Adaptive signal processing for radio communications

A tutorial examination of adaptive processors for radio communication applications is presented. The general form of adaptive equalizers and Maximum Likelihood Sequence Estimators is discussed. The method of determining the performance of an adaptive equalizer in a fading channel environment is summarized. A simple example illustrates how implicit diversity is realized by channel adaptation. Methods of adaptation including Kalman filter techniques are presented along with performance results of practical fast adapting systems. The use of channel adaptation with error correction coding is also examined and practical results presented. These results show that most of the fading effect can be eliminated when there is no restriction on channel time delay. Multiple channel adaptive processors which eliminate correlated interference are also discussed. Performance results for a tropospheric scatter application are predicted and compared with laboratory measurements on a real system. Methods of fast adaptation of these multi-channel processors are discussed.