Survey on cluster-based routing protocols for cognitive radio sensor networks

Routing protocols could achieve efficient convergecast transmission of sensed data in cognitive radio sensor network (CRSN),and it is of vital importance for the whole network performance.In particular,cluster-based routing protocols could further lower routing selection complexity and improve scalability.Therefore,an overview of cluster-based routing protocols for CRSN was provided.Firstly,after a brief introduction to the concept and advantages of clustering in CRSN,the major factors concerning clustering algorithm design were pointed out.Secondly,the challenges faced by routing protocol design in CRSN and basic design principles were explored.Thirdly,the previous work of cluster-based routing protocols for CRSN was systematically analyzed and summarized.Finally,issues that require urgent solutions and future research directions were suggested.     

认知无线电网络中基于信任的安全路由模型

针对认知无线电网络中路由受到的选择性转发攻击,提出一种基于信任的安全路由模型。通过监视节点的数据转发行为,构建节点的信任以识别恶意节点。基于路由选择必须同频谱分配紧密结合的特点,在路由发现阶段,请求信息中封装节点的可用频谱机会并避免发送给恶意节点。在路由选择阶段,利用节点信任构建可用路径信任,结合延时度量进行路由决定。同时,根据节点的信任划分对其服务请求采取不同的响应,对非可信节点的恶意行为采取更严厉的惩罚,从而激励节点在路由中的合作。仿真结果及分析表明,在选择性转发攻击下,该模型较已有模型在网络吞吐率、端到端延迟方面都有较好的表现。     

Design of optimum criterion for opportunistic multi-hop routing in cognitive radio networks

The instability of operational channels on cognitive radio networks (CRNs), which is due to the stochastic behavior of primary users (PUs), has increased the complexity of the design of the optimal routing criterion (ORC) in CRNs. The exploitation of available opportunities in CRNs, such as the channel diversity, as well as alternative routes provided by the intermediate nodes belonging to routes (internal backup routes) in the route-cost (or weight) determination, complicate the ORC design. In this paper, to cover the channel diversity, the CRN is modeled as a multigraph in which the weight of each edge is determined according to the behavior of PU senders and the protection of PU receivers. Then, an ORC for CRNs, which is referred to as the stability probability of communication between the source node and the destination node (SPC_SD), is proposed. SPC_SD, which is based on the obtained model, internal backup routes, and probability theory, calculates the precise probability of communication stability between the source and destination. The performance evaluation is conducted using simulations, and the results show that the end-to-end performance improved significantly.     

A decision tree cognitive routing scheme for cognitive radio mesh networks

Routing in a cognitive radio network operating in a dynamic environment is a complex decision problem. Diversity in the number of available spectrum bands and their stability, in addition to the secondary users' heterogeneities, affect the consequence of the routing decision. We use a decision theory framework to model the problem of routing under uncertainties involved in a cognitive radio network. A utility function is designed to capture the effect of spectrum measurement, fluctuation of bandwidth availability, and path quality. A node cognitively decides its best candidate among its neighbors by utilizing a decision tree. Each branch of the tree is quantified by the utility function and a posterior probability distribution that predicts the suitability of available neighbors. In decision tree cognitive routing (DTCR), nodes learn their operational environment and adapt their decision‐making accordingly. We compared our scheme with the optimal performance in a highly dynamic environment and local coordination‐based routing and spectrum assignment protocol [1]. Our results show that the DTCR tends to perform near optimum. It easily adapts to environmental dynamics. Copyright © 2013 John Wiley & Sons, Ltd.     

认知无线电中的频谱接入技术

认知无线电是一种基于软件无线电的智能通信系统,它能够认知周围环境,并能通过一定的方法相应地改变某些工作参数来实时地适应环境,从而达到提高频谱利用率、缓解频谱资源紧张的目的.授权频段的频谱利用问题是认知无线电实现的关键技术之一.研究了授权频段的两种频谱利用方法:动态频谱接入和基于动态频谱接入模型之一的机会频谱接入.     

一种适合于认知无线传感网络的路由算法

路由设计是认知无线传感网络（CRSNs）中目前受到较少关注却很重要的一个领域。在CRSN中,由于主用户（PUs）对可用信道资源的随机占用行为,路由算法的设计不仅需要考虑如何延长网络寿命,还要考虑网络内数据传输的可靠性。本文研究了具有频谱可感知特性,且对能量消耗敏感的 CRSN路由问题,揭示了 CRSN路由问题的独特性,并将这类问题表述为在能量约束和变化的网络拓扑环境下的网络寿命优化问题。在回顾传感器网络的典型算法之后,提出一种新的路由度量来克服 CRSN的路由设计挑战,即认知能量度量（CE）。在此基础上,提出一种分布式路由算法以延长网络寿命,同时提高数据传输的可靠性。仿真结果表明,所提路由算法能很好地适应 CRSN中可用信道资源及网络拓扑的随机变化。     

Routing for cognitive radio networks consisting of opportunistic links

Cognitive radio (CR) has been considered a key technology to enhance overall spectrum utilization by opportunistic transmissions in CR transmitter–receiver link(s). However, CRs must form a cognitive radio network (CRN) so that the messages can be forwarded from source to destination, on top of a number of opportunistic links from co‐existing multi‐radio systems. Unfortunately, appropriate routing in CRN of coexisting multi‐radio systems remains an open problem. We explore the fundamental behaviors of CR links to conclude three major challenges, and thus decompose general CRN into cognitive radio relay network (CRRN), CR uplink relay network, CR downlink relay network, and tunneling (or core) network. Due to extremely dynamic nature of CR links, traditional routing to maintain end‐to‐end routing table for ad hoc networks is not feasible. We locally build up one‐step forward table at each CR to proceed based on spectrum sensing to determine trend of paths from source to destination, while primary systems (PSs) follow original ways to forward packets like tunneling. From simulations over ad hoc with infrastructure network topology and random network topology, we demonstrate such simple routing concept known as CRN local on‐demand (CLOD) routing to be realistic at reasonable routing delay to route packets through. Copyright © 2009 John Wiley & Sons, Ltd.     

QoS multicast routing in cognitive radio ad hoc networks

In this paper, we discussed the issues of QoS multicast routing in cognitive radio ad hoc networks. The problem of our concern was: given a cognitive radio ad hoc network and a QoS multicast request, how to find a multicast tree so that the total bandwidth consumption of the multicast is minimized while the QoS requirements are met. We proposed two methods to solve it. One is a two‐phase method. In this method, we first employed a minimal spanning tree‐based algorithm to construct a multicast tree and then proposed a slot assignment algorithm to assign timeslots to the tree links such that the bandwidth consumption of the tree is minimized. The other is an integrated method that considers the multicast routing together with the slot assignment. Extensive simulations were conducted to show the performance of our proposed methods. Copyright © 2011 John Wiley & Sons, Ltd.     

基于局部拓扑控制的认知网络路由方法

针对认知网络研究一种融合主、次用户多因素优化的局部拓扑控制和路由方法。该方法综合考虑主用户频谱使用情况以及次用户对主用户干扰影响,预测认知链路的稳定性,结合链路功耗,定义一种联合链路代价,提出链路代价最小的局部认知拓扑控制路由 (LCTCR)算法,优化网络拓扑,并在优化后的拓扑上进行网络路由的选择。算法分析和仿真实验证明,在进行认知网络路径选择时,链路功耗和链路稳定性均为重要参数,需联合优化以保证选择更优的实际路由。     

分布式认知无线电网络多路径路由协议研究综述

为了深入研究分布式认知无线电网络的多路径路由问题,阐述了分布式认知无线电网络基本特征以及多路径路由设计面临的问题与挑战。分布式认知无线电网络多路径路由采用多路径并行传输,可有效降低传输时延、增加网络吞吐量与传输可靠性、实现网络负载均衡。根据路由优化目标不同,从吞吐量、带宽、干扰、时延、负载均衡和路由发现六方面对近年来多路径路由协议的主要研究成果进行了分类,然后逐类对多路径路由协议进行了分析和讨论,最后分别从分布式认知无线电网络基本特征的适应性与多路径路由协议特征两个方面进行了比较,并展望了分布式认知无线电网络多路径路由协议需进一步研究的方向。     

An efficient and adaptive channel handover procedure for cognitive radio networks

In designing cognitive radio systems, one of the most critical issues is handling the channel handover process (CHP). The CHP consists of spectrum sensing, spectrum decision, negotiation on the common control channel, and adjustment of frequency and modulation settings, and such, it can be a time‐consuming process. Consequently, initiating the CHP after each detected user activity (UA) can decrease the aggregate spectrum utilization. To alleviate this problem, we introduce a novel handover strategy to find the optimal trade‐off between the durations of the CHP and UAs. With the use this model, secondary users (SUs) track only local information on their current data channel to make the decision to initiate the CHP or to wait for the termination of the ongoing UA. The system adapts to the dynamic conditions of the data channels and reduces the frequency of handovers to increase throughput and decrease access delay. We give analytical utilization bounds for SUs and also compare the performance of our model to those of other channel handover strategies by using extensive simulations. Our results for channels with heterogeneous loads and dynamic environments show that this model can clearly decrease the frequency of handover and consequently increase the aggregate SU utilization. Copyright © 2013 John Wiley & Sons, Ltd.     

Securing cognitive radio networks

Cognitive radio is a promising technology aiming to improve the utilization of the radio electromagnetic spectrum. A cognitive radio device uses general purpose computer processors that run radio applications software to perform signal processing. The use of this software enables the device to sense and understand its environment and actively change its mode of operation based on its observations. Unfortunately, this solution entails new security challenges. Our objective in this paper is to analyze the security issues of the main recent developments and architectures of cognitive radio networks. We present vulnerabilities inherent to those systems, identify novel types of abuse, classify attacks, and analyze their impact on the operation of cognitive radio‐based systems. Moreover, we discuss and propose security solutions to mitigate such threats. Copyright © 2010 John Wiley & Sons, Ltd.     

Primary user supported routing protocol for cognitive radio ad hoc networks in search of higher throughput

A routing protocol for cognitive radio ad hoc networks (CRAHNs), namely, primary user supported routing (PSR) is demonstrated in this research. Unlike existing routing protocols for CRAHN, where routing of cognitive users (CUs) is accomplished within CUs, in this proposed protocol, some of the primary users (PUs) support CUs to communicate, by forwarding CU packets. This service provided by PU is of voluntary nature. However, such assistance shall be provided by the PUs, only when they are idle, thereby, preserving the principles of cognitive radio networks (CRNs), which indicates that the operation of PU should not be disturbed by the CU activities. The proposed work is compared with cognitive ad hoc on-demand distance vector (CAODV) protocol. The performance parameters considered are routing overhead, rate of loss of packets, and e2e packet delay. PSR outperforms CAODV in all these performance parameters. There has been on average 26.25% improvement in routing overhead, 34.12% decrease in loss, and 27.01% improvement in e2e delivery in the proposed PSR.     

Exploring the impact of social properties on routing in cognitive radio networks

In this paper, we study the social properties, including community, friendship, and individual selfishness of cognitive radio networks and analyze the effect of these social properties on the performance of routing protocols. We first introduce the concept of cooperation willingness considering social relations and individual selfishness. Then, we model the impact of cooperation willingness on the routing performance in cognitive radio networks. After that, we perform extensive simulations to evaluate the accuracy of our model. The simulation results show that our model matched the simulation results well. Finally, our results suggest that community members, friends, and nodes with lower individual selfishness should be selected in the forwarding routes.     

基于最优停止的认知无线网络下行频谱接入算法

为有效平衡认知无线网络中次用户系统中接入信道的感知时间和信道总的吞吐量之间的矛盾,提出了一种只对部分信道进行感知的频谱接入策略,联合总的感知信道数和各条信道的感知时间进行优化,并通过最优停止算法求解,在最大化节省感知时间的同时,取得较大的平均吞吐量。与HC-MAC(Hardware Constrained- Media Access Control)算法的仿真分析对比表明,该算法在相同给定条件下感知时间更短,吞吐量更大,具有明显的优势。     

基于改进遗传算法的认知无线传感网动态频谱分配方案

将认知无线电中的动态频谱分配技术应用在无线传感网中,针对工作在ISM(industrial,scientific and medical)频段的无线传感网面临的频谱资源紧缺问题,提出一种基于改进自适应遗传算法的动态频谱分配方案.该算法以图论着色模型为基础,以最大带宽收益和最小切换频率为目标函数,在交叉和变异过程中采用自适应交叉概率和变异概率代替固定的交叉概率和变异概率.仿真结果表明,与传统遗传算法和颜色敏感图论着色算法相比,该算法可以实现提高频谱利用率、降低能量消耗的预期目标.     

认知网络中一种基于频谱安全态势感知的路由方案

从构建准确的频谱态势图,实现频率资源充分利用的角度出发,针对目前在构建频谱态势图时没有考虑恶意用户(Malicious User,MU)存在的情况,结合克里金(Kriging)插值法估计空域内频谱干扰态势,通过地理位置检测方案识别MU,从而构建更准确、更安全的频谱态势图,并将其用于端到端的路由协议中。仿真结果表明,该方案能构建完整的频谱态势图,平均误差仅为0.106 dBm,能准确识别恶意用户,识别率高于80%;并且通过识别MU,在基于频谱态势图的路由过程中,可以减少路由跳数,增加可用频谱空间。     

Joint resource reconfiguration and robust routing for cognitive radio networks: a robust optimization approach

Cognitive radio (CR) networks comprise a number of spectrum agile nodes with the capability of spectrum detection. Applying techniques of spectrum sharing in CR networks can achieve the efficient utilization of network resources. Usually, data rates of user sessions are time varied because of the dynamic behaviors of CR networks. It is expected that the occurrence of link outage should be avoided and incorporated into the routing design under conditions of increasingly crowded spectrum. This paper proposes an integral framework, which considers these two correlated schemes (resource reconfiguration and robust routing) simultaneously. For that, the resource reconfiguration scheme is developed for the efficient usage of network resources and aims at reducing the occupancy of licensed bands. The link outage, resulting from random session rate, is confined within an acceptable range by using strategy of virtual ‘network portfolio’. A robust optimization approach is proposed to guarantee reliable data transmission among possible interfering links. Both these two items (resource reconfiguration and robust routing) are formulated in a framework of cross‐layer optimization. The evolutionary process of CR network states is provided in simulations, where the results show that the joint design proposal can achieve the least interferences among different licensed users while realizing robust routing. Copyright © 2013 John Wiley & Sons, Ltd.     

认知无线网络中基于主用户行为的联合路由和信道分配算法

针对认知无线网络中主用户行为将导致频谱瞬时变化而影响路由稳定性的问题,提出了一种基于主用户行为的路由和信道联合分配算法。该算法通过采用呼叫模型对主用户行为建模,并根据动态源路由协议的路由寻找机制,在目的节点等待多个路由请求分组后选择受主用户行为影响最小的路由,然后沿着所选定路径的反方向传送路由回复分组并完成信道分配。理论分析证明了算法中的链路平均持续时间期望与主用户活动概率成反比且具有与网络节点数成正比的计算复杂度。仿真结果表明,该算法具有比Gymkhana路由方案更高的分组投递率和更低的平均分组时延。     

Spectrum sensing scheduling for group spectrum sharing in cognitive radio networks

This paper addresses the issues on spectrum sharing in a cognitive radio network consisting of a primary user and a group of cognitive users. Each cognitive user may occupy a non‐overlapped sub‐band of the primary spectrum, but it needs to perform spectrum sensing independently before accessing the sub‐band. To reduce the complexity of spectrum sensing and thus energy consumption, this paper proposes a scheduled spectrum sensing scheme. First, we consider a single spectrum sensing scenario where only one cognitive user is elected to perform spectrum sensing, and then it broadcasts its sensing results to the other cognitive users. The scheduled spectrum sensing scheme works in both network‐centric and user‐centric ways. Next, the scheduled spectrum sensing scheme is further generalized to work in a multiple spectrum sensing scenario. The results show the effectiveness of the proposed schemes compared with the traditional schemes where all cognitive users may perform spectrum sensing at the same time. Copyright © 2010 John Wiley & Sons, Ltd.