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In traditional networks special efforts are put to secure the perimeter with firewalls: particular routers that analyze and filter the traffic to separate zones with different levels of trust. In wireless multi-hop networks the perimeter is a concept extremely hard to identify, thus, it is much more effective to enforce control on the nodes that will route more traffic. But traffic filtering and traffic analysis are costly activities for the limited resources of mesh nodes, so a trade-off must be reached limiting the number of nodes that enforce them. This work shows how, using the OLSR protocol, the centrality of groups of nodes with reference to traffic can be estimated with high accuracy independently of the network topology or size. We also show how this approach greatly limits the impact of an attack to the network using a number of firewalls that is only a fraction of the available nodes. 相似文献
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Recent vehicular routing proposals use real-time road traffic density estimates to dynamically select forwarding paths. Estimating the traffic density in vehicular ad hoc networks requires the transmission of additional dedicated messages increasing the communications load. These proposals are generally based on unicast sender-based forwarding schemes. The greedy nature of sender-based forwarding can result in the selection of forwarders with weak radio links that might compromise the end-to-end performance. To overcome these limitations, this paper presents TOPOCBF, a novel contention-based broadcast forwarding protocol that dynamically selects forwarding paths based on their capability to route packets between anchor points. Such capability is estimated by means of a multi-hop connectivity metric. The obtained results demonstrate that TOPOCBF can provide good packet delivery ratios while reducing the communications load compared to unicast sender-based forwarding schemes using road traffic density estimates. 相似文献
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Chien-Chih Lai Ren-Guey Lee Chun-Chieh Hsiao Hsin-Sheng Liu Chun-Chang Chen 《Journal of Network and Computer Applications》2009,32(6):1229-1241
For the elderly and chronic patients with cardiovascular disease who live alone, it is necessary to constantly monitor their physiological parameters, especially the electrocardiogram (ECG), to effectively prevent and control their health condition and even to provide urgent treatment or care while an emergency such as the abnormal variation of heart rate (HR) occurs. In this paper, a wireless in-home physiological monitoring system, based on multi-hop relay communications, which can ubiquitously and continuously monitor the patient's ECG at any time or any place at home without space limit and the “dead spot” due to the extended communication coverage by multi-hop wireless connectivity, is proposed. The system consists of a mobile-care device, which is responsible for capturing and wirelessly sending the patient's ECG data, a wireless multi-hop relay network (WMHRN) that is in charge of relaying the data sent by the former, and a residential gateway (RG), which is responsible for gathering and uploading the received ECG data to the remote care server through the Internet to carry out the patient's health condition monitoring and the management of pathological data. However, in order to assure that the ECG data can be effectively and timely forwarded, from the mobile-care device to the RG through the WMHRN, to meet the healthcare quality of service (H-QoS) demand for reliable and real-time end-to-end ECG transmission, the analysis of WMHRN latency in data-forwarding stage and the deployment consideration of wireless relay nodes are investigated in detail in this work. Moreover, an emergency alert service using short message service (SMS), based on the detection of abnormal variation of HR, is also used in the RG to further enhance the healthcare service quality. A prototype of this system has been developed and implemented. Finally, the experimental results are presented to verify the feasibility of the proposed system. 相似文献
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Feature extraction for visible–infrared person re-identification (VI-ReID) is challenging because of the cross-modality discrepancy in the images taken by different spectral cameras. Most of the existing VI-ReID methods often ignore the potential relationship between features. In this paper, we intend to transform low-order person features into high-order graph features, and make full use of the hidden information between person features. Therefore, we propose a multi-hop attention graph convolution network (MAGC) to extract robust person joint feature information using residual attention mechanism while reducing the impact of environmental noise. The transfer of higher order graph features within MAGC enables the network to learn the hidden relationship between features. We also introduce the self-attention semantic perception layer (SSPL) which can adaptively select more discriminant features to further promote the transmission of useful information. The experiments on VI-ReID datasets demonstrate its effectiveness. 相似文献
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基于输电线路状态监测的通信特点和应用需求,分析电力光载无线通信系统的局限性,提出光载无线和无线多跳相结合的分层混合组网架构。考虑到输电场景的链式组网特点,为保证通信网络的可靠性,并防止网络单点失效带来的网络中断问题,提出3种多跳链路维护方法,对输电场景的通信系统建设具有一定借鉴意义。 相似文献
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During the last few years, the proliferation of miniaturised devices with networking capabilities has provided the technological grounds for pervasive networking environments. It is not visionary to foresee a world of pervasive devices embedded in the environment interacting between them, and with those carried by users, via wireless communications. In addition, fostered by the diffusion of small-size, computational-rich mobile devices, the way content is generated, and accessed is changing with respect to the legacy-Internet paradigm. An ever-increasing share of the Internet content is generated directly by the users, and shared on the network (following the User-Generated Content model). While today the legacy Internet is still used to share user-generated content, it is reasonable to envision that pervasive networking technologies will represent the natural platform to support this new model. This will result in content being distributed on users’ devices rather than on centralised servers on the Internet, and in users creating ad hoc networks to share content. The p2p paradigm is particularly suitable for this scenario, because communications will occur directly among users, instead of being necessarily mediated by centralised servers. Motivated by these remarks, in this work we focus on p2p multicast services over ad hoc networks aimed at sharing content among groups of users interested in the same topics. Specifically, starting from a reference solution in legacy wired networks (Scribe), we design a cross-layer optimised protocol (XScribe) that addresses most of the Scribe problems on ad hoc networks. XScribe exploits cross-layer interactions with a proactive routing protocol to manage group membership. Furthermore, it uses a lightweight, structureless approach to deliver data to group members. By jointly using experimental results and analytical models, we show that, with respect to Scribe, XScribe significantly reduces the packet loss and the delay experienced by multicast receivers, and increases the maximum throughput that can be delivered to multicast groups. 相似文献
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This paper presents a modeling framework for characterizing the feasibility and impacts of multi-hop packet routing in sensor networks with mobile sinks. Data collection in sensor networks using mobile sinks has recently been investigated to improve energy performance at the cost of collection delay. Although the data collection can be accomplished with varying degrees of multi-hop routing, for a given data generation rate, as the extent of multi-hop routing increases, the round traversal time of the sink decreases. At the same time, the interference experienced by the mobile sink-to-sensor links and the consequent upload time go up. This paper characterizes these competing effects and develops a methodology for determining the extent of multi-hop routing that is feasible for given network and application parameters such as sensor data generation rate, wireless link capacity between sensors and mobile sink, the speed of the mobile sink and node density. 相似文献
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Hybrid optical/electrical interconnects using commercial optical circuit switches have been previously proposed as an attractive alternative to fully-connected electronically-switched networks. Among other advantages, such a design offers increased port density, bandwidth/port, cabling and energy efficiency, compared to conventional packet-switched counterparts. Recent proposals for such system designs have looked at small and/or medium scale networks employing hybrid interconnects. In our previous work, we presented a hybrid optical/electrical interconnect architecture targeting large-scale deployments in high-performance computing and datacenter environments. To reduce complexity, our architecture employs a regular shuffle network topology that allows for simple management and cabling. Thanks to using a single-stage core interconnect and multiple optical planes, our design can be both incrementally scaled up (in capacity) and scaled out (in the number of racks) without requiring major re-cabling and network re-configuration. In this paper, we extend the fundamentals of our existing work towards quantifying and understanding the performance of these type of systems against more diverse workload communication patterns and system design parameters. In this context, we evaluate–among other characteristics–the overhead of the reconfiguration (decomposition and routing) scheme proposed and extend our simulations to highly adversarial flow generation rate/duration values that challenge the reconfiguration latency of the system. 相似文献
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