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QoS-Aware Joint BBU-RRH Mapping and User Association in Cloud-RANs

Cloud radio access network (C-RAN) is a promising wireless network architecture that can reduce the energy consumption by the centralized cloud architecture and subsequently decrease the number of required traditional base station sites and the site support equipments. C-RAN consists of the baseband units (BBUs) and the remote radio heads (RRHs). BBUs are pooled in a central cloud, i.e., the BBU pool is to provide powerful computation and storage resources while RRHs are distributed across multiple sites to provide coverage and interact with user equipments. In order to exploit the benefits of C-RAN, each BBU can be actualized by a virtual machine, i.e., virtual BBU (VB). VBs can be initiated and shut down as needed to serve clusters of RRHs (i.e., many-to-one mapping between RRHs and BBUs). RRHs can be turned into the sleep mode to reduce the energy consumption. In this paper, we jointly optimize BBU-RRH mapping and user association with the objective to minimize the system cost incurred by the energy bill from RRHs and VB rentals under the constraint of user quality of service, which is formulated as an integer linear programming problem. Furthermore, we decompose the joint problem into two subproblems and design a time-efficient algorithm to solve the problem. Simulation results demonstrate that our proposed algorithm performs close to the optimal solutions obtained from CPLEX.