• 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.
    • Soft Decision Decoding of Block Codes

      Baumert, L. D.; McEliece, R. J.; California Institute of Technology (International Foundation for Telemetering, 1978-11)
      Using a general decoding technique of Solomon we evaluate the performance of certain block codes on a gaussian channel. Quadratic residue codes of lengths 48 and 80 as well as BCH codes of length 128 and rates 1/2 and 1/3 are considered. All four of these codes perform quite favorably with respect to the constraint-length 7 rate 1/2 convolutional code presently used on NASA's Mariner-class spacecraft.
    • The Impact of LSI on Telemetry Systems

      Finn, W. J.; Karwoski, R. J.; TRW LSI Products (International Foundation for Telemetering, 1978-11)
      Any system which measures, transmits over a distance, receives, and processes signals can be defined as a telemetry system. Video transmission systems, satellite communications systems wideband data links, and TDM/FDM transmultiplexers all have one thing in common: an increasing need for high-speed digital signal processing. This paper is intended to serve as an introduction to the application of LSI to telemetric signal processors.
    • Summary of Enhanced NRZ Code Properties

      Fairfield, Anthony G.; Schulze, Glen H.; Bell & Howell (International Foundation for Telemetering, 1978-11)
      A summary of the properties of Enhanced NRZ (ENRZ) for magnetic tape recording is presented. Major code properties are defined and, where informative, compared with competing recording codes. Considerable insight is given into the considerations for maximizing the recording density without abusing the limited bandwidth of the tape recording channel. Several standard configurations with multi-track deskewed formats currently in field use are presented with throughput rates up to 320 MBPS. Error-detection and correction for improving Bit Error Rates of inferior tapes to 10⁻¹⁰ is outlined.
    • An Efficient Multichannel FFT Demodulator

      von der Embse, U. A.; Austin, M. C.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      A multichannel binary FSK demodulator for spaceborne application has been implemented using an efficient preweighted and thinned fast Fourier transform (FFT) algorithm. Theory, configuration, and performance are described and compared with the analog unit which performs the same functions. Being able to perform the first base 16 pass with add-only operations following preweighting, provided the complexity reduction which made it feasible to use the FFT to perform the channelization and predetection filtering.
    • Performance Evaluation for Shuttle/TDRSS Links Using Analytical Simulation

      Lindsey, William C.; Braun, Walter R.; LinCom Corporation (International Foundation for Telemetering, 1978-11)
      An analytical simulation package has been developed by LinCom Corporation for analytical verification of bit error rate and tracking services performance for both S- and K-band Shuttle user service through the Tracking and Data Relay Satellite System (TDRSS). The purpose of this effort was to provide a tool to assess overall system performance as well as the sensitivity to key subsystem parameters and to ensure compatibility of TDRSS and Shuttle transponder performance specifications. The evaluation is based on analytical simulation, i.e., a combination of simulation techniques and analytical performance evaluation. This allows the use of a more realistic signal format than is possible with a purely analytical approach and maintains the advantage of short computation time. The Shuttle forward and return link models and the main features of the simulation are described. Sample results of the computer runs are provided for current power budgets and system design parameters.
    • Step-By-Step Decoding of Alternant Codes

      Omidyar, C. G.; Helgert, H. J.; The George Washington University (International Foundation for Telemetering, 1978-11)
      In this paper we present a decoding scheme for Alternant codes. The syndromes are calculated from the received vector and the parity check matrix H. Let t be the error correcting capability of the decoder. Then we determine a Key Equation by adding t columns of the parity check matrix H. We raise this equation t-1 times to the power of n, where n is the number of columns of H. Next we consider a matrix At whose elements are the set of coefficients from the Key Equations which we obtained. We make a decision based on the determinant of the matrix A(t). If the matrix A(t) is singular, then we test the matrix A(t-1) for singularity and continue up to A(t-t+1) which in fact the decoder can correct one error. if any one of the matrices A(t) through A(t-t+1) is nonsingular we change the first digit of the received vector, then recompute the syndromes and recheck Δt'. If Δt' is zero the change is retained. If not, the digit is changed again. The Algorithm then proceeds to the next digit. This Algorithm for decoding Alternant codes has significant improvements over previous schemes since the step-by-step decoding can be carried out at selected areas of the received word.
    • Space Shuttle Orbiter Processing, Monitoring, and Telemetry Systems

      Carrier, Louis M.; Robitaille, Richard A.; Rockwell International (International Foundation for Telemetering, 1978-11)
      The transportation vehicle for launching personnel and payloads into earth orbit during the 1980's and subsequent years will be NASA's space shuttle. The space shuttle flight system consists of an orbiter, an external tank, and two solid rocket boosters. The orbiter, a key element of the Space Shuttle, is launched into space like a conventional launch vehicle, performs on-orbit payload missions, enters the atmosphere, and lands much like a conventional commercial jet aircraft. This paper provides an overview of the Space Shuttle avionics with prime emphasis on how the orbiter's on-board processing, monitoring, and telemetry systems function during the on-orbit mission phase. Included is a description of the S-band and Ku-band RF transmission link and its relationship to the ground systems, payload interfaces, and support equipment. Also discussed are the flexibility of its instrumentation system (including capability to provide formats), features of the on-board monitoring systems (dedicated displays, cathode-ray tubes, and caution and warning systems), and methods for storing and processing data (recorders, mass memory, and on-board computers). The orbiter's avionic services to the payloads and the future growth of the Space Transportation System and the orbiter are also discussed briefly.
    • Satellite Communication Simulation and Its Applications

      Wang, Lily L.; Yeh, Paul P.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      The computer simulation activities which have been carried out at The Aerospace Corporation for satellite link performance studies and system analysis are reported. A brief description of the modelings of a filter, nonlinear device, modulator, detector and receiver is also given. Some results from the simulation studies, such as the basic link performance in the presence of filters and nonlinear device (hard limiter or TWT), the comparisons of various modulation techniques (OK-QPSK, MSK and PFQPSK), the study of cross talk in a FDMA system, the interference or jamming at the presence of a nearby source, and finally, the intermodulation problem of a multiple channel MFSK system using the frequency hopping, are addressed.
    • A Flexible User Oriented Approach to Communications Systems Simulation

      Fashano, M.; Austin, M. C.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      An advanced software/hardware computer system developed for the simulation of communications systems is described. This user oriented system allows for flexible and efficient modeling and simulation of complex communications systems. Excellent agreement between simulation and measured results has consistently valididated the simulation approach.
    • Performance of Bandlimited and Hardlimited PSK Signals

      Rey, R. D.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1978-11)
      Transmission of a signal through a channel, such as a satellite communication channel, results in distortion of the signal due to bandlimiting in the individual channels and hardlimiting. The purpose of this paper is to study the effects that channel distortion due to filtering and hardlimiting have on the performance of BPSK and QPSK. The results will be used to determine the maximum bit rate which can be transmitted through a channel having a particular bandwidth with a specified limit in degradation of performance.
    • Performance Evaluation of Communication Channels by Computer Simulation

      Poza, H. B.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1978-11)
      A computer simulation model capable of aiding in the design and predicting the performance of complex end-to-end communication systems is described in this paper. The model is used to choose the optimal modulation scheme under certain communication channel constraints, define the signal distortion characteristics introduced by realizable channel components and select the demodulator/bit synchronizer designs for minimization of bit error rate. A parameter sensitivity analysis is conducted to demonstrate the usefulness of the model in evaluating the effect of different signal distortion phenomena on overall link performance.
    • A Fast Complex Integer Convolution Using a Hybrid Transform

      Reed, I. S.; Truong, T. K.; University of Southern California; California Institute of Technology (International Foundation for Telemetering, 1978-11)
      In this paper it is shown that the cyclic convolution of complex values can be performed by a hybrid transform. This transform is a combination of a Winograd transform, and a fast complex integer transform developed previously by the authors. This new hybrid algorithm requires fewer multiplications than any previously known algorithm.
    • Subcarrier Phase Recovery Performance in Bent-Pipe Mode of Shuttle Data Transmission

      McKenzie, Teresa M.; Braun, W. R.; LinCom Corporation (International Foundation for Telemetering, 1978-11)
      The subcarrier phase recovery is analyzed for the bent-pipe mode of Space Shuttle detached-payload data transmission on the Tracking and Data Relay Satellite System (TDRSS) Ku-band return link. The high-power component of the subcarrier modulation is unrestored payload data, either at baseband or modulating another subcarrier. At the receiver a Costas loop recovers the subcarrier phase. To analyze its performance in the baseband case, we obtain the loop S-curve, the power spectral density of the equivalent noise process, and the loop phase error variance.
    • Future Automated Spacecraft as an End-to-End System Element

      Bird, Thomas H.; NASA - Jet Propulsion Laboratory (International Foundation for Telemetering, 1978-11)
      Concepts for a highly automated spacecraft, which is much more independent of ground operations than current spacecraft, have been investigated. Applicable systems and technology requirements are identified for maximum onboard automation of mission functions. A spacecraft concept which requires infrequent ground contact while increasing mission effectiveness is described. The potential impact of such a system on end-to-end system design is discussed.
    • A Microprocessor Controlled Antenna Pointing Unit

      Kasser, J. E.; COMSAT Laboratories (International Foundation for Telemetering, 1978-11)
      Two prototype antenna pointing units (APUs) for controlling different antennas tracking geostationary satellites have been built using an 8080 microprocessor. The use of the microprocessor has allowed the same basic hardware to control two separate and different parabolic dish antennas with minimal circuitry changes and has provided significant flexibility in the performance of the units. This paper describes the APU design, which optimizes hardware and software to provide the flexibility necessary during initial testing and subsequent operation of the prototypes.
    • TIPS Real Time Acquisition, Processing and Display Subsystem

      Straehley, Erwin H.; Straehley Associates (International Foundation for Telemetering, 1978-11)
      The requirement to acquire, process, and display telemetry data from increasingly sophisticated test vehicles in real time is one of the, principal parameters that shaped the SAMTEC Telemetry Integrated Processing System (TIPS) design. An integrated subsystem incorporating advances in hardware design, linked by a multi-processor software element implementing three distinct processing functions to fill this requirement, is described in this paper. Most of the hardware elements, except the processor, were designed to meet the specific requirements of this system. This includes telemetry front-end acquisition equipment, electrostatic high speed printer plotters, plasma keyboard displays, and wide band links to transfer data from element to element. The processors are 32-bit word third generation midi-computers. Each element was selected or specified primarily for its ability to perform at the expected incoming data rates. The Real Time Acquisition (RTA) Software is partitioned into an executive function, an acquisition and event processing function, and a display processing function. Each function resides in its own specific computer configuration. The acquisition configuration (TPP) and display configuration (QLDA) are each replicated to provide multi-input stream and multiple independent display capabilities. Real time requirements, similar to those at SAMTEC, are evolving elsewhere. The hardware and software components described herein are easily adaptable to satisfy these requirements at a variety of other advanced telemetry data processing facilities.
    • TIPS - An Integrated Solution for Multi-Mission Telemetry

      Van Dolsen, L. L.; System Development Corporation (International Foundation for Telemetering, 1978-11)
      The Air Force Space and Missile Test Center (SAMTEC) must provide concurrent support for a variety of missions requiring real time telemetry data acquisition and processing. An integrated system is presently going operational to replace seven individual complexes presently supporting these missions. The Telemetry Integrated Processing System (TIPS) includes six real-time input streams, a large-scale near-real-time processor, and six interactive display areas. The TIPS facilitates rapid reconfiguration to meet changing operational needs or to continue operation in the face of equipment failures. The cost and lead time required for support of new requirements and also operation and maintenance costs will be substantially reduced. TIPS is the first Air Force data system processed under the Design-to-Cost/Life Cycle Cost (DTC/LCC) philosophy; all design and specification changes are evaluated in terms of operational as well as initial costs. Notable achievements in the TIPS implementation are the Telemetry Compiler and the real-time acquisition and processing subsystems which are described in accompanying papers.
    • Phase Referencing for MA Demultiplexing in the TDRSS

      Gagliardi, R. M.; University of Southern California (International Foundation for Telemetering, 1978-11)
      The TDRSS performance is based, to a large extent, on the ability to maintain phase coherency between user, satellite, and ground segment. This is especially true for the MA return subsystem, which uses coherent referencing for multiplexing and demultiplexing between the TDRS and ground processor. Phase noise appearing on these referencing waveforms destroy the phase coherency, and will degrade the overall MA return operation. In this paper the manner in which this phase referencing is achieved is described. In addition, the results of a preliminary study to distinguish the key MA return phase noise sources, and the manner in which each will ultimately influence performance, is presented. The results show that the return phase noise effects can be separated into "coherent" and "noncoherent" contributions, and each must be separately evaluated. The effect of the various tracking loop bandwidths throughout the link is shown, and the manner in which the specific phase noise spectra are eventually filtered is developed.
    • Status Report on TDRSS

      Holmes, W. Morris, Jr.; TRW Inc. (International Foundation for Telemetering, 1978-11)
      The NASA Satellite Tracking and Data Network (STDN) will be replaced by the Tracking and Data Relay Satellite System (TDRSS) during the 19801's. The coverage available to user satellites will be increased dramatically and very high data rates will be provided. Real-time data analysis and adaptive satellite control will be possible with the availability of continuous two-way communications. TDRSS will provide these benefits while lowering the cost of tracking and communicating with NASA satellites. Communication requirements will be different for satellite designers in the 1980 period. TDRSS user satellites will require higher transmitter power and more sensitive receivers, and will communicate using special TDRSS modulation formats. There will be less onboard data storage. This paper provides an overview of the TDRSS as it is being built. The major system features are described, and some of the system characteristics that will affect user satellite mission planning are considered.