Energy Efficient Base Stations

With the explosion of mobile Internet applications and the subsequent exponential increase of wireless data traffic, the energy consumption of cellular networks has rapidly focused caught the attention of the entire telecommunication community: industrials, operators, academics and government institutions. One of the first actions taken has been to monitor and understand where and by which cellular equipments the energy is consumed. Several studies have been conducted in parallel (e.g. [1, 2, 3]), and while the figures may slightly differs, all come to the same conclusion: whatever the technology is used (UMTS, HSPA, LTE), the major part of the energy (~50-60%) of a mobile network is consumed by the Radio Access Network (RAN), and in particular by the set of Base Stations, followed by the core network (~30%), and data centers (~10%). The impact of the Base Stations comes form from the combination of a high the power consumption of the equipment itself (up to 1000-1500 Watts for a nowadays macro base station) multiplied by the number of deployed sites in a commercial network (e.g. more then 12000 in UK for a single operator [3]). In order to effectively improve the energy efficiency of the future mobile networks, it is thus important to focus the attention on the Base Station. This chapter aims a providing a survey on the Base Stations functions and architectures, their energy consumption at component level, their possible improvements and the major problems that must be faced in order to make such improvement effective. When possible, examples from the 3GPP LTE technology are provided, in order to help the reader to map generic concepts to real-life networks. However, it is not the intention of this chapter to present in detail the LTE technology. The reader interested in an extensive presentation of this technology can refer to [4].