Compensating Non-Reciprocity Of Time-varying TDD-MIMO Channel Using Channel Prediction

With an enormous advantage of achieving high system capacity, MIMO technique has been one of the widely used techniques in future wireless communication systems. By using channel reciprocity in time division duplex(TDD) MIMO systems, the base station(BS) can preprocess transmitting data according to the channel state information (CSI) obtained by uplink measurement without additional feedback overhead. But time-varying channel leads to the loss of channel reciprocity, which will invalidate the advantage of TDD systems.This thesis analyzes the impact of time-varying channel on channel reciprocity in TDD-MIMO communication systems. And then method compensating channel reciprocity is proposed. The main contributions are as follows:1. The time-varying channel model NE-3GPP SCM (newly extended-3GPP spatial channel model) and the frame structure applicable to TDD systems are discussed, and the characteristics of time-varying channel are analyzed.2. According to the SVD-based systems, the capacities over time-invariant channel and time-varying channel are derived respectively. Simulation results show that the bit error rate(BER) performance and system capacity are severely degraded over time-varying channel,the channel reciprocity is destroyed.3. A compensation method is given to compensate the loss of channel reciprocity due to time-varying channel. Simulation results show that, using channel prediction in BS can significantly improves the BER performance and the system capacity. Thus, the channel reciprocity is compensated effectively.