Abstract—This paper proposes intra-operator dynamic spectrum access, i.e., dynamic spectrum access by an operator’s networks of its available spectrum bands, as a means to improve power efficiency. It is based around four areas of interest: (i) dynamically moving users into particularly active bands from other bands to allow radio network equipment in those other bands to be switched off when possible, (ii) the dynamic sharing of spectrum in order to take advantage of better propagation bands and reduce necessary transmission power, (iii) the sharing of spectrum to allow channel bandwidths to be increased thus allowing transmission power to be significantly decreased, and (iv) the better hierarchical management of spectrum in cases where different types of cells coexist. Numerical results show a significant potential for such spectrum management solutions to reduce power consumption for the operator by some 50% or more, with further potential saving if there is a lower correlation in traffic loads among the operator’s networks/frequencies. It is noted that although the main objective of this paper is power saving, the concepts presented can also be used for other purposes, such as to increase achievable capacity. Index Terms—green communications, dynamic spectrum access I. INTRODUCTION ECENT developments, both from regulatory and technical perspectives, allow freer use of spectrum (see, e.g., [1], [2], [3]). Moreover, in present and future contexts, it is widely expected that communications operators will own or have access to an increasingly wide range of spectrum bands, of very different frequencies and physical characteristics [4]. These developments, occurring in tandem, will in many cases lead to the situation where operators, within certain constraints (e.g., transmission power mask, perhaps implied interference, etc.), will be able to utilize their range of spectrum bands for whichever technologies they see fit. There is clear evidence emerging that carbon emissions must be significantly cut to maintain the viability of the planet Earth for human habitation [5]. Due to the inefficiencies of various components, carbon emissions associated with mobile communications can be quite significant, and, like all other technologies, it is necessary to reduce these emissions by as much as practically possible [6]. One of the most obvious means of reducing carbon emissions associated with mobile communications is lowering operational power consumption; this can also significantly reduce operational expenditure, being beneficial to operators from financial as well as “corporate responsibility” perspectives. Furthermore, some means of power consumption reduction, such as minimizing necessary transmissions power to achieve a service, might be seen by some (perhaps misguided) members of society as beneficial in other ways, such as to human health. This paper investigates dynamic spectrum access of the range of spectrum bands available to the operator, the objective of which, within the Green Radio Core 5 program of the UK’s Virtual Centre of Excellence in Mobile and Personal Communications, is to reduce necessary power consumption in providing services. In addition to the very significant power savings through such spectrum flexibility, this concept also offers various alternative benefits, such as vastly improved achievable capacity for the mobile operator. With the above-mentioned objectives in mind, this paper is structured as follows. In the next section, the power saving concepts that are leveraged are explained. Section III investigates aspects of the performances of the proposed schemes, showing significant potential for power consumption reduction. Finally, Section IV concludes this paper. II. POWER-SAVING SPECTRUM MANAGEMENT CONCEPTS The methods proposed in this paper to save power for the operator are illustrated in Figure 1. They are comprised of four categories: (i) moving users into particularly active bands from other bands, through the sharing of those active spectrum bands, to allow radio network equipment operating in the other bands to be switched off or put into stand-by mode when possible (Figure 1(a)), (ii) the dynamic sharing of spectrum to better take advantage of favorable propagation bands in order to reduce necessary transmission power, by moving users, or indeed even radio systems or parts of systems, to the better propagation bands when they are underused (Figure 1(b)), (iii) the dynamic sharing of spectrum to facilitate channel bandwidths being increased thus allowing transmission power to be significantly decreased according to Shannon (and various other) capacity formulas (Figure 1(c)), and last but not least, (iv) the better dynamic hierarchical management of spectrum, considering shadowing characteristics, in cases where different types of cells coexist (i.e., macro-, micro-, pico- and femto-cells—see Figure 1(d)). Note that various Green Spectrum Management for Mobile Operators Oliver Holland, Vasilis Friderikos, and A. Hamid Aghvami Centre for Telecommunications Research King’s College London Strand, London WC2R 2LS, UK {oliver.holland, vasilis.friderikos, hamid.aghvami}@kcl.ac.uk R IEEE Globecom 2010 Workshop on Green Communications 978-1-4244-8864-3/10/$26.00 ©2010 IEEE 1493