Extended MLSE diversity receiver for the time- and frequency-selective channel

This paper develops an MLSE diversity receiver for the time- and frequency-selective channel corrupted by additive Gaussian noise, when linear constellations are employed. The paper extends Ungerboeck´s derivation of the extended MLSE receiver for the purely frequency-selective channel to the more general channel with diversity. The new receiver structure and metric assume a known channel. The major contributions of this paper are as follows: (i) the derivation of a finite-complexity diversity receiver that is maximum likelihood (ML) for all linear channel models and sources of diversity; (ii) a benchmark, in that the new receiver´s performance is a lower bound on the performance of practical systems; (iii) insight into matched filtering and ML diversity receiver processing for the time- and frequency-selective channel; (iv) bounds on the new receiver´s BER for ideal channel state information (CSI), in a fast Rayleigh fading channel with multiple independently faded paths