Coordinated multipoint in heterogeneous networks: A stochastic geometry approach

Motivated by the ongoing discussion on coordinated multipoint in wireless cellular standard bodies, this paper considers the problem of base station cooperation in the downlink of heterogeneous cellular networks. The focus of the paper is the joint transmission scenario, where an ideal back haul network allows a set of randomly located base stations, possibly belonging to different network tiers, to jointly transmit data, so as to mitigate intercell interference and hence improve coverage and spectral efficiency. Using tools from stochastic geometry, an exact integral expression for the network coverage probability is derived in the scenario where a typical user can coherently combine the received signal from a pool of base stations, that are selected based on their average received power strengths or distance from the receiver. In the special case where cooperation is limited to two base stations, numerical evaluations illustrate relative gains in coverage probability of up to about 30% compared to the non-cooperative case.