An adaptive filtering technique for pilot aided transmission systems

It is demonstrated that adaptivity in pilot filter bandwidth can produce a significant improvement in the bit error ratio (BER) of a pilot aided calibration system. The utility of adjusting the filter bandwidths as vehicle speed changes is addressed. Since the optimum bandwidth varies with vehicle speed, some form of adaptivity is desirable. The adaptation technique is novel; the receiver selects the optimum member from a precalculated bank of stored filters, thereby reducing the search to one dimension. The technique can provide a 1.0 dB improvement for a normalized Doppler frequency of 2%; up to 2.0 dB can be gained when operating at a lower Doppler frequency. The algorithm is found to be very robust, in the sense that self-noise and decision feedback have little effect on its operation and the resulting BER