基于QoE感知的中继卫星带宽资源分配方法研究

为改善数据中继卫星的带宽分配对负载传输效率的影响，提出了一种基于用户体验质量QoE感知的中继卫星带宽资源分配方法。考虑到空间信息网络高动态链路情况下传输的可靠性，建立基于多个静止同步轨道卫星协同接入模型，研究了低轨道用户卫星进行多路数据上传的优势特点。通过设置链路效能函数，其将用户QoE满意度量化为链路反馈和链路成本，并用库恩塔克方法求解，实现最大化系统效能和带宽公平分配。研究结果表明，与Load-Balancing和Best-SNR-First方法相比，该方法不仅保证了用户QoE满意度，还提升了网络的接入性能。     

Improving TCP fairness and performance with bulk transmission control over lossy wireless channel

The traditional windows-based TCP congestion control mechanism produces throughput bias against flows with longer packet roundtrip times; the flow with a short packet roundtrip time preoccupies the shared network bandwidth to a greater extent than others. Moreover, the blind window reduction that occurs whenever packets are lost decreases the network utilization severely, especially in networks with high packet losses. This paper proposes a sender-based TCP congestion control, called TCP-BT. The scheme estimates the network bandwidth depending on the transmission behavior of applications, and adjusts the congestion window by considering both the estimated network bandwidth and the packet roundtrip time to improve fairness as well as transmission performance. The scheme has been implemented in the Linux platform and compared with various TCP variants in real environments. The experimental results show that the proposed scheme improves transmission performance, especially in networks with congestion and/or high packet loss rates. Experiments in real commercial wireless networks have also been conducted to support the practical use of the proposed mechanism.     

基于联邦共识机制的多视频流带宽分配策略

针对瓶颈链路中视频带宽分配不均导致的用户QoE不公平以及带宽利用率低的问题,提出了一种基于联邦深度强化学习的分布式视频流公平调度策略。该策略能够根据客户端网络状态和视频QoE等级动态生成带宽分配权重因子,服务器端的拥塞控制算法则根据带宽分配权重因子为瓶颈链路中的每个视频流分配带宽,以保障瓶颈链路中视频流的公平传输。每个视频终端都运行一个带宽分配agent,且多个agent以联邦学习的方式周期性地训练,以便代理模型能够快速收敛。带宽分配agent通过共识机制同步联邦训练参数,实现了在异步播放请求条件下带宽分配agent模型参数的分布式聚合,并确保了agent模型参数的安全共享。实验结果表明,与最新方案相比,提出策略在QoE公平性和整体QoE效率方面分别提高了10%和7%,这表明提出策略在解决视频流带宽分配不均问题和提升用户体验方面具有潜力和有效性。     

Combining traffic-shaping methods with congestion control variants for HTTP adaptive streaming

HTTP Adaptive Streaming (HAS) is a streaming video technique widely used over the Internet. However, it has many drawbacks that degrade its user Quality of Experience (QoE). Our investigation involves several HAS clients competing for bandwidth inside the same home network. Studies have shown that managing the bandwidth between HAS clients using traffic-shaping methods improves the QoE. Additionally, the TCP congestion control algorithm in the HAS server may also impact the QoE, because every congestion control variant has its own method to control the congestion window size. Based on previous work, we describe two traffic-shaping methods, the Hierarchical Token Bucket shaping Method (HTBM) and the Receive Window Tuning Method (RWTM), as well as four popular congestion control variants: NewReno, Vegas, Illinois, and Cubic. In this paper, our objective is to provide a detailed comparative evaluation of combining these four congestion control variants with these two shaping methods. The main result indicates that Illinois with RWTM offers the best QoE without causing congestion. Results were validated through experimentation and objective QoE analytical criteria.     

Methodologies for bandwidth allocation,transmission scheduling,and congestion avoidance in broadband ATM networks

The call types supported in high-speed packet networks vary widely in their bandwidth requirements and tolerance to message delay and loss. In this paper, we classify various traffic sources which are likely to be integrated in broadband ATM networks, and suggest schemes for bandwidth allocation and transmission scheduling to meet the quality and performance objectives. We propose ATM cell-multiplexing using a Dynamic Time-Slice (DTS) scheme which guarantees a required bandwidth for each traffic class and/or virtual circuit (VC), and is dynamic in that it allows the different traffic classes or VCs to share the bandwidth with a soft boundary. Any bandwidth momentarily unused by a class or a VC is made available to the other traffic present in the multiplexer. The scheme guarantees a desired bandwidth to connections which require a fixed wide bandwidth. Thus, it facilitates setting up circuit-like connections in a network using the ATM protocol for transport. The DTS scheme is an efficient way of combining constant bit-rate (CBR) services with variable bit-rate (VBR) stastically multiplexed services. We also described methodologies to schedule delivery of delay-tolerant data traffic within the framework of the DTS scheme. Important issues such as buffer allocations, guarantee of service quality, and ease of implementation are also discussed.     

A network algorithm for 3D/2D IPTV distribution using WiMAX and WLAN technologies

The appearance of new broadband wireless technologies jointly with the ability to offer enough quality of service to provide IPTV over them, have made possible the mobility and ubiquity of any type of device to access the IPTV network. The minimum bandwidth required in the access network to provide appropriate quality 3D/2D IPTV services jointly with the need to guarantee the Quality of Experience (QoE) to the end user, makes the need of algorithms that should be able to combine different wireless standards and technologies. In this paper, we propose a network algorithm that manages the IPTV access network and decides which type of wireless technology the customers should connect with when using multiband devices, depending on the requirements of the IPTV client device, the available networks, and some network parameters (such as the number of loss packets and packet delay), to provide the maximum QoE to the customer. The measurements taken in a real environment from several wireless networks allow us to know the performance of the proposed system when it selects each one of them. The measurements taken from a test bench demonstrate the success of our system.     

QoE management for video conferencing applications

We introduce a framework for managing the QoE of videos coded with the H.264 codec and transmitted by video conferencing applications through limited bandwidth networks. We focus our study on the medium-motion videos with QCIF, CIF, and VGA resolutions, the most pervasive video formats used by video conferencing applications across the Internet and cellular telephony systems. Using subjective tests for measuring the level of video quality perceived by end users, we expose the relation between the main influential video parameters and the quality experienced by end users. Furthermore, after investigating the effect of different frame rates and compression levels on video streaming bit rate, and consequently on QoE, we propose a QoE control mechanism for limited-bandwidth situations. A congestion control technique is also introduced in this paper and used in simulations for verifying the efficiency of the proposed QoE management algorithm and to implement this algorithm for practical applications.     

Analysis and reduction of data spikes in thin client computing

While various optimization techniques have been used in existing thin client systems to reduce network traffic, the screen updates triggered by many user operations will still result in long interactive latencies in many contemporary network environments. Long interactive latencies have an unfavorable effect on users’ perception of graphical interfaces and visual contents. The long latencies arise when data spikes need to be transferred over a network while the available bandwidth is limited. These data spikes are composed of a large amount of screen update data produced in a very short time. In this paper, we propose a model to analyze the packet-level redundancy in screen update streams caused by repainting of graphical objects. Using this model we analyzed the data spikes in screen update streams. Based on the analysis result we designed a hybrid cache-compression scheme. This scheme caches the screen updates in data spikes on both server and client sides, and uses the cached data as history to better compress the recurrent screen updates in possible data spikes. We empirically studied the effectiveness of our cache scheme on some screen updates generated by one of the most bandwidth-efficient thin client system, Microsoft Terminal Service. The experiment results showed that this cache scheme with a cache of 2M bytes can reduce 26.7%–42.2% data spike count and 9.9%–21.2% network traffic for the tested data, and can reduce 25.8%–38.5% noticeable long latencies for different types of applications. This scheme costs only a little additional computation time and the cache size can be negotiated between the client and server.     

运动感知基于缓存的自适应视频流传输

目的 基于缓存的自适应视频流传输策略无需估测实时带宽,直接通过缓存变化量与码率的映射函数选取符合当前网络状况的最佳质量码流传输。传统基于缓存的自适应视频传输不考虑内容特征,在码率选择上为不同运动级别视频内容均使用相同的码率映射函数,在不稳定的无线网络环境中高运动强度内容的码率急剧降低会严重伤害用户体验质量（QoE）,提出运动感知基于缓存的自适应视频流传输（MA-BBA）算法。方法 MA-BBA算法根据片段运动级别确定码率映射函数,对运动强度高的内容快速切换到较高码率,而对于运动强度较低的内容则使用较为保守的码率,从而使得缓存资源能够位于安全边界之上且较多分配给高级别运动内容,提高不同运动强度内容的平均质量,使整体QoE得到优化。结果 在公开的无线网络带宽数据集上实现本文MA-BBA算法,基于吞吐量的自适应传输算法（TBA）和基于缓存的自适应传输算法（BBA）。MA-BBA在高运动强度内容的平均质量上比TBA和BBA分别提高1.7%和1.2%,且质量波动区间更小。MA-BBA在平均缓存利用率上达到72%,大大高于TBA的45.9%和BBA的45.4%。结论 MA-BBA算法与现有的码率自适应算法TBA和BBA相比,大大提高了缓存资源利用率,提高了对资源要求最苛刻的高级别运动内容的传输质量,减小码率切换幅度频率,优化了视频服务的整体QoE。     

Compression-unimpaired batch-image encryption combining vector quantization and index compression

As the network bandwidth has grown rapidly, it has become common to share a large number of still images via the Internet by means of batch transmission. Unfortunately, most existing methods encrypt only a single image, so there is room for improvement in our ability to send batches of images at one time. A complete reconstruction of the methods is sometimes necessary, especially when considering performance criteria. This paper presents a novel batch-image encryption algorithm that combines Vector Quantization (VQ) and additional index-compression process to benefit from their computational efficiency and low transmission bandwidth without affecting the original compression rate. The experimental results show the performance of this new scheme in terms of compression rate and computational cost.     

基于用户偏好的网络质量QoE感知建模仿真分析

为了解决现有网络质量QoE感知模型数据粗差迭代次数多、线性回归参数小的问题,提出基于用户偏好的网络质量QoE感知建模仿真研究。依据用户偏好理论确定模型参数,并获取网络质量QoE感知数据,以此为基础,通过MCD算法判别并去除网络质量QoE数据粗差,以去除粗差的网络质量QoE数据为基础,利用ROI加权算法提取网络质量QoE数据特征,以得到的网络质量QoE数据特征为依据,将其代入多元线性回归方程计算网络质量QoE感知,实现了基于用户偏好的网络质量QoE感知。实验结果显示,与现有三种网络质量QoE感知模型相比较,构建的网络质量QoE感知模型降低了数据粗差迭代次数,提高了线性回归参数,充分说明构建的网络质量QoE感知模型具备更好的性能。     

Modeling the influence of network delay on the user experience in distributed home-automation networks

Today’s modern home-automation systems and services (HASS) frequently communicate over public telecommunications networks, such as the Internet. Unfortunately, these communication networks do not usually provide sufficient quality (i.e., a predictable delay), which is generally assured in fieldbus HASS networks. Consequently, the user-perceived quality of experience (QoE) cannot be maintained at a satisfactory level when using different HASS devices communicating over an IP-based network. The data transferred over the Internet can experience a non-negligible delay that can have a considerable influence on the QoE. For this reason, the main goal of our research was to measure the influence of the network delay on a subjective QoE assessment, while interacting with some frequently used HASS tasks. The results show that users are satisfied if the delay is kept below 0.8?s, and that they can tolerate delays of over 2?s (depending on the level of the HASS task interactivity). Since such a user-perceived subjective QoE assessment is both time-consuming and expensive we also propose objective QoE assessment models to represent the influence of network delay on a subjective QoE assessment for various HASS tasks.     

A path switching scheme for SCTP based on round trip delays

Due to the rapid development of network applications, today the Internet plays an important role in our everyday life. Users hope that the network is always speedy enough to help them access the Internet without any delay. But the real situation is far from the ideal case. In the future, network researchers will continuously improve the network speed, and try to develop networks that are robust, without any crashes or packet loss. In this paper, we propose an aggressive path switching scheme for SCTP. Before data transmission, the scheme selects the fastest path as the primary path to transmit packets. When the path fails or transmission quality is poor, this scheme evaluates alternate paths, and selects the one with the best quality as the new primary path to substitute for the original one. After that, packets are delivered through the new path. Several factors are considered in the evaluation, including bandwidth, encryption/decryption, size of the congestion window, retransmission policy, routing policy, etc.     

QoE优先的移动网络RRTCC传输改进策略

目前Chrome浏览器为WebRTC适配的RRTCC（receiver-side real-time congestion control)拥塞控制算法在移动网络环境的多流竞争情况下表现较差.在有TCP流共存的情况下会过度退让从而导致WebRTC流饥饿,在视频会议这种多WebRTC流并发的情况下,新加入的WetRTC流会损害已有流的通信质量.针对该问题,提出了QoE优先考量的RRTCC传输控制改进策略MTCIS,该策略根据对当前移动网络性能和QoE需求的分析,采取激进程度适中的WebRTC传输控制方法,避免了与TCP流竞争时过度退让的问题.针对多WebRTC流并发的场景,设计了并发流管理机制,在合理利用带宽和优先满足用户QoE的基础上,对视频流的传输参数进行动态调整.实验结果表明,在移动网络场景多流竞争的情况下,MTCIS策略能够有效地保证WebRTC的合理竞争性、稳定性和健壮性,提高了用户的QoE体验.     

Dynamic multiple-frame bandwidth provisioning with fairness and revenue considerations for Broadband Wireless Access Systems

The increasing demand for wireless heterogeneous multimedia services presents a real challenge to mobile network operators. Even with the substantial increase in the supported bandwidth in emerging Broadband Wireless Access Systems (BWASs) such as 3.5G High Speed Downlink Packet Access (HSDPA) and the Worldwide Interoperability for Microwave Access (WiMAX), satisfying the bandwidth requirements of mobile users while increasing the revenues of network operators is still one of the major issues in these systems. Therefore, bandwidth provisioning will certainly play a decisive role in the success of such BWASs. In this paper, we propose a novel dynamic multiple-frame bandwidth provisioning scheme for BWASs. The proposed scheme spans multiple time frames and optimally allocates them to the different classes of traffic depending on their weights, the real-time bandwidth requirements of their users’ connections, their channel quality conditions and the expected obtained revenues. To maximize fairness and still maintain service differentiation between classes, we provide a unique formulation for dynamically computing the class weights. Simulation results are provided to show the potential and effectiveness of our scheme.     

基于视点预测的全景视频码率自适应策略

为解决全景视频传输中存在的视频卡顿多、用户体验质量（quality of experience,QoE）低等问题,研究当前主流的视点自适应传输方案,提出一种基于视点预测的码率自适应策略（VPBAS）。首先,构建了一种基于长短期记忆网络和全卷积网络的视点预测模型,模型将视点数据和视频显著性信息进行特征融合,实现不同模态数据的相互补充和修正,提高视点预测的准确率;然后,客户端采用随机森林算法预测当前的可用带宽,并根据视点预测结果和可用带宽信息为视频分块选择码率。最后,客户端把选择的码率信息定期发送给服务器,服务器根据反馈的信息向客户端推送最佳码率的全景视频流,这种交互过程在视频播放期间不断地重复,直至客户端观看完毕。实验结果表明,与现有传输方案相比,VPBAS能有效提高带宽受限情况下的视频观看体验。     

基于双向强化学习与动态码率调节的无线mesh网络协议

针对现有无线mesh网络协议的用户体验质量(QoE)较差的问题,提出一种基于双向强化学习与动态码率调节的无线mesh网络协议。首先,设计了兼容不同服务类型的无线mesh网络QoE度量框架;然后,设计了基于双向强化学习的无线mesh网络路由协议;最终,结合QoE感知的差异化报文调度策略与数据流源节点码率动态调节算法进一步优化终端用户的QoE质量。基于NS-2仿真平台的对比实验结果显示,本协议可明显地提高无线mesh网络的QoE指标,同时具有较低的控制开销。     

Incorporating packet semantics in scheduling of real-time multimedia streaming

In this work, we develop a novel packet scheduling algorithm that properly incorporates the semantics of a packet. We find that improvement in overall packet loss does not necessarily coincide with improvement in user perceivable QoS. The objective of this work is to develop a packet scheduling mechanism which can improve the user perceivable QoS. We do not focus on improving packet loss, delay, or burstiness. We develop a metric called, “Packet Significance,” that effectively quantifies the importance of a packet that properly incorporates the semantics of a packet from the perspective of compression. Packet significance elaborately incorporates inter-frame, intra-frame information dependency, and the transitive information dependency characteristics of modern compression schemes. We apply packet significance in scheduling the packet. In our context, packet scheduling consists of two technical ingredients: packet selection and interval selection. Under limited network bandwidth availability, it is desirable to transmit the subset of the packets rather than transmitting the entire set of packets. We use a greedy approach in selecting packets for transmission and use packet significance as the selection criteria. In determining the transmission interval of a packet, we incorporate the packet significance. Simulation based experiments with eight video clips were performed. We embed the decoding engine in our simulation software and examine the user perceivable QoS (PSNR). We compare the performance of the proposed algorithm with best effort scheduling scheme and one with simple QoS metric based scheduling scheme. Our Significance-Aware Scheduling scheme (SAPS) effectively incorporates the semantics of a packet and delivers best user perceivable QoS. SAPS can result in more packet loss or burstier traffic. Despite these limitations, SAPS successfully improves the overall user perceivable QoS.     

QoE-Aware wireless video communications for emotion-aware intelligent systems: A multi-layered collaboration approach

With the ever increasing demand on high-quality visual information for emotion-aware intelligent systems, wireless video traffic explosively grows and causes great energy consumption. Therefore, providing high quality of experience (QoE) for connected users becomes increasingly important. Aiming to establish a new paradigm to solve this challenging problem, in this article we propose a multi-layered collaboration approach to provide energy-efficient QoE-aware wireless video communications by efficiently utilizing the limited transmission resources of wireless networks for 5G. We first investigate the emotion-aware intelligent system QoE measurement based on objective metrics of quality of service (QoS). Then, we utilize the multi-layered collaborations of physical, network and application layers among the connected users to achieve energy-efficient QoE-aware video communications. By developing a profound understanding of the interplay between the video applications and wireless networks, we qualitatively analyze how QoE can benefit from the multi-layered collaborations, and quantitatively assess the achievable gains in a typical wireless-connected emotion-aware application scenario.     

Dynamic Resource Allocation for Multimedia Document Retrieval over High Speed LANs

The emergence of gigabit local area networks (G-LANs) has spurred a tremendous interest in supporting networked multimedia applications over a LAN. In this paper, we propose a mechanism for dynamically allocating network resources in asynchronous LANs. Presentation of multimedia objects with required play-out quality requires Quality of Service (QoS) guarantees by the underlying networking infrastructure. Existing asynchronous LANs, such as Ethernet, do not support the notion of QoS due to their asynchronous media access protocol. For such networks, we propose a dynamic bandwidth management scheme that uses the concept of Time Division Multiple Access (TDMA). Significant performance improvement is observed through experimental results. In particular, the transmission rates for multimedia hosts improve significantly with low jitter variations in media streams. We also propose a framework for graceful degradation of play-out quality of multimedia objects in case the LAN's total capacity is not sufficient to meet the overall demand.