An adaptive data transmission scheme for OFDM systems

This paper proposes adaptive data transmission schemes for orthogonal frequency division multiplexing (OFDM) systems. The forward error correction (FEC) operation within the type I hybrid automatic repeat request (ARQ) protocol is performed on individual OFDM subchannels and the modulation scheme for each subchannel changes adaptively according to the error statistics of the received data blocks. An efficient method to coordinate different subchannels for retransmissions is explored. The system throughput efficiency is derived and compared for three schemes, i.e., a basic scheme (BS), a scheme with adaptive modulation (AMS) and a scheme with adaptive modulation and efficient subcarrier retransmissions (AMSCR). Numerical results show that significant performance improvements are achieved with AMSCR under a wide range of channel conditions.