Adaptive HARQ for Mobile WiMAX Systems over Time-Varying Channels

By retransmission and combining multiple copies of a packet, conventional hybrid ARQ (automatic-repeat-request) schemes are effective to increase the SNR (signal-to-noise ratio) of received signal but not capable of reducing ICI (inter-carrier interference). This paper proposes an adaptive HARQ scheme, which incorporates ICI cancellation into the conventional IR (incremental redundancy)-based HARQ and automatically activates the ICI cancellation without Doppler shift/mobility estimation. Simulations shows that the proposed algorithm outperforms the conventional one in time-varying channels, especially in high mobility environments because it retransmits signals with higher reliabilities.