Keynote Speech V by Ender Ayanoglu

Conventional cellular wireless networks were designed with the purpose of providing high throughput for the user and high capacity for the service provider, without any provisions of energy efficiency. As a result, these networks have an enormous Carbon footprint. For example, only in the United States, the Carbon footprint of the cellular wireless industry is equal to that of about 3/4 million cars. In addition, the cellular network is highly inefficient and therefore a large part of the energy dissipated is wasted. In this presentation, we first analyze the energy dissipation in cellular wireless networks and point to sources of major inefficiency. We also discuss how much more mobile traffic is expected to increase so that this Carbon footprint will increase tremendously more. We then discuss potential sources of improvement at the physical layer as well as at higher layers of the communication protocol hierarchy. For the physical layer, we discuss new modulation formats and new device technologies and what they may bring in terms of energy efficiency gain. At higher layers, considering that most of the energy inefficiency in cellular wireless networks is at the base stations, we discuss multi-tier networks and point to the potential of exploiting mobility patterns in order to use base station energy judiciously. We discuss link adaptation and point to why energy efficiency, and not power efficiency should be pursued and what it means for the choice of link rates. We show how much gain is possible by energy-efficient link rate adaptation. We describe the gains due to the exploitation of nonuniform traffic in space, relays and cooperation, device-to-device communications, multiple antenna technques, and in particular coordinated multipoint and massive MIMO, sleeping modes for the base stations, the techniques of cell breathing and cell zooming, the energy trap problem for the mobile terminals, and the potential approaches for video that provide energy efficiency. We also review several survey papers and books published on this topic. By a consideration of the combination of all potential gains, we conclude that an improvement in energy consumption in cellular wireless networks by orders of magnitude is possible.