Optimum Sensing Bandwidth for Energy-Efficient Cognitive Radio Communications

Abstract

Cognitive radio may discover more idle (unoccupied) spectrum by spending more power for spectrum sensing, while the transmission power can be reduced by using more spectrum (bandwidth). We analyze the tradeoff between the sensing power and transmission power in achieving a given throughput in cognitive radio networks and examine the optimum sensing bandwidth that maximizes the energy efficiency, defined as the number of bits that can be successfully delivered per unit of energy (bits per Joule). Maximizing the energy efficiency enables economical green wireless networks and reduces CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emission. The effect of the sensing time, the number of cognitive radios, and the primary user spectrum occupancy rate on the optimum sensing bandwidth is examined in cooperative spectrum sensing.