• A Low Level Amplifier for Precision Multiplexing

      Temkin, Bruce M.; General Dynamics (International Foundation for Telemetering, 1976-09)
      An amplifier has been designed for high or low level multiplexing for aerospace PCM data acquisition systems. It was designed to provide "instrumentation amplifier" quality under conditions of high common mode, high or low rate random access operation and broad operating temperatures. It has shown versatility in operation, provides common mode rejection in excess of 125 db (RTI) and can be tailored for a drift temperature coefficient of less than 0.2 μV/°C (RTI)
    • An RF Monopulse Attitude Sensing System

      Tammes, J. B.; Bleiweis, J. J.; Hollandse Signaalapparaten; COMSAT Corporation (International Foundation for Telemetering, 1976-09)
      The application of RF monopulse sensing techniques for communications satellite attitude determination was investigated. An engineering model of a two channel 6 GHZ spaceborne RF monopulse attitude sensor capable of measuring roll, pitch and yaw was developed. RF attitude sensing provide attitude measurements compatible with the requirements of future body and spin stabilized satellites employing narrow antenna beams without recourse to mechanical motion. Sensor alignment errors are greatly reduced since the sensing element is a physical part of the antenna array. Troublesome operational difficulties of sun and moon interference are also eliminated. Yaw angle is determined through measurement of roll and pitch angle to two separated beacons. Experimental results including a preferred design, reflecting future stabilization and long life requirements are presented.
    • Production Counting Using a Computer Network

      Knoop, Donald E.; Loessel, Mark C.; Whirlpool Corp. (International Foundation for Telemetering, 1976-09)
      The advent of microprocessors has made possible the development of low cost intelligent terminals for industrial applications. Several of these "smart" terminals can be connected to a communications network which is controlled by a it "master" computer. Such a computer network has been developed at Whirlpool Research for use in production counting for inventory control purposes. This paper discusses the design, development, installation and debugging of the production counting system. The advantages and limitations of this type of computer network are discussed in the context of the industrial environment.
    • Recent Advances in Coding for Multiple Access Communication Systems

      Pursley, M. B.; University of Illinois (International Foundation for Telemetering, 1976-09)
      During the past few years it has been demonstrated that coding can play a major role in multiple-access communication systems. In addition to providing errorcontrol capability as in a single-user system, coding can actually provide the multipleaccess capability in a multi-user system. In this paper we concentrate on one such system, the spread-spectrum multiple-access system in which the communication capacity of the channel is shared by several asynchronous radio frequency signals that occupy the same bandwidth. Recent results on the analysis of these systems and on the selection of codes for multiple-access applications are presented.
    • Low Cost Data Compression

      Hellman, Martin E.; Stanford University (International Foundation for Telemetering, 1976-09)
      The large volumes of raw data involved in telemetry often require compression prior to transmission over a limited data rate channel. If the transmitter is located in a remote location, power, reliability and cost considerations add the requirement that the encoder be fairly simple, while the decoder can be much more complex. A similar encoder-decoder complexity tradeoff exists if there are many sensing stations (and encoders) but only one receiving station (and decoder). This paper describes a technique which is well suited to such applications in that it places almost all of the computational burden on the decoder, and requires only an extremely simple encoder.
    • On a Class of Codes of Delsarte

      Welch, L. R.; University of Southern California (International Foundation for Telemetering, 1976-09)
      In reference [1], Delsarte generalized a class of codes due to Chien and Choy [2] which, in turn, are a generalization of Goppa Codes [3]. Delsarte shows that almost all of these codes meet the Gilbert-Varsharmov bound, a result which is also true of Goppa codes [4]. Both of these results are obtained by showing that the actual minimum distance is much larger than the "designed" distance and approaches the G-V bound for the designed rate. This talk raises the question as to how large the actual rate can be for fixed design distance. No new theorems are presented but two well known theorems are proved in the context of Delsarte's presentation.
    • Remote Controlled Telemetry Receiver Considerations

      Knowles, Robert C.; Microdyne Corporation (International Foundation for Telemetering, 1976-09)
      As the complexity of telemetry systems increases, the desirability of using remote controlled receivers in these systems to reduce human error, setup time, and premission calibration time increases. The specification of such receivers needs to be done carefully to stay within economic and space limitations. A general discussion of possible system objectives is given in which basic decision questions are raised on the degree of remote control required. A tabulation of receiver functions and controls is given followed by detailed discussion of these various parameters in terms of feasibility, problem areas, space requirements and cost where it represents a major impact. The computer-receiver interface is discussed in terms of how this choice will affect cost and system compatibility with other types of equipment. These discussions should provide some insight in the tradeoffs required in specifying a remotely controlled telemetry receiver.
    • MFSK Frequency Acquisition and Synchronization for the Jupiter Probe-to-Relay Communication Link

      Fluchel, R. B.; Lee, G. M.; Paddon, E. A.; McDonnell Douglas Astronautics Co. (International Foundation for Telemetering, 1976-09)
      This paper discusses the coarse frequency acquisition problem and the fine frequency tracking problem for a communication link between a spacecraft and a probe entering the atmosphere of Jupiter. A coded noncoherent MFSK modulation format is assumed along with a severely fading link. Fine frequency tracking is shown to be a more serious problem than coarse acquisition.
    • Maximum Likelihood Decoding Scheme for Convolutional Codes

      Ng, Wai-Hung; Kim, Frank M. H.; Tashiro, Satoru; The Boeing Aerospace Company (International Foundation for Telemetering, 1976-09)
      In recent years the application of coding techniques to enhance digital data transmission has become widely accepted. In general, one would assume that a maximum likelihood decoding of convolutional codes would be impractical for long constraint length codes because the general approach of sequential decoding algorithms utilize very few properties of the code and hence require a considerable effort to decode the received data sequence. In this paper, several structure and distance properties of the convolutional codes for different constraint lengths are derived and utilized in developing an efficient maximum likelihood decoding scheme. Under the proposed decoding threshold conditions, which are functions of the distance properties of the utilized codes, the required number of decoding operations can be reduced markedly. The analysis has been supported by computer simulations and by the development and testing of a prototype decoder. Key results are presented and discussed.
    • 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.
    • A Digital Instrumentation System for Automotive Impact Tests

      Hu, A. S.; Bean, S. P.; Maure, J. J.; New Mexico State University (International Foundation for Telemetering, 1976-09)
      Automotive impact tests require the transmission of large amount of measurement data through drag cables. The traditional practice of using FM technique is tedious and expensive. An on-board PCM system which accepts 112 analog inputs and 91 bi-level inputs has been used successfully at the Daisy Impact Sled Test Track located at the Holloman AFB. This system utilizes a two-conductor pair drag cable. It can also be telemetered by pulse modulating a radio frequency carrier.
    • 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.
    • Performance Bounds on Spread Spectrum Multiple Access Communication Systems

      Yao, Kung; University of California (International Foundation for Telemetering, 1976-09)
      Several approaches for the evaluation of upper and lower bounds on error probability of spread spectrum multiple access communication systems are presented. These bounds are obtained by utilizing an isomorphism theorem in the theory of moment spaces. From this theorem, we generate closed, compact, and convex bodies, where one of the coordinates represents error probability, while the other coordinate represents a generalized moment of the multiple access interference random variable. Derivations for the second moment, fourth moment, single exponential moment, and multiple exponential moment are given in terms of the partial cross correlations of the codes used in the system.
    • Telemetry Packetization for Improved Mission Operations

      Greene, Edward P.; NASA (International Foundation for Telemetering, 1976-09)
      The requirements for mission operations data management will accelerate sharply when the Space Transportation System (i.e., Space Shuttle) becomes the primary vehicle for research from space. These demands can be satisfied most effectively by providing a higher level source encoding function within the spaceborne vehicle. An Instrument Telemetry Packet (ITP) concept is described which represents an alternative to the conventional multiplexed telemetry frame approach for acquiring spaceborne instrument data. By providing excellent data integrity protection at the source and a variable instrument bandwidth capability, this ITP concept represents a significant improvement over our present data acquisition procedures. Realignments in the ground telemetry processing functions are described to take advantage of the ITP concept and to make the data management system more responsive to the scientific investigators.
    • A Microprocessor-Based Computer Developmental System for Satellite Application

      Redman, Paul C.; COMSAT Laboratories (International Foundation for Telemetering, 1976-09)
      This paper describes the hardware and software requirements for a microprocessor-based onboard computer developmental system. In particular, it describes the use of standardized modules which may be assembled in flight form to permit the microprocessor to become a viable alternative to dedicated hard-wired logic implementation in satellite electronic control applications. In addition, it addresses the problem of using electronic control hardware which is common to a majority of applications, with the uniqueness contained in the software. The processor development system includes the basic characteristics of the onboard processor as well as those of the ground-based software development system. The use of these two components to realize a finished onboard processor system is described, and the efficiency advantages of the developmental system are indicated.
    • Elements of a Broadband Biomedical Communications Network

      Henderson, Earl; National Library of Medicine (International Foundation for Telemetering, 1976-09)
      This paper describes the experimental Broadband Biomedical Communications network being developed by the Public Health Service. This network will combine modern satellite communications technology with modified television broadcast techniques to support health experiments in decentralized education, research dissemination and teleconferencing. Small satellite earth terminals will be located in six cities to transmit and receive audiovisual programs. This network will incorporate the Canadian-American Communications Technology Satellite (CTS) to evaluate the cost-effective use of interactive broadband communications systems.
    • Telemedicine: Patient Monitoring in Unusual Environments

      Hanley, John; University of California, Los Angeles (International Foundation for Telemetering, 1976-09)
      Of the several advantages telemetry systems have to offer the burgeoning field of patient monitoring, we have previously stressed recording from freely moving patients unencumbered by lengthy cables and unattached to conventional bulky machines. Paramount in the applications of systems designed and fabricated in our laboratory of Environmental Neurobiology have been the monitoring of patients afflicted with temporal lobe epilepsy in which the capture of unilateral or bilateral EEG seizure activity dictates the possibility or futility of neurosurgical intervention (1). Together with sophisticated computer analyses of neurophysiological data, telemetry has also made it possible to identify EEG correlates of bizarre schizophrenic ritualistic behavior virtually impossible to capture by conventional hard-wire techniques (2). This presentation emphasizes another aspect of the utility of telemetry: the opportunity to record from patients in meaningful circumstances outside the sterile environs of the Neurophysiology Laboratory which sometimes involves freedom of movement and sometimes quiescence. The critical element in these situations is the unacceptability of bulky machinery and its attendant problems. Two such environments are the operating room and the sleep research and treatment laboratory or bedroom. Our current fairly extensive telemetry studies involve both of these surrounds. These activities will now be discussed.
    • High-Density Digital Data Recording/ Reproducing System

      Leighou, Robert O.; Martin Marietta Corporation (International Foundation for Telemetering, 1976-09)
      Problems associated with reliably recording and reproducing digital data at densities of 10 to 30 kilobits per inch and the solutions to these problems are discussed. The three problems are skew, dc offset, and tape imperfections. The solutions are to use a 14-track, wideband II tape recorder; record NRZ-L; use a 24-bit sync word, 504-bit frame length, and odd parity in every 8-bit byte; and to employ circuit design techniques that minimize the effects of the remaining dc offset and tape imperfections.
    • Distribution of Intelligence and Input/Output in Data Acquisition Systems

      Rose, Charles W.; Schoeffler, James D.; Case Western Reserve University; Cleveland State University (International Foundation for Telemetering, 1976-09)
      Low cost, high performance microprocessors are being used in several distributed intelligence architecture to replace conventional data acquisition systems. Each distributed topology has certain attributes which affect its suitably for data acquisition applications: cost and position modularity, behavior in the presence of a fault, logical complexity, and bottlenecking. The software organization of these systems is impacted by the distribution of intelligence and input/output, particularly in the areas of task communication, error recovery, data base management, and operating systems structure. A ring structure has been developed for data acquisition and control, which uses distributed microprocessor intelligence and modified serial CAMAC protocol. A general purpose instrument and communications control module based upon INTEL 3000 microprocessors has been built.
    • Timesharing without Synchronization

      McEliece, Robert J.; Rubin, Arthur L.; Caltech’s Jet Propulsion Laboratory (International Foundation for Telemetering, 1976-09)
      The capacity region of a multiple-access channel has recently been identified as the convex hull K̄ of a certain set K of points in the first quadrant of the (R₁,R₂) plane. For a pair of rates in K, a more or less standard random coding argument can be used to show the existence of a good pair of codes. But for points in K̄-K, it is apparently necessary for the two senders to use some form of timesharing to achieve the desired rates. However, in order to timeshare, at least one of the senders must have knowledge of the other's phase; and in many practical situations this knowledge does not exist. In this paper we investigate the problems which arise in coding for multiple access channels when the senders cannot synchronize with each other.