Acknowledgment procedures at radio link control level in GPRS

In this paper, we investigate the acknowledgment procedures used at radio link control level in General Packet Radio Service (GPRS). The GPRS is a new GSM service, which is currently being standardized by ETSI for GSM Phase 2+ and it provides packet switched data services over GSM network resources. The role of acknowledgment procedures is to assure the delivery of packets on GPRS radio interface. This paper gives a brief description of GPRS radio interface with a special attention to the Radio Link Control and Medium Access Control (RLC/MAC) layer procedures. Particularly, the acknowledgment parameters and operations are described and their performance is evaluated. The delay introduced by acknowledgment procedures is studied analytically In order to ameliorate the performance of RLC acknowledgment mechanism, we propose and describe a new additional hybrid FEC/ARQ mechanism, which can operate with the current one. The purpose of new mechanism is to decrease the number of control blocks used for RLC acknowledgment mechanism and thus reduces the delay requested for a packet delivery. After presenting the channel models used, we evaluate by simulation the performance of acknowledgment procedures presented in ETSI specifications and the proposed one over a stationary channel model and over a noisy wireless channel model affected by burst of errors.