ADAPTIVE EQUALIZATION AND DIVERSITY COMBINING FOR MOBILE RADIO USING INTERPOLATED CHANNEL ESTIMATES

Digital cellular radio (DCR) communications occur over a fading multipath channel. In the case of low bit-rate, narrow-band communications, some form of adaptive equalization and diversity combining is required to mitigate the intersymbol interference and rapid time variations in the DCR channel. In this paper, we demonstrate the feasibility of a DCR system which employs a jointly adaptive decision-feedback equalizer and diversity combiner. In particular, we utilize the current estimates of the channel impulse response (CIR) at each diversity branch to compute the receiver parameters periodically. Moreover, we propose a novel block-adaptive strategy which computes the time-varying CIR by interpolating a set of CIR estimates obtained through periodic training. Despite incurring some inherent processing delay and throughput reduction, this interpolation strategy has the advantage of immunity to decision errors which would quite likely occur during a deep fade. Furthermore, we discovered that the system performance is limited, in the form of an irreducible bit error rate at high signal-to-noise ratios (SNR), by the CIR estimation of the rapidly fading channel.