Duality relationships among “space”,“time”, and “wavelength” in all-optical networks

All-optical networks (AONs) are emerging as the next generation broadband networks for both wide-area and local-area networks. New optical devices such as wavelength routers, and wavelength division switches are currently being developed to realize these AONs. In this paper, we examine “dual” properties that exist among “space”, “time”, and “wavelength” in multiplexed signals in AONs. This observation will clarify relationships among architectural alternatives and suggest novel space-time-wavelength switching structures. It will also lead to a performance analysis of all-optical networks, by exploiting some well studied results obtained for classical circuit switched systems. A study on call blocking probabilities will be reported in a separate paper     

“Professional communication” and the “odor ofmendacity”: the persistent suspicion that skilful writing issuccessful lying

From the time that rhetoric first differentiated itself from philosophy there has been a widespread belief that the craft of rhetoric is, to a considerable extent, the art of deception with impunity. As early as Plato's Gorgias dialogue and as recently as a proposed rule from the Food and Drug Administration, one finds those who argue that even the skills of technical and scientific communication are, in effect, artful forms of misrepresentation. These critics indict not only those who sell and apologize-easy targets-but also those those avowed purpose is merely to make messages clearer. Can it be true that all forms of communication skill, even those that enhance clarity and precision, are merely elegant forms of lying? Does the word “rhetoric” deserve its tainted historical connotation? Or, even worse, is writing itself an inherently self-serving (i.e. misleading) way of adapting to one's environment?     

News: new perils in hosted data?

One of the newest beta features in the Google Desktop is exposing both theoretical and practical issues about storing data at remote, hosted sites. Search Across Computers, new in Google Desktop 3, lets registered users search the documents on any of their computers via indexed copies stored temporarily on Google servers. The new feature represents only one of many online service innovations that current network capabilities encourage - and current laws allow. Legal scholars have joined technologists to resolve the potential data-exposure risks without stifling the development of new and useful online services.     

Indexes are “out”, models are “in”

What would it take to build a search engine possessing the knowledge, intelligence, and resourcefulness of my favorite research librarian? Her ability to interpret my inquiries, knowledgeably expand them, and then extrapolate them into a rich model for search and retrieval makes her an invaluable and pleasurable resource. She takes pride in knowing her library thoroughly, both spatially (where to physically find a book) and temporally (how her book inventory has changed and evolved). As she formulates her plan of attack, her sophisticated understanding of language, culture, experience, and other knowledge domain models simultaneously converge and are re-mapped onto the reality of her library. The task of information retrieval becomes an interactive adventure of human dimensions, full of the satisfaction of continuous discovery. Keyword matching is a crude and unsatisfying method for sampling the information content of complex sources such as the World Wide Web. These truncated representations fail to model the larger meaning embedded within the source-they leave behind all vital contextual information, and they strip away any basis for appraising the quality and veracity of the source. The worthless appears as the equal of the worthy. In the electronic future, when all books are digitized and available on line, I pray that we have a more skilled and interesting guide than Yahoo or WebCrawler staffing the circulation desk     

Tailored spreading symbols in “Strobe Correlators” using “W2-pulses”

A “Strobe Correlator” is a correlation-based multipath mitigation technique that utilizes tailored reference waveform to shape the discriminator function for tracking Global Navigation Satellite System (e.g. Global Positioning System) signals. Multipath performance of these techniques for Binary Phase Shift Keying (BPSK) signals has been discussed for decades but for some, their noise performance may not be easily evaluated analytically. In this paper, a theoretical framework is provided for noise evaluation of “Strobe Correlators” using complex strobes for both BPSK and sine-phased Binary Offset Carrier (e.g. BOC(1,1)) signals. Mathematical expressions of the tailored spreading symbols as key factors are derived and used for theoretical code tracking variance analysis of various correlation techniques including the “Gating Function” using a complex strobe-pulse liked waveform (i.e. “W2-pulses”). Empirical results for the sine-phased BOC(1,1) signal are given as verification. Analytical results reveal that the techniques using a W2-pulse suffer from higher code tracking variance than others, due to increased sensitivity to noise. The sensitivity to pre-correlation bandwidth is found to relate to the relative placement of the strobe pulses.     

Comment on: “Component relevancy in multistate reliabilitymodels”

The author comments on the paper by A.M. Abouammoh and M.A. Al-Kadi (see ibid., vol.40, p.370-4, 1991) which discusses various notions of component relevancy for multistate systems and suggests a unified form of relevancy. The paper contains many misprints, some wrong examples, and several results that need clarification. The most important are mentioned     

Changeover Improvement: Reinterpreting Shingo's “SMED” Methodology

A rapid changeover capability is widely acknowledged as an essential prerequisite to flexible, responsive small batch manufacturing. Its importance in mass customization is recognized, where minimal losses need to be incurred as manufacture switches between differing products. Retrospective improvement of existing changeover practice is often undertaken, arising from pressure to respond better to customer demands, wherein improvement personnel frequently engage Shigeo Shingo's Single Minute Exchange of Die (SMED) methodology to achieve better performance. Irrespective of the improvement methodology that is employed this paper assesses two fundamental mechanisms by which better changeovers might be achieved. First, improvement can occur by altering when tasks are conducted. Better allocation of tasks to the resources necessary to conduct them is sought, where the tasks themselves remain essentially unchanged. The second mechanism is to seek structural change to existing tasks, thereby intrinsically enabling them to be completed more quickly. These two mechanisms are described in relation to use of the SMED methodology, where it is argued that, by reinterpreting Shingo's work, greater clarity of potential improvement options can be gained     

Holographic optical switching: the “ROSES” demonstrator

The design, assembly, and performance of a prototype 1×8 free-space switch demonstrator using reconfigurable holograms are reported. Central to the switch fabric is a ferroelectric liquid crystal (FLC) on silicon spatial light modulator (SLM) deposited with a 540×1 array of highly reflective and planar mirror strips. The input and output ports of the switch are fabricated as a linear array of silica planar waveguides connected to single-mode fibers, and the holographic beam-steerer operates without the need for adjustment or dynamic alignment. The waveguide array and the single Fourier transform lens for the 2f holographic replay system are housed in an opto-mechanical mount to provide stability. The switch operates at 1.55 μm wavelength and has a designed optical bandwidth of >60 nm. The first measured insertion loss and crosstalk figures are 16.9 dB and -19.1 dB, respectively. Improvements in SLM performance, the use of new addressing schemes and the introduction of better alignment techniques are expected to improve these figures considerably. The preliminary performance of a 3×3 optical crossconnect is also presented to show that this technology is scalable to N×N switching fabrics     

Technology diversification in “MUL-TECH” corporations

This paper explores the nature of technology diversification at the product and corporate levels and shows its strong impact upon growth of R&D expenditures and growth of corporate sales. The emergence of “mul-tech” corporations, that is, corporations operating in many technologies, is demonstrated and the hypothesis that technology diversification creates a potential for growth is tested. However, in order to realize mul-tech-based growth it is of vital importance to gear technology management toward reaping both economies of scale and of scope through, among other things, communication and coordination, external technology sourcing and internal technology transfer, and cross-fertilization     

The “packing” and the “scheduling packet”switch architectures for almost all-optical lossless networks

This paper proposes two almost all-optical packet switch architectures, called the “packing switch” and the “scheduling switch” architecture, which when combined with appropriate wait-for-reservation or tell-and-go connection and how control protocols provide lossless communication for traffic that satisfies certain smoothness properties. Both switch architectures preserve the order of packets that use a given input-output pair, and are consistent with virtual circuit switching, The scheduling switch requires 2klogT+k² two-state elementary switches (or 2klogT+2klogk elementary switches, if a different version is used) where k is the number of inputs and T is a parameter that measures the allowed burstiness of the traffic. The packing switch requires very little processing of the packet header, and uses k²logT+klogk two-state switches. We also examine the suitability of the proposed architectures for the design of circuit switched networks. We find that the scheduling switch combines low hardware cost with little processing requirements at the nodes, and is an attractive architecture for both packet-switched and circuit-switched high-speed networks     

Joint Optimization Of “Transmission Rate” and “Outer-Loop SNR Target” Adaptation Over Fading Channels

Joint optimization of signal-to-noise ratio (SNR) target and transmission rate adaptation is examined for multilevel quadrature amplitude modulation (MQAM) over flat-fading channels, to maximize the spectral efficiency subject to an average transmit power constraint. We propose an adaptive transmission scheme in which the outer-loop SNR target and data rate are adapted to bit-error rate (BER), where total or truncated channel-inversion strategies are exploited for the (fast) inner-loop power control. We obtain the optimal solutions for both continuous and discrete rate adaptation, and consider cases where diversity combining is performed in the receiver. We show that by using this BER-based adaptive scheme, spectral efficiency can be improved compared with optimal SNR-based variable-rate variable-power MQAM. We also show that for continuous rate adaptation, the optimal SNR target monotonically increases with BER, while it descends within a BER range with constant rate     

Affine order-statistic filters: “medianization” oflinear FIR filters

This paper introduces a novel, data-adaptive filtering framework: affine order-statistic filters. Affine order-statistic filters operate effectively on a wide range of signal statistics, are sensitive to the dispersion of the observed data, and are therefore particularly useful in the processing of nonstationary signals. These properties result from the introduction of a tunable affinity function that measures the affinity, or closeness, of observation samples in their natural order to their corresponding order statistics. The obtained affinity measures are utilized to control the influence of individual samples in the filtering process. Depending on the spread of the affinity function, which is controlled by a single parameter γ, affine order-statistic filters operate effectively in various environments ranging from Gaussian to impulsive. The class of affine order-statistic filters subsumes the family of weighted order-statistic (WOS) affine filters and the class of FIR affine filters. We focus on a representative of the WOS affine filter class-the median affine filter-whose behavior can be tuned from that of a linear FIR filter to that of a robust median filter by narrowing the affinity function to a process referred to as medianization. The superior performance of affine order-statistic filters is demonstrated in two applications     

Teaching “Introduction to electrical and computerengineering” in context

In this paper we present an approach to teaching an introductory course in electrical and computer engineering to freshmen engineering students. The primary distinguishing characteristics of our approach include: providing information in an experiential context or “teaching-in-context”; focusing on “black-box”-based hierarchical decomposition as an approach to understanding complex systems; and using piecewise linear models for nonlinear elements as a way to develop intuition and understanding about the workings of circuits. The experiential context is provided by having students carry out a series of laboratory exercises involving an exciting real-world electronic system. To date, we have developed laboratory exercises around a programmable robot and a Global Positioning System receiver. The greatest challenges in teaching an intellectually substantive course to entering freshmen are their lack, on average, of the mathematics and physics background that is taken for granted in most electrical and computer engineering courses. In this paper we demonstrate that by appropriate choice of material and presentation methods this challenge can be overcome     

Commentaries on “Active networking and end-to-endarguments”

This article is a collection of short commentaries by recognized networking experts offering their perspectives on the relation between active networks and “end-to-end arguments”. The first commentary, by Bhattacharjee, Calvert, and Zegura, frames the question and makes a case arguing that active networking does not conflict with end-to-end argument principles. These authors are leading a research group at Georgia Institute of Technology working on the CANEs (composable active network elements) project, which focuses on service composition and applications for active networking. They also participate in the DARPA active network community's efforts to define network/node and service composition architectures. The second commentary, by Partridge, Strayer, Schwartz, and Jackson, claims that end-to-end arguments discourage active networking in the Internet layer, but encourage active networking at all other layers except perhaps the transport layer. The BBN Technologies (part of GTE Corp.) team has completed a DARPA project called Smart Packets, where concisely encoded active packets are used for network management and diagnostics in IP. Reed, Saltzer, and Clark reexamine their original end-to-end arguments specifically within the context of active networks     

Internet and the “plodding” standard bodies

The role of the ITU in the development of standards for the Internet is discussed. The speed with which standards are addressed and the relevant procedures in their development are considered     

Professional communication and Poe's “The PurloinedLetter”

At first glance, there seems to be very little in common between professional communication and a nineteenth-century detective story. However, there is a strong link between Poe's “The Purloined Letter” (E.A. Poe, 1975) and the successful practices of today's professional communicators, particularly technical writers and editors. In the story, Poe's writing methodology and his main character's investigative advice both offer useful guidelines for successful professional communication. “The Purloined Letter” is a formulaic detective story about Dupin, a witty detective who solves the case of a stolen letter, a case previously unsolved by the French police. Dupin uses intimate knowledge of human logic and reasoning to find the stolen letter. His method is contrasted with that of the French police who had spent months unsuccessfully searching for it. Dupin's means of finding the letter is a series of significant courses of action that can be applied to effective professional communication strategies. The article summarizes Dupin's advice and how it can be applied to effective technical communication today     

“Dead-band” PWM switching patterns

Reference/modulating waveform continuity is not a necessary condition for the implementation of switching patterns for three-phase pulse-width modulated (PWM) converters if the load or the source are Y-connected. This is based on the fact that the converter phase-voltages do not need to be sinusoidal and switching pattern discontinuities-“dead-bands”-do not degrade the quality of output/input voltage/current waveforms by introducing low-order harmonics if certain parameters are optimized. This paper discusses general characteristics of various discontinuous switching patterns for PWM converters and shows that they can yield better performance than their continuous counterparts in some operating regions. Performance is defined as harmonic distortion normalized with respect to effective switching frequency and serves as a measure of comparison with continuous PWM techniques, The applications considered include general purpose and application specific solid-state power supplies using voltage source inverters and PWM rectifiers. Theoretical considerations are verified on an experimental unit     

“Biped”: a dance with virtual and company dancers. 1

Merce Cunningham's “Biped” is a new and unique modern dance. The choreography integrates computer-captured virtual dance movement so directly and naturally as to root the entire piece in today's time and space. The animations derive from a complex process, beginning with computerized motion-capture sessions. “Biped” reveals an openness and curiosity applied to computer technology that makes us anticipate new possibilities rather than honor the past. This is a dance conceived entirely for performance as much within a computer as on stage, yet executed without sacrificing any of the human emotion and movement that makes dance survive as a fine-art form     

SAR interferometry: a “Quick and dirty” coherenceestimator for data browsing

Usual coherence estimation in SAR interferometry is a time consuming task since an accurate estimation of the local frequency of the interferometric fringes is required. This paper presents a fast algorithm for generating coherence maps, mainly intended for data browsing. The proposed estimator is based on the speckle similarity of coherent SAR data, and is thus independent of fringe frequency. The following advantages, with respect to the usual estimates, are achieved: (a) The estimator is more than 100 times faster, achieved at the cost of a reduced statistical confidence. (b) The estimator is not affected by possible local frequency estimation errors. (c) The estimator can be directly applied to single look detected images. The theoretical derivation of the statistical properties of the frequency independent estimator is carried out in the stationary case. The nonstationary case is then analyzed on real ERS SAR images