Neighbor discovery is one of them in the distributed cognitive systems. Usually, the spectrum for cognitive radio is dynamic, so there is no fixed access channel for the CR users. If there is also no a pre-settled control center, neighbor discovery becomes more complicated. 由于认知无线电技术的频谱是动态的,因此不可能预先为认知无线电系统下的用户分配固定无线接入频谱,在没有固定接入信道,同时也没有控制中心状况下,邻近终端发现问题变得复杂起来。