Joint relay assignment and adaptive modulation for energy-efficient cellular networks

Energy efficient operation of cellular systems becomes a core design goal for economic and environment-friendly network operation. Several studies have shown that the energy consumed in base stations represents 60-80% of the energy consumption in cellular networks. In this paper, we develop an optimization framework that exploits several energy efficient techniques including switching power modes of base stations, Adaptive Modulation (AM), and the use of relays. Our main objective is to reduce both, transmitted and circuit power, subject to satisfying the quality of service constraints. To accommodate the complexity of the target problem, we further propose two sub-optimal algorithms, minimum power heuristic (MPH) and minimum relays heuristic (MRH). The simulation results show that energy saving merits of our proposed schemes can be up to 80%.