Decoding binary block codes on Q-ary output channels
Error correcting binary block code decoding on Q-ary output channels /weighted erasure decoding/, considering applications
Weldon, E. J., Jr.↗
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Burst decoding of binary block codes on Q-ary output channels.
The burst-b distance between two binary vectors is defined and shown to be a metric. This definition is applied to a binary-input, Q-ary output channel where errors occur in bursts. A decoding algorithm is presented for such a channel that is an extension of Weldon's (1971) weighted erasure decoding. Examples are presented illustrating the techniques.
Wainberg, S.↗
M-ary Laguerre detection.
In a communication system using optical devices, the receiver is modeled as a counter of electrons which are emitted from a photodetector when a modulated optical wave is incident on it. The synthesis of the optimal receiver processing and its resulting performance depend upon the statistics associated with this counting. In an M-ary system, the transmitter selects one of a set of M intensities for the optical process. Questions of error probability are investigated.
Mohanty, N. C.↗
Recursive ideal observer detection of known M-ary signals in multiplicative and additive Gaussian noise.
This paper presents the derivation of the recursive algorithms necessary for real-time digital detection of M-ary known signals that are subject to independent multiplicative and additive Gaussian noises. The motivating application is minimum probability of error detection of digital data-link messages aboard civil aircraft in the earth reflection multipath environment. For each known signal, the detector contains one Kalman filter and one probability computer. The filters estimate the multipath disturbance. The estimates and the received signal drive the probability computers. Outputs of all the computers are compared in amplitude to give the signal decision. The practicality and usefulness of the detector are extensively discussed.
Painter, J. H.↗
M-ary shift register
Binary devices are used to construct an m-ary linear feedback shift register.
Perlman, M.↗
The use of TWT amplifiers in M-ary amplitude and phase shift keying systems
A great deal of research is presently being conducted to study modulation schemes in order to reduce the bandwidth of digital communications. These M-ary amplitude and phase shift keying (MAPSK) modulation systems place new requirements on TWT amplifiers in space applications in that the various signal sets usually include two or more discrete output power levels as well as discrete phases at each power level. This paper presents a variety of predistortion schemes to circumvent the TWT problems of AM distortion and AM-to-PM conversion in order to produce MAPSK signal sets. A feedback scheme is presented to correct for long-term phase and amplitude drifts in the transmitter. A complete transmitter is proposed using predistortion to produce the desired MAPSK signal set at very high data rates including the possible use of a feedback stabilization scheme.
Weber, W. J., III↗
The Aries Program with emphasis on the International Magnetospherics Studies /IMS/-Porcupine Project
This paper will discuss the present state of the development of the Aries Sounding Rocket System with particular emphasis on the configuration and subsystems required to support the IMS Program. A brief history of the development program will be presented. The results of the first five flights, three successes and two failures, will be presented and the observed performance compared to theoretical performance.
Honecker, H. J.↗
Development of Alabama Resources Information System (ARIS)
A formal, organized set of information concerning the development status of the Alabama Resources Information System (ARIS) as of September 1976 is provided. A series of computer source language programs, and flow charts related to each of the computer programs to provide greater ease in performing future change are presented. Listings of the variable names, and their meanings, used in the various source code programs, and copies of the various user manuals which were prepared through this time are given.
Herring, B. E.↗
Development of the Aries parachute system
The design and testing of a two-stage parachute system to recover a space telescope weighing up to 2200 pounds is described. The system consists of a 15-ft diameter ribbon parachute reefed to 50 percent for 10 seconds and a 73-ft diameter paraform or cross second stage reefed to 20 percent for 10 seconds. The results of ten drop tests and two operational rocket launched flights are presented. Two successful operational recoveries of 1600-lb and 2050-lb NASA space telescopes were conducted at White Sands Missile Range, NM. The payloads are launched by ARIES rockets to altitudes of about 194 and 163 miles above sea level.
Pepper, W. B.↗
The performance of M-ary FH-DPSK in the presence of partial-band multitone jamming
Using a geometric approach, the performance of M-ary FH-DPSK in the presence of partial-band multitone jamming is evaluated. The optimal jamming strategy is determined as a function of the number of signaling levels M and the ensuing results are used to determine worst case bit error probability performance as a function of this same parameter. It is demonstrated that, for M = 2 to the m power (where m is an integer), the best performance is obtained for M = 4.
Simon, M. K.↗
A near-optimum receiver structure for the detection of M-ary optical PPM signals
A class of receivers called conditionally nulling receivers is defined for quantum noise limited optical communications. These receivers have the ability to decide at each moment in time whether or not to coherently combine a predetermined local oscillator field with the received optical field, prior to performing an energy measurement (photodetection) on the combined field. Conditionally nulling receivers are applicable to pulse position modulation and related modulation schemes, which have the property that, at each moment in time, the transmitted signal is in one of only two states, on or off. The local oscillator field which may or may not be added by the receiver is an exact replica of the negative of the received on field; hence, the receiver can exactly null the on signal if the on signal is present and the receiver chooses to use the local field. An ideal conditionally nulling receiver achieves very nearly the same error probability (within a multiplicative factor varying froom 1 to 2.15) as the optimum quantum measurement for quantum noise limited detection of M-ary PPM signals. In contrast, other known receiving methods, such as direct, heterodyne, and homodyne detection, are exponentially suboptimum.
Dolinar, S. J., Jr.↗
Analysis of a Coded, M-ary Orthogonal Input Optical Channel with Random-gain Photomultiplier Detection
Performance of two coding systems is analyzed for a noisy optical channel with M(=2(L)-ary orthogonal signaling and random gain photomultiplier detection. The considered coding systems are the Reed Solomon (RS) coding with error only correction decoding and the interleaved binary convolutional system with soft decision Viterbi decoding. The required average number of received signal photons per information bit, N sub b, for a desired bit error of 0.000001 is found for a set of commonly used parameters and with a high background noise level. We find that the interleaved binary convolutional coding system is preferable to the RS coding system in performance complexity tradeoffs.
Lee, P. J.↗
Bandwidth efficient block codes for M-ary PSK modulation
A class of bandwidth efficient block codes for M-ary PSK modulation is presented. A soft-decision decoding for this class of codes is devised. Some specific short codes for Quad Phase Shift Key (QPSK), 8-PSK and 16-PSK modulations are constructed. These codes have good minimum squared Euclidean distances and provide 2 to 5.8 dB coding gains over uncoded QPSK modulation without (or with little) bandwidth expansion. The complete weight distributions of these specific codes are determined. Based on these weight distributions, their error probabilities are evaluated. Some of these codes have simple trellis structures and hence can be decoded by Viterbi decoding algorithm with relatively simple implementation. Moreover, the codes are very suitable for use as inner codes for various cascaded coding schemes with Reed-Solomon codes as outer codes.
Lin, Shu↗
Direct detection optical intersatellite link at 220 Mbps using AlGaAs laser diode and silicon APD with 4-ary PPM signaling
A newly developed 220 Mbps free-space 4-ary pulse position modulation (PPM) direct detection optical communication system is described. High speed GaAs integrated circuits were used to construct the PPM encoder and receiver electronic circuits. Both PPM slot and word timing recovery were provided in the PPM receiver. The optical transmitter consisted of an AlGaAs laser diode (Mitsubishi ML5702A, lambda=821nm) and a high speed driver unit. The photodetector consisted of a silicon avalanche photodiode (APD) (RCA30902S) preceded by an optical interference filter (delta lambda=10nm). Preliminary tests showed that the self-synchronized PPM receiver could achieve a receiver bit error rate of less than 10(exp -6) at 25 nW average received optical signal power or 360 photons per transmitted information bit. The relatively poor receiver sensitivity was believed to be caused by the insufficient electronic bandwidth of the APD preamplifier and the poor linearity of the preamplifier high frequency response.
Sun, Xiaoli↗
Reduced electrical bandwidth receivers for direct detection 4-ary PPM optical communication intersatellite links
This interim progress report consists of copies of three reports written for NASA's Flight System Development and Demonstration (FSDD) project on optical intersatellite links. The first report, 'Test results of the PlessCor avalanche photodiode (APD) preamplifier for use in the 50 Mbps quaternary pulse position modulator (QPPM) receiver,' was prepared for NASA Goddard Space Flight Center. The second, 'Performance of Q-ary PPM receiver under additive white Gaussian noise,' was prepared at the request of NASA Lewis Research Center for testing the electronic systems for the FSDD project. The third, 'Use of a Bessel lowpass filter as an approximate raised cosine filter,' was written for raised cosine filter implementation in the FSDD QPPM receiver.
Davidson, Frederic M.↗
Aries x ray objective grating spectrograph
This investigation was initiated in June of 1983. An Aries payload involving a single Wolter 1 telescope was developed and flown under a previous contract and the objective of this work was to add two additional mirrors, nested inside of the then existing mirror and add 12 objective reflection gratings to convert the telescope into a spectrograph. A summary of major milestones in the investigation are given. Results of efforts under this contract prior to 1987 are presented in the form of four reprints of published papers attached to this report. Results of the gamma-ray research are also included in the form of an attached reprint. A summary of other work under the contract since 1987 is given.
Catura, R. C.↗
Synchronization techniques for all digital 16-ary QAM receivers operating over land mobile satellite links
The performance of a low bit rate (64 Kb/s) all digital 16-ary Differentially Encoded Quadrature Amplitude Modulation (16-DEQAM) demodulator operating over a mobile satellite channel, is considered. The synchronization and detection techniques employed to overcome the Rician channel impairments, are described. The acquisition and steady state performance of this modem, are evaluated by computer simulation over AWGN and RICIAN channels. The results verify the suitability of the 16-DEQAM transmission over slowly faded and/or mildly faded channels.
Fines, P.↗
The Aries auroral modelling campaign - Characterization and modelling of an evening auroral arc observed from a rocket and a ground-based line of meridian scanners
A summary of the Aries experiments and results is presented with specific attention given to the tomographic analysis developed from ground-based photometric data. The instrumentation includes particle detectors, rocket photometers, plasma probes, and 1-deg meridian scanning photometers, and an all-sky TV system. The geophysical conditions during the observations are described including the auroral features and wavelengths, rocket trajectories, and the effectiveness of particle measurements. The tomographic inversion is explained with examples of rocket-photometer height data and contrasted with ground-based photometric data. The modeling techniques used to derive height profiles are described and indirectly compared to measured auroral intensities and intensity ratios. An enhancement of atomic oxygen is inferred from discrepancies with previous studies which confirm the difference between observed intensity ratios and modeled results.
Jones, A. V.↗