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  • COMMUNICATIONS AND RADAR  (4)
  • 2020-2022
  • 1990-1994
  • 1985-1989  (4)
  • 1
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    Broadcasting satellite service synthesis using gradient and cyclic coordinate search procedures (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Two search techniques are considered for solving satellite synthesis problems. Neither is likely to find a globally optimal solution. In order to determine which method performs better and what factors affect their performance, an experiment is designed and the same problem is solved under a variety of starting solution configuration-algorithm combinations. Since there is no randomization in the experiment, results of practical, rather than statistical, significance are presented. Implementation of a cyclic coordinate search procedure clearly finds better synthesis solutions than implementation of a gradient search procedure does with the objective of maximizing the minimum C/I ratio computed at test points on the perimeters of the intended service areas. The length of the available orbital arc and the configuration of the starting solution are shown to affect the quality of the solutions found.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AIAA PAPER 86-0641
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Broadcasting satellite service synthesis using gradient and cyclic coordinate search procedures (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Two search techniques are considered for solving satellite synthesis problems. Neither is likely to find a globally optimal solution. In order to determine which method performs better and what factors affect their performance, we design an experiment and solve the same problem under a variety of starting solution configuration-algorithm combinations. Since there is no randomization in the experiment, we present results of practical, rather than statistical, significance. Our implementation of a cyclic coordinate search procedure clearly finds better synthesis solutions than our implementation of a gradient search procedure does with our objective of maximizing the minimum C/I ratio computed at test points on the perimeters of the intended service areas. The length of the available orbital arc and the configuration of the starting solution are shown to affect the quality of the solutions found.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-176708 , NAS 1.26:176708 , TR-716548-4
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Unknown
    Engineering calculations for communications satellite systems planning (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Observed solution times were analyzed for the extended gradient and cyclic coordinate search procedures. The times used in the analysis come from computer runs made during a previously-reported experiment conducted to assess the quality of the solutions to a BSS synthesis problem found by the two search methods. The results of a second experiment with a Fixed Satellite Service (FSS) test problem are also presented. Computational results are summarized for mixed integer programming approaches for solving FSS synthesis problems. A promising heuristic algorithm is described. A synthesis model is discussed for orbital arc allotment optimization. Research plans for the near future are also presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-180106 , NAS 1.26:180106 , TR-718688-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Engineering calculations for communications satellite systems planning (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Computer-based techniques for optimizing communications-satellite orbit and frequency assignments are discussed. A gradient-search code was tested against a BSS scenario derived from the RARC-83 data. Improvement was obtained, but each iteration requires about 50 minutes of IBM-3081 CPU time. Gradient-search experiments on a small FSS test problem, consisting of a single service area served by 8 satellites, showed quickest convergence when the satellites were all initially placed near the center of the available orbital arc with moderate spacing. A transformation technique is proposed for investigating the surface topography of the objective function used in the gradient-search method. A new synthesis approach is based on transforming single-entry interference constraints into corresponding constraints on satellite spacings. These constraints are used with linear objective functions to formulate the co-channel orbital assignment task as a linear-programming (LP) problem or mixed integer programming (MIP) problem. Globally optimal solutions are always found with the MIP problems, but not necessarily with the LP problems. The MIP solutions can be used to evaluate the quality of the LP solutions. The initial results are very encouraging.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-176555 , NAS 1.26:176555 , REPT-716548-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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