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“Transciever Design and Performance Analysis of Adaptive Bit-Interleaved Coded MIMO-OFDM Systems”
by Fu-Hsuan Chiu
December 2006
This dissertation contains novel transceiver design for multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems without knowledge of channel state information (CSI) in priori.First, an iterative approach of joint channel tracking and symbol detection algorithm over time-varying MIMO-ISI channels based on the principle of EM algorithm is presented. This recursive approach, EM-SD, could be viewed as the Kalman filter with soft decision feedback. A soft sphere decoder with soft interference cancelation was proposed to lower the complexity of the BCJR algorithm when large input signal constellation was used.Second, a complete solution to joint channel tracking and symbol detection for bit-interleaved MIMO-OFDM systems in a time-varying frequency-selective fading environment is proposed in this research. In the training mode, the Rao-Blackwellised particle filter (RBPF) is used to estimate the phase offset (PO) and the carrier frequency offset (CFO). The EM-SD algorithm is then applied in data mode to perform the minimum mean squared error (MMSE) channel estimation and the maximum a posterior (MAP) probability symbol detection jointly.Finally, feedback-directed adaptive scheme is shown to achieve the same pre-log factor of the lower bound of the noncoherent capacity of MIMO-OFDM systems in ergodic channels. It also has the same tradeoff of diversity and multiplexing gain as the MIMO systems employed with random Gaussian codewords in nonergodic channels. It is shown that throughput of OFDMA with opportunistic scheduling performs better than traditional OFDM-TDMA scheduling with constant enhancement independent of SNR in multiuser downlink environment.
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