Green Radio

This chapter gives a comprehensive introduction to state‐of‐the‐art energy‐efficient communications, focusing on the physical (PHY) and medium access control (MAC) layers of wireless communication systems. The PHY layer consists of RF circuits, modulation, power control, and channel coding units, and so on and delivers data transmission as reliably as possible. The MAC layer ensures network‐wide efficient resource management while maintaining quality of service (QoS) requirements of individual users. As wireless is a shared communication medium, with wireless communications, device energy consumption is not only affected by the designs of different layers of the point‐to‐point communicating link but also by the interactions of all links in the network. A system approach is therefore necessary for energy‐efficient wireless communications system design. The focus of this chapter is on wireless system design, analysis, and optimization emphasizing energy efficiency enhancement while meeting given performance requirements. Since the design of all protocol layers impact energy consumption, this chapter introduces cross‐layer energy‐efficient techniques to reduce redundant message transfers and the associated energy consumption. Cross‐layer techniques exploit interactions between different layers to significantly improve energy efficiency and adaptability to service, traffic, and environment dynamics.