基于簇的分布式认知无线电网络安全体系结构

针对认知无线电网络中出现的模仿主用户攻击和自私行为攻击问题,提出一种基于簇的分布式认知无线电网络安全体系结构.这种安全体系结构通过采用数据加密和认证等安全技术解决无线网络中原有的安全问题,通过在主用户基站与认知用户间使用Hash匹配技术可解决模仿主用户攻击问题,通过簇头向目的节点发送转发节点的可用频谱信息可解决自私行为攻击问题.由分析可知该安全体系结构是安全、高效和可行的.     

Efficient Power Allocation for Multiuser Cognitive Radio Networks

Cognitive radio has been recently considered as a flexible spectrum usage model to improve the spectrum efficiency. In this paper, we develop a new power allocation approach by geometric programming (GP) to realize the coexistence of a primary user (PU) and multiple cognitive users (CUs) in the same frequency band. The objective is to minimize the total power consumption of CUs while guaranteeing the not only protection of PU but also the quality of service (QoS) of multiple CUs, which is different from previous works. In order to facilitate the centralized computation, a distributed algorithm is developed to adaptively adjust the transmit power of each CU. Numerical results are provided to show the effectiveness of the proposed algorithm in power saving.     

认知无线电传感器网络中能量有效的感知策略

将认知无线电技术引入无线传感器网络(WSN),可以使传感器节点在不影响主用户正常通信的前提下,利用频谱空穴来满足自身的通信需求。虽然切换到合适的信道能够降低传输能耗,但是感知过程不可避免的带来一定的额外能耗,因此如何对频谱进行感知来降低节点的总能耗是一个至关重要的问题。在基于离散马尔可夫链的信道占用模型基础上,根据信道状态的n步转移概率,提出了一种由当前感知结果来决定下一次感知时刻的感知策略。仿真结果表明,相对传统无感知过程的WSN以及先感知后传输的策略,有效地降低了能耗。     

认知无线电网络中基于均方误差的预编码设计

基于认知无线电的概念,研究了一个多中继的认知无线电场景,设计了基站与中继的预编码矩阵,来最小化具有最大均方误差(MSE)的次用户的MSE值,同时保证主用户的MSE小于一定的阈值且中继的功率满足约束条件,将此优化问题转化为一个凸优化问题,并通过凸优化软件包来获得基站和中继预编码矩阵的最优数值解。最后,仿真结果验证了所提方案的有效性。     

PSHO-HF-PM: An Efficient Proactive Spectrum Handover Mechanism in Cognitive Radio Networks

In the paper, we develop an efficient proactive spectrum handover mechanism by using packet scheduling algorithm, called PSHO-HF-PM, to reduce unusable channel. It effectively integrates several mechanisms (hole filling and packet migration) to reduce the bandwidth fragment and support QoS. Its basic idea is in that a new packet is scheduled by migrating some packets to other channels if none of holes in any channels can accommodate it; otherwise repeating the above processes after random waiting time. Meanwhile under an effective data structure, such as the balanced binary search tree, its computational complexity will be \(O(2n\log n)\) at most. In the proposed packet scheduling algorithm, packet migration plays a key role in the improvement of bandwidth efficiency and QoS. We also evaluate the performance of total service time for proactive spectrum handover mechanism based on a Preemptive Resume Priority M/G/1 queuing network model. The performance analysis and simulation results show that it performs much better than other proactive and reactive handover mechanism in collision rate, total service time, packet loss probability and bandwidth fragment ratio.     

认知无线电网络中基于跨层设计的能效优化算法

为提高认知无线电网络中次用户节点的能量有效性,该文基于连续时间马尔科夫理论对次用户的频谱感知和接入过程进行联合建模,对影响次用户传输能效的主要因素进行了分析,提出了一种基于跨层设计的能量有效优化算法。该算法可有效减小主用户非时隙返回信道对次用户能量有效性的影响,并通过联合优化感知时间和接入概率,使次用户在感知性能和传输能效间实现了有效折衷。仿真结果表明,本文算法相对于仅考虑频谱感知或接入策略的单层优化算法,可使次用户的能量有效性得到较大提高。      

认知无线网络架构与关键技术研究

认知无线网络是一种开放性的智能网络,通过网络环境的学习分析,对网络状态进行规划、决策和响应。认知无线网络使网络从静态工作模式发展到动态自适应工作模式,从单一封闭式网络发展到异构融合网络,是解决网络容量受限,实现频谱高效利用和异构网络融合的有效途径之一。认知无线网络的相关研究在国家973项目的支持和项目组各单位的共同努力下取得了长远发展,主要讨论认知无线网络架构的理论模型、实现功能以及部署实现,然后分析了支撑架构的关键技术研究,主要包括多域主动认知方法、自主资源决策管理、无线自主传输机制以及体系结构适变技术等。     

合作认知无线网络中能效最优资源分配

针对能量受限的合作认知网络,该文研究在保证主用户服务质量要求下,认知用户能量效率最大化问题。认知用户利用信能同传技术接收主用户信号,并采用解码转发协议协助主用户通信。基于分式规划和引入辅助变量将原始非凸问题转换为凸优化问题进行求解,并提出一种迭代的资源分配算法。仿真结果表明,所提算法能够快速收敛于最优解。与能量合作方案相比,该文所采用方案能量效率显著提高,同时能更好地保证主用户服务质量要求。     

一种基于CR的无线通信侦察体系结构

在分析认知无线电思想的基础上,定义了基于认知无线电的无线通信侦察分析的概念,设计了一种基于认知无线电的无线通信侦察分析的体系结构,为无线通信侦察技术研究提供参考。     

一种改进的认知无线网络路由算法

在SEARCH路由协议中,如果当前路由处于前向避免区域,会造成频谱切换,影响网络拓扑,增加端到端延迟和能量消耗。提出基于地理位置和前向反馈的认知路由算法来解决这一问题。通过信息反馈,该算法能可靠地选择最佳下一跳路由;同时提出认知网络路由算法的评估方案。仿真表明,所提路由选择算法可以很好地降低端到端的延迟和能量消耗。     

Optimal Sensing and Transmission of Energy Efficient Cognitive Radio Networks

Wireless Personal Communications - The issue of spectrum scarcity can be alleviated by the cognitive radio technology with efficient spectrum sensing and allocation of free spectrum bands....     

Cognitive Radio Architecture Evolution

The radio research community has aggressively embraced cognitive radio for dynamic radio spectrum management to enhance spectrum usage, e.g., in ISM bands and as secondary users in unused TV bands, but the needs of the mobile wireless user have not been addressed as thoroughly on the question of high quality of information (QoI) as a function of place, time, and social setting (e.g. commuting, shopping, or in need of medical assistance). This paper considers the evolution of cognitive radio architecture (CRA) in the context of motivating use cases such as public safety and sentient spaces to characterize CRA with an interdisciplinary perspective where machine perception in visual, acoustic, speech, and natural language text domains provide cues to the automatic detection of stereotypical situations, enabling radio nodes to select from among radio bands and modes more intelligently and enabling cognitive wireless networks to deliver higher QoI within social and technical constraints, made more cost effective via embedded and distributed computational intelligence.     

Cooperative Communications for Cognitive Radio Networks

Cognitive radio is an exciting emerging technology that has the potential of dealing with the stringent requirement and scarcity of the radio spectrum. Such revolutionary and transforming technology represents a paradigm shift in the design of wireless systems, as it will allow the agile and efficient utilization of the radio spectrum by offering distributed terminals or radio cells the ability of radio sensing, self-adaptation, and dynamic spectrum sharing. Cooperative communications and networking is another new communication technology paradigm that allows distributed terminals in a wireless network to collaborate through some distributed transmission or signal processing so as to realize a new form of space diversity to combat the detrimental effects of fading channels. In this paper, we consider the application of these technologies to spectrum sensing and spectrum sharing. One of the most important challenges for cognitive radio systems is to identify the presence of primary (licensed) users over a wide range of spectrum at a particular time and specific geographic location. We consider the use of cooperative spectrum sensing in cognitive radio systems to enhance the reliability of detecting primary users. We shall describe spectrum sensing for cognitive radios and propose robust cooperative spectrum sensing techniques for a practical framework employing cognitive radios. We also investigate cooperative communications for spectrum sharing in a cognitive wireless relay network. To exploit the maximum spectrum opportunities, we present a cognitive space–time–frequency coding technique that can opportunistically adjust its coding structure by adapting itself to the dynamic spectrum environment.      

认知无线电网络中一种改进的传输层协议

在认知无线电网络中,传统的TCP协议无法适应认知用户周期性感知频谱、切换信道等特点,使得网络的传输性能大大降低。在TCP-Reno基础上提出了一种基于传输预判与慢启动门限值(Slow Start Threshold,SSThresh)的自适应调整的传输层协议———TCP-Cog,该协议通过预测下一个数据包的传输时延,调整发送端的发送,并通过预测切换信道的带宽调整SSThresh。通过在NS2工具中进行仿真,验证了TCP-Cog能够提高TCP的传输速率,降低重传率,提升传输性能。     

Efficient Spectrum Sensing with Minimum Transmission Delay in Cognitive Radio Networks

In cognitive radio (CR) networks, the secondary users (SUs) need to find idle channels via spectrum sensing for their transmission. In this paper, we study the problem of designing the sensing time to minimize the SU transmission delay under the condition of sufficient protection to primary users (PUs). Energy detection sensing scheme is used to prove that the formulated problem indeed has one optimal sensing time which yields the minimum SU transmission delay. Then, we propose a novel cooperative spectrum sensing (CSS) framework, in which one SU’s reporting time can be used for other SUs’ sensing. The analysis focuses on two fusion strategies: soft information fusion and hard information fusion. Under soft information fusion, it is proved that there exists one optimal sensing time that minimizes the SU transmission delay. Under hard information fusion, for time varying channels, the novel multi-slot CSS is derived. The performance of SU transmission delay is studied in both perfect and imperfect reporting channels. Some simple algorithms are derived to calculate the optimal sensing settings that minimize the SU transmission delay. Computer simulations show that fundamental improvement of delay performance can be obtained by the optimal sensing settings. In addition, the novel multi-slot CSS scheme shows a much lower transmission delay than CSS based on general frame structure.     

CRN中一种优化的数据传输方案

在认知无线电网络(CRN)中,如何有效地实现认知用户间快速可靠的数据传输是目前的研究热点。针对现有传输方案的不足,提出了一种优化的数据传输方案。在考虑节点发射功率和负载均衡的约束条件下,基于对认知用户间链路可靠性预测,联合频谱分配与按需路由策略实现认知用户数据的最优化传输。仿真实验表明,在减少路由重构次数的同时,较大地提高了系统的吞吐量。     

认知无线电网络中改进的拓扑控制算法

在对认知无线电网络进行信道分配时,网络的拓扑健壮性、对主用户的干扰和认知用户之间的干扰是衡量网络性能优劣的重要指标。文中在假设信道占用时间服从负指数分布的前提下,提出了一个权衡对主用户干扰和认知用户之间干扰的参数,并结合健壮的拓扑控制算法,给出了一种改进的拓扑控制算法。仿真结果表明,ITCA比CRTCA在网络吞吐量上有所增加,冲突率有所降低。     

非饱和认知无线电网络MAC协议设计

针对具有连续性接入需求的业务,论文融合时分多址接入技术和竞争窗口差分服务机制,提出了具有连续性保障的无线接入协议:CP-MAC(MAC with Continuity Provisioning)协议.通过对业务等级划分,保障了连续用户的接入概率.并基于Markov模型,给出了非饱和认知无线电网络的系统容量,接入时延和被阻塞概率的数学解析式.最后,通过与现存的MAC接入协议比较,CP-MAC协议在不降低系统容量的同时,提高了连续用户的接入概率,并降低了其接入时延.