中文摘要：

在认知无线电的研究中，认知用户SU以怎样的访问模式共享主用户PU的空闲信道。是一个值得探讨的问题。假定PU信道的状态变化为泊松分布，SU在物理层使用OFDMA调制技术。比较了随机和最优两种信道选择策略对SU用户有效数据传输率的影响，并研究了这两种策略下SU数据传输率的解析表达式。依据这两种策略的规则和流程进行了相应的计算机仿真，分析了仿真图的变化趋势。结果表明这两种策略在主用户整个频谱空间信道数一定的情况下，将视SU接入信道数的多少而各有优势。

英文摘要：

The research of the access strategy when SU shares PUs＇ free channels is a vital problem. Random and priority channel selection methods are described when PU＇ s channel state alternation is assumed to conform to Poisson Process and SU uses the OFDMA modulation in its physical layer. SU＇ s valid data transmission rate is expressed in analytics and used as the performance measurement to compare the two channel selection methods. Also the simulation is devised according to the access model and its results are analyzed. The results show that these two selection methods have their own advantages depending on the channel numbers that would be occupied by SU.