Interference Management Using Fractional Frequency Reuse for Ultra Dense Networks at Downlink Transmission

Abstract

Small cells i.e., one of them is femtocell are solution to enhance network capacity and to expand quality of services to users who are at indoors and outdoors areas. However, femtocells that are deployed within the macrocell area encounter interference problems because the radio resources are shared between the femtocells and the macrocells. The interference problems become worse when the femtocells deployed are many and dense forming Ultra Dense Networks (UDN). Therefore, the network performances are deteriorated, especially in the cell edge area. To overcome this problem, we propose interference management using the Fractional Frequency Reuse (FFR) scheme at downlink transmissions. The FFR mechanism aims to minimize cross-tier interferences by allocating different sub-bandwidths at the cell edge areas, so that the usages of radio resources do not overlap to the usages in other geographic locations. Therefore, the network performances of the femtocells can be improved. We evaluate the performance of FFR scheme through a simulation experiment and compare the performances to a baseline system. The simulation results show that the FFR scheme applied outperforms the baseline system. In term of Signal to Interference plus Noise Ratio (SINR), when we consider the SINR equal to or less than 20 dB, then the probabilities of SINR not reaching the target for the baseline system and FFR scheme in the cell edge area are 100% and 82%, respectively. It achieves 18% of improvement with FFR scheme for our considered network setting.