Cooperative base station processing in multidimensional interference

Cooperative base station (CBS) processing takes advantage of the entire infrastructure fabric in system-wide multiuser detection (MUD) of each and all mobile stations (MSs). It is a promising paradigm for increasing the efficiency of future wireless communications systems, benefiting from increased dimensionality through macrodiversity as well as increasing the capacity largely through the achievement of full frequency reuse. Managing the high levels of interference occurred in this scheme is the main dilemma discouraging the practical implementation. In this thesis, we introduce innovative methods to handle and reduce co-channel interference in the uplink of CBS systems. Based on the groupwise iterative multiuser detection (IMUD), we come up with a new way to reduce the complexity of belief propagation (BP) algorithm. The resulting reduced complexity BP (RCBP) algorithm is a flexible, efficient technique that can be used for joint detection in a variety of high interference situations. We apply RCBP for distributed MUD in CBS uplink and show that its performance is close to that of the BP algorithm at lower computational cost in the simplified channel model and it has excellent performance in joint decoding and detection using the low-density parity-check (LDPC) codes. We also examine CBS processing in a realistic wireless network model, and illustrate how system-wide RCBP MUD can successfully detect the co-channel signals originating from the MSs in the neighbouring cells, included in the detection set. However, the system performance in such system is limited by the unmodeled interference from the MSs outside the detection set. We apply the RCBP algorithm for MUD in frequency selective multiple-input, multiple-output (MIMO) channels. Our study proves that the RCBP is an efficient equalizer dealing with inter-symbol interference in high interference situations and in iterative joint detection and decoding. In order to reduce the unmodeled interference in CBS networks, we propose a novel power control policy for CBS uplink allowing the MSs to control according to the total received power in their detection set. We investigate the performance of this method and show that it reduces the intercell interference, saves power and improves the BER performance.