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Method and apparatus for time or frequency synchronization in non-geosynchronous satellite communication systems

  • US 9,900,856 B2
  • Filed: 09/23/2015
  • Issued: 02/20/2018
  • Est. Priority Date: 03/20/2015
  • Status: Active Grant
First Claim
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1. A method of controlling a time of transmission and radio frequency of a first signal at a first ground station that includes a first user terminal (UT) in communication with a non-geosynchronous satellite, the non-geosynchronous satellite further being in communication with a gateway, the method comprising:

  • computing a pre-correction time value based on a local time reference and a received signal or ephemeris of the non-geosynchronous satellite;

    applying the pre-correction time value to adjust the time of transmission of the first signal at the first ground station;

    computing a pre-correction frequency value based on a local frequency reference and the received signal or ephemeris of the non-geosynchronous satellite;

    applying the pre-correction frequency value to adjust the radio frequency of the first signal at the first ground station; and

    transmitting the first signal to the non-geosynchronous satellite in accordance with the time of transmission that is adjusted based on the pre-correction time value and the radio frequency that is adjusted based on the pre-correction frequency value,wherein the pre-correction time value is configured to reduce a time-of-arrival (TOA) differential between a TOA of the first signal at the non-geosynchronous satellite and/or the gateway and one or more TOAs of one or more other signals from one or more other UTs at the non-geosynchronous satellite and/or the gateway,wherein the pre-correction frequency value is configured to reduce a frequency offset differential between a radio frequency of the first signal at the non-geosynchronous satellite and/or the gateway and one or more radio frequencies of the one or more other signals from the one or more other UTs at the non-geosynchronous satellite and/or the gateway, or any combination thereof.

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