551942
Shape Dimension and Approximation from Samples 


Abstract. There are many scientific and engineering applications where an automatic detection of shape dimension from sample data is necessary. Topological dimensions of shapes constitute an important global feature of them. We present a Voronoi-based dimension detection algorithm that assigns a dimension to a sample point which is the topological dimension of the manifold it belongs to. Based on this dimension detection, we also present an algorithm to approximate shapes of arbitrary dimension from their samples. Our empirical results with data sets in three dimensions support our theory.

7021110
Approximating the Medial Axis from the Voronoi Diagram with a Convergence
Guarantee
Abstract
The medial axis of a surface in 3D is the closure of all points that
have two or more closest points on the surface. 
It is an essential geometric structure in a number of applications involving 
3D geometric shapes. Since exact computation of the medial axis
is difficult in general, efforts continue to improve their approximations.
Voronoi diagrams turn out to be useful for this
approximation. Although it is known that Voronoi vertices for a sample
of points from a curve in 2D 
approximate its medial axis, a similar result does not hold
in 3D. Recently, it has been discovered that only a subset
of Voronoi vertices converge to the medial axis
as sample density approaches infinity. However, most applications
need a nondiscrete approximation as opposed to a discrete one. To date
no known algorithm can compute this approximation straight
from the Voronoi diagram with a guarantee of convergence. We present
such an algorithm and its convergence analysis in this 
paper. One salient feature of the algorithm is that it is
scale and density independent.
Experimental results corroborate our theoretical claims.


16064988
Enhancing Service Location Protocol for efficiency, scalability and advanced discovery
This paper presents three new mechanisms for the Service Location Protocol (SLP): mesh enhancement, preference filters and global attributes. The mesh enhancement simplifies Service Agent (SA) registrations and improves consistency among Directory Agents (DAs) by defining an interaction scheme for DAs and supporting automatic registration distribution among peer DAs. Preference filters facilitate processing of search results (e.g., finding the best match) in SLP servers (DAs and SAs) to reduce the amount of data transferred to the client for saving network bandwidth. Global attributes allow using a single query to search services across multiple types. These mechanisms can improve SLP efficiency and scalability and support advanced discovery such as discovering multi-access-point services and multi-function devices. We expect that these techniques can also be applied to other service discovery systems.
2852415
Differentiated services with statistical real-time guarantees in static-priority scheduling networks
We propose and analyze a methodology for providing absolute differentiated services with statistical performance guarantees for real-time applications in networks that use class-based (as opposed to flow-aware) static priority schedulers. We develop a method that can be used to derive statistical delay guarantees in a flow-unaware fashion. Traditionally, both deterministic and statistical delay analysis methods either depend on schedulers that keep per-flow state information, or require detailed information about flow population at delay analysis time. The fact that no such information is needed for delay analysis allows us to perform deadline tests during system (re-)configuration time. We are so able to reduce the runtime admission control to a simple utilization test. No explicit delay computation is necessary at admission time, making this approach scalable to large systems.
6507373
The timed-token protocol for real-time communications
The timed-token protocol is a token-passing protocol in which each node receives a guaranteed share of the network bandwidth. Partly because of this property, the timed-token protocol has been incorporated into a number of network standards, including the IEEE 802.4 token bus, the Fiber Distributed Data Interface (FDDI), and the Survivable Adaptable Fiber Optic Embedded Network (Safenet). Networks based on these standards are becoming increasingly popular in new generation real-time systems. In particular, the IEEE 802.4 standard is included in the Manufacturing Automation Protocol (MAP), which has been widely used in computer-integrated manufacturing and industrial applications. Meeting message deadlines requires proper control of medium access. In the timed-token protocol, access to the communication medium is controlled by a token that is passed among the nodes in a circular fashion. Messages are segregated into two separate classes: synchronous and asynchronous. Synchronous messages, used for real-time communication, can have deadline constraints and thus are given a guaranteed share of the network bandwidth. The authors focus on meeting the deadlines of synchronous messages.<<ETX>>
6109299
A message ferrying approach for data delivery in sparse mobile ad hoc networks
Mobile Ad Hoc Networks (MANETs) provide rapidly deployable and self-configuring network capacity required in many critical applications, e.g., battlefields, disaster relief and wide area sensing. In this paper we study the problem of efficient data delivery in sparse MANETs where network partitions can last for a significant period. Previous approaches rely on the use of either long range communication which leads to rapid draining of nodes' limited batteries, or existing node mobility which results in low data delivery rates and large delays. In this paper, we describe a Message Ferrying (MF) approach to address the problem. MF is a mobility-assisted approach which utilizes a set of special mobile nodes called message ferries (or ferries for short) to provide communication service for nodes in the deployment area. The main idea behind the MF approach is to introduce non-randomness in the movement of nodes and exploit such non-randomness to help deliver data. We study two variations of MF, depending on whether ferries or nodes initiate proactive movement. The MF design exploits mobility to improve data delivery performance and reduce energy consumption in nodes. We evaluate the performance of MF via extensive ns simulations which confirm the MF approach is efficient in both data delivery and energy consumption under a variety of network conditions.
2637438
Modeling and regulation of host traffic in ATM networks
For any connection admission control (CAC) algorithm to work correctly and efficiently, accurate information of the traffic flow out of the host systems is required. We develop several approximation approaches for modeling the traffic flows of hard real-time connections. We show that without accurate traffic characterization, the CAC algorithm may do either of the following: (1) admit connections that may cause network congestions which results in violating connection deadline requirements; or (2) pessimistically reject many connections whose QoS can be guaranteed. We propose a traffic approximation model that can characterize the traffic correctly and efficiently, achieving a higher admission probability. From our experimental data we observe that the source traffic from a typical host is bursty. This burstiness may cause congestion within the network. To overcome this problem, we propose and analyze a simple traffic regulation mechanism at the application layer. The performance evaluation data shows that in the regulated system the traffic burstiness is lower and the probability of a connection being admitted is higher than the unregulated system.