6754979
Real-time processing of range-monitoring queries in heterogeneous mobile databases
Unlike conventional range queries, a range-monitoring query is a continuous query. It requires retrieving mobile objects inside a user-defined region and providing continuous updates as the objects move into and out of the region. In this paper, we present an efficient technique for real-time processing of such queries. In our approach, each mobile object is associated with a resident domain, and when an object moves, it monitors its spatial relationship with its resident domain and the monitoring areas inside it. An object reports its location to the server when it crosses over some query boundary or moves out of its resident domain. In the first case, the server updates the affected query results accordingly, while in the second case, the server determines a new resident domain for the object. This distributive approach achieves an accurate and real-time monitoring effect with minimal mobile communication and server processing costs. Our approach also allows a mobile object to negotiate a resident domain based on its computing capability. By having a larger resident domain, a more capable object has less of a chance of moving out of it and having to request a new one. As a result, both communication and server processing costs are reduced. Our comprehensive performance study shows that the proposed technique can be highly scalable in supporting location-based services in a wireless environment that consists of a large number of mobile devices.
7607384
Sharing Location Dependent Experiences in MANET
This paper investigates a new problem of sharing location dependent experiences among mobile hosts in mobile adhoc networks. An experience is location and observer dependent. In other words, experiences of different people witnessing the same event may be quite different. The ability to retrieve prior experiences observed in a given area in advance is very useful for newcomers wishing to enter the same vicinity. Solving this problem is vital for important applications such as hurricane rescue missions, combat missions, and deep space or deep sea exploration. In this paper, we propose a distributed solution that lets mobile hosts share their experiences efficiently. Our simulation results show that our approach significantly outperforms a centralized approach.
10931244
Sharing Multicast Videos Using Patching Streams
The access patterns of most information systems follow the 80/20 rules. That is, 80% of the requests are for 20% of the data. A video server can take advantage of this property by waiting for requests and serving them together in one multicast. This simple strategy, however, incurs service delay. We address this drawback in this paper by allowing clients to receive the leading portion of a video on demand, and the rest of the video from an ongoing multicast. Since clients do not have to wait for the next multicast, the service latency is essentially zero. Furthermore, since most services require the server to deliver only a small leading portion of the video, the server can serve many more clients per time unit. We analyze the performance of this approach, and determine the optimal condition for when to use this strategy. We compare its performance to a hardware solution called Piggybacking. The results indicate that more than 200% improvement is achievable.
271858
Providing scalable on-demand video services for heterogeneous receivers
To provide scalable video-on-demand services, precious system bandwidth must be shared among video requests. Although many efficient bandwidth-sharing techniques have been proposed, they are all designed for homogeneous receivers, i.e., the clients are assumed to have the same receiving bandwidth. For networks with client heterogeneity, these techniques either cannot work or have to compromise their performance. In this paper, we address this problem and propose an efficient solution allowing each client to use its whole receiving bandwidth to download data. To serve a client, the server first selects a set of serving channels for the client according to its actual receiving bandwidth. The video data needed for this client are then scheduled and dynamically adjusted for delivery over these channels. We evaluate the performance of the new technique using simulation and compare it with an existing scheme. Our study shows that by effectively leveraging client heterogeneity, the new technique achieves significantly smaller service latency
8030523
Video management in peer-to-peer systems
Providing scalable video services in a peer-to-peer (P2P) environment is challenging. Since videos are typically large and require high communication bandwidth for delivery, many peers may be unwilling to cache them in whole to serve others. In this paper, the authors addressed two fundamental research problems in providing scalable P2P video services, namely (1) how a host can find enough video pieces, which may scatter among the whole system, to assemble a complete video, and (2) given a limited buffer size, what part of a video a host should cache. A new distributed video management technique was proposed. This scheme organizes hosts into a number of cells, each of which is a distinct set of hosts which together can supply a video in its entirety. A client looking for a video can stop its search as soon as it finds a host that caches any part of the video. Caching operations can be coordinated within each cell to balance data redundancy in the system. The extensive study on a Gnutella-like simulation network shows convincingly the performance advantage of the new scheme.
9627520
Processing range-monitoring queries on heterogeneous mobile objects
We consider in this paper how to leverage heterogeneous mobile computing capability for efficient processing of real-time range-monitoring queries. In our environment, each mobile object is associated with a resident domain and when an object moves, it monitors its spatial relationship with its resident domain and the monitoring areas inside it. An object reports its location to server whenever its movement affects any query results (i.e., crossing any query boundaries) or it moves out of its resident domain. In the first case, the server updates the affected query results accordingly while in the second case, the server determines a new resident domain for the object. This distributive approach is able to provide accurate query results and real-time monitoring updates with minimal location update and server processing costs. In addition, the new scheme allows a mobile object to negotiate a resident domain based on its computing capability. Thus, a more capable object can have a larger resident domain reducing its chance of having to request a new resident domain because of moving out of it. This feature makes the new approach highly adaptive to the heterogeneity of mobile objects. In our performance study, we compare it with an existing approach using simulation. The study shows that the new technique is many times better in reducing mobile communication and server processing costs.
8404482
LSWS: A Linux-based Secure Web Switch
7788842
Information hiding interfaces for aspect-oriented design
The growing popularity of aspect-oriented languages, such as AspectJ, and of corresponding design approaches, makes it important to learn how best to modularize programs in which aspect-oriented composition mechanisms are used. We contribute an approach to information hiding modularity in programs that use quantified advising as a module composition mechanism. Our approach rests on a new kind of interface: one that abstracts a crosscutting behavior, decouples the design of code that advises such a behavior from the design of the code to be advised, and that can stipulate behavioral contracts. Our interfaces establish design rules that govern how specific points in program execution are exposed through a given join point model and how conforming code on either side should behave. In a case study of the HyperCast overlay network middleware system, including a real options analysis, we compare the widely cited oblivious design approach with our own, showing significant weaknesses in the former and benefits in the latter.
7290210
Modular software design with crosscutting interfaces
Aspect-oriented programming (AOP) languages such as AspectJ offer new mechanisms and possibilities for decomposing systems into modules and composing modules into systems. The key mechanism in AspectJ is the advising of crosscutting sets of join points. An aspect module uses a pointcut descriptor (PCD) to declaratively specify sets of points in program executions. Our approach employs crosscut programming interfaces, or XPIs. XPIs are explicit, abstract interfaces that decouple aspects from details of advised code