Robust Multiuser Precoder for Base Station Cooperative Transmission with Non-Ideal Channel Reciprocity

In this paper we present a method to alleviate the performance degradation led by non-ideal channel reciprocity in TDD downlink base station (BS) cooperative transmission systems, which comes from imperfect antenna calibration among BSs. By exploiting the statistics of the ambiguity factors between uplink and downlink channels, a robust multiuser precoder is proposed aimed at maximizing the lower bound of the average signal-to-leakage-plus-noise ratio (SLNR). The precoder is able to adaptively control the cooperation level among the coordinated BSs according to the antenna calibration accuracy among BSs. Simulation results demonstrate an evident performance gain of the proposed robust precoder over the non-robust precoder.