Using time advance information to choose coding scheme in GPRS

Abstract

GPRS defines four coding schemes named from CS-1 to CS-4 with different degrees of data protection against transmission errors in the air interface. The former coding scheme is already used in GSM and the others sequentially offer higher throughput rates but less protection. The selection of the best suited coding scheme could be based on link quality estimators but also on more deterministic system parameters such as time advance (TA) information. This paper analyses this latter option and provides results in order to quantify the feasibility of such allocation based on the time advance information. Aspects such as TA resolution, cell coverage, power control policies and system load are taken into consideration.