Analytical Evaluation of Fractional Frequency Reuse for OFDMA Cellular Networks

Abstract

Fractional frequency reuse (FFR) is an interference management technique\nwell-suited to OFDMA-based cellular networks wherein the cells are partitioned\ninto spatial regions with different frequency reuse factors. To date, FFR\ntechniques have been typically been evaluated through system-level simulations\nusing a hexagonal grid for the base station locations. This paper instead\nfocuses on analytically evaluating the two main types of FFR deployments -\nStrict FFR and Soft Frequency Reuse (SFR) - using a Poisson point process to\nmodel the base station locations. The results are compared with the standard\ngrid model and an actual urban deployment. Under reasonable special cases for\nmodern cellular networks, our results reduce to simple closed-form expressions,\nwhich provide insight into system design guidelines and the relative merits of\nStrict FFR, SFR, universal reuse, and fixed frequency reuse. We observe that\nFFR provides an increase in the sum-rate as well as the well-known benefit of\nimproved coverage for cell-edge users. Finally, a SINR-proportional resource\nallocation strategy is proposed based on the analytical expressions, showing\nthat Strict FFR provides greater overall network throughput at low traffic\nloads, while SFR better balances the requirements of interference reduction and\nresource efficiency when the traffic load is high.\n