CCITT H.261 compatible mixed bit rate coding of video for ATM networks

The arrangement of data in a variable bit rate (VBR) video codec, making it suitable for the transmission over ATM (asynchronous transfer mode) networks, is addressed. Attention is focused on two aspects specifically belonging to the ATM environment: the impairment due to the loss of ATM data cells and the statistical analysis of a real VBR video source. A particular implementation of a hybrid DCT (discrete cosine transform) broadcast video codec, which adheres to the recent specifications proposed by the European Telecommunications Standards Institute, is addressed. In order to optimize the performance with respect to cell losses, a specific solution based on the concept of organizing data into video packets is explored. The statistical characteristics of the available VBR video source are investigated, using a real-time acquisition system. >

For distinctively transporting voice data with silence suppression over asynchronous transfer mode (ATM) networks via the variable bit rate (VBR) service, the problem of jitter introduced from the network often renders the speech unintelligible. It is thus indispensable to offer intramedia synchronization to remove jitter while retaining minimal playout delay. We propose a neural-network-based intra-voice synchronization mechanism, called the intelligent voice smoother (IVoS). The IVoS is composed of three components: smoother buffer, neural network (NN) traffic predictor, and constant bit rate (CBR) enforcer. Newly arriving frames, being assumed to follow a generic Markov modulated Bernoulli process (MMBP), are queued in the smoother buffer. The NN traffic predictor employs an on-line-trained backpropagation neural network (BPNN) to predict three traffic characteristics of every newly encountered talkspurt period. Based on the predicted characteristics, the CBR enforcer derives an adaptive buffering delay by means of a near-optimal, simple, closed-form formula. It then imposes such delay on the playout of the first frame in the talkspurt period. The CBR enforcer in turn regulates CBR-based departures for the remaining frames of the talkspurt, aimed at assuring minimal mean and variance of distortion of talkspurts (DOT) and mean playout delay (PD). Simulation results reveal that, compared to three other playout approaches, the IVoS achieves superior playout yielding negligible DOT and PD irrespective of traffic variation.

This paper presents a general traffic control framework for Asynchronous Transfer Mode (ATM) networks with its performance evaluation. The proposed traffic control scheme can incorporate all the recently considered ATM service classes including Constant Bit Rate (CBR), real time Variable Bit Rate (rtVBR), non-real time Variable Bit Rate (nrVBR), Available Bit Rate (ABR) and Unspecified Bit Rate (UBR) services. The control is based on a complete buffer partitioning architecture and on the associated buffer scheduling rule with adaptive weighting functions. We present, the formulation of the traffic control as an optimization problem in a 3-dimensional Quality of Service (QoS) state space. A solution approach based on dynamic programming is also suggested. A comprehensive performance evaluation of the method has been performed based on simulations and results are presented with several examples. The QoS dependence on CBR load, VBR load, VBR burstiness, UBR load are investigated and results are demonstrated with explanations.

A fuzzy approach to MPEG video transmission in ATM networks

In recent years, there has been a strong interest in transmitting compressed video over packet switched networks, such as asynchronous transfer mode (ATM). Previous work has dealt with transmitting MPEG over constant bit rate (CBR) and variable bit rate (VBR) services of ATM. The available bit rate (ABR) service of ATM is expected to be much more cost effective than CBR or VBR. However, there hasn't been much work done on running interactive client/server applications (for example, video on demand) over ABR. We have developed a framework to design interactive video systems transmitting MPEG video over the ATM ABR service. We have developed models to determine the network connection parameters required to run interactive client/server multimedia applications over an ATM network using the ABR service. We solve our model using real-time dynamic equilation (RTDE) analysis. We conclude that by proper dimensioning of the buffers at the client and the server, it is possible to run interactive video over the ATM ABR service.

Video traffic is expected to account for a significant share of the traffic volume in future asynchronous transfer mode (ATM) networks. MPEG-2, proposed by the Moving Picture Expert Group, is one of the most promising compression techniques for such applications. One of the critical issues in MPEG-2 is to realize effective variable bit rate (VBR) video transfer thorough ATM networks. The leaky bucket (LB) scheme has been widely accepted as the usage parameter control (UPC) mechanism to police the VBR sources. We propose a new adaptive dynamic leaky bucket (ADLB) congestion control mechanism, which is based on the LB scheme. Unlike the conventional LB, the leak rate of the ADLB is controlled using delayed feedback information of available bandwidth sent by the network. The simulation results show that overall cell loss and delay are reduced significantly at the ATM switch node.

The quality of service (QoS) performance of wireless multiple access to an asynchronous transfer mode (ATM) network is investigated. Multiple access is implemented using a polling strategy with nonpreemptive priority to handle constant bit rate (CBR), variable bit rate (VBR) and available bit rate (ABR) services. Sufficient conditions are derived for all CBR sources to satisfy their jitter constraints and all VBR sources to their delay constraints. Under these conditions, tight analytical bounds are derived.

Video traffic is expected to account for a significant share of the traffic volume in the future asynchronous transfer mode (ATM) networks. MPEG-2 proposed by Moving Picture Expert Group is one of the most promising compression techniques for such applications. One of the critical issues in MPEG-2 is to realize effective variable bit rate (VBR) video transfer thorough ATM networks. The Leaky Bucket (LB) scheme has been widely accepted as the usage parameter control (UPC) mechanism to police the VBR sources. We proposed a new Adaptive Dynamic Leaky Bucket (ADLB) congestion control mechanism, which is based on the LB scheme. Unlike the conventional LB, the leak rate of the ADLB is controlled using delayed feedback information of available bandwidth sent by the network. This scheme allows sources to get varying amounts of bandwidth over time, while reserving a minimum guaranteed bandwidth (MCR) for the entire duration of the connection. At the time of congestion, the leak rate of the ADLB is adjusted according to the feedback indicating the currently available bandwidth to the connection. The simulation results show that the end-to-end cell transfer delay and cell loss of each source has been improved significantly.

In recent years, there has been a strong interest in transmitting compressed video over packet switched networks, such as asynchronous transfer mode (ATM). Previous work has dealt with transmitting MPEG over constant bit rate (CBR) and variable bit rate (VBR) services of ATM. The available bit rate (ABR) service of ATM is expected to be much more cost effective than CBR or VBR. However, there hasn't been much work done on running interactive client/server applications (for example, video on demand) over ABR. We have developed a framework to design interactive video systems transmitting MPEG video over the ATM ABR service. We have developed models to determine the network connection parameters required to run interactive client/server multimedia applications over an ATM network using the ABR service. We solve our model using real-time dynamic equilation (RTDE) analysis. We conclude that by proper dimensioning of the buffers at the client and the server, it is possible to run interactive video over the ATM ABR service.

The Asynchronous Transfer Mode (ATM) technology is reaching a considerable level of acceptance in many contexts. One of the key characteristics of ATM is the ability to provide statistical guarantees on performance. In other words, each user has to agree with the network on a set of parameters identifying the connection characteristics (e.g. Traffic Type, Rate, Quality of Service -QoS- parameters, etc.) which will be guaranteed by the network in case the call is accepted. Real-time video applications are foreseen as one of the major users of B-ISDN. In particular the ability of the network to manage variable bit rate (VBR) traffic can be conveniently exploited by compressed video transmission systems. More precisely, with respect to the constant bit rate (CBR) video-codec, the quality of decoded signal can be kept more stable and statistical multiplexing scheme can be used in multi-channel video distribution systems for a more efficient bandwidth utilisation.

Many studies have been conducted involving the transport of constant and variable bit rate MPEG-2 video in asynchronous transfer mode (ATM) networks; however, many of these studies have considered fairly homogeneous scenarios in which the only other traffic present in the ATM network, if any, are other MPEG-2 video sources. In this study the requirements of supporting MPEG-2 video communications in an ATM network under unloaded and heavily loaded network conditions, in which the generated traffic sources are bursty in nature, are considered. To complete the study an experimental video on demand (VoD) testbed, developed as part of a collaborative research effort between the Communications Research Center of Canada (CRC), Nortel and the University of Ottawa, was employed. To determine the characteristics of the MPEG-2 video traffic generated by the VoD application in the ATM network in the presence of other traffic, cell interarrival time measurements and cell rate snapshots at the ATM cell level were considered. Results obtained show that the end-to-end flow control implemented in the application layer in the video-on-demand (VoD) system and the traffic controls implemented intermediate network elements (e.g., routers, switches) have significant impacts on the characteristics of the MPEG-2 traffic carried in the ATM network. Moreover, the impact of the intermediate network elements on the characteristics of the MPEG-2 traffic increases with the amount of non-MPEG-2 video.

Traffic generated by video sources is expected to be an important class of traffic in future networks, such as asynchronous transfer mode (ATM) networks. Statistical models characterizing traffic generated by variable-bit-rate (VBR) video coders are needed to address packet video per formance issues such as predicting cell loss rates in ATM networks. For video teleconference traffic, it has been shown that traffic is sufficiently accurately characterized by a multi-state Markov chain model that can be derived from three traffic parameters (mean, correlation, and variance). In this talk, we describe modeling results for sequences with frequent scene changes (the previously studied video teleconferences have very little scene variation) such as entertainment television, news, and sports. We analyze 11 long sequences. Our conclusion is that different sequences require different details regarding distributions of cells per frame and that a single model based on a few physically meaningful parameters and applicable to all sequences does not seem to be available.

Many recent studies have been conducted involving the transport of constant and variable bit rate MPEG-2 video in Asynchronous Transfer Mode (ATM) networks; however, many of these studies have considered fairly homogeneous scenarios in which the only other traffic present in the ATM network, if any, are other MPEG-2 video sources. In this study the traffic pattern of MPEG-2 video communications in an ATM network under heavily loaded network conditions, in which the generated traffic sources are bursty in nature, is considered. To complete the study an experimental VoD testbed, developed as part of a collaborative research effort between the Communications Research Centre of Canada (CRC), Nortel and the University of Ottawa, was employed. To determine the characteristics of the MPEG-2 video traffic generated by the VoD application in the ATM network in the presence of other traffic, cell interarrivai time measurements were considered. Results obtained show that the end-to-end flow control implemented in the application layer in the VoD system and the traffic controls implemented intermediate network elements (e.g., routers, switches) have significant impacts on the characteristics of the MPEG-2 traffic carried in the ATM network. Moreover, the impact of the intermediate network elements on the characteristics of the MPEG-2 traffic increases with the amount of non-MPEG-2 video traffic present in the network.

A Review on Bandwidth Utilization for Bursty Traffic in Asynchronous Transfer Mode Networks

Video traffic is expected to account for a significant share of the traffic volume in the future asynchronous transfer mode (ATM) networks. MPEG-2, proposed by the Moving Picture Expert Group, is one of the most promising compression techniques for such applications. One of the critical issues in MPEG-2 is to realize effective variable bit rate (VBR) video transfer thorough ATM networks. The Leaky Bucket (LB) scheme has been widely accepted as the usage parameter control (UPC) mechanism. The authors propose an explicit rate congestion control mechanism based on the LB scheme. Unlike the conventional LB, the leak rate is controlled using delayed feedback information sent by the network. The results show that cell loss and delay are reduced significantly at the ATM switch node.