认知无线电系统帧长参数优化

针对认知无线电系统帧结构设计中，如果数据发送时间设置不当可能导致干扰过大以及从用户接入机会丢失过多的问题。基于主用户活动服从指数分布的假设，推导建立了系统干扰模型和从用户接入机会丢失模型，该模型能以较大概率保证干扰时间及从用户接入丢失时间小于指定百分比值。在此基础上，提出了一个干扰和接入机会丢失受限的认知无线电系统帧长设计方案。实验结果表明，根据该方案设计的帧结构能够有效保证从用户的接入时间、较高的感知效率及较低的干扰率。

Optimizing frame duration parameter for cognitive radio systems

In the frame structure design of cognitive ratio systems, if the data sending time is set unreasonably, it is possible for secondary users to suffer much interference and the lost access opportunity. Under the exponentially distributed assumption based on the primary user activity, an interference model and a lost access opportunity model for secondary users are derived. The models ensure that the interference time and the lost access time are less than a specified percentage with a high probability. Then a theoretical framework about frame duration is developed to limit the interference and lost access opportunity ratio. Simulation results show that the frame structure developed in such a way can effectively ensure the secondary user’s access time, the higher sensing efficiency and lower interference rates.