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TCAS I design guidelines

September 24, 1982
  |
Project Report
Author:
William H. Harman III
…
Published in:
MIT Lincoln Laboratory Report ATC-114
Topic:
collision avoidance
R&D area:
R&D group:

Summary

A description of the FAA airborne Traffic Alert and Collision Avoidance System known as TCAS I introduces the main topic of the report: results of an investigation of simple techniques suitable for the passive and active detection of nearby aircraft by TCAS I. This is followed by a review of the measurement facilities and data used to evaluate the detection techniques. Techniques for identifying passively detected returns from potentially threatening aircraft, i.e., the rejection or "filtering out" of non-threat aircraft, are described and evaluated. Alternatives for time-sharing the 1090 MHz channel between the TCAS I transponder and the passive detector are described. A candidate passive detector is defined and its performance is evaluated using flight test data. Predictions of the performance of a low-power TCAS I based on active detection are made via link calculations and flight test measurements. A summary of results concludes the report.
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Summary

A description of the FAA airborne Traffic Alert and Collision Avoidance System known as TCAS I introduces the main topic of the report: results of an investigation of simple techniques suitable for the passive and active detection of nearby aircraft by TCAS I. This is followed by a review of...

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TCAS I design guidelines

Active BCAS: design and validation of the surveillance subsystem

December 17, 1980
  |
Project Report
Author:
William H. Harman III
…
Published in:
MIT Lincoln Laboratory Report ATC-103
Topic:
collision avoidance
R&D area:
R&D group:

Summary

Lincoln Laboratory, under FAA sponsorship, is developing an Active Beacon Collision Avoidance System (BCAS), concentrating primarily on the air-to-air surveillance subsystem. The surveillance functions required are to detect the presence of nearby aircraft (whether they are equipped with ATCRBS transponders or DABS transponders), and then generate a surveillance track on each aircraft, issuing range and altitude reports once per second. The development effort consisted of airborne measurements complemented by simulation studies and analyses. The basic effects of ground-bounce multipath, interference, and power fading were assessed by air-to-air measurements. In other measurements, the BCAS interrogation and reply signal formats were transmitted between aircraft, and the results recorded for later playback and computer processing using the BCAS surveillance algorithms. This is a flexible means of experimentation which allows many of the design parameters to be changed as the effects are noted. In the most recent phase of the program, Lincoln designed and built realtime BCAS Experimental Units (BE Us), flight tested them, and then delivered them to the FAA for more extensive flight testing. In one of these flight tests, a BEU-equipped Boeing 727 flew to New York, Atlanta, and other major terminal areas in the eastern U.S. An analysis of BEU performance during this "Eastern Tour" is given in this report.
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Summary

Lincoln Laboratory, under FAA sponsorship, is developing an Active Beacon Collision Avoidance System (BCAS), concentrating primarily on the air-to-air surveillance subsystem. The surveillance functions required are to detect the presence of nearby aircraft (whether they are equipped with ATCRBS transponders or DABS transponders), and then generate a surveillance track on...

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Active BCAS: design and validation of the surveillance subsystem

Air traffic density and distribution measurements

May 3, 1979
  |
Project Report
Author:
William H. Harman III
Published in:
MIT Lincoln Laboratory Report ATC-80
Topic:
air traffic control
R&D area:
R&D group:

Summary

Results of measurements to determine peak air traffic densities, the spatial distribution of air traffic, and its variation with time, in the Los Angeles Basin and at several locations from Boston to Washington, D.C. are reported. These measurements include only ATCRBS-transponder equipped aircraft. LA Basin traffic densities are shown to be significantly higher than those measured at any other location. The time- and spatial-average density over a circular region of 10 nmi radius reaches a peak value of 0.1 aircraft per sq. nmi in LA. Under comparable conditions the density in Washington, Philadelphia, and Boston reaches 0.02 to 0.04 aircraft per sq. nmi. These measurements, made in 1976, were compared with the LA Basin Standard Traffic Model as to spatial distribution of traffic and absolute density. The results show that the model and the measurement differ by a scale factor of 5:1 (with density being greater in the model) but otherwise agree closely in spatial distribution.
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Summary

Results of measurements to determine peak air traffic densities, the spatial distribution of air traffic, and its variation with time, in the Los Angeles Basin and at several locations from Boston to Washington, D.C. are reported. These measurements include only ATCRBS-transponder equipped aircraft. LA Basin traffic densities are shown to...

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Air traffic density and distribution measurements

Airborne measurements of ATCRBS fruit

October 3, 1978
  |
Project Report
Author:
William H. Harman III
Published in:
MIT Lincoln Laboratory Report ATC-84
Topic:
surveillance
R&D area:
R&D group:

Summary

Airborne measurements of ATCRBS fruit (asynchronous replies from ATCRBS transponders) are described. These measurements were undertaken to provide a more firm basis for assessing the interference impact of ATCRBS fruit on airborne 1090 MHz receivers (as in BCAS). Fruit rate measurements were performed with an instrumented aircraft flying along the East Coast from Boston to Washington and in the Los Angeles Basin. The results of these measurements are reported here, with fruit rates given as a function of altitude, geographical location, and receiver threshold, for receptions on both top-mounted and bottom-mounted aircraft antenna. The highest observed fruit rates, approximately 10,000 replies/sec, occurred in the LA Basin. To complement the measurements, a first-order fruit prediction model is defined. Predictions of this model are compared with the measurements, generally showing favorable agreement in absolute fruit rate, in power distribution, and in the functional dependence on traffic density.
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Summary

Airborne measurements of ATCRBS fruit (asynchronous replies from ATCRBS transponders) are described. These measurements were undertaken to provide a more firm basis for assessing the interference impact of ATCRBS fruit on airborne 1090 MHz receivers (as in BCAS). Fruit rate measurements were performed with an instrumented aircraft flying along the...

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Airborne measurements of ATCRBS fruit

Effects of RF power deviations on BCAS link reliability

June 7, 1977
  |
Project Report
Author:
William H. Harman III
Published in:
MIT Lincoln Laboratory Report ATC-76
Topic:
surveillance
R&D area:
R&D group:

Summary

In the design of BCAS there is some freedom in the choice of specifications for BCAS transmitter power and receiver MTL (Minimum Triggering Level). Transmitter power should be high enough to provide adequate link reliability while being low enough to prevent interference problems. The question of providing adequate link reliability for the DABS mode of BCAS is addressed in this study. The study makes use of aircraft antenna gain data resulting from a model measurement program, and is otherwise analytical. It is concluded that appropriate nominal design values are transmitter power = 500 watts and receiver MTL = -77 dBm (referred to the BCAS unit). It is shown that these values provide sufficient power margin, at the air-to-air ranges appropriate for BCAS, so as to allow for adverse power deviations that might result from aircraft antenna gains, antenna cabling, and the expected transmitter and receiver deviations due to manufacturing nonuniformities and aging.
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Summary

In the design of BCAS there is some freedom in the choice of specifications for BCAS transmitter power and receiver MTL (Minimum Triggering Level). Transmitter power should be high enough to provide adequate link reliability while being low enough to prevent interference problems. The question of providing adequate link reliability...

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Effects of RF power deviations on BCAS link reliability

Discrete address beacon system (DABS) test plan for FY 1976

November 14, 1975
  |
Project Report
Author:
William H. Harman III
…
Published in:
MIT Lincoln Laboratory Report ATC-56
Topic:
surveillance
R&D area:
R&D group:

Summary

The major objectives of the continued DABS testing by Lincoln Laboratory are: (1) design validation and refinement, (2) performance assessment, and (3) the development of a data base of environmental characteristics. This document describes that portion of the test activities that will take place during FY 1976. Also included is a description of the special test facilities and teclmiques needed to collect and analyze the required data.
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Summary

The major objectives of the continued DABS testing by Lincoln Laboratory are: (1) design validation and refinement, (2) performance assessment, and (3) the development of a data base of environmental characteristics. This document describes that portion of the test activities that will take place during FY 1976. Also included is...

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Discrete address beacon system (DABS) test plan for FY 1976

Effects of ATCRBS P2 pulses on DABS reliability

January 28, 1974
  |
Project Report
Author:
William H. Harman III
…
Published in:
MIT Lincoln Laboratory Report ATC-20
Topic:
surveillance
R&D area:

Summary

An analytical study is performed to determine the effects of ATCRBS P2 pulses as interference to DABS uplink transmissions. These effects constitute a major component of all uplink error-producing mechanisms that are anticipated to occur in DABS operation. The study is fomulated in a way that includes effects of both receiver noise and P2 pulse interference, where the interference can be received from any of a number of different transmitters at different distances from the receiving aircraft. The model includes the randomness associated with whether or not a particular DABS signal is overlapped by any interference pulse, and also the conditional randomness of error production given that an overlap does occur. In fact, a major portion of the study is the determination of the conditional error probability given the occurrence of an overlap with stated signal-to-interference ratio and stated signal-to-noise ratio. The results are given as the probability of a "miss," where a "miss" is the event that at least one of the bits in the DABS data block is demodulated in error. The study is carried out for both DPSK and PAM which are the two modulation options being considered in the DABS design. Results are given both as general formulas and as evaluations of these fomulas in various specific cases. In these evaluations, the interference environment is based on ATCRBS interrogator locations, transmitter powers, and repetition frequencies as listed in ECAC's IFF Master File. The numerical results are presented graphically to display the dependence on signal level, noise level, and geographical location between Boston and Washington, D.C. A concept referred to as "effective interference tolerance" is introduced, and numerical evaluations are presented to indicate the accuracy of this concept.
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Summary

An analytical study is performed to determine the effects of ATCRBS P2 pulses as interference to DABS uplink transmissions. These effects constitute a major component of all uplink error-producing mechanisms that are anticipated to occur in DABS operation. The study is fomulated in a way that includes effects of both...

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Effects of ATCRBS P2 pulses on DABS reliability
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