An adaptive method utilizing channel reciprocity in TDD-LTE system

In a time-division-duplex (TDD) system the channel state information (CSI) can be obtained at the transmitter side due to channel reciprocity and it can be used to increase the spectral efficiency of a multiple-input multiple-output (MIMO) system. However, the frame architecture, system parameters, pilot architecture, the moving speed of UE and the interference structure affect the channel reciprocity. The transmission parameters assigned based on the reverse link measurements may lead to excessively high frame error rates, if the channel reciprocity doesn´t exist or interference structure between transmission directions differs significantly. In this paper, an adaptive method of TDD-LTE system is studied. This method analyzes the above factors to propose a criterion of judging the channel reciprocity, compensates asymmetric interference, and then utilize balance of channel reciprocity and feedback. Analysis and simulation results show the proposed scheme can compensate the asymmetric interference, make using the channel reciprocity possible, reduce the feedback load and demonstrate better system performance.