Performance Analysis of RLC/MAC Protocol in General Packet Radio Service K. Premkumar and A. Chockalingam Wireless Research Lab ( Department of Electrical Communication Engineering Indian Institute of Science, Bangalore , INDIA

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

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

LLC/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 protocol Packet Random Access Channel (PRACH) –Contention basis –Random backoff Packet Data Traffic Channel (PDTCH) –Dynamically assigned by base station M uplink CHs, L PRACHs N mobile users

Assumption 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<g d < 1 Loss of request is only due to collision Retransmission attempts is geometrically delayed with 0 < g r <1 Propagation and processing delay are negligible

Mobile station state transition

One step transition probability

Throughput-Delay analysis

Results and discussions (1/2)

Results and discussions (2/2)