Interference Mitigation and Traffic Offloading in OFDMA Cellular Network Using Adaptive Sectored Fractional Frequency Reuse

Abstract

Orthogonal Frequency Division Multiple Access (OFDMA) is the multi-user version of Orthogonal Frequency Division Multiplexing (OFDM). In multi-cell OFDMA system, if same sub-carriers are assigned to different users in neighboring cells, then inter-cell interference (ICI) occurs. ICI is more prominent for the users at cell boundaries due to which the cell edge users experience lower data rates compared to the users close to the base stations. To achieve Inter-cell Interference Coordination (ICIC), variants of static Fractional Frequency Reuse (FFR) schemes have been implemented. However, these schemes do not give the satisfactory performance in real networks; user distribution is non-uniform as it varies with seasons and the occurrence of major events. This is an important challenge for the mitigation of ICI. In this thesis work, adaptive FFR model is proposed as interference mitigation in order to enhance overall per user quality of service (QoS). Performance of adaptive FFR model is analyzed on the basis of drop probability, throughput, outage probability and coverage. From comparative analysis of static and adaptive frequency reuse method (strict-FFR, FFR-3, FFR-6), it is found that adaptive FFR reuse methods have better performance in terms of drop probability, coverage, outage probability and throughput.