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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Performance of DSRC V2V Communication Networks in an Autonomous Semi-Truck Platoon Application

Autonomy for multiple trucks to drive in a fixedheadway platoon formation is achieved by adding precision GPS and V2V communications to a conventional adaptive cruise control (ACC) system. The performance of the Cooperative ACC (CACC) system depends heavily on the reliability of the underlying V2V communications network. Using data recorded on precision-instrumented trucks at both ACM and NCAT test tracks, we provide an understanding of various effects on V2V network performance: Occlusions - non-line-of-sight (NLOS) between the Tx and Rx antenna may cause network signal loss. Rain - water droplets in the air may cause network signal degradation. Antenna position - antennas at higher elevation may have less ground clutter to deal with. RF interference - interference may cause network packet loss. GPS outage - outages caused by tree cover, tunnels, etc. may result in degraded performance. Road curvature - curves may affect antenna diversity. Road grade - antenna may have limited vertical coverage. Our results, which include multiple plots and graphs and their analysis, build on those reported by others and could be of interest to researchers, practitioners, and end-users in the broader autonomous-connected vehicle community.

V2V communications, GPS, truck platoon, semi-auton↗
NASA NTRS1965

Detection of, and communication with space vehicles during atmospheric entry, problems in simulation

In considering the problem of communicating with outer space and detection of spacecraft from the ground, one usually has to worry about only the propagation characteristics of electromagnetic waves of vacuum wavelength falling within either one of the two well known "atmospheric windows," namely; (1) the "optical window" extending from about 0.3 microns to a few microns, and (2) the "RF window" extending from a few millimeters to about 30 meters in the wavelength scale. However, during entry (or reentry) of a spacecraft into the earth's atmosphere, there exists two physical phenomena which tend to complicate the communication problem on the one hand, and to simplify the detection problem on the other hand.

Detection↗
NASA NTRS1965

Principles of communication engineering.

Textbook on communication engineering emphasizing random processes, information and detection theory, statistical communication theory, applications, etc

COMMUNICATION THEORY↗
NASA NTRS1965

The Post Office communication system ground station at Goonhilly, Cornwall

The initial purpose of the Post Office satellite system earth station at Goonhilly Downs, Cornwall, is to obtain information on the performance of experimental communication satellite systems; such information will be of great importance to the designers of systems for commercial operation. To facilitate this dissemination the UK and USA Governments prepared and signed, in February 1961, a Memorandum of Understanding regarding collaboration between the British Post Office and the United States National Aeronautics and Space Administration (NASA) on the testing of experimental communication satellites to be launched by NASA. The first phase of the tests covered Projects Telstar and Relay, both active satellites.

COMMUNICATIONS SATELLITE↗
NASA NTRS1965

Computing and data transmission for the prediction steering of the Goonhilly satellite-communication aerial

The Goonhilly satellite-communication aerial uses an 85-ft. diameter paraboloidal reflector with waveguide feed at the focus. The aerial is movable in azimuth and elevation, and is provided with independent feedback control systems for these two motions. During a satellite pass, the aerial must be steered so that its axis points continuously, and with high accuracy, in the direction of the satellite. Of the various possible methods of achieving this result, that based on prediction of satellite position has been adopted for the first transatlantic communication experiments using the Telstar and Relay satellites. The process by which orbital predictions originating in the USA are converted to substantially continuous real-time azimuth and elevation pointing instructions at Goonhilly is described herein.

GROUND STATION↗
NASA NTRS1987

Point-to-Point Multicast Communications Protocol

This paper describes a protocol to support point-to-point interprocessor communications with multicast. Dynamic, cut-through routing with local flow control is used to provide a high-throughput, low-latency communications path between processors. In addition multicast transmissions are available, in which copies of a packet are sent to multiple destinations using common resources as much as possible. Special packet terminators and selective buffering are introduced to avoid a deadlock during multicasts. A simulated implementation of the protocol is also described.

PROTOCOLS↗
NASA NTRS1989

Communication indices of crew coordination

The relationship between communication patterns and performance in 10 two-person flightcrews is explored with the aim of identifying speech variations which differentiate low- and high-error full mission simulator flights. Verbal data, transcribed from the videotaped performances, are treated as interactive sequences of speech events in which statements spoken by one crewmember are considered within the context of the other crewmember's prior and subsequent speech. Specific speech patterns characterized each crew, but the overriding findings included: a) marked homogeneity of patterns characterizing low-error crews, interpreted as the adoption of a standard form of communicating, and b) heterogeneity of patterns characterizing high-error crews, interpreted as the relative absence of a conventionalized form. Because conventions are regularities which confirm the expectations of those involved, predictability of crewmember behavior should be greater when standard conventions are followed. We conclude that such a practice can facilitate the coordination process and enhance crew performance.

Aerospace Medicine↗
NASA NTRS2001

The status of optical communications at NASA/JPL

Future NASA and commercial space missions will require communications terminals to provide higher data rate with lower mass and power. Optical communications is a rapidly developing technology in response to this demand.

optical communications↗
NASA NTRS2000

Status of Free-Space Optical Communications at JPL

Optical communications is a rapidly developing technology applicable to future NASA and commercial space missions that desire a communications terminal that provides a higher data rate with lower mass and power.

Optical Communications Lasers Detectors↗
NASA NTRS2000

Fine pointing control for free-space optical communication

Free-Space Optical Communications requires precise, stable laser pointing to maintain operating conditions. This paper also describes the software and hardware implementation of Fine Pointing Control based on the Optical Communications Demonstrator architecture.

free-space optical communication fine point contro↗
NASA NTRS1997

The Status of Ka-Band Communications for Future Deep Space Missions

Over the past decade, the Jet Propulsion Laboratory's Telecommunications and Mission Operations Directorate has invested in a variety of technologies, targeted at both the flight and ground sides of the communications link, with the goal of developing a Ka-band (32 GHz) communications capability for future deep space missions.

Power Amplifiers↗
NASA NTRS1996

Extreme Deep Space Communications

Recent work in deep space telecommunication systems has been performed in support of NASA's Mission to the Solar System planning activity. The results show that high bandwidth communications (higher thatn 1 Mbps) are feasible with communication infrastructure investments at targets of high exploration activity. These targets include Mars, Jupiter, and Neptune. Infrastructure improvements must also be made at Earth.

space telecommunications Mission to the Solar Syst↗