Adaptive Interference Avoidance for Dynamic Wireless Systems

Abstract

The paper presents an interference avoidance algorithm for codeword and power adaptation in the uplink of a Code Division Multiple Access (CDMA) system with variable number of active users. The algorithm tracks changes in the system configuration, and transitions incrementally from one optimal point corresponding to a given number of active users to a new optimal point corresponding to the new number of active users. The transition uses gradient-based adaptive interference avoidance in which users adapt their codewords to optimize their corresponding spectral efficiency subject to constraints on the signal-to-interference plus noise-ratio (SINR). The algorithm is illustrated with numerical examples obtained from simulations.