Energy efficient baseband unit aggregation in cloud radio and optical access networks

A cloud radio access network enabled by optical transport technology has been recently proposed as a next-generation mobile access network. It separates the legacy base station into remote radio heads (RRHs) and centralized baseband unit (BBU) pools. "Any-to-any" connections between RRHs and BBUs can be realized through a flexible optical fronthaul network. In this paper, we focus on the energy consumption of a BBU pool under a tidal traffic scenario, and an energy-efficient BBU aggregation is proposed by dynamically sleeping and awaking BBU cards. We discuss a BBU capacity model and transform BBU aggregation into an evolved 2D bin-packing problem. An integer linear programming formulation and two heuristic algorithms are developed to minimize the number of active BBU cards. Simulation comparisons are performed among different cell sites (i.e., macro cell, micro cell, pico cell, and heterogeneous cell) and network coverage. Numerical evaluations show that BBU aggregation can achieve significant energy savings, especially for a small cell scenario.