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IEEE COMMUNICATIONS SURVEYS & TUTORIALS, VOL. 13, NO. 4, FOURTH QUARTER 2011

Green Cellular Networks: A Survey, Some Research
Issues and Challenges
Ziaul Hasan, Student Member, IEEE, Hamidreza Boostanimehr, Student Member, IEEE, and
Vijay K. Bhargava, Fellow, IEEE

Abstract—Energy efficiency in cellular networks is a growing
concern for cellular operators to not only maintainprofitability,
but also to reduce the overall environment effects. This emerging
trend of achieving energy efficiency in cellular networks is
motivating the standardization authorities and network operators
to continuously explore future technologies in order to bring
improvements in the entire network infrastructure. In this article,
we present a brief survey of methods to improve the powerefficiency of cellular networks, explore some research issues and
challenges and suggest some techniques to enable an energy
efficient or “green” cellular network. Since base stations consume
a maximum portion of the total energy used in a cellular system,
we will first provide a comprehensive survey on techniques to
obtain energy savings in base stations. Next, we discuss how
heterogenous networkdeployment based on micro, pico and
femtocells can be used to achieve this goal. Since cognitive
radio and cooperative relaying are undisputed future technologies
in this regard, we propose a research vision to make these
technologies more energy efficient. Lastly, we explore some
broader perspectives in realizing a “green” cellular network
technology.
Index Terms—Green communication, energyefficient networks, efficiency metrics, microcells, picocells, femtocells, cognitive radio, cooperative relaying.

I. I NTRODUCTION

D

URING the last decade, there has been tremendous
growth in cellular networks market. The number of
subscribers and the demand for cellular traffic has escalated
astronomically. With the introduction of Android and iPhone
devices, use of ebook readers such as iPadand Kindle and
the success of social networking giants such as Facebook, the
demand for cellular data traffic has also grown significantly in
recent years. Hence, mobile operators find meeting these new
demands in wireless cellular networks inevitable, while they
have to keep their costs minimum.
Such unprecedented growth in cellular industry has pushed
the limits of energy consumption inwireless networks. There
are currently more than 4 million base stations (BSs) serving
mobile users, each consuming an average of 25MWh per year.
The number of BSs in developing regions are expected to
almost double by 2012 as shown in Fig. 1. Information and
Communication Technology (ICT) already represents around
2% of total carbon emissions (of which mobile networks
represent about 0.2%),and this is expected to increase every
year. In addition to the environmental aspects, energy costs

Manuscript received 18 February 2011; revised 1 September 2011.
Z. Hasan, H. Boostanimehr, and V. K. Bhargava are with the Department
of Electrical and Computer Engineering, University of British Columbia,
Vancouver, Canada (e-mail: {ziaulh, gauravbs, vijayb}@ece.ubc.ca).
Digital ObjectIdentifier 10.1109/SURV.2011.092311.00031

also represent a significant portion of network operators’
overall expenditures (OPEX). While the BSs connected to
electrical grid may cost approximately 3000$ per year to
operate, the off-grid BSs in remote areas generally run on
diesel power generators and may cost ten times more.
The rising energy costs and carbon footprint of operating
cellularnetworks have led to an emerging trend of addressing
energy-efficiency amongst the network operators and regulatory bodies such as 3GPP and ITU [4], [5]. This trend
has stimulated the interest of researchers in an innovative
new research area called “green cellular networks”. In this
regard, the European Commission has recently started new
projects within its seventh Framework Programme to...