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1.
Recent research in the emerging field of cognitive radio (CR) has mainly focussed on spectrum sensing and sharing, that allow an opportunistic use of the vacant portions of the licensed frequency bands by the CR users. Efficiently leveraging this node level channel information in order to provide timely end-to-end delivery over the network is a key concern for CR based routing protocols. In addition, the primary users (PUs) of the licensed band affect the channels to varying extents, depending on the proportion of the transmission power that gets leaked into the adjacent channels. This also affects the geographical region, in which, the channel is rendered unusable for the CR users. In this paper, a geographic forwarding based SpEctrum Aware Routing protocol for Cognitive ad-Hoc networks (SEARCH), is proposed that (i) jointly undertakes path and channel selection to avoid regions of PU activity during route formation, (ii) adapts to the newly discovered and lost spectrum opportunity during route operation, and (iii) considers various cases of node mobility in a distributed environment by predictive Kalman filtering. Specifically, the optimal paths found by geographic forwarding on each channel are combined at the destination with an aim to minimize the hop count. By binding the route to regions found free of PU activity, rather than particular CR users, the effect of the PU activity is mitigated. To the best of our knowledge, SEARCH takes the first steps towards a completely decentralized, CR routing protocol for mobile ad-hoc networks and our approach is thoroughly evaluated through analytical formulations and simulation study.  相似文献   

2.
Cognitive Radio (CR), first proposed by Mitola, has the potential to improve spectrum utilization by allowing secondary transmission in licensed primary networks, as long as the secondary transmissions do not interfere with the operation of the primary users (PUs) in the primary network. Although it is fundamental to the viability of this burgeoning technology, security aspects of CR have so far received scant attention from researchers. Initial research on CR has largely focused on the issues of resource allocation, spectrum sensing and management while security considerations are often added as an afterthought. As a result, many proposed solutions for CR, have introduced significant security gaps, intensifying the effects of selfishness, inequity, unavailability, or even malicious behaviors. This has posed challenges to quality-of-service (QoS) provisioning in Cognitive Radio Network (CRN) in the face of various network attacks like node masquerading, packet mislabeling and deliberate packet dropping. Since existing routing protocols assume that nodes will forward packets in good faith, the presence of selfish nodes coupled with the dynamic behavior of PUs can lead to excessive packet losses, high delays or even the complete failure of routing protocols in secondary networks. In this paper, we propose a cross-layer Altruistic Differentiated Service Protocol (ADSP) for the dynamic CRNs to address the QoS provisioning issue in CRNs with selfish nodes coexistence. Simulation results demonstrate that the ADSP can achieve much better performance in terms of lower delay, higher throughput and better delivery ratio for the traffic originating from collaborative nodes compared to other cognitive routing protocols in the presence of selfish nodes.  相似文献   

3.
We propose a mobility assisted spectrum aware routing (MASAR) protocol for cognitive radio ad hoc networks (CRAHNs), providing robustness to primary user activity and node mobility. This protocol allows nodes to collect spectrum information during a spectrum management interval followed by a transmission period. Cognitive users discover next hops based on the collected spectrum and mobility information. Using a beaeonless mechanism, nodes obtain the mobility information and spectrum status of their neighbors. A geographical routing scheme is adopted to avoid performance degradation specially due to the mobility of the nodes and the activity of the primary users. Our scheme uses two approaches to find either short or stable routes. Since mobility metrics have a significant role in the selection of the next hop, both approaches use a reactive mobility update process assisted by mobility prediction to avoid location errors. MASAR protocol performance is investigated through simulations of different scenarios and compared with that of the most similar protocol, CAODV. The results indicate that MASAR can achieve significant reduction in control overhead as well as improved packet delivery in highly mobile networks.  相似文献   

4.
移动Ad Hoc网络多播路由协议的研究进展   总被引:3,自引:2,他引:3  
移动AdHoc网络是一个自组织、移动节点通过无线链路组成的动态拓扑变化的网络.由于网络规模小、无基础设施、构建迅速等特点,从而广泛用于紧急事件、军事和民用领域以及多媒体应用等.随着网络应用规模的增长,在移动AdHoc网络中支持多播路由成为网络领域中一类重要的研究课题.该文综述了移动AdHoc网络多播路由方面的一些最新工作,论述了设计移动AdHoc网络多播路由协议的特性、问题和技术,详细描述和比较了目前典型的移动AdHoc网络多播路由协议,为进一步的应用和研究提出了新的课题.  相似文献   

5.
Energy efficient routing and power control techniques in wireless ad hoc networks have drawn considerable research interests recently. In this paper, we address the problem of energy efficient reliable routing for wireless ad hoc networks in the presence of unreliable communication links or devices or lossy wireless link layers by integrating the power control techniques into the energy efficient routing. We consider both the case when the link layer implements a perfect reliability and the case when the reliability is implemented through the transport layer, e.g., TCP. We study the energy efficient unicast and multicast when the links are unreliable. Subsequently, we study how to perform power control (thus, controlling the reliability of each communication link) such that the unicast routings use the least power when the communication links are unreliable, while the power used by multicast is close to optimum. Extensive simulations have been conducted to study the power consumption, the end-to-end delay, and the network throughput of our proposed protocols compared with existing protocols.  相似文献   

6.
Recent advancements in wireless communication are creating a spectrum shortage problem on a daily basis. Recently, Cognitive Radio (CR), a novel technology, has attempted to minimize this problem by dynamically using the free spectrum in wireless communications and mobile computing. Cognitive radio networks (CRNs) can be formed using cognitive radios by extending the radio link features to network layer functions. The objective of CRN architecture is to improve the whole network operation to fulfil the user's demands anytime and anywhere, through accessing CRNs in a more efficient way, rather than by just linking spectral efficiency. CRNs are more flexible and exposed to wireless networks compared with other traditional radio networks. Hence, there are many security threats to CRNs, more so than other traditional radio environments. The unique characteristics of CRNs make security more challenging. Several crucial issues have not yet been investigated in the area of security for CRNs. A typical public key infrastructure (PKI) scheme which achieves secure routing and other purposes in typical ad hoc networks is not enough to guarantee the security of CRNs under limited communication and computation resources. However, there has been increasing research attention on security threats caused specifically by CR techniques and special characteristics of CR in CRNs. Therefore, in this research, a survey of CRNs and their architectures and security issues has been carried out in a broad way in this paper.  相似文献   

7.

Cognitive radio (CR) technology has been demonstrated as one of the key technologies that can provide the needed spectrum bands for supporting the emerging spectrum-hungry multimedia applications and services in next-generation wireless networks. Multicast routing technique plays a significant role in most of wireless networks that require multimedia data dissemination to a group of destinations through single-hop or multi-hop communication. Performing multimedia multicasting over CR networks can significantly improve the quality of multimedia transmissions by effectively exploiting the available spectrum, reducing network traffic and minimizing communication cost. An important challenge in this domain is how to perform a multi-cast transmissions over multiple hops in a dynamically varying CR environment while maintaining high-quality received video streaming to all multi-case CR receivers without affecting the performance of legacy primary radio networks (PRNs). In this paper, we investigate the problem of multicast multimedia streaming in multi-hop CR networks (CRNs). Specifically, we propose an intelligent multicast routing protocol for multi-hop ad hoc CRNs that can effectively support multimedia streaming. The proposed protocol consists of path selection and channel assignment phases for the different multi-cast receivers. It is based on the shortest path tree (SPT) that implements the expected transmission count metric (ETX). The channel selection is based on the ETX, which is a function of the probability of success (POS) over the different channels that depends on the channel-quality and availability. Simulation results verify the significant improvement achieved by the proposed protocol compared to other existing multicast routing protocols under different network conditions.

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8.
Cognitive radio refers to an intelligent radio with the capability of sensing the radio environment and dynamically reconfiguring the operating parameters. Recent research has focused on using cognitive radios in ad hoc environments. Spectrum sensing is the most important aspect of successful cognitive radio ad hoc network deployment to overcome spectrum scarcity. Multiple cognitive radio users can cooperate to sense the primary user and improve sensing performance. Cognitive radio ad hoc networks are dynamic in nature and have no central point for data fusion. In this paper, gradient-based fully distributed cooperative spectrum sensing in cognitive radio is proposed for ad hoc networks. The licensed band used for TV transmission is considered the primary user. The gradient field changes with the energy sensed by cognitive radios, and the gradient is calculated based on the components, which include energy sensed by secondary users and received from neighbors. The proposed scheme was evaluated from the perspective of reliable sensing, convergence time, and energy consumption. Simulation results demonstrated the effectiveness of the proposed scheme.  相似文献   

9.
In recent times, there have been many advances in the field of information theory and wireless ad hoc network technologies. Regarding information theory progression and its connection with wireless ad hoc networks, this study presents fundamental concepts related to the application of the state-of-the-art Network Coding (NC) within wireless ad hoc networks in the context of routing. To begin with, this paper briefly describes opportunistic routing and identifies differentiation between NC-aware and NC-based routing mechanisms in wireless ad hoc networks. However, our main focus is to provide a survey of available NC-aware routing protocols that make forwarding decisions based on the information of available coding opportunities across several routes within wireless ad hoc networks. The taxonomy and characteristics of various representative NC-aware routing protocols will also be discussed. In summary, we provide a comparison of available NC-aware routing schemes and conclude that NC-aware routing techniques have several advantages over traditional routing in terms of high throughput, high reliability, and lower delay in a wireless scenario. To the best of our knowledge, this work is the first that provides comprehensive discussion about NC-aware routing protocols.  相似文献   

10.
本文简要介绍了车载自组织网络和移动自组织网络中两个典型的路由协议:表驱动路由协议DSDV和按需路由协议AODV;还介绍了一个实用的移动模型,使仿真实验更加接近现实。在Linux下使用网络仿真工具NS2对这两个典型协议进行仿真,并对仿真结果进行分析比较和性能评价,得出:AODV和DSDV协议都不太适用于车辆自组织网络,所以设计适合车辆网路的协议是急需解决的问题。  相似文献   

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