Fractional Frequency Reuse in LTE Networks

Abstract

LTE supports Orthogonal Frequency Division Multiple Access (OFDMA) communication system where frequency reuse of one is used, i.e. all cells/sectors operate on the same frequency channel to maximize spectral efficiency. However, due to heavy Co-channel Interference (CCI) in frequency reuse one deployment, UEs at the cell edge may suffer degradation in connection quality. With LTE, UEs operate on subchannels, which only occupy a small fraction of the whole channel bandwidth; the cell edge interference problem can be easily addressed by appropriately configuring subchannel usage without resorting to traditional frequency planning.

Resource allocation in multi-cell OFDMA networks has been developed in several works using Fractional Frequency Reuse (FFR) . However, only few contributions have explicitly taken into account the nature of application being either real time or non-real time. For example, authors in [1,2] proposed dynamic resource allocation scheme for guaranteeing QoS requirements while maximizing the whole throughput of the system. However, both schemes work only for non-real-time application. Qi and Ali-Yahiya [3,4] introduced the Radio Network Controller (RNC) to control a cluster of Base Station (eNodeBs) in the multi-cell OFDMA system and to allocate resources in a distributed way; however, these schemes allocate resources in the RNC without taking into account the reallocation scheme at each eNodeB for coordinating resource according to the FFR. Authors in [5] proposed a local resource allocation the eNodeBs in a random way without taking into consideration the RNC. Thus the eNodeB has not a global view about the adjacent cells in the system, leading to inefficient resource allocation.