Energy efficiency and optimal threshold for FFR schemes in OFDMA cellular networks

Abstract

As large energy consumers, base stations need energy-efficient wireless access networks. An advanced energy efficiency measure was developed in this paper, considering throughput, the number of served users, and actual coverage area. The actual coverage area considered in the proposed measure is also in harmony with the measured network coverage area proposed by ETSI ES 203 228 V1.1.1 standard [1] which has been published by 3GPP. It is emphasized by 3GPP that to evaluate the actual coverage area, coverage probability should be taken into account in relation to the quality of service (QoS) definitions. However, coverage probability is not considered in all of the existing measurement methods. Hence, the developed measure turns out to be more effective than them as shown from the analysis and simulation results. Based on the developed measure, energy efficiency of Round Robin (RR) and Maximum SINR (MSINR) scheduling strategies for fractional frequency reuse (FFR) Schemes in orthogonal frequency division multiple access (OFDMA) Cellular Networks was investigated through closed-form expressions. The optimal power threshold of a base station (BS) and the optimal distance threshold of a cell were obtained from the results and the optimal distance threshold of MSINR is higher than that of RR while the optimal power threshold is not affected by scheduling strategies. Simulation also demonstrates that energy efficiency increases and the optimal distance threshold decreases with the number of users. However, the number of users has little impact on the optimal power threshold.