Performance Analysis of Fractional Frequency Reuse Based on Worst Case Signal to Interference Ratio in OFDMA Downlink Systems Sherief Hashima, Masoud Alghoniemy Osamu Muta, Hiroshi Furukawa Hossam Shalaby Department of Electrical Engineering Electronics & Communications Department Faculty of Engineering, Alexandria University Center for Japan-Egypt Cooperation in Science and Technology (EJUST Center) Egypt Japan University of science and technology (EJUST) Alexandria, Egypt Kyushu University Alexandria, Egypt saidelnoubi@yahoo.com Fukuoka, Japan sherif.mostafa@ejust.edu.eg alghoniemy@alexu.edu.eg muta@ait.kyushu-u.ac.jp shalaby@ieee.org furuhiro@ait.kyushu-u.ac.jp Abstract— Fractional Frequency Reuse (FFR) is an efficient method to mitigate Inter Cell Interference in multicellular Orthogonal Frequency Division Multiple Access (OFDMA) systems. In this paper, we analyze the downlink worst case Signal to Interference Ratio for FFR schemes. A closed form expression is derived analytically for the worst SIR, outage probability, and Spectral Efficiency (SE). The proposed analytical technique is used to configure a FFR solution for the downlink of OFDMA cellular system.The analysis is performed using two-tiers cellular network with uniform user density and for three different cases of FFR, namely, Frequency Reuse Factor (FRF) = 3, FRF=4 and sectored FFR. The inner radius configuration depends on equalizing the worst SIR for both inner and outer edges of the cell. Numerical results show that sectored FFR yields the highest SE and low outage probability. Sectored FFR highly balances the needs of interference reduction and resource efficiency. Keywords: Inter-cell interference cancellation, fractional frequency reuse I. INTRODUCTION In future mobile communication systems, the growing demand on wireless data traポc is the main motivation of the industry and academia investment in OFDMA based 4G networks. Several wireless cellular standards such as the Third General Partnership Project (3GPP) Long Term Evolution (LTE), 3GPP2 Ultra Mobile Broadband (UMB), and mobile Worldwide Interoperability for Microwave Access (WIMAX) are all OFDMA cellular systems [1]. The main interference in OFDMA system is due to inter-cell interference (ICI) which deteriorates cell edge user’s performance. Cell-edge users suffer from strong interference when universal frequency or reuse one is used; leading to poor performance at cell edges. ICI mitigation techniques can be grouped into three different approaches, namely, randomization, cancelation, and coordination [2, 3]. FFR belongs to coordination strategy where a significant capacity improvement can be gained by using two different reuse factors instead of one [2]. Discussion and evaluation of different interference management techniques can be found in [4], [5]. Frequency reuse is the most commonly used interference coordination technique, where neighbouring cells do not use the same frequency band. In particular, let 軽 頂 be the number of cells per cluster, then clusters of size 軽 頂 share the whole bandwidth according to the value of FRF. In particular, each cell uses only 怠 朝 迩 of the BW; thus neighbouring cells inside the cluster would not interfere with each other. An obvious disadvantage of frequency reuse is the reduction of SE due to the use of only 怠 朝 迩 of the available BW [3, 4, and 15]. High frequency reuse improves cell edge performance at the expense of reducing the cell average throughput. Figure1.Two-tier network with FFR three FFR with reuse three was first proposed in [7] to balance the link throughput across the coverage area where Cell Center Users (CCUs) use universal 2013 IEEE 24th International Symposium on Personal, Indoor and Mobile Radio Communications: Fundamentals and PHY Track 978-1-4577-1348-4/13/$31.00 ©2013 IEEE 616