An iterative receiver for coded OFDM systems over time-varying wireless channels

This paper presents a low-complexity iterative receiver for coded OFDM systems. We present an EM-based iterative algorithm for combined channel estimation and decoding that makes collective use of the available data and system constraints. Minimum numbers of pilots are sent only in the first symbol of the packet to acquire the channel; then the iterative algorithm is used to track the channel time variation, which is assumed to follow a state-space model, using an EM-based Kalman filter. Data recovery can be achieved within a single OFEM symbol. We also propose the use of an optional outer LDPC code in serial concatenation to offer a trade-off between latency and performance, especially for multi-amplitude modulations, without affecting the complexity of the core iterative algorithm.