Adaptive scheduling algorithms for multimedia traffic in wireless OFDMA systems

This paper deals with the problem of finding an optimal subcarrier allocation strategy for uplink and downlink communications in an OFDMA metropolitan wireless system. Three different resource allocation algorithms are proposed by taking into account the Quality of Service (QoS) constraints and the user’s channel conditions. Moreover, a simple strategy for choosing the most appropriate Modulation and Coding Scheme (MCS) according to the channel conditions of the assigned subcarriers is also considered. Finally, this paper studies the possibility of applying an adaptive Time Division Duplexing (TDD) separation of the uplink and downlink frame, based on the instantaneous load of the network. The performance of the proposed algorithms have been derived and compared in terms of error rate and throughput. All proposed methods show a significant improvement of the overall system performance in comparison with the static subcarrier allocation in which channel information has not taken into account. Moreover, additional improvements have been obtained by applying to these schemes the proposed adaptive TDD frame separation strategy.