AoD Based Joint User-Antenna Scheduling Schemes with Limited Feedback for Multi-User Massive MIMO FDD Systems

This article deals with the problem of channel state information (CSI) acquisition by feedback for downlink user scheduling (US),which is one of the major bottlenecks in multi-user massive multiple-input multiple-output frequency division duplexing (MU-mMIMO FDD) system with limited available uplink feedback resources. Towards the resolution of this feedback based US problem, in this work we consider MU-mMIMO FDD systems with US relying on limited feedback with minimum ceiling effect to the throughput. We develop various signal-to-interference-plus-noise ratio (SINR) based one step feedback US strategies to improve throughput with limited feedback. These schemes utilize the angle of departure (AoD) information which is slowly varying in nature and can be preferred to be effective for user-antenna joint scheduling algorithms in reducing the amount of feedback. Here, SINR is a function of dominant channel qualities, i.e., dominant path gains and path AoDs. Moreover, in order to maintain the trade-off between the system throughput and the feedback load, this article employs the joint user-antenna scheduling with limited or opportunistic feedback approach. Inspired by the above, we have devised four AoD based joint user-antenna scheduling approaches namely maximum SINR feedback, maximum SINR array feedback, selective maximum SINR feedback, and selective maximum SINR array feedback for solving US problem for MU-mMIMO FDD framework. Finally, we examined the performance of these scheduling approaches. Simulation results show that, the proposed opportunistic user-antenna joint scheduling methods provide attractive gain in system throughput with significant CSI overhead reduction as compared to different baseline schemes/strategies. Therefore, the proposed schemes can be useful in the future MU-mMIMO FDD fifth-generation and beyond system deployment scenarios.