Energy efficiency gains in interference-limited heterogeneous cellular mobile radio networks with random micro site deployment

Abstract

Abstract-Energy efficiency considerations recently gained attention due to ecological aspects, that is to say lowering CO2 emissions and reducing energy consumption. Furthermore, it is important to assess energy efficiency improvements from an operator's point of view, since energy costs are increasing and providing ubiquitous high speed mobile access may scale up the operators' operational expenditure. One of two promising approaches to enhance a network's operation regarding energy efficiency is to utilize smaller micro cells within one large macro cell. Another approach is to regard macro base stations as coverage providers for areas in between micro cells, while reducing their maximum transmit powers to a minimum. In this paper we investigate on the energy efficiency of a heterogeneous OFDM-based mobile network in the downlink taking into account the co-channel interference based on varying traffic demand per area. Furthermore, we carry out an assessment of potential energy savings of the two approaches mentioned above. For a sufficiently large traffic demand, increasing deployment densitiy through additional micro sites may maximize a network's energy efficiency. In that case the network operates at a load of less than 50 %. Moreover, a further gain of energy efficiency of about 20 % can be achieved due to macro site transmit power reduction while still providing coverage. I. INTRODUCTIONOver the last few years a significant change in the use of the internet could be recognized. It not only provides information but also serves as a main medium for communication, i. e., instant messaging, email, voice over internet protocol (VoIP), video streams and video calls. The consumers' mobility and further technical improvements lead to an annual increase of the amount of transferred data in mobile communications systems of about 400 % to 800 % [1]. This induces an increase in energy consumption of mobile communications systems of about 16 % to 20 % per year, which corresponds to a doubling every four or five years [2]. 80 % of electricity consumption of a mobile radio communication network originates in its radio access network, i. e., its base stations (BS); the consumption by base stations and its backhaul networks amounts to 60 billion kWh corresponding to 60 million households [2]. In conjunction with high consumption of energy also a large amount of CO 2 emissions can be observed. ICT systems had a share of 2 % of global CO 2 emissions already in 2007, which is equivalent to the total CO 2 emissions caused by the international air traffic [2]. Due to these aspects it is important to address the mobile systems' energy efficiency. Since the largest part of power consumed by a network can be

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