4. Beamforming Training Protocol Design and Analysis

In this chapter, we present beamforming training protocol design and analysis for both single-user transmission and multiuser transmission scenarios. Firstly, in the single-user transmission scenario, we focus on the current 802.11ad standard analyzing its beamforming training performance from a perspective of the medium access control (MAC) layer. Specifically, we present a simple yet accurate analytical model to evaluate MAC performance. Based on the analytical model, we derive the closed-form expressions of average successful beamforming training probability, normalized throughput, and beamforming training latency. Particularly, asymptotic analysis indicates that the maximum normalized throughput of BFT-MAC is barely 1∕e. Moreover, we introduce an enhancement scheme which adaptively adjusts the MAC parameters in tune with user density, to improve MAC performance in dense user scenarios. Extensive simulation results validate the accuracy of the presented analytical model and the effectiveness of the introduced enhancement scheme. Secondly, in the multiuser transmission scenario, since 802.11ad only serves one user at a time, we present a novel 802.11ad-compliant multiuser beamforming training protocol to facilitate multiuser transmission in millimeter-wave networks. Then, we analyze the overhead of the presented multiuser beamforming training protocol. Simulation results show that the effectiveness of the presented protocol as compared to the benchmark protocol.