• International Telemetering Conference Proceedings, Volume 14 (1978)

      International Foundation for Telemetering, 1978-11
    • Hybrid Packet and Circuit Data Networks: Design and Operation Issues

      Gerla, Mario; University of California, Los Angeles (International Foundation for Telemetering, 1978-11)
      Experience with packet switching during the past decade has shown that the packet technology is very cost effective for bursty communications between computers and terminals. However, for applications characterized by a steady instead of bursty flow of information (e.g., file transfer, digitized speech, facsimile), it has been established that pure packet protocols are often inadequate because of the unnecessarily high line overhead and the high delay fluctuations between consecutive packets [1]. For such applications, a circuit switching approach (either physical or virtual) appears more advantageous [1],[2]. In the physical circuit approach, bandwidth is dedicated to a connection for the entire duration of the session; while in the virtual circuit approach the path is fixed at the beginning of the session and some expected bandwidth is guaranteed, in a statistical sense, along the path (but no physical bandwidth is assigned).
    • Detection of Moving Optical Objects

      Burczewski, R. M.; Mohanty, N. C.; Rockwell International (International Foundation for Telemetering, 1978-11)
      This paper deals with the detection of a moving optical object in the presence of background, sensor or star and other noise. The algorithms are derived to estimate noise statistics, and its extrapolation, signal statistics, and the criterion for detecting the moving objects. The performance of the algorithm has also been derived.
    • Bounded Error Data Compression at Constant Rate

      Gonsalves, Robert A.; Evans, Norman E.; Shea, Alicia; EIKONIX Corporation (International Foundation for Telemetering, 1978-11)
      We present a technique to compress M-bit data to N-bit data with a bounded error between the original and de-compressed data. The bounded error is established by quantizing the error signal of DPCM and by entropy encoding the quantized error. The fixed data rate is maintained by non-linear adaptation of the quantization interval on an intermittent basis. Examples of image data compression are given.
    • Spread Spectrum and Coding Techniques in Communication Systems

      Gerardi, F. R.; Otsuki, W. T.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      With the increase in complexity of military communications networks, a combination of spectrum spreading and error correction coding is typically required to provide adequate antijam protection. The specific system architecture utilizing these techniques is established in this presentation by performance requirements, system constraints, interface problems, and assumed jammer models. This presentation will describe various processing techniques with emphasis on their interactions and limitations. Two spread spectrum techniques for permitting operations in a jamming environment are considered: direct sequence (PN) and frequency hopping. The advantages and limitations of each technology will be discussed. The antijam capability of these spread spectrum systems can be improved by using various error correction coding schemes. These can (make more efficient use of the bandwidth allocation) as well as provide enhanced protection against pulse and tone jammers. The advantages, limitations, and constraints imposed on a communication system using various combinations of these techniques are discussed with particular emphasis on the system performance.
    • 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.
    • 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.
    • 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.
    • Defense Satellite Communication System

      Donovan, Andrew R., Jr.; Def. Comm. Eng. Center (International Foundation for Telemetering, 1978-11)
      This paper will present an overview of the Defense Satellite Communication System (DSCS) with emphasis on its current capabilities and future planning. The DSCS is DoD's strategic satellite communications system providing unique and vital worldwide service to the National Command Authorities (NCAs), Worldwide Military Command and Control System (WWNCCS), the White House Communications Agency (WHCA), the Defense Communication System, NATO-Allied nations and other special users. The DSCS will soon expand to encompass the Army/Air Force Ground Mobile Forces SHF-Tactical applications and the Advanced Airborne Command Post (AABNCP).
    • 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.
    • The American Satellite Transmission System

      Cacciamani, Eugene; Garner, William; American Satellite Corporation (International Foundation for Telemetering, 1978-11)
      In 1979, American Satellite Corporation will be the first on-line completely all-digital communications carrier. This will be accomplished when American Satellite Corporation's major trunking earth terminals are converted to operate TDMA at data rates up to 64 Mbps.
    • A Distributed Microcomputer Telemetry System for Spacecraft Applications

      Lord, Donald D.; California Institute of Technology (International Foundation for Telemetering, 1978-11)
      Three significant difficulties exist in using a set of microcomputers (or any computers) as an integral part of an on-board telemetry system. The difficulties arise in providing for: a) the precise timing required by a telemetry system, including accurate time-tagging of data samples; b) the interconnection of several (many) computers in a controlled, organized, understandable manner; c) the capability to allow computer controlled science instruments to operate relatively autonomously with minimum software interactions with other computers. The three items listed above are desirable features and are achievable with proper telemetry system architecture designs. This paper will address each of the three items and present an architecture that provides the desired features.
    • A Distributed Shortest - Path Algorithm

      Humblet, Pierre A.; Massachusetts Institute of Technology (International Foundation for Telemetering, 1978-11)
      The problem of routing in a data network is often treated by assigning traffic dependent lengths to the links of the network and routing traffic from node i to node j along the shortest path from i to j . We present a distributed algorithm in which the nodes cooperate to find all shortest paths. It runs asynchronously in every node and does not require the network topology, or even the number of nodes in the network, to be known a priori by the nodes.
    • 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.
    • 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.
    • Subjective Frequency Hopping System Consideration

      Dixon, Robert C. (International Foundation for Telemetering, 1978-11)
      The effects of frequency hopping on other communication systems will be addressed in this presentation. Tapes of frequency hopping system with varying hopping rates/ dwell times will be played to illustrate the effects.
    • Optical Antennas

      Kraemer, Arthur R.; Jones, Robert W.; GTE Sylvania Incorporated (International Foundation for Telemetering, 1978-11)
      Optical communication systems have the capability to transmit very high data rates (1-Gbps) over long distances. One primary reason is the narrow beamwidths achievable with optical antennas having diameters of less than 30 cm. This paper discusses how the Gaussian beam patterns of the laser sources are modified as they are transmitted through physically realizable optical antennas. Measurements taken on an optical antenna developed for spaceborne operation are presented and compared with theoretical predictions. Optical receiver antennas are also discussed stressing the differences between direct and heterodyne detection. Finally, consideration is given to the privacy and jamming resistance of optical communication systems using these small optical antennas.
    • Air Force Space Laser Communications

      Roland, Jay R.; Whited, Charles E.; Los Angeles Air Force Station (International Foundation for Telemetering, 1978-11)
      The Air Force Space Laser Communications (LASERCOM) Program started with system concept and component design in the early 1970's at the Air Force Avionics Laboratory. The communications system that evolved demonstrated, in 1973, data rates up to one gigabit per second with a bit error rate of 10⁻⁶ for 40,000 kilometer simulated links. System capabilities were demonstrated during the period 1975 to present using an engineering feasibility model of a gigabit-per-second space qualifiable transmitter and a brassboard receiver. The next phase of the program started in September of this year when the LASERCOM system began operation outside of the laboratory environment at the White Sands Missile Range in New Mexico. This six-phase demonstration will include ground-to-ground links up to approximately 20 kilometers and aircraft-to-ground links up to approximately 50 kilometers. During these demonstrations, dynamic far-field acquisition, tracking, and two-way communications will be demonstrated. The performance characteristics of the LASERCOM system make its potential application to certain satellite-satellite and satellite-aircraft links unique, while other potential LASERCOM links require a detailed cost analysis of the current investment in radio frequency terminals and systems versus the cost of developing and deploying LASERCOM terminals and systems. There are also some communications links that can be most effectively satisfied by a hybrid LASERCOM and radio frequency system.
    • 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.