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A digital communications system for manned spaceflight applications.A highly efficient, all-digital communications signal design employing convolutional coding and PN spectrum spreading is described for two-way transmission of voice and data between a manned spacecraft and ground. Variable-slope delta modulation is selected for analog/digital conversion of the voice signal, and a convolutional decoder utilizing the Viterbi decoding algorithm is selected for use at each receiving terminal. A PN spread spectrum technique is implemented to protect against multipath effects and to reduce the energy density (per unit bandwidth) impinging on the earth's surface to a value within the guidelines adopted by international agreement. Performance predictions are presented for transmission via a TDRS (tracking and data relay satellite) system and for direct transmission between the spacecraft and earth. Hardware estimates are provided for a flight-qualified communications system employing the coded digital signal design.
Document ID
19730053961
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Batson, B. H.
Moorehead, R. W.
(NASA Johnson Space Center Houston, Tex., United States)
Date Acquired
August 7, 2013
Publication Date
January 1, 1973
Subject Category
Communications
Meeting Information
Meeting: International Conference on Communications
Location: Seattle, WA
Start Date: June 11, 1973
End Date: June 13, 1973
Accession Number
73A38763
Distribution Limits
Public
Copyright
Other

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