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1.
Broadcasting scheme with low client buffers and bandwidths for video-on-demand applications 总被引:1,自引:1,他引:0
Hsiang-Fu Yu Hung-Chang Yang Yao-Tien Wang Ping-Lin Fan Chu-Yi Chien 《Multimedia Tools and Applications》2009,42(3):295-316
Efficient data broadcasting is independent of request arrivals, and is thus highly promising when transmitting popular videos.
A conventionally adopted broadcasting method is periodic broadcasting, which divides a popular video into segments, which
are then simultaneously broadcast on different data channels. Once clients want to watch the video, they download the segments
from these channels. The skyscraper broadcasting (SkB) scheme supports clients with small bandwidths. An SkB client requires
only two-channel bandwidths to receive video segments. This work proposes a reverse SkB (RSkB) scheme, which extends SkB by
reducing buffering spaces. The RSkB is mathematically shown to achieve on-time video delivery and two-channel client bandwidths.
A formula for determining the maximum number of segments buffered by an RSkB client is presented. Finally, an analysis of
RSkB reveals that its client buffer requirements are usually 25–37% lower than SkB. Extensive simulations of RSkB further
demonstrate that RSkB yields lower client buffer demand than other proposed systems.
相似文献
Hsiang-Fu YuEmail: |
2.
Design and analysis of a look-ahead scheduling scheme to support pause-resume for video-on-demand applications 总被引:1,自引:0,他引:1
In a video-on-demand (VOD) system, subscribers can choose both the movie they wish to view and the time they wish to view it. In such an environment there are invariably hot videos which are requested by many viewers. The requirement that each viewer be able to independently pause the video at any instant and later resume the viewing with little delay can cause difficulties in batching viewers for each showing. Under batching, a single video stream is shared by multiple concurrent viewers and a resume request has to wait for additional stream capacity to become available before actual resumption can occur. The conventional approach to the support of on-demand pause-resume provides one video access stream to disks for each video request. This can greatly increase the disk arm requirements of a VOD system. In this paper, we propose a more efficient mechanism to support the pause-resume feature usinglook-ahead scheduling withlook-aside buffering. The idea is to use buffering to increase the number of concurrent viewers supportable. The concept of look-ahead scheduling is not to back up each viewer with a real stream capacity so he can pause and resume at any time, but rather with a (look-ahead) stream that is currently being used for another showing which is close to completion. Before the look-ahead stream becomes available, the pause and resume features have to be supported by the original stream through (look-aside) buffering of the missed content. It is shown via simulations that the proposed scheme can provide a substantially greater throughput than the approach without batching. Furthermore, for a given amount of buffer, the improvement in throughput grows more than linearly with the stream capacity of the server. In other words, the look-ahead stream scheduling scheme operates with good economy of scale because it is easier to form look-ahead streams for video servers with larger stream capacity. 相似文献
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Hsiang-Fu Yu 《Multimedia Tools and Applications》2014,70(3):2369-2385
Periodic broadcasting is a cost-effective solution for the large-scale distribution of popular videos. This strategy guarantees constant worst service latency to all clients, regardless of the number of video requests. The practical channel transition broadcasting (PCTB) scheme is an essential periodic broadcasting method that can dynamically add or release broadcasting channels (i.e., channel transition) according to video popularity. However, PCTB experiences bandwidth waste when performing channel transition. This study further finds that PCTB yields transition playback latency during channel addition. Therefore, an enhanced version referred to as PCTB+ is proposed to cause less bandwidth waste and lower transition playback latency. The applicability of this new scheme is verified, and an analytical evaluation is provided to demonstrate its performance advantage. The new scheme reduces bandwidth waste by 50 % to 100 % compared to the original PCTB scheme. Moreover, PCTB+ yields 50 % smaller transition playback latency than PCTB. The proposed scheme outperforms the seamless fast broadcasting (SFB) scheme for bandwidth waste under most conditions. No extra startup latency and client buffer demand are required when using PCTB+. 相似文献
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The major drawback of the existing cluster placement scheme is the long response time caused by admission control if the
number of clusters and the number of users are large. A circular skip-cluster placement scheme is proposed to reduce the size
of the data buffer as well as the system response time. Furthermore, the popularity of each video is different in the real
world. We propose a new popularity-based data allocation scheme to allocate data units within a cluster such that the corresponding
data units of these popular videos are stored in those cylinders at one end of each cluster. Due to a higher spatial locality
within these hot cylinders, some data units requested by the users are stored in the same cylinder such that one seek operation,
one rotation, and one transfer operation are required to retrieve these data units. Therefore, the time required to retrieve
data for these requests can be reduced, thus also reducing the system response time. Based on our results, the buffer size
and the system response time can be reduced by half or more. These findings are essential for constructing video-on-demand
systems that provide satisfactory performance. 相似文献
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In this work, we introduce a cross-layer framework to favor the video-on-demand service in multi-hop WiMax mesh networks. We first propose a joint solution of admission control and channel scheduling for video streams. The proposed approach guarantees that the required data rate is achieved for video streams, which is crucial for multimedia streaming applications. An efficient and light-weight multicast routing technique is also proposed to minimize the bandwidth cost of joining a multicast tree. Furthermore, we adopt the Patching technique in the application layer to improve the capacity of the video server. Overall, the quality of the video-on-demand service is dramatically improved with the help of the efficient cooperation between the techniques proposed in different layers of the network. Simulation study shows that with the proposed approach, true video-on-demand in WiMax mesh networks can be achieved under high video request arrival rate. 相似文献
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Arne Roggensack 《Calcolo》2013,50(4):255-282
In this paper, a kinetic method to compute approximative solutions of the one-dimensional open channel flow equations with a varying cross-sectional area and a varying bottom profile is proposed. The scheme preserves the steady states at rest, keeps the water height non-negative and is able to handle dry channel beds. These three properties are essential indicators for the quality of a numerical scheme. The ability of the scheme to treat varying cross-sectional areas along the channel is an important advancement in comparison to previous papers. Further the same equations are considered on a network by coupling the equations at the nodes. The main difference to the majority of common numerical hydraulic models is the usage of the energy equality as coupling condition which seems to be more realistic than conditions based on the water height. Moreover, we set up a numerical method for computing subcritical flow on such networks. Several examples are treated to illustrate the results. 相似文献
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Mobility support for Wireless Sensor Networks (WSN) can significantly extend the use of WSN in many fields, such as industrial control, healthcare and smart home. And high-efficiency mobility support schemes are essential for WSN because this is a typical energy constrained network. This paper proposes a LoW cost inter-PAN Mobility Support Scheme (LoWMS) for IPv6 based WSN, which follows the network based idea. The scheme aims at reducing signaling cost when sensor nodes move between two Personal Area Networks. In order to realize it, the handoff related control messages are designed to transmit in link layer, and resolution for ping-pong handoff is also given. Simulation results show the novel scheme efficiently reduces the amount of handoff messages, which is benefit for energy saving of WSN. At the end of the paper, we illustrate two possible application scenarios which could be beneficial from LoWMS, one is healthcare system, and another is logistics and storage. 相似文献
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一种面向无线传感器网络协同任务分配的动态联盟更新机制 总被引:4,自引:0,他引:4
在面向目标追踪等应用的无线传感器网络研究中,协同任务分配机制的研究是很重要的.基于动态联盟机制的协同任务分配方法是事件触发的.适用于任务出现频率相对较低的大规模无线传感器网络.本文在基于动态联盟机制研究的基础上,首先引入了联盟覆盖范围和休眠盟员的概念,进一步消除针对同一任务的检测传感器节点的冗余,降低系统的能量消耗;而后又给出了一种动态联盟的更新机制,以保证动态联盟执行任务时的连续性,在一定程度上保证网络的检测性能.最后通过仿真,从系统总能耗、目标捕获率和检测误差标准差等方面检验了算法的性能,并给出了缓冲带宽度等参数对能耗和网络检测性能的影响. 相似文献
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Communication support for distributed collaborative applications 总被引:1,自引:0,他引:1
The development of distributed, multimedia, collaborative applications requires the resolution of communication issues such as concurrency control and temporal and causal synchronization of traffic over related data streams. Existing transport and/or session-layer protocols do not include the desired support for multistream, multipoint communication. In this paper, we propose new communication abstractions and mechanisms that facilitate the implementation of the necessary coordination and concurrency control semantics in a collaborative application. We propose a protocol suite called themultiflow conversation protocol (MCP) for the realization of these abstractions and describe its prototype implementation in an internetwork of workstations. The paper also describes our experience with the prototype and results of a performance evaluation. 相似文献
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异构无线传感器网络中基于模拟退火算法的成本最优部署机制 总被引:1,自引:0,他引:1
针对异构传感器网络节点的高密度部署和监测目标非均匀分布的情况,提出了一种基于模拟退火算法的成本最优部署方法.算法在保证网络覆盖和容错性的条件下,以异构节点部署成本最小为优化目标进行操作.仿真结果表明该算法能快速收敛于最优解,有效降低网络部署的成本,提高了目标监测质量. 相似文献
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Asgari Samane Jamali Shahram Fotohi Reza Nooshyar Mahdi 《The Journal of supercomputing》2021,77(11):12209-12229
The Journal of Supercomputing - Network functions virtualization (NFV) is a new concept that has received the attention of both researchers and network providers. NFV decouples network functions... 相似文献
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This paper presents a model for building context-based systems in pervasive computing environments from high level specifications. A pervasive computing environment is viewed as a collaboration space consisting of mobile users, system services, and sensors and resources embedded in the physical environment. The approach presented here is developed for building collaborative activities in which users and environment services cooperate towards some shared objectives and tasks. The specification model allows expression of policies related to context-based discovery and secure access of resources, and role-based interactions among users and environmental services. Using several examples we illustrate the capabilities of our specification model for expressing various kinds of context-based requirements for resource access and user interactions. 相似文献
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Lizhe WangAuthor Vitae Dan ChenAuthor Vitae Fang HuangAuthor Vitae 《Computers & Electrical Engineering》2011,37(3):300-310
Grid computing has become an effective computing technique in recent years. This paper develops a virtual workflow system to construct distributed collaborative applications for Grid users. The virtual workflow system consists three levels: abstract workflow system, translator and concrete workflow system. The research highlight of the implementation is that this workflow system is developed based on CORBA and Unicore Grid middleware. Furthermore, this implementation can support legacy application developed with Parco and C++ codes. This virtual workflow system can provide efficient GUI for users to organize distributed scientific collaborative applications and execute them on Grid resources. We present the design, implementation, and evaluation of this virtual workflow system in the paper. 相似文献
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《国际计算机数学杂志》2012,89(2):454-473
Two-way chaining is a novel hashing scheme with separate chaining that achieves O(log log n) expected maximum search time, when Θ(n) data points are hashed via two independent uniform hash functions into a table of size n. In this note, we consider the two-way chaining scheme in the fixed density model, where the hashing values behave according to two fixed but possibly different densities on [0, 1]. 相似文献