Adaptive Optimization of Least Squares Tracking Algorithms: With Applications to Adaptive Antenna Arrays for Randomly Time-Varying Mobile Communications Systems

摘要

Adaptive antenna arrays are widely used for reducing the effects of interference and increasing capacity in mobile communications systems. The adaptation typically consists of updating the antenna weights by a recursive least-squares-type algorithm. We will add another adaptive loop that greatly improves the operation when the environment for the various links is randomly time-varying. The analysis is via stochastic approximation type arguments. Consider a single cell system with an (receiving) antenna array at the base station. Algorithms for tracking time varying parameters require a balance between the need to follow changes (implying a short memory) and the need to average the effects of disturbance (implying a long memory).