A learning receiver for communication in three-component multipath channels
Richard Paul Brueggemann · 1972
An adaptive receiver is designed for transmissions through a time-varying multipath channel which may include both specular and diffuse components. The design is based on the theory of unsupervised learning machines and the receiver is a recursive structure which. does not qrow in complex! ty with each new observation, but ii is Bayes' optimal at each instant of time. The multipath mediU!n is modelled as an aggregate of L conditionally independent transmission paths, each consisting of random and/or fixed reflections, and is identified in terms of three components: (1) indirect diffuse scatter, (2) indirect specular reflection, and (3) direct transmission. The channel parameters are time-varying and either independent from one signaling interval to the next or at most M-th order Markov dependent. A review of machines that learn without a teacher is presented and the learning receiver for three-component multipath is designed and modelled on the digital computer. A Monte Carlo simulation is used to estimate the performance when the channel is either Rician or nonfading. This performance, in terms of probability of error, is shown to be consistent with the existing coherent receivers and improves on their performance When the correlation between observations is increased.