Improved HARQ scheme using channel quality feedback for OFDM systems

An improved Chase combining scheme is proposed to take advantage of the channel quality feedback information, which is mandatory for adaptive modulation and coding (AMC) schemes, to enhance the throughput of OFDM based mobile communication systems. By comparing the signal-to-noise ratio (SNR) measured on sub-carriers with a predetermined threshold, the data to be retransmitted are selected and mapped onto the sub-carriers that have better channel quality to achieve higher diversity gain in the next retransmission. Simulation results prove that such an operation can reduce the amount of retransmitted data and the resource usage in retransmission, which leads to higher throughput efficiency than conventional Chase combining schemes.