Single-User Receivers for Partly Known Interference in Multi-User Environments

Abstract: In multiuser environments such as cellular radio systems, the limited available bandwidth is one of the principal design constraints. For future high subscriber density systems, frequency reuse is one of the fundamental approaches for efficient spectrum utilization in order to meet the increased demands for capacity. The tolerable co-channel interference at the receivers in the system limits the minimum allowable distance among nearby co-channel users. In turn, the system capacity is limited. In order to achieve a high capacity in such multiuser environments, receivers and modulation techniques must be interference resistant. Conventional receivers are designed to operate in thermal noise without cochannel interference. For performance evaluation in cellular systems, the Gaussian interference model is commonly used, i.e. co-channel interference is modeled as additional thermal noise. In this thesis, we study the co-channel interference in the downlink (transmission from base to mobile station) in symmetrical cellular environments. The results demonstrate that the strongest interferer dominates the total received co-channel interference. One approach to improve the performance in multiuser environments is to use receivers designed for interference environments. We address the design and performance issues for interference adaptive receiver techniques that take advantage of our knowledge of the interference properties. We consider receiver design approaches based on the amount of interference information assumed, and we introduce optimized single interferer adaptive receiver schemes. Performance evaluations in the downlink of symmetrical cellular systems show that by using single interferer adaptive receivers, the cell average error probability and the cell outage probability are significantly reduced. Consequently, the system capacity increases as compared to a system with conventional receivers.