In this paper, we propose a semi-distributed cooperative spectrum sen sing(SDCSS) and channel access framework for multi-channel cognitive radio networks(CRNs). In particular, we c onsider a SDCSS scheme where secondary users (SUs)perform sensing and exchange sensing outcomes with ea ch other to locatespectrum holes. In addition, we devise the p -persistent CSMA-based cognitiveMAC protocol integrating the SDCSS to enable efficient spectrum sharing amongSUs. We then perform throughput analysis and develop an algorithm to determinethe spectrum sensing and access parameters to maximize the throughput for agiven allocation of channel sensing sets. Moreover, we consider the spectrumsensing set optimization problem for SUs to maxim ize the overall systemthroughput. We present both exhaustive search and low-complexity greedyalgorithms to determine the sensing sets for SUs and analyze their complexity.We also show how our design and analysis can be extended to consider reportingerrors. Finally, extensive numerical results are presented to demonstrate thesig nificant performance gain of our optimized design framework with respect tonon-optimized designs as well as the imp acts of different protocol parameterson the throughput performance.
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