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A SIMULATION-BASEd COMPARISON OF VOICE TRANSMISSION ON CSMA/Cd NETWORKS ANd ON TOKEN BUSES

AT&T BELL LABORATORIES TECHNICAL JOURNAL 1984年第1期63卷 33-55页

作者： dETREVILLE, Jd AT&T Bell Laboratories. John D. DeTreville: B.S. (Mathematics) 1970 University of South Carolina S.M. (Computer Science) 1972 Massachusetts Institute of Technology Ph.D. (Computer Science) 1978 Massachusetts Institute of Technology AT&T Bell Laboratories 1978—.

digitized speech can be transmitted over a variety of digital media. An interesting choice is the use of a Local-Area Network (LAN), for which digitized speech is packetized at the transmitter and depacketized at the receiver. Many local-area networks exhibit good throughput but poor delay characteristics; variable or excessive transmission delay can become noticeable and objectionable to the users of such a voice system. A number of simulations were performed to assess the delay characteristics of a Carrier Sense Multiple Access/Collision detection (CSMA/Cd) LAN and of a similar token bus LAN. A comparison of the results shows that the token bus performs somewhat better. The CSMA/Cd LAN's performance was characterized by carrying voice well until a point of collapse is reached; the token bus's performance degraded more continuously. In either case, throughput close to the theoretical capacity of the LAN was found achievable with appropriate techniques.

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OPTIMUM SCAN-WIdTH SELECTION UNdER CONTAINMENT CONSTRAINTS

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AT&T BELL LABORATORIES TECHNICAL JOURNAL 1984年第6期63卷 1191-1212页

作者： GAREY, MR PINTER, RY AT&T Bell Laboratories. Michael R. Garey: B.S. (Mathematics) 1967 M.S. (Computer Science) 1969 and Ph.D. (Computer Science) 1970 University of Wisconsin AT&T Bell Laboratories 1970—. Ron Y. Pinter: B.S. (Computer Science) 1975 Technion—Israel Institute of Technology S.M. and Ph.D. (Computer Science) The Massachusetts Institute of Technology 1980 and 1982 respectively AT&T Bell Laboratories 1982–1983 IBM Israel Scientific Center 1983—.

We consider the following algorithmic problem, which arises in connection with optimally choosing beam widths and positions for electron exposure of integrated circuit wafers. Let H > 0 be a fixed real number, and let c be a fixed, positive-valued, nondecreasing cost function defined on (0, H ]. An instance of the problem consists of a given range R = [ a, b ] and n given intervals I i = [ a i , b i ], 1 ≤ i ≤ n , each contained in R and of length not exceeding H . A solution (or feasible solution) for such an instance is a collection of segments, S 1 , S 2 , …, S k , each of length at most H and contained in R , such that each given interval is contained in at least one segment and the union of all the segments is R . The goal is to find an optimal solution with respect to c , i.e., a solution for which the sum of the costs of the individual segment lengths is as small as possible. The segments in a solution describe the beam positions and widths, projected on one side of the wafer, and the given intervals correspond to particularly sensitive regions on the layout mask, each of which must be entirely exposed by a single scan. The cost function gives the time required for a single scan of given width, including alignment overhead. Using dynamic programming techniques, we give efficient algorithms and data structures for solving this problem for several natural classes of cost functions, the most general of which is the class of all concave increasing functions, solved by an algorithm that runs in time O ( n 2 ).

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THEORY ANd PRACTICE IN THE CONSTRUCTION OF A WORKING SORT ROUTINE

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AT&T BELL LABORATORIES TECHNICAL JOURNAL 1984年第8期63卷 1827-1843页

作者： LINdERMAN, JP AT&T Bell Laboratories. John P. Linderman: S.B. (Mathematics) 1968 S.M. and Ph.D. (Computer Science) The Massachusetts Institute of Technology in 1970 and 1973 respectively AT&T Bell Laboratories 1973—.

Because comparison in the standard UNIX ™ operating system sort routine, /bin/sort, is interpretive, it is generally more time-consuming than the standard paradigm of comparing two integers. When a colleague and I modified sort to improve reliability and efficiency, we found that techniques that improved performance for other sorting applications sometimes degraded the performance of sort. Input and output are important when comparisons are simple, but as comparisons become more complex, the number of comparisons quickly dominates the performance of sort.

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PROGRAM TRANSFORMATIONS FOR dATA ACCESS IN A LOCAL dISTRIBUTEd ENVIRONMENT

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AT&T BELL LABORATORIES TECHNICAL JOURNAL 1984年第6期63卷 1019-1028页

作者： dETREVILLE, Jd SINCOSKIE, Wd AT&T Bell Laboratories. John D. DeTreville: B.S. (Mathematics) 1970 University of South Carolina S.M. (Computer Science) 1972 Massachusetts Institute of Technology Ph.D. (Computer Science) 1978 The Massachusetts Institute of Technology AT&T Bell Laboratories 1978—. AT&T Bell Laboratories present affiliation Bell Communications Research Inc. W. David Sincoskie: B.E.E. 1975 M.E.E. 1977 Ph.D. (Electrical Engineering) 1980 University of Delaware AT&T Bell Laboratories 1980–1983

This paper presents a set of program transformations that are useful in transforming certain sequential program schemas for use in a local distributed environment. The environment is considered to be a set of processors connected by a local area network with broadcast capability. Examples of transformed program schemas are given that implement shared data, maximization, and abstract queues in a distributed environment.

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BUILd - A SOFTWARE CONSTRUCTION TOOL

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AT&T BELL LABORATORIES TECHNICAL JOURNAL 1984年第6期63卷 1049-1059页

作者： ERICKSON, VB PELLEGRIN, JF AT&T Bell Laboratories. Verlyn B. Erickson: B.A. (Mathematics/Physics) 1968 Augustana College M.S. (Computer Science) 1970 University of Wisconsin Madison Mathematics Research Center University of Wisconsin 1969–1972 Engineering Computing Laboratory University of Wisconsin 1970–1977 AT&T Bell Laboratories 1977—. John F. Pellegrin: B.A. (Mathematics) 1965 Occidental College M.A. (Mathematics) 1967 Arizona State University AC Electronics Defense Research Laboratories Goleta CA 1967–69 Ph.D. (Mathematics) 1972 Arizona State University AT&T Bell Laboratories 1972—.

The build tool is used as a sophisticated method of generating and modifying software systems. Build is being used successfully by a number of UNIX ™ software-based projects at AT&T Bell Laboratories. Build is an extension to the make program that permits several software developers to independently make a collection of software while sharing the same fully populated set of directories, with the changed files residing in their own directories. An important concept in using build is software view , which represents the selection of a particular version of software for a generation environment. For example, a developer's view of a software system generally includes all of the current “official” software perturbed by the developer's private modifications to the system. A testing team's view may be the current official software perturbed by changes that a set of developers have made and have submitted for project system testing. A system user's view is a fully tested and released version of the software. The function of build is to simplify the administration of the different views of the software system. The build tool is being used by a number of large software development projects as the primary software generation tool. Build plays a central role in the development strategies and standards used in these projects.

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AN IMPROVEd WORd-dETECTION ALGORITHM FOR TELEphONE-QUALITY SPEECH INCORPORATING BOTH SYNTACTIC ANd SEMANTIC CONSTRAINTS

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AT&T BELL LABORATORIES TECHNICAL JOURNAL 1984年第3期63卷 479-498页

作者： WILPON, JG RABINER, LR MARTIN, T AT&T Bell Laboratories. Lawrence R. Rabiner: S.B. and S.M. 1964 Ph.D. 1967 (Electrical Engineering) The Massachusetts Institute of Technology AT&T Bell Laboratories 1962—. Jay G. Wilpon: B.S. A.B. (cum laude) in Mathematics and Economics respectively 1977 Lafayette College Easton PA M.S. 1982 (Electrical Engineering/Computer Science) Stevens Institute of Technology Hoboken NJ AT&T Bell Laboratories 1977—.

Accurate location of the endpoints of spoken words and phrases is important for reliable and robust speech recognition. The endpoint detection problem is fairly straightforward for high-level speech signals in low-level stationary noise environments (e.g., signal-to-noise ratios greater than 30-dB rms). However, this problem becomes considerably more difficult when either the speech signals are too low in level (relative to the background noise), or when the background noise becomes highly nonstationary. Such conditions are often encountered in the switched telephone network when the limitation on using local dialed-up lines is removed. In such cases the background noise is often highly variable in both level and spectral content because of transmission line characteristics, transients and tones from the line and/or from signal generators, etc. Conventional speech endpoint detectors have been shown to perform very poorly (on the order of 50-percent word detection) under these conditions. In this paper we present an improved word-detection algorithm, which can incorporate both vocabulary (syntactic) and task (semantic) information, leading to word-detection accuracies close to 100 percent for isolated digit detection over a wide range of telephone transmission conditions.

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ON THE APPLICATION OF EMBEddEd TRAINING TO CONNECTEd LETTER RECOGNITION FOR dIRECTORY LISTING RETRIEVAL

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AT&T BELL LABORATORIES TECHNICAL JOURNAL 1984年第3期63卷 459-477页

作者： RABINER, LR WILPON, JG TERRACE, SG AT&T Bell Laboratories. Lawrence R. Rabiner: S.B. and S.M. 1964 Ph.D. 1967 (Electrical Engineering) The Massachusetts Institute of Technology Bell Laboratories 1962—. Sandra G. Terrace: B.S. (summa cum laude in Mathematics) 1975 Northeastern University Boston Massachusetts. Ms. Terrace works primarily from her home in Chelmsford Massachusetts where she and her husband own and operate a computer software consulting firm. She is a computer software consultant to the Acoustics Research Department of AT&T Bell Laboratories at Murray Hill New Jersey. Jay G. Wilpon: B.S. and A.B. (cum laude) in Mathematics and Economics respectively 1977 Lafayette College Easton Pennsylvania M.S. (Electrical Engineering/Computer Science) 1982 Stevens Institute of Technology Hoboken N.J. AT&T Bell Laboratories 1977—.

Automatic speech recognition has advanced to the stage where it is now possible to recognize connected strings of words (e.g., digits, letters, city names, airline terms) from a word reference set of isolated tokens of each of the words in the vocabulary. Recently, an improved training technique called embedded word training was proposed, in which reference word patterns were extracted from within connected word sequences themselves. In this investigation we extend the embedded word training procedure to handle letters of the alphabet for use in a directory listing retrieval task. By performing connected letter recognition of spoken names based on letter classes (rather than specific letters themselves), we show how reliable name recognition results can be achieved using a fairly straightforward system on 200 randomly chosen names (chosen from an 18,210-name directory) spoken at a normal rate by four talkers (three male, one female) in a speaker-trained mode. We have found that an 8-percent improvement in name recognition accuracy is obtained when using embedded letter training patterns over that obtained from isolated letter patterns alone. The overall name recognition accuracy was close to 95 percent.

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ON THE RECOGNITION OF ISOLATEd dIGITS FROM A LARGE TELEphONE CUSTOMER POPULATION

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BELL SYSTEM TECHNICAL JOURNAL 1983年第7期62卷 1977-2000页

作者： WILPON, JG RABINER, LR Bell Laboratories. Jay G. Wilpon: B.S. A.B. (cum laude) in Mathematics and Economics respectively 1977 Lafayette College Easton Pa M.S. (Electrical Engineering/Computer Science) 1982 Stevens Institute of Technology Hoboken N.J. Bell Laboratories 1977—. Lawrence R. Rabiner: S.B. and S.M. 1964 Ph.D. 1967 (Electrical Engineering) The Massachusetts Institute of Technology Bell Laboratories 1962—.

A field study was initiated to learn about the effects of various telephone transmission and switching conditions on the algorithms currently used in the Bell Laboratories, Linear Predictive Coding (LPC)-based, isolated word recognizer. digit recordings were obtained from customers over a variety of transmission facilities. during a 23-day recording period a total of 11,035 isolated digits were recorded. For each recording, statistics were recorded about the line condition, the background environment, and the customer's ability to speak his/her telephone number as a sequence of isolated digits. Also recorded was information about the ability of the automatic word end-point detector to find each spoken digit and to accurately determine the correct endpoints. The results of several recognition tests are presented—one using a previously defined set of laboratory-created digit reference templates, and several others using new sets of reference templates from a subset of the recorded digits. The performance of the recognizer is poor (average digit accuracy of 77.4 percent) using the laboratory template set, but improves substantially (average digit accuracy of 93.1 percent) for a template set created from the field recordings. The reasons for this improvement in digit recognition accuracy are presented, along with their implications to future work in isolated word recognition.

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2 NEW KINdS OF BIASEd SEARCH-TREES

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BELL SYSTEM TECHNICAL JOURNAL 1983年第10期62卷 3139-3158页

作者： FEIGENBAUM, J TARJAN, RE Research done partly while a summer employee of Bell Laboratories and partly while a graduate student supported by Air Force grant AFOSR-80-042. Joan Feigenbaum: B.A. (Mathematics) 1981 Harvard University. Bell Laboratories. Robert E. Tarjan: B.S. (Mathematics) 1969 California Institute of Technology M.S. 1971 and Ph.D. 1972 (Computer Science) Stanford University Cornell University 1972-1973 University of California Berkeley 1973-1975 Stanford University 1975-1980 Bell Laboratories 1980—.

In this paper, we introduce two new kinds of biased search trees: biased, a, b trees and pseudo-weight-balanced trees. A biased search tree is a data structure for storing a sorted set in which the access time for an item depends on its estimated access frequency in such a way that the average access time is small. Bent, Sleator, and Tarjan were the first to describe classes of biased search trees that are easy to update; such trees have applications not only in efficient table storage but also in various network optimization algorithms. Our biased a, b trees generalize the biased 2, b trees of Bent, Sleator, and Tarjan. They provide a biased generalization of B -trees and are suitable for use in paged external memory, whereas previous kinds of biased trees are suitable for internal memory. Our pseudo-weight-balanced trees are a biased version of weight-balanced trees much simpler than Bent's version. Weight balance is the natural kind of balance to use in designing biased trees; pseudo-weight-balanced trees are especially easy to implement and analyze.

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AN EVALUATION OF ENERGY-CONSERVATION APPROACHES FOR SURFACE SHIPS

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NAVAL ENGINEERS JOURNAL 1980年第2期92卷 252-263页

作者： RAINS, dA STILES, HR HO, SPK Dr. Dean A. Rains Director of Advanced Programs and IRBD. Ingalls Shipbuilding Division Litton Industries Pascagoula Miss. has been an active member of ASNE since 1970. a frequent contributor to the Naval Engineers Journal and a participant at ASNE Day meetings as both an Author and a Discusser. He is an Associate Fellow of the American Institute of Aeronautics has twenty-three years experience in the field of Naval Engineering and is a graduate of the California Institute of Technology from which he received his B.S. degree (1950) and his M.S. degree (1952). both in Mechanical Engineering. and his Ph.D. degree (1954) in Mechanical Engineering and Mathematics. Mr. H. Richard Stiles graduated from the U.S. Naval Academy in 1965. Prior to leaving the naval service in 1970 he was designated as a Naval Aviator and authored two Patents one for an aircraft optical glide slope reference system and the second for an intercommunications system for air traffic control. As an author he has had technical papers published by SNAME — “Planning Hull Structure” — and by the Offshore Technology Conference — “A Fourth Generation Crewboat.” At the present time he serves as an Engineering Specialist for the Hull Technical Department at Ingalls Shipbuilding Division. Mr. Stephen P.K. Ho is also with Ingalls Shipbuilding Division where since 1970 he has worked on various phases of naval engineering and advanced studies. He received both his B.S. and M.S. degrees in Naval Architecture and Marine Engineering from the University of Michigan in 1958 and 1959 respectively. and prior to joining Ingalls Shipbuilding Division also worked with other Marine Firms in ship design particularly in computer applications to Preliminary Design the Construction Process and the Management Information System. Besides ASNE which he joined in January 1980. he is a member of SNAME.

Lower Fleet operating costs and independence from foreign fossil fuel resources are the goals of energy conservation efforts for Navy surface ship. This paper describes an evaluation of a wide variety of energy conservation approaches. A standard 20-knot, 300-hour destroyer mission is established so that all of the approaches can be compared on a total fuel required basis. The approaches studied include use of aluminum hull construction; light weight machinery; trail-shaft or cross-connect operation for twin screw ships; improved performance propulsors; advanced power plant types, such as COGAS or cruise engines; use of energy storage techniques to improve ship service generator performance; electrical load reductions; improved performance ship service generators; hull drag reductions; crew size reductions; design margin reduction; reduced performance requirement (such as top speed); and habitability standard reductions. The overall results can be effected by reductions in range requirements as well. Mission duration was held constant at 45 days throughout the study. The results of the study indicate that the combination of these various possible improvements may reduce the fuel used to be as low as one-third of the current levels. Weight reductions are very effective for achieving significant fuel savings.

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