• 120 Mb/s and 240 Mb/s Bit Synchronizer-Signal Conditioners for NASA High Data Rate Applications

      Gray, J. S.; Harris Electronic Systems Division (International Foundation for Telemetering, 1976-09)
      Two bit synchronizer-signal conditioners (BSSC) developed for NASA high data rate applications such as earth resources monitoring are described. One BSSC is centered at 120 Mb/s and the other at 240 Mb/s. These subsystems are featured out of the total hardware developed* because the BSSC is such a key subsystem in determining overall system statistical performance. These units represent an evolution of high data rate technology toward the versatile any data rate BSSC's available at low data rates. Numerous inputs/outputs, control functions, indicators, plus the ability to minimize the effects of various signal perturbations are provided. Examples of allowed perturbations are input level variations, bit rate variance static and dynamic, baseline, transition density, bandlimiting, etc., as well as noise. Emphasis in the past has been primarily concerned only with noise.
    • An Adaptive Intrusion Data System

      Johnson, Charles S.; Sandia Laboratories (International Foundation for Telemetering, 1976-09)
      An Adaptive Intrusion Data System (AIDS) was developed to collect data from intrusion alarm sensors as part of an evaluation system to improve sensor performance. AIDS is a unique digital data compression, storage, and formatting system. It also incorporates capability for video selection and recording for assessment of the sensors monitored by the system. The system is software reprogrammable to numerous configurations that may be utilized for the collection of environmental, bi-level, analog and video data. The output of the system is digital tapes formatted for direct data reduction on a CDC 6400 computer, and video tapes containing timed tagged information that can be correlated with the digital data.
    • Analysis and Decomposition of Complex Real-Time Processes with a Real-Time Schemata Model

      Adrion, W. R.; Frick, P. A.; Szulewski, P. A.; Oregon State University (International Foundation for Telemetering, 1976-09)
      In this paper a formal model for real-time processes is expanded to analyze structured, complex algorithms. Structured forms have inherent modularity and the authors discuss advantages of mapping such processes on distributed micro or mini processor networks. Processes under consideration are subject to random interrupts by independent I/O demands. Degradation of total system performance due to these demands is discussed. Extentions and ongoing research are mentioned.
    • The Application of High Density Tape Recording to Image Processing

      Heffner, Paul; NASA Goddard Space Flight Center (International Foundation for Telemetering, 1976-09)
      The Image Processing Facility at Goddard Space Flight Center has the requirement to move volumes of digital data (10¹¹ data bits per day) that exceed the capacity of conventional computer tape. This paper presents the requirements for a high density digital tape recorder compatible with conventional computer systems. The steps leading to the formulation of these requirements are described. The use and interaction of the recorder with the various elements in the facility are treated. The formulation of the requirements resulted in the selection of a Honeywell Model 96 Wideband II tape transport modified by Martin Marietta Corporation for digital serial-in, serial-out operation. This selection followed a competitive procurement action.
    • ATS-6 European L-Band Aeronautical Experiments

      Brown, D. L.; Guérin, Y.; Melchior, G.; Absolonne, F.; European Space Tecnhology Centre (International Foundation for Telemetering, 1976-09)
      This paper describes the European experiments and test results obtained in L-band (1550-1650 MHz),using the NASA ATS-6 satellite, to conduct communication and navigation tests over the North Atlantic thus assisting in the definition of modulation techniques to be used with an Aeronautical Satellite System, AEROSAT. The experiments conducted by ESA and some of its member states covered voice, data transmission and ranging measurements. The tests were performed on board a Comet IV aircraft equipped with a slot dipole array antenna, especially designed to operate within the coverage required in the AEROSAT MOU (Memorandum of Understanding for the AEROSAT programme signed by Europe (ESA), the USA (FAA) and Canada (DoT) in August 1974. The voice tests compared DELTA-PSK with adaptive NBFM using test tapes consisting of logatoms, SCIM sequences, and PB word lists. An investigation of multipath noise effects on the PSK data transmission system was carried out and led to the general conclusion that this problem is a serious one for coherent demodulators. The DECPSK system tested exhibited a strong tendency towards a Rayleigh channel BER situation at low antenna signal to multipath interference ratios. The ranging results show the feasibility of achieving standard deviations of range of around 500-600 m for the PLACE tone system with its rather short integration time of 120 ms, and 100 m for the DIOSCURES pseudo random coded system operated on a CW basis.
    • Automated Meteorological Data Acquisition System

      Ohmae, Yoshitsugu; Nippon Telegraph and Telephone Public Corp. (International Foundation for Telemetering, 1976-09)
      This paper describes the Automated Meteorological Data Acquisition System (AMeDAS) developed co-operatively by the Japan Meteorological Agency (JMA) and the Nippon Telegraph and Telephone Public Corporation (NTT). The object of this system is to collect exact meteorological data in Japan automatically, and to process it expeditiously by computer. The automatic meteorological observation equipments which observe the amount of precipitation, wind speed/direction, sunshine duration and air temperature, are located at about 1,300 points throughout Japan. The data obtained are collected at the computer center through NTT's telecommunication network by automatic telemetering. After rearrangement, data are sent to about 60 forecasting centers through leased lines. Using these data, the forecasting centers can make accurate weather forecasts to enable taking appropriate measures against disasters.
    • Automatic Control System for Routing of Telemetry Data Signals

      Brandenburg, D. W.; Ehrsam, E. E.; Electrospace Systems, Inc.; Vandenberg Air Force Base (International Foundation for Telemetering, 1976-09)
      The primary role of the Space and Missile Test Center (SAMTEC) is to provide support for the relatively large number of various types of missiles launched from Vandenberg Air Force Base (VAFB). Associated with this function is the requirement to provide telemetry decommutation/data processing systems capable of processing the telemetry transmitted by the missiles. At present, the telemetry data is routed to and from the analog tape recorders and bit synchronizers through patch boards, which totals over 200 inputs. This represents a myriad of patching combinations when considering the number of different missile formats and outputs that have to be manually patched and unpatched. SAMTEC contracted with Electrospace Systems, Inc., (ESI) for a dry reed relay switching system. The switching system, Analog Data Equipment Switching System (ADESS), consists of seven matrices under the control of a Digital Equipment Corporation (DEC) Model PDP-11/05 minicomputer. The ADESS matrices 1 and 2 are three stage switching systems with the respective input/output - 100 x 90 and 60 x 70. Matrices 3 through 7 range from a 40 x 40 down to a 10 x 20 rectangular matrix configuration. Matrix 1 has a frequency response range of DC-12MHz, matrices 2 through 6 have a range from DC- 3MHz, and matrix 7 ranges from DC-15MHz. The PDP-11/05 peripherals include a CRT/Keyboard and dual floppy disk which controls the latching and status of the matrix switches and stores the mission set up files which can be rapidly called up by the operator. The ADESS will decrease turn around by up to ten times as compared to present operations.
    • A Bound on Viterbi Decoder Error Burst Length

      Curry, S. J.; Harmon, W. D.; Aerospace Corp. (International Foundation for Telemetering, 1976-09)
      A maximum likelihood (Viterbi) decoder used with a convolutional code on a Gaussian channel produces decoding errors which tend to occur in clusters or bursts. A method is described for deriving an upper bound on the probability of occurrence of error bursts of a given length. The method applies to the optimum convolutional codes found by Odenwalder, for which the codeword weight distribution is partially known. Laboratory measurements of error burst length at signal-to-noise ratios greater than 4 dB indicate that the upper bound is useful for approximating the length of high-probability bursts, but is not precise enough to predict the probability of very long, low-probability bursts.
    • Broadcast Channels: Some Recent Developments and Open Problems

      Leighton, William J.; Tan, Harry H.; Princeton University (International Foundation for Telemetering, 1976-09)
      In this paper we consider some recent developments and open problems on broadcast channels. In particular we consider general discrete memoryless broadcast channel with two information sources. For the case where the two sources are independent we define a rate region R and show that arbitrarily reliable transmission of information over a general broadcast channel may be achieved with suitable coding at all rates in R. For the special case of degraded broadcast channels, R reduces to a previously known expression for the capacity region. R is calculated for a nondegradable broadcast channel which shows that previously known achievable rate regions can be substantially improved upon. We also define an achievable rate region for the case of dependent information sources. Finally, some open problems are discussed.
    • Calibration of Analog Measurement and Telemetry Systems

      Grant, Eugene; Martin Marietta Aerospace (International Foundation for Telemetering, 1976-09)
      A basic requirement of modern telemetry and instrumentation is a reference or standard to measure against. A brief survey of early flight tests and missile measurement systems shows the development of analog calibration. Frequency Modulation (fm), telemetry, Pulse Amplitude Modulation (PAM), and commutator calibration will be discussed, as well as measurement resistance calibration comparison and the newer actual instrument stimulation techniques. Factors influencing calibration stability and accuracy will be reviewed with a qualitative discussion of accuracy and frequency of calibration as a function of system requirements and measurement accuracy. Digital techniques and components now allow greater accuracy, stability and minaturization of calibration systems. Low power Schottkey transistors, transistor logic (TTL) and Complementary Metal-Oxide Semiconductor (CMOS) circuitry allows ease of design of calibration systems. With these newer calibrators, no measurement system should suffer from a lack of accurate calibration.
    • Candidate Receivers for Unbalanced QPSK

      Weber, Charles L.; University of Southern California (International Foundation for Telemetering, 1976-09)
      Candidate receivers for unbalanced QPSK signal foremats have been studied. The fourth power receiver is shown to be an unsatisfactory choice unless the power division is close to 50-50 or 100-0. The Costas loop receiver which tracks on the high data rate signal of the unbalanced QPSK waveform is shown to perform satisfactorily. Approximate error rate computations, show that the Costas loop considered performs within a few tenths of a dB of the ideal receiver.
    • Cascaded Coherent Tracking Systems with Time-Varying Channels

      Weber, William J., III; Yuen, Joseph H.; California Institute of Technology (International Foundation for Telemetering, 1976-09)
      An approach is given to the analysis of two-way coherent tracking systems in which the transmitted signals have passed through linear time-varying channels. The specific channel considered is the lognormal fading channel, although the results and techniques can be extended to other channels such as the Rice and Rayleigh channels. The performance of the system is characterized by the steady state probability density function of the reduced phase error process in the second tracking loop. Particular numerical examples and system performance curves are given to illustrate the theory for channel models and two-way systems of practical interest.
    • A Code Structure for Certain Coma Environments

      Milstein, Laurence B.; Ragonetti, Ronald R.; R.P.I. (International Foundation for Telemetering, 1976-09)
      Certain communication systems which employ code division multiple access as a means of supporting multiple users need very long codes to guard against the threat of intentional jamming, but cannot tolerate the lengthy acquisition time which long codes usually require. As a possible solution to this problem, the use of combination sequences has been suggested, and this paper presents some new results, both analytical and numerical, on this technique.
    • Command and Control of a Large, Unmanned, Undersea Vehicle

      Linders, Thomas E.; Lockheed Missiles & Space Co., Inc. (International Foundation for Telemetering, 1976-09)
      A system incorporating commercial modems and two twisted-pair shielded wires makes it possible to control/monitor a large unmanned undersea vehicle from a surface vessel. This paper summarizes the design, explains the rationale for it, and describes some of the problems encountered and their solution.
    • Comparison of PCM Codes for Direct Recording

      King, D. A.; Pacific Missile Test Center (International Foundation for Telemetering, 1976-09)
      The bit packing performance of randomized-non-return-to-zero (randomized- NRZ,) odd parity-NRZ, delay modulation, and bi-phase (Bi-Ø) in direct recording was experimentally compared at a bit error probability (BEP) of 10⁻⁶. The effect of bit patterns, record and reproduce levels, bias level, tape speed, tape recorder bandwidth, bit synchronizers, and crossplay between tape recorders on bit packing density was investigated. At high bit packing densities, significant variations in data quality were found for changes in these parameters. This imposes limitations on practical bit packing densities. Some bit synchronizers were found to seriously reduce bit packing densities. Results show randomized-NR.Z to be superior to the other codes in bit packing density.
    • Considerations for Distributed Industrial Control Systems

      Griem, P. D., Jr.; Bernard, J. W.; Foxboro Company (International Foundation for Telemetering, 1976-09)
      For a variety of reasons, industrial plant control systems have been increasingly complex and expensive. Economic and reliability considerations have initiated a trend toward distributing control system functions among communicating components, utilizing the new microprocessor and communication technologies. Any new technology brings new capabilities, but also new engineering design considerations and trade-offs. This paper attempts to outline some of the important system design issues.
    • Convolutional Coding At 50 Mbps for the Shuttle Kuband Return Link

      Batson, Bartus H.; Huth, G. K.; Lyndon B. Johnson Space Center; Axiomatix (International Foundation for Telemetering, 1976-09)
      Error correcting coding is required for 50 Mbps data link from the Shuttle Orbiter through the Tracking and Data Relay Satellite System (TDRSS) to the ground because of severe power limitations. Convolutional coding has been chosen because the decoding algorithms (sequential and Viterbi) provide significant coding gains at the required bit error probability of 10⁻⁶ and can be implemented at 50 Mbps with moderate hardware. While a 50 Mbps sequential decoder has been built, the highest data rate achieved for a Viterbi decoder is 10 Mbps. Thus, five multiplexed 10 Mbps Viterbi decoders must be used to provide a 50 Mbps data rate. This paper discusses the tradeoffs which were considered when selecting the multiplexed Viterbi decoder approach for this application.
    • Cost-Effective Coding Implementations for Computer Communication Systems

      Chien, R. T.; Coordinated Science Laboratory (International Foundation for Telemetering, 1976-09)
      Due to the recent developments in computer hardware and cost reduction, many powerful coding techniques can now be implemented to achieve high reliability at low cost. In this paper we examine the necessary ingredients for successful applications and delineate the systems variables and their inter-relationships. A number of sample applications will be presented to illustrate a systematic procedure to evaluate, select design and implement high performance and low cost systems for error correction and error detection. Implementation approach is considered including hardware, software, microprogramming ROMs, RAMs and LSI.
    • Degradation of FSK Detection Performance Due to Tone Phase Jitter

      Holmes, Jack K.; Hedin, George L.; TRW Defense; Space Systems (International Foundation for Telemetering, 1976-09)
      The paper develops some new results for the degradation in SNR, due to unwanted phase jitter, for a FSK receiver system. The unwanted phase modulation is assumed to be present equally on either FSK tone and is modeled as a sample function of a Gaussian random process. Results are derived based on a standard type FSK system employing bandpass filters, square law envelope detectors, a subtractor, and a post detection lowpass data filter. The degradation was found to depend on the mark-space filter bandwidths, the doppler frequency of the received tones, the nominal SNR and the post detection filter bandwidths. The degradation is minimal for small doppler shifts; however, once the tones, in the predetection filters were displaced to within the post detection filter bandwidth of the predetection filter band edge, the degradation increased dramatically. This was due to the fact that the filtering of the phase noise caused the envelope detectors to produce self noise. In fact, at high SNR's the degradation is primarily due to self noise or envelope distortion due to filtering of the phase jitter spectrum. It is important to point out that the degradation found here is due only to phase noise effects and not sin χ/χ losses. The results derived here are accurate for phase jitter variances ≲0.1. In addition, it is assumed that the lowpass equivalent filter impulse response of the bandpass filter be real, that is, the lowpass equivalent transfer function must be hermetian symetric.
    • A Digital Data Interleaver

      Goodwin, John E.; Martin Marietta (International Foundation for Telemetering, 1976-09)
      Many future space programs such as Space Shuttle contain a number of payloads, each generating its own digital data stream. It is frequently desirable to combine these data streams in a composite serial stream for the telemetry down link. The circuitry for combining these data streams should be as transparent as possible to the design and operation of individual data source subsystems. A concept is described for interleaving the data of several sources without any subsystem synchronization, few limitations on data rates, a no restrictions on formats. All data are accepted without loss and the composite stream is formatted in accordance with IRIG standards. The interleaver requires the use of artificial fill data to assure the possibility of accepting and formatting asynchronous data symmetrically; therefore, methods of error detection and correction of fill words are discussed to ensure nonambiguity of data and fill work.