Bandwidth and power efficiency analysis of fading communication link

Bandwidth and power are the major radio resources of a wireless communication system. Designing an efficient wireless communication system requires trade-off between these resources. In this context, definitions of radio resource efficiencies are given in terms of bandwidth efficiency, bit/s/Hz, and power efficiency, bit/Thermal Noise Energy Unit, for an arbitrary communication system. These efficiencies are analyzed and discussed over Rayleigh and Nakagami fading channels for M-QAM. Investigation shows that the efficiency metrics are degraded by the channel effects. Also, it is evident that each M-QAM level attains highest power efficiency in a specific range of signal to noise ratio (SNR). Thus, an adaptive transmission technique is proposed and analyzed for enhancing resource efficiencies based on number of levels in M-QAM to achieve maximum power efficiency in specific SNR regions. It is shown that efficiency metrics can be significantly improved by using the proposed technique for a broad range of signal to noise ratio, even when fading is severe.