PHP-Based Coverage Analysis in Millimeter Wave Heterogeneous Cellular Network

With severe spectrum shortage and high capacity requirement in future cellular networks, millimeter wave (mmWave) frequencies is a candidate for next-generation wireless networks. Due to the sensitivity of mmWave signals to blockage and using directional beamforming in both transmitter and receiver, novel models are needed to analyze cellular networks operating in mmWave frequencies. Base station (BS) locations in heterogeneous cellular networks (HCNs) is often modeled by a Poisson point process (PPP). While it is a proper model due to the randomness of BS locations, it can not accurately model the network when we have multi-tiered BSs, e.g. macro cells and small cells. The effect of spatial separation between tiers leads us to model BS locations as a Poisson hole process (PHP). Using tools from stochastic geometry, this paper proposes a framework to evaluate the coverage performance in a two-tier mmWave HCN. Since the exact formulation of coverage probability based on PHP modeling of SBSs is not known, different approaches are proposed and fairly accurate expressions for coverage probability are derived and validated by simulation results. It turns out that the analysis based on the proposed model is more accurate for a two-tier HCN than independent PPP-based analysis. Index Terms Millimeter wave cellular network, heterogeneous cellular network, stochastic geometry, Poisson Hole Process, coverage probability.