Energy efficiency for wireless relay systems

Climate change has been an important international agenda these days and will be more important in the future. A number of climate groups have been working on to reduce CO2 emissions. A climate group (called GeSI) has identified that information and communications technology (ICT) sectors can play a key role in reducing CO2 emissions by 15% in Smart 2020 report [1]. To reduce CO2 emissions, it is also important to provide energy efficient solutions in wireless communications. In this chapter, we discuss energy efficiency for wireless relay systems. Energy efficiency can be measured by the energy consumed to transmit one bit over wireless channels. Depending on transmission schemes and system configurations, the energy efficiency can be different and this measure helps choose a better scheme or system for information transmissions. We will focus on wireless relay systems and analyze their energy efficiency in terms of energy and delay tradeoff (EDT). The notion of EDT plays a crucial role in deciding energy efficient transmission schemes or systems with delay constraints as quality of service (QoS) constraints