Method and apparatus for time or frequency synchronization in non-geosynchronous satellite communication systems
First Claim
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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Accused Products
Abstract
Method and apparatus for time or frequency synchronization of radio signals transmitted by user terminals in communication with a gateway through a satellite is provided. The satellite may be part of a non-synchronous satellite communication system, such as a low-earth orbit (LEO) satellite communication system for data, voice or video communications. Times of transmission of return link radio signals from the user terminals may be adjusted such that the signals arrive at the satellite or at the gateway without large time delay differentials. Carrier frequencies of return link radio signals transmitted from the user terminals may be adjusted such that the signals arrive at the satellite or at the gateway without large frequency offset differentials.
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Citations
29 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus configured to control 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 apparatus comprising:
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at least one processor coupled to at least one transceiver and configured to; compute a pre-correction time value based on a local time reference and a received signal or ephemeris of the non-geosynchronous satellite; apply the pre-correction time value to adjust the time of transmission of the first signal at the first ground station; compute a pre-correction frequency value based on a local frequency reference and the received signal or ephemeris of the non-geosynchronous satellite; apply the pre-correction frequency value to adjust the radio frequency of the first signal at the first ground station; and transmit 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. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. An apparatus for 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 apparatus comprising:
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means for computing a pre-correction time value based on a local time reference and a received signal or ephemeris of the non-geosynchronous satellite; means for applying the pre-correction time value to adjust the time of transmission of the first signal at the first ground station; means for computing a pre-correction frequency value based on a local frequency reference and the received signal or ephemeris of the non-geosynchronous satellite; means for applying the pre-correction frequency value to adjust the radio frequency of the first signal at the first ground station; and means for 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. - View Dependent Claims (21, 22, 23, 24)
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25. A non-transitory computer-readable medium comprising instructions to cause a computer or processor to control 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 instructions comprising instructions to:
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compute a pre-correction time value based on a local time reference and a received signal or ephemeris of the non-geosynchronous satellite; apply the pre-correction time value to adjust the time of transmission of the first signal at the first ground station; compute a pre-correction frequency value based on a local frequency reference and the received signal or ephemeris of the non-geosynchronous satellite; apply the pre-correction frequency value to adjust the radio frequency of the first signal at the first ground station; and transmit 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. - View Dependent Claims (26, 27, 28, 29)
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Specification