An adaptive ARQ scheme with packet combining for time varyingchannels

The dependence of the efficiency of hybrid type-II ARQ schemes on the packet size in the context of a simple packet combining scheme is discussed. A simple algorithm for adopting the optimum packet size according to the channel bit error rate (BER) is presented. Also, a very simple method of estimating the channel BER is provided     

An effective congestion control scheme for ATM networks

Congestion control is considered one of the most challenging issues of ATM. Simulation results are presented which show the performance superiority of the proposed scheme as compared to the conventional leaky bucket scheme. © 1998 John Wiley & Sons, Ltd.     

A simple adaptive routing scheme for congestion control inShuffleNet multihop lightwave networks

The authors describe a simple adaptive routing scheme for datagram (connectionless) and virtual circuit (connection-oriented) transmission that relieves congestion resulting from nonuniform traffic patterns and network failures. The authors describe a fixed-routing algorithm for dedicated channel ShuffleNets. Based on the fixed routing algorithm, an adaptive routing scheme for datagram transmission is presented followed by performance results for uniform and nonuniform traffic patterns and fault tolerance. The adaptive routing of datagrams uses only the local queue size information available at the network interface units (NIUs) and redistributes the load as congestion develops. Since datagrams are individually routed through the network, they may not arrive at their destination in the order they were generated and may need to be resequenced. The authors compute an upper estimate on the resequencing buffer size for stream traffic. A virtual circuit version of the adaptive routing algorithm eliminates the need for resequencing buffers     

A globally stable adaptive congestion control scheme for Internet-style networks with delay

In this paper, we develop, analyze and implement a congestion control scheme in a noncooperative game framework, where each user's cost function is composed of a pricing function proportional to the queueing delay experienced by the user, and a fairly general utility function which captures the user demand for bandwidth. Using a network model based on fluid approximations and through a realistic modeling of queues, we establish the existence of a unique equilibrium as well as its global asymptotic stability for a general network topology, where boundary effects are also taken into account. We also provide sufficient conditions for system stability when there is a bottleneck link shared by multiple users experiencing nonnegligible communication delays. In addition, we study an adaptive pricing scheme using hybrid systems concepts. Based on these theoretical foundations, we implement a window-based, end-to-end congestion control scheme, and simulate it in ns-2 network simulator on various network topologies with sizable propagation delays.     

A taxonomy for congestion control algorithms in packet switchingnetworks

The authors propose a new taxonomy for congestion control algorithms in packet switching computer networks based on control theory. They view a network as a large, distributed control system, in which a congestion control scheme is a (distributed) control policy executable at each node (host or switches) of the network in order to a certain level of stable conditions. This taxonomy provides a coherent framework for the comparative study of existing algorithms and offers clues toward the development of new congestion control strategies     

Adaptive threshold control scheme for packet acquisition

An adaptive threshold control scheme for packet acquisition is described. The threshold control is done adaptively by setting the threshold proportional to the maximum likelihood estimate of the noise power     

一种智能交通系统的自适应拥塞控制方法

针对突发性车流量自适应调整主通道流量控制,提出多相位路口时的自适应拥塞控制算法。提高系统管理算法在突发性车流状况中的适应能力,以两种信息通道实现车流队列管理的控制与学习功能。并结合参考模型机制实现模糊反向推理算法。仿真实验结果表明,该控制方案能改善实际交通状况,控制效果优于定时控制的方法,提高平面交通路口的通行能力50％以上。     

A control theoretical approach to congestion control in packet networks

In this paper, we introduce a control theoretical analysis of the closed-loop congestion control problem in packet networks. The control theoretical approach is used in a proportional rate controller, where packets are admitted into the network in accordance with network buffer occupancy. A Smith Predictor is used to deal with large propagation delays, common to high speed backbone networks. The analytical approach leads to accurate predictions regarding both transients as well as steady-state behavior of buffers and input rates. Moreover, it exposes tradeoffs regarding buffer dimensioning, packet loss, and throughput.     

改进的幻影方案在拥塞避免与控制中的应用

对高速网络中拥塞控制与拥塞避免的问题进行了研究。幻影方法是一种简单而有效的防止网络拥塞发生的流量控制方法。以此方法设计的控制算法不仅是收敛的,同时能够平稳地处理网络接入的新连接,并对所有的连接保持良好的公平性。通过选择一个参数来设置不同的拥塞级别并在不同的拥塞级别上采取相应的不同流量控制措施,改进的算法在保留了原来算法优点的基础上,增强了网络拥塞避免的能力。仿真试验表明了这一点。并基于统计推断中的抽样定理,分析了选择划分拥塞级别的参数的准则。     

Efficient and adaptive congestion control for heterogeneous delay-tolerant networks

Detecting and dealing with congestion in delay-tolerant networks (DTNs) is an important and challenging problem. Current DTN forwarding algorithms typically direct traffic towards more central nodes in order to maximise delivery ratios and minimise delays, but as traffic demands increase these nodes may become saturated and unusable. We propose CafRep, an adaptive congestion aware protocol that detects and reacts to congested nodes and congested parts of the network by using implicit hybrid contact and resources congestion heuristics. CafRep exploits localised relative utility based approach to offload the traffic from more to less congested parts of the network, and to replicate at adaptively lower rate in different parts of the network with non-uniform congestion levels. We extensively evaluate our work against benchmark and competitive protocols across a range of metrics over three real connectivity and GPS traces such as Sassy [44], San Francisco Cabs [45] and Infocom 2006 [33]. We show that CafRep performs well, independent of network connectivity and mobility patterns, and consistently outperforms the state-of-the-art DTN forwarding algorithms in the face of increasing rates of congestion. CafRep maintains higher availability and success ratios while keeping low delays, packet loss rates and delivery cost. We test CafRep in the presence of two application scenarios, with fixed rate traffic and with real world Facebook application traffic demands, showing that regardless of the type of traffic CafRep aims to deliver, it reduces congestion and improves forwarding performance.     

An adaptive opportunistic retransmission control scheme environment-aware-based for wireless multimedia Mesh networks

In this paper, we propose an aware-based adaptive opportunistic retransmission control scheme for wireless multimedia Mesh networks. The proposed scheme provides maximum retransmission count optimization based on environment-aware to improve packet relay probability. The scheme discriminates the types of packet loss in wireless link by means of environment information and selects the retransmission count by taking the IEEE 802.11 wireless channel characteristics into consideration. Furthermore, the maximum retransmission count of MAC is adjusted adaptively. Extensive simulations demonstrate that the proposed scheme significantly reduces packet collision probability and packet loss rate, and thus improves network throughput.     

TCP-Peach: a new congestion control scheme for satellite IPnetworks

Current TCP protocols have lower throughput performance in satellite networks mainly due to the effects of long propagation delays and high link error rates. In this paper, a new congestion control scheme called TCP-Peach is introduced for satellite networks. TCP-Peach is composed of two new algorithms, namely Sudden Start and Rapid Recovery, as well as the two traditional TCP algorithms, Congestion Avoidance and Fast Retransmit. The new algorithms are based on the novel concept of using dummy segments to probe the availability of network resources without carrying any new information to the sender. Dummy segments are treated as low-priority segments and accordingly they do not effect the delivery of actual data traffic. Simulation experiments show that TCP-Peach outperforms other TCP schemes for satellite networks in terms of goodput. It also provides a fair share of network resources     

Throughput increase in packet forwarding engines using adaptive block-selection scheme

We propose a new approach for using the block-selection scheme to increase the search throughput in a multi-block TCAM-based packet forwarding engine. While the existing methods try to counter and forcibly balance the inherent bias of the Internet traffic, our method takes advantage of it hence improving flexibility of table management and scalability towards high rates of change in traffic bias. This approach also offers higher throughput than the current art.     

自适应判决门限延时相关分组检测算法

提出了结合双滑动窗口方法和延时相关分组检测的优化算法。该算法利用双滑动窗口算法在峰值点可以用于估计接收信号信噪比的特点,通过对接收信号信噪比的简单估计来确定最佳判决门限,动态跟踪信道变化,使分组同步更加准确。新算法在IEEE802.11a系统中进行了仿真,结果表明新算法的性能比原延时相关分组检测算法有了很大提高。     

An adaptive coding scheme for time-varying channels

An adaptive coding scheme for digital communication over time-varying channels is presented. The scheme is based on a finite-state Markov channel model. Emphasis is on the adaptation of the error protection to the actual channel state. The throughput gains that are achieved by the adaptive scheme relative to the conventional nonadaptive coding methods are demonstrated by several examples. Of special interest is the use of punctured convolutional codes with maximum-likelihood Viterbi algorithm to enable adaptive encoding and decoding without modifying the basic structure of the encoder and the decoder     

An adaptive current control scheme for PWM synchronous motordrives: analysis and simulation

Two schemes for controlling the motor currents in PWM (pulse-width-modulated) inverters in synchronous motor drives are considered: hysteresis control and predictive control. It is pointed out that the system static and dynamic performance can be improved by selecting the control mode in an adaptive manner according to the operating conditions. In steady state, the predictive mode is selected to reduce current ripple and to obtain stable switching frequency. During large transients, such as during starting or load variations, the hysteresis mode is selected to provide fast response. The performance of the proposed controls scheme has been studied by simulation, and the results agree well with the prediction. This adaptive control scheme can be implemented using a high-performance 16-bit microcontroller supported by a mathematical coprocessor     

基于DSP技术的光尾流实时探测方案

利用尾流的光散射特性对其进行探测 ,光散射谱强度分布的半值宽度随尾流中气泡群的密度而变化。基于成熟的信号处理技术 ,文中提出了对尾流进行实时探测的解决方案。系统采用CCD光采样 ,ADC数据采集及FIFO缓存 ,DSP数据处理三级流水线方式工作。充分发挥DSP处理器片内存储器容量大的特点 ,使用其片内数据缓冲区交替对CCD进行信号采集和数据处理 ;在进行数据处理过程中 ,处理器以中断方式读取FIFO缓存结果。     

主动扣费提醒实时扣费用户实现方案

为保护消费者合法权益,提高增值业务订购的透明度,让客户明明白白消费,中国移动全面实施增值业务扣费主动提醒等服务。对于广东省8000万智能网用户,将智能网用户的增值业务消费由实时扣费切换为话单扣费存在较严重的户欠费停机风险。为了规避欠费风险,保障用户感知,制定了实时扣费用户增值业务扣费提醒方案:通过实时鉴权有效规避了用户的欠费风险,通过离线话单实现了扣费提醒要求。通过业务配置的方式实现了针对业务级的灵活可配置。     

Deterministic packet marking for time-varying congestion price estimation

The addition of the two-bit Explicit Congestion Notification (ECN) field to the IP header provides routers with a mechanism for conveying link price information necessary for the successful operation of a number of congestion control schemes. Two recent proposals for probabilistic packet marking at the routers allow receivers to estimate path price from the fraction of marked packets. In this paper we introduce an alternative deterministic marking scheme for encoding path price. Each router quantizes the price of its outgoing link to a fixed number of bits. Every data packet sent along the path encodes a partial sum of the quantized link prices in its ECN field, allowing the receiver to estimate the path price. We evaluate the performance of our algorithm in terms of its error in representing prices, and compare it to probabilistic marking. We show that based on empirical Internet traffic characteristics, our algorithm performs better when estimating time-varying prices and static path price using small blocks of packets.