Variable Bit Rate Transmission Research Articles

Resilient quantized control under Denial-of-Service: Variable bit rate quantization

In this paper, we investigate a networked control problem in the presence of Denial-of-Service (DoS) attacks, which prevent transmissions over the communication network. The communication between the process and controller is also subject to bit rate constraints. For mitigating the influences of DoS attacks and bit rate constraints, we develop a variable bit rate (VBR) encoding–decoding protocol and quantized controller to stabilize the control system. We show that the system’s resilience against DoS under VBR is preserved comparing with those under constant bit rate (CBR) quantized control, with fewer bits transmitted. The proposed VBR quantized control framework in this paper is general enough so that the results of CBR quantized control under DoS and moreover the results of minimum bit rate in the absence of DoS can be recovered. In the last part of the paper, we propose two random VBR transmission protocols, in which not only the bit rate but also the interval between two transmission attempts are time-varying. These protocols enable us to prevent attackers from learning how transmissions are scheduled and to mitigate the influence of attacks specifically targeting at periodic transmission instants. A numerical example is given to illustrate the proposed solution approach.

HFC 망에서 대용량 방송서비스를 위한 채널 결합 기반 전송 방식 및 시뮬레이터 개발

최근에는 UHD(Ultra High Definition) 방송과 같은 단일 채널 전송용량을 초과하는 새로운 대용량 방송 서비스들이 소개되고 있다. 이러한 대용량 방송 콘텐츠를 전송하기 위해 주로 통신 채널을 통한 데이터 전송에 사용되던 채널 결합 기술들을 적용한 솔루션들이 검토되고 있다. HFC(Hybrid Fiber Coaxial) 망에서는 양방향 데이터 전송서비스를 제공하기 위해서 적용하고 있는 DOCSIS 3.0(Data Over Cable Service Interface Specification 3.0) 규격이 상/하향 채널 결합 기술을 지원하고 있다. 주로 하향 채널을 이용한 단방향 전송 특성을 갖는 방송서비스에 이러한 채널 결합 기술을 적용하기 위해서는 DOCSIS 3.0 규격과는 다른 전송 방식에 관한 연구가 필요하다. 또한, 방송을 위해 다수의 전송 채널을 점유하는 대용량 방송 콘텐츠의 특성 상 기존과 같은 CBR(Constant Bit Rate) 전송보다는 전송 대역 효율 측면에서 유리한 VBR(Variable Bit Rate) 전송에 관한 연구필요성도 제기되고 있다. 이와 더불어 전송 지연 및 지터에 민감한 방송서비스의 특성 상 채널 결합을 위한 채널 할당 및 전송 스케줄링에 관한 연구도 필요하다. 본 논문에서는 HFC 망에서 UHD(Ultra High Definition) 방송콘텐츠와 같은 대용량 방송콘텐츠를 전송하기 위해서 채널 결합 기반의 VBR 방송콘텐츠 전송 방식을 제안하고, OPNET 기반의 전송 시뮬레이터를 개발하여 제안한 전송 방식의 성능을 평가한다. 이를 위해, HFC 망에서 대용량 방송콘텐츠를 전송하기 위한 다양한 시나리오를 정의하고, 전송 시뮬레이터를 이용하여 각 시나리오별 전송 성능을 평가한다. 개발된 시뮬레이터를 통해서 HFC 망에서 효율적으로 대용량 방송서비스를 제공하기 위해 VBR 콘텐츠 전송 및 채널 결합 기술의 필요성을 검토하고 전송 시나리오 별 전송 성능을 평가한다. 이를 통해 개발된 시뮬레이터는 향후 효율적인 대용량 방송콘텐츠 전송 기술 및 시스템 개발에 활용될 수 있을 것으로 기대된다. Massive broadcasting contents such as UHD(Ultra High Definition) TV which requires multi-channel capacity for transmission has been introduced in recent years. A transmission scheme with channel bonding has been considered for transmission of massive broadcasting contents. In HFC(Hybrid Fiber Coaxial) networks, DOCSIS 3.0(Data Over Cable Service Interface Specification 3.0) has already applied channel bonding schemes for up/downstream of data service. A method unlike DOCSIS 3.0 is required to introduce a channel bonding scheme in the broadcasting service having unidirectional transmission with a downstream. Since a massive broadcasting content requires several channels for transmission, VBR(Variable Bit Rate) transmission has been emerging for the bandwidth efficiency. In addition, research on channel allocation and resource scheduling is required to guarantee QoS(Quality of Service) for the broadcasting service based on VBR. In this paper, we propose a transmission method for mass broadcasting service in HFC network and show the UHD transmission simulator developed to evaluate the performance. In order to evaluate the performance, we define various scenarios. Using the simulator, we assess the possibility of channel bonding and VBR transmission for UHD broadcasting system to provide mass broadcasting service efficiently. The developed simulator is expected to contribute to the efficient transmission system development of mass broadcasting service.

Segment-based traffic smoothing algorithm for VBR video stream

Transmission of variable bit rate (VBR) video, because of the burstiness of VBR video traffic, has high fluctuation in bandwidth requirement. Traffic smoothing algorithm is very efficient in reducing burstiness of the VBR video stream by trans- mitting data in a series of fixed rates. We propose in this paper a novel segment-based bandwidth allocation algorithm which dynamically adjusts the segmentation boundary and changes the transmission rate at the latest possible point so that the video segment will be extended as long as possible and the number of rate changes can be as small as possible while keeping the peak rate low. Simulation results showed that our approach has small bandwidth requirement, high bandwidth utilization and low computation cost.

Improved priority access, bandwidth allocation and traffic scheduling for docsis cable networks

The Data Over Cable Service Interface Specifications (DOCSIS) is intended to support IP flows over HFC (hybrid fiber/coax) networks with significantly higher data rates than analog modems and Integrated Service Digital Network (ISDN) links for high quality audio, video and interactive services. To support quality-of-service (QoS) for such applications, it is important for HFC networks to provide effective media access and traffic scheduling mechanisms. In this paper, we first present a multilevel priority collision resolution scheme with adaptive contention window adjustment. The proposed collision resolution scheme separates and resolves collisions for different traffic priority classes (such as delay-sensitive and best effort streams), thus achieving the capability for preemptive priorities. Second, a novel MAC (media access control) scheduling mechanism and a new bandwidth allocation scheme are proposed to support multimedia traffic over DOCSIS-compliant cable networks. It is shown through simulation results that throughput and delay performance have been improved for the transmission of real-time VBR (variable bit rate) traffic as compared to current DOCSIS specifications.

Queueing networks approach for bandwidth estimation of smoothed VBR video streams

The growing importance of multimedia applications, which usually implies the transmission of variable bit rate (VBR) video streams, needs an accurate analysis of bandwidth requirements according to specified quality of service (QoS) guarantees. In this paper an original algorithm is proposed for statistical aggregate bandwidth estimation of smoothed VBR video streams, respecting a specified loss probability (the QoS parameter taken into account). This algorithm is based on concepts of multiclass networks of queues whose service centers are represented by the bandwidth levels assumed by smoothed films. The mean service times and the transition probabilities between service centers are directly derived from real video traces. The analytical results have been compared with simulation results and with the results obtained by another analytical method already present in the literature, i.e., the Chernoff bound, discussing the effectiveness of the proposed method.

Rate–distortion model based rate control for real-time VBR video coding and low-delay communications

Abstract Rate control is an important component in a video encoder for data storage or real-time visual communications. In the paper, we will discuss the rate control in MPEG encoder for low-delay real-time video communications over variable bit-rate (VBR) channel. In low-delay video communications, the video transmission is subject not only to the channel rate constraints, but also to the end-to-end delay constraints. In the paper, we employ leaky-bucket model to describe the traffic parameters and monitor the encoder's output. First, an ad hoc bit-allocation method is introduced. Although satisfying the rate constraints perfectly, it provides the objective quality of the decoded image to be just comparable to that of CBR rate control using MPEG2 TM5. Then, a new rate–distortion model is developed, based on which an advanced rate control algorithm is designed, producing almost uniform distortion within a frame as well as consistent video quality between frames. Experimental results show that, when compared to both the MPEG2 TM5 and the proposed ad hoc bit-allocation method, the advanced rate control algorithm maintains not only a constant buffer delay, but also a stable decoded image quality in the scenario of VBR transmission.

Optimal smoothing for guaranteed service

We consider the transmission of variable bit rate (VBR) video over a network offering a guaranteed service such as ATM VBR or the guaranteed service of the IETF. The guaranteed service requires that the flow accepted by the network has to be conforming with a traffic envelope /spl sigma/; in return, it receives a service guarantee expressed by a network service curve /spl beta/. Functions /spl alpha/ and /spl beta/ are derived from the parameters used for setting up the reservation, for example, from the T-SPEC and R-SPEC fields used with the resource reservation protocol (RSVP). In order to satisfy the traffic envelope constraint, the output of the encoder is fed to a smoother, possibly with some look-ahead. The resulting stream is transported by the network; at the destination, the decoder waits for an initial playback delay and reads the stream from the receive buffer. We consider the problem of whether there exists one optimal strategy at the smoother which minimizes the playback delay and the receive buffer size, given the traffic envelope /spl alpha/ and the service curve /spl beta/. We show that there does exist such an optimal smoothing, and give an explicit representation for it. We also obtain a simple expression for the smallest playback delay and playback buffer size which can be achieved over all possible smoothing and playback strategies. We show that the computation of optimal smoothing and minimum playback delay do not depend on the past. We show that separate delay equalization is optimal in the constant bit rate (CBR) case, but not otherwise. We also apply the theory to the analysis of which T-SPEC should be requested by a source-destination pair, given some playback delay and buffer constraint, and given the path characteristics advertised in RSVP PATH messages.

Transporting compressed video over ATM networks with explicit-rate feedback control

We propose a scheme for transmission of variable bit rate (VBR) compressed video for interactive applications using the explicit-rate congestion-control mechanisms proposed for the available bit rate (ABR) service in asynchronous transfer mode networks. Compressed video is inherently bursty, with rate fluctuations over both short and long time scales. This source behavior can be accommodated by the ABR service, since the explicit-rate scheme allows sources to request varying amounts of bandwidth over time. Moreover, when the bandwidth demand cannot be met, the network provides feedback indicating the bandwidth currently available to a connection. In our scheme, the video source rate is matched to the available bandwidth by modifying the quantization level used during compression. We use trace-driven simulations to examine how effective the enhanced explicit-rate scheme is in "rate matching" between the network and the source and the effect on end-to-end delay. We also look at the sensitivity of the proposed scheme to the estimates of the network round-trip times and to inaccuracies in the rate requests made by sources.

VBR video: tradeoffs and potentials

The authors examine the transport and storage of video compressed with a variable bit rate (VBR). They focus primarily on networked video, although they also briefly consider other applications of VBR video, including satellite transmission (channel sharing), playback of stored video, and wireless transport. Packet video research requires careful integration between the network and the video systems; however, a major stumbling block has resulted because commonly used terms are often interpreted differently by the video and networking communities. The paper then, has two main goals: (i) to clarify the definitions of terms that are often used with different meaning by networking and video-coding researchers and (ii) to explore the tradeoffs entailed by each of the various modalities of VBR transmission (unconstrained, shaped, constrained, and feedback). In particular, they evaluate the tradeoff among the advantages (better video quality, less delay, and more calls) that were identified by early proponents of VBR video transmission. An underlying theme of this paper is that increased interaction between the video and network design has potential for improving overall decoded video quality without changing the network capacity.

Optimal bit allocation for coding of video signals over ATM networks

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.

Joint selection of source and channel rate for VBR video transmission under ATM policing constraints

Variable bit-rate (VBR) transmission of video over ATM networks has long been said to provide substantial benefits, both in terms of network utilization and video quality, when compared with conventional constant bit-rate (CBR) approaches. However, realistic VBR transmission environments will certainly impose constraints on the rate that each source can submit to the network. We formalize the problem of optimizing the quality of the transmitted video by jointly selecting the source rate (number of bits used for a given frame) and the channel rate (number of bits transmitted during a given frame interval). This selection is subject to two sets of constraints, namely, (1) the end-to-end delay has to be constant to allow for real-time video display and (2) the transmission rate has to be consistent with the traffic parameters negotiated by user and network. For a general class of constraints, including such popular ones as the leaky bucket, we introduce an algorithm to find the optimal solution to this problem. This algorithm allows us to compare VBR and CBR under the same end-to-end delay constraints. Our results indicate that variable-rate transmission can increase the quality of the decoded sequences without increases in the end-to-end delay. Finally, we show that for the leaky-bucket channel, the channel constraints can be combined with the buffer constraints, such that the system is identical to CBR transmission with an additional, infrequently imposed constraint. Therefore, video quality with a leaky-bucket channel can achieve the same quality of a CBR channel with larger physical buffers, without adding to the physical delay in the system.

Traffic prediction and dynamic bandwidth allocation over ATM: a neural network approach

ATM (Asynchronous Transfer Mode) has been recommended as the transport vehicle for Broadband Integrated Service Digital Networks (BISDN). The ATM technology offers a great flexibility of transmission bandwidth allocation to accommodate diverse demands of multimedia connections, which include data, voice, video, graphics and images. One major application in ATM networks is to provide real-time, low-loss and minimum-delay transmission of variable bit rate (VBR) traffic which is highly bursty, non-stationary and correlated. In this work we adopt neural network methodology to predict VBR traffic represented by a continuous autoregressive (AR) Markov model. We have found that a simple 1-5-1 backpropagation neural network can accurately predict the VBR traffic. Based on prediction results obtained from neural networks, we propose a dynamic bandwidth allocation scheme for ATM. The proposed scheme is simulated under various traffic loads and buffer sizes. Its performance in terms of cell loss, cell delay and link utilization is examined and compared with two other bandwidth allocation schemes: the static average bandwidth allocation scheme, and the optimal (ideal) bandwidth allocation scheme. Experiments show that for most of the time, performance of the proposed dynamic bandwidth allocation is much better than that of the static average bandwidth allocation, and in many cases it is very close to that of the ideal bandwidth allocation.

Variable bit‐rate video transmission under usage parameter control

AbstractThis paper proposes a method of video bit‐rate control for the case where the average transmission bitrate is constrained, considering the usage parameter control in an ATM network. By a simulation, the video quality and the network congestion probability of the variable bit‐rate (VBR) transmission system, with the constrained average bit‐rate, are compared to those of the conventional constant bit‐rate (CBR) transmission system or the VBR transmission system without the rate control. the relations among the length of the sliding window (SW) to monitor the average bit‐rate, the video quality, and the network congestion probability are analyzed.With respect to the video quality, it is shown that the VBR transmission with the average bit‐rate control exhibits a stable image quality when SW is long and exhibits a better image quality than the CBR transmission for the cases of scene change and the panning scene. When the scene changes, the image quality changes and the VBR transmission with the bit‐rate control.With respect to the network congestion probability, it is shown that the probability is decreased greatly by constraining the average bit‐rate and the probability becomes less when SW is made shorter.Finally, it is shown that SW should desirably be long to stabilize the video quality but the permissible length of SW depends on how many video signlas can be multiplexed in the network.

Two-layer video coding for ATM networks

This paper highlights the cell loss problem associated with coding video for variable bit-rate transmission over asynchronous transmission mode networks. Countermeasures are discussed from which a 2-layer coding algorithm has been chosen for a more detailed study. Simulation results are presented for a 2-layer codec using a constant bit-rate base layer and a variable rate enhancement layer compared to a 1-layer model. These results are then used further to investigate achievable network loadings.