Efficient remote radio head switching scheme in cloud radio access network: A load balancing perspective

Abstract

Cloud radio access network (C-RAN) is deemed as a promising architecture to meet the exponentially increasing traffic demand in mobile networks, where baseband processing is separated from remote radio heads (RRHs) and performed in a centralized baseband unit (BBU) pool. However, the densely deployed RRHs, as well as the passive optical network which provides high capacity backhauls between the RRHs and the BBU pool, consume a large amount of energy. In this paper, we propose efficient RRH switching schemes to achieve a tradeoff between the system energy saving and the load balance among the RRHs in the C-RAN. We first develop an approximation algorithm to address the intractable user association problem for a given set of RRHs, based on which we introduce efficient local search algorithms to perform RRH selection procedure, which can reduce the load fairness index of the C-RAN by controlling the active/inactive state of each RRH. We also discuss the handover signalling overhead issue and introduce an adaptive trigger mechanism to avoid switching on/off too many RRHs simultaneously so as to keep the signalling overhead of the C-RAN below an acceptable level. Numerical results demonstrate that the proposed RRH switching schemes can improve the system performance of the C-RAN significantly. Moreover, our proposal sheds light on how to design effective and efficient handover schemes for next generation mobile networks.