Analysis of a green-cell breathing technique in a hybrid access network environment

Energy efficiency in cellular networks is a major issue for current and future mobile networks. Several approaches have been proposed for this purpose: the component approach, the radio resource management (RRM) algorithms, the cell topology adaptation mechanisms, the hybrid network architectures, the cognitive radio approach and others. However, it is rare to find proposals where two or more of these approaches are combined in order to obtain a better energy efficiency. In this paper we combine the cell breathing technique, a cell topology adaptation mechanism, with a hybrid network approach composed of small and large cell layers. Our scenario includes the possibility of users being blocked by the femto-layer due to Closed-Subscriber Groups (CSG) access policies, a concept defined in 3GPP standards but not very discussed so far in the literature. By adding the cell breathing to the macro layer, we have two ways of traffic redistribution in order to offload and deactivate a larger number of Macro-BSs achieving to take the most of benefits from the hybrid cellular infrastructure. The described proposal is compared with other related mechanisms found in the literature. Our results lead to interesting conclusions for shortterm practical implementations.