Performance comparison of link adaptation and incremental redundancy in wireless data networks

Link adaptation and incremental redundancy are two link level techniques proposed to enhance data rate and increase throughput in wireless data networks. Link adaptation pro-actively adjusts the modulation and coding scheme based upon estimated channel conditions. Incremental redundancy, on the other hand, adjusts the code rate to actual channel conditions by incrementally transmitting redundancy information until decoding is successful. In this study, we investigate the system performance of these two techniques. Our results show that incremental redundancy achieves significantly higher throughput compared to link adaptation, especially under high traffic loading conditions. This gain is achieved at the expense of higher terminal and base station complexities, as well as a higher packet delay. On the other hand, in contrast to link adaptation, incremental redundancy does not require any channel quality measurements, and can operate based solely upon ACKs and NACKs