Interference-Limited Environments
John A. Dunlop · 2002
Incremental Redundancy (IR), an established Hybrid-ARQ technique, has been proposed as an adaptive link level mechanism in third-generation and evolved secondgeneration wireless systems such as the Enhanced General Packet Radio Service (EGPRS). In this paper, three alternative EGPRS Incremental Redundancy ARQ algorithms of low (IR-ARQl), 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 M) 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-ARQI (up to about 2dB at 5 kdh, and 5 dB at 50 M). The performance gains from IR-ARQl to IRARQ2, and from IR-ARQ2 to IR-ARQ3 are negligible. Overall, the results suggest that implementing a lowcomplexity Incremental Redundancy ARQ algorithm gives the optimal performance/complexiry trade-ofi