Adaptive Resource Allocation for OFDMA with Mixed Frame Structure

This paper introduces a reconfigurable mixed frame structure and a resource allocation algorithm for OFDMA systems supporting both the band-AMC and diversity modes in the frame. To reduce the total feedback without significant performance loss, we assign a user to the diversity subchannel when the band-AMC mode has no gain over the diversity mode based on the frequency selectivity of the user. After user selection, we apply joint power and rate allocation to exploit the asymmetry in required transmit power of the band-AMC mode and the diversity mode. The results reveal that the mixed frame with simple user classification provides a performance comparable to the frame with band-AMC mode only at a much reduced feedback. In particular, it is observed that the mixed frame with frequency division is preferable to that with time division by increasing the throughput of the users at the cell boundary in a large cell.