共查询到18条相似文献,搜索用时 140 毫秒
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本论文在分析无线传感器网络不同于普通有线网络的特征后,提出了一种适用于无线传感器网络的TCP 拥塞控制机制DW-TCP,此机制将TCP拥塞窗口分为拥塞丢包窗口和误码丢包窗口,在链路误码率较高时通过降低发送速率提高数据发送的可靠性,节约无线节点的能源消耗和系统不必要的开销,该机制不但考虑到拥塞丢包对数据发送速率的影响,而且考虑到无线链路中的误码丢包对数据发送速率的影响. 相似文献
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针对无线环境下TCP(传输控制协议)调用拥塞控制算法致使性能下降的问题,提出一种基于ECN(显式拥塞通知)跨层机制的无线TCP改进方法。算法在ECN机制上判断网络是否拥塞以及丢包发生时具体丢包类型。并在此基础上针对网络具体状况采取不同的拥塞窗口控制机制,更精确的网络信息有效提高了数据发送的可靠性。仿真结果表明该算法可提... 相似文献
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现有的数字广播网络由于没有回传通道,发送端无法知悉传输过程中的丢包状况。接收端处在广播网络的不同位置,常常因处于小区边缘或受障碍物遮挡等原因造成信号减弱,从而导致丢包率提高。该文提出了一种基于pFEC (patching Forward Error Correction,补丁FEC)的丢包恢复机制,来解决单向广播网络的丢包问题。该方法利用蜂窝移动网络的双向信道来传输补丁流,提供自适应的FEC来降低丢包率。这种方式可以在广播业务中为不同位置的用户提供不同的丢包恢复能力。理论建模及仿真结果显示,在蜂窝移动网络丢包率不高的情况下,pFEC机制能够有效应对个别用户突发的丢包,从而提高广播业务整体的可靠性和服务质量。 相似文献
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当今车辆运行环境更加复杂,双移动节点,无线链路带宽不稳定以及链路级丢包较多是车载自组网的显著特点之一,而车载自组网无线链路质量,对其网络上层协议的设计具有重要意义。这里分析无线电波在车载自组网中的传播特点,提出一种以无线信道传播模型为基础,通过OMNET++来仿真车载自组网无线链路丢包率的方法。通过该方法可以方便、有效地仿真不同车辆运行环境下车载自组网的无线链路丢包率。 相似文献
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研究了光无线混合接入网中具有抗毁能力的节能路由问题,结合光网络单元(ONU)休眠控制和风险备用路由表维护机制,提出一种有效的可靠绿色路由算法。该算法为每个无线路由器维护一个风险表,以记录网络中路径是否可用以及ONU活跃与否的状态信息,通过鼓励选择ONU活跃的可用路径来传输数据,可降低全网丢包率和能耗。仿真结果表明:该算法能够在稳定丢包率的同时更好地节省能量。 相似文献
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在无线多跳网络中,本地重传和网络编码已经被成功地应用到多路径技术上以增加吞吐量并减少丢包。然而,在提高UDP传输性能的同时,也产生了数据包重排序和延迟等副作用,严重影响了TCP性能。针对此问题,主要提出一种基于网络编码的多路径传输方案NC-MPTCP,即在无线mesh网络的多条路径中引入网络编码、执行拥塞控制以及使用一个基于信用的方法控制节点的传输速率,提高网络的吞吐量以及增加网络传输的可靠性。该方案使用一个简单的算法,评估丢包率以及发送线性组合数据包的速率,用来降低目的节点的数据包解码延迟和防止TCP的超时重传。仿真结果表明设计的NC-MPTCP有效。 相似文献
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Wassim Ramadan Eugen Dedu Dominique Dhoutaut Julien Bourgeois 《Telecommunication Systems》2013,52(4):1797-1817
One major yet unsolved problem in wired-cum-wireless networks is the classification of losses, which might result from wireless temporary interferences or from network congestion. The transport protocol response to losses should be different for these two cases. If the transmission uses existing protocols like TCP, the losses are always classified as congestion losses by sender, causing reduced throughput. In wired networks, ECN (Explicit Congestion Notification) can be used to control the congestion through active queue management such as RED (Random Early Detection). It can also be used to solve the transport protocol misreaction over wireless networks. This paper proposes a loss differentiation method (RELD), based on ECN signaling and RTT (Round Trip Time), and applied to TCPlike. TCPlike is one of the three current congestion controls present in the new transport protocol DCCP (Datagram Congestion Control Protocol). Our simulations, using a more realistic simulated loss error model for wireless networks, show that RELD optimizes congestion control and therefore increases the performance of transport protocols over wireless networks, leading to an average performance gain ranging from 10% to 15%. 相似文献
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《Signal Processing: Image Communication》2004,19(5):405-419
In a wireless network packet losses can be caused not only by network congestion but also by unreliable error-prone wireless links. Therefore, flow control schemes which use packet loss as a congestion measure cannot be directly applicable to a wireless network because there is no way to distinguish congestion losses from wireless losses. In this paper, we extend the so-called TCP-friendly flow control scheme, which was originally developed for the flow control of multimedia flows in a wired IP network environment, to a wireless environment. The main idea behind our scheme is that by using explicit congestion notification (ECN) marking in conjunction with random early detection (RED) queue management scheme intelligently, it is possible that not only the degree of network congestion is notified to multimedia sources explicitly in the form of ECN-marked packet probability but also wireless losses are hidden from multimedia sources. We calculate TCP-friendly rate based on ECN-marked packet probability instead of packet loss probability, thereby effectively eliminating the effect of wireless losses in flow control and thus preventing throughput degradation of multimedia flows travelling through wireless links. In addition, we refine the well-known TCP throughput model which establishes TCP-friendliness of multimedia flows in a way that the refined model provides more accurate throughput estimate of a TCP flow particularly when the number of TCP flows sharing a bottleneck link increases. Through extensive simulations, we show that the proposed scheme indeed improves the quality of the delivered video significantly while maintaining TCP-friendliness in a wireless environment for the case of wireless MPEG-4 video. 相似文献
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主动队列管理算法性能评价:比较研究 总被引:3,自引:0,他引:3
对当前的主动队列管理算法进行了分类,然后基于NS2网络仿真器比较了它们在不同流量和网络拓扑条件下的多种性能指标。主要结论包括:ARED综合表现最好;PI和REM的瞬态性能较差,对动态流量响应较慢:REM和没有ECN支持的AVQ可以得到较小的时延,但同时牺牲了链路的带宽利用率并造成大量分组丢失;在多瓶颈网络拓扑中,大部分算法的性能有所提高。 相似文献
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Richelle V. Adams 《Wireless Personal Communications》2018,99(3):1195-1215
By simulation using NS-3 we evaluated the performance of voice, video and web traffic sharing a wireless access network connected to a wired core. We compared the performance in terms of end-to-end delay, end-to-end delay variation, average throughput and loss percentage. For the wireless access network, we considered cases when it consisted of a single technology type, e.g., WiFi (IEEE 802.11), WiMAX (IEEE 802.16) and LTE, and when it was heterogeneous, i.e., when the three technologies coexisted and simultaneously shared the same IP core. We attempted to ascertain the impact of this type of heterogeneity on end-to-end performance. It was found that this heterogeneity in the wireless access portion of the network can improve, degrade or have no impact on application performance depending on the network conditions and the application itself. Some key research challenges in Fifth Generation wireless communications are heterogeneous Cloud Radio Access Networks (HC-RANS), backward compatiblity with 4G/3G networks and providing low-latency and QoE. To achieve end-to-end QoS guarantees in such settings the interface with the core must also be addressed, especially when backward compatibility is to be assured. This simulation study attempts to highlight the impact of this type of heterogeneity on network performance. 相似文献
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分析了基于低功耗自适应分簇(LEACH)路由协议的无线传感网络(WSN)在不同拓扑形状下的生命周期,并改进了长方形拓扑形状的路由协议。进而针对WSN在某些场合能量有限、易受干扰和安全性差等缺点,在长方形区域中引入分布式光纤传感结构。将传感光纤铺设在环境复杂和外界电磁波干扰大的监测区域,从而提高整个传感网络的生命周期和可靠性。理论分析和仿真结果表明,改进的拓扑和协议在提高可靠性的同时,有效地延长了光WSN的生存时间,性能优于传统LEACH协议。 相似文献
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无线定位技术在现代社会中发挥着重要的作用。文中首先描述基于GPS、蜂窝网络和RFID的3种典型无线定位技术的原理,分析了各自的特点,并介绍了混合无线定位技术在手机定位和智能交通管理中的应用实例。研究表明,混合无线定位技术,综合了多种无线定位技术的优点,能有效提高定位准确性和可靠性,是无线定位技术发展的趋势。 相似文献