Tractable model for heterogeneous cellular networks with directional antennas

Heterogeneous cellular networks consisting of microcell, picocell, femtocell, distributed antennas and relays codeployed in space and frequency with carefully planned tower-mounted base stations, increase the complexity of the cellular network structure, which makes a tractable analysis model difficult to obtain. In this paper, we extend the original tractable model for downlink heterogeneous cellular network to the scenario with directional antennas, from which the coverage probability (or equivalently outage probability) for a randomly located mobile user in this network can be derived. By using this tractable model, the impact of implementing directional antenna for certain heterogeneous tiers can be demonstrated and utilized as a deployment guideline.