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Optimizing performance of cooperative sensing for increased spectrum utilization in dynamic cognitive radio systems

Cognitive radios (CR) that sense spectrum usage and adjust their transmissions to meet specified spectral constraints have been proposed for use in future generations of wireless systems to enable dynamic access to the frequency spectrum. In cooperative spectrum sensing, a fusion center (FC) receives local sensing information from multiple CRs and combines it to provide better decision on the spectrum use. In dynamic scenarios where occurrence of spectrum opportunities is intermittent and their durations have limited time, the performance of cooperative sensing is affected by the size of the sensing window at local CR and by the time delay introduced by the FC for processing of the local sensing information. In this paper we study how these parameters influence the performance of cooperative sensing by introducing a new metric which incorporates both probability of detection along and spectrum utilization, and which can be used to optimize the performance of cooperative sensing. Numerical performance studies in dynamic scenarios where the PU activity changes in time and/or is affected by fading are also presented.