认知中继网络频谱感知与资源分配研究

发布时间：2018-11-01 15:14

【摘要】：随着无线通信技术的不断发展,人们对频谱资源的需求日益增加。传统的固定频谱分配策略能够避免系统之间的干扰,但对频谱资源的占用具有不完全性,极易造成频谱资源的浪费。认知无线电技术能够实现无线频谱资源的共享和利用,解决了频谱资源匮乏以及频谱资源利用不足之间的矛盾。另一方面,协作中继技术利用分集增益,能够有效提高无线网络系统的容量、传输可靠性以及增加覆盖率。认知无线网络是在认知无线电技术基础上发展起来的一种具有认知能力的网络,通过引入协作中继技术,认知无线网络能够获得更好的系统性能和更高的频谱利用率,因此,面向协作中继的认知无线网络——认知中继网络,已成为无线通信领域的研究热点。由于与授权网络系统共享频谱资源,认知中继网络首先需要进行频谱感知发现可用的频谱资源,然后,根据频谱感知的结果自适应调整自身参数,确定最佳的资源分配方案进行频谱接入。本论文围绕认知中继网络系统中的协作频谱感知和联合资源分配问题展开研究,以协作中继作为主要技术手段,重点解决了认知中继网络系统中两个基本问题:1)研究精确可靠的频谱感知算法,为认知中继网络系统提供尽可能多的可靠频谱接入机会;2)研究高效的联合资源分配算法,以便认知用户能够合理利用有限资源,从而提高接入频谱的利用效率,增加认知中继网络系统的容量。论文主要创新性贡献包括:首先,为了克服信道衰落对频谱感知性能的不利影响,论文提出了两种基于虚拟MIMO技术的带外控制信道协作频谱感知算法,所提算法提高了协作频谱感知的准确性和可靠性,能够为认知中继网络提供更多可靠的频谱接入机会。1)提出了一种基于高效空时编码的协作频谱感知算法,算法利用高效空时编码和协作中继技术增加系统分集增益,能够降低感知信号传输误码率,有效提升协作频谱感知的性能;2)考虑到协作认知用户的动态变化和认知用户感知可靠性之间的差异,提出了一种基于随机空时编码的加权协作频谱感知算法,算法采用随机空时编码克服信道衰落对感知性能造成的影响,利用感知可靠性加权融合准则增强高可靠性感知信号的判决权重,在提高协作频谱感知性能的同时能够适应认知用户数量的动态变化。其次,为了克服带外控制信道协作频谱感知对信道资源的额外需求,论文提出了一种基于选择中继的带内控制信道协作频谱感知算法,在保证协作频谱感知性能的同时能够有效节约信道资源,提高授权频谱利用率以及减小信道管理复杂度。该算法采用了一种基于选择中继的信号传输机制避免初始感知结果上报过程中可能对授权用户造成的干扰,利用感知可靠性加权融合准则区分不同认知用户的感知可靠性,提高协作频谱感知的性能。同时,算法给出了最优能量感知门限选择机制,保证授权用户通信QoS的同时最大限度利用授权频谱资源。所提算法通过联合考虑感知和报告两个阶段,研究了感知开销对协作频谱感知性能的影响,分析表明,对于预设目标检测概率而言,存在唯一的感知开销使得频谱感知的虚警概率最小。然后,在协作频谱感知基础之上,为了充分利用频谱接入机会,针对多约束环境对网络系统性能的影响,论文研究了AF-OFDM认知多中继网络中的联合资源分配问题,提出了三种联合子载波匹配、功率分配和最佳中继选择的资源分配算法,以提高频谱资源的利用效率,提升认知中继网络系统的容量。1)提出了一种基于对偶理论的分布式资源分配算法以获取联合资源分配问题的近似最优解;2)提出了一种快速联合资源分配算法,这种算法具有很低的计算复杂度,比较适合硬件条件有限、性能要求不高的应用场景;3)为了平衡算法性能和复杂度之间的冲突,提出了一种两阶段高效联合资源分配算法,这种算法解决了对偶算法和快速算法的缺点,在获得稳定且较低计算复杂度的同时,算法性能接近于近似最优解。最后,考虑到中继协议的差异,论文研究了DF-OFDM认知多中继网络中的联合资源分配问题,提出了两种联合资源分配算法以适应复杂的应用环境,提高网络系统的容量。1)考虑到算法计算复杂度在应用中可能对系统实现带来的不利影响,以获取较低的计算复杂度为目标,提出了一种快速联合资源分配算法,快速算法能够在不对系统性能造成严重衰减的前提下,大大降低算法计算复杂度;2)由于快速算法以追求计算复杂度最小为目标,次优的功率分配机制以及子载波分配顺序都会对系统性能造成一定的影响,为了克服这些问题,提出了一种高效的联合资源分配算法,高效算法克服了快速算法中发射功率分配机制和子载波分配顺序的不利影响,在计算复杂度和性能之间获得了合理的平衡。
[Abstract]:With the development of wireless communication technology, people's demand for spectrum resources is increasing. The traditional fixed spectrum allocation strategy can avoid the interference between the systems, but the occupation of the spectrum resources is incomplete, and the waste of spectrum resources can be easily caused. the cognitive radio technology can realize the sharing and utilization of radio spectrum resources, and solves the contradiction between the lack of spectrum resources and the insufficient utilization of spectrum resources. On the other hand, cooperative relay technology utilizes diversity gain to effectively improve the capacity of wireless network system, transmission reliability and increase coverage rate. The cognitive wireless network is a network with cognitive ability developed on the basis of cognitive radio technology. By introducing cooperative relay technology, the cognitive wireless network can obtain better system performance and higher frequency spectrum utilization rate, therefore, A cooperative relay-oriented cognitive radio network _ cognitive relay network has become a hot spot in the field of wireless communication. Because the spectrum resource is shared with the authorized network system, the cognitive relay network firstly needs to carry out spectrum sensing to discover available spectrum resources, and then adaptively adjusts the self parameters according to the result of spectrum perception, and determines the best resource allocation scheme to carry out frequency spectrum access. This paper researches on cooperative spectrum sensing and joint resource allocation problem in cognitive relay network system, and takes cooperative relay as the main technical means, mainly solves the two basic problems in the cognitive relay network system: 1) the accurate and reliable spectrum sensing algorithm is researched, Providing as many reliable spectrum access opportunities as possible for the cognitive relay network system; 2) researching the efficient joint resource allocation algorithm so that the cognitive users can reasonably utilize the limited resources, thus improving the utilization efficiency of the access spectrum and increasing the capacity of the cognitive relay network system. Firstly, in order to overcome the adverse effect of channel fading on spectrum sensing performance, two kinds of external control channel cooperative spectrum sensing algorithm based on virtual MIMO technology are proposed, and the proposed algorithm improves the accuracy and reliability of cooperative spectrum sensing. it is possible to provide more reliable spectrum access opportunities for the cognitive relay network. 1) a cooperative spectrum sensing algorithm based on efficient empty time coding is proposed, and 2) considering the difference between the dynamic change of the cooperative cognitive user and the perceived reliability of the cognitive user, a weighted cooperative spectrum sensing algorithm based on random air time coding is proposed, The algorithm adopts random space coding to overcome the influence of channel fading on perceived performance, enhances the decision weight of high reliability sensing signal by utilizing perceptual reliability weighted fusion criterion, and can adapt to the dynamic change of the number of cognitive users while improving the performance of cooperative spectrum sensing. secondly, in order to overcome the additional requirement of the external control channel cooperative spectrum perception to channel resources, a cooperative spectrum sensing algorithm based on a selective relay is proposed, which can effectively save the channel resources while ensuring the cooperative spectrum sensing performance, improve that utilization of authorized spectrum and reduce the complexity of channel management. The algorithm adopts a signal transmission mechanism based on the selective relay to avoid the interference that may be caused by the authorized user during the reporting process of the initial perception result, and utilizes the perceptual reliability weighted fusion criterion to distinguish the perceived reliability of different cognitive users and improve the performance of cooperative spectrum sensing. At the same time, the optimal energy-sensing threshold selection mechanism is given to ensure the maximum utilization of authorized spectrum resources while the user is authorized to communicate with QoS. The proposed algorithm studies the effect of perceived overhead on the perceived performance of cooperative spectrum by considering both the perception and the reporting period. The analysis shows that there is a unique perception overhead for the detection probability of the preset target, so that the probability of the spectrum-aware virtual police is the least. Then, on the basis of cooperative spectrum perception, in order to make full use of spectrum access opportunity, in order to influence the performance of network system with multi-constraint environment, the problem of joint resource allocation in AF-OFDM cognitive multi-relay network is studied, and three joint sub-carriers matching are proposed. In order to improve the utilization efficiency of spectrum resources and improve the capacity of cognitive relay network system, a distributed resource allocation algorithm based on dual theory is proposed to obtain approximate optimal solution of joint resource allocation problem. 2) a fast joint resource allocation algorithm is proposed, which has low computational complexity and is suitable for application scenarios with limited hardware conditions and high performance requirements; and 3) in order to balance the conflict between performance and complexity of the algorithm, A two-stage efficient joint resource allocation algorithm is proposed, which solves the defect of dual algorithm and fast algorithm, and the algorithm performance is close to the approximate optimal solution while obtaining stable and low computational complexity. Finally, considering the difference of relay protocol, the problem of joint resource allocation in DF-OFDM cognitive multi-relay network is studied, and two joint resource allocation algorithms are proposed to suit the complex application environment. increasing the capacity of the network system. 1) taking into account that the computational complexity of the algorithm can adversely affect the implementation of the system in the application, and aiming at obtaining lower computational complexity, a fast joint resource allocation algorithm is proposed, the fast algorithm can greatly reduce the computational complexity of the algorithm without causing severe attenuation to the system performance, and 2) because the fast algorithm aims at the minimum computational complexity, In order to overcome these problems, an efficient joint resource allocation algorithm is proposed in order to overcome these problems. The efficient algorithm overcomes the adverse effects of the transmission power allocation mechanism and the sub-carrier allocation sequence in the fast algorithm, and obtains a reasonable balance between the computational complexity and the performance.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN925

【共引文献】