Fairness in MIMD Congestion Control Algorithms

The Mulitplicative Increase Multiplicative Decrease (MIMD) congestion control algorithm in the form of Scalable TCP has been proposed for high speed networks. We study fairness among sessions sharing a common bottleneck link, where one or more sessions use the MIMD algorithm. Losses, or congestion signals, occur when the capacity is reached but could also be initiated before that. Both synchronous as well as asynchronous losses are considered. In the asynchronous case, only one session suffers a loss at a loss instant. Two models are then considered to determine which source looses a packet: a rate dependent model in which the packet loss probability of a session is proportional to its rate at the congestion instant, and the independent loss rate model. We first study how two MIMD sessions share the capacity in the presence of general combinations of synchronous and asynchronous losses. We show that, in the presence of rate dependent losses, the capacity is fairly shared whereas rate independent losses provide high unfairness. We then study inter protocol fairness: how the capacity is shared in the presence of synchronous losses among sessions some of which use Additive Increase Multiplicative Decrease (AIMD) protocols whereas the others use MIMD protocols.     

An Upward Max-Min Fairness Multipath Flow Control

Many rate allocation algorithms for multipath flows which satisfy max-min fairness are centralized and not scalable. Upward max-min fairness is a well-known relaxation of max-min fairness and can be achieved by an algorithm extended from water-filling algorithm. In this paper, we propose a price-based multipath congestion control protocol whose equilibrium point satisfies upward max-min fairness. Our protocol is derived from a network utility maximization model for multipath flows.

     

Interactions Between Routing and Flow Control Algorithms

In this paper we discuss the interactions between routing and flow control algorithms for packet-switched networks. We present a new variation on the Gallager-Golestaani flow control scheme [4] and also a new variable window scheme. The tradeoff between throughput and network congestion is examined. It is shown that these two flow control schemes have the unique feature that the parameters can be specified to place an upper bound on the expected amount of network congestion.     

Fairness and Dynamic Flow Control in Both Unicast and Multicast Architecture Networks

With the development of multicast service in the Internet, much attention has been drawn to multicast congestion control and analysis. Multicast traffic poses new challenges to the design of Internet congestion control protocols and system stability analysis. The rate control problem of feedback-based sessions on the coexistence of both unicast and multirate multicast traffic architecture networks is focused upon in this paper. First, a fairness problem is discussed in detail, and a reasonable consumption strategy is proposed. In the reasonable consumption strategy, scaling functions are adaptively adjusted based on a relationship between the session rates. Second, contraposing the case that available link capacities are changing with time for these feedback-based unicast and multicast sessions, stability analysis of a closed-loop rate control system under the modified rate mechanism is made based on Lyapunov stable theory. Finally, the simulations illustrate the effectiveness and goodness of the reasonable consumption strategy     

RPS类流量调度与成形算法中worst-case公平性能分析

RPS类流量调度算法由于具有理想的延时性能，在具有QoS要求的调度算法中该类算法被广泛应用。为了使该类算法同时具有较好的公平性，将该算法与流量成形机制相结合(SRPS)，即可得到理想的Worst-case公平指数(WFI)。在现有文献中部认为SRPS算法具有与WF^2Q相同WFI，本文在分析RPS算法的基础上，重新给出了SRPSworst-case表达式，指出SRPS算法具有比RPS算法理想的公平性能，但还没有达到与WF^2Q相同的Worst-case公平指数。     

弹性分组环中公平算法的研究

本文深入分析了目前应用于弹性分组环(RPR,Resilient Packet Ring)中的一些公平算法,指出了目前的算法所存在的一些问题。并根据相关的研究工作,讨论了有待于进一步研究的课题。     

Fundamentals of Fast Simulation Algorithms for RF Circuits

Designers of RF circuits such as power amplifiers, mixers, and filters make extensive use of simulation tools which perform periodic steady-state analysis and its extensions, but until the mid 1990s, the computational costs of these simulation tools restricted designers from simulating the behavior of complete RF subsystems. The introduction of fast matrix-implicit iterative algorithms completely changed this situation, and extensions of these fast methods are providing tools which can perform periodic, quasi-periodic, and periodic noise analysis of circuits with thousands of devices. Even though there are a number of research groups continuing to develop extensions of matrix-implicit methods, there is still no compact characterization which introduces the novice researcher to the fundamental issues. In this paper, we examine the basic periodic steady-state problem and provide both examples and linear algebra abstractions to demonstrate connections between seemingly dissimilar methods and to try to provide a more general framework for fast methods than the standard time-versus-frequency domain characterization of finite-difference, basis-collocation, and shooting methods     

视觉光流计算技术及其应用

视觉光流计算是计算机视觉从处理2维图像走向加工3维视频的重要技术手段,是描述视觉运动信息的主要方式。光流计算技术已经发展了较长的时间,随着相关技术尤其是深度学习技术在近些年的迅速发展,光流计算的性能得到了极大提升,但仍然有大量的局限性问题没有解决,准确、快速且稳健的光流计算目前仍然是一个有挑战性的研究领域和业内研究热点。光流计算作为一种低层视觉信息处理技术,其技术进展也将有助于相关中高层级视觉任务的实现。该文主要内容是介绍基于计算机视觉的光流计算及其技术发展路线,从经典算法和深度学习算法这两个主流技术路线出发,总结了技术发展过程中产生的重要理论、方法与模型,着重介绍了各类方法与模型的核心思想,说明了各类数据集及相关性能指标,同时简要介绍了光流计算技术的主要应用场景,并对今后的技术方向进行了展望。     

弹性分组环公平性算法的FPGA设计

随着弹性分组环的广泛使用，公平有效地利用有限的带宽资源尤为重要。文章主要介绍了公平性算法的FPGA设计，使其具有现实意义。     

Guest Editorial: Networking, Sensing, and Control for Networked Control Systems: Architectures, Algorithms, and Applications

The eight papers in this special issue focus on networking, sensing, and control for networked control systems (NCS). The papers, which are briefly summarized, examine the architectures, algorithms and applications of NCS.     

Multiuser Capacity and Fairness Evaluation of Channel/QoS-Aware Multiplexing Algorithms

In this work multiplexing of variable-rate sources over shared generic multiple fading channels is addressed. In general, the performance of existing multiplexing algorithms has been compared in very specific environments, making it difficult to draw general conclusions. In this article we propose a generic variable-rate multiuser and multichannel system model that can be applied to any orthogonal channel multiplexing mechanism (e.g., TDM, OFDM, CDM, or SDM) through parametric modeling. Based on the model, the performance of different multiplexing algorithms proposed in the literature is evaluated over moderately fast fading snared channels. Physical channel conditions, random traffic arrival, and QoS requirements are taken into consideration in the study. Multiuser capacity and fairness are assessed and evaluated for different channel-aware and/or QoS-aware user multiplexing algorithms. Results show the joint diversity gain and QoS in terms of the throughput and delay experienced by different user information flows     

TCP拥塞控制的公平性研究

针对目前Internet中TCP拥塞控制和式增加、积式减小和窗口变化机制,分析了TCP流量控制带宽分配的公平性问题。     

基于RPR MAC的公平性算法研究

主要讨论弹性分组环网中的公平性算法,对现有的公平性算法进行了分类和比较研究,分析了其性能指标和技术特点,最后讨论它的发展趋势。     

Fairness and Optimal Stochastic Control for Heterogeneous Networks

We consider optimal control for general networks with both wireless and wireline components and time varying channels. A dynamic strategy is developed to support all traffic whenever possible, and to make optimally fair decisions about which data to serve when inputs exceed network capacity. The strategy is decoupled into separate algorithms for flow control, routing, and resource allocation, and allows each user to make decisions independent of the actions of others. The combined strategy is shown to yield data rates that are arbitrarily close to the optimal operating point achieved when all network controllers are coordinated and have perfect knowledge of future events. The cost of approaching this fair operating point is an end-to-end delay increase for data that is served by the network.     

Joint Congestion Control, Routing, and MAC for Stability and Fairness in Wireless Networks

In this paper, we describe and analyze a joint scheduling, routing and congestion control mechanism for wireless networks, that asymptotically guarantees stability of the buffers and fair allocation of the network resources. The queue-lengths serve as common information to different layers of the network protocol stack. Our main contribution is to prove the asymptotic optimality of a primal-dual congestion controller, which is known to model different versions of transmission control protocol well.     

弹性分组环基于流的公平算法的研究

IEEE802．17弹性分组环是宽带城域网的新型技术。凭着本地公平算法、空间重利用、带宽统计复用、正常状态双环均传输业务等特点从而和传统环网相比,弹性分组环在带宽利用方面具有较大的优势。公平算法对弹性分组环发挥其带宽利用优势具有极其重要的作用,而目前的基于节点公平算法不能完全发挥弹性分组环的优势。文章在更能发挥弹性分组环带宽利用优势的基于流的公平策略的基础上,建立相应的算法方案,并进行计算机仿真验证。实验结果验证了理论分析。     

有源噪声控制的前馈/反馈混合算法

有源噪声控制广泛应用于低频噪声控制，针对不同噪声信号使用前馈算法、反馈算法和前馈/反馈混合算法（简称混合算法）进行仿真，并在以扬声器和风机为噪声源的实验系统上进行实验验证，结果表明混合算法在仿真和实际中具有更快的收敛性和更好的抗噪声效果。     

PMIMD拥塞控制算法

分析了目前在Internet上占主导地位的AIMD算法，指出了其在保持数据流稳定性上的不足，这一缺点不能适应当前的媒流体文件传输；提出了一种新的算法--PMIMD（比例乘性增加乘性减少）。仿真结果表明，本算法能减少控制的超调量，从而降低传输率的波动。     

Defective Photocathode: Fundamentals,Construction, and Catalytic Energy Conversion

The development of a long-term and sustainable energy economy is one of the most significant technological challenges facing humanity. Photoelectrochemical (PEC) technology is considered as the most attractive route for converting solar energy into chemical energy. However, the slow reaction kinetics of PEC oxidation and reduction greatly hinder its practical application. To address this issue, engineering photoelectrodes with various defects can significantly improve their catalytic performance, which can not only regulate catalyst electronic structure but also promote charge transfer/separation by serving as an active/adsorption/energy storage site. Herein, the defect engineering strategies for photoelectrodes are systematically summarized, focusing on the latest progress in defective photocathode for energy conversion. First, an overview of defect types, basic principles of photocathode, and the positive role of defects in the photocathode are provided. Second, the construction strategies and characterization methods of defective photocathode are summarized. Then, the progress of typical energy conversion applications, including hydrogen production, CO₂ reduction, and nitrogen reduction over defective photocathode, is reviewed, highlighting the crucial role of defects in high catalytic performance. Finally, the challenges and future prospects of defective photocathode are discussed, aiming to bring new opportunities for the development of photocathode through defect engineering.     

Proportional Fairness in Multi?Carrier System with Multi?Slot Frames: Upper Bound and User Multiplexing Algorithms

Optimal Proportional Fair Scheduling (PFS) in a multi-carrier system is a prohibitively complex combinatorial problem. In this paper we consider practical time frames with multiple time slots, where this optimal allocation becomes even more complex. Therefore, we derive bounds for the optimal proportional fair allocation, by means of convex optimization, and propose approximation algorithms where several users can be time-multiplexed on a same subchannel. With a much lower complexity than the optimal allocation, these algorithms achieve an excellent tradeoff between throughput and proportional fairness, even with the increased signaling overhead.