03 Rn20023en20gla0 (e)Gprs Radio Interface

8/13/2019 03 Rn20023en20gla0 (e)Gprs Radio Interface

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EGPRS Radio Interface

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1 © Nokia Siemens Networks RN20023EN20GLA0

EGPRS EXPLAINEGPRS Radio interface




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Module objectives

After c om pleting thi s l ea rni ng elem en t, the parti cipant wil l be ab le to:

Theory:

• Realize the difference between GPRS CSs and EGPRS MCSs• Explain the air interface principles such as modulation and link adaptation• Explain how mobility is handled in GPRS networks• Explain Network controlled Cell Reselection (NCCR) and Network Assisted Cell Change

(NACC)• Illustrate the interworking with LTE/UMTS




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CodingScheme Payload (bits)per RLC block Data Rate(kbps)*

CS1 181 9.05 / 8

CS2 268 13.4 / 12

CS3 312 15.6 / 14.4

CS4 428 21.4 / 20

More Data=

Less ErrorCorrection

GPRSPCU1+2

• CS1 & CS2 – Implemented in all BTS types without HW change

• CS3 & CS4 – not for Talk family BTS, Non EDGETRXs, CUs

D a t a

E r r o r

C o r r e c t i o n

GPRS Coding Schemes

GPRSPCU2

*first value includes the RLC header, the MAC header (excluding the USF), the spare bits and RLC information.Second value only RLC information (no headers)




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GPRS Coding Schemes- Link Adaptation

GPRS provides four coding schemes: Coding Scheme (CS) 1 to 4.

• EDGE TRXs and PCU 2 are required for CS-3/4.

• PCU1 gives support for CS-1 and CS-2 only.

• Talk family only supports CS-1 and CS-2.

Link Adaptation (LA) allows the PCU to select the most suitable CS for one TBF. The Link Adaptation (LA) algorithm selects the optimum channel coding scheme for a particular RLCconnection to provide the highest throughput and lowest delay available.

In PCU1 the LA algorithm is based on detecting the occurred RLC block errors the blockerror rate (BLER). The operator can define by parameters, whether a TBF uses either afixed coding scheme (CS-1 or 2) or Link Adaptation (LA) based on Block Error Rate (BLER).

In PCU-2 based LA is based on RXQUAL and BLER values

In GPRS RLC acknowledged mode RLC data blocks which are not correctly received have tobe retransmitted with the same Coding Scheme (CS).

• LA algorithm for EDGE (PCU-1 and 2) is mainly based on Bit Error Probability BEPvalues




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Frequency Planning: GPRS

0

2468

10121416

0 5 10 15 20 25C/I

k b p s

CS-1

CS-2

CS-3

CS-4

Minimum Average

TypicalNW C/I

Through-put for 1 TimeslotRelative cell radius of different GPRS

Coding Schemes (CS1=100%)Example, details depend on type of cell

100

81

71

45

84

7467

52

0

20

40

60

80

100

CS1 CS2 CS3 CS4

Hopping

Non Hopping

Simulations




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RLC/MAC Block Size: 428

BCS Size: 16

Precoded USF: 12

Data rate (kbps): 21.4

CS-4

GPRS Coding Schemes

interleaving

MAC

puncturing

rate 1/2 convolutional coding

BCS

MAC

20 ms

BCS

CS-1 CS-2 CS-3

RLC/MAC Block Size: 181 268 312

Block Check Sequence: 40 16 16Precoded USF: 3 6 6

Code Rate: 1/2 ~2/3 ~3/4

Number of bits: 456 588 676

Punctured bits: 0 132 220

Data rate (kbps): 9.05 13.4 15.6

57 57 57 57 57 57 57 57

456 bits

USF

USF

For CS 4 nocoding or

puncturing

is doneexcept for

USF




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EGPRS Implementation

EGPRS can be introduced gradually to the network where the demand is. EGPRS requires:

• EGPRS capable MS (supporting GPRS as well)

• Network HW readiness/upgrade (BTS and TRX)

• Transmission capacity upgrade (Abis and Gb!)

GMSK coverage

8-PSK coverage

AA-bis

Gb

Gn

BTS

BTS

BSC

SGSNGGSN

MSC

More capacity in interfacesto support higher data usage

EDGE capable TRX,GSM compatible

EDGE capableterminal

EDGE functionality in thenetwork elements




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EGPRS Modulation and Coding Schemes 1Ref: 3GPP TS 43.064

NOTE: The italic captions indicate the 6 octets (48) of padding when retransmitting an MCS-8 block withMCS-3 or MCS-6. For MCS-3, the 6 octets of padding are sent every second block (see 3GPP TS 44.060).

8,817610.530.53MCS-1

11,222410.530.66MCS-2

14,813,6

29648 +248 and 29610.530.85MCS-3

17,63521

GMSK

0.531.0MCS-4

22.444811/30.37MCS-5

29.627.2

59248 +54411/30.49MCS-6

44.82x44820.360.76MCS-7

54.42x54420.360.92MCS-8

59.22x5922

8PSK

0.361.0MCS-9

Data ratekbps

Raw Datawithin one

Radio Block

RLCblocks

perRadioBlock

(20ms)

ModulationHeaderCode rateCode rateScheme




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MCS-7

22

28

MCS-337

MCS-444

MCS-556

MCS-674

5656

MCS-86868

MCS-974 74

redundancy fromchannel coding

RLC data block,number of bytes

RLC/MAC block(radio block)

11.2 kbps

14.8 kbps

17.6 kbps

8.8 kbps

22.4 kbps

29.6 kbps

44.8 kbps

54.4 kbps

59.6 kbps

MCS-1

MCS-2

In wireless networks the quality of the connection canchange from very good to very poor in short time

EGPRS has nine different Modulation and CodingSchemes (MCS-1 – MCS-9) in order to optimize theperformance in different radio conditions. All codingschemes have different amount of robustness and errorcorrection.

• When user bit rate is low, robustness is high (e.g.MCS-1)

• When user bit rate is high, robustness is low (e.g.MCS-9)

Two modulations are used:

• GMSK (Gaussian Minimum Shift Keying) for MCS-1 –MCS-4

• 8-PSK (8-Phase Shift Keying) for MCS-5 – MCS-9

The MCS that offers the best performance in current radioenvironment should be selected

Automatic selection of most suitable MCS is called linkadaptation (LA) . The selection is based on link qualitymeasurements

EGPRS Modulation and Coding Schemes 2




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GMSK & 8-PSK - Phase State Vectors

22,5° offset

to avoid zero crossing

GMSK

8PSK

(0,0,1)

(1,0,1)

(0,0,0) (0,1,0)

(0,1,1)

(1,1,1)

(1,1,0)

(1,0,0)

Time

Envelope (amplitude)

Time

Envelope (amplitude)




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Phase state vector

Minimum Amplitude -15 dB

‚usefull‘ Amplitude 0 dB

maximum Amplitude +4 dB (for MS)

Q 0

I0

• 8-PSK (Phase Shift Keying) hasbeen selected as the newmodulation added in EGPRS

• 3 bits per symbol• 22.5° offset to avoid origin

crossing (called 3 Π /8-8-PSK)

• Symbol rate and burst lengthidentical to those of GMSK

• Non-constant envelope highrequirements for linearity of thepower amplifier

• Because of amplifier non-linearities, a 2-4 dB powerdecrease back-off (BO) istypically needed, NSNguarantees a BO of 2 DB forBTS




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Burst Structure

- Burst structure is similar with current GMSK burst, but term 'bit' is replaced by 'symbol‘

- One symbol has 3 bits when using 8-PSK- Training sequence has lower envelope variations

- it is possible to use 8-PSK and GMSK on adjacent timeslots (not for MS!)

- In case of max output power only, back-off applied to 8-PSK (there is no DL powercontrol)

TSL1 TCH

GMSK

TSL2TCH

GMSK

TSL3TCH

GMSK

TSL4TCH

GMSK

TSL5PDTCH8-PSK

TSL6PDTCH8-PSK

TSL7PDTCH8-PSK

TSL0 BCCH GMSK

P(dBm)

t (us)




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8-PSK Modulation – Back-off Value

Since the amplitude is changing in 8-PSK the transmitter non-linearities can be seen in thetransmitted signal.

These non-linearities will cause e.g. errors in reception and bandwidth spreading.In practice it is not possible to transmit 8-PSK signal with the same power as in GMSK due tothe signal must remain in the linear part of the power amplifier.

The back-off value is taken into account in linkbudget separately for UL / DL and bands:900/850, 1800/1900)

Too high initial MCS (8PSK) can lead tounsuccessful TBF establishment, if the MS ison cell border with low signal level (so theback-off is taken into account) and / or low C/I

Back Off for MS (4dB) is higher than for BTS(2dB)Peak to Average of about 3,2 dB

Pin

Pout

Back Off= 4 dB

Compression point

Pout




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EGPRS Data Treatment Principle in RF Layer

User data

"Additional info" that does not require extra protection

Header part, robust coding for secure transmission

Adding redundancy

Puncturing of thecoded info




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EGPRS Channel Coding (MCS-9)

EGPRS channel coding is done separatelyfor data and header, as shown in the figurefor MCS-9 downlink.

Coding of data part:

• Data part includes user data, twoinformation from RLC header, BCS(block check sequence) and tail bits.

• Coded using 1/3 convolutional code.

• Punctured with a selectablepuncturing scheme (P1, P2 or P3).

• Two separate RLC blocks for MCS 7,8 and 9.

Header part:

• Includes RLC/MAC headerinformation including information onthe coding of the data part (like usedpuncturing scheme).

• Convolutional coding + puncturing.

USF

encodedUSF P2 P3

P1 P2 P3puncturing

puncturing

1stburst

2ndburst

3rdburst

4thburst

block coding

P1

header FBI+E

data 2

BCS tail

1/3 convolutional coding

mother code

protectedheader

4 TDMAbursts = 20 ms

FBI+E

data 1

mother code

BCS tail

puncturing

1/3 convolutional coding




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EGPRS MCS Families

37 octets 37 octets 37 octets37 octets

MCS-3

MCS-6

Family A

MCS-9


MCS-2

MCS-5

MCS-7

Family B

22 octets22 octets

MCS-1

MCS-4

Family C

34+3 octets

MCS-3

MCS-6Family Apadding

MCS-8


The MCSs are divided into different families A, B and C

Each family has a different basic unit of payload: 37 (and34), 28 and 22 octets respectively.

Different code rates within a family are achieved bytransmitting a different number of payload units within oneRadio Block.

For families A and B, 1 or 2 or 4 payload units aretransmitted, for family C, only 1 or 2 payload units aretransmitted

When 4 payload units are transmitted (MCS 7, MSC-8 andMCS-9), these are splited into two separate RLC blocks(with separate sequence BSN numbers and BCS, (BlockCheck Sequences)

• The blocks are interleaved over two bursts only, forMCS-8 and MCS-9.

• For MCS-7 the blocks are interleaved over four bursts

34+3 octets




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EGPRS Link AdaptationLink Adaptation (LA)

The task of the LA algorithm is to select theoptimal MCS for each radio condition to

maximize RLC/MAC data rate, so the LAalgorithm is used to adapt to situations wheresignal strength and or C/I level is low andchanging slowly with time. Ideal LA would followthe envelope of the throughput of differentMCSs.

- The PCU selects the data block andadditionally selects the MCS depending on radiolink quality and amount of available dynamic

Abis channels

- LA is done independently for each UL and DLTBF on RLC/MAC block level, but the LAalgorithm is same for uplink and downlink

- The MCS selection is not the same in case ofinitial transmission and retransmission

- LA algorithm works differently for RLCacknowledged mode and unacknowledged mode

- RLC control blocks are transmitted with MCS-1coding0

10

20

30

40

50

60

0 5 10 15 20 25 30

MCS-1MCS-2MCS-3MCS-4MCS-5MCS-6MCS-7MCS-8MCS-9

Simulation ofFrequency HoppingNetwork (TU 50 Km/h)

C/I

kbps




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Link Adaptation is ‘slow’ process and is enabled to adapt to

• path loss

• shadowingIncremental Redundancy (IR) is another enhancement of EGDE compared to GPRS. It isbetter suited to compensate fast fading

Incremental Redundancy works only for RLC acknowledged mode, the retransmissionprocess is based on IR in UL and DL.

• Support of IR for MS is mandatory

• Support of IR for BTS it is optional and implemented in all NSN BTS types supportingEGPRS.

LA must take into account

• if IR combining is performed at the receiver (UL)

• the effect of finite IR memory (in case of full memory buffers it may be necessary to switch

to lower MCSs in order to allow the buffers especially in MS to get empty).

EGPRS Link Adaptation & Incremental Redundancy




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Incremental Redundancy (IR)

IR is a combination of two techniques sometimes called

ARQ type II:• Automatic Repeat reQuest (ARQ)

• Forward Error Correction (FEC)

In the ARQ method the receiver detects the errors in areceived RLC block and requests and receives a re-transmission of the same RLC block from the transmitter.

The FEC method adds redundant information to the re-transmitted information at the transmitter and the receiveruses the information to correct errors caused bydisturbances in the radio channel

IR needs no information about link quality in order toprotect the transmitted data but can increase thethroughput due to automatic adaptation to varyingchannel conditions and reduced sensitivity to link qualitymeasurements

For each MCS there are 2 or 3 Puncturing Schemes (PS)defined

Datablock

P1 P2 P3

One MCS

1. transmission 1st re-transmissionupon reception

failure

2nd re-transmissionupon reception

failure

Transmitter

Receiver

P2 P3P1

P1

P1

P1

P2

P2 P3

Protection level 1

Combination: Protection level x 2

Combination: Protection level x 3

No datarecovered

Stored

No datarecovered

Stored

EGPRS Incremental Redundancy




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Modulation and Coding Schemes - MCS Selection

The PCU selects the used MCS. This selection can be divided in four classes:

• Initial MCS to be used when entering packet transfer mode (set by parameters)

• Modulation selection

• MCS selection for initial transmissions of each RLC block (Link Adaptation, LA)

• MCS to be used for re-transmissions (must be the same family, only for ACK mode )

Link Adaptation algorithm depends if RLC protocol works in acknowledged or unacknowledged mode. Inacknowledged mode, LA algorithm is designed to optimize channel throughput in different radio conditions. Inunacknowledged mode, the algorithm tries to keep the TBF below a specified Block Error Rate (BLER) limit.

The Link Adaptation (LA) algorithm for EGPRS is the same for PCU 1 and 2. It can be disabled byparameter. After the start of the TBF LA starts to work based on Bit Error Probability (BEP) measurementsperformed at the MS (downlink TBF) and the BTS (uplink TBF).

In DL case the MCS selection is based on EGPRS Channel Quality Report received in EGPRS PACKETDOWNLINK ACK/NACK message sent from the MS to network using PACCH to indicate the status of thedownlink RLC data blocks received.

The MCS selection is based on using the BEP (Bit Error Probability) measurement data which contains thecurrent averaged BEP value as well as the variation of this value (CV-Coefficient of Variation).

In UL case the MCS selection is based on the respective BEP measurement values which are measured bythe BTS and given to PCU in the UL PCU frames.




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Modulation and Coding Schemes - MCS Selection

CV_BEP_0

CV_BEP_1

CV_BEP_2

CV_BEP_3

CV_BEP_4

CV_BEP_5

CV_BEP_6

CV_BEP_7

2.00 >CV_BEP >1.75

1.75 >CV_BEP >1.50

1.50 >CV_BEP >1.25

1.25 >CV_BEP > 1.00

1.00 > CV_BEP > 0.75

0.75 > CV_BEP > 0.50

0.50 > CV_BEP > 0.25

0.25 > CV_BEP > 0.00

Value ranges are the same for 8-PSK and GMSK!

big variations

stable

MEAN_BEP Range of log10(actual BEP)

-3.60 - -3.44

MEAN_BEP_25 -2.80 - -2.64

MEAN_BEP_26 -2.96 - -2.80

MEAN_BEP_27 -3.12 - -2.96

MEAN_BEP_28 -3.28 - -3.12

MEAN_BEP_29 -3.4 - -3.28MEAN_BEP_30

MEAN_BEP_31 < -3.60

MEAN_BEP_0 > -0.60

MEAN_BEP_1 -0.64 - -0.60

MEAN_BEP_2 -0.68 - -0.64

MEAN_BEP_3 -0.72 - -0.68

MEAN_BEP_4 -0.76 - -0.72

good

poor

BEP as well as CV_BEP valuesare measured and reported

by MS (DL) and BTS (UL) to PCUMore details 3GPP 46.008

…..

…..




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Mobility for (E)GPRS

BSC-1

RA-1

Old cell New cell

Cell selection and ReselectionIn the GMM state READY the MS has to indicate cell changes towards the SGSN.Unlike in GSM dedicated mode, there is no handover for (E)GPRS networks. Existing idle mode

criteria are used to select the best suitable cell. In case of cell change the MS has to initiate a cellupdate to SGSN (the TBF in the old cell simply drops)When in GSM the LA changes during a call the LA update is initiated by the MS when the call ends.In (E)GPRS there is no handover and the MS has to do first the RA/LA update, before the datatransfer can be continued on LA/RA border.In all cases (as well without RA border) there is a longer interruption time called ‘cell outage’ in thedata transfer. Most non-real time applications manage to recover data losses.For an MS in DTM mode the cell update happens after the handover.

SGSN-1




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The cell update procedure

empty LLC frame

FLUSH-LL

UL-UNITDATA( TLLI, empty LLC frame )

( TLLI, old BVCI, new BVCI,new NSEI if SGSN supports Inter-NSE re-routing )

FLUSH-LL-ACK( TLLI, Flush Action: LLC-PDUs deleted or transferred,

new BVCI, number of octets affected,new NSEI, PFC transfer result )

DL-UNITDATA( TLLI, deleted LLC frames of AM )

to new BVCI

BSC/PCU SGSN

The MS initiates the cell update. The MS sendsempty LLC frame to the SGSN. RLC/MAC isused to transmit the LLC frame from the MS tothe BSS. The MS is identified by the TLLI.

A cell change took place within one RA and oneNSE (=PCU):The LLC-PDUs for the TLLI stored at the „oldBVCI“ are either moved to the „new BVCI“ insame PCU.

A cell change took place within one RA but twoNSEs (different PCUs):The LLC-PDUs for the TLLI stored at the „old

BVCI“ are deleted . A transfer of LLC-PDUs can be only requestedby the SGSN, if the „old BVCI“ supports Inter-NSE re-routing.




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Cell Selection / Re-selectionThe network may request measurement reports from the MS and control its cell re-selection (within GSM cells and towards 3G or LTE cells) when MS is in GMM ready state.

Depending on the NC ( Network Control ) mode set by the network, the MS shall behave

as follows:• NC0 : Normal MS control; the MS shall perform autonomous cell re-selection

• NC1: MS control with measurement reports; the MS shall send measurement reports tothe network and shall perform autonomous cell re-selection

– NC1 is not supported

• NC2 : Network controlled; the MS shall send measurement reports to the network withNetwork Controlled Cell Reselection (NCCR). The feature is not applicable for DTMcapable devices in dedicated or DTM mode.

BSC-1PCU

Old cell New cell

SGSN-1

With NC0 the MS decideswhen to change and to

which cell to changeWith NC2 the PCU tells to

the MS when to changeand to which cell to change

NC2

NC0NC2

NC0




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Cell Selection / Re-selection NC0

Standard implementation with NC0: MS cell selection/re-selection is controlled by thefollowing criteria, normally the MS chooses the strongest cell

- Path loss criterion (C1) or if defined:- Cell reselection criteria (C2)

These criteria are used for the cell reselection during GMM ready in the similar way asin GMM standby state (‘cell reselect hysteresis’ parameter is considered by MS only inGMM Ready or in GMM Standby at RA border)

BSC-1

RA-1

Old cell New cell

SGSN-1

With NC0 the MS decideswhen to change and to

which cell to change

NC0




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GSM / (E)GPRSGSM / (E)GPRS

WCDMA (CS and PS)WCDMA (CS and PS)

LTE (only PS)LTE (only PS)

Inter System interworkingCell reselection as well is the mechanism intersystem interworking. Changing the System normally isassociated with a RA change.

Real cell sizes can be of course different and depend mainly on the used band.

In UMTS there are handovers for PS services but the transition to (E)GPRS is handled by CellChange Command.LTE only knows PS services (Real Time and Non Real Time). In LTE there are handovers, but thetransition to (E)GPRS is handled in a simular way as in (E)GPRS.

Redirected release is used, when LTE coverage ends. Inter System Network Assisted Cell change(IS-NACC) is an enhancement, which shortens the outage time.

Handover (Cell Change command and cell reselection)

Cell reselection

in idle and

packet transfer

GERAN

UTRAN

eUTRAN

Redirected

release and/or

IS-NACC

pluscell reselection

NC0NC2




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Cell Selection / Re-selection – NC2

NC2 : Network control is deployed with Network Controlled Cell Reselection (NCCR).The MS has to send measurement reports and the PCU will make the decision toreselect a certain cell based on C31/C32 criteria.

• C31: Signal Strength threshold criterion

• C32: Cell ranking

NC2 only applies to GMM (GPRS Mobility Management) Ready state.

In GMM Standby state, the MS will always use NC0 mode!

TBF TBF Ready timer

RR Packet Transfer Mode RR Packet Idle Mode Time

Measurement Reports with NC2Measurement Reports with NC2

Ready timer

NC2




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Cell Selection / Re-selection – C31/32

C31 Signal Strength threshold criterion and C32 Cell ranking criteria have been initiallydesigned to be broadcast on the Packet Broadcast Channel (PBCCH) which is no longer supported.With NCCR the PCU makes use out of the independent set of cell (re)selection parameters

internally, without PBCCH.C31/C32 offers the same set of functions as C1 and C2 but independent parameters are nowpossible. That means for MS in GMM Ready the cells can be bigger or smaller compared to Idlemode cell sizes.

With C31/C32 it is additionally possible to define priorities for each neighbor cell, what enables toprefer some cells not because of level, but because of priorities. Cell selection criteria are defined in3GPP 45.008.

• MS is commanded with NCCR to select the cell with the highest C32 value from those having thehighest priority class and fulfilling the C31 criterion (if none fulfills C31, then only C32 is applied)

• The priority classes may correspond to different Hierarchical Cell Structures (HCS) layers

GERAN 900 MacroGERAN 900 Macro

GERAN 900 MicroGERAN 900 Micro

GERAN 1800GERAN 1800

HighestPriority

2nd priority2nd priority

GERAN 900 MicroGERAN 900 Micro

GERAN 1800GERAN 1800

HighestPriority

Usage of Prioritiescan lead to pingpong behavior!

and needs carefulplanning

NC2




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Cell Selection / Re-selection - NCCR (NC2)

NCCR (Network Controlled Cell Re-selection)

• Enables the network to order a cell re-selection instead of the autonomous selection done by the

mobile station based on the measurement reports.• The PCU can command the MS to change cells and decides about the target cell

• Besides the C31 /C32 criteria NCCR can be based on the following criteria:

– Power budget (PBGT) pushes EGPRS capable MSs to EGPRS cells and non-EGPRS capableMSs to non-EGPRS capable cells

– Quality control (QC) triggers NCCR when the quality of the serving cell t ransmission dropseven if the serving cell signal level is good or the throughput gets low ( in case of timeslot sharingfor example).

– Cell attractiveness can be defined on neighbor basis depended on the capabilities of eachneighbor cell (e.g. if CS-3/CS-4 or EGPRS support is given there or not)

GERAN

Frequency 2Frequency 2Frequency 1Frequency 1

NC2




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IS - NCCR (NC2)

IS-NCCR (Inter System - Network Controlled Cell Re-selection)

• Service-based IS-NCCR selects 3G network according to SGSN Service UTRAN CCO (Cell

Change Order) BSSGP procedure even if the serving GSM cell signal level is good.• Coverage-based IS-NCCR selects 3G network as soon as it is available or when GSM coverage

ends, depending on operator choice.

• Decision is based on the reported UMTS neighbors.

GSM / (E)GPRSGSM / (E)GPRS

WCDMA (CS and PS)WCDMA (CS and PS)

GERAN

UTRAN

NC2


http://slidepdf.com/reader/full/03-rn20023en20gla0-egprs-radio-interface 32/39




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NACC for NC0 - CCN Mode

A new mode, Cell Change Notification (CCN ), is needed for a MS in NC0 mode in order to make use ofNACC feature

- MS in NC0 mode can enter CCN mode- MS must be in Transfer Mode- Both NW and the MS must support CCN- The serving and the target neighbor cell must support CCN mode

The CCN Activity support info is in:- SI13 for serving cell- SI2quater for the neighbor cell

Mobile stations supporting NACC have to support the Packet PSI/SI Status procedures

Procedurefor NC0

NC0

When MS sees another cell to bebetter, then it sends info aboutwhich cell it intends to go and waits

for response from network

PSI14 is a new PSI used only for NACC feature

-It is a normal PSI , but the message shall be send to MS only in PACKETNEIGHBOUR CELL DATA –message

-Support of sending PSI14 message on PACCH as a plain PSI14 message, is notimplemented, PBCCH in the target cell is needed.




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NACC for NC0 (Network Control)MS Autonomous Cell-reselection

MS Source cell

C1, C2criterion triggers

Target cell

Current TBF on sourcecell is aborted

SI message

SI message

SI message

SI message

All required (P)SImessage received

data

Channel request

assignment

without NACC

MS Source cell

C1, C2,criterion triggers

Target cell

Current TBF on sourcecell is aborted

PACKET CELL CHANGE NOTIFICATION

PACKET NEIGHBOUR CELL DATA #1…N

PACKET CELL CHANGE CONTINUE

data

Channel request

assignment

PACKET (P)SI STATUS

PACKET SERVING CELL DATA #1

PACKET SERVING CELL DATA #N

with NACC

Shorter outage

NC0




35


GERANGERAN

Inter BSC, Inter System , LTE - NACC

LTELTE

UMTSUMTS

GERANGERAN

LTE-NACC

UMTSUMTS

GERANGERAN

IS–NACC

NACC as functionality is working within one BSC onlyInter-BSC (IB) - NACC allows to use NACC at BSC bordersIB – NACC is a prerequisite for LTE-NACC and Inter system (IS)-NACC however LTE-NACC could

run independently from IS-NACC. In order to enable IS-NACC or LTE–NACC IB-NACC must beactivePacket SI Status procedures are supported in case of inter-BSC cell reselection or cell reselectionfrom 3G as it is done currently. Similarly, support in case of cell change from LTE to GSM will beprovided as well.Feature is applicable only to PCU2 .

BTS 2BTS 1

NACCIB-NACC

BSC 1

BSC 2




36


GERANGERAN

Inter BSC - NACC

GERANGERAN GERANGERAN

With I B-NACC the NACC performance improvement can now be realised across the entire RG20(BSS) GSM/ EDGE Network.Once the MS determines the target cell it delays cell reselection and sends a PCCN message to the

BSC/PCUThe BSC responds with PACKET NEIGHBOR CELL DATA PNCD message(s) that include theSystem Information SI1, SI3 and SI13 of the target cell.When all data is sent the BSC/PCU sends the PACKET CELL CHANGE CONTINUE PCCCmessage.RIM support on Gb and in SGSN is required

BTS 2BTS 1

IB-NACC

BSC 1 BSC 2

SGSN

Neighbour information via SGSNs is exchanged beetween BSCsautomatically, when RAN information management (RIM) is active.

RIM works as well between different SGSNs

MS gets in old cell all requiredinformation about new cell

Neighbor information




37


GERANGERAN

Inter System and LTE - NACC

LTELTE

UMTSUMTS

LTE - NACCIS - NACC

The Inter System NACC capability from UTRAN to GSM/EDGE enables an RNC to request NACCReports from a BSC, which are used when an MS executes a Cell Change from a WCDMA Cell to aGSM/EDGE Cell

The Inter System NACC for LTE capability from LTE to GSM/EDGE enables an eNB to requestNACC Reports from a BSC, which are used when an MS executes a Cell Change from an LTE Cellto a GSM/EDGE Cell

As with Inter-BSC NACC, the SI1, SI3 and SI13 Information is exchanged via RIM.

eNodeB

RNC

BSC

BTS

NodeB

SGSN

MME

S3/Gn

IuPS

Iub

Gb Abis

S1

MS gets in old cell all requiredinformation about new cell

RIM




38


GERAN f1GERAN f1

Interworking with LTE/UMTS

LTE f1LTE f1

2G/LTE interworking features are introduced which allow from the GSM network point of view to:- Perform cell reselection to LTE (LTE System Information)- Perform IS-NACC from LTE to GSM

A MS in idle and Packet transfer in (E)GPRS without NCCR support is performing Cell Reselectionbased on the same criteria.

Autonomous cell reselection to LTE is based on new concept of absolute priorities .Information about E-UTRAN cells is introduced in SI2quater New priority-based system information for managing the cell reselection to UTRAN (instead oflegacy cell ranking algorithm) is introduced as well and it is mandatory to use this algorithm for E-UTRAN MS if MS supports UTRAN.UE reselects to the inter-RAT cell with the highest priority among the ones, where the measurementcriteria is/are fulfilled.

UMTS f1UMTS f1

GERAN f2GERAN f2

UMTS f2UMTS f2

LTE f2LTE f2

gsmPriority = ?

gsmPriority = ?

ltePriority = ?

ltePriority = ?

wcdmaPriority = ?

wcdmaPriority = ??

?

?

Priorities have range from0 to 7, high value means high

priority

?? ?

?


http://slidepdf.com/reader/full/03-rn20023en20gla0-egprs-radio-interface 39/39



Case 2:If LTE has higher priority

Case 1:If LTE has lower priority

Cell Reselection to LTE

GERANHigher priority

GERAN

Higher priority

LTELower priority

LTELower priority

GERANLower priority

GERAN

Lower priority

LTEhigher priority

LTEhigher priority

UE reselects to LTE cell as soon as UEenters the area with poor 2G coverage

and LTE cell is ‘good’ enough

UE reselects to LTE cellas soon as possible

New concept is based on unambiguous cell reselection priority order between different RATswithout predefined offsets.Direct comparison between signal levels of different RATs is no longer requiredIt was concluded from the 2G/3G interworking experience that such a comparison may lead to ping-pong effect especially if deployment of cells with different size is considered (large UMTS cell andseveral small GSM cells)Only minimum signal strength criteria of the neighbouring cells are considered for higher priority cells(and also minimum quality criteria in case of 3G cell)Priorities have to be set with care, coverage of the different solutions and amount of MSs supportingUTRAN, LTE should be input.

Documents

03 Rn20023en20gla0 (e)Gprs Radio Interface