• Computer Image Manipulation for Restoration and Enhancement

      Andrews, H. C.; University of Southern California (International Foundation for Telemetering, 1971-09)
      This paper briefly outlines a few ideas involved in the use of the versatility of high speed digital computers for natural photographic quality image restoration and enhancement. The subject of image digitization is briefly mentioned followed by three models for image restoration. The linear shift invariant (isoplanatic) model relies on a rich body of knowledge in the form of two dimensional linear systems theory. While the linear isoplanatic model is useful for a variety of degradating phenomena, the linear anisoplanatic and nonlinear models often provide further insight into specialized phenomena. Image restoration may often be followed by enhancement techniques which focus on image manipulations for presentation purposes. The psychophysics of vision play a major role in the development of this aspect as do heuristic techniques which tend to focus on known but often unexplainable human viewing responses. Examples from certain nonlinear enhancement processes are presented.
    • Error Bounds in Coherent Digital Systems

      Prabhu, V. K. (International Foundation for Telemetering, 1971-09)
      We present simple upper and lower bounds to the distribution function of the sum of two random variables in terms of the marginal distribution functions of the variables. These bounds are then used to obtain upper and lower bounds to the error probability of a coherent digital system in the presence of intersymbol interference and additive gaussian noise. The bounds are expressed in terms of the error probability obtained with a finite pulse train, and the bounds to the marginal distribution function of the residual pulse train. Since the difference between the upper and lower bounds can be shown to be monotonically decreasing function of the number of pulses in the finite pulse train, the bounds can be used to compute the error probability of the system with arbitrarily small error.
    • Comparison of Phase Tracking Schemes for PSK

      Cahn, Charles R.; Magnavox Research Laboratories (International Foundation for Telemetering, 1971-09)
      Based on straightforward approximations to evaluate the error rate with phase jitter in the reconstituted carrier and phase slips in the tracking loop, comparison is made of three schemes for biphase and quadriphase data transmission: 1. Track phase on carrier component, 2. Track on suppressed carrier - use differentially encoded PSK, 3. Track on suppressed carrier - retain a carrier component to resolve the inherent ambiguity. For operation at relatively high P(E), as with error correction, schemes 1 and 3 both avoid the inherent degradation of differential encoding; however, both require a relatively narrow band phase tracking loop. Scheme 3, suppressed carrier tracking with ambiguity resolution, achieves the minimum E(b)/N(o) degradation at high P(E) when the loop bandwidth parameter is held fixed by system requirements.
    • International Telemetering Conference Proceedings, Volume 07 (1971)

      International Foundation for Telemetering, 1971-09
    • Radiotelemetric Cardiorespiratory Determinations During Submaximal Dynamic Exercise

      Crane, Robert; Steen, Stephen N.; C.B.M.L.; U.C.L.A. (International Foundation for Telemetering, 1971-09)
      Under normal conditions, healthy people at submaximal exercise show a close correlation between work load and cardiac output (i.e. oxygen uptake versus heart rate, respectively). Subjects with chronic bronchospastic disease respond to specific bronchodilators(e.g. isoproterenol) with increases in heart rate -- even without exercise. New bronchodilators (salbutamol) which do not exert such an influence on the heart rate are being studied for their effect on "exercise induced asthma." Measurements of airway resistance(R(A)) and thoracic gas volume (V(tg)) during dynamic exercise (treadmill) pose complex instrumentation problems. The radiotelemetric determinations of specific airway conductance (G(A)/V(tg) where G(A) = 1/R(A)) now appear practicable. The acquisition of such data in conjunction with other radiotelemetered measurements (heart rate from R-R interval) indicate that patients with chronic bronchspastic disease, when treated with bronchodilators, may tolerate physical exercise more safely.
    • Bias and Spread in EVT Performance Tests

      Smith, Joel G.; California Institute of Technology (International Foundation for Telemetering, 1971-09)
      Performance tests (measurements of probability of error) of communication systems characterized by low bit rates and high reliability requirements frequently utilize classical extreme value theory(EVT) to avoid the excessive test times required by bit error rate (BER) tests. If the underlying noise is gaussian or perturbed-gaussian, the EVT error estimates have either excessive bias or excessive variance if an insufficient number of test samples is used. EVT is examined to explain the cause of this bias and spread; experimental verification is made by testing a known gaussian source, and procedures that minimize these effects are described. Even under these conditions, EVT test results are not particularly better than those of BER.
    • Digital Transmission Over the RC Channel

      Hoffman, E.; Bell Telephone Laboratories (International Foundation for Telemetering, 1971-09)
      This work evaluates the performance of digital transmission links over a lumped RC channel when one of three static equalization schemes is utilized: 1. Use of a Sidelobe Transmitter 2. Transversal Filter at the Receiver 3. Frequency Compensation of the Transfer Characteristics to form a rectangular Nyquist Channel. The effect on the probability of error of thermal noise and intersymbol interference is considered. In each of the equalization schemes, the intersymbol interference is reduced to zero, and the waveshape at the transmitter which maximizes the SNR at the receiver decision instant is transmitted. It is found that the performance of the Sidelobe Transmitter and the Transversal Filter Receiver are equal theoretically and that Frequency Compensation provides the poorest results. The comparisons carried out in this work have utilized the RC channel as an example. Detailed generalization of the comparative performance as a function of the impulse response of the channel utilized would be desirable but cannot be made readily. An analysis of the coaxial line is planned for the future. The eigenfunctions and corresponding eigenvalues of the system are required in order to evaluate the optimal performance of the Sidelobe Transmitter and Transversal Filter Receiver. For arbitrary impulse responses, these eigenfunctions are usually complex to obtain. However, one is able to state in general that since the Sidelobe Transmitter or Transversal Filter combined with transmission of the optimum waveshape represent the best linear filter, their performance will not be inferior to the Frequency Compensated rectangular Nyquist channel. This follows since frequency compensation networks fall into the class of linear filters.
    • Operational Processing of ITOS Scanning Radiometer Data

      Bristor, C. L.; Leese, J. A.; National Oceanic and Atmospheric Administration (International Foundation for Telemetering, 1971-09)
      The Improved TIROS Operational Satellite (ITOS) System uses a spacecraft in a sun-synchronous (1500L) polar orbit. A two-channel scanning radiometer on the spacecraft provides information in the .52- to .73- micrometer visible range and the 10.5- to 12.5- micrometer infrared water vapor window. Operational processing of the scanning radiometer data leads to mapped products and derived products. In the former the image data are transformed to fit a common type of map projection such as polar stereographic or mercator. Derived products are the measurements and interpretive type products obtained from the gridded or mapped imagery. Automated procedures are being developed to derive quantitative information from mapped image data. Parameters sought include the sea-surface temperature and cloud top temperature which can be converted to height. Procedures are also being developed which combine the data from the two channels to derive quantitative information.
    • On the Timing Problem in Optical PPM Communications

      Gagliardi, R. M.; University of Southern California (International Foundation for Telemetering, 1971-09)
      The use of digital transmission with narrow light pulses appears attractive for data communications, but carries with it a stringent requirement on system bit timing. In this paper we investigate the effects of imperfect timing in a direct detection (noncoherent) optical system using PPM bits. Particular emphasis is placed on specification of timing accuracy, and an examination of system degradation when this accuracy is not attained. Bit error probabilities are shown as a function of timing errors, from which average error probabilities can be computed for specific synchronization methods. Of significant importance is the presence of a residual, or irreducible error probability, due entirely to the timing system, that cannot be overcome by the data channel.
    • A Versatile Memory Controlled PCM Encoder for Adaptive Telemetry Systems

      Johnson, C. S.; Sandia Laboratories (International Foundation for Telemetering, 1971-09)
      An Adaptive Telemetry System is defined as a flexible, controllable pulse code modulation (PCM) telemetry system which offers many options and many modes of operation prior to and during actual test of a monitored system. The concept of having a telemetry system adapt to the data and circumstances of the test is not new. Large data-gathering systems using computers for control have pioneered this concept. However, the present development activity has centered on a small aerospace memory controlled PCM encoder which can function as the keystone of an adaptive telemetry system. The encoder can be used by itself as a general-purpose airborne encoder.
    • Notch Noise Loading Date on Pre-Detection Recording of FM Carriers

      Hedeman, W. R., Jr.; Nichols, M. H.; Aerospace Corporation (International Foundation for Telemetering, 1971-09)
      In a previous paper (1) the authors reported notch noise loading tests of baseband (post-detection) tape recording showing dependency of the notch noise power ratio, NPR, on record level. The purpose of this paper is to report notch noise loading tests on pre-detection tape recording showing NPR dependence on record level, bias level, and output equalization. Both the baseband and pre-detection recording tests were made with the Hewlett-Packard Model 3950 recorder/reproducer. Generally, the pre-detection NPR were 5db or more improved over the baseband NPR. The extent of the improvement depends, in part, on the quality of the vco and discriminators utilized for the pre-detection recording as well as the carrier deviation. As the linearity of the vco and discriminator and the phase linearity of the circuits that pass the pre-detection signal are improved, the limiting factor in NPR is the noise added by the reproduce amplifier. Increasing the record level above IRIG standard produces an improvement in the output signal-to-noise ratio, NPRO, of 3 to 5 db using IRIG standard bias. Eliminating the bias and recording at the level which results in maximum output of the fundamental produced up to 8 db improvement in NPRO over IRIG. In the course of the tests it was discovered that if harmonics are present in the recorded pre-detection signal and/or are generated in the record/reproduce process, serious intermodulation can occur unless a low-pass filter ahead of the discriminator is used.
    • Two-Way Coherent Tracking Systems

      Lindsey, William C.; Yuen, Joseph H. (International Foundation for Telemetering, 1971-09)
      This paper presents results pertinent to the development of nonlinear theory of two-way tracking system. In particular, the model of cascaded systems is presented and approximations to steady state probability density functions (p.d.f.'s) of the two-way system phase and Doppler error are given. From these certain numerical results required in the design and planning of systems are given.
    • Implementation of Maximum Likelihood Decoders for Convolutional Codes

      Clark, George C., Jr.; Radiation Incorporated (International Foundation for Telemetering, 1971-09)
      Maximum likelihood decoding of convolutional codes is finding considerable application in communication systems and several decoders of this type have recently been built. These decoders implement an evolved form of a decoding procedure that was originally described by Viterbi in 1967. In this document we describe the problems of reducing the Viterbi algorithm to hardware, the various tradeoffs and compromises that must be made, and the short cuts that are available. In addition an interesting variation on the Viterbi algorithm is described which results in favorable implementation particularly at high data rates.
    • Space Station Communications Using Interplex Modulation

      Butman, S.; Lafrieda, J.; Timor, U. (International Foundation for Telemetering, 1971-09)
      This paper describes a new PSK/PM modulation scheme, called interplex, which reduces cross-modulation loss. The scheme can be implemented without significant hardware changes in existing systems, and can be incorporated into the Space Station Telecommunications system.
    • High Data Rate Coding for the Space Station Telemetry Links

      Lumb, D. R.; Viterbi, A. J.; NASA; Linkabit Corp. (International Foundation for Telemetering, 1971-09)
      This paper summarizes a study of coding systems for high data rates with potential application to the space station telemetry links. Among the approaches considered were convolutional codes with sequential, Viterbi and cascaded Viterbi decoding. It was concluded that a high-speed (.40 Mbps) sequential decoding system best satisfies the requirements for the assumed growth potential and specified constraints. Trade-off studies leading to this conclusion will be reviewed. Some sequential (Fano) algorithm improvements will be discussed as well as real-time simulation results.
    • Investigation of a PAM Tester Using PN Waveforms

      McClellan, Wade C.; Nicholas, M. H.; White Sands Missile Range; Duke University (International Foundation for Telemetering, 1971-09)
      A PAM tester using a shift register generated sequence and a conventional data (PCM) bit synchronizer and detector for synchronization was investigated. It was found to function satisfactorily with and without predetection tape recording. This tester can be implemented by adding digital-to-analog converters (DAC's), an error gate, and a rms voltmeter to a PN PCM tester which uses a shift register to generate the PN sequence.
    • Remote Monitoring of Intracranial Pressure

      Deutsch, Sid; Neidinger, Joseph W.; Cook, Albert W.; Polytechnic Institute of Brooklyn; PLB; Long College Hospital; S.U.N.Y. (International Foundation for Telemetering, 1971-09)
      During various pathological states, it is important for the neurosurgeon to know the magnitude of intracranial pressure. It is desirable to have a device small enough to be implanted and left in a trephine hole on a chronic basis, with associated circuitry that would lie beneath the skin surface. An appropriate device is described. The heart of the device is a strain gage bridge that is used to sense differential pressure. The bridge is driven by a 5kHz astable multivibrator, and bridge unbalance frequency-modulates a 100kIlz oscillator. The latter signal is telemetered through the skin via a double-tuned transformer. Power to drive the implant is fed in through a second transformer at 2MHz.
    • Biomedical Telemetry - A Review and Overview

      Caceres, C. A.; Slater, L. E. (International Foundation for Telemetering, 1971-09)
      Biomedical telemetry has yet to fulfill the high promise generated by its first significant use ten years ago. Most of the progress has been in research biotelemetry; in the monitoring of animal physiology and behavior to gain new insight into both the normal and pathological state. Many clinical applications have developed but few, with the notable exceptions of telephone telemetry systems in cardiology and the monitoring of astronauts, have achieved wide acceptance. The nub of the problem has been the bias in equipment design and system orientation towards research criteria. There is a compelling need and opportunity for telemetric systems specifically designed for clinical, or on-the-spot, use.
    • A Real Time Programmable Data Compression System for Video Data

      Kutz, R. L.; Davisson, L. D.; NASA Goddard Spaceflight Center; University of Southern California (International Foundation for Telemetering, 1971-09)
      This paper describes the implementation of a data compression system for the real time operational transmission of advanced technology satellite (ATS) pictures between the command and data acquisition (CDA) station located at Wallops Island, Virginia and the National Environmental Satellite Service (NESS) at Suitland, Maryland over broadband microwave links. The system features the use of general purpose minicomputers for encoding and decoding which makes it possible to easily vary the data compression technique in use and to make simultaneous statistical calculations on the data. Special interfaces to the pre-existing equipment have been designed to insure efficient use of the parallel structure of the computers. Data compression and expansion is done in a way that results in no lowering of data quality.
    • Frame Synchronization in PCM Telemetry

      Peavey, Bernard; NASA-Goddard Space Flight Center (International Foundation for Telemetering, 1971-09)
      Frame synchronization of PCM telemetry data can be accomplished very effectively by employing the fixed threshold method with a unique strategy. Probability of false sync acquisition and maintenance can be made negligibly small for data having bit error rates less than 10%, at a small sacrifice in acquisition time. Furthermore, experimental results indicate that frame synchronization is significantly affected by the frame sync code length rather than by the code pattern itself, i.e., any pseudo-random code is just as good. The difference in performance between "optimum" codes and any pseudo-random code is negligible.