A novel adaptive receiver with enhanced channel tracking capabilityfor TDMA-based mobile radio communications

摘要

The paper presents a novel fast-adaptive nonlinear receiver whichnexploits soft statistics for tracking the random fluctuationsnexperienced by time division multiple access (TDMA) mobile radio linksnimpaired by frequency-selective time-variant multipath phenomena. Thendetection task is accomplished by an Abend-Fritchman-likensymbol-by-symbol maximum likelihood (SbS-ML) detector which deliversnboth hard decisions and soft statistics in form of a posteriorinprobabilities (APPs) of the states of the intersymbol interference (ISI)nchannel. In the proposed adaptive receiver, these APPs are employed innplace of the conventional hard-detected data to feed an ad hoc developednnonlinear recursive Kalman-type channel estimator. Extensive computernsimulations show that the exploitation of soft statistics enhances thentracking capability of the channel estimator so that the proposednreceiver generally outperforms the usual ones based on adaptive maximumnlikelihood sequence estimators (MLSEs) for signal-to-noise ratio (SNR)nvalues over 12-13 dB. Furthermore, the experienced performance gap withnrespect to more complex per-survivor processing (PSP)-basednmulti-estimator detectors appears generally small on slowly andnmoderately fast time-varying channels characterized by values of thenproduct Doppler bandwidth × signaling period BDTSn below 5×10-3