Evolution of controls for the available bit rate service

In the summer of 1993, the asynchronous transfer mode (ATM) community began a search for a mechanism to allocate bandwidth dynamically within an ATM network, while simultaneously preventing data loss. By the fall of 1994, the ATM Forum had introduced a new service category for this purpose, the available bit rate (ABR) service, and had selected a rate-based mechanism for its support. Simply put, the mechanism would consist of a stream of ABR resource management (RM) cells, generated by one end of the connection (the source) and looped back by the other (the destination), into which switches would encode the maximum rate at which the ABR source was to generate data. The ABR service is an addition to ATM that uses a feedback mechanism to control the transmission rates of traffic sources. Although the performance of the ABR service will depend critically on the quality of feedback sent by switches, the algorithms for determining this feedback are largely outside the scope of ATM standards and specifications. We describe how two of the properties implemented by the ABR source and destination, out-of-rate RM cells and a use-it-or-lose-it policy, were implicitly architectural decisions, and we explain how and why the ATM Forum ultimately revised these decisions. We then discuss how the ATM Forum addressed the issues of conformance testing, point-to-multipoint connections, and parameter negotiation for the ABR service. At the end, we reflect on the process by which the ABR specification was developed     

The available bit rate service for data in ATM networks

The authors describe the purpose of the available bit rate (ABR) service in the context of other ATM services and review the agreements on the traffic control mechanism. They describe the recent progress towards standardization of the new service. The general nature of the ABR service is described in comparison with constant bit rate (CBR) and variable bit rate (VBR) services     

A congestion control framework for available bit rate service in ATM networks

Fair packet discarding (FPD) is a mechanism which provides incentives to users to co‐operate in congestion control, so that ATM networks can operate more efficiently. In this paper, we propose a simple congestion control framework consisting of a combination of FPD and ATM Forum's explicit‐rate flow control scheme. We show by simulations that this frame‐work achieves all objectives of congestion control: (1) control congestion, (2) achieve high user‐perceived throughput, (3) maintain fairness and (4) provide protection from misbehaving users. In addition, we equip this framework with two enhancements to improve efficiency, and reduce end‐to‐end delay. Copyright © 2002 John Wiley & Sons, Ltd.     

The rate-based flow control framework for the available bit rateATM service

A new ATM service category, the available bit rate service, is currently the subject of intense development. This new service will systematically and dynamically allocate available bandwidth to users by controlling the flow of traffic with feedback. The rate-based flow control framework has been identified as the most appropriate for the support of this new service     

Optimal bit allocation for coding of video signals over ATMnetworks

We consider optimal encoding of video sequences for ATM networks. Two cases are investigated. In one, the video units are coded independently (e.g., motion JPEG), while in the other, the coding quality of a later picture may depend on that of an earlier picture (e.g., H.26x and MPEGx). The aggregate distortion-rate relationship for the latter case exhibits a tree structure, and its solution commands a higher degree of complexity than the former. For independent coding, we develop an algorithm which employs multiple Lagrange multipliers to find the constrained bit allocation. This algorithm is optimal up to a convex-hull approximation of the distortion-rate relations in the case of CBR (constant bit-rate) transmission. It is suboptimal in the case of VBR (variable bit-rate) transmission by the use of a suboptimal transmission rate control mechanism for simplicity. For dependent coding, the Lagrange-multiplier approach becomes rather unwieldy, and a constrained tree search method is used. The solution is optimal for both CBR and VBR transmission if the full constrained tree is searched. Simulation results are presented which confirm the superiority in coding quality of the encoding algorithms. We also compare the coded video quality and other characteristics of VBR and CBR transmission     

Design of a fair bandwidth allocation policy for VBR traffic in ATMnetworks

Since real-time variable bit rate (VBR) traffic is inherently bursty, dynamic bandwidth allocation is necessary for ATM streams that carry VBR traffic. In order to provide quality-of-services (QoS) guarantees and to reduce the computational complexity, an hybrid of guaranteed and dynamic adaptive allocation scheme requires to be implemented. Typical dynamic allocations to competing streams are done in the form of linear proportions to the bandwidth requirements. We show that during temporary link congestion such proportional arrangements can give rise to unequal queue growth and, subsequently, degraded QoS. This is found to be true even for streams that belong to the same VBR class and share identical long term traffic characteristics and QoS requirements. In this paper, four allocation algorithms are presented and analyzed in terms of their fairness and QoS potential for real-time VBR traffic. We propose and show that a novel allocation strategy, termed Minmax, solves the mentioned problem of unfairness within a class. By maintaining a fair distribution of buffer length across the streams of a class, the proposed policy can achieve better and fairer QoS performance compared to the traditional methods. We present analytical results, proofs and a simulation study of the described algorithms. Four allocation policies for handling MPEG VBR video streams are simulated in the context of a wireless ATM (WATM) medium access control. The results show that in certain scenarios, the Minmax strategy can reduce losses by an order of magnitude, while decreasing delays substantially     

Efficient consolidation algorithm for multicast ABR service in ATMnetworks

A new efficient consolidation algorithm at a branch-point switch for multicast available bit rate (ABR) service is proposed. The scheme can achieve a faster response to congestion status and has a lower consolidation noise compared with existing algorithms. Particularly network environments with a large number of branch points     

Evaluation of the virtual source/virtual destination-technique for available bit rate traffic in ATM-networks

This paper deals with the performance analysis of the Virtual Source / Virtual Destination (vs/vd) technique for abr flow control. The vs/vd mechanism allows the segmentation of the abr end-to-end feedback loop. We will investigate the behaviour and performance of classical Explicit Rate switch algorithms in conjunction with vs/vd and will give recommendations for improvements and alterations. The analysis is based on simulations of different network topologies and traffic scenarios.     

Fair queueing algorithm with rate independent delay for ATMnetworks

A new scheduling algorithm based on self-clocked fair queueing is proposed. The algorithm employs an array of sorting bins for managing the virtual finishing time of connections and uses token buckets as a behaviour-indicator. It remedies the drawbacks of existing fair queueing algorithms and is able to reserve bandwidth to connections while guaranteeing a class-dependent and rate-independent delay for behaving connections     

H.263甚低码率视频编码标准的码率控制方法

主要提出ＩＴＵ组织的Ｈ．２６３甚低码率视频压缩编码标准输出码率的控制方案。着重分析了一种通过调整宏观量化器的量化参数来控制Ｈ．２６３编码器输出码率的方法,它能满足在ＰＳＴＮ网上低时延中的码率输出要求。     

On max-min fair congestion control for multicast ABR service in ATM

In the ATM Forum activities, considerable efforts have focused on the congestion control of point-to-point available bit rate (ABR) service. We present a novel approach that extends existing point-to-point (unicast) congestion control protocols to a point-to-multipoint (multicast) environment. In particular, we establish a unified framework to derive a multicast congestion control protocol for an ABR service from a given rate-based unicast protocol. We generalize a known necessary and sufficient condition on the max-min fairness of unicast rate allocation for a multicast service. Using this condition, we show that the resulting multicast protocol derived using our framework preserves the fairness characteristics of the underlying unicast protocol. The practical significance of our approach is illustrated by extending a standard congestion control mechanism for an ABR service to a multicast environment. The performance of the resulting multicast protocol is examined using benchmark network configurations suggested by the traffic management subworking group at the ATM Forum, and simulation results are presented to substantiate our claims     

End-to-end fair rate optimization in wired-cum-wireless networks

In this paper, we address the end-to-end rate optimization problem in a wired-cum-wireless network, where CSMA/CA based wireless LANs extend a wired backbone and provide access to mobile users. The objective is to achieve proportional fairness amongst the end-to-end sessions in the network. Since the network contains wireless links whose attainable throughput is a (non-convex and non-separable) function of MAC protocol parameters, the problem requires joint optimization at both the transport and the link layers. A dual-based algorithm is proposed in this paper to solve this cross-layer rate optimization problem. It is implemented in the distributed manner, and works at the link layer to adjust scheduling rates for the wireless links in the basic service sets, and at the transport layer to adjust end-to-end session rates. We prove rigorously that the proposed algorithm converges to the globally optimal rates. Simulation results are provided to support our conclusions.     

Energy efficiency and quality of service optimization for constant bit rate real‐time applications in 802.11 networks

In this paper, we propose a quality of service (QoS)‐sensitive energy efficiency optimization mechanism for 802.11 networks on the basis of the dynamic and simultaneous adjustment of the content window (W) and retry attempts limit (r) of the media access control (MAC) sublayer. The use of both operational variables let us not only find the optimum operational point regarding energy efficiency but also attain a positive impact on the QoS, which improves the results obtained with current single‐variable optimization strategies. The model under consideration includes external noise and does not impose the saturation condition in stations and as such is well suited for real‐time industrial applications under noisy channels. Results obtained from simulation confirm the advantages of adjusting simultaneously W and r versus adjusting either one separately, obtaining a slight improvement in energy efficiency and resulting in less loss and delay at the MAC sublayer. Copyright © 2012 John Wiley & Sons, Ltd.     

Suggested new bit rates for ITU-T G.723.1

A 4.5/3.9 kbit/s coder modified from the ITU standard G.723.1 is presented. Owing to the ease of modification and comparable speech quality, it is suggested that the new rates be incorporated in the standard as new options for rate selection     

Reduced bit rate uniform quantisation for SPIHT encoding

Set partitioning in hierarchical trees (SPIHT) is a scalar quantiser for images that have undergone subband decomposition by wavelet transform. Reduced bit rates have been achieved by merging the first and second passes of the already efficient SPIHT algorithm. The modification requires neither entropy encoding nor significant increase to the algorithmic complexity.     

MPEG coding for variable bit rate video transmission

For real-time transmission of broadcast-quality video on ATM-based B-ISDN, the intraframe to interframe ratio and the quantizer scale are two key parameters that can be used to control a video source in a network environment. Their impact on the traffic characteristics of the coder provides insights into the cell arrival process for an MPEG source. The authors obtain video source models for coders that utilize a standard algorithm that can be applied to a multitude of video services. The output stream of a video coder, which complies with the Motion Pictures Expert Group (MPEG) coding standard, is studied with an National Television Systems Committee (NTSC) quality video sequence as the input. Because the MPEG video coding algorithm has been proposed for a variety of applications, they also investigate the effect of changing the coding parameters on the statistics of interest     

A neurocomputing controller for bandwidth allocation in ATMnetworks

We propose a new neurocomputing call admission control (CAC) algorithm for asynchronous transfer mode (ATM) networks. The proposed algorithm employs neural networks (NNs) to calculate the bandwidth required to support multimedia traffic with multiple quality-of-service (QoS) requirements. The NN controller calculates the bandwidth required percall using on-line measurements of the traffic via its count process, instead of relying on simple parameters such as the peak, average bit rate and burst length. Furthermore, to enhance the statistical multiplexing gain, the controller calculates the gain obtained from multiplexing multiple streams of traffic supported on separate virtual paths (i.e., class multiplexing). In order to simplify the design and obtain a small reaction time, the controller is realized using a hierarchical structure of a bank of small size, parallel NN units. Each unit is a feed-forward back-propagation NN that has been trained to, learn the complex nonlinear function relating different traffic patterns and QoS, with the corresponding received capacity. The reported results prove that the neurocomputing approach is effective in achieving more accurate results than other conventional methods that are based upon mathematical or simulation analysis. This is primarily due to the unique learning and adaptive capabilities of NNs that enable them to extract and memorize rules from previous experience. Evidently such unique capabilities poise NNs to solve many of the problems encountered in the development of a coherent ATM traffic management strategy     

Introduction of very high bit rates for NFC and RFID

This article gives a detailed insight into the very high bit rates (VHBR) technology for the data transfer with NFC and RFID. In the first part enhancements and changes to the ISO/IEC 14443 and related standards are discussed. In the second part an analysis of different bit rates with focus on communication parameters and bit error rates are provided.     

Adaptive coding of moving objects for very low bit rates

This paper describes an object-based video coding system with new ideas in both the motion analysis and source encoding procedures. The moving objects in a video are extracted by means of a joint motion estimation and segmentation algorithm based on the Markov random field (MRF) model. The two important features of the presented technique are the temporal linking of the objects, and the guidance of the motion segmentation with spatial color information. This facilitates several aspects of an object-based coder. First, a new temporal updating scheme greatly reduces the bit rate to code the object boundaries without resorting to crude lossy approximations. Next, the uncovered regions can be extracted and encoded in an efficient manner by observing their revealed contents. The objects are classified adaptively as P objects or I objects and encoded accordingly. Subband/wavelet coding is applied in encoding the object interiors. Simulations at very low bit rates yielded comparable performance in terms of reconstructed PSNR to the H.263 coder. The object-based coder produced visually more pleasing video with less blurriness and devoid of block artifacts, thus confirming the advantages of object-based coding at very low bit-rates     

In-band clock distribution concept for ultra-high bit rates OTDM system

A novel clock distribution concept based on inband phase-modulated pilot insertion is demonstrated.This method avoids the need for an ultrafast phase comparator and a phase-locked loop in the receiver.Experimental results show that the clock can be successfully extracted from 160Gbit/s optical time-division multiplexing (OTDM) data signal and employed for demultiplexing of 40Gbit/s tributaries.The in-band clock distribution introduces 1.5dB of power penalty with an error-free performance.