Radio Resource Management in Multi-Tier Cellular Wireless Networks

CHAPTER 5

RESOURCE ALLOCATION IN TWO-TIER NETWORKS USING FRACTIONAL FREQUENCY REUSE

5.1 INTRODUCTION

In OFDMA-based two-tier networks such as the macrocell–femtocell networks, co-tier/cross-tier and UL/DL interferences occur only when the aggressor (or the source of interference) and the victim use the same sub-channel. Therefore, it is essential to adopt an effective and robust interference management scheme that would mitigate the co-tier interference and reduce the CTI considerably in order to enhance the throughput of the overall network. As has been discussed in Chapter 2, different techniques such as cooperation among Macro evolved Node B (MeNB) and HeNBs and collaborative frequency scheduling [1], formation of groups of HeNBs and exchange of information (such as path-loss, geographical location, etc.) among neighboring HeNBs [2], power control approach [3, 4], and intelligent spectrum access [5] have been considered in the recent literature to reduce co-tier interference and CTI. However, in this chapter, we concentrate on an interference avoidance technique known as the FFR method (also advocated by Femtoforum in [6]1), which requires minimal cooperation among BSs, has a less complex operational mechanism, and is well-suited for OFDMA-based LTE-Advanced systems.

The basic mechanism of FFR corresponds to partitioning the macrocell service area into spatial regions and each sub-region is assigned with different frequency sub-bands. Therefore, the cell edge-zone MUEs do not ...