Performance of a decision feedback equalizer under frequency-selective fading in land mobile communications

Some means to cope with frequency-selective fading is indispensable to the realization of a wideband digital mobile communication, and various investigations have been made to this end. For example, the decision feedback equalizer (DFE) is considered promising, since it requires smaller-scale equipment and is versatile in applications. The application of DFE to mobile communication requires tracking to the time-varying channel as well as the fast initial adaptation. Thus, comprehensive investigations, including the construction of the equalizer and tap-updating algorithm are needed. The Kalman algorithm is employed as the tap-updating algorithm. By introducing the memory factor into the algorithm, the tracking performance to the time-varying channel is improved as well as the speed of the initial adaptation. A computer simulation is made for the proposed method based on the model of 256 kbit/s TDMA system with QPSK modulation. It is verified that DFE is useful in compensating for the frequency-selective fading in mobile communication.