• Quantization for Signal Detection and Representation

      Kassam, Saleem A.; University of Pennsylvania (International Foundation for Telemetering, 1978-11)
      For digital representation of analog data the minimum mean-squared-error criterion is commonly used as a criterion for the basis of optimum quantizer design. In this paper we show that in some situations measures other than the minimum mean-squared-error may be more appropriate. For the signal representation problem, it is shown that the mean-absolute-error criterion has theoretical justification, as again for some signal detection problems it is shown that the mean-squared-error criterion is not the most appropriate criterion.
    • 20/30 GHz Satellite Systems Technology Needs Assessment

      Stevens, Grady; Wright, David; National Aeronautics and Space Administration (International Foundation for Telemetering, 1978-11)
      NASA is involved in exploring the potential of the 20/30 GHz bands as evidenced by the propagation work in the ATS series by NASA-Goddard and, more recently, by the systems and market effort by NASA-Lewis. This paper focuses on the system and market work done by NASA-Lewis. Included are results of previous contractual and in-house studies, as well as preliminary results of on-going market and system studies. Baseline concepts for evaluating technology needs are also included.
    • TDRSS Multiple Access Receiving Phased Array System

      DuPree, J. E.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1978-11)
      A 30-element phased array, with remote beamforming and multiple access signal design, is the basis for a new multiple access concept to be used by the Tracking and Data Relay Satellite System (TDRSS). System tradeoffs evolved a control and calibration concept which parallels modern estimation theory in dynamic systems and reduces the complexity of adaptive control while maintaining the necessary accuracy. A system dynamic model propagates "open loop" estimates of optimal weight vectors based on user satellite ephemerides derived from tracking data. A sampled-data closed loop adaptive control system periodically updates the beam-steering vector to eliminate parameter drifts and modeling errors, and to maintain the weight vector near optimum. The concept is primarily useful in the specified noninterference environment, though some nulling capability is possible.
    • A Coherent Receiver for QPSK and SQPSK Signals

      Alem, W. K.; Weber, C. L.; Axiomatix; University of Southern California (International Foundation for Telemetering, 1978-11)
      A demod-remod type of coherent tracking loop for conventional QPSK and staggered QPSK (SQPSK) is presented. The phase detector characteristic (S-curve) is determined. The effects of power unbalance and arm gain unbalance on the S-curve are presented. The steady state rms phase error is shown as a function of the signal-to-noise ratio at the output of the arm filters.
    • Processing Satellites

      Omura, Kim; University of California, Los Angeles (International Foundation for Telemetering, 1978-11)
      With few exceptions, satellite communications systems today employ conventional nonprocessing satellites that are often referred to as "bent pipes in the sky." These satellites merely act as nonlinear (TWT) amplifiers that transmit on the downlink the same signals plus noise (frequency shifted) that it receives on the uplink. It is now clear that the "micro-processor revolution" will impact on satellite technology and result in a new generation of communication satellites with various on-board digital processing. The orbiting experimental military satellites Les-8/9 are the first-of the new generation of processing satellites. Many more such satellites are now being considered with increasingly complex digital processing on the satellites. For military applications these on-board processing capabilities are listed below in increasing order of complexity.
    • Coherent Demodulation for Orthogonal Sideband and Carrier Tracking

      Udalov, Sergei; Axiomatix (International Foundation for Telemetering, 1978-11)
      A demodulation technique which permits simultaneous coherent and orthogonal tracking of a suppressed carrier and of the associated sidebands is described. The performance of a demodulator based on such a technique is defined for a general case and for a specific case of two-channel FM multiplexing. Experimental data supporting the analysis of the FM multiplexing mode of the demodulator is presented and discussed.
    • Subframe Switching in Data Communications

      Foschini, G. J.; Gopinath, B.; Hayes, J. F.; Bell Telephone Laboratories, Incorporated (International Foundation for Telemetering, 1978-11)
      An alternative to packet switching, designated as subframe switching is studied. In this technique the traffic flowing between a pair of nodes in the transport network is given a fixed capacity by means of time division multiplexing. This flow between two nodes, viewed as a single commodity, may consist of packets from many different terminals or ports connected to a node. The advantage of this technique over conventional packet switching lies in simplicity of switching at tandem nodes and in simplicity of operation, particularly in flow control. The disadvantage of subframe switching is that less efficient use is made of transmission capacity. An analysis of the technique is made with the aim of quantifying delay performance and buffering required. A preliminary study of the relative switching complexity of packet and subframe switching is undertaken. Numerical results indicate the relative merits of each method.
    • DSCS III Communications Satellite Performance

      Weinrich, A. W.; Horvath, A.; Harcar, A.; GE Space Division (International Foundation for Telemetering, 1978-11)
      The DSCS III satellite is the third generation space segment of the Defense Satellite Communication System. This satellite is unique compared to earlier DSCS satellites in that it has a six channel transponder designed for both FDMA and TDMA operation and realtime commendable uplink and downlink multibeam antennas. The antenna suit is designed to provide uplink anti-jam discrimination and selective coverage with a 61 element multibeam antenna 45 inches in diameter. The transmit antenna suit includes two 19 element multibeam antennas 28 inches in diameter that provide flexible selective coverage to maximize EIRP allocation and hence optimize satellite traffic thruput. The flexibility in antenna coverage and antenna - transponder interconnectivity allows the system operator to respond rapidly to wide variations in the deployment of forces precipitated by changing world events. This paper describes the overall DSCS III system in which the satellite functions and presents typical antennas patterns obtained with the DSCS III hardware built during the development phase of the program. In addition, overall program status is described and critical hardware elements are shown.
    • A Hybrid Data Compression Algorithm for Image Telemetry

      McCaughey, Dennis G.; University of Arizona (International Foundation for Telemetering, 1978-11)
      This paper presents an image coding algorithm using spline functions that is competitive with the more conventional orthogonal transform methods at data rates of 1 bit/pixel or less. Spline coding has the added attraction of an optical implementation arising from the fact that least squares image approximations also produces least squares approximations to the image derivatives. A first order spline is used to approximate the proper order derivative of the image whose order is determined by an analysis presented in the paper. The image derivative is then encoded and transmitted to the user who reconstructs the image by a k-1 order integration which can be done optically.
    • INTELSAT V Spacecraft Antenna Subsystem

      Jakstys, V. J.; Ward, H. T.; Ford Aerospace and Communications Corporation (International Foundation for Telemetering, 1978-11)
      Design and development has been completed on the Antenna Subsystem for the INTELSAT V Communications Satellite. The Communications antennas include two C-Band (transmit and receive) Hemi/Zone coverage antennas, two C-Band (transmit and receive) Earth Coverage antennas, two 11/14 GHz Spot Beam antennas and an 11 GHz Beacon antenna. The C-Band Telemetry and Command antennas consist of two directional beam telemetry (transmit) antennas, a dual-port toroidal beam telemetry antenna and two cardioid beam command (receive) antennas. The designs have been verified by measurements, and the test results indicate that all major performance requirements will be achieved.
    • A Hardware Comparison of Intermicroprocessor Communications Techniques

      Korgel, C.; Lohaus, T.; Pape, D.; Martin Marietta Corporation (International Foundation for Telemetering, 1978-11)
      A generalized multimicroprocessor utilizing the TI9900 and AMD2901 microprocessors is presented. Different types of microprocessors are used to provide extensive computational capability, versatile interprocessor communications, high reliability, and system flexibility. The system is especially suitable for high speed signal processing, data processing, and data handling. Measured data on the speed of interprocessor communication for three techniques is presented along with a comparative assessment of flexibility and reliability for the techniques.
    • Application of Microprocessors to Spacecraft Synthetic Aperture Radar Processing

      Arens, Wayne E.; California Institute of Technology (International Foundation for Telemetering, 1978-11)
      A ground-based digital synthetic aperture radar (SAR) processor capable of correlating images from raw spacecraft data at real-time rates is currently under development. The processor design requirements are particularly formidable due to (1) range migration effects resulting from planetary curvature and rotation, (2) antenna beam pointing errors, and (3) variation of the doppler reference function with changing orbital parameters. Based upon the current effort, this paper describes a candidate real-time on-board SAR processing implementation approach that might evolve for future spacecraft applications. Key features include the use of custom large scale integration (LSI) charge-coupled device (CCD) technology to accomplish the correlation functions and microprocessor technology to effect control.
    • Network Monitor/Control Concept for the Western Union Satellite Switched TDMA Advanced Westar System

      Markham, R.; Sahai, K.; Schimenti, M., Jr.; Western Union (International Foundation for Telemetering, 1978-11)
      A description of the network monitor and control and TT&C concepts for the Western Union Satellite Switched TDMA Advanced Westar System is presented. The paper includes a brief description of the major system elements, their functional relationship to the network management center, and the methods to be used for monitoring/responding to station/network performance, reallocating: burst assignments, satellite switch assignments and point-to-point (multipoint) connectivity; and failure restoration of satellite communication payload service. Network monitoring and control is achieved via information exchanges between the system Network Management Center and the various system elements including: Network Earth Stations, Master Reference Stations, the White Sands TT&C Center, Western Union O&M Centers, and Western Union Administrative Center. Communication between the TMC and these facilities will be established via both satellite (8 KBPS orderwire channel) and terrestrial links. Fine/Course timing between the network earth stations and the satellite switch will be provided via reference bursts transmitted by the system Master Reference Stations into each of the four zones associated with the individual satellite channels.
    • A Multiple FSK Microprocessor Demodulator/Decoder

      Sahmel, Rainer H.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      A demodulator is described that utilizes an interrupt-driven 8-bit microprocessor and an external digital counter to demodulate an 8-ary Frequency-Shift-Keyed input signal. After demodulation, the system correlates received groups of symbols with a stored code to derive and maintain character synchronization, and compute the decoded and error corrected output. The total device package count is less than 10, including the microprocessor with integral read/write memory and clock driver circuits, a Parallel Interface Adapter, a 1024 X 8-bit ROM, an 8-bit digital counter, a two-pole filter, a limiter and complete input and output buffering.
    • An Airborne Meteorological Data Collection System Using Satellite Relay (ASDAR)

      Bagwell, James W.; Lindow, Bruce G.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1978-11)
      The Aircraft to Satellite Data Relay (ASDAR) project was begun in 1975 as a joint NASA/NOAA program to provide an improved source of meteorological data for weather forecasting. The initiative for starting the project came from a recognition that much of our weather originates in the data sparse areas of the tropics and Southern Hemisphere. It was further recognized that these areas are frequently crossed by many of the modern, wide-body jet aircraft of the B-747, DC-10 type. These aircraft contain navigation and data systems capable of providing the following data: latitude, longitude, altitude, wind speed, wind direction, and outside air temperature. The ASDAR system consists of a data acquisition and control unit to acquire, store, and format this data; a transmitter to relay the formatted data via satellite to the ground; and a clock to time the data sampling and transmission periods. In cooperation with the National Oceanic and Atmospheric Administration (NOAA) the data is relayed to the ground via their Geostationary Operational Environmental Satellite (GOES) series and then to the National Meteorological Center (NMC) to aid in weather forecasting.
    • LSI Hardware for Data Communications

      Comisar, Gerald G.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      A review is presented of some new, low-cost, easy-to-use hardware for interfacing small-scale digital systems to telecommunications and data link networks. Devices featured are binary serial interfaces, protocol controllers (including SDLC and HDLC), data encryption units (including the new NBS Federal Standard), modems, and information encoders. Compatibility with existing microprocessors and future trends are discussed.
    • An Analysis of a Tandem Queueing System for Flow Control in Computer Networks

      Chu, W. W.; Faylolle, G.; Hibbits, D.; University of California, Los Angeles; I.R.I.A. (International Foundation for Telemetering, 1978-11)
      A tandem queueing system with constant service times and threshold control is modeled and analyzed in this paper. The input to the first queue is controlled by the buffer occupancy of the second queue. When the second queue has more than No customers, the input to the first queue will be rejected. The input to the second queue consists of the output from the first queue and an external input which is assumed to be Poisson distributed. The behavior of such a queueing system is analyzed and portrayed in graphs. The threshold control rejects input traffic to the first queue and avoids congestion at the second queue. As a result, the delay for an arrival to be serviced by both of the queues is much lower than the case without threshold control. As N₀ increases, the system behavior approaches the case of the system without threshold control. Such a queueing model is motivated by congestion control in a computer network. An example is given to illustrate the applications.
    • Multilevel SCPC System Design

      Horstein, M.; LaFlame, D. T.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      A method of assigning carrier levels in an SCPC system with mixed earth station G/Ts is developed which optimizes system performance for uniformly spaced and randomly assigned carrier frequencies. The optimum transponder backoff is shown to be identical to that for a system of uniform carriers in which the (common) earth station (G/T)⁻¹ is a weighted average of the different (G/T)⁻¹ values in the mixed system. With the transponder backoff determined, the carrier level to be transmitted to each station type is simply expressed in terms of the station G/T.
    • Medical Applications to Communications Satellites

      Shamaskin, Robert B.; Veterans Administration (International Foundation for Telemetering, 1978-11)
      It is recognized that closed circuit television and other electronic linkages, properly employed to deliver needed information, can be useful tools in the practice of medicine, particularly in providing linkage between distant points. In some instances terrestrial interconnection is practical, as in the case of short distances between communicating points. However, as distances become greater, so do the costs. Therefore, alternative cost effective methods of transmitting television and other types of signals for biomedical purposes are being sought. The development of high powered communications satellites demands consideration and experimentation. Therefore, the Veterans Administration is conducting a series of experiments to determine if and how communications satellites can be employed for diagnostic, therapeutic, educational and administrative purposes.
    • Image Quality Considerations of Compressed Video Imagery

      Pearson, J. J.; Millman, M. W.; Maitra, S.; Lockheed Palo Alto Research Laboratory (International Foundation for Telemetering, 1978-11)
      Most work to date on image data compression has been based on single static images and the use of mean square error (MSE) as an objective quality criterion. However, many current requirements for video bandwidth compression, such as Remotely Piloted Vehicle and "smart" ordnance video links, include dynamic (moving) scenery and severe channel noise. The image degradation effects of the bandwidth compression technique will then fall into three categories: Degradation of a static image; effects due to any frame segmenting and partial frame transmission used; and the impact of uncorrected channel errors. In this environment, the more powerful, but also more complex techniques, i.e., the various transform techniques, may provide less acceptable imagery than simple techniques (such as DPCM or Lockheed's CAQ algorithm) since their complexity may require frame slicing, i.e., the compression and transmission of only a segment of a frame during each frame period. Also, the one-dimensional techniques often prove more effective than twodimensional techniques because the vertical redundancy they retain can be used to eliminate uncorrected errors. The MSE criterion for image quality, known to be crude and often misleading in static images, is totally inadequate to quantify the impact of scene dynamics and uncorrected channel errors.