Analytical evaluation of fractional frequency reuse for MIMO heterogeneous cellular networks

To increase spatial frequency efficiency and transmit capacity, multiple-input multiple-output (MIMO) heterogeneous networks (HetNets) are extensively applied in modern cellular networks. Due to consisting of K-tiers of random base-stations (BSs), MIMO HetNets certainly introduce cross-tier interference. For this problem, fractional frequency reuse (FFR), as an interference management technique, can mitigate effectively the impact of the interference. Recently, Poisson point process (PPP) is more and more used to model HetNets, because it can naturally capture the randomness of the BSs' locations. In this paper, we first develop a general downlink model based on PPP for MIMO HetNets utilizing FFR technique. This paper uses different independent PPP to model BSs' locations of each tier and considers different MIMO techniques. We derive tractable expressions of coverage probability of cell-edge user under both closed and open access cases and discuss the impact of the main parameters on the coverage probabilities.