Analysis and Design of Distributed Antenna-Aided Twin-Layer Femto- and Macrocell Networks Relying on Fractional Frequency Reuse

Distributed antenna systems (DASs) and FemtoCells (FCs) are capable of improving the attainable performance in the cell-edge area and in indoor residential areas, respectively. To achieve high spectral efficiency (SE), both the distributed antenna elements (DAEs) and FC base stations (FBSs) may have to reuse the spectrum of the macrocellular network. As a result, the performance of both outdoor MacroCell (MC) users (OMU) and indoor FC users (IFUs) suffers from CoChannel Interference (CCI). Hence, in this paper, heterogenous cellular networks are investigated, where the DAS-aided MCs and FCs coexist within the same area. Both the outage probability (OP) and the spatially averaged throughput are derived, and the network is optimized either to minimize the OP or to maximize the MC's throughput. Our analysis demonstrates that surprisingly, the unity frequency-reuse (UFR)-based macrocellular system can be optimized in isolation, without considering the impact of FCs. We found that the MCs relying on fractional frequency reuse (FFR) tend to be converted to several small cells, illuminated by the DAEs, when the density of FCs becomes high.