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TCP的控制隐含了一个假设,即分组丢失都是由网络拥塞引起的,而这一点对于无线网络不成立.因此在无线情况下,会引入了冗余控制,使得传输性能下降.浮点窗口算法(FeW)通过限制TCP的分组注入量,减少冗余控制,在此基础上,提出了改进方案自适应包长算法(APS).仿真数据表明,基于FeW的APS算法(APS-FeW)比FeW算法提升了10%~25%的吞吐量. 相似文献
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The transmission control protocol (TCP) is one of the most important Internet protocols. It provides reliable transport services between two end‐hosts. Since TCP performance affects overall network performance, many studies have been done to model TCP performance in the steady state. However, recent researches have shown that most TCP flows are short‐lived. Therefore, it is more meaningful to model TCP performance in relation to the initial stage of short‐lived flows. In addition, the next‐generation Internet will be an unified all‐IP network that includes both wireless and wired networks integrated together. In short, modelling short‐lived TCP flows in wireless networks constitutes an important axis of research. In this paper, we propose simple wireless TCP models for short‐lived flows that extend the existing analytical model proposed in [IEEE Commun. Lett. 2002; 6 (2):85–88]. In terms of wireless TCP, we categorized wireless TCP schemes into three types: end‐to‐end scheme, split connection scheme, and local retransmission scheme, which is similar to the classification proposed in [IEEE/ACM Trans. Networking 1997; 756–769]. To validate the proposed models, we performed ns‐2 simulations. The average differences between the session completion time calculated using the proposed model and the simulation result for three schemes are less than 9, 16, and 7 ms, respectively. Consequently, the proposed model provides a satisfactory means of modelling the TCP performance of short‐lived wireless TCP flows. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Masafumi Hashimoto Go Hasegawa Masayuki Murata 《International Journal of Communication Systems》2015,28(14):1965-1986
A common strategy for energy saving in wireless network devices is to remain in sleep mode for as long as possible. The timing of packet transmission and reception depends on the behavior of the transport‐layer protocols used by upper‐layer applications. Therefore, understanding the relation between the behavior of the transport‐layer protocols and energy efficiency using sleep mode is important for effective energy saving, especially when a wireless network interface (WNI) is activated in sleep mode at packet interarrivals. In this paper, we analyze the energy consumption of a client's WNI in Transmission Control Protocol (TCP) data transfer over a wireless LAN by focusing on the detailed behavior of TCP congestion control mechanisms. This model considers three situations: the WNI is activated in continuously active mode, in sleep mode, and in sleep mode with burst transmission. The latter is proposed as an effective method to improve energy efficiency, which lengthens sleep periods by transmitting and receiving multiple packets in a bursty fashion. Through numerical examples, we show that sleeping without modification of transmission timing reduces energy consumption in TCP data transfer by only around 10%, and that the burst transmission can contribute further 50% energy reduction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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The pervasiveness of the transport control protocol (TCP) and the proliferation of wireless local area networks (WLAN) of the 802.11 type make the topic of TCP performance over last hop wireless networks very relevant. The Snoop protocol, a link layer solution introduced several years ago to improve the performance of TCP in this scenario, has been shown to neglect its benefits to the most widely used TCP version, TCP SACK. In this paper, we introduce the TCP SACK‐Aware Snoop protocol to address this problem. Our results indicate that the TCP SACK‐Aware Snoop protocol improves the performance of TCP SACK by around 30% compared with the original Snoop protocol and by about 8% in an environment where no TCP enhancing mechanism is in place. In addition, we introduce further modifications to the proposed protocol to make its advantages available to any TCP sender. We also show that the mechanism does not introduce unfairness among TCP sources and somewhat protects TCP against UDP traffic. Our results show important throughput improvements to all TCP versions and demonstrate that the TCP SACK‐Aware Snoop protocol shields TCP from last hop wireless losses providing throughtput values very close to the maximum possible. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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主动队列管理(AQM)是对抗拥塞的重要手段,其经典算法之一是随机早期丢弃,简称RED。为使其能适应无线传输高突发误帧的特点,本文提出了一种基于平均队列长度和平均包到达速率的改进RED算法,分析了其相对于传统RED算法在预防和处理拥塞时的优势。同时针对无线信道的时变特性,提出自适应MIR速率调整,以提高频谱利用率和进一步降低拥塞概率,并讨论了其对于系统性能的改善。 相似文献
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Roman Dunaytsev Dmitri Moltchanov Yevgeni Koucheryavy Jarmo Harju 《International Journal of Communication Systems》2011,24(12):1533-1564
In this paper, we propose an analytical cross‐layer model for a Transmission Control Protocol (TCP) connection running over a covariance‐stationary wireless channel with a completely reliable Automatic Repeat reQuest scheme combined with Forward Error Correction (FEC) coding. Since backbone networks today are highly overprovisioned, we assume that the wireless channel is the only one bottleneck in the system which causes packets to be buffered at the wired/wireless interface and dropped as a result of buffer overflow. We develop the model in two steps. At the first step, we consider the service process of the wireless channel and derive the probability distribution of the time required to successfully transmit an IP packet over the wireless channel. This distribution is used at the next step of the modeling, where we derive expressions for the TCP long‐term steady‐state throughput, the mean round‐trip time, and the spurious timeout probability. The developed model allows to quantify the joint effect of many implementation‐specific parameters on the TCP performance over both correlated and non‐correlated wireless channels. We also demonstrate that TCP spurious timeouts, reported in some empirical studies, do not occur when wireless channel conditions are covariance‐stationary and their presence in those measurements should be attributed to non‐stationary behavior of the wireless channel characteristics. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Nasim Arianpoo Paria Jokar Victor C.M. Leung 《Wireless Communications and Mobile Computing》2014,14(13):1302-1313
There is growing interest in the use of wireless mesh network (WMN) as a last‐mile option for Internet access. Despite the many benefits of WMNs, the performance of Internet access may not be ideal. One of the main issues is the interaction of transmission control protocol (TCP) with the underlying network. The poor performance of TCP over multi‐hop networks is well‐documented, and extensive research exists, which addresses TCPs foible and enhance TCP performance for multi‐hop environments. This paper provides a thorough survey of TCP performance issues over WMNs and the available solutions to address these issues. Among the existing methods, we focused on network coding (NC) and the ways that TCP interacts with network coded systems. NC is a technique that encodes the received packets in each node before forwarding them towards the destination. The use of NC in the transport layer to address performance issues raised by wireless access is a recent research topic. This paper presents a detailed study of TCP interaction with NC. Some open research areas in this field are suggested. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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无线信道安全传输的目的是保证期望用户具有良好的通信质量(高速率、低误码率),同时尽可能地提高窃听者的误码率,从而防止信息被窃听者截获。本文重点讲述无线信息安全传输机制。 相似文献
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Wei‐Peng Chen Yung‐Ching Hsiao Jennifer C. Hou Ye Ge Michael P. Fitz 《Wireless Communications and Mobile Computing》2002,2(1):37-57
It is well known that the performance of TCP deteriorates in a mobile wireless environment. This is due to the fact that although the majority of packet losses are results of transmission errors over the wireless links, TCP senders still take packet loss as an indication of congestion, and adjust their congestion windows according to the additive increase and multiplicative decrease (AIMD) algorithm. As a result, the throughput attained by TCP connections in the wireless environment is much less than it should be. The key problem that leads to the performance degradation is that TCP senders are unable to distinguish whether packet loss is a result of congestion in the wireline network or transmission errors on the wireless links. In this paper, we propose a light‐weight approach, called syndrome, to improving TCP performance in mobile wireless environments. In syndrome, the BS simply counts, for each TCP connection, the number of packets that it relays to the destination host so far, and attaches this number in the TCP header. Based on the combination of the TCP sequence number and the BS‐attached number and a solid theoretical base, the destination host will be able to tell where (on the wireline or wireless networks) packet loss (if any) occurs, and notify TCP senders (via explicit loss notification, ELN) to take appropriate actions. If packet loss is a result of transmission errors on the wireless link, the sender does not have to reduce its congestion window. Syndrome is grounded on a rigorous, analytic foundation, does not require the base station to buffer packets or keep an enormous amount of states, and can be easily incorporated into the current protocol stack as a software patch. Through simulation studies in ns‐2 (UCB, LBNL, VINT network simulator, http://www‐mash.cs.berkeley.edu/ns/ ), we also show that syndrome significantly improves the TCP performance in wireless environments and the performance gain is comparable to the heavy‐weight SNOOP approach (either with local retransmission or with ELN) that requires the base station to buffer, in the worst case, a window worth of packets or states. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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We propose using the TCP decoupling approach to improve a TCP connection's goodput over wireless networks. The performance improvement can be analytically shown to be proportional to
, where MTU is the maximum transmission unit of participating wireless links and HP_Sz is the size of a packet containing only a TCP/IP header. For example, on a WaveLAN [32] wireless network, where MTU is 1500 bytes and HP_Sz is 40 bytes, the achieved goodput improvement is about 350%. We present experimental results demonstrating that TCP decoupling outperforms TCP reno and TCP SACK. These results confirm the analysis of
performance improvement. 相似文献
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Wireless packet ad hoc networks are characterized by multi‐hop wireless connectivity and limited bandwidth competed among neighboring nodes. In this paper, we investigate and evaluate the performance of several prevalent TCP algorithms in this kind of network over the wireless LAN standard IEEE 802.11 MAC layer. After extensively comparing the existing TCP versions (including Tahoe, Reno, New Reno, Sack and Vegas) in simulations, we show that, in most cases, the Vegas version works best. We reveal the reason why other TCP versions perform worse than Vegas and show a method to avoid this by tuning a TCP parameter— maximum window size. Furthermore, we investigate the performance of these TCP algorithms when they run with the delayed acknowledgment (DA) option defined in IETF RFC 1122, which allows the TCP receiver to transmit an ACK for every two incoming packets. We show that the TCP connection can gain 15 to 32 per cent good‐put improvement by using the DA option. For all the TCP versions investigated in this work, the simulation results show that with the maximum window size set at approximately 4, TCP connections perform best and then all these TCP variants differ little in performance. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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异构无线网络垂直切换技术综述 总被引:1,自引:0,他引:1
垂直切换是多网融合的基础,是实现异构网络互通、支持不同接入方式无缝衔接的核心技术,目前正在受到业界的重点关注,并成为学术界研究的热点问题。随着无线移动通信技术向接入多元化、网络一体化和应用综合化的方向发展,各种蜂窝移动接入、宽带无线接入和固定接入将共同接入基于IP的统一核心网络,通过网络间的垂直切换,支持用户的移动性和移动过程中业务的连续性。首先给出了垂直切换的定义和基本概念,介绍了垂直切换的分类和基本流程,随后详细论述垂直切换的切换判决和切换执行2个环节。针对切换判决,总结了现有判决算法,重点评述各代表算法工作原理并剖析论其特点和存在的不足。针对切换执行,详述了现有垂直切换执行机制的工作原理和适用场景,并分析其优缺点。最后,对未来垂直切换技术的研究方向进行了展望。 相似文献
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为了计算无线自组织网络中准确的TCP容量,并利用其进行有效的窗口控制,以避免拥塞窗口增长过速的问题,提出一种适用于无线自组织网络TCP容量的优化计算。此方法基于时延和空间复用率,考虑网络中竞争干扰,解决了以往的计算方法对拓扑不能广泛适用的问题。模拟结果显示,基于文章的TCP容量进行拥塞窗口调节,能有效地提高网络的吞吐量。 相似文献