62612563
Enabling location-based services in wireless LAN hotspots
The wide deployment of IEEE 802.11 Wireless LAN (WLAN) makes possible application services developed in WLAN hotspots. Owing to the small cell size in WLAN hotspots, it is practical to develop location-based services with the awareness of the WLAN access points (APs) that mobile devices currently access. In this paper, we propose an effective location determination technique using the inherent SNMP support in WLAN APs. It is shown that the current location of a mobile device can be determined from the SNMP traps sent by APs. Since the SNMP-based approach doesn't need any particular software or hardware in mobile devices, location-based services can be widely deployed, especially in public WLAN hotspots. To further enable location-based services through the WWW, this paper also considers the location determination of a mobile device from its IP address, retrieved in a WWW environment. In addition, we propose a web service framework for location-based services in WLAN hotspots. Thus, location-based services can be developed in a standard way.
8884051
Constant Time Sorting on Reconfigurable Meshes
We present a constant time sorting algorithm by adopting a 3D reconfigurable mesh with only O(n/sup 3/2/) processors. Our algorithm is developed on an n/sup 1/2//spl times/n/sup 1/2//spl times/n/sup 1/2/ 3-D reconfigurable mesh. Moreover, we further extend the result to k-dimensional reconfigurable meshes for k/spl ges/3. Consequently, an O(4/sup k+1/) time sorting algorithm is obtained by adopting an n/sup 1/(k-1)//spl times/n/sup 1/(k-1)//spl times/.../spl times/n/sup 1/(k-1)/k-D reconfigurable mesh of size O(n/sup 1+1/(k-1)/). Hence, constant time sorting using O(n/sup 1+/spl epsiv//) processors, where O >
44397360
Reducing Time Complexities of Semigroup Computations on Mesh-Connected Computers with Multiple Broadcasting
14989858
Logic of Global Synchrony
An intermediate-level specification notation, Logs, is presented for PRAM/BSP-style programming. It extends pre-post style semantics to reveal state at points of global synchronization before termination (if that occurs). The result is an integration of the pre-post, finite and reactive-process styles of specification and in particular an extension of standard BSP. The language is provided with a complete set of laws, formulated to benefit from a simple predicative semantics and to be quite close to programming intuition. The language is compositional, and parallel composition is simply logical conjunction. Use of Logs, and of the laws for reasoningab out it, is demonstrated on the problem of the dining philosophers.
18849054
An enhanced buffer management scheme for fast handover protocol
The integration of IEEE 802.11 wireless LAN and mobile IP technologies offers an affordable and high bandwidth solution for host mobility. When applying the hierarchical mobile IP for fast handover, the performance bottleneck on mobile IP and potential disconnection during handoff period can be greatly improved. However, the fast handover protocol suffers several problems such as scalability and QoS support for lacking a buffer management mechanism. We propose an enhanced buffer management scheme for fast handover. By means of the proposed scheme, we are able to improve the buffer utilization on routers as well as to support QoS services during a handoff process. Using the ns-2 simulator, we have demonstrated the significance and effectiveness of our proposed scheme.
5860855
A distributed buffer management approach supporting IPv6 mobility
In wireless local area networks (WLAN), mobility support is essential for providing seamless services. The current Mobile IP standard suffers several problems, especially for accommodating real-time media applications. Most of the existing studies focus on improving the performance between the home agent (HA) and foreign agent (FA). In this work, we propose a buffer management approach to enhance the performance between the mobility agent (HA or FA) and the mobile node (MN). The proposed scheme deals with the packet delivery between MA and MN in Layer 2. Through the simulation, we show that our scheme improves TCP throughput as well as reducing the UDP packet loss rate. Moreover, its implementation is feasible in both IPv4 and IPv6, and suitable for supporting quality of service (QoS).
5375789
Clustering Web content for efficient replication
Recently, there has been an increasing deployment of content distribution networks (CDNs) that offer hosting services to Web content providers. We first compare uncooperative pulling of Web contents, used by commercial CDNs, with cooperative pushing. The latter can achieve user perceived performance comparable to the former scheme with only 4-5% of replication and update traffic. Therefore, we explore how to push content to CDN nodes efficiently. Using trace-driven simulation, we show that replicating content in units of URLs can yield 60-70% reduction in clients' latency, compared to replicating in units of Web sites. However, such a fine-grained replication is very expensive. We propose to replicate content in units of clusters, each containing objects which are likely to be requested by clients that are topologically close. We describe three clustering techniques, and use various topologies and several large Web server traces to evaluate their performance. Cluster-based replication achieves 40-60% improvement over per Web site based replication. By adjusting the number of clusters, we can smoothly trade off the management and computation cost for better client performance. We also explore incremental clusterings that adaptively add new documents to the existing content clusters. We examine both offline and online incremental clusterings. The offline clusterings yield close to the performance of the complete re-clustering at much lower overhead. The online incremental clustering and replication cut down the retrieval cost by 4.6-8 times compared to no replication and random replication, so it is especially useful for improving document availability during flash crowds.
5924956
On joining and caching stochastic streams
We consider the problem of joining data streams using limited cache memory, with the goal of producing as many result tuples as possible from the cache. Many cache replacement heuristics have been proposed in the past. Their performance often relies on implicit assumptions about the input streams, e.g., that the join attribute values follow a relatively stationary distribution. However, in general and in practice, streams often exhibit more complex behaviors, such as increasing trends and random walks, rendering these "hardwired" heuristics inadequate.In this paper, we propose a framework that is able to exploit known or observed statistical properties of input streams to make cache replacement decisions aimed at maximizing the expected number of result tuples. To illustrate the complexity of the solution space, we show that even an algorithm that considers, at every time step, all possible sequences of future replacement decisions may not be optimal. We then identify a condition between two candidate tuples under which an optimal algorithm would always choose one tuple over the other to replace. We develop a heuristic that behaves consistently with an optimal algorithm whenever this condition is satisfied. We show through experiments that our heuristic outperforms previous ones.As another evidence of the generality of our framework, we show that the classic caching/paging problem for static objects can be reduced to a stream join problem and analyzed under our framework, yielding results that agree with or extend classic ones.