Power and Subcarrier Allocation Algorithms for OFDMA Systems

The problem of low complexity sub-optimal power and subcarrier allocation for orthogonal frequency division multiple access (OFDMA) systems is addressed in the paper. First we extend the ordered subcarrier selection algorithm recently proposed for a single user case to the OFDMA systems. Our analysis confirms an efficiency of such an extension. Then we suggest to supplement the scheme with a low complexity power loading algorithm that equalizes the subcarriers´ signal-to-noise ratios for each user. This procedure further improves the system performance in terms of power consumption. Both the theoretical analysis and simulation results confirm efficiencies of the suggested schemes. The proposed techniques are simple in implementation and they are not iterative that is especially attractive for mobile applications. For implementation of the latter method, the channel state information in terms of the subcarriers´ power gains should be available at the transmitter. Thus the proposed sub-optimal method is especially convenient to apply in communication systems where this information can be easily provided, such as WiMAX technology