1291895
A proxy-assisted adaptation framework for object video multicasting
Video multicast is a challenging problem due to the heterogeneous and best-effort nature of the Internet. In this paper, we present a novel video multicast framework that exploits the potential of object scalability offered by MPEG-4. Specifically, we introduce the concept of object transmission proxy (OTP), which filters incoming streams using object-based bandwidth adaptation to meet dynamic network conditions. Multiple OPTs can form an overlay network that interconnects diverse multicast islands with semi-uniform demands within each single island. We concur with the wisdom that an application best knows the utility of its data. Hence, the bandwidth-adaptation algorithm for the OTPs adaptively allocates bandwidth among video objects according to their respective utilities and then performs application-level filtering based on an effective stream classification and packetization scheme. Extensive simulation results demonstrate that our framework has substantial performance improvement over conventional bandwidth-adaptation schemes. It is particularly suitable for object-based video multicasting where the objects are of different importance.
7789260
Optimal stream replication for video simulcasting
Video simulcasting enables a sender to generate replicated streams of different rates, serving receivers of diverse access bandwidths. As replication introduces noticeable redundancy, balancing bandwidth consumption with user satisfaction becomes a critical concern in simulcasting. This paper investigates the above issue; more explicitly, we seek answers to the following two questions: what is the number of streams that should be generated, and what is the bandwidth that should be allocated to each stream? We derive optimal and efficient solutions, and evaluate their performance under a variety of configurations. The results demonstrate that an optimal and adaptive bandwidth allocation significantly improves user satisfaction under stringent resource constraints, and an optimal choice of the stream number yields further improvements.
14806639
A unified framework for resource discovery and QoS-aware provider selection in ad hoc networks
With the rising popularity of network-based applications and the potential use of mobile ad hoc networks in civilian life, an efficient resource discovery service is needed in such networks for quickly locating resource providers. In addition, to improve user experience, QoS awareness is also crucial. In this paper, we identify the challenges when basic resource discovery techniques for the Internet are used in mobile ad hoc networks. We then propose a framework that provides a unified solution to the discovery of resources and QoS-aware selection of resource providers. The key entities of this framework are a set of self-organized discovery agents. These agents manage the directory information of resources using hash indexing. They also dynamically partition the network into domains and collect intra- and inter-domain QoS information to select appropriate providers. Simulation results show that our framework improves the QoS delivered to the clients, while the cost and response time are kept at a low level.
14992487
COPACC: An Architecture of Cooperative Proxy-Client Caching System for On-Demand Media Streaming
Proxy caching is a key technique to reduce transmission cost for on-demand multimedia streaming. The effectiveness of current caching schemes, however, is limited by the insufficient storage space and weak cooperation among proxies and their clients, particularly considering the high bandwidth demands from media objects. In this paper, we propose COPACC, a cooperative proxy-and-client caching system that addresses the above deficiencies. This innovative approach combines the advantages of both proxy caching and peer-to-peer client communications. It leverages the client-side caching to amplify the aggregated cache space and rely on dedicated proxies to effectively coordinate the communications. We propose a comprehensive suite of distributed protocols to facilitate the interactions among different network entities in COPACC. It also realizes a smart and cost-effective cache indexing, searching, and verifying scheme. Furthermore, we develop an efficient cache allocation algorithm for distributing video segments among the proxies and clients. The algorithm not only minimizes the aggregated transmission cost of the whole system, but also accommodates heterogeneous computation and storage constraints of proxies and clients. We have extensively evaluated the performance of COPACC under various network and end-system configurations. The results demonstrate that it achieves remarkably lower transmission cost as compared to pure proxy-based caching with limited storage space. On the other hand, it is much more robust than a pure peer-to-peer communication system in the presence of node failures. Meanwhile, its computation and control overheads are both kept in low levels
18232832
Tree-assisted gossiping for overlay video distribution
Given its readily deployable nature and broad applications for digital entertainment, video streaming through overlay networks has received much attention recently. While a tree topology is often advocated due to its scalability, it suffers from discontinuous playback under highly dynamic network environments. For on-demand streaming, the asynchronicity among client requests further aggravates the problem. On the other hand, gossip protocols using random message dissemination, though robust, fail to meet the real-time constraints for streaming applications. In this paper, we propose TAG, a Tree-Assisted Gossip protocol that addresses the above issues. TAG adopts a tree structure with time indexing to accommodate asynchronous requests, and an efficient pull-based gossip algorithm to mitigate the impact of network dynamicity. It seamlessly integrates these two approaches and realizes their best features, namely, low delay with a regular tree topology, and robust delivery with smart switching among multiple paths, thus making effective use of the available bandwidth in the network. We evaluate the performance of TAG under various settings, and the results demonstrate that it is quite robust in the presence of local and global bandwidth fluctuations. As compared to pure tree-based overlay VOD system, it achieves much lower and stable segment missing rates, even under highly dynamic network conditions.
12033351
mTreebone: A Hybrid Tree/Mesh Overlay for Application-Layer Live Video Multicast
Application-layer overlay networks have recently emerged as a promising solution for live media multicast on the Internet. A tree is probably the most natural structure for a multicast overlay, but is vulnerable in the presence of dynamic end-hosts. Data-driven approaches form a mesh out of overlay nodes to exchange data, which greatly enhances the resilience. It however suffers from an efficiency-latency tradeoff, given that the data have to be pulled from mesh neighbors with periodical notifications. In this paper, we suggest a novel hybrid tree/mesh design that leverages both overlays. The key idea is to identify a set of stable nodes to construct a tree-based backbone, called treebone, with most of the data being pushed over this backbone. These stable nodes, together with others, are further organized through an auxiliary mesh overlay, which facilitates the treebone to accommodate node dynamics and fully exploit the available bandwidth between overlay nodes. This hybrid design, referred to as mTreebone, is braced by our real trace studies, which show strong evidence that the performance of an overlay closely depends on a small set of backbone nodes. It however poses a series of unique and critical design challenges, in particular, the identification of stable nodes and seamless data delivery using both push and pull methods. In this paper, we present optimized solutions to these problems, which reconcile the two overlays under a coherent framework with controlled overhead. We evaluate mTreebone through both simulations and PlanetLab experiments. The results demonstrate the superior efficiency and robustness of this hybrid solution.
5220045
A study of the performance and parameter sensitivity of adaptive distributed caching
A self-organized approach to manage a distributed proxy system called Adaptive Distributed Caching (ADC) has been proposed previously [8]. We model each proxy as an autonomous agent that is equipped to decide how to deal with client requests using local information. Experimental results show that our ADC algorithm is able to compete with typical hashing-based approaches. This paper gives a full description of the self-organizing distributed algorithm, with a performance comparison based on hits and hops rate. Additional evaluation of the parameters caching-, multiple- and single-table size is also presented.
30869604
Towards Efficient Data Re-mining (DRM)
The problem that we tackle here is a practical one: When users interactively mine association rules, it is often the case that they have to continuously tune two thresholds: minimum support and minimum confidence, which describe the users' changing requirements. In this paper, we present an efficient data re-mining (DRM) technique for updating previously discovered association rules in light of threshold changes.
33401134
Distributed Group Management for Track Initiation and Maintenance in Target Localization Applications
The tradeoff between performance and scalability is a fundamental issue in distributed sensor networks. In this paper, we propose a novel scheme to efficiently organize and utilize network resources for target localization. Motivated by the essential role of geographic proximity in sensing, sensors are organized into geographically local collaborative groups. In a target tracking context, we present a dynamic group management method to initiate and maintain multiple tracks in a distributed manner. Collaborative groups are formed, each responsible for tracking a single target. The sensor nodes within a group coordinate their behavior using geographically-limited message passing. Mechanisms such as these for managing local collaborations are essential building blocks for scalable sensor network applications.
10016971
Improved bottleneck domination algorithms
W.C.K. Yen introduced BOTTLENECK DOMINATION and BOTTLENECK INDEPENDENT DOMINATION. He presented an O(n log n + m)- time algorithm to compute a minimum bottleneck dominating set. He also obtained that the BOTTLENECK INDEPENDENT DOMINATING SET problem is NP-complete, even when restricted to planar graphs.We present simple linear time algorithms for the BOTTLENECK DOMINATING SET and the BOTTLENECK TOTAL DOMINATING SET problem. Furthermore, we give polynomial time algorithms (most of them with linear time-complexities) for the BOTTLENECK INDEPENDENT DOMINATING SET problem on the following graph classes: AT-free graphs, chordal graphs, split graphs, permutation graphs, graphs of bounded treewidth, and graphs of clique-width at most k with a given k-expression.
4908568
Insignificant shadow detection for video segmentation
To prevent moving cast shadows from being misunderstood as part of moving objects in change detection based video segmentation, this paper proposes a novel approach to the cast shadow detection based on the edge and region information in multiple frames. First, an initial change detection mask containing moving objects and cast shadows is obtained. Then a Canny edge map is generated. After that, the shadow region is detected and removed through multiframe integration, edge matching, and region growing. Finally, a post processing procedure is used to eliminate noise and tune the boundaries of the objects. Our approach can be used for video segmentation in indoor environment. The experimental results demonstrate its good performance.