Generalized Concentration Equipment Location Problem

Deregulation of the US telecommunication market and the break-up of the Bell System in the 1980s, followed by the privatizing and deregulating of most economically advanced countries of Europe and the Asia-Pacific region, ushered in an era of market turbulence, technological uncertainty and regulatory confusion in the information technology sector [Dholakia and Dholakia 1994]. This transformation from a regulated to a deregulated industry was the impetus for the marked drop in long-distance rates and the ensuing rapid upsurge in usage, particularly in data communication. In response to competition, common carriers have greatly increased the number of services available. For example, since divestiture, AT&T responded with hundreds of new interstate services and features; indeed, the number of new AT&T pricing plans and services rose from 35 in 1984 to 195 in 1991 [Garfinkel 1993]. Competition of this magnitude makes it possible for businesses to economically create vast private telecommunication networks. As society demands larger and more complex data communication networks, particularly to support such applications as end-user computing, multimedia, and electronic data interchange (EDI), designing cost effective networks and subsequently managing them becomes increasingly more difficult and consequential. One noteworthy topological issue in the design of data communication networks is how to connect large numbers of remote terminals to a central site. Historically, the usual design method utilized strictly concentrators [Mirzaian 1985]. However, with the advent of microelectronics, there is a host of data concentration equipment available that facilitate the economic utilization of transmission media. Despite many sophisticated alternatives supported by advanced technology, transmission will always constitute the most expensive component of telecommunication systems, requiring careful management to achieve the highest possible economy [Puzman and Kubin 1992]. This research addresses a network design problem referred to as the generalized concentrator equipment location problem (GCELP). GCELP may be defined as the problem of determining where to establish sites consisting of one or more concentrators, each of which are connected to a central site (e.g., a node of a backbone network or a processing site), and connecting terminals, often remote, to these concentrators. For completeness sake, variable concentrator coverage is considered. That is, each terminal will be connected to some concentrator for its primary coverage, possibly to another concentrator for its secondary coverage, and so forth [Pirkul et al.1988, Narasimhan 1990]. In the next section, a mathematical formulation of GCELP is provide

Hierarchical location-allocation models for congested systems

In this paper we address the issue of locating hierarchical facilities in the presence of congestion. Two hierarchical models are presented, where lower level servers attend requests first, and then, some of the served customers are referred to higher level servers. In the first model, the objective is to find the minimum number of servers and their locations that will cover a given region with a distance or time standard. The second model is cast as a Maximal Covering Location formulation. A heuristic procedure is then presented together with computational experience. Finally, some extensions of these models that address other types of spatial configurations are offered.Hierarchical location, congestion, queueing

Visible light communications-based indoor positioning via compressed sensing

This paper presents an approach for visible light communication-based indoor positioning using compressed sensing. We consider a large number of light emitting diodes (LEDs) simultaneously transmitting their positional information and a user device equipped with a photo-diode. By casting the LED signal separation problem into an equivalent compressed sensing framework, the user device is able to detect the set of nearby LEDs using sparse signal recovery algorithms. From this set, and using proximity method, position estimation is proposed based on the concept that if signal separation is possible, then overlapping light beam regions lead to decrease in positioning error due to increase in the number of reference points. The proposed method is evaluated in a LED-illuminated large-scale indoor open-plan office space scenario. The positioning accuracy is compared against the positioning error lower bound of the proximity method, for various system parameters.Comment: to appear in IEEE Communication Letter

Hydrogen detection study

The effectiveness was assessed of a hydrogen (H2) detection concept for regenerative environmental control life support systems (EC/LSS). The concept evaluated was that utilized for the electrochemical depolarized concentrator (EDC) design, constructed, and tested for the EC/LSS space station prototype program. The EDC contains combustible gas detectors (CGDs) which were evaluated with H2. The CGDs were evaluated for linearity, position sensitivity, reproducibility, ambient effects, repeatability, speed of response, recovery time, and interchangeability. The effectiveness of CGDs located within the EDC for sensing H2 leaks at various line replaceable units in the subsystem was determined. The effects of H2 leak rate, H2 concentration of leaking gas and air currents in the vicinity of the EDC were determined. Proposed improvements for the H2 detection concept were documented and alternative H2 detection approaches were identified and analyzed

SymbioCity: Smart Cities for Smarter Networks

The "Smart City" (SC) concept revolves around the idea of embodying cutting-edge ICT solutions in the very fabric of future cities, in order to offer new and better services to citizens while lowering the city management costs, both in monetary, social, and environmental terms. In this framework, communication technologies are perceived as subservient to the SC services, providing the means to collect and process the data needed to make the services function. In this paper, we propose a new vision in which technology and SC services are designed to take advantage of each other in a symbiotic manner. According to this new paradigm, which we call "SymbioCity", SC services can indeed be exploited to improve the performance of the same communication systems that provide them with data. Suggestive examples of this symbiotic ecosystem are discussed in the paper. The dissertation is then substantiated in a proof-of-concept case study, where we show how the traffic monitoring service provided by the London Smart City initiative can be used to predict the density of users in a certain zone and optimize the cellular service in that area.Comment: 14 pages, submitted for publication to ETT Transactions on Emerging Telecommunications Technologie

An Exact Algorithm for the Capacitated Vertex p-Center Problem

Cataloged from PDF version of article.We develop a simple and practical exact algorithm for the problem of locating p facilities and assigning clients to them within capacity restrictions in order to minimize the maximum distance between a client and the facility to which it is assigned (capacitated p-center). The algorithm iteratively sets a maximum distance value within which it tries to assign all clients, and thus solves bin-packing or capacitated concentrator location subproblems using off-the-shelf optimization software. Computational experiments yield promising results. 2004 Elsevier Ltd. All rights reserved

Development of an improved mirror facet for space applications

A fabrication technique was successfully developed for a metallic aluminum honeycomb, high-accuracy, lightweight, and long-life solar concentrator (mirror) for Advanced Solar Dynamic Space Power Systems. The program scope was limited to the development, fabrication, evaluation, and delivery of a solar concentrator facet (petal) that was sized for a 2-meter deployable solar concentrator. A surface accuracy of 1.0 mrad was achieved. The development incorporated tooling design, material selection, facet forming, adhesive selection, testing, and analysis. Techniques for applying levelizing, reflective, and protective optical coatings were also developed