A generalized analytical framework for coverage evaluation in mmWave heterogeneous cellular networks in urban areas

In this paper, we introduce a generalized analytical framework to evaluate the coverage probability in an mmWave heterogeneous cellular network (HetNet) consisting of UHF macrocell base stations (BSs) and mmWave small cell BSs deployed in an urban area. A generalized user association scheme that can cover a few user association schemes is formulated and applied in the mmWave HetNet. Two important statistical properties of the associated BS under this scheme are derived for the general line-of-sight and non line-of-sight pathloss channel models and they can be largely simplified if the power-law channel model is applied. Using the two statistical properties, the coverage probability of a downlink multiple-input-single-output channel is found in a compact form, which reveals that the coverage probability in the mmWave HetNet can be significantly improved if compared with the cellular network consisting of a single tier of mmWave small cell BSs. Numerical results not only validate the correctness of the coverage probability derived but also indicate that the mmWave HetNet has the potential to achieve a high coverage probability in an urban area.