An adaptive filtering technique for pilot-aided transmission systems

One of the main design tradeoffs of pilot-based techniques of combating the effects of multipath fading is the pilot filter bandwidth. The approach presented is to store a precalculated bank of pilot filters and automatically select the best one as the signal-to-noise, (SNR) or vehicle speed change. The authors address the issue of adjusting the filter bandwidth as speed changes. They call this technique the filter switching algorithm. This 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 direction have little effect on its operation and the resulting bit error rate