Frequency-domain cross-layer diversity techniques: an efficient way of coping with lost packets in broadband wireless systems

Modern broadband wireless systems demand increasing quality of service (QoS), requiring small error rates and delays which effectively ensure increased throughput. This article focuses on the handling of lost packets and its influence on spectral efficiency. Two time diversity approaches are considered and compared to cope with lost packets: a low-complexity diversity combining Automatic Repeat reQuest (ARQ) scheme employed in a Time Division Multiple Access (TDMA) architecture; and a Network Diversity Multiple Access (NDMA), which is a multi-packet detection approach able to separate simultaneous transmissions using temporal diversity. The comparison among the approaches focuses on error rate, throughput and delay performances, and takes the implementation complexity in consideration.