AU-KBC RESEARCH CENTRE

In this paper we have presented a new loading algorithm for a multiuser Orthogonal Frequency Division Multiplexing (OFDM) based multiple access system for indoor wireless communications in the downlink and analyzed its performance. The optimization problem for minimizing the total transmit power from a base station while satisfying the bit-rate (BR) and bit-error rate (BER) criterion of the various portable users in the system has been outlined. The optimal solution cannot be realized in a simple manner and we present an easily realizable algorithm for allocating subcarriers, modulation mode, and power to the signals transmitted to the different users. Simulation results are used to compare the performance of the optimal method with that using the new algorithm under various channel conditions. The correlation of the frequency-domain channel strengths among the various users is shown to have a significant influence in the performance of the new algorithm. A performance comparison between the new algorithm and systems employing standard multiple access strategies clearly indicates the advantages of the new algorithm under most conditions.