6021546
Leveraging 1-hop neighborhood knowledge for efficient flooding in wireless ad hoc networks
Flooding is a fundamental and frequently invoked operation in wireless ad hoc networks. Existing flooding techniques either are unreliable, generate overwhelming unnecessary retransmission, or incur excessive network control overhead. In this paper, we address these crucial problems and propose a new flooding technique called edge forwarding. The new scheme minimizes the flooding traffic by leveraging location information to limit broadcast retransmission to only hosts near the perimeter of each broadcast coverage. Unlike most existing techniques, edge forwarding requires each host to track only neighboring nodes within its one-hop distance. Therefore, it is more adaptive to host mobility and incurs less network control overhead. In particular, it can be easily incorporated into many existing routing protocols without any additional control overhead. Our performance studies indicate that with our strategy, a substantial portion of the unnecessary broadcast retransmission can be eliminated.
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
6815479
A generalized target-driven cache replacement policy for mobile environments
Caching frequently accessed data items on the client side is an effective technique to improve system performance in a mobile environment. Due to cache size limitations, cache replacement algorithms are used to find a suitable subset of items for eviction from the cache. In this paper, we propose a generalized cost function for cache replacement algorithms for mobile environment. The distinctive feature of our cost function is that it is general and it can be used for various performance metrics by making the necessary changes. To demonstrate the practical effectiveness of the general cost function, we derive two specific functions to be evaluated by setting two different targets: minimizing the query delay and minimizing the downlink traffic. Detailed experiments are carried out to evaluate the proposed methodology. Compared to previous schemes, our algorithm significantly improves the performance in terms of query delay or in terms of bandwidth utilization depending on the targets.
39535676
A generalized target-driven cache replacement policy for mobile environments
Caching frequently accessed data items on the client side is an effective technique to improve the system performance in wireless networks. Due to cache size limitations, cache replacement algorithms are used to find a suitable subset of items for eviction from the cache. Many existing cache replacement algorithms employ a value function of different factors such as time since last access, entry time of the item in the cache, transfer time, item expiration time and so on. However, most of the existing algorithms are designed for WWW environment under weak consistency model. Their choices of value functions are based on experience and on a value function which only works for a specific performance metric. In this paper, we propose a generalized value function for cache replacement algorithms for wireless networks under a strong consistency model. The distinctive feature of our value function is that it is generalized and can be used for various performance metrics by making the necessary changes. Further, we prove that the proposed value function can optimize the access cost in our system model. To demonstrate the practical effectiveness of the generalized value function, we derive two specific functions and evaluate them by setting up two different targets: minimizing the query delay and minimizing the downlink traffic. Compared to previous schemes, our algorithm significantly improves the performance in terms of query delay or in terms of bandwidth utilization depending on the specified target.
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.
14591533
Leveraging broadband access for true on-demand delivery of Internet videos
We consider in this paper how the increasingly popular broadband access can be leveraged for scalable and cost-effective video service. Although much work has been done for such service, the existing techniques either are not designed for on-demand video delivery, or do not take into account the vastly improved client receiving capability. In this paper, we address this problem and develop three novel video delivery techniques with two ultimate goals: minimizing service latency and maximize data sharing. With the new techniques, a client can be served as soon as server resource becomes available and meanwhile, all its receiving bandwidth can be used for data receiving. In particular, in the proposed dynamic scheduling algorithm, the efficiency of data sharing is further improved by also exploring server bandwidth for early delivery of video segments. This innovation is contradicted to the intuition that each video segment should be delivered as late as possible in order to maximize data sharing. We evaluate the performance of our new techniques using simulation and our study convincingly shows that with the new schemes, zero service latency can indeed be achieved with very minimal system resource.
28503947
An integrated approach with feedback control for robust Web QoS design
There is a growing demand for provisioning of different levels of quality of service (QoS) on scalable Web servers to meet changing resource availability and to satisfy different client requirements. In this paper, we investigate the problem of providing proportional QoS differentiation with respect to response time on Web servers. We first present a processing rate allocation scheme based on the foundations of queueing theory. It provides different processing rates to requests of different client classes so as to achieve the differentiation objective. At application level, process is used as the resource allocation principal for achieving processing rates on Apache Web servers. We design and implement an adaptive process allocation approach, guided by the queueing-theoretical rate allocation scheme, on an Apache server. This application-level implementation, however, shows weak QoS predictability because it does not have fine-grained control over the consumption of resources that the kernel consumes and hence the processing rate is not strictly proportional to the number of processes allocated. We then design a feedback controller and integrate it with the queueing-theoretical approach. It adjusts process allocations according to the difference between the target response time and the achieved response time using a proportional integral derivative controller. Experimental results demonstrate that this integrated approach can enable Web servers to provide robust proportional response time differentiation.
16856059
An Area-Based Collaborative Sleeping Protocol for Wireless Sensor Networks
An effective approach for energy conservation in wireless sensor networks is putting redundant sensor nodes to sleep while the active nodes provide certain degree of coverage. This paper presents an Area-based Collaborative Sleeping protocol (ACOS) that can control the degree of coverage for diverse applications. The ACOS protocol, based on the net sensing area of a sensor, controls the mode of sensors to maximize the coverage, minimize the energy consumption, and to extend the lifetime of the sensor network. The net sensing area of a sensor is the area of the region exclusively covered by the sensor itself. We study the parameter tuning in ACOS to guide to configure the network for diverse applications. The simulation shows that our protocol has better coverage of the surveillance area while waking fewer sensors than other sleeping protocols. It extends the lifetime of sensor networks significantly
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.
6311601
An adaptive process allocation strategy for proportional responsiveness differentiation on Web servers
There is a growing demand for provisioning of different levels of quality of service (QoS) on scalable Web servers to meet changing resource availability and satisfy different client requirements. The proportional differentiation model is getting momentum because of its fairness and differentiation predictability. It states that QoS of different traffic classes should be kept proportional to their pre-specified differentiation parameters, independent of the class loads. In this paper, we present a processing rate allocation scheme for providing proportional response time differentiation on Web servers. A challenging issue is how to achieve processing rates for different request classes in the implementation. We propose a process allocation strategy, which dynamically and adaptively changes the number of processes allocated for handling different request classes while ensuring the ratios of process allocation specified by the processing rate allocation scheme. We implement the process allocation strategy at application level on Apache Web servers. Experimental results show that the processing rate can be achieved by the adaptive process allocation strategy and the Web servers can provide predictable and controllable proportional response time differentiation.
11155724
Non-modularity in aspect-oriented languages: integration as a crosscutting concern for AspectJ
Aspect-oriented (AO) methods and languages seek to enable the preservation of design modularity through mappings to program structures, especially where common (object-oriented) languages fail to do so. The general claim is made that AO approaches enable the modularization of crosscutting concerns. The problem that we address is that it is unclear to what extent such claims are valid. We argue that there are meaningful bounds on the abilities of past, present, and future languages to succeed in this regard---bounds that we need to understand better. To make this idea concrete we exhibit a significant bound: Component integration (Sullivan & Notkin 1992, 1994) is not adequately modularizable in AspectJ