Cooperative Sleep and Power Allocation for Energy Saving in Dense Small Cell Networks

Energy consumption has become a crucial issue due to the large-scale deployment of small base stations (SBSs) in dense small cell networks (DSCNs). In this paper, a joint optimization problem involving sleep mode in subframes and power allocation to minimize the DSCN energy consumption while guaranteeing users' rate requirements is formulated as a mixed integer nonlinear programming. To address this problem, we propose a cooperative sleep and power allocation approach by decomposing it into two subproblems. First, we derive the optimum number of active subframes for each SBS and present a centralized heuristic coalition formation algorithm to manage SBSs to form coalitions. In such a case, SBSs can transmit data in active subframes and sleep in others. We then obtain the SBSs' optimum transmit power in the active subframes relying on a distributed price-based power allocation algorithm. System-level simulation results show that our proposed cooperative scheme can yield significant performance gains in terms of energy saving compared with the maximum power allocation and the non-cooperative power allocation (NCPA) approaches. In addition, the effects of target rates on coalition size and energy consumption are also analyzed.