Publications

The wind in the airspace around an airport impacts both airport safety and operational efficiency. Knowledge of the wind helps controllers and automation systems merge streams of traffic; it is also important for the prediction of storm growth and decay, burn-off of fog and lifting of low ceilings, and wake...

The Traffic Alert and Collision Avoidance System (TCAS II) is now operating in all commercial airline aircraft to reduce the risk of midair collisions. TCAS II determines the relative positions of nearby aircraft, called intruders, by interrogating their transponders and receiving their replies. An intruder deemed a potential threat will...

A GPS antenna multipath rejection performance evaluation was conducted at Lincoln Laboratory. Ground reference station antennas and aviation patches were tested for their ability to reject a muitipath signal. Different types of ground plane structures were used such as choke rings, ground planes, and mock sections of fuselage. Frequencies transmitted...

A CW-coherent laser radar using a 20-Watt CO2 laser has been constructed and deployed for the measurement of wake-vortext turbulence. This is part of a larger effort to understand the motion and decay of wake vortices as a function of the local atmospheric conditions. The construction and operation of the...

This paper compares the word error rate of a speech recognizer using several signal processing front ends based on auditory properties. Front ends were compared with a control mel filter banks (MFB) based cepstral front end in clean speech and with speech degraded by noise and spectral variability, using the...

A technique to compensate for differences in phased array element patterns is presented. Each measured element pattern is approximated by a virtual array whose excitation function is determined by the Woodward-Lawson synthesis technique. By extending the virtual array beyond the physical array dimensions, mutual coupling and edge diffraction effects can...

The Federal Aviation Administration is developing a set of software tools, known as the Center-TRACON Automation System (CTAS) to assist air traffic controllers in their management and control tasks. CTAS originated at National Aeronautics and Space Administration (NASA) Ames Research Center, where prototypes continue to evolve. In parallel, Massachusetts Institute...

The performance of systems for speaker identification (SID) can be quite good with clean speech, though much lower with degraded speech. Thus it is useful to search for new features for SID, particularly features that are robust over a degraded channel. This paper investigates features that are based on amplitude...

A language identification technique using multiple single-language phoneme recognizers followed by n-gram language models yielded to performance at the March 1994 NIST language identification evaluation. Since the NIST evaluation, work has been aimed at further improving performance by using the acoustic likelihoods emitted from gender-dependent phoneme recognizers to weight the...

The two largest factors affecting automatic speaker identification performance are the size of the population an the degradations introduced by noisy communication, channels (e.g., telephone transmission). To examine experimentally these two factors, this paper presents text-independent speaker identification results for varying speaker population sizes up to 630 speakers for both...