共查询到20条相似文献,搜索用时 15 毫秒
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Internet的迅速发展使得计算机网络的资源分配成为数据通信研究领域的热点.在Internet由单一服务质量过渡到支持多种服务质量的过程中,传输控制协议(TCP)将一直是主要的端到端的资源分配方案.本文深入分析了具有不同传输延时的TCP连接竞争资源时的公平性.研究表明,TCP算法对具有较大传输延时的连接具有不公平性.当竞争带宽的各连接的传输延时按比例减小时,小传输延时的连接对大传输延时的连接的抑制性相对减弱,这种不公平性将减弱.结论对于TCP算法的改进具有重要意义,同时这种不公平性对于设计分级服务方案将有很好的应用前景. 相似文献
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Optical packet assembly is a key function to support inter-working between TCP/IP networks and optical packet-switched networks.
It is characterized by the assembly delay and by the segment aggregation needed to form an optical packet. These counter-balancing
aspects depend on several environment variables, such as the TCP parameters, the access link speed, the optical packet size
whose effects are studied in this paper. Performance evaluations are obtained by extensive simulations in terms of send rate
of TCP flows, fairness, efficiency, and assembly delay. Some guidelines in the design of optical packets that take into account
the results presented are given. 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 Personal Communications - In the modern era, WSNs broadly used in many research areas. Mainly researchers are focusing on rising the network lifetime, throughput and decreasing the energy... 相似文献
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这篇论文推出了一种基于ZigBee技术的可穿戴传感器网络的无所不在的卫生保健系统,详细阐明了其系统结构及组成部分。用此结构收集和传送病人的生理数据与环境参数给卫生保健中心。这个基于异构无线接入网的病人监测系统,集成多个无线技术,在病人移动的情况下,支持连续的,任意时间,任意地点的用户愿意的生理监测。并针对该系统作了硬件与软件的设计。 相似文献
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网络切换对TCP吞吐量和公平性的影响分析 总被引:2,自引:1,他引:1
无线移动网络的发展日新月异.TCP协议是目前互联网上使用的最为广泛的端到端可靠传输协议,但其应用在无线网络上的时候,TCP性能下降明显.文中详细分析了TCP移动网络的切换对TCP造成影响的几个重要方面.最后通过在NS2上进行实验揭示了对多个TCP流公平性的影响,即切换后RTT越小的TCP流的吞吐量增长的越快,同时静态链路会夺取无线链路的链路资源. 相似文献
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In this paper a new TCP variant, named TCP-Binary Increase, Adaptive Decrease is presented. The suggested congestion control algorithm is a joint approach of Westwood and an enhanced version of BIC, for improving TCP performance in broadband wireless access networks. BIAD has been evaluated with respect to other TCP variants such as Reno, Westwood, BIC, CUBIC, HSTCP and STCP with the use of network simulator 2. The results indicate that the proposed solution achieves high network utilization levels in a wide range of network settings, including wireless channel errors, link asymmetry and congestion. We also evaluated TCP-BIAD when multiple flows share a bottlenecked access link and we show that it demonstrates the fairness features required for network deployment. 相似文献
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异构无线网络互连后的安全问题是当前网络安全研究的一个热点问题,为了解决异构网络互连后产生的接入安全问题,提出了一种基于信任模型的可信接入框架,该框架建立了异构无线网络间的信任评价体系,对接入异构无线网络用户除了进行身份验证,还必须进行用户信任度的验证,既拒绝了恶意节点接入,又确保了合法节点的安全接入,从而保证异构无线网络互连接入的安全和可信。 相似文献
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Neng-Chung Wang Jong-Shin Chen Yung-Fa Huang Chi-Lun Chiou 《Wireless Personal Communications》2008,47(3):399-415
In this paper, we propose a scheme that dynamically adjusts the slow start threshold (ssthresh) of TCP. The ssthresh estimation is used to set an appropriate ssthresh. A good ssthresh would improve the transmission performance of TCP. For the congestion avoidance state, we present a mechanism that probes
the available bandwidth. We adjust the congestion window size (cwnd) appropriately by observing the round trip time (RTT) and reset the ssthresh after quick retransmission or timeout using the ssthresh estimation. Then the TCP sender can enhance its performance by using the ssthresh estimation and the observed RTT. Our scheme defines what is considered an efficient transmission rate. It achieves better
utilization than other TCP versions. Simulation results show that our scheme effectively improves TCP performance. For example,
when the average bottleneck bandwidth is close to 30% of the whole network bandwidth, our scheme improves TCP performance
by at least 10%.
相似文献
Chi-Lun ChiouEmail: |
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针对服务质量(QoS)保证技术问题,从移动性、无线链路特性和IP网络传统的QoS保证技术的改进几个方面出发,对下一代支持多种移动无线接入的IP网络中,QoS保证技术的相关研究热点及技术现状进行了分析和总结,并提出了本研究方向QoS分层模型和进一步的研究建议。 相似文献
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In this paper, we consider the transport capacity of ad hoc networks with a random flat topology under the present support of an infinite capacity infrastructure network. Such a network architecture allows ad hoc nodes to communicate with each other by purely using the remaining ad hoc nodes as their relays. In addition, ad hoc nodes can also utilize the existing infrastructure fully or partially by reaching any access point (or gateway) of the infrastructure network in a single or multi-hop fashion. Using the same tools as in [9], we show that the per source node capacity of Θ(W/log(N)) can be achieved in a random network scenario with the following assumptions: (i) The number of ad hoc nodes per access point is bounded above, (ii) each wireless node, including the access points, is able to transmit at W bits/sec using a fixed transmission range, and (iii) N ad hoc nodes, excluding the access points, constitute a connected topology graph. This is a significant improvement over the capacity of random ad hoc networks with no infrastructure support which is found as
in [9]. We also show that even when less stringent requirements are imposed on topology connectivity, a per source node capacity figure that is arbitrarily close to Θ(1) cannot be obtained. Nevertheless, under these weak conditions, we can further improve per node throughput significantly. We also provide a limited extension on our results when the number of ad hoc nodes per access point is not bounded.Ulaş C. Kozat was born in 1975, in Adana, Turkey. He received his B.Sc. degree in Electrical and Electronics Engineering from Bilkent University, Ankara, Turkey and his M.Sc. in Electrical Engineering from The George Washington University, Washington D.C. in 1997 and 1999 respectively. He has received his Ph.D. degree in May 2004 from the Department of Electrical and Computer Engineering at University of Maryland, College Park. He has conducted research under the Institute for Systems Research (ISR) and Center for Hybrid and Satellite Networks (CSHCN) at the same university. He worked at HRL Laboratories and Telcordia Technologies Applied Research as a research intern. His current research interests primarily focus on wireless and hybrid networks that span multiple communication layers and networking technologies. Mathematical modelling, resource discovery and allocation, vertical integration of wireless systems and communication layers, performance analysis, architecture and protocol development are the main emphasis of his work. E-mail: kozat@isr.umd.eduLeandros Tassiulas (S′89, M′91) was born in 1965, in Katerini, Greece. He obtained the Diploma in Electrical Engineering from the Aristotelian University of Thessaloniki, Thessaloniki, Greece in 1987, and the M.S. and Ph.D. degrees in Electrical Engineering from the University of Maryland, College Park in 1989 and 1991 respectively.He is Professor in the Dept. of Computer and Telecommunications Engineering, University of Thessaly, Greece and Research Professor in the Dept. of Electrical and Computer Eng and the Institute for Systems Research, University of Maryland College Park since 2001. He has held positions as Assistant Professor at Polytechnic University New York (1991–95), Assistant and Associate Professor University of Maryland College Park (1995–2001) and Professor University of Ioannina Greece (1999–2001).His research interests are in the field of computer and communication networks with emphasis on fundamental mathematical models, architectures and protocols of wireless systems, sensor networks, high-speed internet and satellite communications.Dr. Tassiulas received a National Science Foundation (NSF) Research Initiation Award in 1992, an NSF CAREER Award in 1995 an Office of Naval Research, Young Investigator Award in 1997 and a Bodosaki Foundation award in 1999 and the INFOCOM′94 best paper award. E-mail: leandros@isr.umd.edu 相似文献
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The use of multibeam antennas (MBAs) in decentralized wireless networks significantly increases the throughput by improving
spatial reuse and extending coverage compared with single-beam antennas. The throughput performance may, however, degrade
in multipath environments due to the fact that multipath propagation increases the probability of collision among different
users. Based on the probability of collision, accurate analytical expressions are derived for the node throughput gain (NTG)
of a wireless network using MBAs in quasi-stationary multipath environments. The results show that a higher number of propagation
paths cause more frequent collisions and thus yield lower node throughput.
相似文献
Moeness G. AminEmail: |
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In Wireless Mesh Networks (WMNs), the performance of conventional TCP significantly deteriorates due to the unreliable wireless channel. To enhance TCP performance in WMNs, TCP/LT is proposed in this paper. It introduces fountain codes into packet reorganization in the protocol stack of mesh gateways and mesh clients. Furthermore, it is compatible with conventional TCP. Regarded as a Performance Enhancement Proxies (PEP), a mesh gateway buffers TCP packets into several blocks. It simultaneously processes them by using fountain encoders and then sends them to mesh clients. Apart from the improvement of the throughput of a unitary TCP flow, the entire network utility maximization can also be ensured by adjusting the scale of coding blocks for each TCP flow adaptively. Simulations show that TCP/LT presents high throughput gains over single TCP in lossy links of WMNs while preserving the fairness for multiple TCPs. As losses increase, the transmission delay of TCP/LT experiences a slow linear growth in contrast to the exponential growth of TCP. 相似文献
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Chaporkar P. Kar K. Xiang Luo Sarkar S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(2):572-594
The question of providing throughput guarantees through distributed scheduling, which has remained an open problem for some time, is addressed in this paper. It is shown that a simple distributed scheduling strategy, maximal scheduling, attains a guaranteed fraction of the maximum throughput region in arbitrary wireless networks. The guaranteed fraction depends on the ldquointerference degreerdquo of the network, which is the maximum number of transmitter-receiver pairs that interfere with any given transmitter-receiver pair in the network and do not interfere with each other. Depending on the nature of communication, the transmission powers and the propagation models, the guaranteed fraction can be lower-bounded by the maximum link degrees in the underlying topology, or even by constants that are independent of the topology. The guarantees are tight in that they cannot be improved any further with maximal scheduling. The results can be generalized to end-to-end multihop sessions. Finally, enhancements to maximal scheduling that can guarantee fairness of rate allocation among different sessions, are discussed. 相似文献