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  • 1
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    Node synchronization schemes for the Big Viterbi Decoder (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Big Viterbi Decoder (BVD), currently under development for the DSN, includes three separate algorithms to acquire and maintain node and frame synchronization. The first measures the number of decoded bits between two consecutive renormalization operations (renorm rate), the second detects the presence of the frame marker in the decoded bit stream (bit correlation), while the third searches for an encoded version of the frame marker in the encoded input stream (symbol correlation). A detailed account of the operation is given, as well as performance comparison, of the three methods.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Report; p 186-200
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Recent advances in coding theory for near error-free communications (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Channel and source coding theories are discussed. The following subject areas are covered: large constraint length convolutional codes (the Galileo code); decoder design (the big Viterbi decoder); Voyager's and Galileo's data compression scheme; current research in data compression for images; neural networks for soft decoding; neural networks for source decoding; finite-state codes; and fractals for data compression.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA, Washington, Technology 2000, Volume 2; p 229-241
    Format: application/pdf
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  • 3
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    Performance of Galileo's concatenated codes with nonideal interleaving (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Galileo spacecraft employs concatenated coding schemes with Reed-Solomon interleaving depth 2. The bit error rate (BER) performance of Galileo's concatenated codes, assuming different interleaving depths (including infinite interleaving depth) are compared. It is observed that Galileo's depth 2 interleaving, when used with the experimental (15, 1/4) code, requires about 0.4 to 0.5 dB additional signal-to-noise ratio to achieve the same BER performance as the concatenated code with ideal interleaving. When used with the standard (7, 1/2) code, depth 2 interleaving requires about 0.2 dB more signal-to-noise ratio than ideal interleaving.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Report; p 148-152
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Synopsis of Mid-latitude Radio Wave Absorption in Europe (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Radio wave absorption data covering almost two years from Europe to Central Asia are presented. They are normalized by relating them to a reference absorption. Every day these normalized data are fitted to a mathematical function of geographical location in order to obtain a daily synopsis of radio wave absorption. A film of these absorption charts was made which is intended to reveal movements of absorption or absorption anomaly. In addition, radiance (temperature) data from the lower D-region are also plotted onto these charts.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program. Handbook for MAP, Vol. 10; p 24-30
    Format: application/pdf
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  • 5
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    SHARP system for personal communications (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The application of the stationary high altitude relay platform (SHARP) concept orignally developed by the Department of Communications to provide a wide range of personal communications services is addressed. The inherent merits of SHARP are ideally suited to personal communications particularly to overcome some of the limitations of the geostationary satellites (GEOS) and low earth orbit satellite systems (LEOS) when used in personal communications environment. An overview of the SHARP concept is presented, and some of its merits are outlined. High level networking concepts are presented for typical cases as applicable to personal communications.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL, Proceedings of the Workshop on Advanced Network and Technology Concepts for Mobile, Micro, and Personal Communications; p 119-124
    Format: text
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  • 6
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    An adaptive vector quantization scheme (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Vector quantization is known to be an effective compression scheme to achieve a low bit rate so as to minimize communication channel bandwidth and also to reduce digital memory storage while maintaining the necessary fidelity of the data. However, the large number of computations required in vector quantizers has been a handicap in using vector quantization for low-rate source coding. An adaptive vector quantization algorithm is introduced that is inherently suitable for simple hardware implementation because it has a simple architecture. It allows fast encoding and decoding because it requires only addition and subtraction operations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Report; p 214-220
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  • 7
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    Modulation and coding for fast fading mobile satellite communication channels (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The performance of Gaussian baseband filtered minimum shift keying (GMSK) using differential detection in fast Rician fading, with a novel treatment of the inherent intersymbol interference (ISI) leading to an exact solution is discussed. Trellis-coded differentially coded phase shift keying (DPSK) with a convolutional interleaver is considered. The channel is the Rician Channel with the line-of-sight component subject to a lognormal transformation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Jet Propulsion Lab., Proceedings of the Mobile Satellite Conference; p 291-296
    Format: application/pdf
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  • 8
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    Radar observation of known and unknown clear echoes (1979)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: Target cross-section as a function of wavelength for known insects, known bird, and dot targets is presented. Tracking data using the time series analysis was tabulated for known birds. Examples were selected from these early works to give entomologists some indication of the types of information that are available by radar as well as examples of the different sources of clear-air radar backscatter.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Wallops Flight Center Radar, Insect Population Ecology, and Pest Management; p 113-130
    Format: text
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  • 9
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    Frame error rate of the NASA concatenated coding system (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: For a concatenated coding system, the effect of interleaving depth on interleaved frame-error rate is compiled by simulation. Comparisons are made for three different inner convolutional codes; all three systems have a (255,223) 8-bit Reed-Solomon code as an outer code. For all the inner convolutional codes tested, an interleaving depth smaller that 4 causes substantial loss.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Report; p 183-187
    Format: text
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  • 10
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    A high-speed distortionless predictive image-compression scheme (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A high-speed distortionless predictive image-compression scheme that is based on differential pulse code modulation output modeling combined with efficient source-code design is introduced. Experimental results show that this scheme achieves compression that is very close to the difference entropy of the source.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Report; p 73-90
    Format: application/pdf
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