Research On The Channel Reciprocity In Massive MIMO Systems

Massive MIMO is a key technology in the next generation communications.The Massive MIMO system has many advantages.As the number of antennas increases.the channel performance tends to be ideal.In addition,the channel capacity and spectral efficiency can be greatly improved.A major advantage of Time Division Duplex Massive MIMO system is the use of channel reciprocity,so that the acquisition of the uplink and downlink channel status information is more convenient and the system overhead is reduced.However,the channel reciprocity in the actual environment will be affected by I/Q imbalance,time-varying channel and other factors,thus reducing system performance.In this paper,channel estimation and channel prediction are used to compensate channel reciprocity in Massive MIMO system.The specific work is as follows:(1)Aimed at the main influencing factors of reciprocity as time-varying channel and I/Q imbalance,the Massive MIMO system was modeled and analyzed respectively,and the feature abstraction and model construction under the new feature of Massive MIMO system were completed.(2)By using the channel prediction algorithm based on the effective prediction interval,a channel reciprocity compensation algorithm in the time-varying Massive MIMO system is proposed.The simulation results show that the proposed algorithm has a good compensation effect on the channel reciprocity in the Massive MIMO system with time-varying channel.The proposed algorithm has a lower complexity and better performance than the traditional methods.(3)Based on the semi-blind channel estimation algorithm based with subspace tracking,a compensation algorithm for channel reciprocity in Massive MIMO systems with I/Q imbalance is proposed.The simulation results show that the proposed algorithm has a good compensation effect for the channel reciprocity in Massive MIMO systems under I/Q imbalance,which greatly reduces the complexity compared with the traditional methods and can effectively reduce the pilot pollution and other issues in Massive MIMO system.