Abstract-We consider a combined sleeping and censoring scheme for energy-efficient spectrum sensing in cognitive sensor networks. We analyze the detection performance of this scheme by theoretically deriving the global probabilities of detection and false-alarm. Our goal is to minimize the energy consumption incurred in distributed sensing, given constraints on the global probabilities of detection and false-alarm, by optimally designing the sleeping rate and the censoring thresholds. Using specific transceiver models for sensors based on IEEE 802.15.4/ZigBee, we show the energy savings achieved under an optimum choice of the design parameters.
I. INTRODUCTIONThe family of wireless networks -sensor networks, personal area networks, local area networks, cellular networks etc has seen tremendous growth recently, resulting in demand for radio spectrum. Traditionally, radio spectrum allocation has been based on exclusive, licensed use of portions of spectrum to wireless systems. This has resulted in a perceived dearth of spectrum available for use for newer wireless networks and applications. Radio spectrum measurements [13] however indicate that large portions of spectrum licensed to wireless systems remain under-utilized. Consequently there is a growing interest in unlicensed use of empty portions in order to improve spectrum utilization [3], [5], [17]. A promising approach for such secondary spectrum access is the use of cognitive radios. A cognitive radio can alter its radio transmission parameters autonomously based on active monitoring of spectrum in order to access spectrum on a secondary basis while coexisting with licensed systems or other unlicensed systems.In this paper, we consider a cognitive sensor network that performs spectrum sensing in order to determine empty radio channels and limits its transmissions on channels that are found vacant in order to reduce harmful interference to licensed systems. Our study is motivated by recent developments in regulatory and standardization bodies aimed at permitting the use of portable devices and low-power sensors to operate on a secondary basis in VHF-UHF bands licensed to television broadcasting systems. In this context, reliable spectrum sensing that is energy efficient is critical.The cognitive sensor network comprises of a fusion center (FC) and a number of cognitive sensors that carry out sensing