VIRAL: coupling congestion control with fair video quality metric

Video streaming is often carried out by congestion controlled transport protocols to preserve network sustainability. However, the success of the growth of such non-live video flows is linked to the user quality of experience. Thus, one possible solution is to deploy complex quality of service systems inside the core network. Another possibility would be to keep the end-to-end principle while making aware transport protocols of video quality rather than throughput. The objective of this article is to investigate the latter by proposing a novel transport mechanism which targets video quality fairness among video flows. Our proposal, called VIRAL for virtual rate-quality curve, allows congestion controlled transport protocols to provide fairness in terms of both throughput and video quality. VIRAL is compliant with any rate-based congestion control mechanisms that enable a smooth sending rate for multimedia applications. Implemented inside TFRC a TCP-friendly protocol, we show that VIRAL enables both intra-fairness between video flows in terms of video quality and inter-fairness in terms of throughput between TCP and video flows.     

A unified framework for distributed video rate allocation over wireless networks

When multiple video streams share a wireless network, careful rate allocation is needed to prevent congestion, as well as to balance the video qualities among the competing streams. In this paper, we present a unified optimization framework for video rate allocation over wireless networks. Our framework applies to both unicast and multicast sessions, and accommodates both scalable and non-scalable streams. The optimization objective is to minimize the total distortion of all video streams without incurring excessive network utilization. Our system model explicitly accounts for heterogeneity in wireless link capacities, traffic contention among neighboring links, as well as different video rate-distortion (RD) characteristics. The proposed distributed media-aware rate allocation scheme leverages cross-layer information exchange between the MAC and application layers to achieve fast convergence at the optimal allocation.We evaluate performance of the proposed scheme for streaming of high-definition (HD) and standard-definition (SD) video sequences over 802.11-based wireless networks, both in unicast and multicast scenarios. The scheme consistently outperforms conventional TCP-Friendly Rate Control (TFRC) in terms of overall video quality, and achieves more balanced qualities among the streams.     

TFRC friendliness and the case of ECN

The TFRC protocol has been proposed as a TCP‐friendly protocol to transport streaming media over the Internet. However, its deployment is still questionable because it has not been compared to other important protocols, analysed in the presence of important mechanisms, such as the explicit congestion notification (ECN), and studied under more realistic network conditions. In this paper, we address these three aspects, including other congestion control protocols not considered before in the same investigation, such as TCP Tahoe, Reno, Newreno, Vegas, Sack, GAIMD, and the Binomial algorithms, the effect of using ECN in the friendliness of the protocols, and the fairness of the protocols under static and dynamic network conditions. We found that TFRC can be safely deployed in the Internet if competing with TCP Tahoe, New Reno and SACK since fairness is achieved under all scenarios considered. We also found that ECN actually helps in achieving better fairness. However, fairness problems arise when TFRC competes with TCP Reno, GAIMD, SQRT or IIAD in static or dynamic conditions, or both. We used normalized throughput, fairness index, and convergence time as the main performance metrics for comparison. Copyright © 2004 John Wiley & Sons, Ltd.     

End-to-end optimized TCP-friendly rate control for real-time video streaming over wireless multi-hop networks

Rate control is an important issue in video streaming applications. The most popular rate control scheme over wired networks is TCP-Friendly Rate Control (TFRC), which is designed to provide optimal transport service for unicast multimedia delivery based on the TCP Reno’s throughput equation. It assumes perfect link quality, treating network congestion as the only reason for packet losses. Therefore, when used in wireless environment, it suffers significant performance degradation because of packet losses arising from time-varying link quality. Most current research focuses on enhancing the TFRC protocol itself, ignoring the tightly coupled relation between the transport layer and other network layers. In this paper, we propose a new approach to address this problem, integrating TFRC with the application layer and the physical layer to form a holistic design for real-time video streaming over wireless multi-hop networks. The proposed approach can achieve the best user-perceived video quality by jointly optimizing system parameters residing in different network layers, including real-time video coding parameters at the application layer, packet sending rate at the transport layer, and modulation and coding scheme at the physical layer. The problem is formulated and solved as to find the optimal combination of parameters to minimize the end-to-end expected video distortion constrained by a given video playback delay, or to minimize the video playback delay constrained by a given end-to-end video distortion. Experimental results have validated 2–4 dB PSNR performance gain of the proposed approach in wireless multi-hop networks by using H.264/AVC and NS-2.     

Rate control for streaming video over wireless

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 TCP-friendly rate control (TFRC) (Floyd, 2000). It 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. 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 main cause of packet loss is at the physical layer. In this article we review existing approaches to solve this problem. Then 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 a 1/spl times/RTT CDMA wireless data network, and video streaming simulations using traces from the actual experiments are carried out to characterize the performance and show the efficiency of our proposed approach.     

JTCP: jitter-based TCP for heterogeneous wireless networks

Transmission control protocol (TCP), a widely used transport protocol performs well over the traditional network which is constructed by purely wired links. As wireless access networks are growing rapidly, the wired/wireless mixed internetwork, a heterogeneous environment will get wide deployment in the next-generation ALL-IP wireless networks. TCP which detects the losses as congestion events could not suit the heterogeneous network in which the losses will be introduced by higher bit-error rates or handoffs. There exist some unsolved challenges for applying TCP over wireless links. End-to-end congestion control and fairness issues are two significant factors. To satisfy these two criteria, we propose a jitter-based scheme to adapt sending rates to the packet losses and jitter ratios. The experiment results show that our jitter-based TCP (JTCP) conducts good performance over the heterogeneous network.     

TFRC协议友好性与平稳性改进算法研究

 本文针对TFRC(TCP-Friendly Rate Control)流与TCP流竞争带宽时的友好性问题,分析了影响TFRC协议TCP友好性的因素,通过对TFRC速率计算公式中丢包率的不同幂级项引入权重系数,增加网络拥塞严重时的发送速率,减少网络拥塞较轻时的发送速率,从而降低了网络拥塞程度对TFRC流传输速率的影响.仿真实验表明该方法对TFRC协议具有较明显改进作用,提高了TFRC流的传输平稳度和TCP友好性,从而能更有效地适应多媒体流的传输要求.     

Joint Channel Assignment and Routing for Throughput Optimization in Multiradio Wireless Mesh Networks

Multihop infrastructure wireless mesh networks offer increased reliability, coverage, and reduced equipment costs over their single-hop counterpart, wireless local area networks. Equipping wireless routers with multiple radios further improves the capacity by transmitting over multiple radios simultaneously using orthogonal channels. Efficient channel assignment and routing is essential for throughput optimization of mesh clients. Efficient channel assignment schemes can greatly relieve the interference effect of close-by transmissions; effective routing schemes can alleviate potential congestion on any gateways to the Internet, thereby improving per-client throughput. Unlike previous heuristic approaches, we mathematically formulate the joint channel assignment and routing problem, taking into account the interference constraints, the number of channels in the network, and the number of radios available at each mesh router. We then use this formulation to develop a solution for our problem that optimizes the overall network throughput subject to fairness constraints on allocation of scarce wireless capacity among mobile clients. We show that the performance of our algorithms is within a constant factor of that of any optimal algorithm for the joint channel assignment and routing problem. Our evaluation demonstrates that our algorithm can effectively exploit the increased number of channels and radios, and it performs much better than the theoretical worst case bounds     

混合网络下的TCP拥塞控制跨层优化算法

针对混合网络中并行链路间TCP流的不公平性,提出一种新的算法.此算法利用跨层设计的思想,以传输层的数据重传率为参数来调整TCP流不公平性,也就是说MAC层上的竞争窗口将根据重传率的动态变化而改变,其目的在于抑制并行链路TCP流接入信道能力的不公平性.并且用仿真工具NS2进行仿真的结果表明,采用改进算法后的网络公平性指数比未改进前提高了17.9％.该算法能明显改善并行链路间TCP流的不公平性.     

Game of protocols: Is QUIC ready for prime time streaming?

Quick User Datagram Protocol (UDP) Internet Connections (QUIC) is an experimental and low‐latency transport protocol proposed by Google, which is still being improved and specified in the Internet Engineering Task Force (IETF). The viewer's quality of experience (QoE) in HTTP adaptive streaming (HAS) applications may be improved with the help of QUIC's low‐latency, improved congestion control, and multiplexing features. We measured the streaming performance of QUIC on wireless and cellular networks in order to understand whether the problems that occur when running HTTP over TCP can be reduced by using HTTP over QUIC. The performance of QUIC was tested in the presence of network interface changes caused by the mobility of the viewer. We observed that QUIC resulted in quicker start of media streams, better streaming, and seeking experience, especially during the higher levels of congestion in the network and had a better performance than TCP when the viewer was mobile and switched between the wireless networks. Furthermore, we measured QUIC's performance in an emulated network that had a various amount of losses and delays to evaluate how QUIC's multiplexing feature would be beneficial for HAS applications. We compared the performance of HAS applications using multiplexing video streams with HTTP/1.1 over multiple TCP connections to HTTP/2 over one TCP connection and to QUIC over one UDP connection. To that effect, we observed that QUIC provided better performance than TCP on a network that had large delays. However, QUIC did not provide a significant improvement when the loss rate was large. Finally, we analyzed the performance of the congestion control mechanisms implemented by QUIC and TCP, and tested their ability to provide fairness among streaming clients. We found that QUIC always provided fairness among QUIC flows, but was not always fair to TCP.     

基于网络选择的视频通信带宽博弈算法

针对异构无线网络的视频通信提出一种基于网络选择的带宽博弈算法(BAG-NS)。该算法首先根据不同用户视频特性及当前网络状况,采用层次分析法和熵值法确定网络评价参数的权重,选择最佳网络;其次构建了基于收益和代价的用户效用函数,通过分布式迭代算法得到其纳什均衡解,并证明了纳什均衡的存在性和唯一性。仿真结果表明,该算法使不同特性的视频用户合理地分布在不同网络,能兼顾用户公平性和网络拥塞控制,增加网络资源利用率,减小用户视频失真,提高用户视频质量。     

PASA: power adaptation for starvation avoidance to deliver wireless multimedia

In recent years, there has been an increasing interest to deliver multimedia services over wireless ad hoc networks. Due to the existence of hidden terminal and absence of central control, the medium access control protocol as used in the ad hoc networks may lead to channel capture, where some flows monopolize the channel while others suffer from starvation. As a consequence, the system throughput and fairness are greatly degraded. After showing that static power control leads to channel capture, we propose and study a distributed dynamic power control scheme termed "power adaptation for starvation avoidance" (PASA), which dynamically adjusts the transmission power of a node so as to avoid starvation. PASA is shown to be effective in breaking channel captures, hence improving short-term fairness among contending flows. It is simple, fully autonomous and requires no communication overhead. Via extensive simulations, we show that our power control algorithm achieves much better fairness without compromising system throughput through better spatial reuse. Our experiments with video sequences transmitting over different network topologies show that PASA achieves much better video quality with lower start-up delay and buffer requirement.     

End-to-end loss differentiation for video streaming with wireless link errors

Video delivery in heterogeneous wired/wireless networks is challenging, since link errors commonly degrade throughput performance, smoothness, and eventually impair the playback quality. We present an end-to-end Loss Differentiation Mechanism (LDA) which effectively decouples congestion from wireless loss in order to abolish the damage of error-induced multiplicative decrease on flow throughput and smoothness. The proposed LDA relies on Round Trip Time measurements to estimate the queuing delay and determine the appropriate error-recovery strategy. This mechanism can be easily adapted and incorporated into existing Additive Increase Multiplicative Decrease (AIMD) protocols, enabling them to utilize the available resources more efficiently. In this context, we incorporate the LDA into AIMD-based Scalable Streaming Video Protocol (SSVP), an end-to-end TCP-friendly protocol optimized for video streaming applications. Based on simulation results, we show that the combined approach provides the desired functionality to bind operationally wired and wireless links, within the framework of bandwidth efficiency, smoothness, and fairness.     

A novel adaptive logic for dynamic adaptive streaming over HTTP

In this paper, we propose an estimation method that estimates the throughput of upcoming video segments based on variations in the network throughput observed during the download of previous video segments. Then, we propose a rate-adaptive algorithm for Hypertext Transfer Protocol (HTTP) streaming. The proposed algorithm selects the quality of the video based on the estimated throughput and playback buffer occupancy. The proposed method selects high-quality video segments, while minimizing video quality changes and the risk of playback interruption, improving user’s experience. We evaluate the algorithm for single- and multi-user environments and demonstrate that it performs remarkably well under varying network conditions. Furthermore, we determine that it efficiently utilizes network resources to achieve a high video rate; competing HTTP clients achieve equitable video rates. We also confirm that variations in the playback buffer size and segment duration do not affect the performance of the proposed algorithm.     

Power management adaptation techniques for video transmission over TFRC

In this paper, we describe power management adaptation techniques for wireless video transmission using the TCP Friendly Rate Control (TFRC) protocol that take into account feedback about the received video quality and try to intelligently adapt transmitting power accordingly. The purpose of the mechanisms is to utilize TFRC feedback and thus achieve a beneficial balance between power consumption and the received video quality. There are two power adaptation mechanisms proposed, each one with its own advantages. They both offer significant improvements when used in terms of both power consumption and received video quality. We use simulation in order to compare and evaluate our approach. Copyright © 2011 John Wiley & Sons, Ltd.     

TCP-BIAD for Enhancing TCP Performance in Broadband Wireless Access Networks

In this paper a new TCP variant, named TCP-Binary Increase, Adaptive Decrease is presented. The suggested congestion control algorithm is a joint approach of Westwood and an enhanced version of BIC, for improving TCP performance in broadband wireless access networks. BIAD has been evaluated with respect to other TCP variants such as Reno, Westwood, BIC, CUBIC, HSTCP and STCP with the use of network simulator 2. The results indicate that the proposed solution achieves high network utilization levels in a wide range of network settings, including wireless channel errors, link asymmetry and congestion. We also evaluated TCP-BIAD when multiple flows share a bottlenecked access link and we show that it demonstrates the fairness features required for network deployment.     

Achieving inter-session fairness for layered video multicast

The Internet is increasingly used to deliver multimedia services. Since there are heterogeneous receivers and changing network conditions, it has been proposed to use adaptive rate control techniques such as layered video multicast to adjust the video traffic according to the available Internet resources. A problem of layered video multicast is that it is unable to provide fair bandwidth sharing between competing video sessions. We propose two schemes, layered video multicast with congestion sensitivity and adaptive join-timer (LVMCA) and layered video multicast with priority dropping (LVMPD), to achieve inter-session fairness for layered video multicast. Receiver-driven layered multicast (RLM), layer-based congestion sensitivity, LVMCA, and LVMPD are simulated and compared. Results show both proposed schemes, especially LVMPD, are fairer and have shorter convergence time than the other two schemes.     

Improving Transport Layer Performance in Multihop Ad Hoc Networks by Exploiting MAC Layer Information

The traditional TCP congestion control mechanism encounters a number of new problems and suffers a poor performance when the IEEE 802.11 MAC protocol is used in multihop ad hoc networks. Many of the problems result from medium contention at the MAC layer. In this paper, we first illustrate that severe medium contention and congestion are intimately coupled, and TCP's congestion control algorithm becomes too coarse in its granularity, causing throughput instability and excessively long delay. Further, we illustrate TCP's severe unfairness problem due to the medium contention and the tradeoff between aggregate throughput and fairness. Then, based on the novel use of channel busyness ratio, a more accurate metric to characterize the network utilization and congestion status, we propose a new wireless congestion control protocol (WCCP) to efficiently and fairly support the transport service in multihop ad hoc networks. In this protocol, each forwarding node along a traffic flow exercises the inter-node and intra-node fair resource allocation and determines the MAC layer feedback accordingly. The end-to-end feedback, which is ultimately determined by the bottleneck node along the flow, is carried back to the source to control its sending rate. Extensive simulations show that WCCP significantly outperforms traditional TCP in terms of channel utilization, delay, and fairness, and eliminates the starvation problem     

无线网络中TCP友好流媒体传输改进机制

为保持无线网络中多媒体业务对TCP的友好性，提出了一种适用于无线网络的动态自适应的流媒体传输速率调节机制。该机制通过在接收端区分网络拥塞丢包和链路错误随机丢包，准确判断网络的拥塞状况结合接收端缓存区占用程度，自适应实施多级速率调节，实现了TCP流友好性和流媒体服务质量（QoS）的折中。由于准确区分出无线链路误码丢包和动态调整流媒体QoS要求，该机制能维持较高的网络利用率。仿真实验结果显示在连接数为2和32，链路误码率从0到0．1变化时TCP,TFRC和吞吐量幅度下降幅度较大，WTFCC幅度下降相对较慢，最大相差达2M；在网络负载重时，尽管链路误码率较低，WTFCC区分链路错误与拥塞丢包，因此，端到端丢包率高于TCP和TFRC，但整体传输吞吐量也高于两者。归一化吞吐量显示WTFCC对TCP流友好。