Date Added: Feb 2011
With explosive growth of high-data-rate applications, more and more energy is consumed in wireless networks to guarantee Quality-of-Service (QoS). Therefore, energy-efficient communications have been paid increasing attention under the background of limited energy resource and environmental-friendly transmission behaviors. In this paper, basic concepts of energy-efficient communications are first introduced and then existing fundamental works and advanced techniques for Energy Efficiency (EE) are summarized, including information-theoretic analysis, Orthogonal Frequency Division Multiple Access (OFDMA) networks, Multiple-Input Multiple-Output (MIMO) techniques, relay transmission, and resource allocation for signaling. Some valuable topics on energy-efficient design are also identified for future research.