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考虑在认知无线电系统中,次用户正确检测的情况下,主用户与次用户发生传输冲突的情况。引入排队论思想,以M/M/1模型描述主用户的出现模式,在此基础上,综合考虑传输时长、检测概率以及传输冲突等情况,构建频谱利用率与传输时间长度的函数关系式,并通过理论推导证明了,满足一定条件下,传输时间的定义域内频谱利用率的最大值点存在。通过仿真对最大值的存在情况进行了验证,并通过分析发现,仿真所设条件下,传输冲突所带来的频谱利用率损失大于20%,应在系统设计过程中予以充分考虑。
Consider the case of transmission collisions between the primary user and the secondary user in the cognitive radio system when the secondary user detects correctly. The idea of queuing theory is introduced to describe the mode of appearance of primary users by using M / M / 1 model. On this basis, considering the transmission duration, detection probability and transmission conflict, a functional relation between spectrum utilization and transmission duration is constructed. The theoretical derivation proves that the maximum point of spectrum utilization within the definition of transmission time under certain conditions exists. Through the simulation, we verify the existence of the maximum value, and find that under the conditions of simulation, the spectrum utilization loss caused by transmission collisions is more than 20% and should be fully considered in the system design process.