An Adaptive Feedback Method with Channel Change Indication for Band AMC in a Femto Cell

The band adaptive modulation and coding (band AMC) scheme is used in orthogonal frequency division multiple access (OFDMA) systems to increase mobile communication system throughput, however, an amount of feedback overhead degrades uplink system performance. In this paper, we propose an adaptive feedback method that can significantly reduce the amount of channel feedback information when a femto base station (BS) and mobile stations (MS) communicate in the band AMC mode. Since the channel variation of the MS in the femto cell is relatively small, instead of informing the femto BS of the channel quality information (CQI) periodically, MSs only send CQI feedback to the femto BS when channel condition changes above a threshold. Simulation results show that the proposed scheme can reduce feedback overhead up to 70% without resulting in system throughput degradation compared to the conventional best-M feedback scheme.