Towards higher data rates for IS-136

IS-136+ aims to increase the data rate of IS-136 by using higher modulation formats such as 8-PSK or 16-QAM. It is necessary to adaptively switch between these formats to maintain optimal throughput as the SNR varies. Adaptive modulation is a non-trivial task in practice, because accurate SNR measurements are required, the interference may change more quickly than the feedback round trip, and the optimal switching points are a function of the mobile speed. As an alternative, we present an incremental redundancy ARQ retransmission scheme that not only significantly reduces the dependence on mode switching but also increases the average throughput by 20%.