主次用户传输冲突下认知系统感知时间优化

Optimization Sensing Slot under Transmission Collision of Primary User and Secondary User in Cognitive Radio System

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。

In the cognitive radio system, that the primary user（PU） has collision with the secondary user（SU） when the secondary user（SU） was detected properly was considered. The queuing theory was introduced and the PU＇s appearance pattern was described by M/M/1 model. Considering the length of the transmitting slot, detection probability and transmitting collision, the function of spectrum usage and transmitting time were established based on the PU＇s appearance pattern. The existence of the maximum value of spectrum usage in the definition domain of the transmitting time was proved by theoretical derivation in some condition. The simulation results provide support to the existence of the maximum value. Furthermore, the loss of spectrum usage caused by transmitting collision is more than 20%, which should be considered during the system design procedure.