Stochastic Geometry Based Framework for Coverage and Rate in Heterogeneous Networks with Sectored Fractional Frequency Reuse

Abstract

Modern day cellular networks are driven by the need to provide ubiquitous connectivity with very high spectral efficiency to both indoor and outdoor users, hence the need to deploy small cells over conventional macrocells in a Heterogeneous Network (Hetnet) deployment. To alleviate the resulting inter-cell and cross-tier interference, effective inter-cell interference coordination (ICIC) schemes such as Fractional Frequency Reuse (FFR) are employed, and have been widely studied in perfect geometry network scenarios which are too idealistic and not easily adaptable to the complexity of Hetnets. This work provides an analytical framework for the performance of such FFR schemes in Hetnets with antenna sectorization employed at the macro tier, by leveraging stochastic geometry tools to model base station locations of both macro and femto tiers using the Poisson Point Process (PPP). We study the effects of varying system parameters and consider cross-tier femto interference commonly ignored in many analytical works in literature. Furthermore, the femtocells employ a sensing algorithm to minimize spectrum sharing with macro users in close proximity, especially at the transition areas of center and edge region where cross-tier interference could be monumental. Numerical simulations are used to evaluate performance of the proposed framework in terms of coverage probability and average user rate, and results are compared with traditional FFR schemes and the No-FFR deployment. To the best of the author’s knowledge, this is the first analytical framework characterizing sectored-FFR schemes using stochastic geometry tools in Hetnets.