An adaptive control for video transmission over bluetooth

This paper is concerned with transmission of a moving picture expert group (MPEG) video stream over a Bluetooth channel, using an adaptive neuro-fuzzy technique. MPEG variable bit rate (VBR) video sources over a network generally experience long delay and unacceptable data loss, due to high variations in bit rate. Furthermore, transmission rate could be unpredictable in a Bluetooth network due to interferences by other wireless devices or general Bluetooth channel noises. Subsequently, it is almost impossible to transmit VBR data sources over Bluetooth without excessive delay or data loss. In this work, an adaptive scheme is introduced so that the controller may adjust itself to the current state of the system under control. This paper utilizes a traffic-shaping buffer to prevent excessive back-to-back transmissions of MPEG VBR data sources. A novel adaptive neuro-fuzzy scheme regulates the output rate of the buffer to ensure that the video stream from the host conforms to the traffic conditions of the Bluetooth channel during the transmission period. The computer simulation results show that the use of the neuro-fuzzy controller reduces excessive delay and data loss at the host-controller-interface, as compared with a conventional VBR video transmission and a rule-based fuzzy controller (RBF1) in Bluetooth.     

Two neuro-fuzzy control schemes for a traffic-regulating buffer in wireless technology

Bluetooth wireless operates in 2.4-GHz Industrial Scientific and Medicine (ISM) frequency, which may interfere with other devices functioning within the same frequency band, such as WiFi. Furthermore, Moving Picture Expert Group (MPEG) variable bit rate (VBR) video demands larger and more stable bandwidth and may cause data loss and time delay as a result of the high variation in bit rate in Bluetooth channels with limited bandwidth. To address these issues, two new neuro-fuzzy schemes are developed to control the input and output of a buffer referred to here as the traffic-regulating buffer. Regarding the input of this buffer, a rule-based fuzzy scheme is introduced and supervised by a neural network technique as a master controller to monitor the arrival rate to the buffer. The output of the traffic-regulating buffer is observed by another rule-based fuzzy scheme and is supervised by a second neural network to monitor the departure rate. Computer simulation results demonstrate that the two proposed neuro-fuzzy models reduce standard deviation and excessive data loss, and they also show an improved picture quality as compared with conventional MPEG VBR video over a Bluetooth channel.     

Joint rate control for VBR MPEG video on PVC ATM links

A joint rate control algorithm for variable bit rate (VBR) MPEG-compressed digital video on point-to-point permanent virtual circuit (PVC) ATM links is proposed. The algorithm controls the encoding mode of a number of video encoders that operate either on VBR or constant bit rate (CBR) mode. The algorithm selects the encoding mode based on the buffer occupancy of a multiplexer co-located with the encoders that interfaces them to the PVC link. VBR encoding is the predominant encoding mode used during congestion-free periods. CBR mode is used only during congested periods. When CBR is selected, new bit rates are jointly assigned to the encoders based on their relative encoding complexities. The bit rate assigned to the encoders are enforced by a CBR rate control local to each encoder. The performance of the joint rate control algorithm is evaluated through simulation of a packet multiplexer, where a number of connections are multiplexed onto a fixed-capacity channel. The performance is compared to that of multiplexing conventional CBR and open-loop VBR from the video quality and bandwidth efficiency points of view. Simulation results show that the proposed algorithm improves performance over multiplexed conventional CBR or open-loop VBR MPEG video, without significantly increasing implementation complexity. The application of the algorithm to video-on-demand over ATM is discussed.     

AVS实时编码的VBR码率控制

针对AVS实时编码应用,提出一种基于帧层的一次编码VBR码率控制算法。利用GOP层复杂度预测来动态分配码率,在GOP内的帧采用CBR策略,结合AVS编码RDO的特点,采用准确且计算简单的率失真模型计算量化参数。实验结果表明,与AVS现用的码率控制方法JVT-H017相比,该方法码率控制准确,算法复杂度低,平均亮度PSNR提高了约0-2dB,亮度PSNR样本方差约为JVT-H017方法的40％,表明视频质量的平缓性也得到较大改善。     

Fuzzy-based rate control for real-time MPEG video

We propose a fuzzy logic-based control scheme for real-time motion picture expert group (MPEG) video to avoid long delay or excessive loss at the user-network interface (UNI) in an asynchronous transfer mode (ATM) network. The system consists of a shaper whose role is to smooth the MPEG output traffic to reduce the burstiness of the video stream. The input and output rates of the shaper buffer are controlled by two fuzzy logic-based controllers. To avoid a long delay at the shaper, the first controller aims to tune the output rate of the shaper in the video frame time scale based on the number of available transmission credits at the UNI and the occupancy of the shaper's buffer. Based on the average occupancy of the shaper's buffer and its variance, the second controller tunes the input rate to the shaper over a much larger time scale by applying a closed-loop MPEG encoding scheme. With this approach, the traffic enters the network at an almost constant bit rate (with a very small variation) allowing simple network management functions such as admission control and bandwidth allocation, while guaranteeing a relatively constant video quality since the encoding rate is changed only in critical periods when the shaper buffer “threatens” to overflow. The performance of the proposed scheme is evaluated through numerical tests on real video sequences     

Streaming video over variable bit-rate wireless channels

We consider streaming of video sequences over both constant and variable bit-rate (VBR) channels. Our goal is to enable decoding of each video unit before exceeding its displaying deadline and, hence, to guarantee successful sequence presentation even if the media rate does not match the channel rate. In this work, we show that the separation between a delay jitter buffer and a decoder buffer is in general suboptimal for VBR video transmitted over VBR channels. We specify the minimum initial delay and the minimum required buffer for a given video stream and a deterministic VBR channel. In addition, we provide some probabilistic statements in case that we observe a random behavior of the channel bit rate. A specific example tailored to wireless video streaming is discussed in greater detail and bounds are derived which allow guaranteeing a certain quality-of-service even for random VBR channels in a wireless environment. Simulation results validate the findings.     

A QoS Estimation-Based Scheduler for Real-Time Traffic in IEEE 802.11e Mobile Ad hoc Networks

ABSTRACT

For mobile ad hoc networks, the IEEE 802.11e standard specification provides Quality of Service (QoS) facility support in the MAC layer by Enhanced Distribution Channel Access (EDCA), which provides differentiated and distributed access to the wireless medium with four access categories (AC). It works efficiently for constant bit rate (CBR) types of traffic; however, for the case of variable bit rate (VBR) types of traffic, it shows poor performance due to the static nature of computing the number of packets and the time required to transmit these packets. In this paper, we present an EDCA scheduling algorithm that allocates transmission opportunities (TXOP) for fluctuating VBR traffic depending on their queue length estimations for mobile ad hoc networks. We classify the channel state as good or bad based on the channel error conditions. Then the scheduler determines the mean application data rate and estimates the TXOP for the next interval on the same Traffic Stream (TS). By simulation results, we show that the proposed scheduling scheme achieves good throughput and fairness with reduced delay for the VBR traffic class.     

Application of neural-fuzzy controller for streaming video over Bluetooth 1.2

This paper is to introduce an application of Computational Intelligence (CI) to Moving Picture Expert Group-4 (MPEG-4) video compression over IEEE.802.15.1 wireless communication, known as Bluetooth 1.2, in order to improve picture quality. The 2.4 GHz Industrial, Scientific and Medical frequency band is used for the IEEE.802.15.1 standard. IEEE.802.15.1 can be affected by noise and interference due to other neighboring wireless devices sharing the same frequency carrier. The noise and interference create difficulties in ascertaining an accurate real-time transmission rate at the receiving end. Furthermore, the MPEG-4 codec is an object-oriented compression system and demands a high bandwidth. It is therefore difficult to avoid excessive delay, image quality degradation and/or data loss during MPEG-4 video transmission over standard systems. A new buffer entitled ‘buffer added’ has been introduced at the input of the Bluetooth 1.2 device. This buffer is controlled by a Rule-Based Fuzzy (RBF) logic controller at the input and a neural-fuzzy controller (NFC) at the output. The two new fuzzy rules manipulate and supervise the flow of video over the Bluetooth 1.2 standard. The computer simulation results illustrate the comparison between a non-CI video transmission over Bluetooth 1.2 and the proposed design, confirming that the applications of RBF and NFC do improve the image quality, reduce data loss and reduce time delay.     

一种适用于DVB Over IP的传输流传送方法

对DVB Over IP应用来说，如何传送用可变比特率（VBR）压缩的MPEG-2传输流格式的视频是一个重要的问题。其中以传统的恒定速率（CBR）方式传送VBR视频时，接收端需要较大的缓存和开始延时时间；而另一种新的采用PCR协助的恒定速率（PCBR）传送方式，则是以较高的传输速率和以牺牲码率的稳定性来减少缓存需求。为了平衡传输速率和接收端缓存需求，在PCBR基础上，提出了一种称为IPCBR的改进的视频流传送方法。通过实验证明，该新方法与传统的CBR传送方式相比，不仅可降低缓存需求，而且与PCBR方式相比，又具有较高的稳定性和带宽利用率，并克服了PCBR丢包率较高的问题。同时由于该算法特别针对DVB Over IP，具有较强的实用性。且有利于Internet TV业务拓展。     

基于模糊控制的ATM网络VBR视频传输平滑策略

VBR视频传输的突发性是影响ATM网络服务质量的关键因素,文中通过模糊控制方法对视频传输流量的阈值进行监控,实现了接入的平滑并可动态调整传输速度。文中以传输流量及这发级作为评价指标进行分析,结果表明VBR视频传输自适应平滑策略的实效性。     

存储应用中AVS编码的可变码率控制

针对数字视频存储应用,分析二次编码可变码率（VBR）控制的原理和特性,提出一种固定容量视频存储应用的可变码率控制算法。对序列进行恒定码率编码,统计并记录重要的编码信息。在数据处理阶段分析每个场景的复杂度等视频特性并预分配比特数。对同一个序列进行二次VBR编码。实验结果表明,采用该算法能获得PSNR波动很小的高质量视频。     

IEEE 802.11e协议HCCA机制下的QoS研究

分析了IEEE 802.11e协议HCCA信道接入机制下的简单带宽调度算法对多媒体业务的QoS支持情况,指出其不足并在其基础上进行了改进,提出了一种基于业务等级的带宽调度算法E-HCCA（Enhanced HCCA）。E-HCCA对不同优先等级业务的数据在带宽分配上采用不同的策略,在优先保证各个节点CBR业务的基础上,根据节点的VBR流量动态平均分配剩余带宽。相比较简单调度算法,E-HCCA算法更好地支持了多用户下的语音业务流和视频业务流,降低了分组时延,增加了系统吞吐率。     

An Admission Control Scheme Based on Online Measurement for VBR Video Streams Over Wireless Home Networks

This paper presents an online measurement-based admission control scheme on the basis that the aggregate VBR video traffic is lognormally distributed. The proposed scheme consists of two components: measurement process and admission decision. The measurement process applies a linear Kalman filter to estimate statistical parameters of aggregate VBR video traffic. The estimated statistical parameters are used to calculate the effective bandwidth for admission decision. Variable bit rate (VBR) video traffic with high data rate is expected to occupy a dominant proportion of bandwidth for future wireless broadband home networks. To guarantee quality-of-service (QoS) of such VBR video streams, while achieving a high level of channel utilization, an efficient admission control scheme is urgently required, especially for emerging wireless multimedia indoor services, such as HDTV, online video game, etc. The proposed scheme is computationally efficient and accurate without much prior traffic information. Simulation results verify its effectiveness and show that it performs well for both a small number of connections and a large number of connections.     

Real-time applications in a CRMA network: a performance analysis

This paper analyses bandwidth allocation schemes for managing real-time applications (Variable Bit Rate video and voice) in a CRMA network. A methodology to compute the Quality of Service (QoS) experienced by variable bit rate (VBR) video and voice sources is proposed. As VBR video applications only tolerate extremely low packet loss rates (< 10⁻⁸), we need a computational approach to estimate very low tail probabilities. Studying the QoS with a simulation technique is not feasible, because computational costs make it almost impossible to estimate tail distribution probabilities lower than 10⁻²−10⁻³. Therefore, to achieve this target, we propose a model which represents a CRMA network's worst case behaviour (i.e. a scenario with maximum network congestion), and which can be solved analytically. By solving this model for different bandwidth allocation schemes, we can obtain the corresponding bounds on the QoS experienced by VBR video users. Finally, for those bandwidth allocation schemes which provide an acceptable QoS for VBR video traffic, we also estimate (via a trace-driven simulation) the QoS achieved by voice users.     

视频编码中考虑模式选择的位率优化控制

本文在传统位率控制方法的基础上提出一种新算法,即基于宏块的最佳位率控制算法．主要思想是在考虑还宽,比特率和缓冲区大小的同时,考虑不同宏块模式的选择对位率的影响,文中给出了一些相关结果并将其与传统方法所得数据相比较,结果表明在多数位率条件下用本算法得到的ＰＳＮＲ比传统方法要好．     

Scene-Change Aware Dynamic Bandwidth Allocation for Real-Time VBR Video Transmission Over IEEE 802.15.3 Wireless Home Networks

IEEE 802.15.3, an emerging wireless technology, was designed to provide high-quality multimedia services at home. Dynamic bandwidth allocation for a multimedia connection should be considered in order to achieve higher channel utilization, less buffer and less delay, especially for variable bit rate (VBR) multimedia connections. For real-time VBR videos, the bandwidth requirement should be predicted adaptively for effective channel-time requests. Previously, the adaptive least-mean square (LMS) algorithm with fixed step size was applied to predict channel time requirements due to its simplicity and relatively good performance. However, the performance might degrade when scene changes occurred. In this paper, we modify the variable step-size LMS algorithm and apply it as our predictor (VSSNLMS) so that the prediction errors on scene changes can be effectively reduced. Using the prediction results of VSSNLMS, we propose a dynamic bandwidth-allocation scheme that is scene-change aware and can guarantee the delay bound of real-time VBR videos. Simulation results show that the VSSNLMS predictor is superior to previous LMS-type predictors in performance, and the proposed scheme has better performance in channel utilization, buffer usage, and packet loss     

Analysis of an access node multiplexer in a system serving CBR and VBR traffic

This paper considers a multiplexer at the access node of a system serving both CBR and VBR services in a B-ISDN environment. The CBR traffic component represents fixed bit rate services in an ATM network. Such services need to be allocated a fixed number of time slots in each output frame. The VBR traffic here represents connectionless and connection oriented variable bit rate services that are loss sensitive but delay insensitive. A mathematical model is developed for such a system and performance parameters are evaluated. These results are verified by simulation.     

基于混合预测模型的VBR流拥塞控制机制

针对VBR多媒体流量的数字特征,在混合网络流量预测模型的基础上,结合小波分析和卡尔曼滤波,提出一种多媒体流自适应带宽分配算法,以合理分配网络带宽,利用双重漏桶控制网络流量。在NS网络仿真平台上进行的仿真实验表明,该算法能有效避免网络拥塞,降低网络传输时延和数据丢包率,提高带宽利用率。     

MPEG VBR视频流—统计特性及其模型

该文分析了已有的MPEG VBR视频流模型及其缺点,并在此基础上对VBR视频流的统计特性进行了研究,实验结果表明,通过对整个视频流进行场景划分（聚类）,聚类间用Markov调制链建模,而每一聚类中独立的场景则可以采用TES模型基于GOP（Group Of Picture)而非帧进行建模,则该方法既能避免状态空间过大,又能避免帧间周期性的自相关,因而能够更好地拟合VBR视频流序列的一阶和二阶统计特性,同时,对独立场景的GOP分布函数可以采用Gamma函数进行拟合,自相关函数则可以采用双指数函数更好地拟合。     

Evaluation of ABR traffic management under various system time scales

In this paper, the effects of various time scales on the management of ABR (Available Bit Rate) traffic using feedback based control is studied. Since delay tolerable, the ABR applications can be allocated the remaining resources after CBR (Constant Bit Rate) and VBR (Variable Bit Rate) applications have been accommodated. To avoid excessive losses the transmission rate of the ABR applications should be modulated by the amount of remaining resources. That is, the ABR rate should be controlled through a feedback based rate control mechanism. In this paper, a network link shared by remote ABR and VBR applications is considered and the impact of various system time scales on the effectiveness of the feedback based flow control scheme is investigated by formulating and studying a tractable analytical model. These time scales are expressed in terms of the network transmission speed, the minimum tolerable ABR rate and the rate of change of the VBR source rate. While the negative impact of a decreased network time scale on the effectiveness of this control scheme is well established, the impact of the ABR and VBR time scales has not been investigated in the past. It turns out that for a given network time scale, the induced cell losses can be significantly reduced for increased ABR and/or VBR time scales and thus, the latter time scales should be taken into consideration while evaluating the effectiveness of an adaptive feedback based flow control mechanism. This study also suggests that higher efficiency can be achieved by enforcing large ABR time scales, leading to the introduction of a new class of transmission policies.