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Automatic language identification using Gaussian mixture and hidden Markov models

April 27, 1993
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Conference Paper
Author:
Marc A. Zissman
Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, Vol. 2, Speech Processing, ICASSP, 27-30 April 1993, pp. 399-402.
Topic:
language recognition
R&D area:
R&D group:

Summary

Ergodic, continuous-observation, hidden Markov models (HMMs) were used to perform automatic language classification and detection of speech messages. State observation probability densities were modeled as tied Gaussian mixtures. The algorithm was evaluated on four multilanguage speech databases: a three language subset of the Spoken Language Library, a three language subset of a five language Rome Laboratory database, the 20 language CCITT database, and the ten language OGI telephone speech database. Generally, performance of a single state HMM (i.e. a static Gaussian mixture classifier) was comparable to the multistate HMMs, indicating that the sequential modeling capabilities of HMMs were not exploited.
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Summary

Ergodic, continuous-observation, hidden Markov models (HMMs) were used to perform automatic language classification and detection of speech messages. State observation probability densities were modeled as tied Gaussian mixtures. The algorithm was evaluated on four multilanguage speech databases: a three language subset of the Spoken Language Library, a three language subset...

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Automatic language identification using Gaussian mixture and hidden Markov models

Detection of transient signals using the energy operator

April 27, 1993
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Conference Paper
Author:
Robert B. Dunn
…
Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, Vol. 3, ICASSP, 27-30 April 1993, pp. 145-148.
Topic:
signal processing
R&D area:
R&D group:

Summary

A function of the Teager-Kaiser energy operator is introduced as a method for detecting transient signals in the presence of amplitude-modulated and frequency-modulated tonal interference. This function has excellent time resolution and is robust in the presence of white noise. The output of the detection function is also independent of the interference-to-transient ratio when that ratio is large. It is demonstrated that the detection function can be applied to interference signals with multiple amplitude-modulated and frequency-modulated tonal components.
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Summary

A function of the Teager-Kaiser energy operator is introduced as a method for detecting transient signals in the presence of amplitude-modulated and frequency-modulated tonal interference. This function has excellent time resolution and is robust in the presence of white noise. The output of the detection function is also independent of...

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Detection of transient signals using the energy operator

Time-scale modification of complex acoustic signals

April 27, 1993
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Conference Paper
Author:
Thomas F. Quatieri
…
Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, ICASSP, Vol. 1, Plenary, Special, Audio, Underwater Acoustics, VLSI, Neural Networks, 27-30 April 1993, pp. 213-216.
Topic:
speech enhancement
R&D area:
R&D group:

Summary

A new approach is introduced for time-scale modification of short-duration complex acoustic signals to improve their audibility. The technique constrains the modified signal to take on a specified spectral characteristic while imposing a time-scaled version of the original temporal envelope. Both full-band and sub-band representations of the temporal envelope are considered. In the full-band case, the modified signal is obtained by appropriate selection of its Fourier transform phase. In the sub-band case, using locations of maxima in the sub-band temporal envelopes, the phase of each bandpass signal is formed to preserve "events" in the envelope of the composite signal. The approach is applied to synthetic and actual short-duration acoustic signals consisting of closely-spaced and overlapping sequential time components.
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Summary

A new approach is introduced for time-scale modification of short-duration complex acoustic signals to improve their audibility. The technique constrains the modified signal to take on a specified spectral characteristic while imposing a time-scaled version of the original temporal envelope. Both full-band and sub-band representations of the temporal envelope are...

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Time-scale modification of complex acoustic signals

Automated gust front detection using knowledge-based signal processing

April 20, 1993
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Conference Paper
Author:
Richard L. Delanoy
…
Published in:
Proc. 1993 IEEE Natl. Radar Conf., 20-22 April 1993, pp. 150-155.
Topic:
artificial intelligence
R&D area:
R&D group:

Summary

For reasons of aviation safety and airport operations efficiency, gust front detection and tracking is an important product of Doppler weather radars developed for use in airport terminal areas. Previous gust front algorithms, which have relied on the detection of one or two conspicuous signatures in Doppler radar imagery, have worked reasonably well in images generated by the high-resolution, pencil-beam Terminal Doppler Weather Radar (TDWR). The latest Airport Surveillance Radar, enhanced with a Wind Shear Processor (ASR-9 WSP), is being developed as a less expensive alternative weather radar. Although gust fronts are visible to human observers in ASR-9 WSP imagery, the lower sensitivity and less reliable Doppler measurements of this radar make automated gust front detection a much more challenging problem. Using machine intelligence and knowledge-based signal processing techniques developed in the context of automatic target recognition, a Machine Intelligent Gust Front Algorithm (MIGFA) has been constructed that is radically different from the previous algorithms. Developed initially for use with ASR-9 WSP data, MIGFA substantially outperforms a state-of-the-art gust front detection algorithm based on earlier approaches. These results also indirectly suggest that MIGFA performance may be nearly as good as human performance. Preliminary results of an operational test period (two months, approximately 15000 scans processed) are presented.
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Summary

For reasons of aviation safety and airport operations efficiency, gust front detection and tracking is an important product of Doppler weather radars developed for use in airport terminal areas. Previous gust front algorithms, which have relied on the detection of one or two conspicuous signatures in Doppler radar imagery, have...

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Automated gust front detection using knowledge-based signal processing

Evaluation of the capacity and delay benefits of terminal air traffic control automation

April 14, 1993
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Project Report
Author:
Steven B. Boswell
Published in:
MIT Lincoln Laboratory Report ATC-192
Topic:
air traffic control
R&D area:
R&D group:

Summary

This report reviews the benefits that the CTAS component of the FAA Terminal Air Traffic Control Automation program (TATCA) offers to aviation users. In particular, the report evaluates the prospects that exist for increasing arrival capacity during Instrument Meteorological Conditions (IMC) by introducing CTAS functionality into current operations. The impact of anticipated capacity gains on air traffic delays is analyzed. Savings in delay are translated into dollar savings using FAA statistics on the fleet-weighted direct cost of delay to domestic air carriers. Also, the value of passenger time is considered. Economic impacts are estimated and reported on an annualized, nationwide basis. Adopting FAA projections of future traffic growth, estimates of delay and attendant cost savings to air carriers and their passengers are provided for fiscal years 1995-2015. Taking the nominal estimate of a 12% gain in IMC arrival capacity, a nationwide implementation of CTAS would be estimated to save an average of 412,000 hours of air carrier delay annually over this 21-year period, and 273 million gallons of fuel per year. With current fuel and labor costs, this amounts to average direct operating savings to air carriers of $1.5 billion per year, and value to passengers of over $3 billion per year, in constant 1988 dollars. There may be factors outside the scope of this study that restrict the implementation of CTAS to certain sites, or that limit the weather conditions in which CTAS is effective. Methods are discussed in the report for modifying benefits estimates in response to such considerations. However, since development and implementation costs of CTAS are estimated to be a small fraction of the benefits enumerated above, and since the delay savings recur annually, it is concluded that the development of STC automation software such as CTAS is economically justifiable.
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Summary

This report reviews the benefits that the CTAS component of the FAA Terminal Air Traffic Control Automation program (TATCA) offers to aviation users. In particular, the report evaluates the prospects that exist for increasing arrival capacity during Instrument Meteorological Conditions (IMC) by introducing CTAS functionality into current operations. The impact...

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Evaluation of the capacity and delay benefits of terminal air traffic control automation

ADS-Mode S: Initial System Description

April 2, 1993
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Project Report
Author:
Vincent A. Orlando
Published in:
MIT Lincoln Laboratory Report ATC-200
Topic:
mode S data links
R&D area:
R&D group:

Summary

Dependent Surveillance and the Mode S beacon radar. The result is an integrated concept for seamless surveillance and data link that permita equipped aircraft to participate in ADS or beacon ground environmenta. This offers many possibilities for transition from a beacon to an ADS based environment. The ADS-Mode S concept in baaed on use of the Mode S squitter. The Mode S squitter is a spontaneous, periodic (once per second) 56-bit Mode S broadcast containing the Mode S 24-bit address. This broadcast is provided by all Mode S transponders and in used by the Traffic Alert and Collision Avoidance System (TCAS) to acquire Mode S equipped aircraft. For ADS-Mode S use, this squitter broadcast is extended to 112 bits to provide for the transmission of a 56-bit ABS message field. The ADS squitter is transmitted in addition to the current TCAS squitter in order to maintain compatibility with current TCAS equipment. This paper defines the ADS-Mode S concept, describes its principal surveillance and data link applications and provides estimates of expected performance.
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Summary

Dependent Surveillance and the Mode S beacon radar. The result is an integrated concept for seamless surveillance and data link that permita equipped aircraft to participate in ADS or beacon ground environmenta. This offers many possibilities for transition from a beacon to an ADS based environment. The ADS-Mode S concept...

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ADS-Mode S: Initial System Description

Contributions to the American Meteorological Society's 26th International Conference on Radar Meteorology

April 1, 1993
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Project Report
Author:
Marilyn M. Wolfson
Published in:
MIT Lincoln Laboratory Report ATC-199
Topic:
weather
R&D area:
R&D group:

Summary

Eleven papers contributed by the Lincoln Laboratory Weather Sensing Group to the American Meteorological Society's 26th International Conference on Radar Meteorology, to be held May 24-28, 1993 in Norman, Oklahoma, are compiled in this volume. The work reported was sponsored by several FAA programs, including Terminal Doppler Weather Radar (TDWR), Air Surveillance Radar-9 (ASR-9), Integrated Terminal Weather System (ITWS), and Terminal Area Surveillance System (TASS). The papers are based on analyses completed over the past year at Lincoln Laboratory and in collaboration with staff at the National Severe Storms Laboratory, the University of Oklahoma, Raytheon Corporation, and the FAA Technical Center in Atlantic City, NJ. The staff members of the Weather Sensing Group have documented their studies in four major areas: Operational Systems (TDWR Operational Test and Evaluation results); Radar Operations (future airport weather surveillance requirements, a "machine intelligent" gust front detection algorithm, microburst asymmetry study results, a shear-based microburst detection algorithm, and a hazard index for TDWR-detected microbursts); Signal Processing (coherent processing across multi-PRI waveforms, clutter filter design for multiple-PRT signals, and identification of anomalous propagation associated with thunderstorm outflows); and Analysis Methods (multiple-single Doppler wind analysis using NEXRAD data, and an adjoint method wind retrieval scheme).
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Summary

Eleven papers contributed by the Lincoln Laboratory Weather Sensing Group to the American Meteorological Society's 26th International Conference on Radar Meteorology, to be held May 24-28, 1993 in Norman, Oklahoma, are compiled in this volume. The work reported was sponsored by several FAA programs, including Terminal Doppler Weather Radar (TDWR)...

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Contributions to the American Meteorological Society's 26th International Conference on Radar Meteorology

Two simulation studies of precision runway monitoring of independent approaches to closely spaced parallel runways

March 2, 1993
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Project Report
Author:
Ann-Marie Lind
Published in:
MIT Lincoln Laboratory Report ATC-190
Topic:
surveillance
R&D area:
R&D group:

Summary

This report documents the findings of two simulation studies of air traffic controller reaction to the Precision Runway Monitor (PRM). The PRM is a new system for monitoring independent approaches, to closely spaced parallel runways. It consists of a radar which has higher accuracy and a faster update interval than the current system. The PRM radar is accompanied by a high-resolution color display which provides automated visual and vocal warnings to alert controllers of impending and actual penetration of a 'No Transgression Zone' between parallel runways. The studies, were conducted in order to determine the effects of key variables on controller reaction time and to determine controller opinion on system acceptability. Study I examined the use of the PRM when the runway separation was both 3,400 ft and 4,300 ft. Study II examined the use of the PRM when the runway separation was 3,000 ft. Real-time simulated approach blunders were presented to controllers, and measurements of their reaction times were recorded and analyzed. Independent variables studied included sensor update interval, runway separation, deviation angle, deviation range, flight path condition, approach blunder type, and controller experience level. In addition, controller opinions of the PRM were surveyed. Findings regarding the effects of each of the variables are reported. Survey results of controller opinion are reported. Recommendations for enhancing the realism of the simulation and recommendations of issues for future study are discussed.
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Summary

This report documents the findings of two simulation studies of air traffic controller reaction to the Precision Runway Monitor (PRM). The PRM is a new system for monitoring independent approaches, to closely spaced parallel runways. It consists of a radar which has higher accuracy and a faster update interval than...

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Two simulation studies of precision runway monitoring of independent approaches to closely spaced parallel runways

Machine intelligent gust front detection

March 1, 1993
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Journal Article
Author:
Richard L. Delanoy
…
Published in:
Lincoln Laboratory Journal, Vol. 6, No. 1, Spring 1993, pp. 187-212.
Topic:
algorithms
R&D area:
R&D group:

Summary

Techniques of low-level machine intelligence, originally developed at Lincoln Laboratory to recognize military ground vehicles obscured by camouflage and foliage, are being used to detect gust fronts in Doppler weather radar imagery. This Machine Intelligent Gust Front Algorithm (MIGFA) is part of a suite of hazardous-weather-detection functions being developed under contract with the Federal Aviation Administration. Initially developed for use with the latest generation Airport Surveillance Radar equipped with a wind shear processor (ASR-9 WSP), MIGFA was deployed for operational testing in Orlando, Florida, during the summer of 1992. MIGFA has demonstrated levels of detection performance that have not only markedly exceeded the capabilities of existing gust front algorithms, but are competitive with human interpreters.
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Summary

Techniques of low-level machine intelligence, originally developed at Lincoln Laboratory to recognize military ground vehicles obscured by camouflage and foliage, are being used to detect gust fronts in Doppler weather radar imagery. This Machine Intelligent Gust Front Algorithm (MIGFA) is part of a suite of hazardous-weather-detection functions being developed under...

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Machine intelligent gust front detection

Receiver Autonomous Integrity Monitoring (RAIM) of GPS and GLONASS

March 1, 1993
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Journal Article
Author:
Pratap N. Misra
…
Published in:
Navig. J. Inst. Navig., Vol. 40, No. 1, Spring 1993, pp. 87-104.
Topic:
autonomous systems
R&D area:
R&D group:

Summary

A receiver autonomous integrity monitoring (RAIM) algorithm is proposed, and used to analyze the integrity monitoring capabilities of potential sole-means (or stand-alone) systems based on integrated use of GPS and GLONASS, GPS supplemented with a geostationary overlay, and enhanced GPS constellations. As in the other RAIM algorithms, the idea is to take advantage of the redundant measurements. Our focus, however, is on the quality of the position estimate, rather than on diagnosing whether the system is working as intended. The proposed approach uses the redundant measurements to generate a position estimate and a measure of its quality. The latter, called integrity level, is defined as an upper bound on the position error. The estimation of the integrity level is the main innovation in the proposed scheme. The RAIM algorithm is tailored to an abundant redundancy of the measurements, and addresses the following issue: Given a snapshot of the pseudo range measurements, one of which may be in error, can we compute a position estimate that can be shown with high confidence to meet the user's accuracy requirement?
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Summary

A receiver autonomous integrity monitoring (RAIM) algorithm is proposed, and used to analyze the integrity monitoring capabilities of potential sole-means (or stand-alone) systems based on integrated use of GPS and GLONASS, GPS supplemented with a geostationary overlay, and enhanced GPS constellations. As in the other RAIM algorithms, the idea is...

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Receiver Autonomous Integrity Monitoring (RAIM) of GPS and GLONASS
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