Resource Allocation and Reuse for Inter-Cell Interference Mitigation in OFDMAbased Communication Networks

The future wireless systems are envisaged to offer ubiquitous high data-rate coverage in large areas. With the Orthogonal Frequency Division Multiple Access (OFDMA) transmission technique, great benefits in handling Inter-Symbol Interference (ISI), inter-carrier interference and providing high flexibility in resource allocation can be reaped. Nevertheless, Co-Channel Interference (CCI) or so-called Inter-Cell Interference (ICI) as a big obstacle is still remaining in OFDMA systems, which encumbers to attain both, wide area coverage and high spectral efficiency in multicellular communication networks.
It is known that effective reuse of resources in a cellular system can highly enhance the system capacity. With a smaller Frequency Reuse Factor (FRF), more available bandwidth can be obtained by each cell. So, in this sense employing the classical FRF of 1 is preferable. However, with the usage of FRF-1, most User Terminals (UTs) are seriously afflicted with heavy ICI, especially in the border areas of cells. And this causes low cell coverage and inferior system capacity. Conventional method to figure out this problem is by increasing the cell-cluster-order to avoid the reuse of the same frequency bands in neighboring cells, which can mitigate the ICI efficiently, nonetheless at the cost of a decrease in available bandwidth for each cell. This would
result in reduced cell capacity and lower system spectrum efficiency in general, and would worsen in the case of unbalanced traffic distribution among cells. Thus, it is desirable to combat the ICI by other means. A promising method to solve the ICI problem is ICI coordination, which may potentially attain significant performance improvements and has become very important in next generation wireless communication networks. To take aim at
improving cell-edge performance while retaining system spectrum efficiency of Reuse-1, several representative local ICI coordination approaches with static frequency resource partitioning are introduced and studied at first in this monograph, including the classical Fractional Frequency Reuse (FFR) scheme, the well-known Soft Frequency Reuse (SFR) scheme and the newly emerged Incremental Frequency Reuse (IFR) scheme. Based on thoroughly analysing the advantages and limitations of these approaches, a novel ICI mitigation design called Enhanced Fractional Frequency
Reuse (EFFR) scheme and its two derivatives (the EFFR-Advanced scheme and EFFR-Beyond scheme) are proposed for a better fulfillment of the goals, namely, to enhance the mean system capacity while restraining the ICI at the cell edge. The EFFR scheme designs a resource allocation and reuse mechanism combined with power allocation and interference-aware reuse. Taking the inherent vulnerability of the Cell-Edge Users (CEUs) into account, the EFFR scheme reserves resources for them with two specific emphases: 1) using dedicated FRF-3 subchannels; 2) data transmission with higher transmit power. Taking advantage of the location-specific predominance of the Cell-Centre Users (CCUs), the EFFR scheme allows them to occupy resources with FRF-1 and interference awareness. The performance evaluations are done by means of both, analytical models and stochastic even-driven simulation. The presented results show that the EFFR schemes can efficiently mitigate the ICI in OFDMA-based cellular networks and outperform
the SFR scheme, the IFR scheme and static Reuse schemes under any propagation condition. With the usage of the EFFR scheme, the medium is able to be more effectively utilized; higher flexibility as well as more robustness can be attained; the overall cell capacity is significantly improved; and the cell coverage can be substantially enlarged.