Spectral- and energy-efficient transmission over frequency-orthogonal channels

Spectral efficiency and energy efficiency are important design criteria for green communications systems and networks. In this paper, spectral efficiency and energy efficiency are addressed for wireless transmission over frequency-orthogonal channels. The maximum sum rate is used in measuring spectral- and energy-efficiency. Towards achieving the maximum efficiency, two separated optimization problems are formulated. With a fixed transmit power allocation, the optimal bandwidth assignment is given in closed form. Then, a procedure is provided to determine the total bandwidth for maximum spectral efficiency. With a fixed bandwidth assignment, the optimal transmit power allocation is given in closed form. Then, a procedure is provided to determine the total transmit power for maximum energy efficiency. Practical data traffic is discussed that affects the maximum efficiency result. Simulation results validate the transmission approaches over frequency-orthogonal channels that achieve the best spectral efficiency and energy efficiency, respectively.