Extended MLSE Receiver for the Frequency-Flat, Fast Fading Channel

This paper develops an MLSE receiver for the frequency-flat, fast fading channel corrupted by additive Gaussian noise, when linear modulations (M-ASK, M-PSK, M-QAM) are employed. The paper extends Ungerboeck’s derivation of the Extended MLSE receiver for the purely frequency-selective channel to the time-selective channel. Although the new receiver’s structure and metric assume ideal channel state information (CSI) at the receiver, the receiver structure can be used wherever high-quality CSI is available. The receiver is Maximum Likelihood for a variety of channels, including Ricean, Rayleigh, log-normal and AWGN channels. Bounds on the receiver’s BER are deduced for ideal and pilot tone CSI for fast Rayleigh fading. A crude lower bound is developed on the BER of predictor-based receivers for the same channel. The paper offers insight into matched filtering and receiver processing for the fast fading channel, and shows how pilot symbols and tones should be exploited.