Subcarrier allocation and power control for OFDMA

We study the problem of finding an optimal subcarrier and power allocation strategy for downlink communication to multiple users in an OFDM based wireless system. We formulate the problem of minimizing total power consumption with constraints on BER and transmission rate for users requiring different classes of service, and derive simple algorithms which perform well. We divide the larger problem of joint allocation into two steps. In the first step, the number of subcarriers that each user is determined based on the users´ average SNR. Numerical results demonstrate that the proposed low complexity algorithms offer comparable performance with an existing iterative algorithm.