(E)gprs radio networks_-_optimization_guidelines

1/90 CMO SBU MS Network & Service Optimization Capability Management

15/12/2008

Copyright 2007 Nokia Siemens Networks. All rights reserved.

(E)GPRS Radio Networks Optimization Guidelines Version 3.0


15/12/2008


DOCUMENT DESCRIPTION

Title and version (E)GPRS Radio Networks Optimization Guidelines v3.0 Reference Target Group Radio, Tranmission, E2E Technology and SW release

GERAN - S13

Related Service Items

Service Item number

Author Pal Szabadszallasi Date Approver Villa Salomaa

CHANGE RECORD

This section provides a history of changes made to this document

VERSION DATE EDITED BY SECTION/S COMMENTS Ver. 1.0 24.11.2004 Pal Szabadszallasi Ver. 2.0 24.06.2006 Pal Szabadszallasi Ver. 3.0 16.12.2008 Pal Szabadszallasi

Copyright © Nokia Siemens Networks. This material, including documentation and any related computer programs, is protected by copyright controlled by Nokia Siemens Networks. All rights are reserved. Copying, including reproducing, storing, adapting or translating, any or all of this material requires the prior written consent of Nokia Siemens Networks. This material also contains confidential information which may not be disclosed to others without the prior written consent of Nokia Siemens Networks.


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Table of contents

1. Introduction....................................................................................... 7

1.1 BSS Optimization Approach........................................................................................... 8 1.2 Parameters and Features Having Main Impact on Network Performance....................... 9

2. Configuration, Parameter and Feature Audit................................... 10

2.1 BSS Configuration and Parameter Audit ...................................................................... 11 2.1.1 Area and Network Element Audit ................................................................................. 11 2.1.2 RF Deployment and PSW Parameter Audit.................................................................. 12 2.1.3 BSC and PCU and Flow Control Parameter Audit ........................................................ 13 2.1.4 HLR Setting Audit......................................................................................................... 14 2.2 BSS Feature Audit ....................................................................................................... 15

3. Performance Audit .......................................................................... 18

3.1 OSS KPI Analysis ........................................................................................................ 18 3.1.1 NetAct Reporter ........................................................................................................... 18 3.2 Inactivity Alarm (S12 onwards)..................................................................................... 19 3.3 Field Tests ................................................................................................................... 20 3.4 Real-Time Protocol Testing .......................................................................................... 20 3.5 Application Testers....................................................................................................... 20 3.6 Post-Processing Tools ................................................................................................. 20

4. GSM Coverage and Quality Optimization ....................................... 21

4.1 (E)GPRS Coverage Area Estimation and Maximization ............................................... 21 4.1.1 Signal Level vs. TSL Data Rate.................................................................................... 21 4.1.2 Interference vs. TSL Data Rate .................................................................................... 21 4.1.3 Signal Level and Interference vs. TSL Data Rate ......................................................... 23 4.2 Site Arrangement ......................................................................................................... 23 4.3 Frequency Plan ............................................................................................................ 23 4.4 Optimal GSM Network for PSW Services..................................................................... 23

5. Signaling Capacity Improvement .................................................... 25

5.1 Air Interface Signaling .................................................................................................. 25 5.1.1 PCH (NMO II)............................................................................................................... 25 5.1.1.1 Traffic Volume.............................................................................................................. 25 5.1.1.2 Rejection...................................................................................................................... 25 5.1.1.3 Paging message deletion ratio ..................................................................................... 25 5.1.1.4 Paging success ratio on PS (2G SGSN)....................................................................... 25 5.1.1.5 Solution for reducing PCH rejection and load ............................................................... 26 5.1.2 PCH (NMO I)................................................................................................................ 26 5.1.2.1 Traffic Volume.............................................................................................................. 26 5.1.2.2 Congestion (CS + PS).................................................................................................. 26 5.1.2.3 Paging of MS in Packet Transfer Mode ........................................................................ 26 5.1.2.4 Gs Interface (2G SGSN) .............................................................................................. 26 5.1.3 AGCH .......................................................................................................................... 26 5.1.3.1 Traffic Volume (with Rejection)..................................................................................... 26 5.1.3.2 Congestion................................................................................................................... 27 5.1.3.3 Solution for reducing AGCH rejection and load ............................................................ 27 5.1.4 RACH........................................................................................................................... 27


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5.1.4.1 Load............................................................................................................................. 27 5.1.4.2 Load and quality (repetitions of PS channel requests).................................................. 27 5.1.4.3 Solution for reducing RACH rejection and load ............................................................ 27 5.1.5 SDCCH ........................................................................................................................ 27 5.1.5.1 Traffic Volume.............................................................................................................. 27 5.1.5.2 Congestion................................................................................................................... 28 5.1.5.3 Quality.......................................................................................................................... 28 5.1.5.4 Solution for reducing SDCCH load ............................................................................... 28 5.1.6 Parameters .................................................................................................................. 28 5.1.7 Features....................................................................................................................... 29 5.1.7.1 NMO1 with Gs Interface ............................................................................................... 29 5.1.7.2 EPCR (S11, UltraSite, MS R99) with one phase access .............................................. 29 5.1.7.3 Resume........................................................................................................................ 29 5.1.8 TBF Establishment Failure ........................................................................................... 30 5.2 TRXSIG........................................................................................................................ 30 5.3 PCU ............................................................................................................................. 30 5.4 BCSU........................................................................................................................... 30 5.5 MM and SM Signaling .................................................................................................. 31

6. Resource Allocation Improvement .................................................. 32

6.1 PSW Activation and Territory Settings.......................................................................... 32 6.1.1 Parameters .................................................................................................................. 32 6.1.2 Measurements – KPIs.................................................................................................. 33 6.2 Cell (Re)-Selection ....................................................................................................... 34 6.2.1 C1 and C2 and HYS..................................................................................................... 34 6.2.2 Cell re-selection Measurements (NC_0)....................................................................... 35 6.3 NCCR .......................................................................................................................... 35 6.3.1 NCCR Criteria .............................................................................................................. 37 6.3.2 NCCR – Power Budget ................................................................................................ 37 6.3.3 NCCR – Quality Control ............................................................................................... 37 6.3.3.1 Block Error Rate (BLER) .............................................................................................. 38 6.3.3.2 BLER Degradation Duration Counter ........................................................................... 38 6.3.3.3 Bitrate (BER)................................................................................................................ 39 6.3.3.4 Bitrate per Radio Block Degradation Duration Counter................................................. 39 6.3.3.5 Corrective Actions ........................................................................................................ 39 6.3.4 NCCR Parameters with Power Budget and Quality Control.......................................... 40 6.3.5 Cell re-selection Measurements (NC_2)....................................................................... 41 6.4 BTS Selection in Segment (MultiBCF and CBCCH) ..................................................... 42 6.4.1 Parameters .................................................................................................................. 42 6.4.2 Measurements ............................................................................................................. 42 6.5 Scheduling (TSL Selection with Priority based QoS) .................................................... 43 6.5.1 Parameters .................................................................................................................. 44 6.6 DAP Resource Allocation in PCU1............................................................................... 44

7. Connectivity Capacity Optimization................................................. 46

7.1 Connectivity Limits in PCU ........................................................................................... 46 7.1.1 Connectivity Limits in SGSN and PAPU (SG6)............................................................. 46 7.1.2 Connectivity Capacity Optimization – Maximized Capacity........................................... 47 7.1.3 Connectivity Capacity Optimization – Maximized Data Rate......................................... 47 7.1.4 Connectivity Limit related Measurements - KPIs .......................................................... 48

8. RLC/MAC TSL Data Rate Maximization ......................................... 49


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8.1 TLS utilization .............................................................................................................. 50 8.1.1 Acknowledge Request.................................................................................................. 50 8.1.2 Pre-Emptive Transmission ........................................................................................... 50 8.1.3 UL TBF Assignment with One / Two Phase Access and EPCR.................................... 51 8.1.4 EPCR........................................................................................................................... 51 8.1.5 TBF Release Delay, TBF Release Delay Ext and BS_CV_MAX .................................. 51 8.1.5.1 DL_TBF_RELEASE_DELAY (0,1-5sec, def 1s) ........................................................... 51 8.1.5.2 UL_TBF_RELEASE_DELAY (0,1-3sec, def 0,5s) ........................................................ 52 8.1.5.3 Extended UL TBF Mode (EUTM) ................................................................................. 52 8.1.5.4 BS_CV_MAX ............................................................................................................... 53 8.1.5.5 Measurements ............................................................................................................. 53 8.1.5.6 Parameters .................................................................................................................. 54 8.2 GPRS Link Adaptation ................................................................................................. 54 8.2.1 Measurements ............................................................................................................. 55 8.2.2 Parameters .................................................................................................................. 55 8.3 EGPRS Link Adaptation ............................................................................................... 56 8.3.1 Measurements ............................................................................................................. 56 8.3.2 Parameters .................................................................................................................. 56 8.3.3 Effect of Link Adaptation .............................................................................................. 57 8.4 Multiplexing .................................................................................................................. 58 8.4.1 Synchronization............................................................................................................ 58 8.4.2 Timeslot sharing........................................................................................................... 59 8.4.3 GPRS and EGPRS Multiplexing................................................................................... 59 8.4.4 Dynamic Allocation with USF4 ..................................................................................... 59 8.4.5 Extended Dynamic Allocation....................................................................................... 59 8.4.6 Measurements ............................................................................................................. 59 8.4.7 Parameters .................................................................................................................. 59 8.5 UL Power Control......................................................................................................... 60 8.5.1 Measurements ............................................................................................................. 61 8.5.2 Parameters .................................................................................................................. 61

9. Multislot Usage Maximization ......................................................... 63

9.1 TSL unavailability ......................................................................................................... 63 9.2 CSW traffic and HSCSD............................................................................................... 63 9.3 Territory Downgrade .................................................................................................... 63 9.4 Territory Upgrade Request Rejection ........................................................................... 64 9.5 Free TSLs .................................................................................................................... 64 9.6 HMC and EDA.............................................................................................................. 64 9.7 Measurements ............................................................................................................. 65

10. End-to-End Data Rate Maximization............................................... 67

10.1 HLR Settings................................................................................................................ 67 10.1.1 HLR QoS Profile Handling (MML command: MYQ) ...................................................... 67 10.1.2 Subscriber Data Handling (MML command: MN) ......................................................... 67 10.1.3 QoS Parameter Set Recommendation ......................................................................... 69 10.2 Gb over FR .................................................................................................................. 69 10.3 Gb over IP.................................................................................................................... 70 10.4 TCP/IP ......................................................................................................................... 71 10.5 Measurements ............................................................................................................. 72

11. Mobility Optimization....................................................................... 73

11.1 Cell-reselection without LA/RA Update (Intra/Inter PCU).............................................. 74


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11.2 Cell-reselection with LA/RA Update.............................................................................. 78 11.2.1 Cell-reselection with uncombined LA/RA Update ......................................................... 78 11.2.2 Cell-reselection with combined RAU (NMO1, Gs interface required) ............................ 81 11.3 Cell-reselect Hysteresis................................................................................................ 81 11.4 PCU Balancing............................................................................................................. 83 11.5 LA/RA Design .............................................................................................................. 85 11.6 NACC........................................................................................................................... 86

12. Applications .................................................................................... 88

12.1 Service Types .............................................................................................................. 88 12.1.1 Conversational Services............................................................................................... 88 12.1.2 Streaming Services ...................................................................................................... 88 12.1.3 Interactive Services...................................................................................................... 88 12.1.4 Background Services ................................................................................................... 88 12.2 Dual Transfer Mode (DTM)........................................................................................... 89 12.3 Push to Talk (PoC)....................................................................................................... 89

13. References ..................................................................................... 90


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1. Introduction The purpose of (E)GPRS Radio Networks – Optimization Guidelines is to describe the (E)GPRS BSS Network Optimization requirements and activities.

The form of this document is same as a closing report of Optimization Projects, so the same structure with the same topics can be used as reference for EGPRS optimization projects.

This document is part of EDGE Radio Networks planning document set, which is separated as listed below:

- (E)GPRS Radio Networks – Planning Theory

- (E)GPRS Radio Networks – Dimensioning and Planning Guidelines

- (E)GPRS Radio Networks – Optimization Guidelines

These documents are strongly linked to each other, thus the separated usage is not recommended.

(E)GPRS BSS optimization contains BSS network elements such as air interface, EDAP and PCU, therefore mainly the RLC/MAC layer is investigated in the (E)GPRS protocol stack. See RLC/MAC layer between mobile and BSC/PCU in Figure 1 below.

Figure 1 (E)GPRS protocol stack

This version of the Optimization Guidelines is based on S11.5, S12 and S13 BSS software with PCU1 and PCU2.

The simulation and measurement results in the document were gathered from Nokia Test Network, operators’ test and live networks.

LLC

SNDCP

LLC

SNDCP

L1/RF L1/RF

UmMS BTS

FR

NS

BSSGP

FR

NS

BSSGP

GbSGSN

GTP

UDP

IP

L1

L2

GTP

UDP

IP

L1

L2

GnGGSN

RLC/MAC RLC/MAC

DAbis DAbis

AbisBSC / PCU

IP

L1

L2

WWW/FTP

Server

Gi

TCP

HTTPor FTP

L1

L2

IP

TCP

HTTPor FTP


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1.1 BSS Optimization Approach The (E)GPRS BSS network optimization approach can be seen in Figure 2 below:

Configuration and

Feature Audit

BSS and End-to-End

Performance Audit

GSM Network

Optimization

(E)GPRS Network Optimization

•Area and network element audit

•RF deployment and parameter audit

•BSC and PCU parameter audit

•OSS KPIs

•Field tests

•Real-time protocol testing

•Post-processing

•Coverage maximization

•Interference reduction

•Capacity optim. (air interf. and connectivity)

•Signaling capacity improvement

•Resource allocation improvement

•E2E Data rate improvement

•Connectivity capacity

•RLC/MAC data rate (TSL and multislot)

•E2E Data rate

•Mobility improvement

Configuration and

Feature Audit

BSS and End-to-End

Performance Audit

GSM Network

Optimization

(E)GPRS Network Optimization

•Area and network element audit

•RF deployment and parameter audit

•BSC and PCU parameter audit

•OSS KPIs

•Field tests

•Real-time protocol testing

•Post-processing

•Coverage maximization

•Interference reduction

•Capacity optim. (air interf. and connectivity)

•Signaling capacity improvement

•Resource allocation improvement

•E2E Data rate improvement

•Connectivity capacity

•RLC/MAC data rate (TSL and multislot)

•E2E Data rate

•Mobility improvement

Figure 2 (E)GPRS Optimization steps


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There are lots of references to 3GPP Specifications in the document. The specifications can be found at the following intranet location:

http://www.3gpp.org/specification-numbering

1.2 Parameters and Features Having Main Impact on Network Performance

The following items have the main impact on (E)GPRS network performance:

• GSM signal level and interference

• Deployment strategy and resource allocation

o CS and PSW traffic volume and allocation (TRP, BFG)

o GENA / EGENA settings

o CDEF, CDED and CMAX settings

• Connectivity Limits

o PCU limits (CDEF and EDAP size)

• RLC/MAC TSL and multislot data rate

o TBF Release Delay, TBF Release Delay Ext and BS_CV_MAX

o Link Adaptation (MCA)

o Multislot usage

• E2E data rate

o Flow control utilization (link size)

o TCP/IP settings (TCP window, TCP buffer, MCU, MSS)

o Applications (terminal type, application type)

• Mobility (cell outage)

o Proper PCU connectivity and LA/RA design

o NACC


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2. Configuration, Parameter and Feature Audit This chapter contains the description of the BSS configuration, parameter and feature audit.

The Figure 3 is an example to introduce the end-to-end network configuration.

BSC GGSN

IP/MPLS/IPoATM-

backbone

Application Servers

(co-located

or remote)

2GSGSN

BTS

HLR/AC/EIR

TCSM

TC

MSC/VLR

EDAP FR

Gn Gi

Gs

BSC BSC GGSNGGSN

IP/MPLS/IPoATM-

backbone

Application Servers

(co-located

or remote)

2GSGSN2G

SGSNBTS

HLR/AC/EIR

HLR/AC/EIR

TCSM

TC

MSC/VLR

EDAP FR

Gn Gi

Gs

Figure 3 End-to-end network configuration


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2.1 BSS Configuration and Parameter Audit The aim of this chapter is to summarize the initial configuration of the sites involved in optimization project. The OSS Radio Manager and MML commands are used to obtain the parameter information. More information related to parameters is available in [2]. The chapter is organized in the following sections:

• Area and network element information

• RF configuration and PSW parameters

• BSC, PCU parameters

• HLR setting

2.1.1 Area and Network Element Audit

The following information should be collected related to (E)GPRS optimization area:

o Area size

o # of sites

o # of cells, segments

o # of cells, segments / site

The above information gives picture about built in capacity situation.

o Average distance among sites

o Antenna types

o Average antenna height

o Frequency bands

o Reuse factors

The information above shows the signal and interference situation in general.

The following information should be collected related to network element types and software:

o BSC types

o PCU types

o BTS types

o BSC SW with CD information

o BTS SW

The BSC, PCU and BTS hardware and SW limits can be checked by the information above.


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The following information should be collected related to the volume of network element and connectivity usage of network elements:

o # of BSCs

o # of PCU/BSC ratio

o # of BCF/PCU ratio

o # of Cells/PCU

o # of Abis TSLs/PCU

o # of DAP/PCU

o Average DAP size/BCF

o # of Gb TSLs (64 kbps)/PCU

The connectivity limits can be estimated based on the list above.

The following information should be collected related to terminals used in the network:

o Ratio of AMR capable terminals

o Ratio of R97, R98, R99, R4, R5, R6 capable terminal

o Ratio of the different TSL capability terminals (with HMC and EDA)

The capacity requirements and feature possibilities can be analyzed by the list above.

2.1.2 RF Deployment and PSW Parameter Audit

The following issues (planning approaches, parameter settings) can be investigated on air interface:

o Cell, segment structure and layer usage (MultiBCF and CBCCH usage)

o Deployment options (allocation strategy of TCHs among signaling, voice (FR, HR and DR), CS data (HSCSD) and PS data)

o Idle mode related parameters like Cell-reselect hysteresis, Rx Lev Access Min, C1, C2 related parameters

o RF related parameters:

• GENA, EGENA, GTRX

• TRP, BFG • TRP, BFG (S11 onwards) • CMAX • CDEF • CDED • TERRIT_UPD_GTIME_GPRS


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• FREE TSL FOR CS DOWNGRADE • FREE TSL FOR CS UPGRADE

• MAXIMUM NUMBER OF DL TBF • MAXIMUM NUMBER OF UL TBF

• MultiBCF and CBCCH: NBL, DIRE, LSEG, GPU, GPL

2.1.3 BSC and PCU and Flow Control Parameter Audit

The following PCU, PAFILE and PRFILE parameters must be investigated and modified according to NSN recommendations:

o GPRS Link Adaptation related parameters: DLA, ULA, CODH, COD, DLBH, ULBH, DLB, ULB

o GPRS Link Adaptation related parameters (PCU2): CS34, DCSA, UCSA, DCSU, UCSU

o EGPRS Link Adaptation related parameters: ELA, MCA, BLA, MBG, MBP

o Priority based QoS: SSS parameters

o UL Power Control: ALPHA, GAMMA, IFP, TFP

o DL_TBF_RELEASE_DELAY o UL_TBF_RELEASE_DELAY

o UL_TBF_RELEASE_DELAY_EXT o UL_TBF_SCHED_RATE_EXT

o BS_CV_MAX

o GPRS_UPLINK_PENALTY o GPRS_UPLINK_THRESHOLD o GPRS_DOWNLINK_PENALTY o GPRS_DOWNLINK_THRESHOLD o EGPRS_UPLINK_PENALTY o EGPRS_UPLINK_THRESHOLD o EGPRS_DOWNLINK_PENALTY o EGPRS_DOWNLINK_THRESHOLD

o FC_R_DIF_TRG_LIMIT o FC_MS_R_DEF o FC_MS_R_DEF_EGPRS o FC_MS_R_MIN o FC_MS_B_MAX_DEF o FC_MS_B_MAX_DEF_EGPRS o FC_R_TSL o FC_R_TSL_EGPRS o FC_B_MAX_TSL o FC_B_MAX_TSL_EGPRS


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o NCCR_STOP_DL_SCHEDULING o NCCR_STOP_UL_SCHEDULING o NCCR_NON_DRX_PERIOD o NCCR_MEAS_REPORT_TYPE

The detailed description of the above parameters and the NSN recommendations can be found in [2].

2.1.4 HLR Setting Audit

The following QoS settings have impact on BSS performance, so it must be checked and tuned according to the QoS policy:

o Reliability class = 3 o Traffic Class (TC) = Interactive o RLC mode = Acknowledged o THP = 1 o ARP = 1 o SDU error ratio = 10^-4 o Maximum Bitrate = 2048 kbps o Transfer delay = 1000ms


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2.2 BSS Feature Audit All the CSW and PSW BSS features that are impacting the PSW traffic are explained in this chapter.

• Idle mode settings and Directed Retry

If there is real TCH congestion in the accessed cell, then a Directed Retry due to congestion with or without queuing will be made. If there are TCHs available in accessed cell, then BSC will act according to the direct access criteria usage/determination (C/I evaluation) and cell load.

• BB and RF Hopping

BB and RF hopping can be used to spread the interference among the cells evenly. So the areas with very bad C/I parameters will be improved, while the areas with very good C/I figures will be decreased a bit.

Different layers can have different hopping policy, therefore the appropriate layer selection is important to maximize the (E)GPRS data rate.

If EDGE and non-EDGE TRXs are mixed in same BTS, BB Hopping requires segment solution and own hopping groups. (EDGE cannot move to non-EDGE TRX).

• MultiBCF and Common BCCH

The most appropriate layer can be selected by MultiBCF and CBCCH features, so the separation of GPRS from EGPRS is working properly. The separation is not that important if USF4 or EDA is used.

• FR / HR / DR with AMR

Each radio time slot of the BTS TRX can be configured to be a FR, HR, or dual rate (DR) TCH. In the case of dual rate, the BSC dynamically allocates the idle radio time slot either for half rate or full rate coding on a call basis.

The CSW calls will be allocated to FR firstly.

More timeslots are available for (E)GPRS traffic without more hardware (Increased average (E)GPRS total cell throughput for all users and improved probability for occasional high bit rate services for individual end users).

The drawback is a slight decrease in the speech quality using AMR half rate when compared to AMR full rate in very bad C/I environment. So smaller coverage is expected for AMR calls in low C/I networks.

The FRL, FRU, HRL and HRU parameters are based on available full rate TCH resource (not including signaling and GPRS territory - dedicated and default territory or DR RTSLs). The half rate is allocated before the CS traffic starts to use the GPRS territory (if FRL, FRU, HRL and HRU are set accordingly). In essence the GPRS territory is safeguarded to some degree. However in severe congestion, unoccupied dual rate timeslots can still be allocated to GPRS.

• HSCSD


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CSW data has priority over PSW traffic. Therefore the analysis of HSCSD traffic behavior is important.

• Extended Cell

ETRX cannot carry (E)GPRS TCHs in extended cell, but NTRX is able to handle it. Extended Cell can be used only with the BTS software BTS 1063 Extended cell radius. Extended Cell feature in UltraSite is available from S11.5 only.

• Extended cell for (E)GPRS

BSS13 supports the Extended Cell radius for Flexi EDGE base station (EP2.0).

The following considerations must be taken into account:

• Up to six GPRS/EDGE timeslots in both normal and extended area TRXs

• Operator configures fixed GPRS/EDGE timeslots to extended area TRX (GPRS/EDGE territory upgrades/downgrades not applied in extended area TRX)

• Intelligent Underlay Overlay

The IUO feature enables definition of super layer and regular layers by defining TRXs as such, i.e. trxFrequencyType=1 for a super TRX. IUO does not support (E)GPRS.

• Priority based QoS

The users can be prioritized, so the users with higher priority will have more allocations to Air interface. The Priority based QoS cannot be used for guarantied services, because it is prioritizing the available resources only.

However, Priority QoS is only way to differentiate BSS statistics based on services. So cell level statistics (from BSS) are available compared to network level based server statistics.

• NMO1

NMO1 with Gs interface allows to have combined RAU, so the cell-reselection is faster (SDCCH is not required), because LAU does not take place.

• NCCR

Network Controlled Cell Reselection helps to allocate terminals more effectively to those resources, where the data rate can be maximized.

• CS3-4

CS3-4 is available with PCU2.

• NACC

Network Assisted Cell Change feature reduces the cell-outage time (it is used with R4 onwards devices only).


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• DA with USF4

The detailed information related to DA and USF4 is available in [1].

• EDA

The detailed information related to EDA is available in [1].

• HMC

High Multislot Classes (HMC) increases GPRS/EDGE peak downlink throughput to 296 kbit/s.

3GPP release 4 or earlier MSs are limited to combined downlink and uplink timeslot sum of 5. 3GPP release 5 (TS 45.002) introduces new MS multislot classes which allow sum of downlink and uplink timeslots of 6.

New maximum allocation configurations:

• Downlink + uplink: 5+1 and 4+2

• Downlink + uplink: 3+3 and 2+4 (With Extended Dynamic Allocation Application Software)

The detailed description of these features above can be found in [1].

• DTM

Dual transfer mode is providing simultaneous circuit switched voice and Packet Switched data service in a coordinated manner.

In dual transfer mode, the mobile station is simultaneously in dedicated mode and in packet transfer mode so that the timeslots allocated in each direction are contiguous and within the same frequency.

The CS part consists of a single slot connection, while the PS part can consist of a multislot connection.

Entering to DTM mode goes through the dedicated mode:

• PS radio connection has to be released when entering and leaving Dual Transfer Mode

• Nokia solution minimizes the outage on downlink data transmission

• 3GPP release 6 allows transitions between PS and DTM (BSS13 candidate)

The Planning Theory of DTM can be [3] and the information about DTM planning is available in DTM – Planning guidelines [4].


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3. Performance Audit Performance measurements are needed to get clear picture about network functionality and find the possibilities for increasing the performance.

The (E)GPRS performance measurements and their analysis are usually separated to

• OSS KPI Analysis

• Inactivity Alarm Analysis

• Field Test Analysis

• Real-time measurement analysis

• Analyzers and post-processing

3.1 OSS KPI Analysis OSS counter and KPI analysis gives exact picture about (E)GPRS BSS network performance. The analysis of the networks based on KPIs can be based on the following benchmark KPI list:

S13 KPI report structure - planning and optimization KPIs v2.0.xls

The planning and optimization related KPIs can be found in the following file:

S13 KPI report structure - planning and optimization KPIs v2.0.xls

The materials related to KPIs can be found on the following link:

https://sharenet-ims.inside.nokiasiemensnetworks.com/livelink/livelink?func=ll&objId=358457268&objAction=Browse&viewType=1

The formulas listed in the excel files above can be found in the Network Operations Portal (JUMP page), too:

http://nop-i.nokiasiemensnetworks.com/bsc_fp.php

3.1.1 NetAct Reporter

The following Reporter applications can be used:

Report Builder


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• Report definition • KPI definition • Permissions

Report Explorer

• Report Browsing

• KPI Browsing

• Drilling

• Web based Report creation on existing KPI

Reporting Suites

• Ready-made implementations of KPIs and reports

• Subscription to Nokia Operations Portal allow on-line download

Customized Reporting Suites

• Delivered by C&I team

The following links gives information about NetAct Reporter:

http://domino.inside.nokiasiemensnetworks.com/NET/OSS/bookshlf.nsf/vwDocsByCat1All2?OpenView&Start=1&Count=1000&Expand=36

https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/NetAct_RS

3.2 Inactivity Alarm (S12 onwards) In S12 the “7789 NO (E)GPRS TRANSACTIONS IN BTS” base station alarm is implemented. The meaning of this alarm is to find out the reason for the loss of BTS traffic capacity and bring the BTS back to use.

It appears if there is no succesful (E)GPRS transactions have occured within the supervision period.

The supplementary information fields are listed below:

1 Criteria used to detect the (E)GPRS Inactivity.

0 = Alarm disabled

1 = No Successful UL TBFs only

2 = No Successful DL TBFs only

3 = No Successful UL nor DL TBFs


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The system cancels the (E)GPRS Inactivity Alarm when (E)GPRS traffic occurs again in the BTS, where the alarm was previously raised.

The user can also cancel the alarm with the EEJ command (criteria = disabled).

3.3 Field Tests The Nokia projects mainly use Nemo Outdoor (former TOM) and TEMS Investigator. In some projects the SwissQual and Agilent are used as well. (Other field measurement tools are available from Anritsu, Cuoei, Condat, QualComm and Rohde&Schwarz.)

3.4 Real-Time Protocol Testing The following testers are recommended and described in the subsections below.

o Traffica

o 3rd party tools

o Agilent

o NetHawk

o RadCom

o Tektronix

3.5 Application Testers The most common application testers are listed below:

• Application Tester

• Ethereal

• Commview

3.6 Post-Processing Tools The most common post-processing tools are listed below:

• Actix Analyzer

• NetCare

• NetTest

• Ad hoc environment can be built around Excel / Access


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4. GSM Coverage and Quality Optimization The physical layer of (E)GPRS is the existing GSM network, therefore the analysis of GSM network performance is important step in (E)GPRS optimization. The aim here is to estimate and maximize the (E)GPRS service area for each coding schemes based on GSM functionality.

The following subchapters describe the function of signal level, interference and data rate from test lab and live test measurements (the available capacity is not a limiting factor).

4.1 (E)GPRS Coverage Area Estimation and Maximization The GSM coverage and interference analysis is needed to estimate the current GSM functionality to find the possible room for improving signal level and C/I, hence improving (E)GPRS data rate as well.

The following subchapters contain the impact of signal level and interference on data rate.

4.1.1 Signal Level vs. TSL Data Rate

The target of this chapter is to show the effect of signal level on data rate. The sensitivity threshold of the receivers determines the MCSs used during the connections.

The Figure 4 shows that if the signal level is less then around –90 dBm and there is not any interference, than the RLC/MAC throughput will be lower then 100 kbps (Nokia Test Network (NTN) result). The outdoor field strength in city environment is higher than –90 dBm, but the indoor performance can be lower many cases (moreover most of the PSW users are located inside the buildings).

RLC/MAC Data Rate (2 TSLs)

0

20

40

60

80

100

120

-74 -76 -78 -80 -82 -84 -86 -88 -90 -92 -94 -96 -98 -100 -102 -104

RxLev (dBm)

kbps

RLC/MAC Data Rate (2M Download on 2 TSLs)

Figure 4 DL RLC/MAC throughput vs. Rx Lev (NTN)

The Figure 4 above shows the data rate dependency clearly based on signal level. The interference can further reduce the throughput with the same signal level.

4.1.2 Interference vs. TSL Data Rate


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The curve in the graph below shows the relation between C/I and RLC/MAC data rate based on NTN measurement results (Figure 5). The RxLev is –70 dBm, so the performance is limited by interference only (LA enabled).

C/I dependency (FTP Download on 2 TSLs)

0

20

40

60

80

100

120

36 34 32 30 28 26 24 22 20 18 16 15 14 13 12 11 10 9

C/I

kbps

RLC/MAC Data Rate (2M Download 2TSLs)

Figure 5 DL RLC/MAC throughput vs. interference in NTN

As it can be seen in the graph above the interference starts to be limiting factor from 24 dB. Between 24 and 14 dB there is a significant degradation in data rate and from 14 dB till 9 dB the Link Adaptation is choosing robust enough MCSs (MCS3 and MCS2) to stabilize the throughput on 20 kbps/TSL.

The curve in the graph above is based on averaged values from Application Tester logs.


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4.1.3 Signal Level and Interference vs. TSL Data Rate

In the above chapters the impact of signal level and interference were investigated separately. Here in this chapter the complex effect of GSM performance will be studied (mixture of RxLev and C/I).

RLC/MAC Data Rate (FTP Download on 2 TSLs)

0

20

40

60

80

100

120

-65 -70 -75 -80 -85 -90 -95 -100 -105

Signal level (dBm)

kbps

No Interference

C/I 25 dB

C/I 20 dB

C/I 15 dB

Figure 6 DL RLC/MAC throughput vs. interference and signal level in NTN

In city environment the indoor signal level is usually around –70 and - 90 dBm, while the C/I is around 15-25 dB. Therefore in worst case with –90 dBm signal level and 15 dB C/I the practically available data rate on two TSLs is around 50 kbps only, just based on GSM functionality.

4.2 Site Arrangement The TSL data rate can be improved if the signal level is raised. It can be achieved by tuning of the radio network elements, like antenna turning, space diversity improvement, uptilting, changing, usage of MHA, etc, etc.

This is a GSM optimization activity.

4.3 Frequency Plan The TSL data rate can be improved if the C/I is increased. If the site arrangement is optimized and the cells have dominant coverage areas, the C/I can be improved with better frequency allocation as well.

This is a GSM optimization activity.

4.4 Optimal GSM Network for PSW Services The optimal GSM network from PSW services point of view has:


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• As high signal level as possible

It means that even the indoor signal level should be high enough to have MCS9 for getting the highest data rate on RLC/MAC layer.

• As low interference as possible

The aim of having high C/I is to avoid throughput reduction based on interference.

• Enough capacity

Enough hardware capacity is needed to provide the required capacity for PSW services in time. Both CSW and PSW traffic management should be harmonized with the layer structure and long term plans.

• As few cell-reselection as possible

The dominant cell coverage is important to avoid unnecessary cell-reselections in mobility. The prudent PCU allocation can help to reduce the inter PCU cell reselections.

Dominant cell structure can help to maximize the signal level and reduce the interference, too.

• Features

All the features should be used which can improve the PSW service coverage, capacity and quality in general.


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5. Signaling Capacity Improvement The congestion and long delay on signaling can reduce the TBF establishment time. Therefore the signaling channels must be analyzed and optimized, if the TBF establishment is suffering from signaling channel bottlenecks.

The following interfaces and network elements must be analyzed and optimized for avoiding bottlenecks in signaling:

• Air interface

• TRXSIG

• PCU

• BCSU

• MM and SM signaling

5.1 Air Interface Signaling The air interface signaling optimization for avoiding signaling capacity bottlenecks is based on the PCH, AGCH, RACH and SDCCH analysis and modification.

5.1.1 PCH (NMO II)

On PCH the following counters and KPIs can be investigated:

5.1.1.1 Traffic Volume • Paging messages on air interface pgn_13

Total number of paging messages sent by BSC to air interface via a BTS. It is applicable on BTS level.

• Note: If GENA=Y then the counters cs_paging_msg_sent and ps_paging_msg_sent are not pegged at all.

• Number of CS paging commands sent via A c3000

• MAX_PAGING_BUFFER_CAPA c3035

5.1.1.2 Rejection • delete_paging_command (c3038) (includes both PS and CS paging)

5.1.1.3 Paging message deletion ratio • Paging message deletion ratio pgn_15

The ratio of deleted paging commands of the total amount of paging messages on the air interface.

5.1.1.4 Paging success ratio on PS (2G SGSN) sum(UNSUCC_PAGINGS(05002))


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• mob_sgsn141a = ----------------------------------------------------------------------* 100 sum(LLGMM_PAGING_ATTEMPTS (005003))

5.1.1.5 Solution for reducing PCH rejection and load The following activities can be done for better PCH functionality:

• Usage of combined structure • Modifying MFR and PER parameters • PBCCH implementation (in case of high (E)GPRS signaling traffic)

5.1.2 PCH (NMO I)

On PCH with NMO I the following counters and KPIs can be investigated:

5.1.2.1 Traffic Volume • cs_paging_msg_sent (c3058) (CS pagings from Gb)

• ps_paging_msg_sent (c3057) (PS pagings from Gb)

5.1.2.2 Congestion (CS + PS) • max_paging_gb_buf (003050)

5.1.2.3 Paging of MS in Packet Transfer Mode • Ratio of CS paging messages sent on PACCH pgn_14a

5.1.2.4 Gs Interface (2G SGSN) sum(DL_MESSAGES_DISCARDED_IN_GS(11000))

• Sgsn_961a = ----------------------------------------------------------------------- * 100

sum(CS_PAGING_MSGS + DL_TOM_MSGS)

5.1.3 AGCH

AGCH is used for Immediate Assignment messages. The following items can be investigated:

5.1.3.1 Traffic Volume (with Rejection) • imm_assgn_sent (c3001) - Imm Assign)

• imm_assgn_rej (c3002) - Imm Assign Rejected

• packet_immed_ass_msg (c72084) - P-Imm Assign

• packet_immed_ass_rej_msg (c72087) - P-Imm Assign


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5.1.3.2 Congestion packet_immed_ass_nack_msg blck_21b = ------------------------------------------------------------------------- packet_immed_ass_nack_msg + packet_immed_ass_ack_msg

5.1.3.3 Solution for reducing AGCH rejection and load The following activities can be done for better AGCH functionality:

• Usage of combined structure, modifying AG and CALC parameters

• Immediate Assignment messages are shared between PCH and AGCH

• PBCCH implementation (in case of high (E)GPRS signaling traffic)

Note that for GPRS & EGPRS, most of the Immediate Assignment messages are actually sent on the PCH and not on the AGCH.

In case of PCH and/or AGCH congestion LA/RA border and size planning, MSC paging parameters, CCCH configuration, CS paging load can be investigated to reduce CCCH load.

5.1.4 RACH

The counters and KPIs below can be investigated related to RACH functionality:

5.1.4.1 Load • rach_4 = 100 * avg(ave_rach_busy(C3014)/res_acc_denom3(c3015))

avg(ave_rach_slot(c3006)/res_acc_denom1(c3007))

5.1.4.2 Load and quality (repetitions of PS channel requests) • rach_9 = UL_TBF_WITH_RETRY_BIT_SET (c072020) / PACKET_CH_REQ (c072082)

5.1.4.3 Solution for reducing RACH rejection and load The following activities can be done for better RACH functionality:

• Usage of combined structure, modifying RET parameter

• PBCCH implementation (in case of high (E)GPRS signaling traffic)

5.1.5 SDCCH

The counters and KPIs below can be analyzed related to SDCCH functionality:

5.1.5.1 Traffic Volume • SDCCH seizure attempts (c1000)

• Average available SDCCH (ava_45a)

• Average SDCCH traffic trf_168

• Average SDCCH traffic trf_11b


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5.1.5.2 Congestion • Blocking on SDCCH, before FCS (blck_5)

• Blocking on SDCCH, after FCS (blck_5a)

• Time congestion on SDCCH (cngt_2)

5.1.5.3 Quality • SDCCH drop ratio without timer T3101 expiry % (sdr_4)

• Ghosts detected on SDCCH and other failures (sd_1b)

• SDCCH Drop % (sdr_1a)

5.1.5.4 Solution for reducing SDCCH load The following activities can be done for better SDCCH functionality:

• Increase of Periodic location update timer / Periodic RA update timer (PRAU) (it can be risky to change these parameters on network level)

• Increase of MS Reachable timer (MSRT)

• More SDCCH allocation and Dynamic SDCCH feature usage

• Combined RAU (NMO-I with Gs for (E)GPRS)

• (Resume feature decreases the amount of RAUs)

• LA/RA re-planning

5.1.6 Parameters

The descriptions of the parameters are used for RF signaling optimization is listed below:

• Number of Multiframes (MFR)

• With this parameter you define the number of multiframes between two transmissions of the same paging message to the MSs of the same paging group. (def 4)

• Number of Blocks for Access Grant Msg (AG)

• With this parameter you define the number of blocks reserved for access grant messages from the CCCH during the 51 TDMA frame (a multiframe). (def 1)

• Max Number of Retransmission (RET)

• With this parameter you define the maximum number of retransmissions on the RACH (random access channel) that the MS can perform. (def 4)


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• Calculation of Minimum Number of Slots (CALC)

• With this parameter you calculate the minimum number of slots between two successive Packet Channel Request messages. (def 30)

• Preferred BCCH TRX (PREF)

• With this parameter you mark one or more TRXs as preferred TRXs where the BCCH is reconfigured, if possible.

• Timer for Periodic MS Location Updating (PER)

• With this parameter you define the interval between periodic MS location updates. The value 0 means that the periodic location update is not used.

5.1.7 Features

The subsections below show the features, which can help to avoid signaling issues.

5.1.7.1 NMO1 with Gs Interface • In case of combined LAU/RAU the RA Update is generated without LA Update.

The time used for combined RAU is much less compared to uncombined LAU/RAU.

5.1.7.2 EPCR (S11, UltraSite, MS R99) with one phase access • EPCR is always on when BSS 11 is used and supported by MS Rel’99 onwards.

Ultrasite supports EPCR (CX4.0-x) and EDGE support required as well.

• If EDGE one phase access is used on CCCH, only one TS is allocated, so reallocation need is checked when establishment is completed.

• Nokia solution has PACKET RESOURCE REQUEST (PRR) implemented with one phase access.

5.1.7.3 Resume GPRS suspension procedure enables the network to suspend GPRS services packet flow in the downlink direction. When the terminal leaves the suspended mode (and CSW dedicated mode), the BSS shall signal to the SGSN that an MS's GPRS service shall be resumed.

Less signaling is generated, so more user data can be sent.

The counters related to Resume feature are listed below:

• 057049 GPRS_SUSPEND - Number of MS initiated GPRS suspension requests. • 057050 GPRS_SUSPEND_FAILURE - Number of unsuccessful GPRS

suspension procedures. • 057051 GPRS_RESUME GPRS - Number of BSC initiated GPRS resume

requests. • 057052 GPRS_RESUME_FAILURE - Number of unsuccessful GPRS resume

procedures. To check how much the Resume function has reduced the signaling, SGSN counters can be checked before and after S11.5 is loaded (check the amount of intra-PAPU routing area updates).


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5.1.8 TBF Establishment Failure

(E)GPRS TBF establishment failure ratio can be measured by tbf_66. This KPI is calculating the TBF establishments that have failed due to no response from MS.

5.2 TRXSIG The LAPD links are used for CSW and PSW signaling as well, so the congestion on TRXSIG can increase the connection time and reduce the reliability (the TRXSIG has important role in connection establishment).

(E)GPRS differs from GSM in that signaling information data packets can be transmitted on TRXSIG channel but also on PDTCH/PACCH traffic channel (16 kbit/s PCU frames, a derivative of TRAU frames). So the signaling on PDTCH/PACCH is not transmitted over TRXSIG.

The Abis LAPD link can be configured to 16Kbps, 32Kbps or 64Kbps. A bottleneck can be arise, as in some cases BTS processors can handle more messages than the Abis link can transfer.

In case of PBCCH implementation the (E)GPRS signaling is conveyed over PBCCH TSL, so the TRXSIG is used for CSW signaling only. PBCCH feature will be not available from S11.5 - PCU2 implementation.

The TRXSIG load measurement (based on MML scripts) description can be found in the link below:

https://sharenet-ims.inside.nokiasiemensnetworks.com/Download/368224953

5.3 PCU The PCU can be analyzed from processing and connectivity capacity point of view.

The processing capacity limits have alarms:

• Notification 0125 (90% load, PCU starts to reduce cell reselection calculations)

• Alarm 3164 (95% load, PCU starts to discard blocks)

While the connectivity capacity limits can be observed by KPIs (S11.5 onwards):

• UL MCS selection limited by PCU dap_10

• DL MCS selection limited by PCU dap_9

Both processing and connectivity related issues can be solved by better allocation of BCFs among PCUs. More information is available in Section 0.

5.4 BCSU The BCSU handles the LAPD (TRXSIG and OMUSIG) and SS7. From BSC load audit point of view the TRXSIG should be mainly taken into account.


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The ND 184 report contains the BSC Unit load per hour for each BSC. For processor units the average load of 70% is critical and the average of 60% should not be exceeded. For MB the average load should not exceed 50%. An example can be seen in Table 1.

Unit name and index Average load

(%)Min peak load

(%)Max peak load

(%)Peak hour

(YYYYMMDDHH)BCSU-0 0 1 1 2004120200BCSU-1 6.7 15 15 2004120215BCSU-2 7.01 17 17 2004120219BCSU-3 7.15 17 17 2004120218BCSU-4 7.15 17 17 2004120215BCSU-5 6.02 15 15 2004120219BCSU-6 5.26 14 14 2004120219BCSU-7 7.52 18 18 2004120215BCSU-8 8.07 20 20 2004120219MB-0 2.28 19 19 2004120214MCMU-0 8.95 79 79 2004120214MCMU-1 5.71 27 27 2004120214OMU-0 1.18 32 32 2004120215

Table 1 Network Doctor 184 report example

5.5 MM and SM Signaling Mobility Management (MM) and State Management (SM) signaling are used for attach, PDP context activation, RAU update, etc.

The capacity situation on RF signaling has impact on the success rate of MM and SM.

For BSS, there are KPIs which tell how many of all the established TBFs are used for MM and SM signaling:

• Ratio of DL signaling TBFs tbf_62

• Ratio of UL signaling TBFs tbf_61

If the TBF success rate is low (with high portion of MM and SM signaling TBFs), the quality of GPRS attach and PDP context activation will be degraded.

In addition, the amount of different procedures can be checked from the relevant tables in the SGSN:

• p_sgsn_mobility_management (Nokia SGSN)

• p_sgsn_session_management (Nokia SGSN)


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6. Resource Allocation Improvement The aim of resource allocation improvement is to ensure not only the fast access to the network but also the access to the right cells and TSLs, which provide the fastest data rate.

Usually the following items should be checked in BSS resource allocation improvement:

• PSW activation and territory settings

• Cell selection

• BTS selection

• TSL selection

6.1 PSW Activation and Territory Settings The aim of PSW activation procedure and territory setting is to provide enough capacity to PSW traffic and provide the appropriate balance between CSW and PSW traffic.

The TRX, cell (segment) are used for signaling, CSW traffic, Free TSLs and PSW traffic.

TRX 1

TRX 2

BCCH TS TS TS TS TS TS

TS TS T TS TSTS

SDCCH

TS TSS

TS

TS

BCCH

= (E)GPRS Traffic

= CSW Traffic

= Signaling

TS = Free TSL for CSW

TRX 1

TRX 2


TS TS T TS TSTS

SDCCH

TS TSS

TS

TS

BCCH

= (E)GPRS Traffic

= CSW Traffic

= Signaling



TS TS T TS TSTS

SDCCH

TS TSS

TS

TS

BCCH

= (E)GPRS Traffic

= CSW Traffic

= Signaling


7. Figure TSL Occupation

6.1.1 Parameters

The PSW activation and territory can be optimized by the following parameters:

PSW Activation

• GPRS Enabled (GENA)

• EGPRS Enabled (EGENA)


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• GPRS Enabled TRX (GTRX)

• Adjacent GPRS Enabled (AGENA)

• GPRS Cell Barred (GBAR)

• Not Allowed Access Classes (ACC)

• GPRS Not Allowed Access Classes (GACC)

Territory Settings

• Default GPRS Capacity (CDEF)

• Dedicated GPRS Capacity (CDED)

• MAX GPRS Capacity (CMAX)

Channel Allocation Parameters

• Prefer BCCH frequency GPRS (BFG)

• TRX priority in TCH allocation (TRP)

6.1.2 Measurements – KPIs

The following counters and KPIs can be used to analyze the territory related situation on a cell and a BTS level.

Actual Territory

• ava_44

• Peak PS territory (c2063)

Recommendation: Ava_44 and c2063 can be compared with the CDEF settings. If too big difference, then CDEF should perhaps be changed, or more capacity should be added to the cell.

Multislot Blocking

• DL multislot blocking – soft (blck_33a) (Request counters are updated according to MS capabilities, so they are not indicating, what PCU is requesting, but what MS is capable)

• UL / DL multislot allocation blocking – hard (tbf_15a, tbf_16a)

TSL Sharing

• UL / DL timeslot sharing – TBFs pr time slot (tbf_37c, tbf_38c)

Recommendation: Too much sharing shows that the territory is perhaps not enough.


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Impact of PSW territory upgrades/downgrades on CSW

• ho_61

Recommendation: Too much CSW HOs (because of PSW territory upgrades/downgrades) shows that the territory is perhaps not enough, which generates instability to CSW, too.

6.2 Cell (Re)-Selection The terminals must be allocated to that cell, where the maximized TSL data rate and territory are available.

If low data rate and/or limited territory generate low user throughput, the optimized cell selection can be a solution among many others.

In cell selection the C1, C2 and NCCR parameters are taken into account.

6.2.1 C1 and C2 and HYS

The allocation decision is always based on received level average (RLA_P) for each of the carriers in BA (GPRS).

In C1 the following parameters must be observed:

Rxlev Access Min (RXP)MS TXPWR Max CCH (TXP1)MS TXPWR Max CCH1x00 (TXP2)

The too low RXP will generate high retransmission, but probably less unexpected TBF release.

TXP1 is used for 800/900 MHz, while TXP2 is used for 1800/1900 MHz.

C2 parameters are used to push slow moving users to the cells with less cell size but probably better signal level, C/l and capacity, so the user data rate can be increased (because of higher TSL RLC/MAC data rate and bigger territory) on micro and pico cells.

The following parameters are used in C2 implementation:

Cell reselect offset (REO)Temporary Offset (TEO)Penalty Time (PET)


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M a c ro 9 0 0 “ A "

M a c ro 9 0 0 “C ”

M ic ro 9 0 0 “ D ”

M a c ro 1 8 0 0 “B ”

8. Figure C2 parameters’ usage in multilayer networ k environment

6.2.2 Cell re-selection Measurements (NC_0)

The following KPIs tell how often a TBF is interrupted due to a cell re-selection.

• tbf_63

• tbf_64

This is calculated on the source cell, there is no information of where the target is, so it is not possible to distinguish between e.g. C2 and C31/C32 effects.

The duration and thereby the impact on the applications are not known.

The following parameter shows the number of NACC usage to assist MS in network control mode 0.

• c95017 (NACC_WITH_NC0)

Drive tests are needed to measure cell re-selection behavior properly.

6.3 NCCR NCCR (Network Controlled Cell Reselection) enables the network to control the resource allocation when the MS performs the cell reselection.

NCCR is an optional feature in Nokia BSC. Operator can enable/disable the feature on BSC level.

Benefits with NCCR are the efficient allocation of resources:

• EDGE MS can be held on EDGE TRX longer => better throughput for EDGE MS.

• GPRS MS can be prevented to access an EDGE TRX => better throughput for EDGE MS.


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The better control over mobile stations is possible and more counter statistics helps in detailed analysis.

Network Control Mode (NCM) defines how cell re-selection is performed:

Network Control Mode = 0 (NC0): the MS will perform an autonomous cell reselection.

Network Control Mode = 1 (NC1): it is not supported.

Network Control Mode = 2 (NC2): the MS sends neighbour cell measurements to the network and the network commands the MS to perform cell re-selection (NCM is modified with MML command ZEEM).

MS PCU

cell update

FLUSH-LL

SGSN

C1, C2, C31 or C32 criterion triggers

MS PCU

cell update

FLUSH-LL

SGSN

NCCR triggers

PACKET ENHANCED MEASUREMENT REPORT

PACKET CELL CHANGE ORDER

Autonomous MS cell reselection

Network controlled cell reselection

9. Figure Flow chart – NC0 and NC2


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6.3.1 NCCR Criteria

The following points summaries the NCCR criteria:

• Power budget push EGPRS capable MSs to EGPRS cells and non-EGPRS capable MSs to non-EGPRS capable cells. This feature can also be useful in e.g. non-EDGE networks!

• Quality Control (without EQoS) triggers NCCR when the serving cell transmission quality drops even if the serving cell signal level is good.

• Quality Control (with EQoS) PFC downgrade and deletion actions are used, too.

• Coverage based ISNCCR selects 3G network as soon as it is available or when GSM coverage ends, depending on operator choice.

• Service based ISNCCR selects 3G network according to SGSN Service UTRAN CCO BSSGP procedure if the serving cell signal level is good. Feature candidate for S14.

6.3.2 NCCR – Power Budget

With NCCR Power Budget parameters it is possible to:

• push EGPRS capable MSs to EGPRS cells

• push non-EGPRS capable MSs to non-EGPRS capable cells

• delay MSs entrance into a cell

• avoid moving MSs unnecessary entrance into cells they only briefly pass

NCCR EGPRS PBGT margin (EPM) and NCCR GPRS PBGT margin (GPM) can be used to effectively allocate EDGE and GPRS capable MSs on different cells.

GPRS temporary offset (GTEO) and GPRS Penalty Time (GPET) can be used to avoid unnecessary cell reselection from moving MS to cells they briefly pass. E.g. Pico cells.

Priority Class (PRC) and HCS signal level threshold (HCS) should be used carefully! Preferably not used at all! Wrongly used they can increase ping-ponging and decrease network performance.

6.3.3 NCCR – Quality Control

The purpose of Quality Control (QC) in BSS11.5 onwards is to monitor and detect degradation periods in service quality, and to perform corrective actions to remove the service degradation. The possible actions in BSS11.5 include TBF reallocation and network controlled cell reselection.

NCCR is triggered only if the NCCR feature is active. NCCR activity is controlled by a BSC level parameter NCCR control mode.


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The Quality Control shall maintain statistics about BLER for each TBF as well as bitrate per radio block for each TBF in RLC ACK mode. QC uses this information for monitoring radio link performance and delay.

The monitored samples are filtered. The filtering is based on appropriate threshold values:

• For BLER sample filtering, the threshold value is operator parameter maximum BLER in acknowledged mode (BLA) or maximum BLER in unacknowledged mode (BLU), depending on the RLC mode of the TBF.

• For bitrate per radio block sample filtering, the threshold value is one of the four operator parameters QC GPRS DL/UL RLC Ack Throughput Threshold or QC EGPRS DL/UL RLC Ack Throughput Threshold, depending on the type and mode of the TBF, multiplied with e.g. 1.2 in order to have a safety margin of some degree during the first calculation cycles.

6.3.3.1 Block Error Rate (BLER) RLC shall report to QC the BLER statistics - number of correctly transmitted RLC data blocks and number of RLC data blocks actually needed to transmit the correct blocks - for all TBFs, independently for UL and DL, and RLC ACK and UNACK mode. Based on BLER information provided by RLC, QC shall calculate and maintain the actual BLER values for each RAT, independently for UL and DL, and RLC ACK and UNACK mode.

The BLER definition in GPRS is straightforward, as the RLC block reception is an independent event. Thus, the BLER in GPRS is the probability of any RLC block received incorrectly. On the contrary in EGPRS with Incremental Redundancy, the reception of a retransmitted RLC block is not an independent event, but depends on the previous receptions of the same block. Thus, the BLER definition in EGPRS must be more general. However, the following formula is justified in both cases:

,1_

_

onstransmissineeded

blockscorrect

N

NBLER −=

where blockscorrectN _ is the number of RLC data blocks received correctly in the reporting

period, and onstransmissineededN _ is the number of transmissions needed for correct receptions

(initial transmission + retransmissions). This definition is valid for both GPRS and EGPRS.

6.3.3.2 BLER Degradation Duration Counter QC shall maintain the BLER degradation duration counter for each TBF according to the following rules:

- The BLER degradation duration counter shall be incremented by 10, if

(%)_(%)_ BLERMeasuredBLERMAX < ;

- the counter shall not be modified, if

(%)_(%)_(%)_ BLERMAXBLERMeasuredBLERMAX ≤≤ ;

- The counter shall be cleared (set to zero), if (%)_(%)_ BLERMAXBLERMeasured < .

The QC thread shall monitor the BLER degradation duration counter, and if the counter is larger than predefined triggering levels (BLA, BLU parameters), the corresponding corrective action is tried.


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6.3.3.3 Bitrate (BER) QC shall monitor bitrate per radio block for each TBF in RLC ACK mode, for UL and DL separately. The statistic is gathered by RLC, and reported to QC. RLC shall calculate and report values in the following way:

• In downlink, RLC shall maintain counters for transmitted bits (only the payload bits in each RLC data block are taken into account) and transmitted radio blocks. The counter for transmitted bits shall contain only new RLC data block transmissions; for the retransmissions, the number of bits transmitted is zero. Pending ACK retransmissions as well as the RLC data blocks containing only an LLC dummy block, but no real data, shall be ignored in this calculation.

• In uplink, RLC shall maintain counters for received RLC data block payload bits and received radio blocks. When a radio block is received, the counter of received radio block is increased by one. If the RLC data block(s) is/are received correctly, RLC shall update the counter of the received RLC data block payload bits accordingly. If RLC data block(s) is/are received incorrectly, the number of received payload bits is zero. Radio blocks containing only pending ACK retransmission(s) shall be ignored in this calculation.

QC shall calculate the bitrate per radio block value once in its execution cycle (200 ms) and check it against the corresponding threshold value. Since the unit of the threshold values is kbit/s, QC shall convert RLC reported bitrate per radio block by dividing the values with 20 ms (1 block period corresponds 20 ms). Thus the value range of QC calculated bitrate per radio block is from 0 kbit/s to 59,2 kbit/s.

The threshold values are operator parameters and there is a separate value for UL and DL, as well as for GPRS and EGPRS, respectively (look at operator parameters QC GPRS DL/UL RLC Ack Throughput Threshold (QGDRT, QGURT) and QC EGPRS DL/UL RLC Ack Throughput Threshold (QEDRT, QEURT)).

Note. Bitrate per radio block monitoring algorithm does not measure the actual throughput. The algorithm does not take into account the time between samples received from RLC, and thus cannot calculate the real throughput: the output of the algorithm merely describes the quality of the measured TBF in terms of bits it can theoretically transfer per second.

6.3.3.4 Bitrate per Radio Block Degradation Duration Counter The bitrate per radio block degradation duration counter shall be maintained for each RAT according to the following rules:

- The bitrate per radio block degradation duration counter shall be incremented by 10, when the bitrate per radio block is below the threshold value.

- The counter shall be cleared (set to zero), when the bitrate per radio block is above or equal to the threshold value.

The QC thread shall monitor the bitrate per radio block degradation duration counter. If the counter is larger than predefined triggering levels (QGDRT, QGURT and QEDRT, QEURT parameters), the corresponding corrective action is tried.

6.3.3.5 Corrective Actions When any of the degradation duration counters monitored by QC gets larger than a predefined action trigger threshold, QC shall try to corresponding corrective action in


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background thread, running with low priority. Each action shall be triggered only once for a TBF in QC (once for a call (UL+DL TBFs of the same phone) during one degradation period. If the degradation period ends and a new starts, new actions can be tried). For example, if reallocation is already done, next action to be performed is NCCR, triggered when a degradation duration counter exceeds the NCCR trigger threshold. The flags of already performed actions shall be cleared when the degradation ends, i.e. when all the degradation duration counters are cleared.

The action trigger thresholds are expressed in block periods and the values can be set by operator, see operator parameters QC Action Trigger Threshold:

• QC reallocation action trigger threshold (QCATR)

• QC NCCR action trigger threshold (QCATN)

• QC QoS renegotiation action trigger threshold (QCATQ) (not implemented in S11.5)

• QC drop action trigger threshold (QCATD) (not implemented in S11.5)

It is possible to change the order of different actions by modifying the action trigger threshold values (If the value is set to 0, then no action of that kind is tried).

6.3.4 NCCR Parameters with Power Budget and Quality Control

The following parameters are used to set the NCCR:

• NCCR Control Mode (NCM)

• WCDMA FDD NCCR Enabled (WFNE)

• NCCR Idle Mode Reporting Period (NIRP)

• NCCR Transfer Mode Reporting Period (NTRP)

• NCCR RxLev Transfer Mode Window Size (NRTW)

• NCCR Rxlev Idle Mode Window Size (NRIW)

• NCCR number of zero results (NNZR)

• NCCR Return to Old Cell Time (NOCT)

• NCCR Neighbor Cell Penalty (NNCP)

• NCCR Target Cell Penalty Time (NTPT)

• NCCR EGPRS PBGT margin (EPM)

• NCCR GPRS PBGT margin (GPM)

• NCCR streaming TBF offset (NSTO) (available only if EQoS exists)

• NCCR other PCU cell offset (NOPO)

• NCCR GPRS quality margin (GQM)


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• NCCR EGPRS quality margin (EQM)

• ISNCCR FDD quality threshold (FQT)

Quality Control

• Maximum BLER in acknowledged mode (BLA)

• Maximum BLER in unacknowledged mode (BLU)

• QC GPRS DLRLC Ack Throughput Threshold (QGDRT)

• QC GPRS DL RLC Ack Throughput Threshold (QGURT)

• QC EGPRS DL RLC Ack Throughput Threshold (QEDRT)

• QC EGPRS UL RLC Ack Throughput Threshold (QEURT)

• NCCR_NON_DRX_PERIOD

• NCCR_STOP_UL_SCHEDULING

• NCCR_STOP_DL_SCHEDULING

• NCCR_MEAS_REPORT_TYPE

• BSSGP_T5

• BSSGP_RAC_UPDATE_RETRIES

6.3.5 Cell re-selection Measurements (NC_2)

The following KPIs show the NCCR functionality.

• Nccr_12: Number of network controlled cell reselections compared to data amount

• Nccr_13: Successful NCCR ratio

• Nccr_14: Average duration of successful NCCRs

The following parameter shows the number of NACC usage to assist MS in network control mode 2.

• c95018 (NACC_WITH_NC2)

QC triggers actions (reallocations/NCCR) due to RB bitrate if measured radio block bitrate stays under configured thresholds (QC EGPRS DL RLC ack throughput threshold (QEDRT), QC EGPRS UL RLC ack throughput threshold (QEURT), QC GPRS DL RLC ack throughput (QGDRT), QC GPRS UL RLC ack throughput (QGURT)). Default values for the parameters are 10, 10, 6 and 6 kbit/s, correspondingly. It seems that the QC action is triggered too sensitively with the default parameter setup, so the mentioned parameter values could be lowered.


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Because the NCCR_QC_TRIG_NO_GOOD_NEIG counter used in nccr_13 seems to be triggered heavily, the nccr_13 will shows bad figures. NCCR_QC_TRIG_NO_GOOD_NEIG counter upgrade can be reduced, if the QC parameter setup has lower values.

6.4 BTS Selection in Segment (MultiBCF and CBCCH) The right BTS (with the maximized TSL data rate and territory) must be selected if MultiBCF or CBCCH are used. So the GPRS capable mobiles can be allocated to BTS with GPRS, while the EGPRS capable terminals are allocated to the EGPRS capable BTS inside the segment.

If EDGE and non-EDGE TRXs are mixed in same BTS, BB Hopping requires segment solution and own hopping groups. (EDGE cannot move to non-EDGE TRX).

6.4.1 Parameters

The following parameters have impact on allocation algorithm:

• NonBCCHLayerOffset (NBL Offset)

• Direct GPRS Access Threshold (DIRE)

• BTS Load in SEG (LSEG)

• TBF Load Guard Threshold

• GPRS non BCCH Layer Rxlev Upper Limit (GPU)

• GPRS non BCCH Layer Rxlev Lower Limit (GPL)

6.4.2 Measurements

Most of the GPRS/EDGE KPIs are on BTS level. E.g. the payload and Erlang formulas can be used to see how the different BTSs inside the segment are used:

• Downlink GPRS RLC payload trf_213c

• Downlink GPRS Erlangs trf_208c

• Uplink GPRS RLC payload trf_212c

• Uplink GPRS Erlangs trf_205d

• Downlink EGPRS RLC payload trf_215a

• Downlink EGPRS Erlangs trf_162g

• Uplink EGPRS RLC payload trf_214b

• Uplink EGPRS Erlangs trf_161i


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• PS Erlangs trf_237d

From S11.5 onwards, it can be checked if EDGE TBFs ends in GPRS territory (OSS4):

• DL EDGE TBFs in non-EDGE territory tbf_60

• UL EDGE TBFs in non-EDGE territory tbf_59

And if EDGE territory is “wasted” on GPRS TBFs:

• tbf_57a = UL_GPRS_TBF_IN_EGPRS_TERR / (UPLINK_TBF - EGPRS_TBFS_UL)

• tbf_58a = DL_GPRS_TBF_IN_EGPRS_TERR / (DOWNLINK_TBF - EGPRS_TBFS_DL)

The NBL offset parameter has probably the biggest impact on the BTS selection, if the capacity is not limited. As it can be seen from the NBL measurement below, the average NBL offset value for the whole network is not a good solution.

NBL Measurements

0

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LSANCA0106XLSANCA0106YLSANCA0106ZLSANCA0109XLSANCA0109Y

Figure 10 NBL measurement results (example)

The CBCCH Optimization Guidelines describes the Multi BCF planning in details:

https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/394442290

6.5 Scheduling (TSL Selection with Priority based QoS) The calculation of the load of TSLs is done by the PCU and based on the Priority based QoS parameters and different penalties given to the TSLs (PACCH, timeslot type and GPRS/EGPRS multiplexing).


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6.5.1 Parameters

The following parameters are used to set the TSL usage:

• DHP (DL high priority SSS)

• DNP (DL normal priority SSS)

• DLP (DL low priority SSS)

• UP1 (UL priority 1 SSS)




Sequence can be set by TBF Load Guard Threshold parameter.

6.6 DAP Resource Allocation in PCU1 No EDAP resource sharing algorithm is needed in that case where the number of slave channels required by the PS calls is lower than the EDAP capacity. This means that all the requests are served.

EDAP resource sharing algorithm is needed in that case where the number of slave channels required by the PS calls is higher (13 channels) than the EDAP capacity (12 channels). This means that the last requested call, with MCS-7 requires 3 slave channels, which could not be served by the existent EDAP: they cannot be allocated in the configured EDAP.

An MCS adjustment (a downgrade in DL and a transmission turn skipped in UL) is needed and the biggest MCS available with the restricted slave amount will be granted for the RLC by the Dynamic Abis Manager.

RTSLRequestsTRX 1

0 1 2 3 4 5 6 70 1 2 3 4 5 6 7

- - CS-2 MCS-5 MCS-9 MCS-8 MCS-1 MCS-7- - CS-2 MCS-5 MCS-9 MCS-8 MCS-1 MCS-7

5 5

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11. Figure EDAP resource sharing Example


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EDAP congestion situation in DL data transfer is handled differently in PCU1 than in PCU2. PCU1 reduces MCS for all MSs whereas PCU2 is recycling the EDAP resources between MSs.

If PCU1 can not allocate requested EDAP resources for all scheduled TBFs in DL direction, then requested EDAP resources are decreased evenly for all scheduled TBFs until requested EDAP resources match with available EDAP resources. In case of lack of EDAP resources some of the TBFs are totally left outside of the slave channel allocation. However, the 16 kbit/s EGPRS master channel can and shall be used for those TBFs – this guarantees CS-1 and MCS-1 usage.

For example, if there is one EDAP sized one TSL and two MSs are trying to transfer data with MCS-9, then MCS is reduced to MCS-6 for both MSs.


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7. Connectivity Capacity Optimization The aim of connectivity capacity optimization is to re-plan CDEF and EDAP size and reallocate the sites (BCFs) among PCUs (BSCs) for avoiding connectivity limits and maximizing QoS.

The view here is on the E2E chain (MS-SGSN), so all the network elements and interfaces are optimized for enough connectivity capacity.

The number of required PCUs is CDEF (with additional territory, if there is any) and DAP size dependent from physical layer point of view, while the amount of Gb links used by PCUs is PAPU limiting factor (or the limited number of PAPUs can limit the number of PCUs, because of Gb link limits in PAPU).

7.1 Connectivity Limits in PCU The following table shows the limiting factors in case of different PCU types.

PCU Type BSC Types Network elements BSS10.5 BSS10.5 ED BSS11 BSS11.5PCU BSCE, BSC2, BSCi, BSC2i BTS 64 64 64 64

TRX 128 128 128 128Radio TSLs 256 256 256 128Abis 16 kbps channels 256 256 256 256Gb 64 kbps channels 31 31 31 31

PCU-S BSCE, BSC2, BSCi, BSC2i BTS 64 64 64 64TRX 128 128 128 128Radio TSLs 256 256 256 128Abis 16 kbps channels 256 256 256 256Gb 64 kbps channels 31 31 31 31

PCU-T BSCE, BSC2, BSCi, BSC2i BTS 64 64 64 64TRX 128 128 128 128Radio TSLs 256 256 256 256Abis 16 kbps channels 256 256 256 256Gb 64 kbps channels 31 31 31 31

PCU2-U BSCE, BSC2, BSCi, BSC2i BTS N/A N/A N/A 128TRX N/A N/A N/A 256Radio TSLs N/A N/A N/A 256Abis 16 kbps channels N/A N/A N/A 256Gb 64 kbps channels N/A N/A N/A 31

PCU-B BSC3i BTS 2 x 64 2 x 64 2 x 64 2 x 64TRX 2 x 128 2 x 128 2 x 128 2 x 128Radio TSLs 2 x 256 2 x 256 2 x 256 2 x 256Abis 16 kbps channels 2 x 256 2 x 256 2 x 256 2 x 256Gb 64 kbps channels 2 x 31 2 x 31 2 x 31 2 x 31

PCU2-D BSC3i BTS N/A N/A N/A 2 x 128TRX N/A N/A N/A 2 x 256Radio TSLs N/A N/A N/A 2 x 256Abis 16 kbps channels N/A N/A N/A 2 x 256Gb 64 kbps channels N/A N/A N/A 2 x 31

2. Table Limiting factors of PCUs

7.1.1 Connectivity Limits in SGSN and PAPU (SG6)

The following limits must be taken into account in connectivity capacity optimization:


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• The available 240 E1/T1 can be freely allocated between the Gb and the SS7-based interfaces

• The maximum number of supported network service entities (NSE) per PAPU (or PAPU group) is 512

• Maximum number of FR NS-VCs in PAPU = 512*4 = 2048 (DLCI/CIR limit 992) • One AS7-C supports 8 times 2Mbps PCMs (32*64kbps). 2Mbps is achieved both for

Uplink and Downlink (2M UP + 2M DL). • Maximum number of AS7-C per PAPU = 2 in all PAPUs ( 16 E1/PCM per papu ),

meaning 240 E1 per SG6 in full configuration for 2G => 240 E1 => 7680 TSL • Maximum of 3 AS7-C per PAPU when having small configuration (up to 5 PAPUs),

meaning up to 24 E1 per papu = >120 E1 per SGSN in this config => 3840 TSL • The maximum number of supported BSSGP virtual connections (cells / BVCIs) per

PAPU ( or papu group) is 12 000, and the Nokia SGSN supports up to 48 000 BVCIs. The SGSN supports up to 3000 2G routing areas and up to 2000 location areas (LAs), which can be freely allocated across the PAPU/SGSN boundaries

7.1.2 Connectivity Capacity Optimization – Maximized Capacity

The connectivity optimization for maximum capacity is based on the proper set of CDEF and DAP size.

To provide enough capacity for territory upgrade the 75 % utilization in the connectivity limits is recommended by Nokia (75% is not valid if the operator decides to set CDEF=1% in all cells in order to save PCU capacity, because then the margin needs to be higher), therefore the following limits must be taken into account in optimization:

Outputs Max limit* Utilization Limit unitAbis channles (radio TSLs) 256 75% 192 TSLsEDAP pools 16 75% 12 pcsBTS (cell, segment) 64 75% 48 pcsTRXs 128 75% 96 pcs*PCU & PCU-S handle 128 radio TSLs only with S11.5

*PBCCH is not implemented

Table 3 PCU Connectivity capacity limits

• The CDEF is allocated to the cells (BTSs in segment), so the too big CDEF territory will need more PCUs.

• The Dynamic Abis Pool (DAP) is allocated to the sites (BCFs). Higher DAP size provides more MCS9 capable TSLs on air interfaces, but on the other side, higher DAP size needs more capacity on E1s and more PCUs as well.

So the proper value of CDEF on cell (BTS) level and DAP on BCF level can help to be below the 192 radio TSL limit (with 75 % utilization) to avoid connectivity bottlenecks even in case of territory upgrades.

It is important to know that the PCU and PCU-S have 128 radio TSL limit with S11.5, which can be a real bottleneck in GPRS only networks.

7.1.3 Connectivity Capacity Optimization – Maximized Data Rate

The maximized data rate needs proper utilization of PCUs, so the following considerations must be taken into account:


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• The proper DSP allocation in PCU requires additional considerations, because the maximized data rate (200 kbps) can be achieved for 4 TSL (E)GPRS users in case of multiplexing with GPRS, if the number of connected radio TSLs to one PCU is not more than 64. This limit will not be valid with S11.5 PCU2.

• In mixed GPRS/EGPRS networks the DAP usually eats the Abis channels (256 TSLs as limit for one PCU), so the average number of radio TSLs is usually less than 64 TSLs in dense network environment.

The number of EDAP pools depends on EDAP size, territory size and number of cells per EDAP, however the theoretical maximum is 16 for connectivity.

In the live networks the balance between investment and QoS is the most important question, so the aim is to find the compromised solution between data rate and connectivity.

7.1.4 Connectivity Limit related Measurements - KPIs

The TSL data rate cannot be maximized, because of connectivity limits on EDAP and PCU:

o DL MCS selection limited by EDAP dap_7b

o UL MCS selection limited by EDAP dap_8c

• DL_TBFS_WITHOUT_EDAP_RES (c076007)

• DL_TBFS_WITH_INADEQ_EDAP_RES (c076008)

The EDAP related counter functionality can lead to excessive pegging of c076007 and c076008 even in situation where EDAP size is adequate. Estimated increase with EDAP blocking counters (in case there is adequate EDAP size) is around 2% of all allocations. This additional blocking is real blocking caused by S11.5 DAP slave channel reservation and will be corrected in near future. It will be corrected in CD4.1.

o DL MCS selection limited by PCU dap_9

o UL MCS selection limited by PCU dap_10

o DL inadequate EDAP channel time (dap_4)

o EDAP congestion ratio (dap_5)

o Peak DL EDAP usage (c76004)

• Territory upgrade rejection due to lack of PCU capacity (blck_32)


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8. RLC/MAC TSL Data Rate Maximization The following features, parameters and events are studied below for maximizing TSL data rate:

• TSL Utilization

• TBF Release Delay, TBF Release Delay Extended and BS_CV_MAX

• Link Adaptation and Incremental Redundancy

• Multiplexing

• UL Power Control

• Multislot Usage

The maximization is achieved by (E)GPRS related parameters’ modification only, because the GSM network’s performance is already improved based on Chapter Error! Reference source not found. items.

The TSL date rate can be maximized if:

• There is not any connectivity limitation;

All the interfaces and network elements are having enough capacity.

• There is not any functionality limitation;

E.g. the flow control parameters are set properly or the DSP allocation of PCU is working properly

• The PSW calls are allocated to the most appropriate layer;

The signal level, C/I and capacity are providing good environment for maximized data rate.

• The TBFs are established as fast as possible;

The proper parameter setting is needed to achieve fast TBF establishment

• The retransmission ratio is optimized;

The higher retransmission with MCS9 can generate higher RLC/MAC data rate compared to lower retransmission with MSC6. So the higher retransmission does not mean higher throughput for sure. So the target here is to find the balance between MCSs (CSs) and retransmission.


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8.1 TLS utilization The TSL utilization can be increased by the setting or usage of the following items:

• Acknowledgement Request

• Pre-emptive transmission

• One Phase Access with EPCR

8.1.1 Acknowledge Request

The Acknowledge Request parameters are used by the RLC acknowledgement algorithm to determine how frequently the PCU polls the mobile station having a DL TBF in EGPRS mode. The PCU has a counter, which is incremented by one whenever an RLC data block is transmitted for the first time or retransmitted pre-emptively.

In case of EGPRS Downlink traffic the counter is incremented by (1 + EGPRS_DOWNLINK_PENALTY) whenever a negatively acknowledged RLC data block is retransmitted. The mobile station is polled when the counter exceeds the threshold value of EGPRS_DOWNLINK_THRESHOLD.

All the Acknowledge Request parameters are listed below:

• GPRS Uplink Penalty (Recommendation: 1)

• GPRS Uplink Threshold (Recommendation: 19)

• GPRS Downlink Penalty (Recommendation: 1)

• GPRS Downlink Threshold (Recommendation: 19)

• EGPRS Uplink Penalty (Recommendation: 1)

• EGPRS Uplink Threshold (Recommendation: 19)

• EGPRS Downlink Penalty (Recommendation: 1)

• EGPRS Downlink Threshold (Recommendation: 19)

8.1.2 Pre-Emptive Transmission

PRE_EMPTIVE_TRANSMISSIO

If the pre-emptive transmission bit is set to '1‘ (The mobile station shall use pre-emptive transmission) in the PACKET UPLINK ACK/NACK message and there are no further RLC data blocks available for transmission, the sending side shall transmit the oldest RLC data block which is in PENDING_ACK state.

Default value allows pre-emptive re-transmission.


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8.1.3 UL TBF Assignment with One / Two Phase Access and EPCR

When CCCH is in use, the Uplink Establishment offers:

• GPRS: one-phase access is possible, but only 1 TSL can be allocated to the TBF. Timeslot reconfiguration would be needed for multi slot allocation

• EGPRS: one-phase access is possible only if “EGPRS Packet Channel Request” (EPCR) is supported by the network.

The benefit of one-phase access compared to two-phase access:

• One phase access Packet Resource Request (PRR) will be sent faster than in two phase access

• One phase – next USF is used for PRR message

Typical delay between Immediate Assignment and PRR few milliseconds only

• Two phase – MS will send PRR and ARAC messages within given single/mutiblock allocation

Typical delay between Immediate Assignment and PRR few hundred milliseconds

8.1.4 EPCR

EPCR is always on when BSS 11 is used and supported by MS Rel’99 onwards. Ultrasite supports EPCR (CX4.0-x) and EDGE support required as well.

One TS is allocated when EDGE one phase access is used on CCCH, so reallocation need is checked when establishment is completed.

Nokia solution has PACKET RESOURCE REQUEST (PRR) implemented with one phase access.

8.1.5 TBF Release Delay, TBF Release Delay Ext and BS_CV_MAX

The TBF Release Delay, TBF Release Delay Extended and BS_CV_MAX parameters are used to achieve faster data rate.

8.1.5.1 DL_TBF_RELEASE_DELAY (0,1-5sec, def 1s) This parameter is used to adjust the delay in downlink TBF release. An appropriate delay time increases the system performance, since the possibly following uplink TBF can be established faster, and frequent releases and re-establishments of downlink TBF can be avoided.

When the MS wants to send data or upper layer signaling messages to the network, it requests the establishment of an uplink TBF from the BSC. There are the following main alternatives for the TBF establishment:

• on PACCH; used when a concurrent DL TBF exists


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The UL TBF establishment is faster if there is a concurrent DL TBF, therefore the longer delay in DL TBF Release can help to have faster signaling and finally faster data rate.

• on CCCH; used when there is no concurrent DL TBF

The faster UL TBF establishment can be achieved by using PACCH.

But during the release phase, the TBF is kept alive based on sending DL dummy blocks in DL TBF (Polling the mobile, at least one time every 360 ms).

8.1.5.2 UL_TBF_RELEASE_DELAY (0,1-3sec, def 0,5s) This parameter is used to adjust the delay in uplink TBF release. An appropriate delay time increases the system performance, since the possibly following downlink TBF can be established faster.

The DL TBF establishment obviously takes time and done in one of the following ways:

• on PACCH; used when 1.) concurrent UL TBF exists or 2.) when the timer T3192 is running in the MS

1.) The effect of UL TBF release delay is taken into account when there is no concurrent DL TBF for the same MS. The purpose of the delay is to speed up the possibly following DL TBF establishment. No USF turns are scheduled during this delay. The establishment is done with a PACKET_DOWNLINK_ASSIGNMENT or PACKET_TIMESLOT_RECONFIGURE message.

2.) When the DL TBF is released, the MS starts the timer T3192 and continues monitoring the PACCH of the released TBF until T3192 expires. During the timer T3192 the PCU makes the establishment of a new DL TBF by sending a PACKET_DOWNLINK_ASSIGNMENT on the PACCH of the 'old' DL TBF.

• on CCCH; used when T3192 is not running

The faster DL TBF establishment can be achieved by using PACCH.

But during the release phase, the TBF is kept alive based on sending PACKET UL ACK/NACK in UL TBF.

According to test measurement results HTTP prefers it but PoC does not prefer TBF Release Delay.

8.1.5.3 Extended UL TBF Mode (EUTM) EUTM is Rel4 feature - MS support and NW-support required. If EUTM is activated the UL TBF Release parameter is ignored.

When PCU does not know MS EUTM support (GPRS one-phase access on CCCH, short access on CCCH)

• the PCU schedules USF to MS when EUTM capability is not known

• based on MS behavior PCU concludes EUTM support

otherwise UL TBF release done immediately (concurrent DL TBF) or delayed UL TBF release is used.


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8.1.5.4 BS_CV_MAX The most important functionalities of BS_CV_MAX parameter from network planning point of view is described in [1].

Recommended value: 9

Basically the BS_CV_MAX parameter should define the RLC round-trip delay in block periods.

• If the BS_CV_MAX parameter has too high value (e.g. 15), then the mobile may ignore some nacks that would require retransmissions. So in some cases a block has to be nacked twice before the mobile is willing to make the retransmission. This may reduce the performance slightly.

• On the other hand, if the BS_CV_MAX parameter is too large or if the mobile is not able to do accurate time stamping for the UL RLC blocks, then the mobile may ignore some negative acknowledgements that were received in the Packet UL ACK/NACK message. This may distort the ARQ procedure slightly.

• If the BS_CV_MAX parameter is lower than the actual round-trip delay or if the mobile is not able to do accurate time stamping for the UL RLC blocks, then the mobile may transmit needless retransmissions after processing a Packet UL ACK/NACK message.

It is recommended to tune the BS_CV_MAX parameter so that the minimum value is searched with which the mobile does not send needless RLC retransmissions right after the processing of a Packet UL ACK/NACK message.

After modification of this parameter it takes about 5 minutes for processes to get the new values. After 5 minutes disable and then re-enable GPRS in those cells where GPRS is active for the change to take effect.

8.1.5.5 Measurements EUTM usage

• UL_DATA_CONT_AFTER_COUNTDOWN (c072115)

• EXTENDED_UL_TBFS (c072116)

BS_CV_MAX

• IGNOR_RLC_DATA_BL_UL_DUE_BSN is changed when BS_CV_MAX is changed.

The MS accepts a retransmission request for a block in Packet UL ACK/NACK even if it has (re)-transmitted the block so recently that the PCU has not had the chance to receive the block before sending the P UL ACK/NACK.

The new QoS formulas (llc_4, llc_5, llc_6) should be able to tell if the throughput gets worse, although it is not so easy to say directly that this is caused by BS_CV_Max changes.

The benefit of EUTM and BS_CV_MAX can be measured by RTT tests.


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8.1.5.6 Parameters The following setup is recommended (the BSS11.5 recommendation is valid for S13, too):

BSS10.5 +

CD7

BSS11+CD7 BSS11.5 BSS11.5

(default) (recommendation) (default) (recommendation)

DL_TBF_RELEASE_DELAY 46 / 67 03E8 (1s) 03E8 (1s) 03E8 (1s) 03E8 (1s)

UL_TBF_RELEASE_DELAY 46 / 68 01F4 (0.5s) 01F4 (0.5s) 01F4 (0.5s) 01F4 (0.5s)

UL_TBF_RELEASE_DELAY_EXT 46 / 71 - 07D0 (2s) 07D0 (2s) 07D0 (2s)

UL_TBF_SCHED_RATE_EXT 46 / 72 - 4 (80ms) 4 (80ms) 4 (80ms)

BS_CV_MAX - 6 9 9 9

Parameter Parameter

class / id

4. Table Parameter set

8.2 GPRS Link Adaptation Currently the coding schemes CS-1 and CS-2 are supported. The BSC level parameters coding scheme no hop (COD) and coding scheme hop (CODH) define whether the fixed CS value (CS-1/CS-2) is used or if the coding scheme is changed dynamically according to the Link Adaptation algorithm. In unacknowledged RLC mode CS-1 is always used regardless of the parameter values. When the Link Adaptation algorithm is deployed, then the initial value for the CS at the beginning of a TBF is CS-2.

The Link Adaptation (LA) algorithm is used to select the optimum channel coding scheme (CS-1 or CS-2) for a particular RLC connection and it is based on detecting the occurred RLC block errors.

Essential for the LA algorithm is the crosspoint, where the two coding schemes give the same bit rate. In terms of block error rate (BLER) the following equation holds at the crosspoint: 8.0 kbps * (1 - BLER_CP_CS1) = 12 kbps * (1 - BLER_CP_CS2), where:

• 8.0 kbps is the theoretical maximum bit rate for CS-1

• 12.0 kbps is the theoretical maximum bit rate for CS-2

• BLER_CP_CS1 is the block error rate at the crosspoint when CS-1 is used

• BLER_CP_CS2 is the block error rate at the crosspoint when CS-2 is used


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X

CS1 & CS2 Crosspoint

12. Figure CS1 and CS2 cross point

8.2.1 Measurements The following KPIs can be used to measure LA functionality (if there is not any limiting factor, like EDAP congestion):

• Downlink GPRS RLC throughput trf_235b

• Uplink GPRS RLC throughput trf_233c

• Downlink GPRS CS1 ratio rlc_55b

• Downlink GPRS CS2 ratio rlc_33

• Downlink GPRS CS1 retransmission ratio rlc_12a

• Downlink GPRS CS2 retransmission ratio rlc_13

• Uplink GPRS CS1 ratio rlc_54b

• Uplink GPRS CS2 ratio rlc_32

• Uplink GPRS CS1 retransmission ratio rlc_10e

• Uplink GPRS CS2 retransmission ratio rlc_11f

8.2.2 Parameters

The following parameters can be used to modify LA functionality.


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• GPRS Coding Scheme Hopping

• GPRS Coding Scheme No Hopping

• DL BLER Crosspoint for CS Selection Hopping (DLBH)

• UL BLER Crosspoint for CS Selection Hopping (ULBH)

• DL BLER Crosspoint for CS Selection Non Hopping (DLB)

• UL BLER Crosspoint for CS Selection Non Hopping (ULB)

8.3 EGPRS Link Adaptation The goal for Link Adaptation (LA) algorithm is to adapt to situations where signal strength compared to interference level is changing within time. Therefore the task of the LA algorithm is to select the optimal MCS for each radio condition to maximize channel throughput and optimize retransmission.

LA adapts to path loss and shadowing but not fast fading, while Incremental Redundancy (IR) is better suited for compensating fast fading.

8.3.1 Measurements

The following KPIs are used to analyze EGPRS LA:

• Downlink EGPRS RLC throughput trf_236

• Downlink EGPRS coding scheme selection rlc_57

• Downlink EGPRS retransmission ratio rlc_21

• Uplink EGPRS RLC throughput trf_234

• Uplink EGPRS coding scheme selection rlc_56

• Uplink EGPRS retransmission ratio rlc_20b

• Uplink EGPRS BLER rlc_60

8.3.2 Parameters

The following parameters are used to optimize EGPRS LA:

• EGPRS Link Adaptation Enabled (ELA)

• Initial MCS for Acknowledged Mode (MCA)

• Initial MCS for Unacknowledged Mode (MCU)

• Maximum BLER in Acknowledged Mode (BLA)

• Maximum BLER in Unacknowledged Mode (BLU)


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• Mean BEP Offset GMSK (MBG)

• Mean BEP Offset 8PSK (MBP)

8.3.3 Effect of Link Adaptation

There are few parameters that can modify the LA functionality and finally the data rate. The MCA parameter has impact mainly on the small file size transfer. As it can be seen on the Figure 13 below, the higher MCA settings allow higher data rate mainly in good radio condition (the file size is 55KB). If the interference is high (yellow curve below), the effect of MCA setting will be negligible even in case of small file size transfer, too.

Impact of MCA Setting on RLC/MAC Data Rate

30

35

40

45

50

55

0 1 2 3 4 5 6 7 8 9 10

MCA

Kbp

s

RLC/MAC Data Rate (55K FTP Download x5) -65 dBm, no interfrenece

RLC/MAC Data Rate (55K FTP Download x5) -80 dBm, C/I 20 dB

RLC/MAC Data Rate (55K FTP Download x5) -90 dBm, C/I 15 dB

Log. (RLC/MAC Data Rate (55K FTP Download x5) -65 dBm, no interfrenece)

Log. (RLC/MAC Data Rate (55K FTP Download x5) -80 dBm, C/I 20 dB)

Log. (RLC/MAC Data Rate (55K FTP Download x5) -90 dBm, C/I 15 dB)

Figure 13 MCA settings

The BLA parameter can improve the data rate in case of bad radio environment. If the setting of BLA is e.g. 30 % and the C/I is high, than the MCS degradation will take place quickly, so the retransmission ratio will be lower and the effective RLC/MAC data rate will be probably a bit higher.

The Mean BEP Offset GMSK and the Mean BEP Offset 8PSK parameter recommendation is the default value (0), because the LA functionality is optimized by PL based on simulations.


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8.4 Multiplexing Multiplexing can reduce the TSL data rate. The affect of multiplexing on TSL data rate is listed below (from S10.5):

• Synchronization

• GPRS USF on DL EGPRS TBF

• TSL sharing - GPRS/EGPRS TBFs’ multiplexing on a TSL

8.4.1 Synchronization

The synchronization is BSS SW release dependent:

• In S11 basic release:

In case of GPRS territory only (if EGENA=N): the synchronization in every 17th block is not needed anymore.

In case of (E)GPRS territory (if EGENA=Y): "For synchronization purposes, the network sends at least one radio block using CS-1 or MCS-1 in the downlink direction every 360 milliseconds on every timeslot that has either uplink or downlink TBFs. If there are only EGPRS TBFs on the timeslot, the synchronization block is sent using MCS-1. If there are also GPRS TBFs on the timeslot, the synchronization block is sent using CS-1"

• In S11 CD1.2 onwards:

In case of GPRS territory only (if EGENA=N): the synchronization in every 17th block is not needed anymore.

In case of (E)GPRS territory (if EGENA=Y): For synchronization purposes, the network sends at least one radio block every 360 milliseconds using a MCS or CS low enough that all mobiles can be expected to be able to decode the block. If there are only EGPRS TBFs in the timeslot, the synchronization block is sent using CS-1 or a low enough MCS. If there are GPRS TBFs as well, the synchronization block is sent using CS-coding"

If any MS has not been decoding anything for a 17 block period, the PCU put the limit of the MCS (Modulation and Coding Scheme)/CS (Coding Scheme) for GPRS in the next downlink block so low that the MS can be expected to decode it. The block may be addressed to other MSs too but the MCS/CS is limited according to the rules below.

• An EGPRS MS is expected to decode blocks that are using lower or equal MCS/CS than link adaptation has selected for the MS’s downlink TBF. If any EGPRS MS only has uplink TBF, (M)CS-1 or (M)CS-2 in the downlink is considered robust enough to be correctly decoded.

• An GPRS MS is expected to decode blocks that are using CS-1 or CS-2.

• If any GPRS MS has not been decoding anything for a 17 block period, the PCU sends an CS-1 or CS-2 coded block. If possible, the turn is given to a GPRS downlink TBF. If only EGPRS TBF exist on the downlink connection, the PCU sends a CS-1 (dummy) control block.


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So in S11 CD 1.2 onwards the CS1/MCS1 usage is reduced significantly compared to S11 basic release backwards.

8.4.2 Timeslot sharing

If the timeslot is shared among TBFs, then the TSL data rate will be reduced. The rate reduction is the effect of territory occupation and needs further investigation to know the exact impact of it (if the TSL data rate is 50 kbps and this TSL is shared by two users, then the user RLC/MAC data rate will be less than 25 kbps, because of increased territory occupation).

8.4.3 GPRS and EGPRS Multiplexing

GPRS and EGPRS TBFs can be multiplexed dynamically on the same timeslot.

When USF is addressed to GPRS TBF the downlink RLC radio block carrying the USF must use GMSK coding scheme, that is MCS-1 to MCS-4 if the DL RLC radio block is addressed to EGPRS TBF or CS-1 to CS-2, if the DL RLC radio block is addressed to GPRS TBF [04.60] 5.2.4a.

If the RLC has selected 8-PSK MCS then the MCS will be GMSK MCS as follows:

o Initial transmission of a RLC block: The downlink transmission of EGPRS DL TBF is forced to GMSK only on the timeslots used by the GPRS UL TBF and only for the block periods when GPRS USF is actually transmitted.

o Retransmission of a RLC block: If the RLC is retransmitting a downlink data block using 8-PSK MCS, USF will not be given to GPRS TBF at this time.

8.4.4 Dynamic Allocation with USF4

More information about DA without and with USF4 can be found in [1].

8.4.5 Extended Dynamic Allocation More information about EDA can be found in [1].

8.4.6 Measurements

Amount of TBFs / TSL

• Uplink TBFs pr timeslot tbf_37d

• Downlink TBFs pr timeslot tbf_38d

GPRS TBF multiplexed with EGPRS TBF

• 8PSK coding scheme downgrade due to GPRS multiplexing rlc_61

8.4.7 Parameters

The following parameters have direct impact on multiplexing:


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1..7, default:7maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the uplink

direction.

MNULMaximum Number of UL TBF

1..9, default:9maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the downlink

direction.

MNDLMaximum Number of DL TBF

Range and DefaultDescriptionAbbreviationParameter Name

1..7, default:7maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the uplink

direction.

MNULMaximum Number of UL TBF

1..9, default:9maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the downlink

direction.

MNDLMaximum Number of DL TBF

Range and DefaultDescriptionAbbreviationParameter Name

Channel Allocation Algorithm tends to separate EDGE TBFs and GPRS TBFs on different RTSL to avoid multiplexing, if only one PS Territory exists in the cell or there is high load. The algorithm checks the need for re-allocation every TBF_LOAD_GUARD_THRSHLD, in order to separate sessions.

8.5 UL Power Control The optimized Uplink Power Control can achieve higher signal level as well.

The following graph shows the function of MS output power and DL Rx Lev.

0

5

10

15

20

25

30

35

-30 -40 -45 -50 -55 -60 -65 -70 -75 -80 -85 -90 -95 -100 -105 -110

DL Rx Lev (dBm)

MS output pwr (dBm)

Gamma = 14

Gamma = 36

Gamma = 28Alpha =0.8

0

5

10

15

20

25

30

35

-30 -40 -45 -50 -55 -60 -65 -70 -75 -80 -85 -90 -95 -100 -105 -110

DL Rx Lev (dBm)

MS output pwr (dBm)

Gamma = 14

Gamma = 36

Gamma = 28Alpha =0.8

Figure 14 Effect of gamma and alpha 0.8

With lower values of Gamma the MS output power is increased, when the user is closer to the BTS. This can help to reduce retransmissions in the UL and improve the performance. The drawback would be that with lower values of Gamma interference in the UL is increased too.


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Practically it is not so easy to measure the impact of PC on signal level and finally on data rate.

8.5.1 Measurements

The following KPIs can be used to observe the effect of UL PC functionality.

• Uplink GPRS CS1 ratio rlc_54b

• Uplink GPRS CS2 ratio rlc_32



• Uplink EGPRS RLC throughput trf_234

• Uplink EGPRS coding scheme selection rlc_56

• Uplink EGPRS retransmission ratio rlc_20c

• Uplink EGPRS BLER rlc_60

• LLC throughput for 4 timeslot capable EDGE MS (pr QoS class) llc_6

• LLC throughput for other than 4 timeslot capable EDGE MS (pr QoS class) llc_5

• LLC throughput for GPRS MS (pr QoS class) llc_4

Low UL PS power gives bad performance, high UL PS power with low PS traffic gives good performance and high UL PS power with high UL PS traffic gives bad performance.

CSW RX Qual must be checked on those TRXs, where (E)GPRS traffic is generated.

8.5.2 Parameters

Alpha and Gamma parameters have impact on UL PC functionality:

1.00.81.00.7Alpha

28362834Gamma

1800/1900 new

recommendation

1800/1900 old850/900 new

recommendation

850/900 oldParameter

1.00.81.00.7Alpha

28362834Gamma

1800/1900 new

recommendation

1800/1900 old850/900 new

recommendation

850/900 oldParameter

Recommended settings should provide good UL throughput in a case where maximum of -105 dBm level interferer is present.

Still, in strong signal conditions, MS output power is limited to avoid unnecessary UL interference generation especially in high altitude locations.


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In practice, estimating impact of possible additional interference caused by higher mobile output power is very difficult. This impact is anyway considered clearly a secondary issue compared to improved UL throughput.

This should provide an improvement to UL throughput in all Nokia supplied networks that still use previous default values.


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9. Multislot Usage Maximization When the TSL data rate is maximized, the next optimization step is to maximize the PSW territory. The aim of this maximization is to provide the required TSLs based on multislot capability of MS.

The multislot usage can be limited by:

• TSL Unavailability

• CSW traffic and HSCSD

• Free TSL setting

9.1 TSL unavailability The TSL unavailability (for any traffic due to fault on normal TRXs) can be checked by ND226 - uav_13.

9.2 CSW traffic and HSCSD Average CS traffic on normal TRXs can be checked by trf_97. This KPI includes all types of CS traffic (single TCH, HSCSD) on normal TRXs.

In principle CSW has always priority over PSW and the share between HSCSD and (E)GPRS makes it possible for one multislot HSCSD user to block many (E)GPRS users from the service.

Protection of (E)GPRS is needed based on dedicated GPRS capacity, MinHSCSDcapacity and DefaultGPRScapacity. The Table 5 shows the service with different parameter:

MinHSCSDcapacity DefaultGPRScapacity Priority0 0 Multislot HSCSD > (E)GPRS

>0 0 Multislot HSCSD > (E)GPRS0 >0 (E)GPRS > Multislot HSCSD

>0 >0

Multislot HSCSD > (E)GPRS (if HSCSD load < MinHSCSD capacity) (E)GPRS > Multislot HSCSD (if HSCSD load > MinHSCSDcapacity)

Table 5 Prioritization between HSCSD and (E)GPRS

9.3 Territory Downgrade The territory downgrade heavily depends on the size of dedicated and default territory. There are two types of downgrades:

• Territory downgrade due to CSW traffic rise (Downgrade request below Default territory because of rising CSW (c1179))


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• Territory downgrade due to less PSW traffic (Downgrade request back to the default territory when there is no need for additional channels anymore (c1181))

9.4 Territory Upgrade Request Rejection Territory upgrade request rejection also limits the data rate:

• Territory upgrade request rejection beyond default territory. Upgrade request beyond Default territory for additional resources, which can be rejected because of (c1174):

1. PCU and EDAP capacity limitation (256 Abis TSL per PCU)

2. High CSW load

9.5 Free TSLs The BSC attempts to keep one or more timeslots free in the CSW territory all the time. The reason for this comes from the fact that if the CSW territory becomes fully occupied and further CSW connections need to be accommodated, then one or more timeslots from the GPRS territory would need to be re-allocated for CSW use. This re-allocation introduces a delay due to associated signaling requirements.

In order to avoid passing this delay onto the CSW user, the system attempts to keep a number of timeslots free (spare CSW timeslot) for such CSW allocations.

The number of timeslots kept free after upgrading is defined by the BSC parameter freeTSLCSupgrade. This value is a condition for starting territory upgrade.

The number of timeslots kept free after downgrading is defined by parameter freeTSLforCSdowngrade. This is the amount of free TSLs that must be maintained after the downgrade. If the number of free TSLs goes below this value a downgrade will be started.

The effect of the free timeslots is a decrease in overall cell capacity. It should be noted, however, that the free slots will be occupied when required by the circuit switched traffic load. Therefore, when considering overall cell (or TRX) capacity, this overhead must be taken into account.

The detailed theoretical information about freeTSLCSupgrade and freeTSLforCSdowngrade can be found in [1].

9.6 HMC and EDA High Multislot Classes increases GPRS/EDGE peak downlink throughput to 296 kbit/s (~250 kbps on 5 DL TSLs in practice)

• Supports 3GPP Release 5 High Multislot Mobiles

• Multi Slot Class 30 ... 45 Mobiles

• Maximum (Sum = 6): 5+1, 4+2 Timeslots DL+UL


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Extended Dynamic allocation increases GPRS/EDGE peak uplink throughput to 236.8 kbit/s (~200 kbps on 4 UL TSLs in practice)

• With Class 1-12 mobiles, no EDA

• Maximum 4+1, 3+2 timeslots DL+UL

• With Class 1-12 mobiles and EDA

• Maximum 1+4, 2+3 timeslots DL+UL

• With High Multislot mobiles and EDA

• Maximum 2+4, 3+3 Timeslots DL+UL

So EDA is not only an access method to help the device to connect to the network on UL, but it allows increasing the UL Multislot usage, too.

9.7 Measurements The following KPIs are recommended to measure multislot usage:

• Actual Territory ava_44

• Peak PS territory (c2063))

Recommendation: ava_44 and c2063 can be compared with the CDEF settings. If too big difference, then CDEF should perhaps be changed, or more capacity should be added to the cell.

• Multislot Blocking

• UL / DL multislot allocation blocking – hard (tbf_15a, tbf_16a)

• DL multislot blocking – soft (blck_33a)

Recommendation: Too much multislot blocking shows that the territory is perhaps not enough.

It is also interesting to see how many timeslots which are requested (helpful in determining the size of the default territories)

• Requested timeslots for GPRS TBFs c72039-c72149, c72040-c72150, c72041-c72151, c72042-c72152

• Requested timeslots for EDGE TBFs c72149, c72150, c72151, c72152

If the resources are not enough, also the LLC throughput will suffer:

• LLC throughput for 4 timeslot capable EDGE MS (all QoS classes) llc_3a

• LLC throughput for 4 timeslot capable EDGE MS (pr QoS class) llc_6

• LLC throughput for other than 4 timeslot capable EDGE MS (pr QoS class) llc_5a

• LLC throughput for GPRS MS (pr QoS class) llc_4a


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If ho_61 shows that there are too many intracell handovers triggered by GPRS (ie caused by too frequent territory movements), the following counters can be used to get an idea if the CDEF parameter should be adjusted:

• GPRS_TER_UPGRD_REQ: If high, it means that PS often needs more resources than there is in the territory. Indicates that CDEF is too low

• GPRS_TER_UG_DUE_DEC_CSW_TR: If high, it means that the territory is often recovering after having been “invaded” by CS calls. Indicates that CDEF is too high or that CS traffic should be moved to another BTS.


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10. End-to-End Data Rate Maximization

10.1 HLR Settings The following list summaries the activities in QoS and subscriber relations:

• Creation of QoS Profiles

• Creation of PDP contexts for each subscribers (with QoS profiles)

10.1.1 HLR QoS Profile Handling (MML command: MYQ)

MYQ command is used to create a R99 GPRS-related Quality of Service profile. To link an appropriate QoS profile to the subscriber, the QoS profile index has to be inserted into the subscriber data.

INDEX = <QoS profile index>,

[NAME = <QoS profile name> | <no name> def] :

CLASS = <traffic class>

ORDER = <delivery order>

DELERR = <delivery of erroneous SDU>

SDUMAX = <maximum SDU size>

DWNMAX = <maximum bit rate for downlink>

UPMAX = <maximum bit rate for uplink>

BER = <residual BER>

SDUERR = <SDU error ratio>

DELAY = <transfer delay>

UPBR = <guaranteed bit rate for uplink>

DWNBR = <guaranteed bit rate for downlink>

PRIOR = <traffic handling priority> ;

10.1.2 Subscriber Data Handling (MML command: MN)

GPRS subscriber data handling MML is a HLR subscriber data management interface, which is used for the creation, deletion, modification, and output of PDP contexts.

• PDP Context Creation


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The following parameters can be set in PDP context creation assigned to a subscriber:

MNC:(IMSI=<international mobile subscriber identity > | IMSIFILE=<name of the IMSIFILE>):

[PDPID=[<PDP context id>|N def] |

PDPTYPE=[<type of the PDP context>|F121 def] |

PDPADDR=<address of the PDP context> |

VPLMN=[<visitor PLMN address allowed>|N def] |

ALLOC=[<allocation class>|2 def] |

APN=[<access point name>|* def] |

GPRSACC=[<add GPRS access>|NA def] |

FUN=[<functional status>|A def] |

PCHARG=<charging characteristic><option>]...,

(QOSP=<quality of services profile>);

• PDP Context Modification

More parameters can be set by PDP context modification:

MNM:(IMSI=<international mobile subscriber identity > | IMSIFILE=<name of the IMSIFILE>):

([SGSN=<SGSN address> |

NWACC=<network access> |

MTSM=<MT-SMS via SGSN> |

CELLOPT=<cell update information> |

MVGS=<MT-SMS via GPRS suppressed><option> |

CHARG=<subscriber based charging characteristic><o ption> |

GRP=<GPRS roaming profile><option> |

GPRSSAM=<GPRS service area>]...: |

[(PDPID=<PDP context id> |

(TYPECRI=<PDP context's PDP type criterion>,

APNCRI=<PDP context's APN criterion> )),


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PDPTYPE=<type of the PDP context> |

PDPADDR=<address of the PDP context> |

VPLMN=<visitor PLMN allowed> |

ALLOC=<allocation class> |

QOSP=<quality of services profile> |

APN=<access point name> |

FUN=<functional status> |

PCHARG=<PDP context based charging characteristic><option>]...):

DISPL=<display mode>|N def;

10.1.3 QoS Parameter Set Recommendation

The following set is recommended to implement:

Traffic Class (TC) = Interactive

RLC mode = Acknowledged

THP = 1

ARP = 1

SDU error ratio = 10^-4

Maximum Bitrate = 2048 kbps

Transfer delay = 1000ms

10.2 Gb over FR The following setup can be used on flow control for achieving maximized data rate on application layer.


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25000 (25 kB)

25000 (25 kB)

4500 (36 Kbps)

1500 (12 Kbps)

25000 (25 kB)

10000 (10 kB)

40 (320 bps)

15000 (120 Kbps)

4500 (36 Kbps)

100 (10%)

Based on TN819 (12 May 2005)

0029

0028

0027

0026

0025

0024

0023

0022

0021

0020

Num.

B

B

B/s

B/s

B

B

B/s

B/s

B

% (/10)

Unit

FC_B_MAX_TSL_EGPRS

FC_B_MAX_TSL

FC_R_TSL_EGPRS

FC_R_TSL

FC_MS_B_MAX_DEF_EGPRS

FC_MS_B_MAX_DEF

FC_MS_R_MIN

FC_MS_R_DEF_EGPRS

FC_MS_R_DEF

FC_R_DIF_TRG_LIMIT

Parameter

25000 (25 kB)

25000 (25 kB)

4500 (36 Kbps)

1500 (12 Kbps)

25000 (25 kB)

10000 (10 kB)

40 (320 bps)

15000 (120 Kbps)

4500 (36 Kbps)

100 (10%)

Based on TN819 (12 May 2005)

0029

0028

0027

0026

0025

0024

0023

0022

0021

0020

Num.

B

B

B/s

B/s

B

B

B/s

B/s

B

% (/10)

Unit

FC_B_MAX_TSL_EGPRS

FC_B_MAX_TSL

FC_R_TSL_EGPRS

FC_R_TSL

FC_MS_B_MAX_DEF_EGPRS

FC_MS_B_MAX_DEF

FC_MS_R_MIN

FC_MS_R_DEF_EGPRS

FC_MS_R_DEF

FC_R_DIF_TRG_LIMIT

Parameter

6. Table Flow control parameter recommendations

4TSL capable mobile at good radio conditions (MCS=9), theoretical max throughput would be 4X59.2kbps=~240kbps and consider, therefore both Bearer Channel Access Rate, and Committed Information Rate (CIR) should be at minimum 384 kbps.

Recommended to have one 8 TSL Gb link having CIR is 512 kbps (8 E1/T1 TSLs)

The CIR is usual set at both ends, i.e. BSC and SGSN. The BSC setting is the deciding one.

10.3 Gb over IP The Gb over IP Planning Guideline can be found in the following link:



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10.4 TCP/IP The following table shows the proper server and client setup.

TCP Receive Window Size 24 x MSS (35040B) for 4 radio TSLs

Maximum Achievable Segment Size (MSS)

1460 B

Maximum Transfer Unit (MTU) 1500 B

TCP Sending Buffer Size 9 x MSS for GPRS

44 x MSS for EGPRS

FTP Server Application (FileZilla server 0.9.6)

TCP buffer size = 1 MSS

SACK = 1 (DWORD)

Time Stamp = 2 (DWORD)

FTP Client (Windows 2000, Windows XP)

TCP Window Size = 24 x MSS

TCP Receiving buffer size = 64 kB

SACK = 1 (DWORD)

Time Stamp = 2 (DWORD)

7. Table Server and client setup


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10.5 Measurements The user experienced data rate can be measured by trf_125 (there is good correlation between trf_125 and application throughput)

• For larger files, good correlation between radio link conditions and throughput

• File size has big impact on throughput values

The following figure shows the correlation between HTTP data rate and trf_125.

HTTP throughput vs trf_125

0

20

40

60

80

100

120

140

~50 dB 10 dB 5 dB

Downlink C/I

kbit/

s

1 KB, App

1 KB, trf_125

10 KB, App

10 KB, trf_125

50 KB, App

50 KB, trf_125

100 KB, App

100 KB, trf_125

1000 KB, App

1000 KB, trf_125

15. Figure Correlation between HTTP data rate and t rf_125


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11. Mobility Optimization The aim of mobility optimization is to reduce the cell outage time during cell re-selection.

Cell outage can be reduced by:

• Providing enough signaling capacity for cell re-selection (the RACH, PCH, AGCH and SDCCH channel are not limiting the signaling flow)

• Rebalancing BCFs among PCUs properly (the important neighbors are allocated to the same PCU)

• Reallocating LA/RA borders properly

• Enabling Network Assisted Cell Change (NACC) feature

Three types of delay can be calculated as cell re-selection time:

o Cell outage:

� In one-phase access: the time between the last EGPRS Packet Downlink Ack/Nack message and the first Packet Uplink Ack/Nack.

� In two-phase access: the time between the last EGPRS Packet Downlink Ack/Nack message and the first Packet Uplink Assignment.

o Data outage: the time between the last and the first EGPRS Packet Downlink Ack/Nack message.

o Application outage: the time between the last and the first successfully received FTP-packet.

EGPRS Packet Downlink Ack/Nack

MS GERAN

Routing Area Update Accept

Routing Area Update Complete

First IP packets

Last IP packets

DataOutage

Application Outage

CellOutage

Routing Area Update Request

EGPRS Packet Downlink Ack/Nack

Packet Uplink Assignment

16. Figure Types of Cell-reselection delay


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The cell re-selection time can be reduced based on the following cases:

• Cell-reselections without LA/RA update (intra/inter PCU)

• Cell-reselections with LA/RA updates (intra/inter PCU)

• Cell-reselections with inter PAPU/SGSN

11.1 Cell-reselection without LA/RA Update (Intra/Inter PCU) The cell-reselection events without RA Update are listed below:

1. Mobile station (MS) is camped on Cell A and it notices a better Cell B

2. MS abnormally stops all the temporary block flow sessions (TBFs) from Cell A. (The network has no idea what is happening.)

3. MS camps on the new Cell B and reads system information (SI) messages

4. When MS has successfully read the SI messages, it asks for a channel and resources by sending CHANNEL REQUEST message for cell update and packet resource request message (Note: 2phase access for EDGE phone on CCCH)

5. PCU responds with an immediate assignment message and packet uplink assignment message respectively.

6. SGSN recognizes TLLI (in the packet resource request message) and understands that a cell reselection occurred and it sends Flush LLC packet data unit to the PCU. Note: The MS data stored in Cell A buffer is kept in the PCU buffer if Cell A and Cell B belong to the same PCU otherwise it is deleted and has to be retransmitted.

7. PCU sends an acknowledgement (FLUSH-LLC-ACK) to the SGSN.

8. SGSN sends an LLC PDU to the PCU.

9. PCU sends downlink assignment message for DL TBF establishment on PACCH.

10. Data transfer resumes In the analysis we separated the BSS cell-reselection outage from data outage.

The Figure 17 shows the cell-reselection process on signalling in upload case.


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MS BTS BSC SGSN

Channel Request (RACH)

Immediate Assignment (CCCH)

P_Channel Required

P-Immediate Assignment Cmd

UL TBF ASSIGNMENT, MS ON CCCH. 2 phase access.

Packet Resource Request (PACCH)Packet Resource Request

Packet Uplink AssignmentPacket Uplink Assignment (PACCH)

RLC Data block (PDCH)

Packet Uplink Ack/Nack

RLC Data Block

Packet Uplink Ack/Nack (specs)

NOTE: BTS does not send Imm Ass Ackfor Single block Immediate Assignment

Including TLLI for contention resolution


First System information message [ 1].

UL TBF ASSIGNMENT, MS ON CCCH. 2 phase access [ 2].

Uplink Data Packets

BS

S/D

ata

Cel

l Res

elec

tion

Out

age

First System information message(BCCH)

MS BTS BSC SGSNMS BTS BSC SGSN



P_Channel Required


UL TBF ASSIGNMENT, MS ON CCCH. 2 phase access.

Packet Resource Request (PACCH)Packet Resource Request


RLC Data block (PDCH)

Packet Uplink Ack/Nack

RLC Data Block

Packet Uplink Ack/Nack (specs)

NOTE: BTS does not send Imm Ass Ackfor Single block Immediate Assignment





Uplink Data Packets

BS

S/D

ata

Cel

l Res

elec

tion

Out

age


Figure 17 BSS and Application data cell-reselection outage in upload

The cell outage time in case of DL transfer is measured from the last “RLC/MAC Uplink” message on BCCH with “EGPRS_PACKET_DOWNLINK_ACK/NACK. The end of the BSS cell outage measurement is the “Packet_Uplink_Assignment” message on downlink. See Table 8 below:

Table 8 BSS cell outage

Event name Time Channel MessageRLC/MAC Uplink 20:42.0 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_1"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_2"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_3"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_4"… … … …

Layer 3 Downlink 20:42.6 BCCH "SYSTEM_INFORMATION_TYPE_4"Cell Reselection 20:42.8 from CI 5032 to CI 5033Layer 3 Downlink 20:42.8 BCCH "SYSTEM_INFORMATION_TYPE_2"… … … …

Layer 3 Downlink 20:43.1 BCCH "SYSTEM_INFORMATION_TYPE_13"Layer 3 Uplink 20:43.1 RACH "CHANNEL_REQUEST"Layer 3 Downlink 20:43.2 CCCH "IMMEDIATE_ASSIGNMENT"Layer 3 Downlink 20:43.2 CCCH "PAGING_REQUEST_TYPE_1"Layer 3 Downlink 20:43.2 CCCH "PAGING_REQUEST_TYPE_1"Layer 3 Downlink 20:43.3 CCCH "PAGING_REQUEST_TYPE_1"Layer 3 Downlink 20:43.3 BCCH "SYSTEM_INFORMATION_TYPE_2"… … … …

Layer 3 Downlink 20:43.8 BCCH "SYSTEM_INFORMATION_TYPE_13"RLC/MAC Uplink 20:43.8 PACCH "PACKET_RESOURCE_REQUEST"RLC/MAC Downlink 20:44.0 PACCH "PACKET_UPLINK_ASSIGNMENT"RLC/MAC Downlink 20:44.0 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"


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The application outage time in case of DL transfer is measured from the last “RLC/MAC Uplink” message on BCCH with “EGPRS_PACKET_DOWNLINK_ACK/NACK. The end of the BSS cell outage measurement is the “Packet_Downlink_Assignment” message on downlink. See Figure 18 and Table 9 below:

MS BTS BSC SGSN



P_Channel Required



Packet Resource Request (PACCH) Packet Resource Request




LLC PDUDL TBF Establishment when UL TBF is ongoing [ 3]


Packet Downlink Assignment

Downlink Data Packets

Packet Downlink Assignment (PACCH)

Packet Downlink Ack/Nack (PACCH)Packet Downlink Ack/Nack

RLC Data blocks (PDTCH)RLC Data blocks

Cel

l Res

elec

tion

BS

S O

utag

e

Packet downlink dummy control blocksPacket downlink dummy control blocks

Cel

l res

elec

tion

dat

a O

utag

e


MS BTS BSC SGSNMS BTS BSC SGSN



P_Channel Required



Packet Resource Request (PACCH) Packet Resource Request




LLC PDUDL TBF Establishment when UL TBF is ongoing [ 3]


Packet Downlink Assignment

Downlink Data Packets

Packet Downlink Assignment (PACCH)

Packet Downlink Ack/Nack (PACCH)Packet Downlink Ack/Nack

RLC Data blocks (PDTCH)RLC Data blocks

Cel

l Res

elec

tion

BS

S O

utag

e

Packet downlink dummy control blocksPacket downlink dummy control blocks

Cel

l res

elec

tion

dat

a O

utag

e


Figure 18 BSS and Application data cell-reselection outage in download


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Event name Time Channel MessageRLC/MAC Uplink 20:42.0 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_1"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_2"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_3"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_4"… … … …Layer 3 Downlink 20:42.6 BCCH "SYSTEM_INFORMATION_TYPE_4"Cell Reselection 20:42.8 from CI 5032 to CI 5033Layer 3 Downlink 20:42.8 BCCH "SYSTEM_INFORMATION_TYPE_2"… … … …

Layer 3 Downlink 20:43.1 BCCH "SYSTEM_INFORMATION_TYPE_13"Layer 3 Uplink 20:43.1 RACH "CHANNEL_REQUEST"Layer 3 Downlink 20:43.2 CCCH "IMMEDIATE_ASSIGNMENT"Layer 3 Downlink 20:43.2 CCCH "PAGING_REQUEST_TYPE_1"Layer 3 Downlink 20:43.2 CCCH "PAGING_REQUEST_TYPE_1"Layer 3 Downlink 20:43.3 CCCH "PAGING_REQUEST_TYPE_1"Layer 3 Downlink 20:43.3 BCCH "SYSTEM_INFORMATION_TYPE_2"… … … …

Layer 3 Downlink 20:43.8 BCCH "SYSTEM_INFORMATION_TYPE_13"RLC/MAC Uplink 20:43.8 PACCH "PACKET_RESOURCE_REQUEST"RLC/MAC Downlink 20:44.0 PACCH "PACKET_UPLINK_ASSIGNMENT"RLC/MAC Downlink 20:44.0 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"RLC/MAC Downlink 20:44.0 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"… … … …

RLC/MAC Downlink 20:44.2 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"RLC/MAC Downlink 20:44.2 PACCH "PACKET_DOWNLINK_ASSIGNMENT"RLC/MAC Uplink 20:44.3 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"

Table 9 Application outage in download

The application outage time is 2.2 s from the table above. The Table 10 below shows a measurement results from a live network in case of DL transfer:

Table 10 Cell and application outage results from TOM in download

As it can be seen from Table 10 above, the BSS cell outage is almost the same in both intra and inter PCU cases. But the data outage is more variable, because the Packet Downlink Assignment message is coming from SGSN, so the effect of Gb and SGSN is taken into account, too (while Packet Uplink assignment is based on MS-PCU discussion only).

Cell-reselection events 1 2 3 4 5 6 7 8 9 RemarkLayer 3 Downlink (BCCH)PACKET_UPLINK_ASSIGNMENTLayer 3 Downlink (BCCH)PACKET_DOWNLINK_ASSIGNMENT

from (CI) 5692 5531 5533 5533 10101 10101 5032 5031 5693to (CI) 5531 5533 10101-5533 10101 5032 5032 5031 5693 5692Comments 1) 2), 4) 3), 4) 2), 4)

1) Ping-pong cell-reselection (5533-10101-5533)2) No Packet Downlink Asignment in time3) TBF drop and new allocation on other cell4) InterPCU

2.2 2.4 24.7 1.61.8 10 2.3 17.5

2 2.2 2.1 1.41.6 2.1 2 2.12.1

2.3

BSS cell outage (s)

Data outage (s)


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11.2 Cell-reselection with LA/RA Update Two types of LA/RA Updates can be analyzed:

• Cell-reselection with uncombined LA/RA Update

• Cell-reselection with combined RA Update (Gs interface required)

11.2.1 Cell-reselection with uncombined LA/RA Update

The cell-reselection events without LA/RA Update are listed below:

1. MS is camped on Cell A and it notices a better Cell B

2. MS abnormally stops all the temporary block flow sessions (TBFs) from Cell A.

3. MS camps on the new Cell B and reads system information (SI) messages

4. When it has successfully read the SI messages, MS sends CHANNEL REQUEST message for location area update.

5. An SDCCH channel is created for this purpose.

6. MS then sends location area update

7. Security functions set by the operator take place.

8. When authentication is complete the SDCCH channel is released

9. Routing area update request is sent to the network

10. A channel and resources are requested for routing area update (Note: 2phase access for EDGE phone on CCCH)

11. When granted network sends routing area update accept to MS

12. And the MS acknowledges receipt of this message by sending routing area update complete

In the analysis the Location Area Update, Routing Area Update and LA/RA Update BSS cell-reselection can be separated from each other.

Location Area Update

The LAU time is the period between Channel_Request and Channel_Release for LAU.

o First time stamp is taken from the Channel_Request for LAU

o The last time is the time stamp from Channel_Release after Location_Updating_Accept message.


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Routing Area Update

o First time stamp is taken from the Routing_Area_Request

o The last time is the time stamp from Routing_Area_Update_Complete

Data outage (LA/RA Update)

o First time stamp is taken from the first system information message after the last RCL/MAC block transmitted.

o The last time is the time stamp from Routing_Area_Update_Complete

The following figure (Figure 19) and table (Table 11) show the cell-reselection process with RAU on signalling.

MS BTS BSC New SGSN

DL TBF ASSIGNMENT

Routeing Area Update Accept

Routing Area Update Accept (PDCCH)Routing Area Update Accept

Location update request (SDDCH)

Routing Area Update complete (PDCH)Routing Area Update complete


Location update request

Location Update AcceptLocation Update Accept



P_Channel Required


Caneel Release (SDCCH)

SECURITY FUNCTIONS AS SET BY THE OPERATOR

Routing Area Update RequestRouting Area Update Request (PDTCH) Routing Area Update Request

Location area Update [ 2].

Routing area Update [ 3].

Cel

l res

elec

tion

dat

a O

utag

e


MS BTS BSC New SGSNMS BTS BSC New SGSN

DL TBF ASSIGNMENT

Routeing Area Update Accept

Routing Area Update Accept (PDCCH)Routing Area Update Accept

Location update request (SDDCH)

Routing Area Update complete (PDCH)Routing Area Update complete


Location update request

Location Update AcceptLocation Update Accept



P_Channel Required


Caneel Release (SDCCH)

SECURITY FUNCTIONS AS SET BY THE OPERATOR

Routing Area Update RequestRouting Area Update Request (PDTCH) Routing Area Update Request

Location area Update [ 2].

Routing area Update [ 3].

Cel

l res

elec

tion

dat

a O

utag

e


Figure 19 BSS and Application data cell-reselection outage in download with LAU/RAU


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Event name Time Channel Message

… … … …

Layer 3 Downlink 8:44:05.801 BCCH "SYSTEM_INFORMATION_TYPE_1"… … … …

Layer 3 Downlink 8:44:10.797 BCCH "SYSTEM_INFORMATION_TYPE_13"Cell Reselection 8:44:10.906 from 5691 to 5753Layer 3 Downlink 8:44:11.018 BCCH "SYSTEM_INFORMATION_TYPE_2"… … … …Layer 3 Uplink 8:44:11.997 RACH "CHANNEL_REQUEST"Layer 3 Downlink 8:44:12.101 CCCH "IMMEDIATE_ASSIGNMENT"Layer 3 Uplink 8:44:12.313 SDCCH "LOCATION_UPDATING_REQUEST"Layer 3 Downlink 8:44:12.353 SACCH "SYSTEM_INFORMATION_TYPE_6"Layer 3 Uplink 8:44:12.388 SACCH "MEASUREMENT_REPORT"Layer 3 Uplink 8:44:12.548 SDCCH "CLASSMARK_CHANGE"Layer 3 Downlink 8:44:12.764 SDCCH "CIPHERING_MODE_COMMAND"Layer 3 Uplink 8:44:12.784 SDCCH "GPRS_SUSPENSION_REQUEST"Layer 3 Uplink 8:44:13.020 SDCCH "CIPHERING_MODE_COMPLETE"Layer 3 Downlink 8:44:13.224 SDCCH "IDENTITY_REQUEST"Layer 3 Uplink 8:44:13.350 SACCH "MEASUREMENT_REPORT"Layer 3 Uplink 8:44:13.490 SDCCH "IDENTITY_RESPONSE"Layer 3 Downlink 8:44:13.697 SDCCH "LOCATION_UPDATING_ACCEPT"Layer 3 Uplink 8:44:13.799 SACCH "MEASUREMENT_REPORT"Layer 3 Downlink 8:44:14.168 SDCCH "MM_INFORMATION"Layer 3 Uplink 8:44:14.284 SACCH "MEASUREMENT_REPORT"Layer 3 Downlink 8:44:14.399 SDCCH "CHANNEL_RELEASE"… … … …

Layer 3 Uplink 8:44:16.258 PDTCH "ROUTING_AREA_UPDATE_REQUEST"… … … …

Layer 3 Uplink 8:44:16.752 RACH "CHANNEL_REQUEST"Layer 3 Downlink 8:44:16.829 CCCH "IMMEDIATE_ASSIGNMENT"… … … …

Layer 3 Uplink 8:44:16.258 PDTCH "ROUTING_AREA_UPDATE_REQUEST"RLC/MAC Uplink 8:44:17.401 PACCH "PACKET_RESOURCE_REQUEST"RLC/MAC Downlink 8:44:17.607 PACCH "PACKET_UPLINK_ASSIGNMENT"… … … …

RLC/MAC Downlink 8:44:17.886 PACCH "PACKET_DOWNLINK_ASSIGNMENT"… … … …

Layer 3 Downlink 8:44:18.950 PDTCH "ROUTING_AREA_UPDATE_ACCEPT"Layer 3 Uplink 8:44:18.964 PDTCH "ROUTING_AREA_UPDATE_COMPLETE"RLC/MAC Uplink 8:44:19.119 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"

… … … …

Table 11 LA/RA Update message flow from a Tom log

The Table 12 shows a measurement result from live network:

Table 12 Cell-reselection events with RAU

Cell-reselection events with RAU 1 2 3 4 5 6 7 8 9 Average RemarksLayer 3 DownlinkROUTING_AREA_UPDATE_COMPLETECHANNEL_REQUESTCHANNEL_RELEASEROUTING_AREA_UPDATE_REQUESTROUTING_AREA_UPDATE_COMPLETE

from (CI) 5691 5753 5692 5753 5692 5753 5691 5753 5691to (CI) 5753 5692 5753 5692 5753 5692 5753 5692 5753Comments 1)

1) System information reading failures (BSS fault)

LA/RA Update BSS cell-reselection (s)

Location Area Uptade (s)

Routing Area Update (s)

2.4

2.7

17.3 8.5

2.3

2.8

8.5 8.3 8.5 8.5 8.3 8.3 8.5 9.4

2.2 2.4 2.3 2.3 2.4 2.3 2.8 2.4

2.7 2.7 2.8 2.8 2.8 2.7 2.8 2.7


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11.2.2 Cell-reselection with combined RAU (NMO1, Gs interface required)

In case of combined LAU/RAU the RA Update is generated without LA Update. The time used for combined RAU (see Table 13 below) is much less compared to uncombined LAU/RAU in Table 11.

Event Time Channel Message… … … …

Layer 3 Downlink 11:19:03.529 BCCH SYSTEM_INFORMATION_TYPE_3Layer 3 Downlink 11:19:03.529 BCCH SYSTEM_INFORMATION_TYPE_4Layer 3 Downlink 11:19:03.529 BCCH SYSTEM_INFORMATION_TYPE_2Layer 3 Downlink 11:19:03.529 BCCH SYSTEM_INFORMATION_TYPE_3Layer 3 Downlink 11:19:03.529 BCCH SYSTEM_INFORMATION_TYPE_4Layer 3 Uplink 11:19:03.529 PDTCH ROUTING_AREA_UPDATE_REQUEST… … … …

Layer 3 Uplink 11:19:04.220 RACH CHANNEL_REQUEST… … … …

Layer 3 Downlink 11:19:04.220 CCCH IMMEDIATE_ASSIGNMENT… … … …

RLC/MAC Downlink 11:19:04.550 PACCH PACKET_TIMESLOT_RECONFIGURE… … … …

Layer 3 Downlink 11:19:04.620 PDTCH ROUTING_AREA_UPDATE_ACCEPT… … … …

Layer 3 Uplink 11:19:04.620 PDTCH ROUTING_AREA_UPDATE_COMPLETERLC/MAC Downlink 11:19:04.731 PACCH PACKET_DOWNLINK_DUMMY_CONTROL_BLOCKRLC/MAC Uplink 11:19:04.791 PACCH PACKET_DOWNLINK_ACK/NACKRLC/MAC Downlink 11:19:04.811 PACCH PACKET_UPLINK_ACK/NACKRLC/MAC Uplink 11:19:04.811 PACCH PACKET_CONTROL_ACKNOWLEDGEMENT… … … …

Table 13 Combined RA Update message flow from a To m log

11.3 Cell-reselect Hysteresis With cell reselect hysteresis (HYS) parameter the received RF power level hysteresis for required cell reselection can be defined.

The test results below show the different cell reselect hysterisis parameters’ impact on:

• BSS Outage

• Data Outage

The results of live test can be seen in Figure 20.


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2.2 2.44.3

6.7

10.9

14.5

0

2

4

6

8

10

12

14

16

6dB 8dB 10dB

Cell Reselect Hysterisis

Tim

e [s

]

Average Cell Reselection BSSOutage

Average Cell Reselection DataOutage

Figure 20 Cell Reselect Hysteresis in Ready state

By increasing the cell reselect hysteresis parameter the received signal level would degrade before cell reselection occurs. This in turn would degrade performance, so the recommendation is to keep it at its default value =6.

To avoid ping-pong effects, some antennas of sectors may need to be downtilted or re-planned to avoid overshooting or have dominance areas.


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11.4 PCU Balancing The proper allocation of the cells among PCUs can help to maximize the number of intra PCU cell re-selections, which is the most stable and shortest cell re-selection event.

• RLC/MAC layer: The intra PCU cell re-selection takes less time compared with inter PCU cell reselection

• LLC layer: In case of intra PCU cell re-selection the untransferred data is moved to new cell (BVCI) and the transfer can be continued on new cell without packet loss on higher layer, while in case of inter PCU cell re-selection the untransferred data is not moved to new cell (BVCI).

The following main rules can be followed:

• The cells of a BCF should be connected to the same PCU.

• The neighbor relations with high re-selection traffic should be connected to the same PCU.

• Modify (if it is needed) the LA/RA border for reducing the interPCU and interBSC cell re-selection.

• The neighbor relations in very bad signal and quality environment should be connected to the same PCU.

• Do not connect GPRS and EGPRS BCFs to separated PCU in case of island coverage, because of mobility issues and PCU and PCU-S limits with S11.5 in GPRS only networks.

There are connectivity related recommendations, which should be taken into account in PCU balancing:

• Take the live traffic figures into account, so the less traffic sites can have less CDEF, while sites with more traffic can have more CDEF

• Try to allocate min 4TSL DAP to all the BCFs

• Try to allocate max 8DAP pools to one PCU (1, 2 or 4 are even better)

• Try to keep balanced traffic allocation among PCUs (and inside DSPs, too)

• Try to keep the 75 % of connectivity limits for acceptable (E)GPRS data rate

• Try to connect less than 64 radio TSLs to one PCU to maximize EGPRS coverage in case of GPRS-EGPRS traffic mix

The geographical information is required to efficiently perform PCU cluster planning. The sites with same color are grouped under same PCU (see Figure 21).


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Figure 21 PCU allocation map

The load of PCU can be evaluated as followed: Number of default EGPRS/GPRS radio timeslots + EDAP timeslots divided by 256 (PCU capacity)

The following paragraphs show the PCU load analysis of a live network:

The load of PCU 2080: 244/256 =95% (Table 14). This PCU has very limited remaining capacity for territory upgrade. Therefore there is a high probability for all BTS connected to the same PCU to experiencing territory upgrade rejection.

The solution can be a site re-homing to another less loaded PCU.

Table 14 PCU reallocation information

Site 557 has been moved to less loaded PCU (at 22/09) and the blocking due to lack of PCU of site 5571 is drastically reduced (see Figure 22).


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NSEI=2080, BCSU=8, PCU=4 NSEI=2085, BCSU=7, PCU=4NSEI=2080, BCSU=8, PCU=4 NSEI=2085, BCSU=7, PCU=4

Figure 22 Blocking due to lack of PCU

Sites located in the same geographical area, along major roads should be grouped under same PCU and the total number of default EGPRS/GPRS radio timeslots + EDAP timeslots of 180 channels (180 out of 256) is recommended.

11.5 LA/RA Design It is important to avoid LA/RA border allocation between cell with high neighboring traffic.

Radio Aspect of LA/RA Design is listed below:

• The too big LA/RA will increase the paging, while the too small LA/RA will increase the LA/RA Update. So the balance should be found between too big and too small RA/RAs.

• The suboptimal LA/RA border design can significantly increase the signaling on air interface signaling channels and TRXSIG on LA/RA border cells, so the cell-reselection outage can be longer in this case because of congestion on signaling.

• The LA/RA border should be moved from those areas where the normal CSW and PSW traffic is very high. (Additional SDCCH capacity or a dynamic SDCCH may be allocated for the cells to handle extra LA/RA updates.)

• The combined RAU (NMO I with Gs) is shorter compared to MNO II.

In S11 backwards the GPRS resume always can cause a lot of RAs if GPRS MS has high CS call activity, but this behavior cannot be avoided by proper LA/RA design.

• In S11.5 the Resume is working without LA/RA update


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11.6 NACC Network Assisted Cell Change (NACC) is in Rel 4 of 3GPP GERAN, mandatory for R4 mobiles. Nokia’s S11.5 implementation is based on Rel4.

Both, autonomous and network controlled cell reselections are supported.

NACC can be used for intra-BSC cell changes. (Support of inter-BSC NACC specification is available in Rel 5)

NACC support is for MSs in RR Packet Transfer Mode only.

NACC shortens the cell reselection in two ways:

• Sending neighbour cell system information on PACCH to MS in packet transfer mode while it is camped on the serving cell

• By supporting PACKET SI STATUS procedure in a target cell

NACC is enabled/disabled with MML command ZEEM.

The following figures show the improvement achieved by NACC:

Cell Reselection DelaysOne-phase access, Intra-RA, Intra-PCU

Nokia 5140

0

0.5

1

1.5

2

2.5

3

NC0 NC0 + NACC

NC0 without NACC and with NACC

Tim

e (s

)

Application OutageData OutageCell Outage

23. Figure Improvement in cell re-selection time


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Cell Reselection DelaysTwo-phase-access, Intra-RA, Intra-PCU

Nokia 6230i

0

0.5

1

1.5

2

2.5

3

3.5

NC0 NC0 + NACC

Network Control Mode

Tim

e (s

)

Application OutageData OutageCell Outage

24. Figure Improvement in cell re-selection time


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12. Applications The improvement of the service based end-to-end user perception needs special attention on BSS parameter set.

The BSS optimization of end to end services are based on the signaling capacity, accessibility, TSL data rate, territory and cell outage (mobility).

In general the BSS parameters and features must be optimized for the most sensitive services, like interactive PoC.

12.1 Service Types

12.1.1 Conversational Services

The video telephony and VoIP services need conversational QoS setting, but these services cannot be used over (E)GPRS yet.

12.1.2 Streaming Services

Video downloading (on demand) is the typical streaming service.

The streaming services are very sensitive for data outage (mobility), so the BSS cell-reselection parameters and features (e.g. NACC) are very important and must be optimized.

12.1.3 Interactive Services

The interactive services, like PoC (Push to Talk over Cellular), WEB and WAP browsing, interactive games and Corporate VPN are heavily used in (E)GPRS networks.

The most delay sensitive interactive application is PoC.

In case of single PoC user in a cell the TSL data rate requirement is not that high (10-12 kbps) so the TSL data rate should not be maximized. But for capacity reason, when more than one user is camped on the same cell, the TSL data rate and territory must be maximized.

The following BSS parameters and features can be analyzed and optimized for better PoC functionality:

• Non-DRX mode, NMO I with Gs

• TBF Release Delay, TBF Release Delay Ext, BS_CV_MAX

• LA (MCA), Priority based QoS

• LA/RA design, NCCR, NACC

• Connectivity capacity

12.1.4 Background Services

The MMS, FTP and mail download services are working with low TSL data rate, small territory and long data outage as well.


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12.2 Dual Transfer Mode (DTM) Dual Transfer Mode (DTM) provides mobile users with simultaneous circuit-switched (CS) voice and packet-switched (PS) data services. This means that users can, for example, send and receive e-mail during an ongoing phone call.

The Planning Theory of DTM can be downloaded from the following link:


Information about DTM planning is available in DTM – Planning guidelines:


12.3 Push to Talk (PoC) Push to talk service support can be found on the links bellow:

Dimensioning guideline


Dimensioning tool


PM guide



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13. References [1] (E)GPRS Radio Networks – Planning Theory 3.0


[2] (E)GPRS Radio Networks – Dimensioning and Planning Guidelines 3.0


[3] DTM - Planning Theory


[4] DTM – Planning guidelines.


[5] (E)GPRS Radio Networks – Tools 2.0
