| MIMO and relay technique have been widely studied and employed in order to meet the demands in the new-generation wireless communications. The multi-antenna system with fixed relays can boost coverage and link capacity in cellular networks especially in regions with significant shadowing, and achieve high-data-rate communication far from the base-station at the cell edge. But fixed relays will also increase the interferences between users and degrade system performance severely. In this thesis, we address the problem of suppressing inter-user and relay-to-user interference and propose the schemes to mitigate the effect of interference correspondingly. The main works are as follows:1. The deleterious effects of interference in distinct slots employing different types of relays are discussed, and the precoding schemes for interference suppression are studied. Simulation results show that the precoding schemes can only act well when the number of receiving antennas is small and single-slot precoding scheme may not mitigate the interference in AF relay system.2. A multi-slot joint precoding algorithm for interference suppression is proposed, which can eliminate the interference from AF relay when it relays the signal in the second time slot.3. Combing the precoding method, a power allocation based interference suppression scheme is proposed, which can be applied to AF and DF relay systems. Simulations results show that the proposed algorithm can significantly improve system capacity, and impose no harsh demand for the number of transmit and receive antennas. |
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