On the use of H-inf criterion in channel estimation and precoding in massive MIMO systems

In this paper, a channel estimation (CE) and precoding scheme by using H-infinity (H-inf) criterion for mitigation of pilot contamination (PC) in massive multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is investigated. Firstly, different thresholds in H-inf CE and precoding are considered. Secondly, asymptotic analysis is presented to simplify the H-inf precoding, which shows that the complexity of an order of magnitude is reduced. Thirdly, approximate downlink achievable data rates per user are studied for different CE and precoding schemes, such as H-inf and minimum mean square error (MMSE) CE, MMSE, zero-forcing (ZF) and H-inf precoding. The analysis shows that the proposed scheme can provide dual mitigation to the PC. That is, the H-inf CE mitigates the PC by adjusting its thresholds, and the H-inf precoding is utilized to suppress the PC by considering inter-cell interference. The numerical results show that joint use of H-inf CE and H-inf precoding outperforms existing schemes in terms of mitigation to the PC.