Lte parameter tuning

LTE Parameters and TuningCourse Code: LT1001 Duration: 2 days Technical Level: 3

LTE courses include:n LTE/SAE Engineering Overview

n LTE Air Interface

n LTE Radio Access Network

n Cell Planning for LTE Networks

n LTE Evolved Packet Core Network

n 4G Air Interface Technologies

n LTE Technologies, Services and Markets

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LTE PARAMETERS AND TUNING

© Wray Castle Limited

First published 2010Last updated June 2011

WRAY CASTLE LIMITEDBRIDGE MILLS

STRAMONGATE KENDALLA9 4UB UK

Yours to have and to hold but not to copyThe manual you are reading is protected by copyright law. This means that Wray Castle Limited could take you and

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Apart from fair dealing for the purposes of research or private study, as permitted under the Copyright, Designs and Patents Act 1988, this manual may only be reproduced or transmitted in any form or by any means with the prior

permission in writing of Wray Castle Limited.

All of our paper is sourced from FSC (Forest Stewardship Council) approved suppliers.

LTE Parameters and Tuning

ii © Wray Castle Limited LT1001/v2


CONTENTS

iii© Wray Castle LimitedLT1001/v2

Section 1 Introduction

Section 2 Cell Structure, Configuration and Dimensioning

Section 3 Frequency Planning

Section 4 Idle Mode Parameters

Section 5 Connected Mode Parameters

Glossary


iv © Wray Castle Limited LT1001/v2

INTRODUCTION


1.i© Wray Castle LimitedLT1001/v2

SECTION 1


1.ii © Wray Castle Limited LT1001/v2

CONTENTS

Introduction

1.iii© Wray Castle LimitedLT1001/v2

Parameter Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.1

LTE Cell Configuration Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.2

Self-Optimizing Networks (SONs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.3

Self-Configuration and Self-Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.4

Channel Bandwidths and Subcarriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.5

Frequency Bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.6

Bandwidth Applicability in LTE Bands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.7

LTE Air Interface Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.8

System Information Broadcasting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.9

System Information Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.10

LTE Radio Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.11


1.iv © Wray Castle Limited LT1001/v2

At the end of this section you will be able to:

OBJECTIVES

Introduction

1.v© Wray Castle LimitedLT1001/v2

■ identify the functional entities and interfaces that are relevant to air interface parameters

■ suggest key LTE configurations parameters for the eNB

■ outline the procedures for self-configuration

■ outline the aims and process that could form part of a self-optimization process

■ summarize the LTE air interface spectrum band and bandwidth options

■ summarize the LTE air interface protocol stack and identify those protocols most relevant to

radio resource management on the air interface

■ describe the system information broadcasting mechanism used in LTE and relate this to

parameter identification

■ define the key radio measurements for LTE


1.vi © Wray Castle Limited LT1001/v2

LT1001/v2 1.1© Wray Castle Limited

Introduction

Parameter Scope

The architecture for the LTE RAN (Radio Access Network) is IP-based and very simple in terms of functional nodes. Management for all functions that occur within a cell is performed by the eNB, which in effect includes the functions that for 2G and 3G would have been performed by the BSC or RNC. Thus when considering the operation and the parameters for the air interface it is largely independent of the RAN and the core network.

Nevertheless, some functions, particularly for an SFN (Single Frequency Network) configuration, are dependent on communication between eNBs. Therefore the behaviour and functions supported over the X2 interface do have a bearing on air interface operation.

This is not to say that the performance of the air interface is independent of the RAN (Radio Access Network) as a whole or of the core network. The provision of adequate QoS (Quality of Service) on the air interface is only possible with appropriately dimensioned and managed resources for transmission and switching in the network as a whole. The importance of QoS management in this context depends on the type of services offered in the LTE network of interest.

Parameters also determine interactions with neighbour cells for reselection and for

handover

Some procedures require communication between

eNBs over the X2 interface

Key parameters for LTE air interface impact the

relationship between the UE and a serving cell on the eNB

EPC

LT1001/v21.2 © Wray Castle Limited


LTE Cell Configuration Parameters

In addition to the standard cell parameters that are common with any other cellular technology there are a number of LTE-specific parameters that are required for successful LTE system operation.

In the main, these parameters relate to the configuration of the physical layer and the way that control channels are mapped into it. In turn, the settings for these parameters are driven by spectrum availability, the feature set to be used and appropriate dimensioning for expected traffic and signalling loads.

FDD/TDD

Frequency band

Channel bandwidth

Frequency allocation

Cyclic prefix

UL/DL switching point (TDD only)

Control channel configuration

Channel Power offsets

Cell ID

MIMO configuration

Cell Configuration ParameterseNB


Introduction

Self-Optimizing Networks (SONs)

A great deal of emphasis has been placed on a standardized approach to an network that is to some degree self-configuring. This concept is known as SON (Self-Optimizing Network). In general the principle of SON is that performance measurements received in real time from the network can be used to vary configuration parameters in the RAN.

In the past, configuration parameters have been the sole preserve of optimization or network design engineers and most would be set at static or semi-static values. In a SON performance, analysis by an application is used to set, and crucially also to change, key parameters as network conditions change. The overall aim in this automation of the optimization process is to use resources in the most efficient way and at the same time maximize coverage and capacity.

Further Reading: 3GPP TR 36.902, TS 36.300; 22.4

continuously optimized and matched UL and DL coverageoptimized DL and UL capacity of the systembalanced trade-off between coverage and capacityinterference reductioncontrolled cell-edge capacityminimized human intervention in network management and optimization tasksenergy savings

SON Aims

SON functions

SON functions OAM



Self-Configuration and Self-Optimization

The self-configuration process is designed to allow a new eNB to obtain the basic configuration needed for system operation through automatic initialization procedures. The self-configuration process occurs while the eNB is in the ‘pre-operational’ state. In this state the eNB is powered on and has an active communications link, but the RF unit is not yet switched on. Once the eNB has obtained an initial radio configuration the RF unit is powered on and it becomes operational. At this point the self-optimizing process can begin.

The self-optimization process allows the eNB to fine tune radio parameters in response to network activity.

Further Reading: 3GPP TR 36.902, TS 36.300; 22

Basic set-up Configuration of IP address and detection of OAM

Authentication of eNB and network

Association with a S-GW

Downloading of eNB software(and operational parameters)

Self-Configuration(Pre-operational state)

eNB power on(coms link active)

Neighbour list configuration

Coverage/capacity related

Initial radio configuration

parameter configuration

Neighbour list optimization

Coverage and capacity control

Optimization/adaptation

Self-Optimization(Operational state)


Introduction

Channel Bandwidths and Subcarriers

E-UTRA/LTE is designed to work in a variety of bandwidths ranging from 1.4 MHz to 20 MHz. The version of OFDMA (Orthogonal Frequency Division Multiple Access) employed by LTE is similar to the versions employed by WiMAX or DVB, but with a few key differences. In systems such as WiMAX, OFDMA schemes occupying different channel bandwidths employ different subcarrier spacing, meaning that there is a different set of physical layer parameters for each version of the system.

The E-UTRA (Evolved Universal Terrestrial Radio Access) scheme allows for two fixed subcarrier spacing options; 15 kHz in most cases, with an optional 7.5 kHz spacing scheme, only applicable for TDD operation providing broadcast multimedia. Fixing the subcarrier spacing reduces the complexity of a system that can support multiple channel bandwidths.

Further Reading: 3GPP TS 36.211, 36.101:5.5, 36.104:5.5

Channel bandwidths (bandwidth/subcarriers)

1.4 MHz/72

3 MHz/180

5 MHz/300

10 MHz/600

15 MHz/900

20 MHz/1200



Frequency Bands

There is considerable regional variation in the availability of spectrum for LTE operation and this is reflected in the standards. Along with flexibility in bandwidth there is considerable flexibility for spectrum allocation. There are no requirements for minimum band support nor for band combinations. It is assumed that this is determined by regional requirements.

The standards currently identify 19 bands for FDD operation, ranging from frequencies of approximately 700 MHz through to frequencies in the range 2.7 GHz. There are also eight bands identified for TDD operation ranging from approximately 1900 MHz to 2.6 GHz. Considerable scope has been left in the standards to add more frequency bands as global requirements evolve.

Further Reading: 3GPP TS 36.101; 5.5, TS 36.104; 5.5

FDDBand UL Range (MHz) DL Range (MHz)

1 1920 – 1980 2110 – 2170 2 1850 – 1910 1930 – 1990 3 1710 – 1785 1805 – 1880

7 2500 – 2570 2620 – 2690 8 880 – 915 925 – 960

13 777 – 787 746 – 756 ... ... ... 20 832 – 862 791 – 821

24 1626.5 – 1660.5 1525 – 1559

... ... ...

... ... ...

... ... ...

TDDBand UL/DL Range (MHz)

33 1900 – 1920 34 2010 – 2025 35 1850 – 1910 36 1930 – 1990 37 1910 – 1930 38 2570 – 2620 39 1880 – 1920 40 2300 – 2400


Introduction

Bandwidth Applicability in LTE Bands

Not all bandwidths are mandatory in all bands. Those bandwidths that are mandatory for a UE supporting each given band are shown in the table.

Further Reading: 3GPP TS 36.101; 5.6.1

FDDBand

123456789

1011121314... 1718192021

1.4 MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz

... ... ... ... ... ...

TDDBand

3334353637383940

1.4 MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz



LTE Air Interface Protocols The AS (Access Stratum), much of which for UMTS resided in the RNC, is located in the eNB for LTE. In addition, the functionality and complexity of RRC has been significantly reduced relative to that in UMTS. The main RRC functions are outlined in the diagram. The RRC is in overall control of radio resources in each cell and is responsible for collating and managing all relevant information related to the active UEs in its area. In regard of the control of radio resources and procedures that relate to the way radio resources are handled, RRC works very closely with the layer 2 protocol MAC (Medium Access Control). In effect, MAC micro-manages the key procedures in response to overall management of activity by RRC. Each eNB is responsible for managing inter-cell handovers between all the cells it controls. When handover to a cell on another eNB site is required the eNB will pass details of the current UE context to its neighbour. This includes details of identities used, historical measurements taken and active EPS bearers.

Further Reading: 3GPP TS 36.300, 36.331

Data Traffic

NAS NASData Traffic

EMM ECM EMM ECM

UE eNB EPC

NAS

RRCRRC

RRC

System information broadcastingPaging

Connection managementTemporary identity management

Handover managementQoS management

NAS signalling direct transfer

AS (Access Stratum)

PDCP PDCP

RLC RLC

MAC MAC

MAC

Logical to transport channel mappingScheduling

Priority handlingRandom access procedure

RNTI managementHARQ process management

Physical Layer Physical Layer


Introduction

System Information Broadcasting

System information provides the main means of advertising the configuration and parameters applicable in a cell. For LTE the BCH (Broadcast Channel) carries only basic information and acts as a pointer to broader system information related to the NAS (Non-Access Stratum), such as PLMN identity (network code and country code) and AS details such as cell ID and tracking area identity; all of which is carried in the downlink dynamically scheduled resource (DL-SCH). LTE has been designed with network sharing in mind and system information can carry details of up to six sharing PLMNs.

A ‘bootstrap’ approach is adopted for system information broadcasting on the LTE air interface. The physical layer is primarily a dynamically scheduled resource with very little permanently defined capacity. Therefore, although a BCH transport channel and corresponding physical layer resource exist, this is only used to carry the MIB (Master Information Block). The position of the MIB can be determined by the UE as it performs initial synchronization with the cell.

The MIB contains only basic information enabling the UE to find and read the RRC message SystemInformationBlockType1. This message in turn provides the scheduling information for the RRC SystemInformation messages being transmitted on the cell. SystemInformation messages contain one or more information elements, each of which will be a SIB (System Information Block). It is the SIBs that provide the complete set of system information for a UE. The operator determines which SIBs are transmitted, and how frequently, dependent on configurations, capabilities and services supported.

Further Reading: 3GPP TS 36.331; 5.2

MIB

BCCH

BCH

SIB 2-13

DL-SCH

SystemInformation message

Essential and basic frequently

transmitted parameters

All other parameters with flexible scheduling

indicated in SIB 1

MasterInformationBlock(40 ms periodicity)

SystemInformationBlockType1(80 ms periodicity)

SystemInformation (Other SIBs)

eNBSIB 1

IE



System Information Messages

The table provides a summary of the contents of the MIB, SystemInformationType1 message and SIB Types 2–13 currently defined for LTE operation.

Further Reading: 3GPP TS 36.331; 6.2.2, 6.3.1

Type Key Information

MIB DL bandwidth, PHICH configuration, system frame number

SIB scheduling list, PLMN ID(s), TAC, cell barring info,cell selection parameters, frequency band info

Detailed cell barring info, UL frequency allocation, UL bandwidth, MBSFN information

SIB 3 Cell reselection information

SIB 4 Intra-frequency neighbour-cell descriptions

Inter-frequency E-UTRA neighbour-cell descriptions,cell-specific reselection parameters

Inter-RAT UMTS neighbour-cell descriptions,frequency-specific reselection parameters

Inter-RAT GSM/GPRS neighbour-cell descriptions,frequency-specific reselection parameters

Inter-RAT CDMA2000 neighbour-cell descriptions,frequency- and cell-specific reselection parameters

SIB 9 Home eNB name (text)

SIB 10 ETWS (Earthquake and Tsunami Warning System) primary notification

SIB 11 ETWS secondary notification

SIB 12 CMAS (Commercial Mobile Alert Service) notification

SIB 13 MBSFN information

SIB 1

SIB 2

SIB 5

SIB 6

SIB 7

SIB 8


Introduction

LTE Radio Measurements

There are three key measurement values used in LTE, the RSRP (Reference Signal Received Power), the RSSI (Received Signal Strength Indicator) and the RSRQ (Reference Signal Received Quality).

The standards define RSRP as the linear average over the power contributions of the resource elements that carry cell-specific reference signals within the considered measurement frequency bandwidth.

The standards define RSSI as the linear average of the total received power observed only in OFDM symbols containing reference symbols for antenna port 0, in the measurement bandwidth, over N number of resource blocks by the UE from all sources, including serving and non-serving cells, adjacent channel interference, thermal noise, etc.

The standards define RSRQ as the ratio N x RSRP/(E-UTRA carrier RSSI), where N is the number of RBs of the E-UTRA carrier RSSI measurement bandwidth.

Note that the measurement of RSRP is based on reference signals from antenna port 0, but where antenna port 1 can be received reliable, reference signals from that port may also be included. Additionally, the values of RSRP and RSSI used to calculate RSRQ must have the same measurement bandwidth.


(Reference Signal Received Power) (Received Signal Strength Indicator)

Total received power in RS OFDM symbol periods including the serving

cell, all co-channel and adjacent channel interference and thermal noise

Linear average power of the reference signal resource elements

The ratio of the reference signal power, calculated as N x RSRP, to the RSSI, where

N is the number of RBs in the RSSI measurement bandwidth

(Reference Signal Received Quality)

RSRP RSSI

RSRQ

Serving cellServing cell





SECTION 2

CELL STRUCTURE, CONFIGURATION AND DIMENSIONING



CONTENTS

Initial LTE Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1

Radio Channel Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2

Carrier Frequencies and EARFCNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.3

EARFCN Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.4

Assignment of PCI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5

Automatic Neighbour Relation Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.6

Neighbour Additions and Removals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.7

Type 1 Frame Structure (FDD Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8

Type 2 Frame Structure (TDD Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.9

TDD Mode with MBMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.10

Multicast with 7.5 kHz Subcarriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.11

The Benefits of MIMO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.12

MIMO Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.13

MIMO Options for LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.14

Physical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.15

Resource Blocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.16

Downlink Reference Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.17

UE-Specific Reference Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.18

Uplink Demodulation Reference Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.19

Uplink Sounding Reference Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.20

Downlink Configured Control Resource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.21

Downlink Structure with MIMO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.22

Uplink Configured Control Resource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.23

PUCCH Resource Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.24

Cell Structure, Configuration and Dimensioning


CONTENTS

RACH Procedure for MAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.25

Resource Allocation for PRACH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.26

PRACH Resource Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.27

PRACH Procedure Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.28

PRACH Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.29




OBJECTIVES



■ identify the standard radio parameters that need to be defined for an LTE site

■ define the parameters that relate to radio spectrum options for LTE

■ explain how basic parameters such as the PCI (Physical Cell ID) and neighbour relations

can be allocated and managed in a SON (Self Organizing Network)

■ identify the features of the frame structure that need to be defined for LTE cells

■ describe the key control channel structures used for the LTE air interface

■ identify the features of the control channel structures that need to be defined for LTE cells

■ summarize the options for receive diversity, transmit diversity and MIMO capabilities that

can be defined for LTE cells

■ summarize the configuration options for downlink reference signals and uplink demodulation

reference signals

■ explain the parameters that are used to configure and control the PRACH resource and

procedure

■ identify aspects of PRACH control that could be automatically configured and managed in a

SON





Initial LTE Parameters

The frequency allocation will be a very important planned parameter. However, whether there is a frequency plan or not depends on the strategy adopted by the particular licensed operator. Some LTE systems may be operated as SFNs (Single Frequency Networks). In such cases there is no frequency planning to be performed, but the frequency will still need allocating at a cell level.

A PCI (Physical Cell Identifier) must be allocated to each cell. The PCI does need planning to avoid potential ambiguity of cell identity in the built network. This could be done in the normal way as part of the planning process, and all LTE planning tools support this function. However, PCI allocation is also a potential function provided as part of the self-configuration process.

Most planning tools also offer sophisticated mechanisms for both neighbour list creation and analysis. Typically, automatic neighbour cell creation is performed as a starting point and then fine tuned with sanity checking applied manually. Once again, neighbour list allocation can be part of the self-configuration process and additionally may be adjusted as part of a self-optimizing process.

Neighbour List(LTE intra-freq, LTE inter-freq, inter-RAT?)Cell 1: N-cells = (N1, N2, ... Nn)Cell 2: N-cells = (N1, N2, ... Nn)Cell 3: N-cells = (N1, N2, ... Nn)

Physical Cell Identifier(one of 504 in 168 groups of 3)Cell 1: PCI = ?Cell 2: PCI = ?Cell 3: PCI = ?

Frequency AssignmentCell 1: EARFCN = ?Cell 2: EARFCN = ?Cell 3: EARFCN = ?

Cell 1

Cell 2

Cell 3



Radio Channel Organization

For both uplink and downlink operation, subcarriers are bundled together into groups of 12. This grouping is referred to as an RB (Resource Block). The RB also has a dimension in time and when this is combined with the frequency definition it forms the basic unit of resource allocation.

The number of resource blocks available in the system is dependent on channel bandwidth, varying between 100 for 20 MHz bandwidth to just six for 1.4 MHz channel bandwidth. The nominal spectral bandwidth of an RB is 180 kHz for the standard 15 kHz subcarrier spacing. Note that this means there is a difference between the stated channel bandwidth and the transmission bandwidth configuration, which is expressed as n x RB. For example, in a 5 MHz channel bandwidth the transmission bandwidth would be approximately 4.5 MHz. This difference acts as a guard band.

OFDMA channels are allocated within an operator’s licensed spectrum allocation. The centre frequency is identified by an EARFCN (E-UTRA Absolute Radio Frequency Channel Number). The precise location of the EARFCN is an operator decision, but they must be placed on a 100 kHz raster and the transmission bandwidth must not exceed the operator’s licensed spectrum.

Further Reading: 3GPP TS 36.101: 5.6, 5.7; TS 36.104: 5.6, 5.7

Channel bandwidth (MHz)

Transmission bandwidth configuration (n x RB)

Transmission bandwidth (n x RB)

12 subcarriers

EARFCN(100 kHz raster)



Carrier Frequencies and EARFCNs

Formulas are shown in the diagram for translating between the carrier frequency (in MHz) and an EARFCN. Note that separate EARFCNs are required to describe an uplink and a downlink frequency pair in an FDD channel. Note also that there is no defined paring between uplink and downlink EARFCNs in the FDD bands.

EARFCNs in any given band that fall close to the edge of the band such that at the applied bandwidth the channel would extend beyond the edge on the band cannot be used. This implies that the first 7, 15, 25, 50, 75 and 100 EARFCNs at the lower band edge, and the last 6, 14, 24, 49, 74 and 99 EARFCNs at the upper band edge, are not used for bandwidths of 1.4, 3, 5, 10, 15 and 20 MHz respectively.

Further Reading: 3GPP TS 36.101: 5.7.3; TS 36.104: 5.7.3

Carrier Frequency from EARFCN

The frequencies FDL and FUL in MHz are given by:

FDL = FDL_low + 0.1(NDL – NOffs-DL)

and

FUL = FUL_low + 0.1(NUL – NOffs-UL)

where:

NDL and NUL are the downlink and uplink ARFCNs

respectively

FDL_low, FUL_low, NOffs-DL and NOffs-DL are specified

for each LTE band

EARFCN from Carrier Frequency

The EARFCNs NDL and NUL are given by:

NDL = 10(FDL – FDL_low) + NDLOffs-DL

and

NUL = 10(FUL – FUL_low) + NDLOffs-UL

where:

FDL and FUL are the downlink and uplink

carrier frequencies respectively in MHz

FDL_low, FUL_low, NOffs-DL and NOffs-DL are

specified for each LTE band



EARFCN Parameters

EARFCNs in any given band that fall close to the edge of the band such that at the applied bandwidth the channel would extend beyond the edge on the band cannot be used. This means that the first 7, 15, 25, 50, 75 and 100 EARFCNs at the lower band edge, and the last 6, 14, 24, 49, 74 and 99 EARFCNs at the upper band edge, should not be used for bandwidths of 1.4, 3, 5, 10, 15 and 20 MHz respectively.

Note that there is no difference between the downlink and uplink parameter values in the TDD bands.

Further Reading: 3GPP TS 36.101: 5.7.3; TS 36.104: 5.7.3

FDL_low (MHz) NOffs-DL Range of NDL FUL_low [MHz] NOffs-UL Range of NUL

1 2110 0 0 – 599 1920 18000 18000 – 185992 1930 600 600 - 1199 1850 18600 18600 – 191993 1805 1200 1200 – 1949 1710 19200 19200 – 199494 2110 1950 1950 – 2399 1710 19950 19950 – 203995 869 2400 2400 – 2649 824 20400 20400 – 206496 875 2650 2650 – 2749 830 20650 20650 – 207497 2620 2750 2750 – 3449 2500 20750 20750 – 214498 925 3450 3450 – 3799 880 21450 21450 – 217999 1844.9 3800 3800 – 4149 1749.9 21800 21800 – 22149

10 2110 4150 4150 – 4749 1710 22150 22150 – 2274911 1475.9 4750 4750 – 4949 1427.9 22750 22750 – 2294912 728 5000 5000 – 5179 698 23000 23000 – 2317913 746 5180 5180 – 5279 777 23180 23180 – 2327914 758 5280 5280 – 5379 788 23280 23280 – 23379…17 734 5730 5730 – 5849 704 23730 23730 – 2384918 860 5850 5850 – 5999 815 23850 23850 – 2399919 875 6000 6000 – 6149 830 24000 24000 – 2414920 791 6150 6150 - 6449 832 24150 24150 - 2444921 1495.9 6450 6450 – 6599 1447.9 24450 24450 – 24599…33 1900 36000 36000 – 36199 1900 36000 36000 – 3619934 2010 36200 36200 – 36349 2010 36200 36200 – 3634935 1850 36350 36350 – 36949 1850 36350 36350 – 3694936 1930 36950 36950 – 37549 1930 36950 36950 – 3754937 1910 37550 37550 – 37749 1910 37550 37550 – 3774938 2570 37750 37750 – 38249 2570 37750 37750 – 3824939 1880 38250 38250 – 38649 1880 38250 38250 – 3864940 2300 38650 38650 – 39649 2300 38650 38650 – 39649

E-UTRA Operating

Band

Downlink Uplink



Assignment of PCI

Two methods for PCI assignment are identified for LTE, and these are known as ‘centralized’ and ‘distributed’. In the centralized scheme a single predefined value for the PCI is provided from the OAM function to the cell as part of the initial configuration process. This value may be an output of the cell planning process.

For the distributed scheme the OAM function provides a list of PCI values to the cell. The eNB then applies rules to limit the list and ultimately to select a value to be used. For example, the eNB will not use values reported by UEs and it will not use values discovered over the X2 interface for eNB neighbours. The eNB may also be able to receive on a downlink frequency, which would enable it to determine the PCI values already used by neighbours directly, and consequently this information would also be used to limit the list from which the PCI value is selected.


OAMfunction

New cellon eNB

Assigned PCI value Centralized PCI assignment

OAM function

New cell on eNB

PCI value listX2

eNB selects a PCI value from the list using all

available information to avoid collision

Distributed PCI assignment



Automatic Neighbour Relation Function

The aim of the ANR (Automatic Neighbour Relation) function is to maintain optimal neighbour lists for each cell with minimal manual management of the process. At the core of the process is the NRT (Neighbour Relation Table) which contains the list of current intra-frequency, inter-frequency and inter-RAT neighbours for each cell operated by the eNB. Details are provided in the NRT for each neighbour and they include a cell ID as well as the three key parameters ‘No Remove’, No Handover’ and ‘No X2’. If No Remove is checked for a neighbour then that cell cannot be removed through the automatic action of the ANR function. If No Handover is checked then the neighbour is not applicable for handover, but could be a candidate for reselection. If No X2 is checked then handover procedures cannot be performed over the X2 interface.

Neighbour detection and removal functions identify changes to be made in the NRT. Additions are generally detected through measurements from UEs in connected mode and involve interaction with the measurement and reporting functions in RRC. Removals are based on statistical analysis of handover behaviour and success rate. The specific operation of these two functions is not defined and thus implementations are proprietary.

Note that manual adjustment of the neighbour list is still possible through the OAM function.

Further Reading: 3GPP TS 36.300; 22.3.2a

OAM function

NRTmanagement

function

Neighbourremovalfunction

Neighbourdetectionfunction

RRCmeasurement control

and reporting

Internal information

Measurementrequests

Measurementreports

NRremove

NRadd

eNB

NRupdate

NRupdate

NRadd/update

Neighbourrelation table

ANR function

NR CGI No remove No H/O No X2

1 ECGI 1

2 ECGI 2

... ... ... ... ...

n ECGI n



Neighbour Additions and Removals

Initially, the measurement process is started using the existing NRT. RRC indicates the required measurements to the UE using the RRCConnectionReconfiguration message (1). This instruction can be set such that the UE will scan for and report detected cells (2) that are not on a defined n-cell list. Any detected cells are reported in a MeasurementReport message (3). At this stage detected cells will be reported with a signal quality measure and a physical layer identifier (PCI for LTE cells), however there is no reported global cell ID. If the quality measure indicates a cell that could be added to the NRT then the eNB must discover the cell’s global cell ID. In order to do this it modifies the UE’s measurement process and instructs it to read the global cell ID on the detected cell, or cells (4). For inter-frequency and inter-RAT cells this will also require the definition of measurement gaps in order to allow the UE to find and synchronize to the relevant broadcast channels on the target cells. The UE performs these new measurements (5) as defined, and reports the results in a MeasurementReport message (6). If appropriate, the NRT will be modified automatically.


Serving cell

UE inconnected

mode

Inter-frequency neighbour

Inter-RAT neighbour

Inter-frequency neighbour

RRCConnectionReconfiguration12

MeasurementReport (signal quality) 3

RRCConnectionReconfiguration4

5+

6MeasurementReport (Cell ID)



Type 1 Frame Structure (FDD Mode)

There are two basic frame types employed in LTE, which are common to both uplink and downlink. Type 1 frames are employed for FDD full- and half-duplex systems, while Type 2 frames are reserved for TDD operation only. The frame type is implicit when either TDD or FDD mode is set. The Type 1 frame duration is 10 ms and it is divided into 20 slots, each of 0.5 ms duration. More significantly, however, for most information transmission, two slots are combined to form a subframe. Thus subframe duration is 1 ms, which corresponds to the TTI (Transmission Time Interval) for LTE. Type 1 slots contain either 7 or 6 symbols, depending upon which cyclic prefix length is in use. In general, the longer cyclic prefix will be used on cells likely to show more extreme time dispersion. The cyclic prefix length will need to be set for each cell. The longer cyclic prefix provides more tolerance to time dispersion, but it has an impact on capacity. Scheduling occurs across a subframe period. Up to the first three symbols in the first slot of each subframe can be defined as a ‘control region’ carrying control and scheduling messages. The remaining symbols of the first and all symbols in the second slot within the subframe are then available for user traffic.


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190

Frame – 10 ms

Slot – 0.5 ms

0 1 2 3 4 5 6

Subframe – 1 ms

Normal cyclic prefix(c. 5 µs)

0 1 2 3 4 5 6

OFDM SymbolCP

CP

00 1 2 3 4 5 0 1 2 3 4 5

Extended cyclic prefix(c. 17 µs)

OFDM SymbolCP

CP



Type 2 Frame Structure (TDD Mode)

Type 2 frames are used in TDD configured systems. They share the 10 ms frame structure and 1 ms subframe of type 1 frames but an additional demarcation known as a half-frame is also defined. Each half-frame carries five subframes, each of which can be used for the TDD downlink to uplink switching. The switching point in the first half-frame is mandatory, but the second is optional. Thus selection of either half-frame switching or full-frame switching is a configuration parameter.

The diagram also shows the options for allocation of slots for either uplink or downlink use. This is used to adjust the relative uplink/downlink capacity and will also be a configuration parameter.

Further Reading: 3GPP TS 36.211: 4.2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190

Frame – 10 ms

Slot – 0.5 msHalf-frame – 5 ms

2 3 4 5 7 8 90

Subframe DL/UL switch point

(optional)DL/UL switch point

(mandatory)

0 1 2 3 4 5 6

Subframe – 1 ms

0 1 2 3 4 5 6

or

00 1 2 3 4 5 0 1 2 3 4 5

UL/DLConfig.

5 ms (half-frame) switching

0 D U1 D U2 D U6 D U

10 ms (full-frame) switching3 U4 D U5 D U

UL/DL Switching Options

D

DDDD

DD

D

DDD

DD

D

D

DD

DDD

DDD

D

DD

DD

UD

UD

U

U

U

U

U

U

UUUU

UU

U

U



TDD Mode with MBMS

The addition of MBMS brings some added possibilities regarding the configuration of an LTE cell. TDD mode offers the most efficient configuration for unidirectional broadcast services. In TDD mode, particularly with full-frame switching configured, LTE can provide considerable downlink capacity. It should also be noted that an LTE network for broadcast operation is likely to be a shared resource for a number of operators and as such a significant radio bandwidth may be available.

The most efficient way to make use of the available bandwidth is to build an SFN (Single Frequency Network). This is particularly useful for broadcast services, since the same information can be transmitted from all cells in the network simultaneously. In this mode of operation it is likely that the option for 7.5 kHz subcarrier spacing would be used, providing a longer OFDM symbol period and corresponding longer CP (Cyclic Prefix).


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190

Frame – 10 ms

Slot – 0.5 msHalf-frame – 5 ms

2 3 4 5 7 8 90

Subframe DL/UL switch point

(optional)DL/UL switch point

(mandatory)

0 1 2

Subframe – 1 ms

0 1 2

Extended cyclic prefix with 7.5 kHz subcarrier spacing

Extended cyclic prefix(c. 34 µs)

OFDM SymbolCP

CP

UL/DLConfig.

5 ms (half-frame) switching

0 D U1 D U2 D U6 D U

10 ms (full-frame) switching3 U4 D U5 D U

UL/DL Switching Options

D

DDDD

DD

D

DDD

DD

D

D

DD

DDD

DDD

D

DD

DD

UD

UD

U

U

U

U

U

U

UUUU

UU

U

U



Multicast with 7.5 kHz Subcarriers

For broadcast operation the multimedia channel streams can be simulcast from all sites. Thus the UE can receive its required traffic stream from multiple sites simultaneously. This is facilitated in LTE with configuration in TDD mode as an SFN. This could result in large propagation delay differences between channels arriving at a UE from different sites. In most cases use of the extended CP may be sufficient to absorb this time dispersion. However, LTE can be configured with a reduced subcarrier spacing of 7.5 kHz. This results in a doubling of the OFDM symbol period and an accompanying doubling of the extended CP to 34 µs. In this configuration, which is only intended for use in a network used for the MBMS, there are only three symbol periods per slot.

F1F1

F1

SFN frequency plan

Time dispersion in multicast signal (multipath + propagation delay variation)

OFDM symbolCP

OFDM symbolCP

OFDM symbolCP



The Benefits of MIMO

MIMO (Multiple Input Multiple Output) is potentially a complex technology, but it can provide significant benefits in system capability. There are three key ways in which MIMO improves system performance. Any given MIMO implementation may make use of all these benefits or may be configured to take particular advantage of one of them. Ideally, a system should be designed with sufficient flexibility in MIMO implementation to allow a system operator to choose the most suitable implementation for different environments or system goals.

Diversity gain arises out of the provision of multiple antennas at the transmitting and/or receiving end of the radio link. This creates multiple transmission paths with decorrelated fading characteristics. The result is an overall improvement in channel signal-to-noise ratio leading to increased channel throughput and reliability.

Array gain refers to the beamforming capability of a multiple antenna array. With suitable signalling of feedback from the receiver, or with measurements made on a return link, it is possible to direct radiated energy toward the receiver in a steered beam. The result is improved channel performance and increased throughput.

Spatial multiplexing gain arises out of the orthogonality between the multiple transmission path created by the multiple antenna array. Since the receiver can resolve independent transmission paths it is possible to map different information streams into the transmission paths; identifiable by their spatial signature. This results in a direct increase in the channel throughput in proportion to the number of separate transmission streams used.

MIMO brings

Diversity gain Array gain Spatial multiplexing gain

Decorrelates fading through different

transmission paths

Provides a beamforming effect that focuses

radiated energy in the direction of the receiver

Enables multiple data streams to be transmitted

on the same frequency/time resource



MIMO Concept

MIMO antenna arrays offer significant performance improvements over conventional single antenna configurations. The technique involves placing several uncorrelated antennas at both the receiving and transmitting ends of the communication link. If there are four uncorrelated antennas at the transmitter and a further four uncorrelated antennas at the receiver, then there will be 16 possible direct radio paths between the transmitter and the receiver. Each of these is open to multipath effects, creating even more radio paths between the transmitter and the receiver. These radio paths can then be constructively combined, thus producing micro diversity gain at the receiver. Since the receiver can distinguish between the various uncorrelated antennas, it is possible to transmit different data streams in different paths. The stream applied to each antenna can be referred to as a ‘layer’, and the number of antennas available at the transmitter and receiver can be referred to as a ‘rank’. For example, a system operating with a 4x4 MIMO antenna array can be described as having four layers and being of rank four. The way in which data streams are mapped to layers will change the specific benefits offered by a particular MIMO implementation, and the specification of this is an important part of system design. Pre-coding may also be used to improve the MIMO system performance. Pre-coding may be adaptive and as such would be based on some source of channel estimation. This could be derived at the transmission or the reception end of the link.

It is relatively easy to mount antennas on the base station in an uncorrelated manner. For a 2x2 MIMO array, a single cross-polar panel could be used. A 4x4 MIMO array would require two cross-polar panels with suitable special separation. This is harder to achieve in a UE. However, as for the base station, 2x2 MIMO could be achieved with cross polarization, but this could result in some undesirable directivity in the antenna.

Data stream

mapping

Pre-coding matrix

Signal generation

MIMO decoding

and channel estimation

Stream 1

Stream 2

Layer 1

Layer 2

Power weightings and beamforming

Feedback

2x2 MIMO or Rank 2 4x4 MIMO or Rank 4



MIMO Options for LTE

Currently, LTE is specified with several options for SU-MIMO (Single User MIMO) implementation and a more limited option for MU-MIMO (Multi User MIMO) operation. The specifications include descriptions of operation up to 4x4 MIMO.

The simplest option is not MIMO as such, but uses the multi-antenna array at an eNB to provide transmit diversity. The standards allow configuration with up to four antennas at the base station. It is likely that cross-polar antennas would be used as part of the antenna array, so a two-antenna array could be implemented using a single cross-polar panel, with a four-antenna array requiring two cross-polar panels. Transmit diversity involves the transmission of a single data stream to a single UE, but makes use of the spatial diversity offered by the antenna array. This can increase channel throughput or increase cell range.

There are also two beamforming options available: a closed loop mode, which involves feedback of PMI (Pre-coding Matrix Indicators) from the UE, and an open loop mode, which involves the transmission of UE-specific reference signals and the eNB basing the pre-coding for beamforming on uplink measurements.

Full SU-MIMO configurations are available in LTE in the downlink direction up to 4x4. However, a maximum of two data streams is used, even when four antenna ports are available. In SU-MIMO the UE can also be configured to provide feedback indicating the configuration that the UE calculates will give the best performance.

There is only a limited implementation of MU-MIMO specified. It is applicable in the uplink direction and allows two UEs to use the same time-frequency resource within one cell.

Further Reading: 3GPP TS 36.211; 6.3.3, 6.3.4, TS 36.213; 7.1

Transmit Diversity BeamformingClosed loop with feedback

SU-MIMO MU-MIMO (virtual MIMO)



Physical Channels

The physical layer involves the transmission and reception of a series of physical channels and physical signals. The physical signals relate to the transmission of reference signals, the PSS (Primary Synchronization Signal) and the SSS (Secondary Synchronization Signal).

The PBCH (Physical Broadcast Channel) carries the periodic downlink broadcast of the RRC MasterInformationBlock message. Note that system information from BCCH is scheduled for transmission in the PDSCH (Physical Downlink Shared Channel).

The PDCCH (Physical Downlink Control Channel) carries no higher-layer information and is used for scheduling uplink and downlink resources. Scheduling decisions, however, are the responsibility of the MAC layer, therefore the scheduling information carried in the PDCCH is provided by MAC. Similarly the PUCCH (Physical Uplink Control Channel) is used to carry resource requests from UEs that will need to be processed by MAC.

The PHICH (Physical Hybrid ARQ Indicator Channel) is used for downlink ACK/NACK of uplink transmissions from UEs in the PUSCH. It is a shared channel and uses a form of code multiplexing to provide multiple ACK/NACK responses.

The PCFICH (Physical Control Format Indicator Channel) is used to indicate how much resource in a subframe is reserved for the downlink control channels. It may be either one, two or three of the first symbols in the first slot in the subframe.

The PRACH (Physical Random Access Channel) is used for the uplink transmission of preambles as part of the random access procedure.

The PDSCH (Physical Downlink Shared Channel) and the PUSCH (Physical Uplink Shared Channel) are the main scheduled resource on the cell. They are used for the transport of all higher-layer information including RRC signalling, service-related signalling and user traffic. The only exception is the system information in PBCH.

Further Reading: 3GPP TS 36.213, TS 36.211, TS 36.300

Physical signalsPSS/SSS

Reference Signals

Physical layer

MACBCCH PCCH CCCH DCCH DTCH

BCH PCH RACH DL-SCH UL-SCH

PBCH PDCCH PHICH PCFICH PRACHPUCCH PDSCH PUSCH

MAC Control



Resource Blocks

A resource block consists of 12 subcarriers for one slot period. In both the uplink and downlink directions, 12 subcarriers correspond to 180 kHz of bandwidth. The minimum possible capacity allocation period is the Transmission Time Interval (TTI) of 1 ms. This equates to the allocation of two consecutive resource blocks. Additionally, the sum of all the resource blocks in a single slot period is known as the resource grid. The minimum definable capacity unit is the resource element, which is one subcarrier during one symbol period. Within each resource grid the resource elements that will be carrying reference signals are assigned first; the remaining elements are then available to have user data or control mapped to them. In data transfer terms, one resource element is the equivalent of one modulation symbol on a subcarrier, so if QPSK modulation was being employed, one resource element would be equal to 2 bits, with 16QAM 4 bits and with 64QAM 6 bits of transferred data. If MIMO is employed on the downlink then separate resource grids are created for each antenna port – each port maps to a different MIMO stream.


Subcarrier 1

Subcarrier 12

Resource block

1 ms subframe (2 slots)

Resource element

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6



Downlink Reference Signals

In any mobile radio system it is necessary to provide mobile devices with a means of measuring and monitoring the strength and quality of the signal they receive and of calibrating their own output to ensure that the correct frequencies are being employed. LTE employs a physical reference signal, embedded in the main body of the transmitted signal to provide an opportunity for channel estimation and frequency calibration on the downlink. On the downlink, three types of downlink reference signals are currently defined: cell-specific reference signals, MBSFN (Multicast/Broadcast Single Frequency Network) reference signals, associated with MBSFN transmission, and UE-specific reference signals. In most circumstances only the first of these reference signal types will be used. The reference signal takes the form of a modulated time and frequency shifted symbols generated from a Gold code of length 231–1.

Reference signal symbols are inserted into the transmitted resource grid following a predetermined sequence as shown in the diagram for cell-specific SISO (Single Input Single Output) and 2x2 MIMO (Multiple Input Multiple Output) antenna arrangements and the normal CP. Modifications of this pattern are also defined for 4x4 MIMO operation, for use of the extended CP and for MBSFN operation. Cell-specific reference signals, as well as providing a ‘known signal’ upon which to base channel estimations, are modulated to identify the cell to which they belong. The sequence is related to the cell’s PCI in the set of 504 options.

Reference signals may have an applied power-boost over data symbols of up to 6 dB.

Further Reading: 3GPP TS 36.211; 6.10, TS 36.300

0 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2R0 5 6 1 2 5 6

R0

R0

R0

R0

R0

R0

R0

3 33 33 33 33 33 33 33 33 33 33 3

3 3

0

0

4

4

0

0

4

4

SISO (Normal CP)

Cell-specific downlink reference signals

2x2 MIMO (Normal CP)

Antennaport 0

Antennaport 1

0 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2R0 5 6 1 2 5 6

R0

R0

R0

R0

R0

R0

R0

3 33 33 33 33 33 33 33 33 33 33 3

3 3

0 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 6

3 33 33 33 33 33 33 33 33 33 33 3

3 3R1

R1

R1

R1

R1

R1

R1

R1



UE-Specific Reference Signals

UE-specific reference signals are in addition to, and not in place of, cell-specific reference signals. They are intended for use when the cell supports beamforming antennas for individual UEs. The UE-specific reference signals are only transmitted in PRBs that are scheduled to be received by the UE in question.

When beamforming is used the channel characteristic in the beam will be different than that for general cell coverage. Additionally, the cell may be based on a MIMO transmission while only SISO is used for UE specific reference signals. Thus the UE-specific reference signals are required for accurate channel modelling and CQI feedback for a UE with an allocated beam.

The diagram shows the arrangement for UE-specific reference symbols in the resource grid for cell SISO operation and the normal CP. A second pattern is defined for the extended CP. UE-Specific reference signals are considered to be on port 5, ports 0 to 3 being for normal cell operation up to 4x4 MIMO and port 4 being for MBSFN operation.

Further Reading: 3GPP TS 36.211; 6.10, TS 36.300

0 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 0 1 2 4 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 1 2 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 0 1 2 4 60 1 2 4 5 6 0 1 2 4 5 6

1 2R0 5 6 1 5 6

R0

R0

R0

R0

R0

R0

R0

3 33 33 3

33 33 33 3

33 33 33 3

3

0

0

4

4

0

0

4

4

R5 R5

R5 R5

R5 R5

R5 R5

R5 R5

R5 R5

SISO (Normal CP)

Antennaport 5

UE-specific downlink reference signals

Beamforming antenna for specific UE on

antenna port 5

Main cell coverage: SISO – Antenna port 0 2x2 MIMO – Antenna ports 0 and 1 4x4 MIMO Antenna ports 0,1,2 and 3 MBMS – Antenna port 4



Uplink Demodulation Reference Signals

There are two types of reference signal used in the uplink, known as DRS (Demodulation Reference Signals) and SRS (Sounding Reference Signals). DRS symbols are multiplexed with user data and control transmissions. DRSs provide the receiving eNB with a ‘known signal’ element upon which to perform channel estimations and from which it can calculate timing adjustments. For the PUSCH one DRS symbol is transmitted per slot in the fourth symbol position (symbol number three). In the PUCCH there may be either two or three DRS symbols per slot dependent on configuration (not shown).

Because DRS symbols are multiplexed with user data they will always occupy the same allocated bandwidth as the user data. This means that the length of the reference symbol sequence needs to be the same as the number of allocated subcarriers in the transmission bandwidth (and always a multiple of 12). For each possible bandwidth allocation a number of base DRS sequences are defined. This is organized such that there are 30 base sequences for 1, 2 and 3 resource block allocations and more than 30, dependent on specific bandwidth, for allocations of more than three resource blocks. Thus there are multiple DRS sequences in many different lengths. They are organized into 30 ‘sequence groups’. Each sequence group contains one base DRS sequence of each length up to that suitable for bandwidth allocations up to five resource blocks, and two base DRS sequences for bandwidth allocations above five resource blocks.

Each cell is allocated one sequence group. In addition, multiple orthogonal DRS sequences are then created from a single base sequence using cyclic shifts; 12 are available for each base sequence. These orthogonal sequences are used to multiplex signals from different UEs in the same cell.


0 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 60 1 2 DRS 4 5 6




Uplink Sounding Reference Signals

Channel estimations for received uplink signals are made by the eNB based on measurements taken of the reference signal symbols embedded in uplink transmissions. If there is no uplink transmission taking place, however, the eNB cannot take measurements. In these circumstances a UE may be instructed to perform uplink sounding, which consists of the UE transmitting a reference signal within an uplink resource allocation specifically set aside for the purpose. Sounding is performed on the transmission of SRS signals. Resources for SRS are allocated over multiples of four resource blocks and always transmitted in the last symbol of a subframe. SRS transmissions can be set as periodic, can be frequency hopping and can have variable bandwidth; the configuration being set using higher-layer signalling. UEs may also be instructed to undertake sounding to enable the eNB to perform ‘frequency-specific scheduling’. This term describes a procedure whereby the eNB measures the sounding signal transmitted by a UE across some or all subcarriers and then chooses the resource block that contains the best performing set of frequencies. This is similar to the downlink process whereby scheduling can be influenced by the UE’s CQI (Channel Quality Indication) reporting.


0 1 2 DRS 4 5 SRS

0 1 2 DRS 4 5 60 1 2 DRS 4 50 1 2 DRS 4 5 60 1 2 DRS 4 50 1 2 DRS 4 5 60 1 2 DRS 4 50 1 2 DRS 4 5 60 1 2 DRS 4 50 1 2 DRS 4 5 60 1 2 DRS 4 50 1 2 DRS 4 5 6


SRS

SRS

SRS

SRS

SRS



Downlink Configured Control Resource

The diagram shows an example of a populated downlink FDD frame using the normal CP and implemented in a 5 MHz bandwidth channel.

The PBCH is transmitted during subframe 0 of each 10 ms frame and occupies the centremost six resource blocks. Alongside this, and also in the sixth subframe in the frame, are the primary and secondary synchronization signals. Reference signal positions for two resource blocks within a single subframe are shown. All these resource allocations are fixed and therefore need no special attention . However, the PSS and SSS are related to the cell’s physical layer ID, which is configured. Additionally, it is possible that power offsets could be included for these channels.

The diagram also shows the space allocated for downlink control channels, which includes PDCCH, PCFICH and PHICH resources. A UE will be required to monitor some proportion of this dependent on the connectivity state and the cell configuration. Crucially, this is a variable resource that may occupy one, two or three symbol periods at the start of each subframe. The setting will affect available capacity and therefore it will be a parameter that needs setting or may be dynamically variable in a SON implementation.

The remainder of the allocation space will be used for scheduled downlink transmission in the PDSCH. This includes common control signalling (system information and paging), dedicated control signalling and traffic packets.

Further Reading: 3GPP TS 36.211, TS 36.300

FrameSubframeSlot

0 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2R0 5 6 1 2 5 6

R0

R0

R0

R0

R0

R0

R0

3 33 33 33 33 33 33 33 33 33 33 33 3

0 0

4 4

0 0

4 4

Downlink control channels configured for one, two or three

slots(PDCCH + PHICH + PCFICH)

PSS/SSS Primary and Secondary Synchronization Signals

PBCH Physical Broadcast Control Channel

PDSCH Physical Downlink Shared Channel



Downlink Structure with MIMO

The diagram shows an example of a downlink FDD frame using the normal CP with 2x2 MIMO configured. Again it is based on a 5 MHz bandwidth channel.

Reference signal positions for two resource blocks within a single subframe are shown for both antenna ports in the 2x2 MIMO system. Note that control allocation on the second antenna port is the same as that on the first port. This means that for MIMO implementations parameter setting is little different than for non-MIMO configurations. However, LTE does offer a number of different MIMO configurations and the selected configuration will need to be set.


0 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 6

R1

R1

R1

R1

3 33 33 33 33 33 33 33 33 33 33 33 3

Antenna port 1 Antenna port 1R1

R1

R1

R1

FrameSubframeSlot

0 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2 5 6 1 2 5 60 1 2 4 5 6 0 1 2 4 5 60 1 2 4 5 6 0 1 2 4 5 6

1 2R0 5 6 1 2 5 6

R0

R0

R0

R0

R0

R0

R0

3 33 33 33 33 33 33 33 33 33 33 33 3

Antenna port 0

Antenna port 0



Uplink Configured Control Resource

The diagram shows an example of a populated uplink FDD frame using the normal CP and implemented in a 5 MHz bandwidth channel. The overall uplink frame structure is simpler than that employed by the downlink. Symbol 3 in each slot carries the uplink demodulation reference signal, leaving the other six symbols available to carry traffic. A configurable number of outer resource blocks can be set aside to carry PUCCH messages. The number of resource blocks used for PUCCH in this way will therefore need to be set in the cell configuration or will be dynamically variable in a SON implementation.


Frame

SubframeSlot

0 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 60 1 2 DRS 4 5 6 0 1 2 DRS 4 5 6

Configured for one, two or three RBs at the edges of the channel

PUSCH Physical Uplink Shared Channel

PUCCH Physical Uplink Control Channel



PUCCH Resource Allocation

The PUCCH is allocated to the outermost RBs in the allocated bandwidth. The amount of resource allocated for use to carry PUCCH is indicated to UEs with the parameter N(2)RB. This parameter indicates the number of RBs used for PUCCH per slot and forms part of the PUCCH-Config information element, itself found in several RRC messages.

Common configuration for PUCCH resources is carried in SIB Type 2. Dedicated PUCCH configuration is provided in the RRCConnectionSetup, RRCConnectionReconfiguration and RRCConnectionRe-establishment messages.

PUCCH information is transmitted by a UE using a PUCCH region, which occupies one subframe and utilizes RBs on alternate sides of the channel in alternate slots. This approach provides maximum frequency diversity in the PUCCH. Note that since one PUCCH region equals two PUCCH slots, the parameter N(2)RB also describes the number of PUCCH regions per subframe.

The diagram shows an example based on N(2)RB equal to four. Note that uneven values may also be used, in which case one RB will always be available for scheduled PUSCH use on alternating sides of the channel.

A single PUCCH region can be sub-multiplexed using code sequences between up to to 12 different UEs.

Further Reading: 3GPP TS 36.211; 5.3, 5.4, TS 36.213; 10.1

PUCCH_1 PUCCH_0 PUCCH_1 PUCCH_0




SubframeSlot

PUCCH region 0

PUCCH region 1

PUCCH region 2

PUCCH region 3

PUSCH demodulation reference signals

Example, N(2)RB = 4



RACH Procedure for MAC

The random access procedure is handled by the MAC and the physical layer and operates using a combination of the PRACH on the uplink and the PDCCH on the downlink. UEs are informed of the range of random access preambles available in system information, as are the contention management parameters. When a random access event is required, the UE will perform the following functions: review and randomly select a preamble

■ check the BCCH for the current PRACH configuration; this will indicate the location and periodicity of PRACH resources in uplink subframes

■ calculate open loop power control parameters – initial transmit power, maximum transmit power and power step

■ discover contention management parameters Once the UE transmits an initial preamble it will wait a specified period of time for a response before backing off and retrying. Open loop power control ensures that each successive retry will be at a higher power level. Upon receipt of a successful uplink PRACH preamble, the eNB will calculate power adjustment and timing advance parameters for the UE based on the strength and delay of the received signal and schedule an uplink capacity grant to enable the UE to send further details of its request. This will take the form of the initial layer 3 message. If necessary, the eNB will also assign a Temporary C-RNTI (Cell Radio Network Temporary Identifier) for the UE to use for ongoing communication.

Once received, the eNB reflects the initial layer 3 message back to the UE in a subsequent downlink scheduled resource to enable unambiguous contention resolution. After this, further resource allocations may be required for signalling or traffic exchange; these will be addressed to the C-RNTI.

Further Reading: 3GPP TS 36.321; 5.1, TS 36.213; 6

MAC Entity

MAC Entity

Physical layer

Physical layer

RACH and preamble instructions

L2/L3 Message

CCCH

Radio link

PRACH RACH indication

RAR (Random Access Response)

DL-SCH

•Timing Advance•UL Grant•Temporary C-RNTI

RARDL-SCH/PDSCH

Resource allocation for RARPDCCH

CRC scrambledwith RA-RNTI

MAC PDU [L2/L3 Message]UL-SCH/PUSCH

CRI (Contention Resolution Identity)

DL-SCH

L2/L3 Message

CCCH

Resource allocation for CRIPDCCH

CRIDL-SCH/PDSCH

Contention check.Temporary C-RNTIbecomes the allocated C-RNTI



Resource Allocation for PRACH

There is considerable flexibility in the options for resources to be used for random access. A random access preamble sequence burst takes place in an allocated PRACH timeslot. This special timeslot period corresponds to one, two or three subframe periods depending on the preamble format used, which may be set as types 0, 1, 2 or 3 as shown in the diagram. The relative variations in the lengths of the CP, preamble sequence and GT (Guard Time) between the preamble formats is intended to cater for a wide variety of coverage scenarios.

PRACH timeslots are allocated with a regular repetition period known as the PRACH burst period. This ranges from fractions of a frame to multiples of a frame. The example in the diagram corresponds to a 10 ms period, which would be typical with a 5 MHz bandwidth. The example also assumes that Format 0 preambles are in use. More than one PRACH timeslot can be allocated at the same time but this would increase the processing load for the eNB. It should also be noted that the possibility for an eNB to schedule PUSCH resources at the same time and frequency as a PRACH timeslot is not precluded.


Frame

Subframe 1 ms (30720 Ts)

CPPreamble(24576 Ts) GT

3168 Ts 2976 Ts

Format 0

Format 1

Format 2

Format 3

(21024 Ts) (24576 Ts) (15840 Ts)

(6240 Ts) (49152 Ts) (6048 Ts)

(21024 Ts) (49152 Ts) (21984 Ts)

CP Preamble GT

CP Preamble GT

CP Preamble GT



PRACH Resource Description

The key parameters that define the PRACH resource in the uplink are contained within SIB Type 2. They form part of the information element RadioResourceConfigSIB. The preamble sequences are drawn from a set of Zadoff-Chu sequences such that 64 sequences can be available on a cell.

For normal LTE operation there are four preamble sequence formats. The format to be used on the cell is indicated to UEs with an index that references a table in the standards documentation. The reference in the table will also indicate which subframes may be used for the start of a preamble transmission. The minimum configuration for this allows just one starting point that is only available in even-numbered frames. The maximum configuration provides five starting positions in every frame. In addition, a parameter is included that indicates the starting index in terms of frequency allocation for PRACH. This is simply the lowest RB index that can be used. The allocation will always be for six RBs in the frequency domain.

Note that this allocation of resource does not have to be for exclusive use by PRACH. It may also be allocated for a UE using the UL-SCH.

Further Reading: 3GPP TS 36.331; 6.3.1, TS 36.321; 5.7.1

Frame

Define the set of preamble sequences that can be used

Index references a position within a table that defines the preamble format to be used and also the starting subframes within the frame

Format TSEQ

0 3168. Ts 24576. Ts c. 0.9 TTI

1 21024. Ts 24576. Ts c. 1.5 TTI

2 6240. Ts c. 1.8 TTI

3 21024. Ts 2 x 24576. Ts c. 2.3 TTI

CP Sequence

TSEQ

Defines the starting RB position to be used in the frequency domain

SIB Type 2

RadioResourceConfigSIB

prach-ConfigrootSequenceIndex 0...837

prach-ConfigInfo

prach_ConfigIndex 0...63

High-speed-flag 1/0

zeroCorrelationZoneConfig 0...15

prach_FreqOffset 0...94

TCP

TCP

Example:Preamble format 3

prach_ConfigIndex = 54

prach_FreqOffset = 5

RB 5

SF 1 SF 6

2 x 24576. Ts



PRACH Procedure Control

The RadioResourceConfigSIB information element also contains the parameters that control the overall preamble transmission process. Having identified the set of preamble sequences available on a cell, the UE must select one to use. Optionally, the set of preamble sequences available on a cell can be divided into two groups, A and B. Use of group B is determined by two thresholds; one relates to the size of the layer 3 message that will be transmitted after a response has been received, and the other relates to the required power offset between the power used for the successful preamble and the power used for the layer 3 message transmission. If both these thresholds are met then the UE will select a sequence from group B, otherwise it will use a sequence from group A .

The UE then selects a starting frame and an RB from the set defined as available for PRACH and begins a transmission sequence that is controlled by the four key parameters shown in this information element.

Further Reading: 3GPP TS 36.331; 6.3.1, TS 36.213; 6.1

SIB Type 2

RadioResourceConfigSIB

rach-Config

preambleInfo

numberOfRA-Preambles 4, 8, ...64 steps of 4

preambleGroupAConfig

sizeOfRAPreambleGroupA 4, 8, ...60 steps of 4

messageSizeGroupA 56, 144, 208, 256

messagePowerOffsetGroupB

powerRampingParameters

powerRampingStep 0, 2, 4, 6 dB steps of 2

preambleInitialReceivedTargetPower

ra-SupervisionInfo

preambleTransMax 3, 4, 5, 6, 7, 8, 10, 20, 50, 100, 200

ra-responseWindowSize 2, 3, 4, 5, 6, 7, 8, 10 subframes

mac-ContentionresolutionTimer 8, 16, ...64 steps of 8 subframes

macHARQ-Msg3Tx 1, 2, ...8

Used to select the specific preamble for the transmission

Used to control the physical layer preamble transmission procedure

Used to control behaviour with respect to the subsequent transmission of the Layer 3 message

–inf, 0, 5, 8, 10, 12, 15, 18 dB

–120,–118, ...–90 dBm steps of 2



PRACH Procedure

The UE calculates an initial power, as shown in the diagram, and uses this for the first preamble sequence transmission.

Starting from the last subframe in which the preamble sequence was transmitted, the UE will begin to monitor the PDCCH for a RAR (Random Access Response). The RAR will be identified with an RA-RNTI that is related to the preamble transmission, as shown. The UE continues to monitor the PDCCH for a number of subframes given by the parameter ra-responseWindowSize. If it has not received a RAR in this time with a corresponding RA-RNTI then it will initiate a retransmission with a power increment, as shown. This process continues until the number of retransmissions reaches preambleTransMax. If this occurs then the procedure will fail and an indication will be given to higher layers.


PPRACH = min{PCMAX, PREAMBLE_RECEIVED_TARGET_POWER + PL} dBm

where:

PL = Path loss estimated by the UE

PCMAX = Max power allowed or power class of the UE

PREAMBLE_RECEIVED_TARGET_POWER = preambleInitialReceivedTargetPower +

DELTA_PREAMBLE + (PREAMBLE_TRANSMISSION_COUNTER – 1)*powerRampingStep

where:

DELTA_PREAMBLE = 0 dB for formats 0 and 1, –3 dB for formats 2 and 3

powerRampingStep

ra-responseWindowSize

powerRampingStep

Look for RARin DPCCH

preambleTransMax

Look for RARin DPCCH

in DPCCH

RA-RNTI= 1 + t_id + 10*f_idwhere:t_id = the index of the first subframe usedf_id = the index of the RB used

Look for RARPPRACH



FREQUENCY PLANNING



SECTION 3



CONTENTS

Frequency Planning


Spectrum Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.1

Example – PCS1900 Operator LTE Spectrum Refarming . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.2

Example – US Operator with 700 MHz New Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3

Example – IMT-2000 Operator LTE Spectrum Refarming . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.4

Example – GSM900/1800 Operator LTE Spectrum Refarming . . . . . . . . . . . . . . . . . . . . . . . . .3.5

Example – European LTE New Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.6

Considerations for an SFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.7

Partial Frequency Reuse in an SFN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.8

Limitations of Partial Frequency Reuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.9

Multi-Frequency Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.10

Example Frequency Plan with Three Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.11

Example Frequency Plan with Six Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.12

SINR for a Three-Frequency Planned Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.13

SINR for a Six-Frequency Planned Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.14

SINR for an SFN Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.15

Downlink Throughput for a Three-Frequency Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.16

Downlink Throughput for a Six-Frequency Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.17

Downlink Throughput for an SFN (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.18

Downlink Throughput for an SFN (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.19

Histograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.20

Downlink Throughput for Fixed Users in a 3FN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.21

Downlink Throughput for Fixed Users in an SFN (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.22

Downlink Throughput for Fixed Users in an SFN (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.23

Downlink Throughput for MIMO Users in a 3FN (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.24

Downlink Throughput for MIMO Users in a 3FN (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.25

Downlink Throughput for MIMO Users in an SFN (1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.26

Downlink Throughput for MIMO Users in an SFN (2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.27




OBJECTIVES

Frequency Planning


■ identify factors that are affected by the frequency allocation strategy for LTE cells

■ describe potential refarming options for existing GSM, UMTS and CDMA2000 spectrum

■ describe potential licence options for LTE operation in new spectrum

■ characterize network LTE network behaviour for single- and multi-frequency allocation

strategies

■ discuss the appropriateness of single- and multi-frequency allocation strategies for different

LTE network scenarios

■ interpret example planning tool studies of network performance for a range of frequency

allocation and frequency planning scenarios




Frequency Planning

Spectrum Considerations

Unlike the 2G and 3G technologies that have preceded it, where spectrum usage is fairly constrained, for LTE there are many options for spectrum bands and spectrum division within a band that an operator may have access to. The specific spectrum availability will depend on the country and region in which the network will operate. Spectrum options will also be impacted by legacy technology choices. For example, an operator may already have licensed spectrum available in which LTE could be rolled out. This may because an older legacy technology can be progressively switched off, or because they have spectrum that is currently unused.

In most cases however, an operator will need to consider purchasing new spectrum in which to operate LTE. Even when new spectrum is available, an operator will need to consider a number of operation options. For example, the spectrum block will be either FDD or TDD, there may be a number of bandwidth options, they may want to provide for a mixture of fixed and mobile access and there may be specific interference issues to think about resulting from other technologies in use or from geographical factors.

?

Which frequency band?

How muchspectrum?

Build a single-frequencyor mult-frequency

network?

What kind of services are required?

Mobile?Fixed?

Broadband access?Broadcast?

What coverage is needed?

Urban?Rural?Both?

Refarm existingspectrum?

Unused spectrum already available?

FDD or TDD?

Compatibility with legacyspectrum/technologies?

Consideration forcompatibility for

roaming?



Example – PCS1900 Operator LTE Spectrum Refarming

The diagram shows some of the options open to an operator with one of the A,B or C blocks of PCS1900 spectrum. This spectrum is used for both CDMA2000 operation and GSM/UMTS operation. Different operators will demarcate their spectrum in different ways but some possibilities are shown here.

A CDMA2000 operator could fairly comfortably refarm a 5 MHz frequency block to be made available for LTE. This would leave them with enough spectrum to continue operation of eight CDMA2000 radio carriers, probably used with a mixture of 1x and 1xEV-DO configurations. The 5 MHz of LTE spectrum could be used in a number of ways. For example the operator could build an SFN based on a 5 MHz bandwidth channel. Alternatively, the operator could chose to implement the spectrum as a three-frequency network based on 1.4 MHz channel bandwidth.

Another theoretical possibility is for the LTE frequency block to be utilized as two 5 MHz TDD channels, one in the reverse spectrum and one in the forward spectrum. However, this would probably result in unacceptable inter-technology or inter-operator interference, and in any case, would most likely be a breach of the licence conditions and is not specified in the LTE standards.

If a GSM operator were to refarm 5 MHz for LTE operation they would be left with sufficient spectrum to operate 50 GSM radio carriers, which could offer a mixture of GSM and GPRS/EDGE connectivity. They would have the same options for LTE spectrum division. If, however, the operator has already refarmed spectrum for UMTS operation, which would demand at least one 5 MHz block, then the amount of spectrum remaining for GSM operation would be sufficient for only 25 radio carriers. It is doubtful whether this amount of spectrum would be viable.

In both cases, as time passes more spectrum can be refarmed for legacy 2G and 3G for LTE operation.

A(15 MHz)

D(5 MHz)

B(15 MHz)

E(5 MHz)

F(5 MHz)

C(15 MHz)

Reverse Forward

1850 1910 1930 1990Frequency MHz (E-UTRA Band 2)

GSM/GPRS/EDGE(5 MHz)

UMTS/HSPA(5 MHz)

LTE(5 MHz)

GSM/GPRS/EDGE(10 MHz)

LTE(5 MHz)

CDMA2000 1x/1xEV-DO(10 MHz)

LTE(5 MHz)

8 CDMA radio carriers

1 x 5 MHz (FDD)3 x 1.4 MHz (FDD)1 x 1.4 MHz plus 1 x 3 MHz (FDD)

50 GSM radio carriersGSM/UMTS

(5 MHz)LTE

(10 MHz)

CDMA2000 1x/1xEV-DO

LTE(10 MHz)

4 CDMA radio carriers

1 x 10 MHz (FDD)2 x 5 MHz (FDD)3 x 3 MHz (FDD)3 x 1.4 MHz plus 1 x 5 MHz (FDD)

25 GSM radiocarriers(viable?)

1 UMTS radiocarrier

1 UMTS radio carrier

25 GSM radiocarriers(viable?)


Frequency Planning

Example – US Operator with 700 MHz New Spectrum

Following TV digital switchover in the US the FCC (Federal Communication Commission) has made a number of licences available in the 700 MHz band for use as broadband digital access. The diagram shows an example of use based on an operator with a licence to use the ‘C’ block of the Upper 700 MHz band.

As can be seen the C-block licence corresponds approximately with LTE Band 13. Thus the operator has the potential to use 10 MHz for LTE FDD operation. The bandwidth agnostic nature of LTE means that the operator has a number of frequency division and reuse options to consider. However, the chief advantage is the relatively low frequency, which significantly improves the achievable coverage from a single site. This means the operator can take advantage of substantial infrastructure savings and at the same time provide more reliable coverage, particularly in terms of in-building coverage.


Former analogueTV channels

C(11 MHz)

D Public safety C(11 MHz)

D Public safety

A B E A BDivisionsfor FCCAuction 73

10 MHz(DL)

10 MHz(UL)

Ch. 52

Ch. 53

Ch. 54

Ch. 55

Ch. 56

Ch. 57

Ch. 58

Ch. 59

Ch. 60

Ch. 61

Ch. 62

Ch. 63

Ch. 64

Ch. 65

Ch. 66

Ch. 67

Ch. 68

Ch. 69

LTE Band 13

Lower 700 MHz Band

(698 MHz-746 MHz)

Upper 700 MHz Band

(746 MHz-806 MHz)



Example – IMT-2000 Operator LTE Spectrum Refarming

The diagram shows some of the options open to an operator with a typical licence for European operation of UMTS in the IMT-2000 spectrum corresponding to LTE band 1. Such an operator could refarm a 5 MHz frequency block to be made available for LTE. This would leave them with enough spectrum to continue operation of two UMTS FDD radio carrier pairs (including HSPA capability). The 5 MHz of LTE spectrum could be used in a number of ways. For example the operator could build an SFN based on a 5 MHz bandwidth channel. Alternatively, the operator could choose to implement the spectrum as a three-frequency network based on 1.4 MHz channel bandwidth.

There are many cases where European operators already hold licences for 5 MHz of TDD spectrum but are not currently making use of it. For operators in this position this spectrum could be made available immediately for LTE TDD operation. The only restriction may be limitation in the original licence conditions.

Another important consideration is that most European UMTS operators will also have some GSM900 and/or GSM1800 spectrum. Again, dependent on licence conditions, it may make more sense to try and refarm GSM spectrum for LTE operation rather than UMTS spectrum.

TDD FDD SAT TDD FDD SAT

TDD FDD FDD

IMT-2000Spectrum

TypicalEuropeanallocation

5 MHz 15 MHz

DECT

TypicalEuropeanlicence

UMTS(10 MHz)

LTE(5 MHz)

1885 1920 1980 2010 2025 2110 2170 2200

1900

UMTS(5 MHz)

LTE(10 MHz)

1 x 5 MHz (TDD)3 x 1.4 MHz (TDD)1 x 1.4 MHz plus 1 x 3 MHz (TDD)

1 x 5 MHz (FDD)3 x 1.4 MHz (FDD)1 x 1.4 MHz plus 1 x 3 MHz (FDD)

2 UMTS radio carriers

15MHz

LTE(5 MHz)


1 UMTS radio carrier


Frequency Planning

Example – GSM900/1800 Operator LTE Spectrum Refarming

There are two chief advantages in a operator with both GSM and UMTS spectrum choosing to refarm GSM spectrum before they refarm UMTS spectrum. The first is that upgrading UMTS HSPA to HSPA+ provides an economic way of achieving very similar performance to LTE, at least in the more restricted bandwidths. Thus it may be difficult to make a business case for replacing UMTS with LTE in the short term. Secondly, the lower frequencies in the GSM spectrum, particularly GSM900, mean that LTE implemented in these bands would require less capital expenditure and could provide more reliable coverage.

Licences for GSM900/1800 vary very widely, but the diagram provides examples of some possibilities. These blocks of spectrum are completely covered by LTE bands eight and three.

E-GSM(10 MHz)

P-GSM(25 MHz)

E-GSM(10 MHz)

P-GSM(25 MHz)

E-GSM(5 MHz)

P-GSM(12.5 MHz)

LTE(5 MHz)

P-GSM(12.5 MHz)

E-GSM(5 MHz)

P-GSM(2.5 MHz)

LTE(10 MHz)

880 890 915 925 935 960

GSM1800(75 MHz)

GSM1800(75 MHz)

GSM1800(18 MHz)

GSM1800(8 MHz)

LTE(10 MHz)

1710 1785 1805 1880

GSM1800(3 MHz)

LTE(15 MHz)





Example – European LTE New Spectrum

In many countries new spectrum is becoming available in which LTE could be implemented. The large number of defined LTE bands and the fact that it is ‘bandwidth agnostic’ means that most new spectrum can be considered for LTE operation.

The example shown in the diagram is for 190 MHz of spectrum that is likely to be offered in the UK. The aim is to offer the spectrum in a very flexible way. It is divided into 5 MHz blocks that can be licensed individually or in groups. There is also a nominal division between that which is offered for FDD use and that which is offered for TDD use. The split shown at the top of the diagram is the minimum configuration for TDD spectrum and corresponds exactly to LTE FDD band 7 and LTE TDD band 38. However, as shown in the diagram, it is envisaged that some of the FDD spectrum could be assigned for TDD operation. This would be outside the scope of the current LTE specification, but this spectrum is likely to be offered as being independent of technology choice.

Additional spectrumallocated as TDD from here

Additional spectrumallocated as TDD from here

2500 2570 2620 2690Nominally paired (FDD) Nominally paired (FDD)Nominally unpaired (TDD)

Potential organization for UK 2.6 GHz licences (blocks of 5 MHz)

FDD TDD FDD TDD

Operator 1 FDD + TDD

Operator 2 FDD + TDD

Operator 3 FDD

Operator 4 TDD

Operator 5 TDD

Guard

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38


Frequency Planning

Considerations for an SFN

For most cellular technologies, single frequency reuse is not considered an option unless CDMA is in use. The reason for this is the high level of mutual interference that is assumed to result. However, it is not the case that there will always be an unacceptably high level of interference between two adjacent cells using the same frequency allocation.

Consider two mobiles in two adjacent cells using the same frequency allocation. Both mobiles will be receiving a wanted signal ‘C’ and a co-channel interfering signal ‘I’. When the mobiles are close to their respective serving cells there will be a large difference in the two signals that results in a strongly positive signal-to-noise ratio. It can be shown that the best signal quality results from both cells transmitting higher downlink powers. In this scenario good performance is achievable for both mobiles whilst maintaining a very spectrally efficient single-frequency reuse pattern.

As the mobiles move further from their respective serving cells and closer to the edge-of-cell area, the signal-to-noise ratio degrades. Once they reach edge-of-cell there will be little difference between the wanted signal ‘C’ and the interfering signal ‘I’; i.e. the SNR will approach 0 dB. The result will be very poor performance or loss of connection. However, it can be shown that the signal-to-noise ratio can be improved with increasing difference between the respective cell transmit powers. The ideal situation would be to switch one cell off while the other was transmitting maximum power. Such a working condition is not normally considered viable since one or other mobile would be denied service. However, an OFDMA-based system can offer a compromise in terms of spectrum sharing.



Partial Frequency Reuse in an SFN

When adjacent LTE eNBs are allocated the same frequency resource, the scheduling can be coordinated between them. This is organized such that for UEs on the edge of cell the selection of allocated RBs (Resource Blocks) will be selected from different parts of the available channel bandwidth. The example shown is based on 5 MHz bandwidth with 25 available RBs. Each eNB has the same channel frequency and each has allocated five RBs to a UE on the edge of cell. However, the five allocated RBs are in a different part of the 5 MHz bandwidth. The remainder of each of the eNBs resource can be allocated to in-cell UEs in the normal way. Thus the full capacity is potentially available to each eNB with the restriction that only partial capacity is available to UEs in edge-of-cell areas.

This coordination can occur in two ways. Firstly, the protocol used on the X2 interface, which links eNBs, includes a facility for direct resource negotiation between the eNBs. However, it is optional for this functionality to be used. Even in the case where direct negotiation is not performed the selection of allocated resource is dynamic, very frequent and based on channel quality assessment. Thus the eNBs will tend to schedule resources that show the lowest value of interference.

Coordination of resource allocation in this way at the edge-of-cell while allowing full resource allocation within the cell can be described as ‘partial frequency reuse’.

C1

C2

X2 Interface(resource negotiation)

Full cell capacity

Full cell capacity

frequency

frequency frequency

Same frequency allocation to both cells


Frequency Planning

Limitations of Partial Frequency Reuse

In typical physical cell architecture involving three-cell sites it is important to remember that the term edge-of-cell is not only at the most distant points for the eNB. Edge-of-cell includes the areas of overlap between cells (or sectors) on the same eNB. These regions run from the edge of coverage back and up to the eNB site. When an SFN frequency allocation is used these intra-site overlap areas are potentially subject to very high levels of interference. In particular, because of the close proximity of UEs to the eNB, uplink interference from UEs served by adjacent cells may be even higher.

As seen in the diagram, the area within the nominal cell coverage in which un-negotiated full cell capacity is available for allocation to UEs is relatively small. It can also be seen that even in a regular and idealized coverage plan there is a need to coordinate resource allocation between up to three different cells on three different eNBs. This means that while the peak bit rates achievable in the in-cell area may be very high, the average throughput may be lower than for a frequency planned system using a lower radio bandwidth.

Nevertheless, there are exceptions where the SFN partial frequency reuse strategy becomes very attractive. The first is where LTE is being used to provide fixed wireless broadband access. In this case the UEs can be assumed to have high gain directional antennas. The antenna gain provides significant isolation from adjacent cell interference and in some cases removes the need for resource negotiation. Thus cell-edge throughput can remain very high. The second exception is for the use of the more advanced forms of MIMO operation, particularly the options for beamforming and MU-MIMO.



Multi-Frequency Networks

In an idealized three-frequency reuse pattern the complete resource bandwidth should be available in all areas of the cell without the need for resource negotiation between eNBs. However, for any given licence spectrum this will require subdivision to create the three channels. The result will be reduced maximum throughput, but more consistent performance across the cell area. In general the average throughput for the system will be higher than for an equivalent SFN approach.

Nevertheless, non-idealized plans may show different characteristics. There is still a strong likelihood that adjacent reuse sectors will suffer from some interference.


Frequency Planning

Example Frequency Plan with Three Channels

The diagram shows a screenshot indicating the layout of a simple three-frequency plan. The plan is based on LTE FDD band 1 with an assumed licence for 15 MHz of spectrum. The hypothetical operator has subdivided the band to create three 5 MHz bandwidth allocations. The channels have been added manually one to each sector in a geometrically repeating pattern on each eNB.

The same licence for 15 MHz of spectrum will also be studied when allocated as an SFN using a single 15 MHz channel.



Example Frequency Plan with Six Channels

Further studies have been performed assuming a licence for 20 MHz of radio spectrum with which the hypothetical operator has created six channels each with 3 MHz bandwidth. The screen shot shows the frequency plan.


Frequency Planning

SINR for a Three-Frequency Planned Network

The Atoll planning tool has been used to calculate the downlink SINR for the network when configured for three frequencies of 5 MHz bandwidth. Note that over most of the ground within the focus zone the SINR is above 12 dB with some areas exceeding 25 dB.



SINR for a Six-Frequency Planned Network

The Atoll planning tool has been used to calculate the downlink SINR for the network when configured for six frequencies of 3 MHz bandwidth. Note that over most of the ground within the focus zone the SINR is above 20 dB.


Frequency Planning

SINR for an SFN Configuration

The Atoll planning tool has been used to calculate the downlink SINR for the network when configured for a single frequency of 15 MHz bandwidth. Note that the SINR is generally much lower than for frequency planned network configurations over almost all of the ground area.



Downlink Throughput for a Three-Frequency Network

This screen shot shows a study of DL (Downlink) RLC (Radio Link Control) throughput when the network is configured with three frequencies. It can be seen that a rate in the region of 17 Mbit/s is achieved across a significant proportion of the ground area within the focus zone.


Frequency Planning

Downlink Throughput for a Six-Frequency Network

This screen shot shows a study of DL RLC throughput when the network is configured with six frequencies. It can be seen that a rate in the region of 11 Mbit/s is achieved across most of the ground area within the focus zone. This is lower than the peak bit rate achieved in the three-frequency configuration because the channel bandwidth is lower. However, this rate is achieved over a larger area because the SINR performance was better.



Downlink Throughput for an SFN (1)

This screen shot shows a study of DL RLC throughput when the network is configured as an SFN with a channel bandwidth of 15 MHz. It can be seen that rates achievable over the ground area within the focus zone are very variable, but the highest rate is in excess of 20 Mbit/s. This is higher than the peak bit rate achieved in the three-frequency configuration because the channel bandwidth is higher. However, this rate is achieved over a smaller area because the SINR performance was poorer.


Frequency Planning

Downlink Throughput for an SFN (2)

In order to study in more detail the effect of using an SFN strategy the display scale has been modified for this study. Now the variation on performance across the cell area can be more clearly seen, as can the increase in peak performance, which in some places reaches rates in excess of 50 Mbit/s.



Histograms

Histograms provide a very effective way of contrasting the performance variations between a frequency-planned segmented approach and a single-frequency network approach. This example shows the consistency of service provision for the three-frequency network configuration where 18–19 Mbit/s is being achieved across 60% of the ground area. The consistency of service provision is lifted to more than 80% for a six-frequency plan, but at the expense of ultimate performance, since the rate achieved falls to 11–12 Mbit/s.

The distribution is very different for the SFN configuration. Peak rate is significantly improved, reaching 54–55 Mbit/s, but over only 4% of the ground area.

3FN – 5 6FN – 3

SFN – 15


Frequency Planning

Downlink Throughput for Fixed Users in a 3FN

The Atoll Tool is also able to model the effects of providing fixed radio access. In this case the users are assumed to have high-gain antennas directed at the intended serving cell. As can be seen, the effect of the antenna on coverage is considerable. The peak bit rate is still limited to 18–19 Mbit/s by the channel bandwidth of 5 MHz, but this capability is now available across almost all of the ground area in the focus zone.



Downlink Throughput for Fixed Users in an SFN (1)

When the three-frequency configuration for fixed users is replaced by an SFN configuration, the rate rises, as would be expected. However, unlike the mobile case, where more extreme service variation was seen, the directivity in the high-gain antennas used by subscribers provides isolation from neighbour-cell interference and thus improves performance over a larger ground area.


Frequency Planning

Downlink Throughput for Fixed Users in an SFN (2)

The effect of the SFN configuration in a fixed radio access system is more clearly seen with scale adjustment and the histogram. This indicates the highest bit rate (more than 50 Mbit/s) may be available over more than 80% of the ground area.



Downlink Throughput for MIMO Users in a 3FN (1)

The Atoll tool is able to perform studies on the effects of using a variety of MIMO configurations. In this case a 2x2 MIMO configuration for mobile users is being studied in the three-frequency network set-up. It is clear that the study suggests an improvement both in terms of throughput and in terms of coverage area.


Frequency Planning

Downlink Throughput for MIMO Users in a 3FN (2)

The effects of the MIMO configuration in the 3FN system can be more clearly seen with scale adjustment and the histogram. It can be seen that the peak rate has increased to more than 30 Mbit/s and that this rate is available over approximately 75% of the ground area within the focus zone.



Downlink Throughput for MIMO Users in an SFN (1)

In this study a 2x2 MIMO configuration is being used along with an SFN arrangement using 15 MHz channel bandwidth. The use of MIMO has a marked effect on the performance of the network when an SFN configuration is used. Bit rate is increased, as would be expected, but most significantly MIMO also appears to be compensating for the poor SINR at edge-of-cell and high bit rates are still being achieved over a significant ground area.


Frequency Planning

Downlink Throughput for MIMO Users in an SFN (2)

The real effects of the MIMO configuration in the SFN system can be more clearly seen with scale adjustment and the histogram. It can be seen that the peak rate has increased to more than 90 Mbit/s. However, this rate is available in only about 3% of the ground area. Nevertheless, very good rates are still achieved over a wide area. Overall users could expect access to rates more than 17 Mbit/s in about 95% of the ground area.



IDLE MODE PARAMETERS



SECTION 4



CONTENTS

Idle Mode Parameters


RRC States. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.1

RRC Inter-RAT State Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.2

LTE State Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.3

Idle Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.4

Selection and Idle Mode Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.5

PLMN Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.6

Cell Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.8

Parameters for Initial Cell Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.9

Cell Selection Modifications for CSG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.10

Cell Barring at Cell Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.11

Cell Barring for RRC Connection Establishment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.12

Idle Mode Neighbour Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.13

Periodic HPLMN Searches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.14

Cell Reselection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.15

Priority in Frequency and Technology Layers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.16

Measurement Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.17

Normal Cell Reselection Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.18

Reselection and Ranking Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.19

Parameters for Cell Reselection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.20

Mobility States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.21

Scaling Rules for Mobility States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.22

LTE Neighbour Lists in UMTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.23

UMTS Measurement Rules without Absolute Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.24

UMTS Measurement Rules with Absolute Priorities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.25

UMTS Reselection Criteria without Absolute Priorities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.26

UMTS Reselection Criteria with Absolute Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.27

LTE Neighbour Lists in GSM/GPRS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.28

GSM Measurement Rules with Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.29

GSM Reselection Criteria with Priorities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.30




OBJECTIVES



■ define idle mode for LTE and identify the activities performed by the UE in this mode

■ describe the interaction between the NAS and AS for network selection and explain the

parameters involved

■ describe the processes and criteria used for cell selection

■ define each cell selection parameter in terms of function setting range and distribution

mechanism

■ describe the processes and criteria used for cell reselection for intra-LTE reselections and

for inter-RAT reselections

■ define each cell reselection parameter in terms of function setting range and distribution

mechanism

■ identify the changes required to facilitate reselections to LTE from non-LTE RATs





RRC States The RRC idle state refers to terminals that are powered on and have performed network access, but that are currently not supporting any active connections. RRC idle terminals will monitor the paging channel in the camped-on cell and will perform cell reselection as required. Idle UEs have no RRC context with any eNB and therefore have no C-RNTI assigned. The only transitory identity they have will be the TMSI used for paging purposes by the MME (Mobility Management Entity). A connected UE will have an active RRC context in place with an eNB. Its location will therefore be known down to the serving-cell level and it will have a C-RNTI assigned. As part of the RRC context establishment process the eNB will have contacted the HSS (via the MME) and received security and authentication vectors for the UE. Ciphering and integrity keys will therefore also be in place. RRC connected does not necessarily imply that the UE has any active EPS bearers, only that it has made contact with an eNB.


RRC CONNECTED

RRC IDLE

UE has an E-UTRAN RRC connectioneNB stores an RRC context

E-UTRAN knows which cell the UE is inEPS can transmit and/or receive data to/from the UE

Neighbour cell measurements and reportingNetwork-controlled mobility

Monitors BCH system informationMonitors paging channelPerforms cell reselectionAssigned TAID by MME

Performs tracking area updatesNo stored RRC context in the eNB



RRC Inter-RAT State Transitions

Both Inter-RAT (Inter-Radio Access Technology) handover and cell reselection are defined for LTE, which means that defined state transitions must also be defined for interworking to the radio resource control states in other technologies.

The diagram shows the state transitions for UMTS and GSM/GPRS.

RRC LTE idle mode transition for both UMTS and GSM/GPRS are primarily by reselection. However, for GPRS operation an option for CCO (Cell Change Order) also exists.

The UMTS RRC connected state has a number of substates that are not a feature of LTE. Therefore state transition between the two systems in the RRC connected state varies dependent on traffic activity and on direction. Handover is supported both to and from the UMTS CELL_DCH state from the LTE RRC connected state irrespective of packet activity. However, in the reverse direction a UE in the UMTS RRC connected state but that is in the substate CELL_PCH or URA_PCH would return to LTE through cell reselection.

Similarly, transitions for RRC connected UEs to and from GSM/GPRS are also affected by the traffic or signalling activity. Real-time traffic is most likely to be handed over between LTE and GSM, but for GPRS operation options for CCO or CCO with optional NACC (Network Assisted Cell Change) exist.


Connection establishment/

release

IDLE RRC IDLE

CELL_DCH

CELL_FACH

CELL_PCHURA_PCH

RRC CONNECTED

GSM Dedicated

GSM_Idle/ GPRS Packet_Idle

GPRS Packet transfer mode

UMTS LTE GSM/GPRS

Reselection


release

Handover

Reselection

CCO, reselection


release

RRC CONNECTED



LTE State Management

In order to offer effective service to UEs, the EPS needs to be able to define and keep track of the availability and reachability of each terminal. It achieves this by maintaining two sets of ‘contexts’ for each UE – an EMM (EPS Mobility Management) context and an ECM (EPS Connection Management) context – each of which is handled by ‘state machines’ located in the UE and the MME.

A further state machine operates in the UE and serving eNB to track the terminal’s RRC state, which can be either RRC-IDLE (which relates to a UE in idle mode) or RRC-CONNECTED (which relates to a UE with an active traffic bearer).

EMM is analogous to the MM processes undertaken in legacy networks and seeks to ensure that the MME maintains enough location data to be able to offer service to each UE when required. The two EMM states maintained by the MME are EMM-DEREGISTERED and EMM-REGISTERED.

The ECM states describe a UE’s current connectivity status with the EPC, for example whether an S1 connection exists between the UE and EPC or not. There are two ECM states, ECM-IDLE and ECM-CONNECTED.

Although the EMM and ECM states are independent of each other they are related and any discussion of a UE’s reachability is best served by viewing these states in a combined fashion. There are three main phases of UE activity, each of which can be described by a combination of EMM and ECM states. These are with the UE powered off, with the UE in idle mode and the UE with an active traffic connection.

Further Reading: 3GPP TS 23.401

MME

eNBUE

RRC

Connected

Idle

EMMEMM

Registered

Deregistered

ECMECM

Off Attaching Idle Connecting Active

Connected

Idle

RRC

Deregistered Registered

Idle Connected

Idle Connected Idle ConnectedRRC

ECM

EMM



Idle Mode

Idle mode represents a state of operation for the UE where it has successfully performed the following: PLMN selection, cell selection and location registration (by tracking area). Once in idle mode, the UE will continue to reassess the suitability of its serving cell and, in some circumstances, its serving network. In order to do this it will implement cell and PLMN reselection procedures. A UE in idle mode will be monitoring its current serving cell in terms of radio performance and signalling information. The radio performance measurements are done on the basis of a quality measure. This is an assessment of radio signal strength and interference level, and it can be made for both the serving cell and its neighbours. The aim will be to ensure that the UE is always served by the cell most likely to give the most reliable service should information transfer of any kind be required. The UE will also be monitoring two key types of signalling from the serving cell system information messages and paging or notification messages. System information messages convey all the cell and system parameters. The UE will record changes in these parameters that may affect the service level provided by the cell, or access rights to the cell. Changes in these parameters could provoke a cell reselection, or a PLMN reselection. Paging or notification messages will result in connection establishment. All of these procedures are performed through communication between the AS and the NAS. In general, instructions are sent from the NAS to the AS; the AS then performs the requested procedure and returns a result to the NAS.

If CSG (Closed Subscriber Group) is supported then these procedures are modified such that a cell’s broadcast CSG ID forms another level of differentiation between cells. CSG is intended for use with HeNBs (femtocells).


PLMN selection and reselection

Cell selection and reselection

Location registration

Support for manual CSG ID

selection

Location registration response

Service requests

Indication to userManual

mode

Automatic mode

Available PLMNs

Selected PLMN

Registration area changes

Location registration response

NAS control

Radio measurements

CSG ID selected

Available CSGIDs to NAS



Selection and Idle Mode Activities At switch-on, the UE has a number of tasks to perform in order to ensure that it is in a condition to obtain services through a network as required. The first of these is to perform PLMN Selection. The selection process is performed by the Non-Access Stratum (NAS) part of the protocol stack, and may involve input from the user. Having selected a PLMN the UE is required to select a suitable cell belonging to the selected PLMN. Registration is then performed through the camped-on cell. After a successful registration the UE will assume the camped normal state and begin idle mode tasks. Idle mode tasks will involve neighbour cell measurements, cell reselection, system information monitoring and paging monitoring. The precise behaviour of the UE when performing these tasks will depend upon the camped-on cell’s channel configuration and upon the setting of several related parameters in system information.

Further Reading: 3GPP TS 23.122, TS 36.304

System information

for idle mode

Scan neighbours as required for cell reselection

Cell reselection

Camped Normal Idle Mode

AS in UE

AS in UE

Selected PLMN/RAT

Suitable cell found

Scan and test for a suitable cell on selected PLMN

Registration

Cell selection

AS in UE

NAS in UE

Automatic Manual

Select PLMNand RAT

Scan for radio carriers and identify

PLMNs

Results (PLMN/RATs

found)

PLMN selection

AS in UE

NAS in UE



PLMN Selection

PLMN selection involves interaction between the AS (Access Stratum) and NAS (Non Access Stratum) in the UE. The AS performs scanning for cells across all supported channels in the E-UTRA band. If the UE has previously been registered with an LTE system it may optionally use stored information to optimise this search.

The strongest detected cells on each carrier frequency are reported to the NAS for PLMN selection. Note that a single cell may be broadcasting more than one PLMN ID, in which case the cell is reported separately with respect to each PLMN ID. If the measured signal level exceeds –110 dBm then a cell is considered to have passed the ‘high quality’ threshold and is reported as such with no specific signal level. For cells below this threshold the measured signal level is reported along with the PLMN ID.

PLMN selection from the reported PLMN IDs is the responsibility of the NAS. As with other 3GPP technologies, this would typically be done automatically with reference to preset priorities, or, if set by the user, can be performed manually as a user choice.

Once the NAS has performed PLMN selection it will instruct the AS to perform cell selection on the selected PLMN.

Further Reading: 3GPP TS 36.304; 5, TS 23.122; 4

E-UTRAFrequency 1

PLMN 1IRATFrequency 4

PLMN 2

NASselect

ASscan

E-UTRAFrequency 2

PLMN 3

E-UTRAFrequency 1

PLMN 1PLMN 2PLMN 3



PLMN Selection (continued) PLMN selection is a NAS function, but the AS provides the list of available PLMNs from which the selection is made. To compile this list, the UE is required to scan all carriers within its frequency capability (this may include non-LTE RAT carriers depending on the UE capability and network availability). On each carrier on which a signal is received the UE will synchronize to the cell with the strongest signal level and attempt to read the PLMN identity (or identities) from the system information. The AS reports all successfully read PLMN identities to the NAS. Each detected PLMN/RAT combination is compared with a defined ‘high-quality’ criterion. Those exceeding the high-quality criterion are reported directly and those below it are reported along with a specific signal strength measurement. The UE may optimize this measuring and reporting process through the use of stored information. NAS selection of a PLMN may be done automatically or manually. In automatic mode the available PLMNs are listed in priority order and the highest priority PLMN is selected. In manual mode a list of the available PLMNs is presented to the user in priority order, but the user may select any PLMN from the list.

Further Reading: 3GPP TS23.122; 4.4.3.1.1, 4.4.3.1.2, TS 36.404; 5.1.2.2

AS in UE

NAS in UE

SIM in UE

Results(PLMN/RATs

found)

Read files

mBd58–ISSRSRPG/MSGmBd48–PCSRDDTSTMUmBd59–PCSRDDFSTMU

mBd011–PRSRETL

noiretirCytilauQhgiH

User PLMN listOperator PLMN List

PLMN Priority List

1. The HPLMN or the highest priority EPLMN

2. Highest priority PLMN/RAT combination listed in the user controlled PLMN selector data file in the SIM

3. Highest priority PLMN/RAT combination listed in the operator controlled PLMN selector data file in the SIM

4. Other PLMN/RAT combinations meeting the high quality criterion in random order

5. Other PLMN/RAT combinations in order of decreasing quality



Cell Selection

Once the NAS has selected a PLMN it will indicate this to the AS and request that the AS finds a suitable cell on the selected PLMN.

Dependent on circumstances the UE may use either initial cell selection or stored information cell selection. In the former case the UE will look for the strongest cell by scanning its complete E-UTRA frequency band capability. In the latter the UE may optimise the scan by using stored information on the last used cell. In either case the UE looks only for the strongest cell based on a measurement of RSRP.

Once the strongest cell has been identified the UE will test it for suitability using the list of requirements in the diagram and suitability ‘S-criterion’. The S-criterion is fulfilled when Srxlev is greater than zero for the conditions defined in the diagram. If the cell is suitable then it will be selected. If it is not suitable then the UE will scan for the next strongest signal.

Following successful cell selection an indication will be given to the NAS, which will subsequently initiate the location registration process.

Further Reading: 3GPP TS 36.304;4.3, 5.2.3

The UE scans for the strongest cell first and then tests for suitability.

A cell is suitable if:

The cell is in the selected PLMN or Equivalent PLMNThe cell is not barredThe cell is in at least one TA that is not part of ‘forbidden TAs for roaming’For CSG, the cell is part of the UE’s CSG white list

and if:

Srxlev > 0 (dB)

according to:

Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) – Pcompensation

where:

Pcompensation = max(PEMAX_H – PPowerClass, 0)

and where:

Qrxlevmeas = measured cell DL RSRP in dBmQrxlevmin = minimum required cell DL RSRP in dBmQrxlevminoffset = offset for Qrxlevmin in dB (set to 0 for intial cell selection)PEMAX_H = max permitted UL TX power in the cell in dBmPPowerClass = max UE TX power in dBm (from power class)



Parameters for Initial Cell Selection

The table shows details for all the parameters that are used for suitability testing in regard of initial cell selection under normal conditions. Note that some of these parameters are also used for cell reselection, but in that case they will be sourced from different locations and may have different values.

Further Reading: 3GPP TS 36.331; 6.2, 6.3

Parameter Source Value Unit

PLMN ID SystemInformationBlockType1 - - SystemInformationBlockType1 Cell Barred (All PLMNs) – on/off -

SIB Type 2

Cell reserved for operator use (Per PLMN) – on/off -

Emergency – on/off -MO-Signalling – on/off -MO-Data – on/off -Barring for AC (Access Class)

-Barring factor – 0...0.95 (step 0.05)-Barring time – 4,8,16,32,64,128,256,512- Special AC – 11...15 (5 bits)

Q rxlevmeas Physical layer measurement - dBm

Information element value = –70...–22Working value = IE value x 2 = –140...–44

Q rxlevminoffset SystemInformationBlockType1 Taken as 0 for initial cell selection dB

PPowerClass UE Characteristic Only power class 3 defined (23 dBm, 0.2 W) dBm

PEMAX_H SystemInformationBlockType1 Equivalent to P-Max = –30...33 dBm

Cell Barring

Q rxlevmin SystemInformationBlockType1 dBm



Cell Selection Modifications for CSG

In addition to normal initial scanning for PLMNs, the NAS may request the AS to scan for CSG IDs (Closed Subscriber Group Identities). In this case the UE will also look for the CSG ID (carried in SystemInformationBlockType1) on the strongest cell for each carrier frequency. It will report the CSG ID along with the HeNB name (carried in SIB Type 9), if available.

If the NAS selects a reported CSG ID then this is indicated to the AS and the cell selection suitability test is supplemented with the requirement for a cell belonging to the selected CSG.


AS in UE

NAS in UE

CSG ID (SystemInformationBlockType1) HeNB name (SIB 9)

HeNB

Requests scan for CSG IDs

Reports CSG ID + HeNB name and modifies suitability

criteria if selected by NAS



Cell Barring at Cell Selection

The flow chart in the diagram summarizes the process for determining cell barred status in respect of the determination of ‘suitability’ during cell selection.

Note that if the barred cell is a CSG cell then the UE is permitted to select an alternative cell on the same frequency irrespective of the information element intraFrequencyReselection.

Once a cell is selected, the UE will attempt to register, which requires the establishment of an RRC connection. This RRC procedure is itself subject to more cell barring conditions based on the access class, or classes, of the SIM.


Start suitability test for barring

Cell barred?Do not select/

reselectIntra-frequency

reselection?Intra-

freq not allowed

Intra-freq allowedPLMNn

reserved for operator

use?

Select if suitable

A

AUE part of PLMNn?

UE has valid

AC 11-15? A

AC 11-15 for UE not barred?

A

Y

N

Y

Y

N

N

N

NN

Y

Y

Y



Cell Barring for RRC Connection Establishment

Even though a cell may not be barred for the purposes of camping-on, the operator may still choose to implement complete or partial barring in regard of access to cell resources. Assessment of access class barring is performed as part of the RRC connection establishment procedure.

This functionality is based on the access classes associated with the SIM card, which remain unchanged in definition from UMTS and GSM. Thus all SIMs will be allocated one access class in the range 0–9, some SIMs will have one or more additional access class in the range 11–15, and all SIMs will assume access class 10 when making an emergency call. Note that access classes 11 and 15 are for operator use and are only valid in respect of the HPLMN. Note also that access classes 12, 13 and 14 are for use by public safety and public utility organizations and are only valid in the home country.

The parameters required for access class baring are carried in SIB Type 2. The procedure applied for the four defined types of access attempt are summarized in the flows shown in the diagram. Note that if a call attempt is barred for MO Data or MO signalling then a timer is started which retains the barred state for a period of time given by:

T303 or T305 = (0.7 + (0.6 x rand)) x ac-BarringTime


Initiate RRC connection

establishment

Y

NACBarring Info

present?

Responseto Page

EmergencyCall MO Data

SendRRCConectionRequest

AC10barred?

UE has valid AC11-15?


A

A

CellBarred

N

N

Y

N

MOSignalling

Drawrand

Y

Y

MO Data barring infopresent?

Y

N

Start T303

Drawrand

MO Sigbarring infopresent?

N

Y

Y

N

rand<AC barring

factor?

N

N

N

A

A

ACBarring Info

present?

Y

Y

N

N

A

A

ACBarring Info

present?

Y

YUE has valid AC11-15?

Y

UE has valid AC11-15?

Y


YA A A


CellBarred

N

CellBarred

Nrand<AC barring

factor?

A A

Start T305

A



Idle Mode Neighbour Lists

In order for the UE to perform tasks relating to cell reselection in idle mode it requires information about the frequencies, technologies and cells that it should consider for reselection. This information is provided in SIBs 3 to 8. However, the specific SIBs used depends on the frequency and technology options that will be considered. The table outlines which SIB relates to each of the different neighbour cell types. Note that information relating to intra-frequency LTE is split between SIB Type 3 and SIB Type 4.

An example summarizing the general content of SIB Type 5 (inter-frequency LTE cells) is shown. Inter-frequency information is provided as a set for each inter-frequency layer included in the SIB. Information within the set is specific to the frequency layer. The set may optionally include a neighbour list. For each neighbour in the n-cell list the physical layer ID and a cell-specific reselection offset is provided. Note that the UE is required to be able to scan and ‘detect’ neighbours on a given frequency and thus an operator may choose not to include the n-cell list. Additionally, the set may include a black-cell list. Each entry in the black-cell list is either a single physical cell ID or a range of physical cell IDs. This list can be used by an operator to prevent reselection to cells ‘detected’ by the UE on the given inter-frequency.

The format for SIB Type 6 is similar to that shown for SIB Type 5. However, SIB Type 7, for GSM cells, differs in that it consists of a list of ARFCNs and an accompanying bit map identifying ‘allowed’ values for the NCC element in the BSIC. Thus, unlike a standard GSM n-cell list, it does not list specific BSICs.

The detailed format for SIB Type 8 is also different from SIB Types 4, 5 and 6, but it does still include information specific to frequency layers. The key difference lies in the included reselection parameter set, which is very different for this non-3GPP technology.


Message N-list Other Information

SIB Type 3 - Common reselectionparameters

SIB Type 4 LTE intra-freq Layer-specific reselectionparameters

SIB Type 5 LTE inter-freq Layer-specific reselectionparameters

SIB Type 6 UMTS Layer-specific reselectionparameters

SIB Type 7 GSM/GPRS Layer-specific reselectionparameters

SIB Type 8 1x/1xEV Layer-specific reselection parameters

Physical cell ID_1 + Reselection offset

... Physical cell ID_n + Reselection offset

Physical cell ID_1 or ID range_1

...Physical cell ID_n or ID range_n

... Inter-frequency carrier information_n

Carrier frequency Reselection parameters Layer priority Measurement bandwidth MIMO setting N-cell list

Black-cell list

SIB Type 5 Inter-frequency carrier information_1



Periodic HPLMN Searches

Once the UE has selected a cell belonging to the selected PLMN and, if appropriate, a selected CSG ID, it will register and enter idle mode. At this point the UE will begin procedures relating to cell reselection. If the UE is in a VPLMN (Visited PLMN) then the normal reselection processes will relate only to cells in the current RPLMN (Registered PLMN), which is not the UE’s HPLMN (Home PLMN). Therefore, when the RPLMN is a VPLMN the UE also performs periodic searches for the HPLMN or a higher priority EPLMN (Equivalent PLMN).

The first search after switch-on is made no sooner than two minutes later, but before a timer value ‘T’ has elapsed. The value T is preconfigured on the SIM card and can be set between six minutes and eight hours in steps of decihours. Subsequent searches then occur with a periodicity of ‘T’. During such searches the UE may find a cell belonging to its home network or a higher priority equivalent network. The cell reselection processes are then used to evaluate the cell, but when Srxlev is calculated, the variable Qrxlevminoffset is included with its broadcast value. This and the value of Qrxlevmin used will be as received from the evaluated cell in the higher priority PLMN and not those broadcast in the current camped-on cell.

Qrxlevminoffset provides an offset in the Srxlev calculation; the information element value is variable between one and eight, but the value used in the calculation is multiplied by two and thus in effect Qrxlevminoffset is variable between two and 16.

Further Reading: 3GPP TS 23.122; 4.4.3.3.1, TS 36.304; 5.2.3.2

Normal cell reselection measurements and assessment includes only VPLMN cells based on parameters

received from the camped-on cell

UE also scans for the HPLMN with periodicity ‘T’

T is configured on the SIM and is set in multiples of decihours between 1 and 80 (6min – 8 hours)

Srxlev for HPLMH reselection includes Qrxlevminoffset, received in

SystemInformationBlockType1

Qrxlevminoffset = IE value (1...8) x 2VPLMN

HPLMN

Camped-on cell



Cell Reselection

Cell reselection in LTE both reuses many principles that were are well established in legacy technologies as well as introducing some new strategies. A key addition for LTE is the use of RAT/frequency prioritization. Each frequency layer that the UE may be required to measure, either E-UTRA or any other RAT, is assigned a priority. The cell-specific priority information is conveyed to UEs via system information messages. Additionally, UE-specific values can be supplied in dedicated signalling, in which case they take priority over the system information values. Any indicated frequency layers that do not have a priority will not be considered by the UE for reselection.

In general the measurement rules are used to reduce unnecessary neighbour cell measurements. Measurements are then evaluated for potential reselection. Again the frequency/RAT priority level is used along with system defined threshold for this assessment. In addition to all of this the UE will apply scaling to Treselection, hysteresis values and offset values dependent on an assessment of its mobility state, which may be high, medium or low. This is based on an analysis of resent reselection frequency.


Based on priority of RAT/Frequency layers

and thresholds

Based on priority of RAT/Frequency layers

and thresholds

Based on measurements, offsets, parameters and

mobility status

1 sec since last reselectionCell is suitable

I-RATInter-frequency

E-UTRAInter-frequency E-UTRA

Intra-frequency

Low

Medium

High

Measurement rules

Evaluation

Ranking

Reselection



Priority in Frequency and Technology Layers

Optionally, priority levels can be allocated to LTE frequency layers and to each applicable IRAT layer. Priority levels are indicated in system information for each of the technology and frequency layers as indicated in the table. However, they may be modified with dedicated signalling using the RRCConnectionRelease message.

Priority levels are allocated a value between 0 and 7 where 7 is the highest priority. However, CSG cells are treated as if they have a priority higher than 7 irrespective of the indicated priority for the frequency layer they use.

Once allocated, priority levels are used to influence the cell reselection process.

Different LTE frequency layers may have the same priority, but priorities may not be equal for different radio access technologies.

Further Reading: 3GPP TS 36.304; 5.2.4.1

Frequency Layer 1 (e.g. LTE F1_FDD)

Frequency Layer 1 (e.g. LTE F2_FDD)

Frequency Layer 1 (e.g. LTE F3_TDD)

Frequency Layer 1 (e.g. UMTS FDD)

Frequency Layer 1 (e.g. UMTS TDD)

Frequency Layer 1 (e.g. 1xEV)

Frequency Layer 1 (e.g. 1x)

Frequency Layer 1 (e.g. GSM/GPRS)

Priority = 7

Priority = 6

Priority = 5

Priority = 4

Priority = 3

Priority = 2

Priority = 1

Priority = 0

CSG cells treated as priority >7

LTE Intra SIB Type 3

LTE Inter SIB Type 5

UMTS SIB Type 6

GSM SIB Type 7

1x/1xEV SIB Type 8

NB. Can be modified with dedicated signalling



Measurement Rules

The measurement rules are used to limit unnecessary measurement activity for the UE. They are summarized in the diagram but in general they ensure that the UE will tend to measure cells in a higher priority layers unless the quality of the currently selected layer becomes unacceptably poor.

Note that the parameters Sintrasearch and Snonintrasearch are optional. If they are not included in SIB Type 3 then the UE will measure all indicated frequency and technology layers and the measurement rules have no effect.


If SServingCell > Sintrasearch UE may not measure

UE must measure

Sintrasearch not sent UE must measure

Intra-frequency Measurements

hcraesartniSlleCgnivreSSfI

Selected cell

LTE F1

LTE F1

UE must measure

Equal or lower priority layer

UE may not measure

UE must measure

Snonintrasearch not sent UE must measure

Inter-frequency and Inter-RAT Measurements

SServingCell = SrxlevSintrasearch = 0...31 dB (in SIB Type 3)Snonintrasearch = 0...31 dB (in SIB Type 3)

Higher priority layer

If SServingCell > Snonintrasearch

hcraesartninonSlleCgnivreSSfI

UMTS/GSM/

1x/1xEV

Selected cell

LTE F1 LTE F2



Normal Cell Reselection Criteria

If frequency layer and technology layer priorities have been allocated then the UE behaviour with regard to a particular n-cell will depend on the relative priority of the layer to which it belongs. If priorities have not been allocated for a frequency or technology layer then the UE will not perform reselection evaluation for that layer.

Note that ultimate reselection is still subject to suitability and therefore a cell will not be reselected if it is found to have access restrictions that apply to the UE. Additionally, in the case where more than one cell meets the reselection criteria, the ranking criterion is used to determine the best cell for reselection.

Further Reading: 3GPP TS 36.304; 5.2.4.4, 5.2.4.5, 5.2.4.6

Criteria 1:SnonServingCell,x (Srxlev) > Threshx,high for TreselectionRAT

andCamped on current selected cell for more than 1 second

Higher Priority N-Cells

Criteria S:SnonServingCell,x (Srxlev) > 0

andRanking criterion Rn > Rs for TreselectionRAT

andCamped on current selected cell for more

than 1 second

Equal Priority N-Cells

Lower Priority N-Cells

No higher priority cell fulfils Criteria 1and

No equal priority cell fulfils the Ranking Criteriaand

SServingCell,x (Srxlev) < Threshserving,low for TreselectionRAT

andLower priority n-cell SnonServingCell,x (Srxlev) > Threshx,low for TreselectionRAT




Reselection and Ranking Criteria

Both Criteria 1 and Criteria S are based on a calculation of Srxlev; either for the serving cell or for a considered neighbour cell. The calculation and key parameters for this are shown in the diagram. Although the calculation is essentially the same as that used for cell selection, the values of the parameters used are related to the frequency/technology layer of the cell in question. They are sourced from a different location to those used for cell selection and may have different values.

The diagram also shows the calculation for cell ranking. Note that the parameter Qoffsets,n is cell-specific for any cell listed in a neighbour list and the parameter Qoffsetfrequency is layer-specific. Together these parameters allow the evaluation of Qoffset to be different for each listed neighbour cell.

Further Reading: 3GPP TS 36.304; 5.2.3.2, 5.2.4.6

Criterion 1 and Criterion S

SServingCell and SnonServingCell are calculated as Srxlev

where:

Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) – Pcompensation

and where:

Pcompensation = max(PEMAX_H – PPowerClass, 0)

and where:

Qrxlevmeas= measured cell DL signal level in dBm

Qrxlevmin = minimum required cell DL signal level in dBm

Qrxlevminoffset = offset for Qrxlevmin in dB (0 for normal cell reselection)

PEMAX_H= max permitted UL TX power in the cell in dBm

PPowerClass = max UE TX power in dBm (from power class)

Ranking Criterion

Rs = Qmeas,s + QHyst

Rn = Qmeas,n – Qoffset

where:

Qmeas = measured cell DL signal level in dBm

Qoffset intra-freq = Qoffsets,n

inter-freq = Qoffsets,n + Qoffsetfrequency



Parameters for Cell Reselection

The table shows details for all the key parameters that are used for cell reselection under normal conditions. Note that although Qrxlevmin is nominally the same parameter as used for cell selection, in that case it would have been sourced from SystemInformationBlockType1 and it may have a different value here.

Further Reading: 3GPP TS 36.304; 5.2.4.7, TS 36.331; 6.3.1, 6.3.2

Parameter Source Unit

Layer Priority per Freq/RAT – SIB Type 3, 5, 6, 7, 8 -

TreselectionRAT per Freq/RAT – SIB Type 3, 5, 6, 7, 8 Seconds

Qoffsets,n per Cell– SIB Type 4, 5, 6, 7, 8 dB

Qoffsetfrequency per Freq/RAT– SIB Type 5, 6, 7, 8 dB

QHyst SIB Type 3 dB

Information element value = –70...–22Working value = IE value x 2 = –140...–44

Information element value = –60...–13Working value = (IE value x 2) + 1 = –119...–25

Information element value = 0...45Working value = (IE value x 2) – 115 = –115...–25

Srxlev taken as –floor(–2 x 10Log10Ec/Io)NB. To give units of 0.5

LTE Equivalent to P-Max = –30...33 dBm

UMTS Equivalent to P-MaxUTRA = –50...33 dBm

GSM Equivalent to P-MaxGREAN = 0...39 dBm

Qmeas Physical layer measurement (RSRP) dBm -

dB

PEMAX_H per Freq/RAT– SIB Type 3, 5, 6, 7

1x/1xEV dB

dBm

UMTS dBm

GSM dBm

–24, –22, –20...–2, 0, 2...18, 20, 22, 24

–24, –22, –20...–2, 0, 2...18, 20, 22, 24

0, 1, 2, 3...6, 8, 10, 12...22, 24

Qrxlevmin per Freq/RAT– SIB Type 3, 5, 6, 7

LTE

1x/1xEV

Threshserving,low SIB Type 3 Information element value = 0...31Working value = IE value x 2 = 0...62 dB

dB

Threshx,low per Freq/RAT– SIB Type 5, 6, 7, 8 Information element value = 0...31Working value = IE value x 2 = 0...62 dB

0...7

Threshx,high per Freq/RAT– SIB Type 5, 6, 7, 8 Information element value = 0...31Working value = IE value x 2 = 0...62

Value

0...7

Srxlev taken as –floor(–2 x 10Log10Ec/Io)NB. To give units of 0.5



Mobility States

Optionally, mobility state information may be sent to the UE in SIB Type 3. If this information is received then the UE will assess its current mobility state, as shown in the diagram. The mobility state is then used to determine scaling factors that may be applied during assessment for cell reselection.


NCR_M, NCR_H, TCRmax, TCRmaxHystSIB Type 3

Normal Mobility if:

Number of reselections in M_RCNsdnocesxamRCT

Medium Mobility if:

Number of reselections in

High Mobility if:

Number of reselections in TCRmax seconds > NCR_H

Return to Normal mobility state if not Medium and not High for TCRmaxHyst seconds

NCR_M 1...16

NCR_H 1...16

TCRmax 30, 60, 120, 240 (seconds)

TCRmaxHyst 30, 60, 120, 240 (seconds)

H_RCNdnaM_RCN>sdnocesxamRCT



Scaling Rules for Mobility States

Once the UE has determined its mobility state it will apply scaling rules, as shown in the diagram. For Normal mobility no action is required over the standard reselection evaluation process. For medium and high mobility states scaling is applied.

When considering intra-frequency or inter-frequency LTE neighbours and IRAT neighbours in the medium or high mobility states, the UE will add the indicated speed-dependent scaling factor to the QHyst value used in the ranking process. In addition, it will multiply the RAT-specific TreselectionRAT timer value by the RAT-specific speed dependent scaling factor.

It is up to the operator to determine how speed-dependent scaling should affect the reselection process. However, the general effect is to negate the normal preference for higher priority frequency or technology cell layers. Use of the speed-dependent scaling factors will tend to make the current selected cell less prominent in the ranking process and will reduce the amount of time required for an equal or lower priority cell to maintain a relative reselection condition.

Further Reading: 3GPP TS 36.304; 5.2.4.3.1, TS 36.331; 6.3.1, 6.3.2

Normal Mobility

Medium Mobility

High Mobility Add q-HystSF-High to QHyst Multiply TreselectionRAT by TreselectionRAT-SF-High

Add q-HystSF-Medium to QHyst Multiply TreselectionRAT by TreselectionRAT-SF-Medium

No action

Mobility State Speed Dependent Scaling Factor Range Source

Normal - - -

q-HystSF-Medium –6, –4, –2, 0 (dB) SIB Type 3

per Freq/RATSIB Type 3, 5, 6, 7, 8

q-HystSF-High –6, –4, –2, 0 (dB) SIB Type 3

per Freq/RATSIB Type 3, 5, 6, 7, 8

Medium 0.25, 0.5, 0.75, 1

High TreselectionRAT-SF-High 0.25, 0.5, 0.75, 1

TreselectionRAT-SF-Medium



LTE Neighbour Lists in UMTS

Neighbour list information for UMTS UEs in idle mode is provided in SIBs within System Information messages. Most neighbour cell information is carried in SIB Type 11, although for some operators this may be supplemented with SIB Types 11bis and 12. However, LTE information is carried separately in SIB 19.

Although the term ‘neighbour list’ is used here, in fact specific neighbour cells are not listed for LTE reselection from UMTS. Instead, SIB 19 carries a parameter called E-UTRA Frequency and Priority List. This simply lists one or more (up to eight) LTE frequency layers. Each frequency layer entry contains a priority for the layer, the required set of LTE layer-specific reselection parameters and, optionally, a black-cell list.

Additionally, it is possible to provide redirection information relating to LTE cells. If used, this is carried in either the RRC Connection Release or Reject messages.

Further Reading: 3GPP TS 25.331; 8.1.1.6.19, 8.6.7.3c, 10.2.48.8.22, 10.3.7.115

Selected cell(UMTS FDD)

UMTS intra-freq

UMTS inter-freq

GSM LTE

Sys Info SIB Type 11

Sys Info SIB Type 19

UMTSintra-freq

UMTSinter-freq

Freq 1...Freq n

PriorityReselection parametersBlack-cell list

I-RAT(GSM)

I-RAT(LTE)



UMTS Measurement Rules without Absolute Priorities

There are several options for the way in which cell reselection is managed in UMTS. The mechanism used will depend on the architecture of the network and on operator preferences. One key feature is the option to implement cell reselection with or without HCS rules. Most UMTS networks are operated ‘without’ HCS rules and the measurement rules are described here in this context. Secondly, the operator may or may not provide absolute priorities for different frequency and technology layers. This page outlines the rules for measurement when priorities are not provided. It is possible to limit the amount of neighbour cell measurement performed by the UE in conditions when the service from the current serving cell is adequate. This is controlled by setting five basic parameters: Sintrasearch, Sintersearch, SsearchRATm, SsearchHCS and SHCS,RATm. These parameters are applied by the UE as shown in diagram. These are optional parameters and if they are not included in system information the UE will simply perform measurements on all indicated neighbour cells irrespective of the condition of the serving cell.

The crucial parameters that impact cell reselection from UMTS to LTE are SsearchRATm and SHCS,RATm. If present, these parameters determine whether or not the UE takes measurements of LTE n-cells. Note that these parameters are set per RAT, so SIB 3 will contain two copies of each, one pair for reselection to LTE and the other pair for reselection to GSM.

Further Reading: 3GPP TS 25.304; 5.2.6.1.1, 25.331; 10.2.48.8.6, 10.3.2.3

Selected cell(UMTS FDD)

Sys Info SIB Type 3

Qqualmeas(-25 to 0)

CalculateSqual

(1 to 25)

Compare

Where:

Squal = Qqualmeas – Qqualmin

Srxlev = Qrxlevmeas – Qrxlevmin – Pcompensation

and

Pcompensation = max(UE_TXPWR_MAX_RACH – P_MAX, 0)

mTAR,SCHSvelxrSromTARhcraesSlauqS:fistnemerusaemTAR-retnimrofreP

SCHhcraesSvelxrSrohcraesretniSlauqS:fistnemerusaemycneuqerf-retnimrofreP

hcraesartniSlauqS:fistnemerusaemycneuqerf-artnimrofreP

Parameter Value

Sintrasearch –32 to 20 in steps of 2 1.

Sintersearch –32 to 20 in steps of 21.

SsearchHCS –105 to 91 in steps of 21.

SsearchRATm2. –32 to 20 in steps of 21.

SHCS,RATm2. –105 to 91 in steps of 21.

Qqualmin Ec/No (dB) –25 to 0 in steps of 1

Qrxlevmin RSCP (dBm) –115 to –25 in steps of 2

1. Negative values are considered to be 0

2. Parameter defined per RAT



UMTS Measurement Rules with Absolute Priorities

If the operator does provide absolute priority values for frequency and technology layers then the measurement rules are modified such that they are similar to those used in LTE.

The diagram outlines the rules as they would be applied for measurements of an LTE frequency layer.

The measurement rules are used to limit unnecessary measurement activity for the UE. They are summarized in the diagram, but in general they ensure that the UE will tend to measure cells in a higher priority layers unless the quality of the currently selected layer becomes unacceptably poor.

Note that the parameters Sintrasearch and Snonintrasearch are optional. If they are not included in SIB Type 3 then the UE will measure all indicated frequency and technology layers and the measurement rules have no effect.

Further Reading: 3GPP TS 25.304; 5.2.6.1.2a

UE must measure

Lower priority layer

UE may not measure

UE must measure

Inter-RAT LTE Measurements

SrxqualServingCell = SrxqualSprioritysearch1 = 0...62 dB in steps of 2 (in SIB Type 19)Sprioritysearch2 = 0...7 dB in steps of 1 (in SIB Type 19)


IfSrxlevServingCell > Sprioritysearch1

andSrxqualServingCell > Sprioritysearch2

Selected cell

UMTS FDD

LTE

2hcraesytiroirpSlleCgnivreSlauqxrSro

1hcraesytiroirpSlleCgnivreSvelxrSfI

SrxlevServingCell = Srxlev



UMTS Reselection Criteria without Absolute Priorities

The UE tests all measured cells, including the current serving cell against the cell selection criterion. All those cells that meet the cell selection criterion are then ranked using the cell-ranking criteria ‘R’. A new cell will be reselected if it is ranked higher than the current cell for a time interval defined by the parameter Treselection, and if the UE has been camped on the current serving cell for more than one second.

Further Reading: 3GPP TS 25.304; 5.2.6.1.4, TS 25.331;10.3.48.8.6, 10.2.48.8.14

Parameter Source Value

Squal

Srxlev

Rs

Rn

Qmeas,s

Qmeas,n

Qhysts SIB 3 0...40 dB is steps of 2

Qoffsets,n SIB 11 –50...50 dB

0...31 secondsSubject to a IRAT Scaling Factor (SF) and a High Mobility state scaling factor

IRAT SF SIB 3 0...4.75 in steps of 0.25

High Mobility SF SIB 3 0...1 in steps of 0.1

Not applicable for LTE cells

Calculated using values in SIB 19

Calculated ranking value for the serving cell

Treselection SIB 3

Calculated ranking value for a neighbour cell

can be set as either Qqualmeas or Qrxlevmeas

RSRP for LTE

it is ranked higher than the serving cell for a time greater than Treselection

the UE has been camped on the current serving cell for at least one second

Rs = Qmeas,s + QhystsRn = Qmeas,n + Qoffsets,n

Cells meeting the ‘S’ criterion are ranked using the ranking criterion ‘R’

Squal > 0 and Srxlev > 0

where:

Squal = Qqualmeas – Qqualmin

Srxlev = Qrxlevmeas – Qrxlevmin – Pcompensation

UE applies cell selection criterion ‘S’

Neighbour Cell Measurements(Based on measurement rules without absolute priorities)

A neighbour cell is reselected if:



UMTS Reselection Criteria with Absolute Priorities

If the operator does provide absolute priority values for frequency and technology layers then the reselection criteria are modified such that they are similar to those used in LTE. Note that LTE cells could never be in an equal priority layer because the operator cannot allocate equal priorities to different technology layers.

The parameters relevant to LTE layers (Threshx,high, Threshx,low and Qrxlevmin for calculating SrxlevnonServingCell,x) are carried in SIB Type 19.

Further Reading: 3GPP TS 25.304; 5.2.6.1.4a

Criteria 1:SrxlevnonServingCell,x (Srxlev) > Threshx,high for TreselectionRAT



Criteria 2:SrxlevServingCell,x (Srxlev) < Threshserving,low for TreselectionRAT

orSqualServingCell,x (Srxlev) < 0 for TreselectionRAT

andLower priority n-cell SrxlevnonServingCell,x (Srxlev) > Threshx,low for TreselectionRAT


Equal Priority N-Cells(Never applies to LTE neighbours)

Lower Priority N-CellsCriteria 3:

SrxlevServingCell,x (Srxlev) < Threshserving,low for TreselectionRAT

orSqualServingCell,x (Srxlev) < 0 for TreselectionRAT

andLower priority n-cell SrxlevnonServingCell,x (Srxlev) > Threshx,low for TreselectionRAT




LTE Neighbour Lists in GSM/GPRS

Neighbour list information for GSM MSs in idle mode is provided in System Information Type 2quater messages. This message contains the frequency list, neighbour cells list, applicable measurement and reporting parameters (for use in dedicated mode or for GPRS) and reselection parameters for UMTS and for LTE as required. Since the message size is restricted and there may be a substantial amount of information required, the complete information may be transmitted of several instances of the SI Type 2quater message. This is facilitated through the use of Start and Stop bits that indicated whether a particular message contains the beginning, end or neither of the complete set of IRAT information.

The key parameters for reselections are shown in the diagram. Note that the parameters include a layer priority for LTE. This is because it is mandatory to use reselection based on priority levels if reselection to LTE is required.

Further Reading: 3GPP TS 44.018; 9.1.34a, 10.5.2.33b

Reselectionparameters

Sys Info Type 2quater Selected Cell UMTS LTE

GERAN_PRIORITYTHRESH_Priority_SearchT_reselectionH_PRIOTHRESH_GSM_low

E-UTRAN Neighbour CellsEARFCNMeasurement BandwidthE-UTRAN_PRIORITYTHRESH_E-UTRAN_highTHRESH_E-UTRAN_lowE-UTRAN_RXLEVMIN

E-UTRAN Not Allowed CellsE-UTRAN PCID to TA Mapping

Selected cell(GSM/GPRS)

UMTS LTE

MS Calculates:

S_GSM = C1

S_non-serving_E-UTRAN = RSRP – E-UTRAN_QRXLEVMIN



GSM Measurement Rules with Priorities

It is mandatory for the operator to implement measurement rules with priority if reselection to an LTE frequency layer is required. The measurement rules are used to limit unnecessary measurement activity for the MS.

Note that once implemented for use with LTE, these rules will also apply to measurements of UMTS frequency layers. Note also that if the value 15 is used for THRESH_Priority_Search then the MS will always measure LTE and UMTS frequency layers.


MS must measure at least once every 60 x Nhpf seconds

Lower priority layer

UE may not measure

MS must measure

Inter-RAT LTE Measurements


hcraeS_ytiroirP_HSERHTC_ALRfI

Selected cell

GSM/GPRSLTE

If RLA_C < THRESH_Priority_Search

sreyalycneuqerfTARIytiroirprehgihforebmuneht=fphN)=51eulav(4fospetsniBd65–...89–=hcraeS_ytiroirP_HSERHT

ISSR=C_ALR



GSM Reselection Criteria with Priorities

The only option for reselection to LTE from GSM is with priority levels. The diagram shows the criteria for reselection. Note that an LTE frequency layer must be a different priority than the selected GSM layer.


S_non-serving_E-UTRAN > THRESH_E-UTRAN_high for T_reselection


Lower Priority N-CellsS_GSM < THRESH_GSM_low for T_reselection

andS_non-serving_E-UTRAN > THRESH_E-UTRAN_low for T_reselection

andS-GSM < C1 for all other measured GSM cells for T_reselection

else ifS_non-serving_E-UTRAN > S-GSM by H_PRIO for T_reselection

andS-GSM < C1 for all other measured GSM cells for T_reselection

Parameter Value

T_reselection 5, 10, 15, 20 seconds

H_PRIO )=0eulav(Bd5,4,3

THRESH_GSM_low )=51eulav(2fospetsBd82...0

THRESH_E-UTRAN_high 0...62 dB steps of 2

THRESH_E-UTRAN_low 0...62 dB steps of 2

E-UTRAN_RXLEVMIN –140...–78 dB steps of 2

CONNECTED MODE PARAMETERS



SECTION 5



CONTENTS

Connected Mode Parameters


RRC Inter-RAT State Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.1

Measurement Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.2

Measurement Configuration Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.3

Measurement Object Definition for LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.4

Measurement Object Definition for Inter-RAT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.5

Measurement and Object Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.6

Measurement Gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.7

Configuration of LTE Reporting Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.8

Event Triggers Relating to LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.9

Configuration of Inter-RAT Reporting Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.10

Event Triggers Relating to Inter-RAT Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.11

Behaviour at Event Trigger Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.12

Measurement Report Format – LTE/UMTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.13

Measurement Report Format – GSM/CDMA2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.14

Intra-LTE Handover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.15

Handover from LTE (IRAT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.16

UMTS Measurement Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.17

LTE Measurement Objects and Reporting in UMTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.18

UMTS Inter-RAT Event Triggers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.19

UMTS Inter-RAT Event Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.20

UMTS Measurement Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.21

UMTS Handover to LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.22

GSM/GPRS Measurement Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.23

Key GSM to LTE Measurement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.24

GSM/GPRS Measurement Reporting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.25

GPRS Packet Handover to LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.26

Uplink Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.27

Timing Advance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.28

CQI Reporting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.29

CQI Reporting Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.30

Management of DRX for Connected Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.31




OBJECTIVES



■ define connected mode for LTE and identify the activities performed by the UE in this mode

■ identify the potential transitions between LTE connected mode and data transfer modes in

other radio access technologies

■ describe the measurement configuration and neighbour cell parameters for LTE

■ define each measurement configuration and neighbour cell parameter in terms of function

setting range and distribution mechanism

■ explain the options for determining reporting and how this can be modified for different radio

access technologies and for mobility

■ explain how the handover process is n=managed between LTE cells and from LTE cells to

inter-RAT cells

■ describe how a UMTS UE can be configured to measure and report on LTE cells

■ explain the handover process between UMTS and LTE

■ describe how a GSM/GPRS MS can be configured to measure and report on LTE cells

■ explain the handover process between GSM/GPRS and LTE

■ outline the parameters that facilitate power control and timing advance adjustment in LTE

connected mode

■ outline the parameters that facilitate CQI reporting in LTE connected mode





RRC Inter-RAT State Transitions

Both Inter-RAT (Inter-Radio Access Technology) handover and cell reselection are defined for LTE, which means that defined state transitions must also be defined for interworking to the radio resource control states in other technologies.

The diagram shows the state transitions for UMTS and GSM/GPRS.

RRC LTE idle mode transition for both UMTS and GSM/GPRS are primarily by reselection. However, for GPRS operation an option for CCO (Cell Change Order) also exists.

The UMTS RRC connected state has a number of substates that are not a feature of LTE. Therefore state transition between the two systems in the RRC connected state varies dependent on traffic activity and direction. Handover is supported both to and from the UMTS CELL_DCH state from the LTE RRC connected state irrespective of packet activity. However, in the reverse direction a UE in the UMTS RRC connected state but that is in the substate CELL_PCH or URA_PCH would return to LTE through cell reselection.

Similarly, transitions for RRC connected UEs to and from GSM/GPRS are also effected by the traffic or signalling activity. Real-time traffic is most likely to be handed over between LTE and GSM, but for GPRS operation options for CCO or CCO with optional NACC (Network Assisted Cell Change) exist.



release

IDLE RRC IDLE

CELL_DCH

CELL_FACH

CELL_PCHURA_PCH

RRC CONNECTED

GSM Dedicated

GSM_Idle/ GPRS Packet_Idle

GPRS Packet transfer mode

UMTS LTE GSM/GPRS

Reselection


release

Handover

Reselection

CCO, reselection


release

RRC CONNECTED



Measurement Configuration

The RRCConnectionReconfiguration message is used to set up, modify or remove measurements to be made by UEs. In principle the measurement and reporting process is similar to that used in UMTS. The UE is instructed in some detail what it should measure, when it should measure it, how it should interpret the results and under what circumstances it should report measurement results to the eNB. Measurement reporting can be configured as either periodical or event-based.

Note that the RRCConnectionReconfiguration message is a general purpose message and when used for a specific function only the relevant information elements will be present. In this case the key information element is measConfig.

Further Reading: 3GPP TS 36.331; 5.3.5, 5.5

MeasurementReportDCCH/UL-SCH

RRCConnectionReconfigurationCompleteDCCH/UL-SCH

RRCConnectionReconfigurationDCCH/DL-SCH

Measurement processes started

Periodical or event-based reporting set

Report triggered

measConfig Intra- and inter-frequency and inter-RAT measurement configuration

mobilityControlInfo Target cell configuration and H/O parameters

dedicatedInfoNASList Encapsulated NAS message

radioResourceConfigDedicated SRB or DRB add, modify or remove

securityConfigHO Information regarding security settings to be used after H/O

nonCriticalExtensions-v9x0 Layer-specific reselection parameters

RRCConnectionReconfiguration message



Measurement Configuration Settings

The measConfig information element is itself made up from four key information element sets: measurement objects, reporting configurations, measurement identities and other parameters. Measurement objects identify that which is to be measured. Measurement objects are defined in terms of a RAT/frequency layer within which cells may be specified. Each defined measurement object is tagged with a measurement ID.

Reporting configurations identify the trigger for reporting defined measurements. The measurements defined depend on the RAT being described, for example for LTE this would be RSRP or RSRQ, or for UMTS this would be RSCP or Ec/No. Reporting can be set as either periodical or event based and this setting will be accompanied by details of appropriate events, thresholds and timers. Each defined reporting configuration is tagged with a report configuration ID.

Measurement identities link defined measurement objects to defined reporting configurations and it identifies each defined combination with a specific measurement identity.

The set of other parameters represents those things that are common to all measurements. This includes the measurement filter coefficient (default setting = 4), measurement gap start position configuration (for inter-frequency or inter-RAT measurements), the serving cell quality threshold (to trigger intra- or inter-frequency or inter-RAT measurements) and factors for speed-dependent scaling. There may also be information regarding preregistration on 1xEV-DO (HRPD) if required for potential handover to the 1xEV-DO system.

Further Reading: 3GPP TS 36.331; 5.5.2, 6.2.2, 6.3.5

measConfig Intra- and inter-frequency and inter-RAT measurement configuration

mobilityControlInfo Target cell configuration and H/O parameters

dedicatedInfoNASList Encapsulated NAS message

radioResourceConfigDedicated SRB or DRB add, modify or remove

securityConfigHO Information regarding security settings to be used after H/O

nonCriticalExtensions-v9x0 Layer-specific reselection parameters

RRCConnectionReconfiguration message

List as required

List as required 1...n (max = 32)

List as required

List as required 1...n (max = 32) reportConfigRAT

List as required

List as required 1...n (max = 32) measObjectId reportConfigId

Measurement filter coefficients by type and RAT

0, 1, 2, 3, 4, 5, 6, 7, 8, 9,11, 13, 15, 17, 19

gp1 0...39gp2 0...39

0...97(–140...–44 dBm)

... ...

sf-High 0.25, 0.5, 0.75, 1.0

n-CellChangeMedium 1...16 n-CellChangeHigh 1...16

speedStateScaleFactors sf-Medium 0.25, 0.5, 0.75, 1.0

preRegistrationInfoHRPD speedStateParameters

t-Evaluation 30, 60, 120, 240 seconds t-HystNormal 30, 60, 120, 240 seconds

Other Parameters

qualityConfig

measGapConfig

s-Measure Serving cell quality threshold

reportConfigId Event/periodical + details

Measurement Identities measIdToRemoveList measIdToAddModList

measId

measObjectId measObject LTE, UMTS, GSM or CDMA2000 layers

Reporting Configurations reportConfigToRemoveList reportConfigToAddModList

measConfig Measurement Objects

measObjectToRemoveList measObjectId

measObjectToAddModList



Measurement Object Definition for LTE

The diagram shows the parameters that are used to define the measurement object in the case that the measurements are to be made on LTE cells.

Note that the cellsToAddModList is optional and it is possible to specify the measurement object only as a frequency layer. In this case the black-cell list may still be used to exclude cells from the measurement process.


List as required


Other Parameters Measurement Identities


Reporting Configurations




EARFCN

6, 15, 25, 50, 75, 100 RBs

True/False (MIMO setting)

MBSFN or TDD related info

–24...24 dB (Qoffsetfrequency)

Cell indices as required (max = 32)

1...n (max = 32)

0...503 (PCI)

–24...24 dB (Qoffsets,n)


start 0...503 (PCI)

range 1, 4, 8, 12, 16, 24, 32, 48, 64, 84, 96, 128, 168, 252, 504

0...503 (PCI)

physicalCellIdRange

cellForWhichToReportCGI

Example: measObjectEUTRA

carrierFreq

allowedmeasBandwidth

presenceAntennaPort1

neighCellConfig

offsetFreq

cellsToRemoveList

cellsToAddModList

cellIndividualOffset

blackCellsToRemoveList

blackCellsToAddModList

cellIndex

cellIndex

physicalCellId

1...n (max = 32)

measObject LTE, UMTS, GSM or CDMA2000 layers



Measurement Object Definition for Inter-RAT

The diagram shows the parameters that are used to define the measurement object in the case that the measurements are to be made on either UMTS cells or on GSM cells.

Note that for GSM it is only possible to specify ARFCNs. BSICs are not specified explicitly, but it is possible to restrict the allowed values for the NCC part of the BSIC.


List as required


Other Parameters Measurement Identities


Reporting Configurations




1...n (max = 32)

Example: measObjectUTRA

carrierFreq

cellIndex

physicalCellId

UARFCN

–15...15 dB (eval of meas req)


Either FDD or TDD

FDD 0...511

TDD 0...127

FDD 0...511

TDD 0...127 cellForWhichToReportCGI

offsetFreq

cellsToRemoveList

cellsToAddModList

measObject LTE, UMTS, GSM or CDMA2000 layers

UARFCN

ARFCN

1800/1900

CHOICE

Listed ARFCNs (max = 32)

arfcn-Spacing 1...8

numberOfFollowingARFCNs 0...31

1...16 octets

–15...15 dB (eval of meas req)

True/False 8-bit bitmap

BSIC (NCC+BCC)

offsetFreq

ncc-Permitted

cellForWhichToReportCGI

Example: measObjectGERAN

carrierFreqs

startingARFCN

bandIndicator

followingARFCNs

explicitListOfARFCNs

equallySpacedARFCNs

variableBitMapOfARFCNs



Measurement and Object Summary

Measurement objects must be defined for the UE to take measurements, but the definition of a measurement object varies slightly dependent on the RAT involved. Measurement object requirements are summarized in the table.

The measurement configuration information element also contains the parameter s-Measure expressed as RSRP. This forms the basis of a measurement rule such that neighbour cell measurements are only made when the measured quality of the serving cell is below s-Measure.

Measured neighbour cells may be those that are explicitly identified in the measurement object information element, in which case they are referred to as ‘listed’ cells, or they may be cells that the UE has detected on a specified frequency/RAT layer, in which case they are referred to as ‘discovered’ cells.

Further Reading: 3GPP TS 36.331; 5.5.1, 5.5.3.1

s-MeasureServing Cell

Discovered Cell

Listed CellN-cell measurements

Measurement Object

Frequency Listed Cells Listed Black Cells

Listed

LTE Intra-Freq Yes - One Optional Optional

LTE Inter-Freq Yes - One Optional Optional

UMTS Yes - One Yes No

GSM Yes - Set No No

CDMA2000 Yes - One Yes No



Measurement Gaps

When the UE is in RRC connected mode it will be engaged in data transfer in the uplink or downlink directions, or both. In order to simplify the design of the UE it is not required to be able to take neighbour cell measurements and transfer data with the serving cell at the same time. This requires defined periods where the UE is able to take neighbour cell measurements and is not required to communicate with the serving cell.

Transmission gaps perform this function and are very similar in concept to compressed mode for UMTS. The transmission gaps have a duration of 6 ms since this allows sufficient time to take measurements and gain basic synchronization with most RATs in a single transmission gap. For GSM, however, 6 ms remains a sufficient gap, but multiple transmission gaps are required to take measurements and determine a cell’s BSIC.

The transmission gap period is variable, but will be a multiple of 10 ms.

The transmission gap pattern to be used by a UE is included in the measurement parameters.

Further Reading: 3GPP TS 36.133:8.1

Start position defined by the measGapConfig parameter

MGL (Measurement Gap Length)

MGRP(Measurement Gap Repetition Period)

Neighbour cell Neighbour cell Neighbour cell

eNBServing cell

MGRP (ms)

MGL (ms)Gap Pattern ID

01

66

4080



Configuration of LTE Reporting Criteria

The diagram shows the parameters that are used to define the reporting criteria for measurements made on LTE cells. The criteria may be either event or periodical. In the case of event-based reporting one or more events can be defined, each with appropriate details including the threshold, the hysteresis value and the time-to-trigger value. Note that these are set individually for each event defined.

Events can be based on a measurement of either RSRP or RSRQ, but is also possible to request that any consequent report contains both RSRP and RSRQ irrespective of the trigger measurement.

Note that a combination of periodical and event-based reporting can be set up by including multiple report configurations in the report configurations list.


List as required


Other Parameters


Measurement Identities



reportConfigRAT Event/periodical + details

CHOICE

List of event triggers required

eventId Event A1, A2, A3, A4, A5

hyteresis 0...30 value = IE x 0.5 dB

timeToTrigger 0, 40, 64, 80, 100, 128, 160, 256, 320, 480, 512, 640, 1024, 1280, 2560, 5120 milliseconds

purpose Report strongest cells/report CGI

RSRP/RSRQ

Same as trigger quantity/both

1...8

120, 240, 480, 640, 1024, 2048, 5120, 10240 milliseconds, 1, 6, 12, 30, 60 minutes

1, 2, 4, 8, 16, 32, 64, infinity

...

reportInterval

reportAmount

reportConfigEUTRA-v9x0

Example: reportConfigEUTRA

triggerType

event

periodical

triggerQuantity

reportQuantity

maxReportCells

eventId Event A1, A2, A3, A4, A5

CHOICEthreshold-RSRP 0...97 (maps to –140...–44 dBm)threshold-RSRQ 0...34 (maps to –19.5...–3 dB)


–30...30 True/false




eventA5 a5-Threshold1

a5-Threshold2

eventA4

eventA2

a3-Offset reportOnLeave

a4-Threshold

eventId eventA1

a1-Threshold

a2-Threshold

eventA3



Event Triggers Relating to LTE

The event triggers defined for LTE are as follows:

■ Event A1 – The serving cell becomes better than absolute threshold

■ Event A2 – The serving cell becomes worse than absolute threshold

■ Event A3 – A neighbour cell becomes better than an offset relative to the serving cell

■ Event A4 – A neighbour cell becomes better than absolute threshold

■ Event A5 – The serving cell becomes worse than absolute threshold1 and a neighbour cell becomes better than absolute threshold2

Each event will have an associated hysteresis value and time-to-trigger value. These can be used to provide a damping or filtering effect to cover short-term variation in the measured value.


Absolute threshold

Serving cell

Event A1

LTE Event Triggers

Absolute threshold

Serving cell

Event A2

Offset

Serving cell

Event A3Neighbour cell

Absolute threshold


Serving cell


Absolute threshold1

Absolute threshold2



Configuration of Inter-RAT Reporting Criteria

The diagram shows the parameters that are used to define the reporting criteria for measurements made on Inter-RAT cells, which may be either UMTS, GSM or CDMA2000. The criteria may be either event or periodical. In the case of event-based reporting two events can be defined, each with appropriate details including the threshold, the hysteresis value and the time-to-trigger value.

Measurements made on Inter-RAT signals are appropriate to the RAT concerned. In the case of Event B2 this is combined with an LTE measurement.


List as required


Other Parameters


Measurement Identities



reportConfigRAT Event/periodical + details

CHOICE

List of event triggers required

eventId Event B1, B2,

hysteresis 0...30 value = IE x 0.5 dB

timeToTrigger 0, 40, 64, 80, 100, 128, 160, 256, 320, 480, 512, 640, 1024, 1280, 2560, 5120 milliseconds

purpose Report strongest cells/report strongest cells for SON/report CGI

1...8

120, 240, 480, 640, 1024, 2048, 5120, 10240 milliseconds, 1, 6, 12, 30, 60 minutes

1, 2, 4, 8, 16, 32, 64, infinity

...

reportInterval

reportAmount

reportConfigInterRAT-v9x0

Example: reportConfigInterRAT

triggerType

event

periodical

maxReportCells

eventId Event B1, B2,

CHOICE

eventId eventB1

b1-Threshold CHOICE

utra-RSCP –5...91 (maps to –120...–25dBm)utra-EcN0 0...49 (maps to –24...0dB)

0...63 (maps to –110...–47 dBm)0...63

CHOICE0...97 (maps to –140...–44 dBm)0...34 (maps to –19.5...–3 dB)CHOICECHOICE

utra-RSCP –5...91 (maps to –120...–25 dBm)utra-EcN0 0...49 (maps to –24...0 dB)

0...63 (maps to –110...–47 dBm)0...63

b2-thresholdGERAN b2-thresholdCDMA2000

eventB2 b2-Threshold1

threshold-RSRP threshold-RSRQ

b2-Threshold2 b2-thresholdUTRA

b1-thresholdUTRA

b1-thresholdGERAN b1-thresholdCDMA2000



Event Triggers Relating to Inter-RAT Measurements

There are also two more event triggers for inter-RAT mobility:

■ Event B1 – An inter-RAT neighbour cell becomes better than an absolute threshold

■ Event B2 – The LTE serving cell becomes worse than absolute threshold1 and an inter-RAT neighbour cell becomes better than absolute threshold2

Events can be modified with time-to-trigger values and hysteresis values if required.


Absolute threshold

Event B1Inter-RAT

neighbour cell

Inter-RAT Event Triggers

LTE Serving cell

Event B2

Absolute threshold1

Absolute threshold2

Inter-RATneighbour cell



Behaviour at Event Trigger Points

In addition to the event thresholds, the measurement configuration includes values for time-to-trigger and hysteresis. These are specified individually for each event used. As shown in the diagram they can be used independently or together.

Additionally, a speed state scaling parameter can also be provided. The assessment of speed state is performed exactly as specified for idle mode except that the UE counts successive handovers instead of reselections. Once the speed state is determined then the scaling factor is applied to the Time-to-trigger value, as shown.


Hysteresis value

Hysteresis

Nominaltrigger

condition

Reporttriggered

here

ttt value

Hysteresis condition met

here

Hystvalue

ttt value

Hysteresis and Time-to-triggerTime-to-trigger (ttt)Hysteresis and Time-to-trigger

Nominaltrigger

condition

Reporttriggered

here Nominaltrigger

condition

Reporttriggered here

Connected Mode Parameter Value Range Idle Mode

equivalent

t-Evaluation 30, 60, 120, 240 seconds TCRmax

t-HystNormal TCRmaxHyst

n-CellChangeMedium 1...16 NCR_M

n-CellChangeHigh 1...16 NCR_H

30, 60, 120, 240 seconds

Normal Mobility

Medium Mobility

High Mobility

No action

Multiply Time-to-trigger by sf-Medium

Multiply Time-to-trigger by sf-High

Speed State Scale Factors



Measurement Report Format – LTE/UMTS

The diagram shows the general format of the MeasurementReport message. Examples of the format for reported LTE neighbours and UMTS neighbours are shown.

The specific contents of the message will vary dependent on trigger type, RAT type and on what the UE was asked to report. For example, the report may contain only the measurement of the trigger value or it may contain all measured quantities. Similarly, the report may or may not contain the cgi-Info information element. This information element is only included if specifically requested for the reported cell. Thus in most cases the message will contain only physical cell identities and measurement results.


1...n (max = 32)

0...97 (maps to –140...–44 dBm)

0...34 (maps to –19.5...–3 dB)

CHOICE

List as required

List as required

List as required

preRegistrationStatusHRPD

measResultListCDMA2000 List as required

UE Tx/Rx Time difference

MeasurementReport message

measId

measResultServingCell

rsrpResult

rsrqResult

measResultNeighCells

measResultListEUTRA

measResultListUTRA

measResults-v9x0

measResultListGERAN

measResultsCDMA2000

List as required measResultListEUTRA

0...503

cellGlobalId MCC + MNC + CID

trackingAreaCode 16 bits

plmn-IdentityList List as required (max = 5)

rsrpResult 0...97 (maps to –140...–44 dBm)

rsrqResult 0...34 (maps to –19.5...–3 dB)

measResult-v9x0 CSG Info

physicalCellId

cgi-Info

measResult

measResultEUTRA

List as required measResultListUTRA

FDD 0...511TDD 0...127


locationAreaCode 16 bits

routingAreaCode 8 bits

plmn-IdentityList List as required (max = 5)

utra-RSCP –5...91 (maps to –120...–25 dBm)

utra-EcN0 0...49 (maps to –24...0 dB)

measResult-v9x0 CSG Info

physicalCellId

cgi-Info

measResult

measResultUTRA



Measurement Report Format – GSM/CDMA2000

The diagram shows the general format of the MeasurementReport message with examples of the format for reported GSM neighbours and CDMA2000 neighbours.


1...n (max = 32)

0...97 (maps to –140...–44 dBm)

0...34 (maps to –19.5...–3 dB)

CHOICE

List as required

List as required

List as required

preRegistrationStatusHRPD

measResultListCDMA2000 List as required

UE Tx/Rx Time difference

MeasurementReport message

measId

measResultServingCell

rsrpResult

rsrqResult

measResultNeighCells

measResultListEUTRA

measResultListUTRA

measResults-v9x0

measResultListGERAN

measResultsCDMA2000

List as required measResultListGERAN

ARFCN

BSIC (0...7 – 0...7)


routingAreaCode 8 bits

rssi 0...63 (maps to –110...–47 dBm)

measResultGERAN

carrierFreq

physicalCellId

cgi-Info

measResult

List as required measResultListCDMA2000

0...511 (Pilot PN-Offset)

cellGlobalId SID/NID+ CID + Sector ID (1xEV only)

pilotPnPhase 0...32767

pilotStrength 0...63

measResultCDMA2000

physicalCellId

cgi-Info

measResult



Intra-LTE Handover

The diagram shows the air interface signalling for an intra-E-UTRA/LTE handover. The handover is triggered after the reception of a MeasurementReport message containing measurements and identity for a valid target cell. Negotiation for resources takes place directly between source and target cell over the X2 interface. A change in S1 interface resource allocation is also required and involves a negotiation between the eNBs and the MME. Once all of this is in place the handover instructions, including a description of the new SRBs and DRBs on the target cell, are transmitted to the UE using an RRCConnectionReconfiguration message.

The UE uses the lower-layer random access procedure to obtain an uplink resource to transmit on the target cel l and a new C-RNTI. The upl ink resource is then used to t ransmit an RRCConnectionReconfigurationComplete message to the target eNB.


SourceeNB

TargeteNB

MeasurementReport

X2 – Handover preparation

RRCConnectionReconfiguration

MAC – random access procedure

RRCConnectionReconfigurationComplete



Handover from LTE (IRAT)

When a measurement report indicates that an IRAT handover is required, the eNB cannot negotiate directly with the target cell. Instead the mobility procedures are handled by interactions via the MME. Once suitable resources are allocated on the target cell, handover information is forwarded to the source eNB, which forwards them to the UE in an RRC MobilityFromEUTRACommand message.

On reception of this message the UE changes RAT mode and implements the new channel as instructed. Handover acceptance and conformation after this point are dependent on the RAT concerned. However, for GSM or UMTS this will involve the transmission of a RR or RRC Handover Complete message.


SourceeNB

TargetRAN

TargetCN nodeMME

MeasurementReport

Handover preparation

MobilityFromEUTRACommand

Handover Complete (or as required for target RAT)



UMTS Measurement Configuration

Measurement configuration in UMTS is achieved primarily through the use of the RRC Measurement Control message. The contents of this message are summarized in the diagram. The message is sent to the UE when in connected mode and is used repeatedly if necessary as measurement requirements change with UE mobility, physical layer channel combination or radio conditions. In many cases multiple Measurement Control messages are required to provide a complete set of measurement and reporting configurations for a UE.

Additionally, UEs having to take inter-frequency or inter-RAT measurements will need a transmission gap configuration for compressed mode operation. This information is provided in an RRC Physical channel Reconfiguration message, which must be sent before the relevant Measurement Control message.

As shown, the most pertinent part of the Measurement Control message for handover to LTE is the information element Inter-RAT measurement type. This information element defines LTE measurement objects, quantities and reporting criteria.


UMTS RRCMeasurement Control message

UTRAN

1...n (max = 16)

Setup/Modify/Release

Measurement Report Transfer Mode AM/UM RLC

Reporting Mode Event/Periodical

CHOICE

Intra-frequency

Inter-frequency

Inter-RAT

UE positioning

Traffic volume

Quality

UE internal

CSG proximity Compressed mode status information

Measurement Control message

Measurement Identity

Measurement Command

Measurement Reporting Mode

Measurement Type

Physical Channel Information Elements

Inter-RAT

CHOICE

N/A for LTE

E-UTRA Frequency Removal All/Some(listed)/None

New Frequencies List as required

RSRP/RSRQ

1, 2...9, 11, 13...19 Measurement Quantity/both

1...12

CHOICE

Periodical Reporting Criteria

Filter Coefficient

Inter-RAT Reporting Quantity

Reporting Cell Status

Max Number of Reported Cells

Report Criteria

Inter-RAT Measurement Reporting Criteria

Inter-RAT Cell Info List

E-UTRA Frequency List

No Reporting

Inter-RAT (for LTE)

Inter-RAT Measurement Objects

Inter-RAT Measurement Quantity

Measurement Quantity



LTE Measurement Objects and Reporting in UMTS

Note that when LTE is specified as a measurement object in UMTS it is specified only in terms of a frequency layer; there are no individual cell IDs. However, the option does exist to specify black-listed cells on the frequency layer if required. The standards allow up to eight LTE frequency layers to be defined.

The reporting criteria may be either periodic or event-based. If event-based then four inter-RAT events are specified that could be applied to LTE; Event 3a, 3b, 3c or 3d. Note that multiple events can be specified in the list, each with individually specified threshold, hysteresis and time-to-trigger values.

Further Reading: 3GPP TS 25.331; 10.3.7.6b, 10.3.7.30, 10.3.7.53

CHOICE

N/A for LTE

E-UTRA Frequency Removal All/Some(listed)/None


RSRP/RSRQ

1, 2...9, 11, 13...19 Measurement Quantity/both

1...12

CHOICE


Filter Coefficient

Inter-RAT Reporting Quantity


Max Number of Reported Cells

Report Criteria


Inter-RAT Cell Info List

E-UTRA Frequency List

No Reporting

Inter-RAT (for LTE)

Inter-RAT Measurement Objects

Inter-RAT Measurement Quantity

Measurement Quantity

List as required

EARFCN

6, 15, 25, 50, 75, 100 RBs

List as required

Physical Cell Id PCI (0...503)

New Frequencies (list as required, max = 8)

E-UTRA Carrier Frequency

Measurement Bandwidth

Blacklisted Cells


e3a, e3b, e3c, e3d

–115...0 dBm (e3a only)

0...2.0 in steps of 0.1 (e3a only)

–115...0 dBm (e3a, b, c only)Value = IE value – 25

0...7.5 in steps of 0.5

0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240, 320, 640, 1280, 2560, 5000 milliseconds

Max Number of Reported Cells 1...12

(list as required, max = 8)

W

Threshold Other System


Time-to-Trigger


Inter-RAT Event Identity

Threshold Own System

Hysteresis

Inter-RAT Measurement Reporting Criteria List as required

Amount of Reporting 1, 2, 4, 8, 16, 32, 64, Infinity

Reporting Interval 250, 500, 1000, 2000, 3000, 4000, 6000, 8000, 12000, 16000, 20000, 24000, 28000, 32000, 64000 milliseconds





UMTS Inter-RAT Event Triggers

The diagram summarizes the four UMTS inter-RAT event triggers, which can be defined as follows:

■ Event 3a – The quality of the UMTS active set becomes worse than an absolute threshold and an inter-RAT LTE neighbour cell becomes better than an absolute threshold

■ Event 3b – An inter-RAT LTE neighbour cell becomes worse than an absolute threshold

■ Event 3c – An inter-RAT LTE neighbour cell becomes better than an absolute threshold

■ Event 3d – Change of best inter-RAT LTE neighbour cell

Since UMTS is a CDMA technology and as a serving system may be making use of an active set of cells, a mechanism is defined (as shown in the diagram) for determining an overall quality measure for the UMTS active set. As can be seen, this is a balance between the sum of active set cell quality measures and the best active set cell quality measure. The balance between these two evaluation approaches is adjusted with the parameter ‘W’.

The precise trigger point associated with each event can be modified with a time-to-trigger value and an hysteresis value.

Further Reading: 3GPP TS 25.331; 14.3, 14.3.1

Absolute threshold

Event 3c Inter-RAT LTEneighbour cell

UMTS active set (QUTRAN)

Event 3a Inter-RAT LTEneighbour cell

Absolute threshold (own)

Absolute threshold (other)

Absolute threshold

Event 3b

Inter-RAT LTEneighbour cell

Event 3dInter-RAT LTEneighbour cell 1

Inter-RAT LTEneighbour cell 2

Changeof best

UMTS Inter-RAT Event Triggers

Note that:

where:

Mi is the quality measure of the ‘i’ th cell in the active setMBest is the quality measure of the best cell in the active setNA is the number of cells in the active setW is a factor that changes the weighting between the sum of all Mi and MBest

QUTRAN?10?LogMUTRAN ? W?10?Log Mi

NA

1i???

????

??

?+(1–W)?10?LogMBest,



UMTS Inter-RAT Event Flow

The diagram shows an example of the events that may take place in order for an IRAT handover to occur successfully.

Since compressed mode is not operated all of the time a trigger must be used to start it. This is likely to be based on something that reflect a reduction in the quality of the serving cell such as reducing RSCP or Ec/No or increasing UE transmit power. However, there are many other possibilities such as UE position or even default operation of compressed mode for UEs with LTE capability. Nevertheless, in this example one or a combination of events e1f or e6a could be reported before compressed mode is started. Once compressed mode is triggered it must be signalled to the UE and this will require at least two consecutive messages (Physical Channel Reconfiguration and Measurement Control). The UE must then configure compressed mode and indicate that it has done so correctly.

Once compressed mode is in operation, the UE will take measurements and generate reports. It is likely to require several periodical reports before the IRAT handover requirements and target cell can be determined. Only at this point can the RNC arrange for resources to be made available on LTE. Once this is complete a handover message can be sent to the UE.

3G CPICH Ec/No or RSCP begin to deteriorate

UE TX Pwr begins to rise

time

Could trigger e6a

Could trigger e1f

IRAT H/O needed

ReportingMoving out of 3G coverage

Decision, settings, signalling

IRAT measurements and reporting

Channel allocation and

signalling

Compressed mode

triggered

Compressed mode active

IRAT H/O triggered

Connection re-established

on LTE

Physical Channel ReconfigurationMeasurement Control

Measurement Reports(Triggered on e3a, e3b, e3c, e3d)

Handover From UTRAN Command



UMTS Measurement Reporting

When the configured trigger conditions are met the UE will send a Measurement Report message. The general contents of this message are shown.

Although the information element Measured Results does include an option for inter-RAT results, its structure was defined in early releases of UMTS. In this context the interpretation of ‘inter-RAT’ includes only GSM, CDMA2000 and other modes of UMTS and thus cannot be used for LTE measurement results. Instead, new information elements have been defined from Release 8 that are used specifically for LTE measurement reporting. The structures of these information elements are shown.

Further Reading: 3GPP TS 25.331; 10.2.19, 10.3.7.6a, 10.3.7.6c

UMTS RRCMeasurement Report message

UTRAN

1...n (max = 16)

N/A for LTE

N/A for LTE

List as required, max = 4

Measured Results N/A for LTE

N/A for LTE

CHOICE

UTRA CSG Frequency Info UARFCN

E-UTRA CSG Frequency Info EARFCN

Additional Measured Results

CSG Proximity Indication

E-UTRA Event Results

Measurement Report message

Measurement Identity

Measured Results

Measured Results on RACH

Event Results

E-UTRA Measured Results

List as required , max = 4

EARFCN


Physical Cell Id PCI 0...503

RSRP 0...97 (maps to –140...–44 dBm)

RSRQ 0...33 (maps to –19.5...–3 dB)


E-UTRA Measured Results List


Measured E-UTRA Cells List

E-UTRA Measured Results e3a, e3b, e3c, e3d


EARFCN


Physical Cell Id PCI 0...503


Inter-RAT Event Identity


E-UTRA Event Results List

Reported Cells List




UMTS Handover to LTE

In most cases the measurement process for the UE will be defined using a Measurement Control message that includes triggers based on intra-frequency measurements. Reporting from this point will be based on the configuration in those messages and can be either periodical or event-based.

When it is determined that an inter-RAT handover to LTE may be required, either as a result of the contents of a measurement report message or as a result of network policy, the UE’s configuration must be modified for inter-RAT measurements. This requires the setting of compressed mode, which is achieved through the use of a Physical Channel Reconfiguration message. LTE measurement objects and, if required, inter-RAT event triggers are then defined in a Measurement Control message.

When the UE reports an LTE cell that is suitable as a handover target according to the network requirements the source UTRAN will request handover channel configuration and resources from the target eNB via source and target core network nodes. Once returned, the handover details are sent to the UE in a Handover From UTRAN Command message.

The UE configures the new access details and attempts to re-establish its connection through the LTE eNB.


SourceRAN

TargeteNB

SourceCN node MME

MeasurementReport

Measurement Control

MeasurementReportCompressed

mode triggeredPhysical Channel Reconfiguration

MeasurementReport

Measurement Control

MeasurementReportHandover

preparationHandover From UTRAN Command





GSM/GPRS Measurement Configuration

In order for a multi-mode MS operating on a GSM or GPRS channel to take measurements of LTE neighbour cells the MEASUREMENT INFORMATION or PACKET MEASUREMENT ORDER message must be used, dependent on operating mode. The contents of these messages have been modified in Release 8 to include LTE information as summarized for the MEASUREMENT INFORMATION message in the diagram. The messages are sent to the MS when in dedicated mode or GPRS transfer mode and may be used repeatedly if required as measurement requirements change. In most cases multiple messages are required to provide a complete set of measurement and reporting configurations for an MS. The successful accumulation of a complete set of measurement data is achieved through the combined use of the 3G_BA_IND information element and the E-UTRAN_Start/Stop information elements.

A very similar set of information can be included in the SYSTEM INFORMATION TYPE 2quater message carried in BCCH. This means that the MS may already have stored measurement information for LTE cells acquired in idle mode and applied as soon as it moves to dedicated mode or GPRS transfer mode. Subsequent reception of the MEASUREMENT INFORMATION message may then replace or supplement this configuration.

Further Reading: 3GPP TS 44.018; 9.1.54, TS 44.060

PACKET MEASUREMENT ORDER message GERAN

MEASUREMENT INFORMATION message

SYSTEM INFORMATION TYPE 2quater

BA_IND 1/03G_BA_IND 1/0 MP_CHANGE_MARK 1/0 MI_INDEX 0...15 MI_COUNT 0...15 PWRC 1/0 REPORT_TYPE 1/0 REPORTING_RATE 1/0

E-UTRAN Parameters Description

Various 2G and 3G reporting parameters

MEASUREMENT INFORMATION message

E-UTRAN_Start 0/1

E-UTRAN_Stop 0/1

E-UTRAN Measurement Parameters Description

Measurement quantity and reporting thresholds

Repeated E-UTRAN Neighbour Cells Frequency list and measurement bandwidth

Repeated E-UTRAN Not Allowed Cells Black cell list or range

E-UTRAN Measurement Control Parameters Description

Default behaviour if no LTE N-cell info present





Key GSM to LTE Measurement Parameters

The diagram shows the main measurement configuration parameters for LTE measurements. This reflects the contents of a MEASUREMENT INFORMATION but similar information may also be transmitted in the SYSTEM INFORMATION TYPE 2quater message.

The parameter Qsearch_C_E-UTRAN can be used as a trigger for the performance of measurements on LTE neighbour cells. As can be seen it may be set as either an upper or lower threshold or it may be set as a an absolute switch. The measurement quantity can be specified as either RSRP or RSRQ, but there is not an option form both. The number of cells included in a measurement report can also be specified.

The remaining parameters all relate to trigger thresholds for the generation of measurement reports. The set used depends on whether 3-bit or 6-bit reporting is requested and this in turn is dependent on whether the standard MEASUREMENT REPORT or the ENHANCED MEASUREMENT REPORT message is to be used for reporting on LTE neighbours. In each set the first and second threshold must be satisfied before a cell is reported and then the third parameter is used as an offset on the reported value. The granularity parameter is applicable only when 3-bit reporting is in use and is required to define the meaning of the reported values.

Note that although there is a parameter called E-UTRAN Neighbour Cell; it only contains a description of LTE as a frequency layer and no specific cell details are included. However, individual sets of cells may be specified as a black-cell list.

Further Reading: 3GPP TS 44.018; 9.1.54, TS 45.008; 8.4.7, 8.4.8

E-UTRAN_Start 0/1

E-UTRAN_Stop 0/1




Repeated E-UTRAN Not Allowed Cells Black cell list or range

E-UTRAN Measurement Control Parameters Description

Default behaviour if no LTE N-cell info present



EARFCN 16 bits

Measurement Bandwidth 3 bits (6, 15, 25, 50, 75, 100)

E-UTRAN Neighbour Cells (List)



0...7 search if below –98, –94...–74, inf (always)8...15 search if above –78, –74...–54 inf (never)

1/0 RSRP/RSRQ

0...3 number of reported cells

E-UTRAN_REPORTING_THRESHOLD 0...7 maps to 0, 6...36, inf (never)

E-UTRAN_REPORTING_THRESHOLD_2 0...63

E-UTRAN_REPORTING_OFFSET 0...7 maps to 0, 6...36, 42

E-UTRAN_MEASUREMENT_REPORT_OFFSET 0...63

E-UTRAN_REPORTING_THRESHOLD_2 0...63

E-UTRAN_REPORTING_OFFSET 0...7 maps to 0, 6...36, 42

1/0 RSRP = 2/3 dB, RSRQ = 1/2 dBREPORTING_GRANULARITY

Qsearch_C_E-UTRAN

E-UTRAN_REP_QUANT

E-UTRAN_MULTIRAT_REPORTING

CHOICE (for 6-bit or 3-bit reporting)



GSM/GPRS Measurement Reporting

LTE neighbour cell measurement results can be sent in either the MEASUREMENT REPORT or the ENHANCED MEASUREMENT REPORT message. Which is to be used is indicated to the MS in downlink signalling.

If the MEASUREMENT REPORT message is used then the standard 12-bit N-CELL information element is modified as shown in the diagram. The LTE Physical cell identity requires 9 bits (value = 0...503), which leaves only 3 bits for the reported value. This is a normal measurement encoded over a defined range and quantized to a defined granularity (value = 0...7 with variable mapping).

The diagram shows a summary of the contents of the ENHANCED MEASUREMENT REPORT message. Note that the serving cell measurement information relates to GPRS operation. The key information element for LTE cells is a list of measurement results at the end of the message.

Further Reading: 3GPP TS 44.018; 9.1.21, 9.1.55, 10.5.2.20

MEASUREMENT REPORT orENHANCED MEASUREMENT REPORT UTRAN

0/10/1 0/1 0/1

DTX_USED 0/1RXLEV_VAL 6 bitsRX_QUAL_FULL 3 bitsMEAN_BEP 5 bitsCV_BEP 3 bitsNBR_RCVD_BLOCKS 5 bits

N/A for LTE Repeated Invalid BSIC Info

BA_USED3G_BA_USED

ENHANCED MEASUREMENT REPORT message

BSIC_Seen SCALE Serving Cell Data


All relating to GPRS

operation


2 bits

E-UTRAN_CARRIER_FREQUENCY_INDEX 3 bits

CELL_IDENTITY 9 bits (PCI)

REPORTING_QUANTITY 6 bits (RSRP/RSRQ)

N_E_UTRAN

E-UTRA Measurement Report

6 Bits BSIC-NCELL

(LSB) LTE PCI 3-bit level LTE PCI (MSB)

6 Bits RXLEV-NCELL

becomes



GPRS Packet Handover to LTE

A number of different scenarios are possible for the transfer of a packet data connection from GPRS to LTE. Two typical examples are shown in the diagram, one where the MS is initially in Packet Idle mode and one where the MS is initially in Packet Transfer mode. To operate these cases it is assumed that the MS supports capability for CCN (Cell Change Notification) mode and for NC2 (Network Control Mode 2).

In the packet idle state the MS has received LTE neighbour cell information and an indication that CCN is active and that the MS operating initially in NC0 or NC1. The MS finds a suitable LTE cell, starts CCN mode and sends a PACKET CELL CHANGE NOTIFICATION message. The contents of this message are very similar to a MEASUREMENT REPORT message. In this case the BSS responds with a PACKET MEASUREMENT ORDER message configured to force the MS into NC2 mode. On receipt of this message the MS stops CCN mode, starts NC2 mode and waits for instructions from the BSS. The BSS then sends a PS HANDOVER COMMAND message , wh i ch encapsu la tes an RRCConnectionReconfiguration message provided by the target eNB.

In the packet transfer mode it is assumed that the MS is initially in either NC1 or NC2 mode and the MS has received LTE neighbour cell information. The MS sends a PACKET MEASUREMENT REPORT message, but an option also exists for the use of ENHANCED PACKET MEASUREMENT REPORT. If the MS is not already in NC2 mode then the BSS will send a PACKET MEASUREMENT ORDER message configured to force the MS into NC2 mode. The BSS then sends a PS HANDOVER COMMAND message, which encapsulates an RRCConnectionReconfiguration message provided by the target eNB.

Further Reading: 3GPP TS 44.060; 8.8.3, 8.10.3, 8.10.4

SourceBSS

TargeteNB

SourceCN node MME

MS

PACKET CELL CHANGE NOTIFICATION

PACKET MEASUREMENT ORDER or SYS INFO or PACKET SYS INFO


PACKET MEASUREMENT ORDER(use NC2)

PS HANDOVER COMMAND



PACKET MEASUREMENT REPORT

PACKET MEASUREMENT ORDER or SYS INFO or PACKET SYS INFO


PACKET MEASUREMENT ORDER(use NC2)

PS HANDOVER COMMAND





Uplink Power Control

Even though uplink transmissions from LTE UEs in a cell are orthogonal, uplink power control is still important if maximum throughput efficiency is to be achieved for individual UEs and for the cell as a whole.

The UE calculates the transmit power to be used in each subframe in which it has a resource allocation according to the formula shown in the diagram. Maximum power is limited by the UE power class, which will correspond to 23 dBm. The calculation for power to be used below this level is based on three elements: a bandwidth-dependent element, a semi-static open-loop operating point and a dynamic closed-loop offset.

The bandwidth element is based on the number of scheduled RBs in the UE’s uplink transmission.

The semis-static control point is itself made up from two elements. The first, PO_PUSCH(j), is a cell-defined offset between –126 dBm and +23 dBm. The second part is a compensation factor based on the UE’s estimate of downlink path loss. The value α can be varied between 0 and 1. Variation of PO_PUSCH(j) and α provide a trade-off between absolute cell performance and overall system performance.

The dynamic closed loop offset is based on TPC (Transmit Power Control) commands transmitted to the UE in the PDCCH and identifies using a TPC-RNTI. The closed loop mode of operation can operate in tow modes, one in which absolute power control commands are sent and one where corrections on a accumulative value are sent. It is in the latter case that is referenced by the parameter f(i).

If a UE was allocated an uplink bandwidth that resulted in a calculated power higher than 23 dBm, then the UE would be unable to use the full resource. To avoid this the UE sends power headroom reports to the eNB. These represent the UE’s estimate of its power control requirements in the current subframe, and based on this, the eNB can schedule resources efficiently between UEs in a cell.


PPUSCH(i)

Power control headroom

mBd})i(f+)i(FT+LP.)j(+)j(HCSUP_OP+))i(HCSUPM(01gol01,XAMCP{nim=

UE Power Class

1

2

3

4

...

...

23 dBm

...

Bandwidth dependent element,

MPUSCH(i) is the number of allocated

RBs

ssolhtaprofrotcafnoitasnepmoc

asiLP.)j(dnalevelesabdenifed-llecehtsi)j(HCSUP_OP

,tniopgnitarepopool-nepocitats-imeS

sdnammocCPTfonoitalumuccaehtsi)i(fdnadnammocCPT

enosi)i(FT,tesffopool-desolccimanyD



Timing Advance

In order to maintain orthogonality between uplink transmissions from multiple UEs in a cell, timing adjustment must be applied to compensate for variations in propagation delay.

Initial timing advance is calculated at the eNB from a UE’s preamble transmission on the PRACH. The timing advance correction is given as an 11-bit value, although the range is limited to 0–1282 timing advance steps. Granularity is in steps of 16Ts (0.52 µs) so timing advance can be varied between 0 and 0.67 ms. One timing advance step corresponds to a distance change of c.78 m and is significantly smaller than the normal CP, The maximum timing advance value corresponds to a range of c.100 km.

The maximum specified speed for a UE relative to an eNB is 500 km/h (139 m/s), which would require slightly more than one timing advance change every two seconds. Consideration also needs to be given to the possibility of more extreme changes in the multipath characteristics of a channel, for example the sudden appearance or disappearance of a strong reflected path from a distant object or delay through a repeater. However, these are extreme examples and, in any case, timing advance update commands can indicate up to +/– 16 µs in a single step. Thus the rate at which timing advance commands need to be sent in practice is typically much less than one every two seconds.

Timing update commands are transmitted to UEs as MAC control messages and as such are included in MAC PDUs carrying data for the UE on the PDSCH. The command itself is a 6-bit value giving a number range from 0–63. Values less than 31 will reduce timing advance and values greater than 31 will increase timing advance.


eNB measures propagation delay from PRACH preamble

TA step size is 16Ts (0.52 µs)

Correction is included in the RAR as a value of steps in the range 0 to 1282 (0 to 0.67 ms)

TA adjustments are made using MAC control messages in the PDSCH

Correction is a value in the range 0 to 63 interpreted as +/– 31 steps (+/– 16 µs)



CQI Reporting

Link adaptation is a crucial part of the LTE air interface and involves the variation of modulation and coding schemes to maximize throughput on the air interface.

Link adaptation for scheduled uplink resources can be can be calculated by the eNB from a number of inputs based on measurements of the UEs’ uplink transmissions. Additionally, the eNB may request that UEs transmit sounding reference signals, the measurements results of which can also be used for link adaptation.

For downlink transmissions the eNB needs information about the success or otherwise of the UE in receiving its downlink transmissions. The UE assesses the quality of the downlink signal through measurements of the received signal and consideration of the error correction scheme. It then calculates the maximum modulation and coding scheme that it estimates will maintain an error rate better than 10%. This is indicated to the eNB as a CQI value. The table in the diagram (taken from the 3GPP standards) shows how the CQI values are interpreted as modulation and coding schemes. The table is also useful for estimating the likely physical layer throughput in an given radio configuration.


Efficiency(bits/symbol)

0 No TX ... ... 1 QPSK 0.076 0.15232 QPSK 0.12 0.23443 QPSK 0.19 0.3774 QPSK 0.3 0.60165 QPSK 0.44 0.8776 QPSK 0.59 1.17587 16QAM 0.37 1.47668 16QAM 0.48 1.91419 16QAM 0.6 2.406310 64QAM 0.45 2.730511 64QAM 0.55 3.322312 64QAM 0.65 3.902313 64QAM 0.75 4.523414 64QAM 0.85 5.115215 64QAM 0.93 5.5547

CQI Index Modulation Approx. code

rate

Downlink channel adaptation based on

UE CQI reporting

Uplink channel adaptation based on eNB measurements of UL data

transmissions and SRS if requested



CQI Reporting Options

CQI reporting can be configured for a UE in several ways. Firstly, the types of reporting is instructed as either periodic or aperiodic. For periodic reporting the CQI is carried in the PUCCH at regular intervals that can be configured between 2 ms and 160 ms. For aperiodic reporting the CQI is carried in the PUSH only after a specific request from the eNB, which is included in the PDCCH scheduling information.

Additionally, the CQI feedback mode may be configured as wideband feedback, eNB-configured sub-band feedback or UE-selected sub-band feedback. All three options are applicable for aperiodic reporting, but only wideband feedback and UE-selected sub-band feedback can be configured for periodic reporting.

For wideband feedback the reported CQI value is based on an assessment across the whole system bandwidth. For both sub-band feedback modes, sub-bands are defined across the system bandwidth as groups of consecutive RBs. The size and number of sub-bands is fixed dependent on the total system bandwidth and the feedback mode in use. For the eNB-configured sub-band feedback mode the UE reports the wideband CQI and then each sub-band CQIs as relative offset values. For the UE-selected sub-band feedback mode the UE selects a set of preferred sub-bands from the total available sub-bands and indicates their positions to the eNB. Then it reports an average CQI value for these preferred sub-bands along with a wideband CQI value.


CQI Reporting

AperiodicReports on request in

PUSCH

PeriodicReports regularly in

PUCCH

UE-selected sub-band feedback

CQI across total system bandwidth+

Preferred sub-band positions+

CQI average for preferred sub-bands

Wideband feedback

CQI across total system bandwidth

eNB-configured sub-band feedback

CQI across total system bandwidth+

CQI offset for each sub-band



Management of DRX for Connected Mode

In addition to DRX for UEs in idle mode, E-UTRA also supports DRX for UEs in RRC connected mode. This process is controlled collectively by MAC and RRC. The parameters are set by RRC but it is the MAC layer the operates the process itself.

The onDurationTimer defines the length of time that the UE is active and monitoring downlink control channels when DRX is running; in the example in the diagram this is set to two subframes (2 ms). This operates in conjunction with a DRX cycle that defines the amount of time that the UE can be ‘off’. There are two DRX cycles defined for a UE known as the longDRX-Cycle and the shortDRX-Cycle. As can be seen in the diagram, the longDRX-Cycle is the default value.

When a period of activity is started through the scheduling of resources for the UE’s C-RNTI, the UE starts the drx-InactivityTimer. If the UE remains active long enough for the drx-InactivityTimer to expire, or if it receives a MAC CE on which it may have to act, then, when activity stops, the UE will use the shortDRX-Cycle period and start also the drxShortCycleTimer. If no further activity takes place before the drxShortCycleTimer expires then the UE reverts to the longDRX-Cycle period.

Further Reading: 3GPP TS 36.321; 5.7, 36.331

eNB

longDRX-Cycle shortDRX-Cycle

shortDRX-Cycle

longDRX-CycleReception period

Physical layer subframe

onDurationTimer

DL schedule for UE’s C-RNTI

drx-InactivityTimer started

drx-InactivityTimer expires or UE receives

a MAC CE

drxShotCycleTimer started

drxShotCycleTimer expires




GLOSSARY OF TERMS


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G.ii © Wray Castle Limited LT1001/v2

LT1001/v2 G.1© Wray Castle Limited

Glossary of Terms

16QAM 16-State Quadrature Amplitude Modulation1xEV-DO HRPD 1x Evolution – Data Only (High Rate Packet Data)2G Second Generation3G Third Generation3GPP 3rd Generation Partnership Project64QAM 64-State Quadrature Amplitude Modulation

AC Access ClassANR Automatic Neighbour Relation ARFCN Absolute Radio Frequency Channel NumberAS Access Stratum

BCCH Broadcast Control ChannelBCH Broadcast ChannelBSC Base Station ControllerBSIC Base Station Identity CodeBSS Base Station System

CGI Cell Global IdentityCCN Cell Change Notification CCO Cell Change Order CDMA Code Division Multiple AccessCP Cyclic PrefixCQI Channel Quality IndicationC-RNTI Cell Radio Network Temporary Identifier CRI Contention Resolution IdentityCSG Closed Subscriber Group CSG ID Closed Subscriber Group Identity

DL DownlinkDL-SCH Downlink Synchronization ChannelDRS Demodulation Reference Signals DRX Discontinuous ReceptionDVB Digital Video Broadcasting

EARFCN E-UTRA Absolute Radio Frequency Channel NumberECM EPS Connection Management EMM EPS Mobility Management eNB evolved Node BEPLMN Equivalent Public Land Mobile NetworkEPS Evolved Packet SystemE-UTRA Evolved Universal Terrestrial Radio AccessE-UTRAN Evolved Universal Terrestrial Radio Access Network

FCC Federal Communication CommissionFDD Frequency Division Duplex

GPRS General Packet Radio ServiceGSM Global System for Mobile CommunicationsGT Guard Time

HCS Hierarchical Cell StructureHeNB Home evolved Node BHPLMN Home Public Land Mobile NetworkHSS Home Subscriber Server

Inter-RAT Inter-Radio Access Technology IP Internet ProtocolIRAT Inter-Radio Access Technology

LTE Long Term Evolution

LT1001/v2G.2 © Wray Castle Limited


MAC Medium Access ControlMBMS Multimedia Broadcast and Multicast ServiceMBSFN Multicast/Broadcast Single Frequency Network MGL Measurement Gap LengthMGRP Measurement Gap Repetition PeriodMIB Master Information BlockMIMO Multiple Input Multiple Output MM Mobility Management MME Mobility Management EntityMO Mobile OriginatedMS Mobile StationMU-MIMO Multi User MIMO

NACC Network Assisted Cell Change NAS Non-Access Stratum NC2 Network Control Mode 2NRT Neighbour Relation Table

OAM Operations and MaintenanceOFDM Orthogonal Frequency Division MultiplexingOFDMA Orthogonal Frequency Division Multiple Access

PBCH Physical Broadcast Channel PCFICH Physical Control Format Indicator Channel PCI Physical Cell IdentityPDCCH Physical Downlink Control Channel PDU Packet Data UnitPHICH Physical Hybrid ARQ Indicator Channel PLMN Public Land Mobile NetworkPMI Pre-coding Matrix Indicator PRACH Physical Random Access Channel PS Packet SwitchedPSS Primary Synchronization Signal PUCCH Physical Uplink Control Channel PUSCH Physical Uplink Shared Channel

QoS Quality of Service QPSK Quadrature Phase Shift Keying

RACH Random Access ChannelRAN Radio Access NetworkRAR Random Access ResponseRA-RNTI Random Access Radio Network Temporary Identifier RAT Radio Access Technology RB Resource BlockRF Radio FrequencyRLC Radio Link ControlRNC Radio Network ControllerRNTI Radio Network Temporary IdentifierRPLMN Registered Public Land Mobile NetworkRR Radio ResourceRRC Radio Resource ControlRSCP Received Signal Code PowerRSRP Reference Signal Received PowerRSRQ Reference Signal Received QualityRSSI Received Signal Strength Indicator

SFN Single Frequency Network SIB System Information BlockSIM Subscriber Identity Module

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Glossary of Terms

SINR Signal to Interference and Noise RatioSISO Single Input Single Output SON Self-Optimizing NetworkSRS Sounding Reference SignalsSSS Secondary Synchronization SignalSU-MIMO Single User MIMO

TA Tracking AreaTAI Tracking Area IdentityTDD Time Division DuplexTMSI Temporary Mobile Subscriber IdentityTPC Transmit Power Control TTI Transmission Time Interval ttt time to trigger

UE User EquipmentUL-SCH Uplink Synchronization ChannelUMTS Universal Mobile Telecommunications SystemUTRAN Universal Terrestrial Radio Access Network

VPLMN Visited Public Land Mobile Network

WiMAX Worldwide Interoperability for Microwave Access

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