Abstract: A novel Hybrid ARQ scheme for orthogonal frequency division multiplexing (OFDM)systems is proposed. The scheme exploits the property of high level modulation that the performance of different bits mapped to the same modulation symbol is different, and the property of the multi-path channel that the fading between anypair of OFDM subcarriers is independent, provided that the frequency interval is wider than channel's coherent bandwidth. In the retransmission of one data packet, the bit level interleaving mode is changed,so that the transmission orderis changed, and the packet is maximum ratio combined at the bit level.

Key words: mobile communication, orthogonal frequency division multiplexing, hybrid ARQ