gprs edge optimization

04/19/2023 Prepared by Mohyedeen Alkousy 1

GPRS/EDGE Optimizationin Huawei Networks


1. GPRS /EDGE Review

2. GPRS/EDGE Algorithms

3. GPRS/EDGE Optimization Parameters

4. GPRS/EDGE Problem Analysis

5. GPRS/EDGE example Case Analysis

Topics Presented


GPRS 52-Multiframe


GPRS Logical Channels

CONTROL CHANNELS TRAFFIC CHANNELS

PBCCH PDTCH

PPCH PACCH

PAGCH

PNCH


TBFs Multiplexing

MS2: EDGE

MS3: EDGE

MS6: GPRS

MS5: EDGE

USF4

USF2

USF4

USF3

USF2

USF1

MS1: GPRS

MS4: GPRS

USF4

USF2

USF4

USF3

USF2

USF1


MO Packet Transfer


MT Packet Transfer


GPRS VS EDGE

GPRS EDGE

Modulation GMSK GMSK + 8PSK

Link Quality Control LA LA +IR

Header Coding Same as payload Separate and robustRLC Window Size 64 RLC Blocks 1024 RLC Blocks

LQ Measurement BER BEP


GPRS VS EDGE

Coding scheme

Modulation

RLC blocks/radio blocks

FEC code rate

User bits/20ms

Bit rate (bps)

CS-1 GMSK 1 0.45 160 8000CS-2 GMSK 1 0.65 240 12000CS-3 GMSK 1 0.75 288 14400CS-4 GMSK 1 n/a 400 20000

MCS-1 GMSK 1 0.53 176 8800MCS-2 GMSK 1 0.66 224 11200MCS-3 GMSK 1 0.85 296 14800MCS-4 GMSK 1 1 352 17600MCS-5 8-PSK 1 0.38 448 22400MCS-6 8-PSK 1 0.49 592 29600MCS-7 8-PSK 2 0.76 448+448 44800MCS-8 8-PSK 2 0.92 544+544 54400MCS-9 8-PSK 2 1 592+592 59200


Protocol Stack


Same as BCCH carrier functionality but for PS only

PBCCH Carrier


• GPRS Mobility Management (GMM)• Radio Resource management (RRM)• Link Quality Control (LQC)• Uplink power control• Cell selection/reselection

GPRS/EDGE Algorithms


GMM StatesId

le S

tate

In GPRS IDLE the subscriber is not attached

to the GPRS Mobility Management. The MS and

SGSN context hold no location or routing information for the

mobile. The GPRS Mobile is seen as not reachable for PTP data transfers. PLMN selection and

reselection are performed by the MS. St

andb

y St

ate

In standby state the subscriber is attached to

the GPRS Mobility Management. The MS and the SGSN have established

MM contexts for the subscribers IMSI. The subscriber may now

receive pages for data transfers. Transmission and reception of data is

not possible in this state. MS performs GPRS cell reselection and routing

area MS updates SGSN if it enters a new RA MS may

activate or deactivate PDP contexts.

Read

y St

ate

The MS performs MM procedures to notify the network with the actual selected cell. GPRS cell selection and reselection may be done by the MS, or optionally controlled by the network. An identifier of the cell is placed in the BSSGP header of the packet data from the MS. The MS may send and receive PTP PDUs in this state. The network initiates no network pages for an MS in the Ready State.


GMM States


GPRS/EGPRS link quality control is implemented to adjust GPRS/EGPRS coding schemes dynamicallyaccording to the radio link quality during packet data transmission. It enables coding schemes to adapt tothe variation of the radio environment, maximizes the data throughput, and increases the data rate andsystem capacity.

Link Quality Control Algorithm


LQC in GPRS


GPRS LQC Parameters

MO Parameter ID Parameter Name Recommended Value

GCELLPSCS UPFIXCS Uplink Fixed CS Type UNFIXED

GCELLPSCS UPDEFAULTCS Uplink Default CS Type CS1

GCELLPSCS UPTHDCSUPGRADE1 Uplink TBF Threshold from CS1 to CS2 5



GCELLPSCS UPTHDCSDEGRADE1 Uplink TBF Threshold from CS2 to CS1 10



GCELLPSCS DNFIXCS Downlink Fixed CS Type UNFIXED

GCELLPSCS DNDEFAULTCS Downlink Default CS Type CS2

GCELLPSCS DNTHDCSUPGRADE1 Downlink TBF Threshold from CS1 to CS2 5



GCELLPSCS DNTHDCSDEGRADE1 Downlink TBF Threshold from CS2 to CS1 10




EDGE LQC

LA Mode• In LA mode, the network side adjusts channel coding schemes dynamically

according to the link quality to achieve the maximum throughput. The MS measures the downlink quality; the BTS measures the uplink quality. The network side determines an appropriate coding scheme according to the radio link measurement report sent from the MS. For the cells where the signal quality on the Um interface is good, the link quality control mode is generally set to LA.

IR Mode• In IR mode, the transmitter retransmits data blocks in puncturing-scheme-based

code diversity mode instead of in time diversity mode to increase redundancy. The receiver does not discard erroneous packets but stores them and combines and decodes them together with the soft information of the same data block. In this way, the gains of channel coding and time diversity can be obtained at the same time. Therefore, in the case that the channel quality is ensured, the BLER decreases and the throughput increases. For the cells where the signal quality on the Um interface is poor, the transmission performance of radio links is comparatively good. In such a case, the link quality control mode is generally set to IR.


EDGE LQC Parameters

MO Name Parameter NameRecommended Value

GCELLEGPRSPARA

Link Quality Control Mode IR

GCELLEGPRSPARA Uplink Fixed MCS Type UNFIXEDGCELLEGPRSPARA Uplink Default MCS Type MCS2GCELLEGPRSPARA

Downlink Fixed MCS Type UNFIXED

GCELLEGPRSPARA

Downlink Default MCS Type MCS6


Resources Utilization Parameters

MO Parameter Name Recommended Value

GCELLPSCHM Maximum Rate Threshold of PDCHs in a Cell 100

GCELLPSCHM Uplink Multiplex Threshold of Dynamic Channel Conversion 20

GCELLPSCHM Downlink Multiplex Threshold of Dynamic Channel Conversion 20

GCELLPSCHM PDCH Uplink Multiplex Threshold 70

GCELLPSCHM PDCH Downlink Multiplex Threshold 80

GCELLPSCHM Level of Preempting Dynamic Channel Level:0

GTRXCHAN PDCH Channel Priority TypeEGPRS Normal Priority

GTRXBASE Maximum Number of PDCH 8


• The formula which determine the output power of the Mobile station :

Where:

PDCH Uplink output power for every independent link 39dBm for EGSM , 36dBm for DCS

: Alpha, Specific Power control, parameter set by the network side.the received Rxlev of the mobile station. :MS_TXPWR_MAX_CCH

Uplink Power Control



GAMMA

Higher Output Power

Lower Output Power

ALPHA

Lower Output Power

Higher Output Power


• N3101/N3103 and N3105• PAN (Piggybacked ACK/NACK)• T3168• NOM• T3192• Non DRX Timer• BS_CV_MAX

GPRS/EDGE Optimization Parameters


Counter N3101

DL RLC Data Block or UL Packet ACK/NACK

UL RLC Block Not Valid

N3101 +1UL RLC Block Not Valid

N3101 +1UL RLC Block Not Valid

N3101 +1


Counter N3103

Uplink Data Block (CV=0)

Packet Uplink Ack/Nack (FAI=1)

Packet Control Ack(or Access Burst 8bit)

Packet Uplink Ack/Nack (FAI=1)

Packet Control Ack(or Access Burst 8bit)

N3103 +1

N3103 +1


Counter N3105

DL RLC Data Block (RRBP)

DL Packet Ack/NACK

N3105 +1

N3105 +1

DL RLC Data Block (RRBP)

DL Packet Ack/NACK


N3101/N3103/N3105 Settings

MO Parameter ID

Parameter Name

Recommended Value

GCELLSTANDARDOPTPARA N3101 Maximum Value of N3101 20




There are three network operation modes: .

Network Operation Mode (NOM)

Network operation mode I :is used when the system is configured with the Gs interface.

Network operation mode II: is used when the system is not configured with the Gs interface and the PCCCH is not configured.

Network operation mode III is used when the system is not configured with the Gs interface and the PCCCH is configured.


BSC

Interface in the core network that connects SGSN with MSS for paging coordination purposes.

Gs Interface

MSC Server

SGSN

PCU

BTS

A interface Gb interface

Gs Interface


• Coordinating the paging requests between CS and PS domain is necessary to avoid paging failure

• There are different solutions to this problem:

1. Using the Gs interface between MSS and SGSN.2. The mobile and the network support DTM feature.3. Activating BSS paging coordination via Pb internal

interface.

Paging Coordination

MO Parameter ID Meaning

GCELLPSBASE BSSPAGINGCOORDINATION

Whether to support the paging function of the CS domain of the A interface. Yes: the MS can be called upon paging request on the A interface when handling the PS service; No: the MS cannot be called upon paging request on the A interface when handling the PS service.


Timer: T3168

Packet Resource Request or Channel Request

Packet Uplink Assignment







T3168 Expire

T3168 Expire

T3168 Expire

T3168 ExpireTBF Establishment Failure due to radio reasons


Timer: T3192

DL RLC Data Block (FBI=1)

DL Packet Ack/Nack (FAI=1)

T3192 Expire

TBF Resources are released

DL RLC Data Block

DL RLC Data Block

DL RLC Data Block


• When the MS is switched from the packet transmission mode to the idle mode, the MS needs to maintain the none DRX mode for a moment. After the TBF is released, in the period when the MS is in non-DRX mode, the MS monitors all the CCCH blocks and the BSC stores the context of the MS.

• The reservation duration is determined by the minimum value of DRX_Timer_Max and NON_DRX_TIMER. The parameter NON_DRX_TIMER is negotiated with the SGSN during GPRS attaching of the MS. Normally, this value is greater than that of DRX_TIMER_MAX. Therefore, the value of DRX_TIMER_MAX is used.

0: switch to the DRX mode immediately; 1: switch to the DRX mode in one second. Value n indicates that the MS enters the DRX mode n

seconds

DRXTIMERMAX


DRXTIMERMAX

DL RLC Data Block (FBI=1)

DL Packet Ack/Nack (FAI=1)

T3192 ExpireTBF Resources are released

DL RLC Data Block

DL RLC Data Block

NON DRX Mode

DRX Mode

Stop listening to whole CCCH Channels


• This parameter is used to set the parameter BS_CV_MAX for MS countdown. This parameter is used for the MS to calculate the CV.

• This parameter also determines the duration of the timer T3198. When the MS sends one uplink RLC data block, the receiving state of this data block is set to Pending and the timer T3198 is started. If the MS receives the packet uplink acknowledge before the timer T3198 expires, the MS updates the receiving state of each uplink RLC data block according to the bit map in the message.

• If the timer T3198 of the RLC data block in the Pending state expires, the MS sets the receiving state of this data block to Nack and retransmits the data block.

BS_CV_MAX


BS_CV_MAX

BS_CV_MAC=15

BS_CV_MAC=6


T3198

ACK NACK ACK NACK Pending ACK ACK Pendi

ng ACK ACK

Will turn to NACK after

T3198 expire

Will be re transmitted

Will be removed from

window

UL RLC Window


When a nacked block is retransmitted, its status is changed from nacked to pending ack. Also when an transmitted block is transmitted, its status is changed to pending ack. If there are no blocks whose status is either nacked or un-transmitted within the RLC window, meaning that all the RLC blocks have been transmitted but no acknowledgement information has been received yet, the window is said to be stalled.

RLC Window Stalling

Pending NACK Pendi

ng NACK Pending NACK NACK Pendi

ng NACK NACK

Stalled RLC Window


• PAN_DEC: Set the decrease step length of the N3102 counter of the MS.

• PAN_INC: Set the increase step length of the N3102 counter of the MS.

• PAN_MAX: Set the maximum value of the N3102 counter of the MS.

PAN (Piggy-backed ACK/NACK)


PAN (Piggy-backed ACK/NACK)


GPRS/EGPRS Cell Reselection


Effect of RF Hopping


Effect of distance

gprs edge optimization

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