一种分层P2 P流媒体系统重叠网的构建策略

基于Peer-to-Peer(P2P)技术的流媒体应用具有部署效率高及可扩展性好等突出优势。而采用分层视频编码技术的P2P流媒体系统把原视频流分解为多个视频层数据进行分发,让节点能够选择与自己带宽资源相匹配的视频质量,使其很好地适应节点的异构性。但是各分层视频数据传输的路径存在较大差异,使重叠网构建策略面临更大的挑战。因此定义了基于分层视频编码技术环境下的P2P流媒体重叠网络构建问题,并证明该问题是一个NP难问题。提出了一种构建重叠网的集中启发式算法,同时还提出了一种基于视频组(Streaming Group)的分布式重叠网络构建策略。通过大规模网络仿真实验验证了基于该分布式重叠网构建策略的分层流媒体系统具备低服务器带宽占用、高数据获取率等优点。     

Enhancing multi-hop communication over multi-radio multi-channel wireless mesh networks: A cross-layer approach

The multi-channel multi-radio technology represents a straightforward approach to expand the capacity of wireless mesh networks (WMNs) in broadband wireless access scenarios. However, the effective leveraging of this technology in WMNs requires (i) enhanced MAC protocols, to coordinate the access to multiple channels with a limited number of radio interfaces, and (ii) efficient channel allocation schemes, to mitigate the impact of co-channel interference. The design of channel assignment schemes and MAC protocols is strictly interrelated, so that joint design should be considered to optimize the mesh network performance. In this paper, a channel assignment and fast MAC architecture (CAFMA) is proposed, which exploits the benefits provided by the multi-channel multi-radio technology to (i) enhance the performance of multi-hop communications, (ii) maximize the resource utilization, and (iii) support differentiation of traffic classes with different quality of service (QoS) requirements. CAFMA is designed with a cross-layer approach and includes (1) a novel MAC scheme, which provides multi-channel coordination and fast data relaying over multi-hop topologies, and (2) a distributed channel allocation scheme, which works in cooperation with the routing protocol. Simulation results confirm the effectiveness of CAFMA when compared with other single-layer and cross-layer solutions for multi-radio multi-channel WMNs.     

QoS optimal real-time video streaming in distributed wireless image-sensing platforms

This paper provides a novel real-time video streaming method in distributed wireless image-sensing platforms. It consists of (1) a millimeter-wave (mmW)-based multi-hop routing optimization for real-time video streaming, (2) wireless image-sensing platforms by using the high-efficiency video coding. A mmW wireless communication is a promising technology for increasing capacity in next-generation wireless systems. However, the weakness of mmW signals to (1) do long-distance transmission and (2) survive in non-line-of-sight environments makes the mmW networks need a multi-hop relaying. Thus, this paper focuses on the maximization of video transmission quality of service (QoS) that makes the optimization problem different from the conventional sum-rate maximization. Specifically, this paper develops an algorithm that optimizes the summation of QoS of the individual wireless transmission of different video streams, subject to constraints of separate streams (i.e., minimum requirements in each stream). Experimental results show the proposed approach presents 32 % better performance with 1.84 dB gain in Y-peak signal-to-noise ratio than the widely used max–min flow routing that is generally considered in QoS-sensitive video streaming applications.     

P2P流媒体中的数据分配算法

最近兴起的P2P技术在充分利用客户资源、提高系统的可伸缩性方面具有巨大的潜力,基于P2P提供视频服务已成为Internet的一项重要应用.在多对单P2P模式下,对多个发送端最优地分配发送速率和数据是一个难题.为此,提出了一种新的分配算法.首先,应用排队论把最优速率分配问题模型化为非线性最优化问题,推导出求解最优化问题的速率分配公式;然后,基于该公式提出最优速率分配算法(ORAA),并对ORAA输出解的最优性给出证明;最后,提出动态速率分配算法(DRAA).DRAA对动态的网络环境具有自适应性,能根据网络条件的变化最优地为多个发送端进行速率和数据分配.仿真实验结果表明,在不同的参数条件下,DRAA算法减少了计算和通信开销,比同类算法有更好的性能.     

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.     

Diverse community: Demand differentiation in P2P live streaming

Peer-to-Peer (P2P) technology has become an attractive approach for enabling large-scale video streaming applications, but the factor of users’ subjective preferences is not paid enough attention in such networks. As users have various demand on video qualities, we can provide them with video streams at different resolutions without impairing their satisfaction. The adaptive streaming rate technique is a promising method. However, in providing adaptive streaming rate services, P2P live streaming design faces the following challenge: how to provide all users with uninterrupted video with their desired qualities in case that their demand dynamically changes? To shed more light on this problem, we first derive a model and formulate the problem as a resource demand vs supply problem. Then we present a framework to address the challenge via efficient bandwidth allocation and group cooperation. Through comprehensive simulations, we evaluate the effectiveness of the proposed framework, and conclude that it effectively helps existing solutions, such as Partial Participation Scheme (PPS), achieve better performance.     

An efficient scheduling algorithm for scalable video streaming over P2P networks

During recent years, the Internet has witnessed rapid advancement in peer-to-peer (P2P) media streaming. In these applications, an important issue has been the block scheduling problem, which deals with how each node requests the media data blocks from its neighbors. In most streaming systems, peers are likely to have heterogeneous upload/download bandwidths, leading to the fact that different peers probably perceive different streaming quality. Layered (or scalable) streaming in P2P networks has recently been proposed to address the heterogeneity of the network environment. In this paper, we propose a novel block scheduling scheme that is aimed to address the P2P layered video streaming. We define a soft priority function for each block to be requested by a node in accordance with the block’s significance for video playback. The priority function is unique in that it strikes good balance between different factors, which makes the priority of a block well represent the relative importance of the block over a wide variation of block size between different layers. The block scheduling problem is then transformed to an optimization problem that maximizes the priority sum of the delivered video blocks. We develop both centralized and distributed scheduling algorithms for the problem. Simulation of two popular scalability types has been conducted to evaluate the performance of the algorithms. The simulation results show that the proposed algorithm is effective in terms of bandwidth utilization and video quality.     

无线mesh网络中效用与链路强度联合优化的覆盖多播

支持多播通信是无线mesh网络(WMNs)的一个重要应用.采用基于效用的定价机制,通过拉格朗日(Lagrange)对偶分解法获得一个基于价格的分布式算法.以该分布式算法为核心,作为mesh网络中数据流速率和链路强度调整的优化策略,每条链路根据自己的拥塞状况合理地定价,通过价格机制来调节链路的强度和数据流的速率,使网络净效用最大化.实验结果表明该算法是有效可行的.     

Realizing and benchmarking broadcast algorithms in wireless mesh networks

Broadcasting by flooding causes the broadcast storm problem in multi-hop wireless networks. This problem becomes more likely in a wireless mesh network (WMN) because WMNs can bridge wired LANs, increasing broadcast traffic and collision probability. Since the network control, routing, and topology maintenance of a WMN highly rely on layer-2 broadcasting, unreliable broadcast algorithms directly destabilize a WMN. Researchers have developed many algorithms for efficient and reliable broadcast in multi-hop wireless networks. However, real-world systems rarely verify or compare these approaches, especially in a WMN. This paper examines six representative broadcast algorithms: simple flooding, dynamic probabilistic, efficient counter-based broadcast, scalable broadcast, domain pruning, and connected-dominating-set based algorithms. This study addresses both common and algorithm-specific implementation in a real-world IEEE 802.11s WMN testbed. Experiments under various topologies and packet lengths reveal the reliability, forwarding ratio, and efficiency of these six algorithms. Quantitative survey results indicate that the scalable broadcast algorithm possesses the best reliability due to its lower collision probability. The domain-pruning algorithm is the most efficient algorithm when considering both reliability and the forwarding ratio.     

一种基于P2P点组技术的流媒体协作计算

分析了流媒体技术的现状和问题，讨论了在P2P环境下的流媒体多点分布式调度技术和调度性能分析，以及多点调度下的带宽分配算法，最后给出了一个基于P2P点组的流媒体协作调度模型。     

P2P流媒体网络的关键节点识别算法

P2P流媒体网络中普遍存在一些关键节点,关键节点对网络的安全和通信性能起着重要作用,识别网络中的关键节点尤为重要,而传统方法对于大规模网络的关键节点识别时间开销很大,无法保证实时性。提出P2P流媒体网络中的关键节点识别算法,结合混合模式的网络结构特点,采用分区域的计算模型解决网络规模过大造成的巨大时间开销问题,根据节点的贡献度和传播能力差异定量化描述节点的重要性程度。仿真结果表明,所提算法可以快速获得节点重要性排序,有效识别P2P流媒体网络中的关键节点。     

An incentive scheduling mechanism for peer-to-peer video streaming

P2P video streaming networks are found as a scalable solution and an alternative for traditional client–server based video streaming over the Internet. One of the significant issues affecting the success of any P2P streaming network is cooperation between peers. Practical observations have proved the prevalence of free riders in P2P networks that degrade their performance. To solve this problem, using incentive mechanisms, which encourage peers to contribute more in the network, is necessary. In this paper, we designed and proposed a distributed and scalable incentive mechanism for mesh based P2P video streaming networks. In the proposed approach the contribution of the peers is measured and maintained in a distributed fashion. Furthermore, we proposed an incentive sending side scheduler in which peers are served based on their contribution in the network. Our simulation evaluations show the efficiency of the proposed approach in improving the overall perceived video quality by the non-free rider nodes and consequently in the whole network.     

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。     

无线多跳网络联合拥塞控制和功率分配的快速二阶算法

针对节点功率受限的无线多跳网络,研究业务流路由确知时的联合功率分配、流量分配和拥塞控制问题,并基于原始对偶内点法设计一种具有二阶收敛性能的算法.该算法利用矩阵分裂方法实现业务流源速率和节点功率的分布式更新,最终优化网络效用.仿真结果表明,算法能有效降低网络中的功率消耗,提高网络的能量效用,同时相较于传统拉格朗日对偶分解法,所提出算法具有非常好的收敛性能.     

Load-balanced AP association in multi-hop wireless mesh networks

Wireless mesh networks (WMNs) provide high-bandwidth wireless access, which makes it capable for multimedia services. A user in a WMN may be covered by multiple APs, while it should be associated with only one to access the Internet. Conventional IEEE 802.11 user-AP association mechanism for WLANs employs signal strength as the sole metric. However, this may lead to network congestion and performance degradation in multi-hop networks such as WMNs, especially for multimedia services that require a large bandwidth and a low latency. Thus AP association in WMNs becomes an important research issue. In this paper we propose a novel AP association approach LBAA, taking AP’s load-balancing, WMN’s multi-hop characteristic, and user’s RSSI into consideration. We first propose a centralized algorithm and then extend it to a distributed one, with the latter one more practical and convenient for deployment. Network throughput and max–min user fairness are improved by LBAA. Performance evaluation demonstrating the benefits of our approach is given through a series of experiments in terms of collision probability, access bandwidth, end-to-end throughput, and average RSSI.     

一种基于信源信道联合的最优速率分配算法

针对视频数据在无线信道上可靠传输问题,提出了一种基于信源信道联合的最优速率分配算法。该算法在网络带宽一定的情况下,从信源、信道及差错弹性能力权衡考虑,引入了信源解码器的抗误码性能指标,根据不同的信道状态确定信源信道编码的最优速率分配方案,从而获得最大的可解码长度,并最终获取最佳重建视频质量。仿真结果表明,该方案与传统的联合信源信道速率分配算法相比可获得更高的性能增益,适合于视频数据在无线网络上传输。     

On the end-to-end flow allocation and channel assignment in multi-channel multi-radio wireless mesh networks with partially overlapped channels

The performance of wireless mesh networks (WMNs) can be improved significantly with the increase in number of channels and radios. Despite the availability of multiple channels in several of the current wireless standards, only a small fraction of them are non-overlapping and many channels are partially overlapped. In this paper, we formulate the joint channel assignment and flow allocation problem for multi-channel multi-radio WMNs as a Mixed Integer Linear Program (MILP). Unlike most of the previous studies, we consider the case when both non-overlapped and partially overlapped channels are being used. We consider an objective of maximizing aggregate end-to-end throughput and minimizing queueing delay in the network, instead of the sum of link capacities, since the traffic characteristics of a multi-hop WMN are quite different from a single hop wireless network. Our static channel assignment algorithm incorporates network traffic information, i.e., it is load aware. Our formulation takes into consideration several important network parameters such as the transmission power of each node, path loss information, the signal to interference plus noise ratio at a node, and the frequency response of the filters used in the transmitter and receiver. We show by simulations that our MILP formulation makes efficient use of the spectrum, by providing superior channel assignments and flow allocations with the addition of partially overlapped channels, without the use of any additional spectrum. We also justify the need to consider alternative objective functions such as, minimizing average queueing in the network. We also propose a polynomially bounded heuristic algorithm to scale the proposed algorithm to bigger network topologies.     

率失真优化的无线多跳网络多路径选择算法

随着无线网络技术的发展,基于无线多跳网的视频通信在智能交通、灾难应急和军事指挥等多个领域得到越来越广泛的应用.但是,如何保证无线视频的传输质量,是亟待解决的一个关键问题.已有多路径视频传输研究忽略了信道变化和路径间干扰.针对该问题,提出一种基于率失真预测的多路径选择优化算法.该算法不仅分析了网络拥塞对传输质量的影响,而...     

Adaptive content-and-deadline aware chunk scheduling in mesh-based P2P video streaming

In mesh-based Peer-to-Peer (P2P) live video streaming systems packet scheduling is an important factor in overall video playback quality. In mesh based P2P video streaming systems, each video sequence is divided into chunks, which are then distributed by multiple suppliers to the receivers. The suppliers need to be coordinated by the receiver through specifying a transmission schedule for each of them. Many previous studies on scheduling of P2P streaming tend to mainly focus on networking issues which strongly depend on a particular P2P architecture such as tree or mesh. These algorithms suffer from some design issues: 1) they are too complex to deploy, 2) they do not take video characteristics into account and 3) they do not have sender-side transmission policy. To address all three of these problems, we propose a new chunk scheduling scheme which consists of two parts: i) receiver-side scheduler and ii) sender-side transmission order scheme. The proposed receiver-side scheduler considers the contribution level of each video frame as well as the frame’s urgency in order to define a priority for each video frame. It attempts to request frames with highest priority from peers which can deliver them in a shorter time. We also design a new chunk transmission order scheme that decides which requested chunk will be sent out first based on its importance to the requesting neighbor. Our simulation results show that the proposed scheduling scheme improves the overall quality of the perceived video in mesh-based P2P video streaming architectures substantially.     

SRPM: Secure Routing Protocol for IEEE 802.11 Infrastructure Based Wireless Mesh Networks

Infrastructure based IEEE 802.11 wireless mesh networks (WMNs) are new paradigm of low cost broadband technology. The large scale city-wide community-based coverage and multi-hop architecture are such characteristics which are vulnerable to network layer threats, and the adversary can exploit them for large scale degradation of the broadband services. So far many secure routing protocols have been proposed for ad-hoc networks, however, due to the different nature and characteristics; they cannot perform well in a WMN environment. In this paper, we discuss the limitations and challenges as well as propose an exclusive secure routing protocol for an infrastructure based wireless mesh (SRPM) network. SRPM is robust against a variety of multi-hop threats and performs well over a range of scenarios we tested.