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Batson, B. H.

Publications and source records attributed to Batson, B. H..

31 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Space Shuttle communications - Wideband direct link signal and system design

This paper describes the design of a wideband S-band communications link from the Space Shuttle Orbiter to a ground-based terminal. This link will be used for transmission of television, digital data (various rates), or analog data, and is of interest because of the presence of bandwidth, power, and hardware constraints. The procedure followed to arrive at an overall signal and system design is outlined, and system performance margins are presented for various operational configurations. Finally, the growth potential of this link for digital data transmission is discussed.

Batson, B. H.↗
NASA NTRS1973

Performance of binary FSK data transmission systems

Matched-filter detection of binary signals is discussed in terms of the probability of bit error. The equations for the probability of error are derived for coherent phase shift keying, and coherent frequency shift keying (FSK). Suboptimum detection of FSK signals is also discussed for discriminators.

Batson, B. H.↗
NASA NTRS1973

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.

Batson, B. H.↗
NASA NTRS1973

A variable-data-rate, multimode quadriphase modem.

This paper describes the design and performance of a highly versatile modulator and demodulator recently developed to facilitate the evaluation of various digital communications links. The modem is capable of either PSK or QPSK operation and can accommodate a very wide range of continuously tunable data rates (1 kbps to 30 Mbps in each of two channels). In the QPSK mode, operation is possible using either a single serial data stream (single channel operation) or using two mutually independent, unrelated, and asynchronous data streams (dual-channel operation). Integrate and dump detectors are used at the demodulator for regeneration of the data stream(s). Measurements indicate that the performance of the overall system (including the bit detectors) is within 2 dB of the theoretically optimum performance of either PSK or QPSK at any rate within the range of rates provided by the modem, and is within 1 dB of theoretical over most of the range of rates.

Allen, R. W.↗
NASA NTRS1973

A command encoding scheme for a multiplexed space communications link

This paper describes a command encoding scheme which was conceived to provide the necessary error protection for digital commands from a ground-based terminal to a manned spacecraft. The selected approach is compatible with a time-division multiplexing scheme which combines the command channel with two digital voice channels prior to transmission over the RF link. The command encoding scheme is also fully compatible with a channel encoding strategy which is applied to the multiplexed bit sequence (commands plus voice) to provide increased link efficiency. Implementation aspects of the command encoder and decoder are discussed and the system end-to-end performance improvement provided by the command encoding scheme is calculated.

Huth, G. K.↗
NASA NTRS1972

Simulation results for the Viterbi decoding algorithm

Concepts involved in determining the performance of coded digital communications systems are introduced. The basic concepts of convolutional encoding and decoding are summarized, and hardware implementations of sequential and maximum likelihood decoders are described briefly. Results of parametric studies of the Viterbi decoding algorithm are summarized. Bit error probability is chosen as the measure of performance and is calculated, by using digital computer simulations, for various encoder and decoder parameters. Results are presented for code rates of one-half and one-third, for constraint lengths of 4 to 8, for both hard-decision and soft-decision bit detectors, and for several important systematic and nonsystematic codes. The effect of decoder block length on bit error rate also is considered, so that a more complete estimate of the relationship between performance and decoder complexity can be made.

Batson, B. H.↗