Double feedback streaming agent for real-time delivery of media over 3G wireless networks

A network agent located at the junction of wired and wireless networks can provide additional feedback information to streaming media servers to supplement feedbacks from clients. Specifically, it has been shown that feedbacks from the network agent have lower latency, and they can be used in conjunction with client feedbacks to effect proper congestion control. In this work, we propose the double-feedback streaming agent (DFSA) which further allows the detection of discrepancies in the transmission constraints of the wired and wireless networks. By working together with the streaming server and client, DFSA reduces overall packet losses by exploiting the excess capacity Of the path with more capacity. We show how DFSA can be used to support three modes of operation tailored for different delay requirements of streaming applications. Simulation results under high wireless latency show significant improvement of media quality using DFSA over non-agent-based and earlier agent-based streaming systems.     

Practical design of a proxy agent to facilitate adaptive video streaming service across wired/wireless networks

Thanks to the growing of the wireless networks, the video streaming application becomes a ubiquitous joyful service. In a wireless communication network environment, the service traffic spans across the wired and wireless domains. In this article, we propose a practical design of a proxy agent - SPONGE (Stream Pooler Over a Network Graded Environment) sitting between the wireless User Equipments (UEs) and the video streaming server to facilitate the adaptive video streaming service across wired/wireless networks. To make the wireless streaming service more efficient, an input video session would be encoded as multiple qualities of video streams so that UEs with a similar receiving condition can share streams with the same service quality via SPONGE. SPONGE can alleviate the direct load on the original stream broadcasting server. Meanwhile, it can make each UE get an adaptive streaming service according to the network conditions of the UE by a reduced network condition feedback latency. Our theoretical analysis and simulation results show that SPONGE can help wireless streaming users get a smooth and better playback quality by a quick and accurate reaction to the network condition.     

Multiple TFRC Connections Based Rate Control for Wireless Networks

Rate control is an important issue in video streaming applications for both wired and wireless networks. A widely accepted rate control method in wired networks is equation based rate control , in which the TCP friendly rate is determined as a function of packet loss rate, round trip time and packet size. This approach, also known as TCP friendly rate control (TFRC), assumes that packet loss in wired networks is primarily due to congestion, and as such is not applicable to wireless networks in which the bulk of packet loss is due to error at the physical layer. In this paper, we propose multiple TFRC connections as an end-to-end rate control solution for wireless video streaming. We show that this approach not only avoids modifications to the network infrastructure or network protocol, but also results in full utilization of the wireless channel. NS-2 simulations, actual experiments over 1$times$RTT CDMA wireless data network, and and video streaming simulations using traces from the actual experiments, are carried out to validate, and characterize the performance of our proposed approach.     

无线网状网多源多径组播P2P流媒体分发

由于无线网络相邻链路间信号相互干扰,无线网状网中P2P流媒体分发不能直接利用现有有线网络P2P流媒体分发的调度算法.为提高无线网状网P2P流媒体分发质量,通过引入流媒体传输率失真模型和组播无线信号干扰模型,提出一种跨层多源多径组播调度策略,并采用改进的遗传算法对该策略进行实现.与多源多径单播调度算法相比,由于多源多径组播调度算法利用了无线网络实质采用广播方式传输数据的特点,能有效的减少流媒体数据传输冲突概率.仿真实验表明,多源多径组播调度算法更能有效的提高无线网状网P2P流媒体分发质量.     

3G网络中流媒体点对点自适应传输策略

研究3G无线网络的流媒体通信协议和性能参数,提出一种流媒体点对点自适应传输策略,包括通信链路速率估计、流媒体自适应速率控制与媒体流控制、客户端缓存反馈控制。分析结果表明,在该策略中,服务器可根据链路状况多变的3G网络特性和客户端反馈参数,自适应调节媒体速率和媒体流,从而有效避免客户端缓存的饥饿和溢出现象,达到合理利用网络带宽资源的目的。     

Wireless MediaNets: application-driven next-generation wireless IP networks

Thanks to the explosive creation of multimedia contents, the pervasive adoption of multimedia coding standards and the ubiquitous access of multimedia services, multimedia networking is everywhere in our daily lives. Unfortunately, the existing best effort IP network infrastructure, originally designed with little real-time QoS requirement, has started to suffer from performance degradation on emerging multimedia networking applications. This inadequacy problem is further deepened by the prevalence of last/first-mile wireless networking, such as Wi-Fi, mobile WiMAX, and many wireless sensors and ad-hoc networks. This can be evidenced by more and more fragmentation of application-driven IP-based networks, such as for power grid distribution, networked security surveillance, intelligent transportation communication, and many other sensor networks. To overcome the QoS challenges, the next generation wireless IP networks have to be architected in a top-down manner, i.e., application-driven layered protocol design. More specifically, based on the application media data, compression schemes are applied, the subsequent Network, MAC- and PHY-layered protocols need to be accordingly or jointly enhanced to reach the optimal performance. This is the fundamental concept behind the design of Wireless MediaNets. In this survey paper, I will address the QoS challenges specifically encountered in video over heterogeneous wireless broadband networks and address several application-driven Wireless MediaNet solutions based on effective cross-layer integration of APP and MAC/PHY layers. More specifically, the congestion control for achieving airtime fairness of video streaming to maximize the link adaptation performance of Wi-Fi, the minimum latency event-driven data exchange for distributed wireless ad-hoc sensor networks, and the opportunistic multicast of scalable video live streaming over mobile WiMAX.     

User density sensitive P2P streaming in wireless mesh networks

Link rate allocation is very important for supporting high video playback rate in Peer-to-Peer video streaming. Although many studies can be found on resource allocation in P2P streaming in wired networks, very few studies have studied the problem in wireless networks, especially in Wireless multi-hop Mesh Networks (WMNs), which is still challenging. To maximize the users’ satisfaction of P2P streaming in WMNs, this paper focuses on link rate allocation problem and proposes a fully distributed algorithm to efficiently utilize the upload and download bandwidth of wireless mesh nodes. We first build an efficient P2P streaming system based on the experimental results from real deployment of our wireless mesh testbed. Then we design an efficient distributed algorithm based on the solution to a linear optimization model, which optimizes towards a user-density-related objective to decide the best streaming rates among peers. Our scheme is resilient to network dynamics that is characteristic in wireless multi-hop peer-to-peer networks. The simulation experiments demonstrate the significant performance enhancement by using the proposed rate allocation algorithm in WMNs.     

分级的Ad Hoc网络入侵检测系统改进

随着无线网络的快速发展和移动计算应用的快速增加,移动无线网络安全问题愈加突出.入侵检测作为保证网络安全的一种有效手段已经从保护固定有线网络扩展到移动无线网络.作为无线移动网络众多实现方式之一的移动Ad Hoc网络分为平面和分级两种结构.由于其与有线网络存在很大差别,现有针对有线网络开发的入侵检测系统很难适用于移动Ad Hoc网络.本文在描述入侵检测相关技术的基础上改进了分级的AdHoc网络入侵检测系统体系结构,并给出了该系统的分簇算法,使之更好地应用于分级的Ad Hoc网络.     

一种适用于无线网络的流媒体传输机制

为保证无线网络中多媒体数据的传输质量,提出了一种适用于无线网络的流媒体传输机制（WMTCC）。该机制通过发送探测报文区分网络拥塞丢包和链路误码随机丢包,准确判断网络的拥塞状况,实施发送速率调节,保证了流媒体服务质量(QoS)。由于准确区分出无线链路误码丢包,该机制在链路误码率较高时能维持较高的网络吞吐量。仿真实验结果显示在高误码率无线网络中,该机制可以获得更高的吞吐量和更大的拥塞窗口,并且发送速率的变化更加平滑。     

Packet video transport in ATM networks with single-bit feedback

The promise of a broadband integrated service digital network has led to the design of mechanisms for efficient transport of real-time compressed video in packet switching networks. We examine feedback control for video transport in ATM networks where the available feedback is a single bit of information carried in the cell header. We investigate the performance of three single-bit schemes for source rate adaptation. Two were originally for congestion control of bursty data traffic and are modified to control video traffic. The third scheme conveys more information about the state of queue(s) at the bottleneck. The simulation results show that all three schemes for feedback control of VBR video streams work remarkably well. During severe network congestion, the signal quality degrades gracefully, but not uniformly across all connections. Based on insights from the initial simulations, we propose a scheme to improve the fairness of service and demonstrate its effectiveness.     

A novel self-tuning feedback controller for active queue management supporting TCP flows

Wireless access points act as bridges between wireless and wired networks. Since the actually available bandwidth in wireless networks is much smaller than that in wired networks, there is a bandwidth disparity in channel capacity which makes the access point a significant network congestion point. The recently proposed active queue management (AQM) is an effective method used in wired network and wired-wireless network routers for congestion control, and to achieve a tradeoff between channel utilization and delay. The de facto standard, the random early detection (RED) AQM scheme, and most of its variants use average queue length as a congestion indicator to trigger packet dropping. In this paper, we propose a Novel autonomous Proportional and Differential RED algorithm, called NPD-RED, as an extension of RED. NPD-RED is based on a self-tuning feedback proportional and differential controller, which not only considers the instantaneous queue length at the current time point, but also takes into consideration the ratio of the current differential error signal to the buffer size. Furthermore, we give theoretical analysis of the system stability and give guidelines for the selection of feedback gains for the TCP/RED system to stabilize the instantaneous queue length at a desirable level. Extensive simulations have been conducted with ns2. The simulation results have demonstrated that the proposed NPD-RED algorithm outperforms the existing AQM schemes in terms of average queue length, average throughput, and stability.     

基于RTP速率控制单元的无线视频传输控制*

第三代无线移动通信中视频传输成为重要的业务。提出了一种有线网络与无线网络边界的RTP速率控制单元方案,实现了在无线流媒体传输中有效区分拥塞丢包与无线网络信道丢包。通过仿真实验证明,此方案能够较好地判断网络状态,合理地进行速率控制和鲁棒性控制,为无线视频传输提供较高的QoS保障。     

Resource allocation for multimedia streaming over the Internet

This paper addresses the resource allocation problem for multiple media streaming over the Internet. First, we present an end-to-end transport architecture for multimedia streaming over the Internet. Second, we propose a new multimedia streaming TCP-friendly protocol (MSTFP), which combines forward estimation of network conditions with information feedback control to optimally track the network conditions. Third, we propose a novel resource allocation scheme to adapt media rate to the estimated network bandwidth using each media's rate-distortion function under various network conditions. By dynamically allocating resources according to network status and media characteristics, we improve the end-to-end quality of services (QoS). Simulation results demonstrate the effectiveness of our proposed schemes     

基于流媒体相关的视频安全组播协议(MSMP)研究

随着无线网络的快速发展和Internet中流媒体视频的巨大成功,无线网络中的视频服务有望在不久的将来得到大规模部署,无线网络上的实时流媒体传输技术已成为研究热点,而其中视频安全组播协议是一个关键问题。但是,由于无线网络中有限的带宽和有限的存储空间,外部的攻击与自适应机制带来的安全性问题在无线流媒体视频中是不可避免的。一个精心设计的密钥管理算法不仅可以明显地提高流媒体视频的性能,还能够保证可靠的数据嵌入以及实时视频应用提供安全支持。如何设计一个高效的密钥管理算法,是当前流媒体视频应用中一个备受关注的问题。针对无线视频应用,针对一个处于开放和不安全的网络环境中的自适应视频应用的密钥管理算法进行了研究,并进行了算法评价。     

无线流媒体自适应链路层HARQ控制策略

无线网络动态的信道特性、高误码率和带宽有限等特点,使得在无线环境下为实时流媒体传输提供QoS保证面临更大的挑战;提出了一种用于无线实时流媒体传输的自适应链路层HARQ控制策略,针对不同的信道状况动态选择混合ARQ方案;该策略采用跨层设计的方法,在应用层采用自适应FEC策略,在视频源数据和冗余数据之间动态分配网络带宽;数学分析和仿真验证表明,该策略能使接收方获得最大的可播放帧率,有效地提高流媒体传输的可靠性和实时性。     

Using RTT Variability for Adaptive Cross-Layer Approach to Multimedia Delivery in Heterogeneous Networks

A holistic approach should be made for a wider adoption of a cross-layer approach. A cross-layer design on a wireless network assumed with a certain network condition, for instance, can have a limited usage in heterogeneous environments with diverse access network technologies and time varying network performance. The first step toward a cross-layer approach is an automatic detection of the underlying access network type, so that appropriate schemes can be applied without manual configurations. To address the issue, we investigate the characteristics of round-trip time (RTT) on wireless and wired networks. We conduct extensive experiments from diverse network environments and perform quantitative analyses on RTT variability. We show that RTT variability on a wireless network exhibits greatly larger mean, standard deviation, and min-to-high percentiles at least 10 ms bigger than those of wired networks due to the MAC layer retransmissions. We also find that the impact of packet size on wireless channel is particularly significant. Thus through a simple set of testing, one can accurately classify whether or not there has been a wireless network involved. We then propose effective adaptive cross-layer schemes for multimedia delivery over error-prone links. They include limiting the MAC layer retransmissions, controlling the application layer forward error correction (FEC) level, and selecting an optimal packet size. We conduct an analysis on the interplay of those adaptive parameters given a network condition. It enables us to find optimal cross-layer adaptive parameters when they are used concurrently.     

无线Ad Hoc网络P2P流媒体分发缓存算法

无线Ad Hoc网络由于其传输时延较长,网络拓扑动态变化以及高丢包率,给流媒体在无线网络中的分发带来了挑战.但随着移动通信终端设备存储能力的提高,在无线Ad Hoc网络中进行P2P的流媒体分发服务成为可能.本文提出一种最小化网络总体有效传输代价的P2P流媒体分发启发式缓存算法,它是在网络总体缓存资源有限的条件下,综合考虑流媒体片段内部流行度、无线节点可靠性,以及片段实际缓存密度与期望缓存密度之差等因素,以减少流媒体分发总体传输代价为目标的启发式缓存算法,此算法能很好地减少流媒体分发起动时延,有效地减少流媒体分发在无线Ad Hoc网络中的传输代价.     

无线网络中基于流媒体传输的自适应TFRC机制

在无线网络高误码率的环境下, 经典TFRC机制会将无线误码丢包误认为拥塞丢包, 导致吞吐量过度降低. 针对无线网络实时流媒体业务的传输控制问题, 提出了一种改进型动态自适应TFRC机制(Adaptive-TFRC). 它在接收端利用丢包区分参数来真实反映网络的状态(即拥塞或者误码), 然后反馈至发送端, 同时对经典TFRC机制的吞吐量模型公式进行改进, 最终能够根据实时网络条件动态自适应地调节传输速率. 仿真结果表明, Adaptive-TFRC机制能够有效地提高网络吞吐量, 降低实时业务流的延时抖动, 同时能够进一步改善TCP业务的友好性传输, 从而保证无线网络实时流媒体的服务质量.     

煤层气集输工艺中数据传输网络技术研究

数据传输网络技术是实现煤层气安全、高效集输生产的关键环节。文章介绍了煤层气"似神经网络"集输工艺及其特点,指出了煤层气集输工艺对数据传输网络技术的具体需求;通过分析目前的数据传输网络技术,即基于有线介质的传输网络、基于GPRS的无线网络和基于3G的无线网络在煤层气集输工艺中应用存在的问题,提出了一种适合煤层气集输特点的自建无线网络架构,并分析了其技术优势,指出该自建无线网络架构为煤层气安全、高效集输提供了一种有效的数据传输手段。