GPRS overview

© NOKIA India_1.PPT / 1.6.05 / Matti Puhto

GPRS PERFORMANCE MANAGEMENT WORKSHOP GPRS PERFORMANCE MANAGEMENT WORKSHOP

GPRS FUNDAMENTALSGPRS FUNDAMENTALS

Matti PuhtoMatti PuhtoPrincipal EngineerPrincipal Engineer

Delhi 1.6.05Delhi 1.6.05


Next 3 days agendaNext 3 days agenda• 1.6.05 full day

GPRS Fundamentals & MPC activity in India

• 2.6.05 14:30-18:00GPRS signaling GPRS KPI’sOptimisation

• 3.6.05 full dayGPRS Practical cases


AGENDA AGENDA What is old/new in GPRS

System overview, What has changed? What remains as per today? Signaling multiframe mapping

The concept, What's the affect today ? The Future: PBCCH Data multiframe mapping

The concept, How PCU works ? The Future: QoS CS1 & CS2

how this will affect the throughput ? link adaptation algorithm, Future: EDGE GPRS Territory Method

how Nokia specific Territory Method works ? Mobility Management stages

The concept, How this will this affect the signaling ?, DRX stage, Timers changes between S9 and S10

PBCCH, GPRS dedicated n-list


The NetworkThe Network

MSC

LocalAreaNetwork

Server

Router

Corporate 1

Server

Router

Corporate 2

GPRSINFRASTRUCTURE

BorderGateway (BG)

Serving GPRSSupport Node(SGSN)

HLR/AuCEIR

BSCBTSUm

Gateway GPRSSupport Node(GGSN)

Lawful InterceptionGateway (LIG)

Inter-PLMNnetwork

Datanetwork(Internet)


PSTNNetwork

SS7Network

GPRSbackbonenetwork

(IP based)

Billing System

Charging Gateway (CG)


GPRSGPRS

LocalAreaNetwork

Server

Router

Corporate 1

Server

Router

Corporate 2

GPRSINFRASTRUCTURE

BorderGateway (BG)

Serving GPRS Support Node

HLR/AuCEIR

Um

Gateway GPRSSupport Node

Lawful InterceptionGateway (LIG)

Inter-PLMNnetwork



PSTNNetwork

SS7Network

GPRSbackbonenetwork

(IP based)

Billing System


1..16+1 PAPU

PCU each for 256TCH in max 64cells, 128TRXsmax. 16 PCU (4096TCH) Max 2Mbit/s

Bearer:(1..31) x 64kbit/s

SGSN,counters

Per PAPU:1 RAmax. 64 x 64kbit/s (frame relay)max.15k PDP contexts

1..4+1SMMU

24 x 64kbit/s per SMMU

BSC

BTS

MSC

GGSN


Gb

Per user:max. 2 PDP(rel.1)max. 4 PDP (rel.2)

Frame Relay: max.4 bearer ch. per PCU

1MS/TBFmax.9MS/DL TSLmax.7MS/UL TSL(In S10 nbr of MS/TSLwill be different)

S9: 1 PCU: 256 TCH in 64 BTS S10: 1 PCU: 256 TCH in 64 segments

Max.248BTS

DAP: max.470max20TRX/DAP

Gn

GGN2: 100000 PDP contexts250 Aps100Mbps nominal, 240Mbps max


The ProtocolsThe Protocols

L1L2IP

UDPGTP

USERPAYLOAD

GGSN

L1L2

IP

GPRS Bearer

GGSN

Relay

IP

GPRS IP Backbone

L1L2IP

GTP

L1bisNW sr

BSSGP

SNDCPLLC UDP

SGSN

Relay

Gn

Internet

L1L2IP

TCP/UDPAPP

Gi

•User information transfer

LLCSNDCP

IPTCP/UDP

APP

RLCMAC

GSM RF

MS

RLCMAC

GSM RF

BSSGPNW srL1bis

BSS

Ciphering and reliable link

Um Gb

Compression, segmentation

FIXED HOST


GPRS versus GSM GPRS versus GSM Fundamental DifferencesFundamental Differences

• 3+1 versus 1+1GPRS MS can use up to 3 TS in DL, in CSW this is 'not' possible

• Up to 9 users may share the same time slot in DLseparation based on MAC header, affect to data speed,

unrealistic

• GPRS do not have handoversbecause MS is not sending measurement reports to network

• GPRS 'do not' have power controlbecause MS is not sending measurement reports to network, PC

only in UL

• Radio resources are allocated to a user on level of 5 seconds (DL TBF) this depends heavily on applicationsgenerates massive signaling, ref. Mobility management stages


GSM and GPRS MultiframeGSM and GPRS Multiframe

D O C U M E N T T Y P E

T y p e U n i t O r D e p a r t m e n t H e r eT y p e Y o u r N a m e H e r e T y p e D a t e H e r e

G S M S i g n a l l i n g t i m e s l o t G S M T r a f f i c T S G P R S t r a f f i c T ST D M A f r a m e

T S 0 T S 1 T S 2 T S 3 T S 4 T S 5 T S 6 T S 70 F C C H T C H1 S C H T C H2 B C C H T C H R a d i o B l o c k 03 B C C H T C H4 B C C H T C H5 B C C H T C H6 P C H + A G C H T C H R a d i o b l o c k 17 P C H + A G C H T C H8 P C H + A G C H T C H9 P C H + A G C H T C H

1 0 F C C H T C H R a d i o B l o c k 21 1 S C H T C H1 2 P C H + A G C H S A C C H P T C C H1 3 P C H + A G C H T C H1 4 P C H + A G C H T C H1 5 P C H + A G C H T C H R a d i o B l o c k 31 6 P C H + A G C H T C H1 7 P C H + A G C H T C H1 8 P C H + A G C H T C H1 9 P C H + A G C H T C H R a d i o B l o c k 42 0 F C C H T C H2 1 S C H T C H2 2 P C H + A G C H T C H2 3 P C H + A G C H T C H R a d i o B l o c k 52 4 P C H + A G C H T C H2 5 P C H + A G C H I D L E I D L E2 6 P C H + A G C H2 7 P C H + A G C H2 8 P C H + A G C H R a d i o B l o c k 62 9 P C H + A G C H3 0 F C C H3 1 S C H3 2 P C H + A G C H R a d i o B l o c k 73 3 P C H + A G C H3 4 P C H + A G C H3 5 P C H + A G C H3 6 P C H + A G C H R a d i o B l o c k 83 7 P C H + A G C H3 8 P C H + A G C H P T C C H3 9 P C H + A G C H4 0 F C C H4 1 S C H R a d i o B l o c k 94 2 P C H + A G C H4 3 P C H + A G C H4 4 P C H + A G C H4 5 P C H + A G C H R a d i o B l o c k 1 04 6 P C H + A G C H4 7 P C H + A G C H4 8 P C H + A G C H4 9 P C H + A G C H R a d i o B l o c k 1 15 0 I D L E5 1 I D L E


GPRS System understanding: signaling GPRS System understanding: signaling multiframe structure (51 TDMA frames)multiframe structure (51 TDMA frames)

RR R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R

F S B C F S CC F S CC F S CC F S CC -

R R R RR

D 0D 0

D 1D 1

D 2D 2

D 3D 3

D 4D 4

D 5D 5

D 6D 6

D 7D 7

A 0A 4

D 0D 0

D 1D 1

D 2D 2

D 3D 3

D 4D 4

D 5D 5

D 6D 6

D 7D 7

A 0A 4

A 3A 1A 5

A 2A 6 A 7 --

- - --

--- - -

-A 3A 1A 5

A 2A 6 A 7

F S B C F S CC F S -F S B C F S CC F S -

R R R R R

R R R R R R R R R R R R R R RR R R RR R R RR R R R R R R R R R R R R R RR R R RR R R R

D 3D 3

RRRR

D 0D 0

D 1D 1

R RR R

D 2D 2

A 0 A 1A 3A 2

F SF S D 3D 2

D 3D 2F SF S

D 1D 0D 1D 0

A 2 A 3A 1A 0

S:C:A:

F:B:D:R:

TD M A fram e fo r frequency correction burstTD M A fram e fo r BC C HTD M A fram e fo r SD C C HTD M A fram e fo r R A C H

B C C H + C C C H(do w n link)

B C C H + C C C H(up link)

8 S D C C H /8(up link)

8 S DC C H /8(d ow nlin k)

B C C H + C C C H4 S D C C H /4(do w n link)

B C C H + C C C H4 S D C C H /4

(up link)

TD M A fra m e for synch ro n iza tion bu rs tTD M A fra m e fo r C C C HTD M A fra m e fo r S A C C H /C

51 fram es 235 .38 m s


GPRS system understanding: RLC follows GPRS system understanding: RLC follows 26 TDMA multiframe26 TDMA multiframe

• Explain RLC mapping to TDMA multiframe


Role of NMORole of NMO

• Network Mode of Operation 1 (NMO1) means that Gs interface exists (VLRSGSN)

• Possibility to made combined procedures (attach, LU/RAU…)

• Is a must when PBCCH is implemented

• Recommendation is to use NMO1

• In case of NMO2 Gs is not implemented

• Paging in case of NMO1:

• SGSN is just delivery man (pages and possible re-pages are coming from VLR)

• Counters in Nokia BSC: c3000 (via A-if), c3057 (via Gb, PS), c3058 (via Gb, CS)


Link adaptation and Link adaptation and GPRS Coding SchemesGPRS Coding Schemes

Coding Scheme

Payload (bits)per RLC block

Data Rate (kbit/s)

CS1 181 9.05

CS2 268 13.4

CS3 312 15.6

CS4 428 21.4

More Data =

Less Error Correction

Nokia GPRSRelease 1

• CS1 & CS2

- Implemented in ALL Nokia BTS without HW change

Dat

a

Err

orC

orre

ctio

n


Radio interface summary for EDGERadio interface summary for EDGE• In EDGE we have new modulation: 8-PSK• In GSM, including GPRS, we are using GMSK modulation• This modulation change allowes higher data rates in air interface• Due to higher speed in air interface, modifications needed in A-bis interface (dynamic

A-bis pool, ADAP pool)

• New re-sending algorithm: Incremental Redundancy (IR)• PCU orders BTS to send relevant RLC block indifferent MCS than the original RLC

block

• Link adaptation: same idea than in GPRS, more steps (2 versus 9)


New modulation: 8-PSK (EDGE)New modulation: 8-PSK (EDGE)

EDGE GSMModulation 8-PSK, 3bit/sym GMSK, 1 bit/symSymbol rate 270.833 ksps 270.833 kspsPayload/burst 346 bits 114 bitsGross rate/time slot 69.2 kbps 22.8 kbps

(0,0,1)

(1,0,1)

(d(3k),d(3k+1),d(3k+2))=(0,0,0) (0,1,0)

(0,1,1)

(1,1,1)

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

• 8-PSK (Phase Shift Keying) has been selected as the new modulation added in EDGE

• Non-constant envelope high requirements for linearity of the power amplifier

• Because of amplifier non-linearities, a 2-4 dB power decrease (back-off) is typically needed

• 3 bits per symbol

• 22.5° offset to avoid origin crossing

• Symbol rate and burst length identical to those of GMSK


GMSK (GPRS) & 8-PSK (EDGE) GMSK (GPRS) & 8-PSK (EDGE) modulationsmodulations

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


22,5° offset to avoid zero crossing


8-PSK Tx Power Reduction8-PSK Tx Power Reduction

GMSK

8PSK

Time


Time


Pin

Pout

Back Off= 4 dB

Compression point


8-PSK Modulation8-PSK Modulation• Since the amplitude is changing in 8-PSK the transmitter non linearity can be seen in

the transmitted signal• These non-linearity 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 to the signal must remain in the linear part of the power amplifier


GPRS & EGPRS coding schemesGPRS & EGPRS coding schemes• GPRS has four coding schemes,

CS-1...4. All use GMSK.• EDGE has nine modulation and coding schemes,

MCS-1...9.• MCS-1...4 use GMSK,

MCS-5...9 use 8-PSK modulation• Operator can set the MCS to start with

• E.g. always start with MCS-9

MCS-7

MCS-1

22

MCS-2

28

MCS-3

37

MCS-4

44

MCS-5

56

MCS-6

74

5656

MCS-8

6868

MCS-9

74 74

redundancy fromchannel coding

RLC data block,number of octets

RLC/MAC block(radio block)

CS-1

20

CS-2

30

CS-3

36

CS-4

50


EDGE link performanceEDGE link performance• GPRS with re-transmission with same

coding scheme• Retransmissions with EDGE can be sent

with the new scheme•Bit Error Probability (BEP) is a new MS quality measurement introduced

• In general, a higher coding scheme has higher coding rate, and consequently higher peak throughput, but it also tolerates less noise or interference.

• New parameters• Max BLER for Ack and Non-Ack modes

Can be used to tune to use more higher MCS’s• Mean BEP offset for GMSK and 8-PSK

Set threshold for MCS change

• The figure shows throughput vs. C/I of EGPRS coding schemes in TU50iFH, without incremental redundancy.

0

10

20

30

40

50

60

0 5 10 15 20 25 30

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

Ideal Link AdaptationIn RLC layer (kbit/TSL)

C/I


Coding scheme Data rate for 1 TSL

MCS-1 8.8 kbit/s MCS-2 11.2 kbit/sMCS-3 14.8 kbit/sMCS-4 17.6 kbit/sMCS-5 22.4 kbit/sMCS-6 29.6 kbit/sMCS-7 44.8 kbit/sMCS-8 54.4 kbit/sMCS-9 59.2 kbit/s

Number of Abis TSL’sThis is also requirement for GSM FR voice2x

2x2x2x3x4x5x5x

EGPRS Modulation and Coding SchemesEGPRS Modulation and Coding Schemes


Nokia Dynamic AbisNokia Dynamic Abis• The Dynamic Abis feature optimizes the loading:

• Permanent time slots for signaling/voice and a dynamic pool for data

• Pool can be shared by a number of transceivers• Dynamic Abis reduces the need for new transmission

capacity up to 67%.

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



TCH 2TCH 1TCH 0TCH 7TCH 6TCH 5TCH 4



MCB LCB

TRXsig1TRXsig2TRXsig3TRXsig4TRXsig5TRXsig6BCFsig

EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1EDAP1

Q1-management

TRX 1

TRX 2

TRX 3

TRX 4

TRX 5

TRX 6TRXsigs+BCFsig

EGPRSpool

TCH 3

28272625242322212019181716151413121110987654321

293031

0

BTS

BTS

BSC

Mobile with 59.2 kbit/s (MCS-9) connection in TRX6, 1 fixed and 4 dynamic Abis TSL.


Incremental Redundancy (IR) in BriefIncremental Redundancy (IR) in Brief• GPRS "send and pray"

• EGPRS "send and minimize re-sending"Interference > corruption of data Store blockTransmission of GPSR data block

Higher reception probability leads to higher user data rates

Puncturingscheme 1

Puncturingscheme 2

Interference > corruption of data

Soft combiningRe-transmission Interference > corruption of data Block accepted

Interference > corruption of data Block not acceptedTransmission of GPSR data block

Re-transmission Block not accepted

Re-transmission Interference > corruption of data Block not accepted


Territory concept and channel allocationTerritory concept and channel allocation• Main rule is the same idea: one user per time slot in air interface (=1.0 TBF/TSL)• If PCU is forced to allocate several user per Time Slot (in air interface); GPRS TBFs

to same TSL, EDGE TBFs to another TSL (penalty method)• Worst scenario: EDGE TBF in DL and GPRS in UL (very theoretical)• Specification: MS have to have frame synchronization with in 360ms interval every

18th RLC block must be sent in GMSK modulation


GPRS: GPRS: territory territory (S9-10)(S9-10)

AVG. AVAILABLE TCH in CS territoryava_15 (S9)ave_avail_TCH_sum/ ave_avail_TCH_den

AVG. AVAILABLE GPRS CHANNELS in PS territoryava_16 (S9)ave_GPRS_channels_sum/ave_GPRS_channels_den

AVG. AVAILABLE DEDICATED GPRS CHANNELSava_17 (S9) ave_GPRS_channels_sum/ave_GPRS_channels_den

PEAK DEDICATED GPRS CHANNELS/c2066(S9)peak_permanent_gprs_ch

PEAK GPRS CHANNELS/c2063(S9) peak_gprs_channels

Used capacity for GPRS

The following are the operator configurable parameters for territorymanagement: GPRSenabled (BTS-level) GPRSenabledTRX (TRX-level) DedicatedGPRScapacity (BTS-level) DefaultGPRScapacity (BTS-level) PreferBCCHfreqGPRS (BTS-level) TerritoryUpdateGuardTimeGPRS (BSC-level)

GENA

GTRXCDED

CDEFBFG

GTUGT

ADDIT.GPRS CH USEDach_1

UNAVAILABLE TCHc2040

AVG. BUSY TCH = CS traffictrf_12bave_busy_tch/ res_av_denom14

AVG. TSL used for UL GPRS trf_78b

AVG. TSL used for DL GPRS trf_79b

Free capacity

Allocated resources

Usedresources

CDEDCDEF

Used capacity for speech

Availability ava_1d

The main principle is that GPRS (PS) uses the capacity that remains from the CS traffic.

Given as % over dual TCH tsls ofGPRS enabled TRXs. Includes dedicated time slots. Rounded downwards.

• Circuit Switched traffic has priority• In each cell Circuit Switched & Packet Switched territories are defined• Territories consist of consecutive timeslots

TRX 1

TRX 2

CCCH TS TS TS TS TS TS TS

TS TS TS TS TS TS TSTS

DedicatedGPRS

Capacity

CircuitSwitchedTerritory

PacketSwitchedTerritory

Territory border movesDy n a m ic a l ly based onCircuit Switched traffic load

DefaultGPRS

Capacity

AdditionalGPRS

Capacity

http://nea.ntc.nokia.com/~neva/PMWG_2GBSS/GPRS_territory.htm

http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/frmls?ava_15



http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/counters?002066


http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/params?942






http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/frmls?ach_1


http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/frmls?trf_12b




http://essrv509ntc.ntc.nokia.com:6336/dynaweb/NED31_bsc_s9e/0031312/@ebt-link;nh=1;pt=46768;uf=0?root=%25N%15_46776_START_RESTART_N%25;stylesheet=table.rev;window=new;title=%22Table+124%3A+%22;__prev_hit__=46773;DwebQuery=CDEF

http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/frmls?ava_1d


GPRS: Territory upgrades/downgrades (S9-10) GPRS: Territory upgrades/downgrades (S9-10)

In S9 the margin (free tsls for CS) between CS and PS territory is defined by system and is dependent on nbr of TRXs.In S10 margin can be set as BSC level parameter ‘CSU’ (actual tsls for margin counted on BTS level by BSC) ¨

GPRS territory guard time is BSC level parameter to define how frequently upgrades can be made.

S9 marginNo. of TRXs 1 2-3 4 5-7 8-9 10-12 13-16 margin (tsls) 1 2 3 4 5 6 7

gprs_ter_upgr_req/c1174 (S9)

incompl_serv_gprs_ter_upgr_req/c1175 (S9)

gprs_ter_ug_rej_due_csw_tr/c1176 (S9)

Rejected

gprs_ter_ug_rej_due_lack_psw/c1177 (S9)

gprs_ter_ug_rej_due_lack_pcu/c1178 (S9)

Incompletely served

Requests from PCUfor additional channel(more than one channel can be requested) gprs_ter_downgrader_req

/c1181 (S9)

gprs_ter_dg_due_inc_in_csw_tr/c1179 (S9)

gprs_ter_ug_due_dec_csw_tr/c1180 (S9)

Territory UpgradeTerritory Downgrade

Due to decreased CS traffic

Requests from PCU

Ave_add_gprs_ch_hold_den/c2068 (S9)

Upgrade of additional ch.

Downgrade of additional tsl when notneeded anymore

Requests from MCMU

Additional ch. seizures (req. from PCU)

Requests from MCMU

CS traffic high (CS margin kept)

All GPRS TRXs already in GPRS territory

Max.256 TCH per PCU

DG request rejection (S11.5?)

Note: not triggered if the CS is already occupying the GPRS territory .

Note: the upgrade can be requested again after the guard time is over.

See also: TN772PSW RRM decides to request for more channels in the following cases: 1) When there is a lack of resources as indicated by the status flag (MS mslot capability needs more tsls than available) 2) When the average TBF number in a channel has increased (checked after every channel allocation) to more than UpgradeTrigTBFno (a configurable PRFILE parameter).The number of channels required is calculated so that if the requested number of channels were given to PSW, the average number of TBFs in a channel would be at most UpgradeTargetTBFno (a configurable parameter). At least one channel will be requested.

Note: upgrades are not tried if CS has taken PS territory => from upgrad rejections we can not see this situation

http://nea.ntc.nokia.com/cgi-bin/counter_list_bsc.pl?counter_id=001174













GPRS and EDGE mixGPRS and EDGE mix• Unwanted situation: if EDGE and GPRS user will start to share the same radio

resources (2 (or more) TBF per a TSL)• Network have to inform USF for UL TBF• Worst case: DL TBF with EDGE and UL TBF for GPRS in the same time slot• In this case EDGE user can have only GMSK modulation due to USF (up to MCS-4)• Due to frame synchronization network must send a RLC block which is understood

by all MS in given TSL (CS-1) ref: 05.08, 10.2.2 • Above should be taken into consideration while doing EDGE planning• Some considerations: use 2 different territory, use max 1.0 TBF/TSL, typical TBF life

time is 5 sec in DL and some 0.5 sec in UL


Multiple Mobiles and Downlink TransmissionMultiple Mobiles and Downlink Transmission

TFI2

TFI5

TFI3

TFI2

MSs

BTS

The TFI included in the Downlink RLC Block header indicates which Mobile will open the RLC Block

associated with its TBF

RLC Data Block


Downlink RLC data block with MAC headerDownlink RLC data block with MAC header

USF - Uplink State FlagTFI - Temporary Flow Indicator (TBF ID)FBI - Final Block IndicatorBSN - Block Sequence Number (RLC Block ID within TBF)

Bit8 7 6 5 4 3 2 1

Payload Type RRBP S/P USF MAC headerPR TFI FBI Octet 1

BSN E Octet 2Length indicator M E Octet 3 (optional)

.

.

.

.

.

.Length indicator M E Octet M (optional)

Octet M+1

RLC data.

.

.Octet N2-1Octet N2

spare spare (if present)


Multiple Mobiles and Uplink TransmissionMultiple Mobiles and Uplink Transmission

USF = 1

USF = 2

USF = 3

USF = 3

MSs

BTS

RLC Data Block

The USF included in the Downlink RLC Block header identifies which Mobile will transmit in the following

Uplink RLC Block


Bit8 7 6 5 4 3 2 1

Payload Type Countdown Value SI R MAC headerspare PI TFI TI Octet 1

BSN E Octet 2Length indicator M E Octet 3 (optional)

.

.

.

.

.

.Length indicator M E Octet M (optional)

Octet M+1 \TLLI Octet M+2 } (optional)

Octet M+3 /Octet M+4 /

PFI E Octet M + 5 /Octet M+6

RLC data...Octet N-1Octet N

spare spare (if present)

Uplink RLC data block with MAC headerUplink RLC data block with MAC header

Countdown Value - Used to calculate number of RLC blocks remaining(SGSN Function)

TLLI - Temporary Logical Link Identifier (type of mobile ID)


GPRS System understanding: Mobility GPRS System understanding: Mobility ManagementManagement

D O C U M E N T T Y P E

T y p e U n i t O r D e p a r t m e n t H e r eT y p e Y o u r N a m e H e r e T y p e D a t e H e r e

I d l e

S t a n d b y

R e a d y

P a c k e tT X / R XM O B I L E R E A C H A B L E

T i m e r E x p i r y

G P R SA t t a c h / D e t a c h

R E A D YT i m e r E x p i r y

M S l o c a t i o n k n o w n t oR o u t i n g A r e a l e v e l .M S i s c a p a b l e o f r e c i e v i n gP o i n t - t o - M u l t i p o i n t d a t aa n d b e i n g p a g e d f o rP o i n t - t o - P o i n t d a t a

M S l o c a t i o nn o t k n o w n .S u b s c r i b e r i s n o tr e a c h a b l e b y t h eG P R S N W .

M S l o c a t i o n k n o w n t oc e l l l e v e l .M S i s t r a n s m i t t i n g o r h a sj u s t b e e n t r a n s m i t t i n g .M S i s c a p a b l e o f r e c e i v i n gP o i n t - t o - P o i n t d a t a a n dP o i n t - t o - M u l t i p o i n t d a t a .

• GPRS MM is based on States• State Transition occurs when a pre-

defined transaction takes place• For example, via GPRS Attach the

MS makes itself known to the network:

• State transition Idle to Ready• Mobility Management before

Session Management:• GPRS attach needs to happen

before PDP context activation• READY Timer default value: 44 s• MOBILE REACHABLE Timer

default value: 60 min• Timer values are configurable with

SGSN Parameter Handling


PBCCHPBCCH

• PBCCH is the mediceine against cell reselection

• In S10: PBCCH can contain own packet neighbor list

• GPRS MS acts like idle CS MS now GPRS "must" be activated in all cells with PBCCH (S10) C31 and C32 makes possible manipulate GPRS terminals

• In S10 dedicated GPRS signaling (fully separated)

• DL PCCCH (RLC mapping) = PBCCH (n-list, 12-2), PAGCH (12-2-on demand), PPCH (12-2-on demand), "free" are used for PDCH and PACCH

• UL PCCCH (RLC mapping) = PRACH (12-6), "free" are used for PDCH and PACCH

• above are master PCCCH, possibility to use additional PCCCH(no PBCCH)

GPRS overview

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