Abstract
Energy efficiency (EE) and spectral efficiency (SE) have become the key performance indicators for wireless communication systems. In this paper, EE and SE, efficiency metrics, of a digital communication system with M-QAM modulation technique are introduced. The upper bounds on the efficiency metrics over generalized-K fading channel are derived in closed form. These efficiency metrics are analyzed for several generalized-K channel parameters and constellation size M. The effect of roll-off bandwidth factor on the efficiency metrics is also investigated. It is observed that the efficiency metrics are degraded by the nature of the fading channel. Thus, enhancing technique for SE and EE is proposed which is based on employing a higher/lower modulation level M to achieve a maximum EE in specific regions of signal to noise ratio (SNR) while maintaining a certain QoS. The proposed technique improves the efficiency metrics for a wide operating range of SNR; however, results in increased system complexity.