基于能量检测的协作频谱感知技术研究

发布时间：2018-01-12 13:06

本文关键词：基于能量检测的协作频谱感知技术研究　出处：《解放军信息工程大学》2014年硕士论文　论文类型：学位论文

【摘要】：作为能缓解频谱资源短缺和利用率低下之间矛盾最具潜力的一项技术,认知无线电(Cognitive Radio,CR)近年来引起了广泛关注,它允许次用户(Secondary User,SU)在不给主用户(Primary User,PU)带来有害干扰的前提下动态接入空闲频段,因而可以提高频谱利用率。频谱感知是认知无线电技术执行的基础,其实质即为监测目标频段的主用户存在与否。鉴于单个次用户的频谱感知,例如能量检测,循环平稳特征检测和匹配滤波器检测等,其结果往往受阴影、多径衰落和噪声不确定性等影响而性能较差,学者提出了协作频谱感知(Cooperative Spectrum Sensing,CSS)技术来克服这些问题。然而在带来诸多好处的同时,协作频谱感知也引入了新的感知开销,包括控制信道、感知时延和上传能耗等。为此,本文以基于能量检测的协作频谱感知技术为对象,以提高协作感知性能和降低感知开销为目标,提出了以下解决方案:首先,针对平坦瑞利衰落信道下的协作频谱感知,提出了一种基于有限状态马尔科夫信道(Finite State Markov Channel,FSMC)的用户选择机制。通过引用一阶FSMC模型刻画衰落信道的缓慢变化,设计了次用户依据当前状态在感知和休眠之间的切换规则,并根据信道状态参数的获知与否给出了两种实现方案。研究表明:所提机制能保证各次用户尽可能地在高信噪比时参与感知而在低信噪比时进入休眠状态,动态实现了用户选择的目的,同时提高了协作感知性能和降低了感知开销。其次,针对协作频谱感知中上传时隙存在较多空闲的问题,设计了一种新的帧结构。在所设计的帧结构中,当一个次用户上传信息时,后面的次用户继续执行本地感知直至轮到其上传时才停止。分别针对恒虚警率(Constant False Alarm Rate,CFAR)和恒检测率(Constant Detection Rate,CDR)两种需求,研究了AND准则和OR准则下的次用户最优调度策略问题,并讨论了该帧结构带来的感知性能增益。研究表明:所设计的帧结构由于合理地将一半的空闲上传时隙用于本地感知,因而可以在不增加感知时延的前提下有效改善协作频谱感知性能。然后,针对次用户能量受限的协作频谱感知过程,提出了一种新的删除机制,核心思想是各次用户仅当感知结果与其前一次不同时才向融合中心发送一个指示信号,否则不发送。对比分析了基于所提删除机制的协作频谱感知中的上传能耗,并以限制对主用户的干扰为约束条件,对感知周期进行了优化。研究表明,所提机制可以在不造成任何感知性能损失的前提下有效降低次用户的上传能耗。此外,当上传信道非理想时,对所提机制还给出了一种改进方案,以保证其可行性。最后,在传统K/N融合准则的基础上提出了一种序贯决策融合机制,通过序贯地接收本地决策结果,融合中心可以不必接收所有决策信息就能做出全局决策。证明了该机制中的协作频谱感知性能与接收所有本地决策的传统协作频谱感知性能一致,还分析了融合中心所需接收决策的平均个数,并给出了AND准则和OR准则下的闭式解。研究表明,所提机制可以在不牺牲协作感知性能的前提下使得融合中心所需接收决策的平均个数明显降低,从而有效节约次用户上传能耗。此外,还考虑了将该机制与所提的删除机制进行联合设计,进一步降低了次用户的上传能耗。
[Abstract]:As can ease the shortage of spectrum resources and low utilization rate of the contradictions between the most potential of a technology, cognitive radio (Cognitive Radio, CR) in recent years has aroused widespread concern, it allows secondary users (Secondary, User, SU) in to the main user (Primary User, PU) with harmful interference under the premise of dynamic free access frequency, so it can improve the utilization of the spectrum. Spectrum sensing is the cognitive basis of radio technology implementation, which is the main user monitoring target band exists or not. In view of the single user spectrum sensing, such as energy detection, cyclostationary feature detection and matched filter detection, the result is often affected by the shadow. The influence of multipath fading and noise uncertainty and poor performance, scholars have proposed cooperative spectrum sensing (Cooperative Spectrum, Sensing, CSS) technology to overcome these problems. However, in the same benefits When the cooperative spectrum sensing also introduced a new sensing overhead, including control channel, sensing delay and energy consumption. Therefore this paper upload, the cooperative spectrum sensing technology based on energy detection as the object, in order to improve the performance of cooperative sensing and reduce perceived cost, the paper proposes the following solutions: first, for flat Rayleigh fading collaboration the channel spectrum sensing, proposes a finite state Markoff (Finite State Markov channel based on Channel, FSMC) user selection mechanism. By citing the first-order FSMC model to describe the fading channel changes slowly, designed according to the current state of the secondary users in the perception and dormancy switching between rules, and to know the channel state parameters and not give two schemes. The study shows that the proposed mechanism can guarantee the user as much as possible in the high SNR in perception in low SNR. In the resting state, the dynamic implementation of user selection, and also improves the performance of cooperative sensing and reduce the sensing overhead. Secondly, for the upload slot in cooperative spectrum sensing, there are more idle problem, designed a new frame structure. The frame structure design, when a user to upload information time, the user behind the continued implementation of the local perception until its turn upload to stop. According to the constant false alarm rate (Constant False Alarm Rate, CFAR) and the constant detection rate (Constant Detection Rate, CDR) two kinds of needs of AND quasi secondary user optimal scheduling strategy problem and OR criterion, and discuss the perception to bring the performance gain of the frame structure. The study shows that the design of the frame structure due to idle upload reasonably will be half of the time slot for local sensing, which can effectively improve the association in the premise of not increasing the perceived delay under the The performance of spectrum sensing. Then, according to the cooperative spectrum sensing user energy constrained process, put forward a new removal mechanism, the core idea is the user only when the sensing results and the first time to the fusion center sends an indication signal, otherwise not sent. Comparative analysis of the cooperative spectrum sensing provided in upload delete mechanism based on the energy consumption, and to limit the interference to primary users as constraint conditions, the perception of cycles were optimized. The results show that the proposed mechanism can effectively reduce the secondary users without causing any perceived loss of performance on energy consumption. In addition, while uploading a non ideal channel. The proposed mechanism gives an improved scheme to, to ensure its feasibility. Finally, based on the traditional K/N fusion rule proposed a sequential decision fusion mechanism, by sequentially receiving local decision results, The fusion center can not receive all the decision information can make a global decision. It is proved that the performance of cooperative spectrum sensing mechanism and receiving of all local decision-making of the traditional cooperative spectrum sensing performance, also analyzed the average number of fusion centers required for receiving decision, and gives a closed form solution of AND criterion and OR criterion under. The results show that the proposed mechanism can be without sacrificing the performance of collaborative awareness that the fusion center received the decision of average number is significantly reduced, thereby effectively saving energy consumption of secondary users upload. In addition, also considered the mechanism and proposed the deletion mechanism joint design, to further reduce the secondary users upload energy consumption.

【学位授予单位】：解放军信息工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN925

【相似文献】