Performance analysis of IEEE 802.11.ad downlink hybrid beamforming

Hybrid beamforming (BF) is a widely considered strategy to enable downlink multiuser transmission for mmWave communication systems. However, current mmWave WiFi standard, the IEEE 802.11 ad, does not support hybrid BF because it could only serve one user at a time. Thus, it is important to implement hybrid BF based on IEEE 802.11.ad such that it could be applied in future mmWave WiFi. In this paper, we propose a hybrid BF scheme compatible with the IEEE 802.11 ad, and then analyze its BF overhead and throughput gain. Theoretical analysis and simulation results show that with the increasing number of users, BF overhead increases linearly, whereas the throughput gain increases and then decreases. Specifically, we analyze the tradeoff between the hybrid BF overhead and the throughput gain of multiuser transmission enabled by hybrid BF based on an IEEE 802.11 ad setting. Our finding suggests that there is an optimal number of users that a hybrid BF enabled mmWave communication systems should support.