In this article, we analyze the packet transmission time in spectrum sharing systems where a secondary user (SU)\r\nsimultaneously accesses the spectrum licensed to primary users (PUs). In particular, under the assumption of an\r\nindependent identical distributed Rayleigh block fading channel, we investigate the effect of the peak interference\r\npower constraint imposed by multiple PUs on the packet transmission time of the SU. Utilizing the concept of\r\ntimeout, exact closed-form expressions of outage probability and average packet transmission time of the SU are\r\nderived. In addition, employing the characteristics of the M/G/1 queuing model, the impact of the number of PUs\r\nand their peak interference power constraint on the stable transmission condition and the average waiting time of\r\npackets at the SU are examined. Moreover, we then extend the analysis for point-to-point to point-to-multipoint\r\ncommunications allowing for multiple SUs and derive the related closed-form expressions for outage probability\r\nand successful transmission probability for the best channel condition. Numerical results are provided to\r\ncorroborate our theoretical results and to illustrate applications of the derived closed-form expressions for\r\nperformance evaluation of cognitive radio networks.
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