ABSTRACT
Two key characteristics of wireless communications that greatly impact system design and performance are 1) the randomly-varying channel conditions and 2) limited energy resources. In wireless systems, the power of the received signal fluctuates randomly over time and distance due to multipath fading, mobility, and changing environment. These random changes in the received signal strength lead to variations in the instantaneous data rate that can be supported by the channel. In addition, mobile wireless systems can only be equipped with limited energy resources, and hence energy efficient operation is a crucial requirement in most mobile applications. Also, with emerging applications in wireless ad-hoc and wireless sensor networks, energy-efficient operation is becoming a vital issue, especially when the replenishment of energy resources is not easy. Finally, there has been a new surge of interest in green communications in order to reduce the carbon footprint of communication systems and lower the energy costs. In summary, energy efficiency is a critical concern in wireless systems.
