Interference Avoidance for Wireless Systems with Multiple Receivers

Interference avoidance is a class of adaptive modulation techniques in which, with feedback from the receiver, a transmitting radio is instructed to vary its waveform so as to maximize the signal-to-interference plus noise-ratio. For an ensemble of users connected to a single receiver interference avoidance methods have been thoroughly analyzed. This thesis provides insight into application of interference avoidance methods to systems with multiple transmitters and receivers, which consist of a collection of base stations and associated users that share the same bandwidth for communication. After a brief review of interference avoidance for single base station systems, we present a code-word adaptation algorithm for collaborative multi-base wireless systems based on greedy interfer-ence avoidance. The system is modeled with multiple inputs and multiple outputs and information is transmitted using multicode CDMA. We continue with the collaborative scenario and derive bounds on sum capacity and total squared correlation in the case of flat channels between users and bases. We also investigate structural properties which must be satisfied by user transmit covariance matrices at the optimal sum capacity/TSC point, and show that for multi-base systems maximizing sum capacity and minimizing TSC are in general not equivalent problems