Adaptive Subcarrier Allocation Algorithms in Wireless OFDMA Systems

WiMAX is one of the most important technologies for providing a Broadband Wireless Access (BWA) in a metropolitan area. The use of OFDM transmission has been proposed to reduce the effect of multipath fading in wireless communications; moreover, multiple access is achieved by resorting to the use of OFDMA. Adaptive subcarrier allocation techniques have been selected to exploit the multiuser diversity, leading to an improvement of performances by assigning subchannels to the users accordingly with their channel responses. In this paper, three adaptive subcarrier allocation algorithms have been proposed; they are based on channel capacity and aim to assign an equal amount of capacity to all the users or to distribute the capacity proportionally to the users' channel conditions. The algorithms performances have been valued and compared in terms of bit error rate and throughput. The proposed strategies show a substantial improvement with respect to a static allocation, turning the multiuser diversity into a significant increase of data rate.