Date Added: Apr 2011
Conventional design of wireless networks mainly focuses on system capacity and Spectral Efficiency (SE). As Green Radio (GR) becomes an inevitable trend, energy-efficient design in wireless networks is becoming more and more important. In this paper, the fundamental relation between Energy Efficiency (EE) and SE in downlink Orthogonal Frequency Division Multiple Access (OFDMA) networks is addressed. The authors first set up a general EE-SE tradeoff framework, where the overall EE, SE and peruser Quality-of-Service (QoS) are all considered, and prove that EE is strictly quasi-concave in SE. They also find a tight upper bound and a tight lower bound on the EE-SE curve for general scenarios, which reflect the actual EE-SE relation.