Performance Analysis of RLC/MPerformance Analysis of RLC/MAC Protocol in GeneralAC Protocol in GeneralPacket Radio ServicePacket Radio Service

K. Premkumar and A. ChockalingamK. Premkumar and A. ChockalingamWireless Research Lab (http://wrl.ece.iisc.ernet.in)Wireless Research Lab (http://wrl.ece.iisc.ernet.in)

Department of Electrical Communication EngineeringDepartment of Electrical Communication EngineeringIndian Institute of Science, Bangalore 560012, INDIAIndian Institute of Science, Bangalore 560012, INDIA

OutlinesOutlines

• Introduction• LLC/RLC/MAC in GPRS• Throughput-Delay analysis• Results and discussions

Introduction of GPRSIntroduction of GPRS

• A packet mode wireless system• Dynamically share radio resources with GSM• Uplink CHs are shared by request-reservation

GSM RF Libis

MS BSS SGSN GGSN

RLC

MAC

IP/X.25

SNDCP

LLC

Application

BSSGPRelay

Um Gb Gn

GSM RF

RLC

MACNetworkService

Libis

NetworkService

BSSGP

LLC

SNDCPRelay

GTPUDP/TCPIP

L2

L1

GTP

UDP/TCP

IP

L2

L1

IP/X.25

Gi

LLC/RLC/MAC in GPRSLLC/RLC/MAC in GPRS• Logical Link Control

– Operates between MS and SGSN– Variable size frames– “Stop-and-wait” Automatic Repeat reQuest

• Radio Link Control– Operates between MS and BSS– Fixed size blocks depending on CH coding– ACK mode provides selective retransmission

• Media Access Control– Slotted-ALOHA– Resolve collision of request packets

GPRS MAC protocolGPRS MAC protocol

• Packet Random Access Channel (PRACH)– Contention basis– Random backoff

• Packet Data Traffic Channel (PDTCH)– Dynamically assigned by b

ase station

• M uplink CHs, L PRACHs• N mobile users

Assumption before analysisAssumption before analysis

• New request packet generation is Bernoulli process with arrival prob λ

• A new PDU is accepted only after the completion of previous one

• PDU length, measured in #slots, is geometric with 0<gd< 1

• Loss of request is only due to collision• Retransmission attempts is geometrically delaye

d with 0 < gr <1• Propagation and processing delay are negligible

Mobile station state transitionMobile station state transition

,...}}3,2,1{);,,({ tkjiZ t

One step transition probabilityOne step transition probability

Throughput-Delay analysisThroughput-Delay analysis

Results and discussions (1/2)Results and discussions (1/2)

Results and discussions (2/2)Results and discussions (2/2)