Performance of EGPRS incremental redundancy in interference-limited environments

Incremental redundancy (IR), an established hybrid-ARQ technique, has been proposed as an adaptive link level mechanism in third-generation and evolved second-generation wireless systems such as the Enhanced General Packet Radio Service (EGPRS). In this paper, three alternative EGPRS incremental redundancy ARQ algorithms of low (IR-ARQ1), medium (IR-ARQ2) and high (IR-ARQ3) computational complexity are specified The relative downlink performance of the specified algorithms is evaluated for interference-limited mobile radio environments with pedestrian (5 km/h) and vehicular (50 km/h) mobile speeds, using a high-speed link level simulator. For comparison, a basic selective-repeat ARQ algorithm (SRARQ) is also implemented The algorithms are compared in terms of their throughput performance, transmission delay performance, and processing requirements. It is shown that the most significant performance improvement is from SRARQ to IR-ARQ1 (up to about 2 dB at 5 km/h, and 5 dB at 50 km/h). The performance gains from IR-ARQ1 to IR-ARQ2, and from IR-ARQ2 to IR-ARQ3 are negligible. Overall, the results suggest that implementing a low-complexity incremental redundancy ARQ algorithm gives the optimal performance/complexity trade-off.