Adaptive Bit Loading and Transmit Diversity for Iterative OFDM Receivers

In this paper, we consider a transmission system employing orthogonal frequency division multiplexing (OFDM) with bit-interleaved coded modulation and perfect channel state information at both transmitter and receiver. An adaptive bit loading scheme in combination with cyclic delay diversity and discontinuous Doppler diversity is proposed at the transmitter and iterative demapping and decoding at the receiver. The loading procedure minimizes the bit-error rate at the decoder output, and the transmit diversity schemes mitigate channel correlations. We analyze the iterative receiver with extrinsic information transfer charts and present the achievable gains.