Multiple daily base station switch-offs in cellular networks

In this paper we study base station sleep modes, which are today considered a viable approach to improve the energy efficiency of cellular access networks, by reducing power consumption in periods of low traffic. When some base stations are switched off, radio coverage and service provisioning are taken care of by the base stations that remain active, so as to guarantee that service is available over the whole area at all times. This is a realistic assumption in the case of the dense base station layouts of urban areas, which consume most of the network energy. We develop simple analytical models that allow optimal base station switch-off times to be identified as a function of the daily traffic pattern, in the cases in which either just one switch- off per day is possible (bringing the network from a high- power, fully-operational configuration, to a low-power reduced configuration), or several switch-offs per day are permitted (progressively reducing the number of active base stations and the network power). We first assume that any fraction of base stations can be switched off, then we consider a realistic case. We quantify the percentage of energy which can be saved with base station sleep modes, proving that it can be close to 50% of the total network energy consumption.