Coverage Probability of Analog Beamforming with Limited Feedback in mmWave Cellular Networks

This paper characterizes a coverage probability of a mmWave cellular network with limited feedback. Considering a downlink mmWave cellular model based on stochastic geometry, which incorporates blockage effects and limited feedback of analog beamforming, an analytical expression for the coverage probability of the instantaneous signal-to-interference ratio (SIR) is derived in terms of relevant system parameters, chiefly the number of antennas elements per BS, and the pathloss exponent values for line-of-sight (LOS) and non-line-of-sight (NLOS). Our results indicate that the number of feedback bits for analog beamforming with an uniform linear array needs to scale with the number of antenna elements logarithmically at least to obtain a reasonable directional beamforming gain. Furthermore, our result confirms the intuition that the blockage effect leads to a significant coverage performance degradation for the millimeter cellular network.