| Summary: | 碩士 === 國立交通大學 === 電信工程系所 === 95 === Limited feedback precoding is a technique used to improve system reliability in modern wireless communications. The feature of limited feedback precoding is that receiver feeds back the index of the optimal precoder to the transmitter. The transmitter does not need to have any channel state information (CSI). In this thesis, we focus on the transmit beamforming scheme in multiple-input single-output (MISO) systems. In conventional approach, under a fixed average feedback rate, the single-mode limited feedback system (has only one codebook) is not robust enough in time-varying channels. Perfect channel knowledge known at the receiver, error-free feedback channel, and first-order Markov MISO channel model are assumed in this thesis. We propose a dual-mode limited feedback system with a symbol-error-rate (SER) based mode selection criterion. Two transmit beamforming modes over two consecutive time slots are considered: (1) separate beamforming for the individual time slot with a small-size codebook, and (2) joint beamforming for both slots with a large-size codebook. By exploiting the temporal-correlation coefficient of two consecutive time slots and perfect channel knowledge, the better mode can be selected by using the mode selection criterion. Simulation results show that the performance of the dual-mode limited feedback system is better than that of the single-mode limited feedback system.
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