Acknowledgment Operations in the RLC Layer of GPRS

This paper considers the acknowledgment procedure used to assure the delivery of packets on the radio interface of General Packet Radio Service (GPRS), where GPRS system is a new GSM service. It is currently being standardized for GSM Phase 2+ and provides packet switched data services over GSM network resources. This paper gives a rapid description of the GPRS radio interface, and its sublayers, 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 its performance is analyzed. The delay introduced by the acknowledgment procedure is evaluated analytically. In order to ameliorate the performance of the RLC acknowledgment mechanism, we propose and analyze a new additional hybrid FEC/ARQ mechanism, which can operate with the current one. The new mechanism permits to decrease the number of control blocks used for RLC acknowledgment and thus reduce the delay requested for a packet delivery.