14162767
Striping delay-sensitive packets over multiple burst-loss channels with random delays
Multi-homed mobile devices have multiple wireless communication interfaces, each connecting to the Internet via a long range but low speed and bursty WAN link such as a cellular link. We propose a packet striping system for such multi-homed devices - a mapping of delay-sensitive packets by an intermediate gateway to multiple channels, such that the overall performance is enhanced. In particular, we model and analyze the striping of delay-sensitive packets over multiple burst-loss channels with random delays. We first derive the expected packet loss ratio when forward error correction (FEC) is applied for error protection over multiple channels. We next model and analyze the case when the channels are bandwidth-limited with shifted-gamma-distributed transmission delays. We develop a dynamic programming-based algorithm that solves the optimal striping problem for the ARQ, the FEC, and the hybrid FEC/ARQ case.
15064150
Caching strategies in transcoding-enabled proxy systems for streaming media distribution networks
With the wide availability of high-speed network access, we are experiencing high quality streaming media delivery over the Internet. The emergence of ubiquitous computing enables mobile users to access the Internet with their laptops, PDAs, or even cell phones. When nomadic users connect to the network via wireless links or phone lines, high quality video transfer can be problematic due to long delay or size mismatch between the application display and the screen. Our proposed solution to this problem is to enable network proxies with the transcoding capability, and hence provide different, appropriate video quality to different network environment. The proxies in our transcoding-enabled caching (TeC) system perform transcoding as well as caching for efficient rich media delivery to heterogeneous network users. This design choice allows us to perform content adaptation at the network edges. We propose three different TeC caching strategies. We describe each algorithm and discuss its merits and shortcomings. We also study how the user access pattern affects the performance of TeC caching algorithms and compare them with other approaches. We evaluate TeC performance by conducting two types of simulation. Our first experiment uses synthesized traces while the other uses real traces derived from an enterprise media server logs. The results indicate that compared with the traditional network caches, with marginal transcoding load, TeC improves the cache effectiveness, decreases the user-perceived latency, and reduces the traffic between the proxy and the content origin server.
735816
An interactive video delivery and caching system using video summarization
Abstract With the advance of high-speed network technologies, the availability and popularity of streaming media content over the Internet has grown rapidly in recent years. The delivery and caching of streaming media must be handled in a different fashion than that of traditional non-streaming objects such as HTML or image files, because of its distinct characteristics and user viewing patterns. We propose a novel scheme that provides users with the video summary (a number of key-frame images) before they download the file, and options for them to select the starting playback position. We introduce the content analysis service to achieve these functionalities. The video content analysis performs shot boundary detection, key-frame selection, and face detection and tracking. The results of the processing are a segmented video sequence and an XML-based meta-data describing the video content. We also design a caching system that utilizes our video abstraction and summarization technique. Our integrated video delivery and caching system combines content-aware segmentation, prefix caching, prefetching, and cooperative caching. We describe how our scheme can be applied in three proposed caching architectures.
32056587
Improving aggregated channel performance through decentralized channel monitoring
Aggregating low-speed WAN links into a higher-speed logical link promises to improve data-transfer rates to collaborating communities of wireless mobile multihomed devices. Such bandwidth aggregation systems must adapt to link dynamics as the number of links and the channel conditions vary with time due to mobility, power dissipation, and channel interference. A monitoring architecture that accurately measures the link dynamics and promptly feeds this information to the system is vital to realize significant bandwidth aggregation performance gains. In this paper we present various architectural design alternatives for such a monitoring system, and evaluate them using both analysis and simulation. We show that a properly-designed monitoring system can accurately measure and quickly respond to changes in communication link performance while minimizing the control overhead.
6659898
On-Demand Multicast Routing Protocol in Multihop Wireless Mobile Networks
An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile ad hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation.
195352211
Distributed querying of Internet distance information
14022203
An arbitration look-ahead scheme for reducing end-to-end latency in networks on chip
With the increasing complexity of system-on-chips, networks on chip (NoC) using multi-hop switching require low end-to-end latency for QoS guarantees. An arbitration look-ahead scheme is proposed to reduce the end-to-end packet latency in the NoC. Its packet arbitration at each switch is completed a few cycles in advance of the packet arrival. As a result, a packet bypasses the switch without the latency of input queuing and arbitration. This scheme is analyzed on a 4/spl times/4 mesh topology. A maximum 65% and average 26% latency reduction are obtained under random traffic. Latency reduction up to 36% is achieved under multimedia traffic.
11234364
Robust routing in wireless ad hoc networks
A wireless ad hoc network is a collection of mobile nodes with no fixed infrastructure. The absence of a central authorization facility in dynamic and distributed environments requires collaboration among nodes. When a source searches for a route to a destination, an intermediate node can reply with its cached entry. To strengthen correctness of such a routing discovery process, we propose a method in which the intermediate node requests its next hop to send a confirmation message to the source. After receiving both a route reply and confirmation message, the source determines the validity of a path according to its policy. As a result, this strategy discourages malicious nodes from intercepting packets. Simulation results show a remarkable improvement in throughput (30% higher delivery ratio and 10% less data transmission overhead) with a moderate increase of control messages.
9314363
Feature sensitive mesh segmentation with mean shift
Feature sensitive mesh segmentation is important for many computer graphics and geometric modeling applications. In this paper, we develop a mesh segmentation method, which is capable of producing high-quality shape partitioning. It respects fine shape features and works well on various types of shapes, including natural shapes and mechanical parts. The method combines a procedure for clustering mesh normals with a modification of the mesh clarification technique. For clustering of mesh normals, we adopt Mean Shift, a powerful general purpose technique for clustering scattered data. We demonstrate advantages of our method by comparing it with two state-of-the-art mesh segmentation techniques.
18246433
FERMA: An Efficient Geocasting Protocol for Wireless Sensor Networks with Multiple Target Regions
Some sensor applications are interested in collecting data from multiple regions. For supporting such applications with multiple target regions, most conventional protocols are based on either a network flooding or multiple unicastig to cover those more than one target region. Either one will result in a lot of redundant packets to transmit by energy scared sensor nodes. To alleviate this problem, we propose a novel geocasting scheme which can make a suitable shared path among multiple target regions. We utilize the theorem of “Fermat Point,” in order to find an optimal junction point branching into each region. By using this shared path, an interest dissemination can be performed very efficiently. Our simulation study shows that the proposed scheme FERMA reduces a lot of network traffic and achieves significant energy saving as the number of target regions increase.
15089909
Image Metamorphosis with Scattered Feature Constraints
This paper describes an image metamorphosis technique to handle scattered feature constraints specified with points, polylines, and splines. Solutions to the following three problems are presented: feature specification, warp generation, and transition control. We demonstrate the use of snakes to reduce the burden of feature specification. Next, we propose the use of multilevel free-form deformations (MFFD) to compute C/sup 2/-continuous and one-to-one mapping functions among the specified features. The resulting technique, based on B-spline approximation, is simpler and faster than previous warp generation methods. Furthermore, it produces smooth image transformations without undesirable ripples and foldovers. Finally, we simplify the MFFD algorithm to derive transition functions to control geometry and color blending. Implementation details are furnished and comparisons among various metamorphosis techniques are presented.