Daniel Reininger

Statistical multiplexing of VBR MPEG compressed video on ATM networks

A variable-bit-rate (VBR) MPEG video compression encoder is introduced, and the performance of a statistically multiplexed asynchronous transfer mode (ATM) network supporting a number of such VBR video sources is evaluated. Bit-rate characteristics obtained from a detailed simulation are provided for a VBR MPEG encoder for CCIR601 video (operating in the 5-10 Mb/s regime) appropriate for medium-quality multimedia or broadcasting applications. The results presented include bit-rate traces and signal-to-noise-ratio data for typical test sequences, along with summary statistics such as the marginal distribution of frame rate. Data from a study of statistical multiplexing on an ATM network are also given. Simulation results for an ATM statistical multiplexer with N>>1 VBR MPEG sources are presented in terms of key performance measures such as cell loss rate and delay versus throughput. The results confirm that ATM channel efficiencies of approximately 80-90% can be obtained at reasonable cell loss rate and delay levels.<<ETX>>

Bandwidth renegotiation for VBR video over ATM networks

A scheme for delivery or variable bit-rate (VBR) video over asynchronous transfer mode (ATM) networks where bandwidth can be renegotiated during the duration of a call between the video source and the network is considered. Renegotiation can be initiated by either the video source or the network. The video bandwidth requirement is characterized by a usage parameter control (UPC) consisting, in general, of peak rate, burst length, and sustained rate. A baseline design is outlined where rate-control adjusts the sources rate while a new UPC is requested from the network. When granted, the new UPC allows the source to maintain its target quantization and delay requirements. Rate control epochs may be extended when the network blocks UPC requests or sets a lower UPC value to temporally deal with congestion. Simulation results are presented for VBR MPEG video. The results show that with a moderate renegotiation rate the scheme tracks the bandwidth requirements of the source. As a result, the video quality and bandwidth efficiency can be maintained.

Paying for QoS: an optimal distributed algorithm for pricing network resources

Network applications require certain individual performance guarantees that can be provided if enough network resources are available. Consequently, contention for the limited network resources may occur. For this reason, networks use flow control to manage network resources fairly and efficiently. This paper presents a distributed microeconomic flow control technique that models the network as competitive markets. In these markets, switches price their link bandwidth based on supply and demand, and users purchase bandwidth so as to maximize their individual quality of service (QoS). This yields a decentralized flow control method that provides a Pareto optimal bandwidth distribution and high utilization (over 90% in simulation results). Discussions about stability and the Pareto optimal distribution are given, as well as simulation results using actual MPEG-compressed video traffic.

An architecture for adaptive QoS and its application to multimedia systems design

We describe a prototype implementation of a distributed multimedia system that generalizes the concept of QoS to all layers of its software architecture. Each layer deals with QoS at its appropriate level of abstraction using a generic API for communicating QoS parameters and values to layers above and below. The aggregation of these parameters and values is called a service contract. This architecture provides a hierarchical framework to design adaptive multimedia systems. Furthermore, the API allows for reporting of contract violations as well as dynamic renegotiation of the contract terms. A proof-of-concept multimedia system was built to evaluate the proposed architecture. Key components of this system are: a graphical user interface that dynamically requests the quality expected by the user to lower level components, a dynamic network service that efficiently matches network resources to user requirements and a processor scheduler which schedules tasks according to their execution requirements. Our experience with this system showed that the proposed architecture is an efficient framework for building adaptive multimedia systems.

VBR MPEG video coding with dynamic bandwidth renegotiation

A scheme for VBR video coding is proposed where encoding bandwidth can be renegotiated between the encoder and the network during the duration of a call. Renegotiation can be initiated by either the encoder or the network. The encoders bandwidth requirement is characterized by a usage parameter control (UPC) set consisting of peak rate, burst length and sustained rate. An adaptive encoder rate-control algorithm at the network interface card (NIC) computes the necessary UPC parameters to maintain the user specified quality-of-service (QoS). The network may, optionally, set a lower UPC value to deal with congestion. Simulation results are given for a rate-controlled VBR video encoder operating through an ATM network interface which supports dynamic UPC. These results suggest that dynamic band-width renegotiation could provide significant quality gains and/or bandwidth savings with graceful degradation during renegotiation transients, even in the presence of relatively large feedback delay.

Multichannel joint rate control of VBR MPEG encoded video for DBS applications

A method to transmit multiplexed digital video that potentially allows for video quality and capacity gains over conventional constant bit-rate (CBR) transmission is described. The method uses a joint rate control algorithm that regulates the encoders during buffer congestion periods using bandwidth re-allocation and source rate control. A multichannel joint rate control algorithm is described and its performance simulated for MPEG encoded video on broadcast satellite (DBS) application. Results indicate significant capacity and/or quality gains over conventional CBR transmission methods. >

A dynamic quality of service framework for video in broadband networks

A dynamic framework for QoS control of video in distributed multimedia applications is presented. The framework allows flexible and efficient video delivery with application-level QoS support. Key components of the framework are client QoS renegotiation, server source rate control, and dynamic bandwidth allocation. The coordinated functionality of these distributed components provides soft QoS to adaptive applications. A proof-of-concept prototype of a video browser with user-level control of soft QoS is implemented within the proposed framework. The implementation uses a distributed software architecture that represents soft QoS requirements by software objects called service contracts. These objects are exchanged among servers, network nodes, and clients to achieve distributed soft QoS control. Experiences with the prototype and its performance are discussed.

UPC based bandwidth allocation for VBR video in wireless ATM links

This paper presents a medium access level VBR bandwidth allocation scheme for wireless ATM (WATM) networks. After introducing a wireless ATM system model and the associated dynamic TDMA/TDD medium access control (MAC) scheme, an algorithm for VBR slot allocation is proposed. The algorithm combines information from user parameter control (UPC) at the call admission control (CAC) level with rapid MAC level estimates of the requirements for each VBR virtual circuit (VC). The method described is applicable to both conventional VBR and VBR+ in which UPC parameters are dynamically renegotiated as source bit rate requirements vary. Simulation experiments using statistically multiplexed MPEG-1 video are carried out for a typical 25 Mbps dynamic TDMA/TDD wireless ATM access link scenario. Experimental results show that, for the VBR video under consideration, the proposed scheme can achieve throughputs in the range of 60-70% while maintaining reasonable QoS.

Bit-rate characteristics of a VBR MPEG video encoder for ATM networks

The authors present the bit-rate characteristics of variable bit-rate (VBR) MPEG-1 compatible video intended for asynchronous transfer mode (ATM) network applications. The VBR coding mode for MPEG video is of special interest in teleconferencing and workstation multimedia applications requiring constant image quality, low delay, and/or integrated multimedia transport. Simulation data are provided for a 5-10 Mbps CCIR601 VBR MPEG encoder appropriate for standard-quality TV broadcasting or multimedia applications. The results presented include bit-rate traces and signal-to-noise ratio for typical test sequences, along with summary bit-rate statistics. The performance of frame-based peak rate control as a traffic shaping method is studied. Signal-to-noise ratio obtained with VBR and constant bit-rate coding modes operating at the same average bit-rate is also given for purposes of comparison.<<ETX>>

Market based bandwidth allocation policies for QoS control in broadband networks

Efficient quality-of-service (QoS) control in broadband networks requires dynamic bandwidth allocation. This paper formulates a distributed and hierarchical QoS control scheme that dynamically allocates bandwidth based on a market model. The market players are consumers, retailers and wholesalers. Consumers trade bandwidth with retailers, and retailers trade with wholesalers. The market price for bamdwidth fluctuates based on demand and consumers’ price sensitivib (estimated from past transactions). For a given price, consumers opt-tie bandwidth demand Us-mg their individual cost-benefit (ut-tity) functions. In the case of mult-hnedia applications’, a ‘softness” proiile describes the application’s robustness to network congestion. Simulations using hIPEG2 vaiiable bit-rate (VBR) video are used to evaluate the ability of the scheme to effectively provide QoS to applications and, at the same time, provide a framework to price networked multimedia services with heterogeneous traflic and QoS requirements. Key wor& quality-of-seruice, softness profdss, marketlmsed wnhl, MPEG video, broadband service pricing.