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  • 1
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    On-board processing for future satellite communications systems: Satellite-Routed FDMA (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A frequency division multiple access (FDMA) 30/20 GHz satellite communications architecture without on-board baseband processing is investigated. Conceptual system designs are suggested for domestic traffic models totaling 4 Gb/s of customer premises service (CPS) traffic and 6 Gb/s of trunking traffic. Emphasis is given to the CPS portion of the system which includes thousands of earth terminals with digital traffic ranging from a single 64 kb/s voice channel to hundreds of channels of voice, data, and video with an aggregate data rate of 33 Mb/s. A unique regional design concept that effectively smooths the non-uniform traffic distribution and greatly simplifies the satellite design is employed. The satellite antenna system forms thirty-two 0.33 deg beam on both the uplinks and the downlinks in one design. In another design matched to a traffic model with more dispersed users, there are twenty-four 0.33 deg beams and twenty-one 0.7 deg beams. Detailed system design techniques show that a single satellite producing approximately 5 kW of dc power is capable of handling at least 75% of the postulated traffic. A detailed cost model of the ground segment and estimated system costs based on current information from manufacturers are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165419 , NASA/LERC-C-49029-D , MTR-8311
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Second year technical report on-board processing for future satellite communications systems (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Advanced baseband and microwave switching techniques for large domestic communications satellites operating in the 30/20 GHz frequency bands are discussed. The nominal baseband processor throughput is one million packets per second (1.6 Gb/s) from one thousand T1 carrier rate customer premises terminals. A frequency reuse factor of sixteen is assumed by using 16 spot antenna beams with the same 100 MHz bandwidth per beam and a modulation with a one b/s per Hz bandwidth efficiency. Eight of the beams are fixed on major metropolitan areas and eight are scanning beams which periodically cover the remainder of the U.S. under dynamic control. User signals are regenerated (demodulated/remodulated) and message packages are reformatted on board. Frequency division multiple access and time division multiplex are employed on the uplinks and downlinks, respectively, for terminals within the coverage area and dwell interval of a scanning beam. Link establishment and packet routing protocols are defined. Also described is a detailed design of a separate 100 x 100 microwave switch capable of handling nonregenerated signals occupying the remaining 2.4 GHz bandwidth with 60 dB of isolation, at an estimated weight and power consumption of approximately 400 kg and 100 W, respectively.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165155 , MTR-8164 , TR-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    On-board processing concepts for future satellite communications systems (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The initial definition of on-board processing for an advanced satellite communications system to service domestic markets in the 1990's is discussed. An exemplar system with both RF on-board switching and demodulation/remodulation baseband processing is used to identify important issues related to system implementation, cost, and technology development. Analyses of spectrum-efficient modulation, coding, and system control techniques are summarized. Implementations for an RF switch and baseband processor are described. Among the major conclusions listed is the need for high gain satellites capable of handling tens of simultaneous beams for the efficient reuse of the 2.5 GHz 30/20 frequency band. Several scanning beams are recommended in addition to the fixed beams. Low power solid state 20 GHz GaAs FET power amplifiers in the 5W range and a general purpose digital baseband processor with gigahertz logic speeds and megabits of memory are also recommended.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159683 , MTR-3943
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Application of advanced on-board processing concepts to future satellite communications systems (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159682 , MTR-3787-VOL-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    A frequency-division multiple-access system concept for 30/20 GHz high-capacity domestic satellite service (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Previously cited in issue 09, p. 1357, Accession no. A82-23484
    Keywords: COMMUNICATIONS AND RADAR
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 20; 619-625
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    An FDMA system concept for 30/20 GHz high capacity domestic satellite service (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The paper summarizes a feasibility study of a multibeam FDMA satellite system operating in the 30/20 GHz band. The system must accommodate a very high volume of traffic within the restrictions of a 5 kW solar cell array and a 2.5 GHz bandwidth. Multibeam satellite operation reduces the DC power demand and allows reuse of the available bandwidth. Interferences among the beams are brought to acceptable levels by appropriate frequency assignments. A transponder design is presented; it is greatly simplified by the application of a regional concept. System analysis shows that MSK modulation is appropriate for a high-capacity system because it conserves the frequency spectrum. Rain attenuation, a serious problem in this frequency band, is combatted with sufficient power margins and with coding. Link budgets, cost analysis, and weight and power calculations are also discussed. A satellite-routed FDMA system compares favorably in performance and cost with a satellite-switched TDMA system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AIAA PAPER 82-0447 , In: Communications Satellite Systems Conference; Mar 07, 1982 - Mar 11, 1982; San Diego, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    A frequency-routed satellite system concept using multiple orthogonally-polarized beams for frequency reuse (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The design concepts of a multibeam frequency-division multiplexed satellite system accessed by many moderately sized earth stations are outlined. In the system proposed here, traffic is routed from beam to beam through appropriate apportionment and filtering. Within a beam, the routing to particular users is achieved by conventional FDM. The optimum beam size, beam isolation, orthogonal polarization assignment to beams, the concept of beam groups yielding a simple transponder design, and the establishment of a frequency plan providing interference-free band assignments are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Milcom ''83; Proceedings of the Military Communications Conference; Oct 31, 1983 - Nov 02, 1983; Washington, DC
    Format: text
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    NASA TECHNICAL REPORTS
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