Abstract
In this dissertation, we propose a new intercarrier interference (ICI) cancellation scheme for orthogonal frequency division multiplexing (OFDM) based cooperative relay systems using conjugate transmission, which involves an adaptive receiver design and a relay selection strategy. The proposed adaptive receiver not only applies two phase rotations on the two receive paths carrying conjugate OFDM symbols, but also employs an amplitude scaling factor on each subcarrier of the second receive path. Unlike a previous receiver design where the same amplitude scaling factor is applied to all subcarriers, the proposed one allows individual adjustment of the amplitude scaling factor over each subcarrier to approach optimal ICI cancellation. We also develop a new relay selection mechanism based on the proposed receiver structure, where the signal-to-noise ratio (SNR) and carrier-to-interference ratio (CIR) bounds are jointly evaluated for each relay pair and the one with the highest SNR/CIR bound is selected for transmission. Simulation results show that the proposed adaptive receiver outperforms previous designs, especially in ICI-dominated environments. It is also demonstrated that the proposed relay selection method provides better bit-error-rate performance than other related approaches.