Method and system for transmitting radio signals between a fixed terrestrial station and user mobile terminals via a network of satellites
First Claim
1. Method of transmitting radio signals via a satellite network between at least one fixed terrestrial station and user terminals, wherein the satellite network comprises a plurality of satellites rotating about a terrestrial globe in a circular orbit and at a particular rotation speed, wherein the orbits are inclined to an equator and have a radius less than that of geostationary orbits, wherein the satellites are triply geosynchronous, and wherein each satellite comprises an arrangement of antennas for generating at least one beam with a radiation pattern directed towards a surface of the terrestrial globe and associated with a frequency band of frequencies of particular bandwidth, the method comprising at least the following steps:
- dividing said beam into a particular number of contiguous pencil beams, wherein said each of said pencil beams is associated with a frequency sub-band and wherein said frequency sub-band is a subdivision of said particular bandwidth;
setting up a communication link in at least one direction between said one fixed terrestrial terminal station and a first user terminal of said user terminals via a first satellite of said satellite network, wherein a first portion of said communication link between said first satellite and said first user terminal is set up by using an instantaneous transmission frequency in a first frequency sub-band associated with a first pencil beam which illuminates said first user terminal when said first satellite flies over said first user terminal and wherein a second portion of said communication link is set up between said first satellite and said one fixed terrestrial terminal station; and
progressively shifting said transmission frequency during a period of the first portion of said communication link towards a second frequency sub-band associated with an adjacent pencil beam and at a rate proportional to said particular rotation speed so as to compensate said rotation and to enable tracking of said satellite.
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Abstract
The invention concerns a method and a system for transmitting radio signals between a fixed terrestrial station and mobile user terminals via a network of satellites in inclined circular orbits having a radius less than that of geostationary orbits. The beams generated are divided into pencil beams each associated with a continuous sub-band of frequencies in increasing frequency or decreasing frequency order. The instantaneous transmission frequency is offset progressively during the call towards the frequency subband of the adjacent pencil beam, at a rate proportional to the orbital rotation speed, to enable switching between pencil beams or between satellites. Applications include transmission via satellites in non-geostationary orbit.
308 Citations
22 Claims
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1. Method of transmitting radio signals via a satellite network between at least one fixed terrestrial station and user terminals, wherein the satellite network comprises a plurality of satellites rotating about a terrestrial globe in a circular orbit and at a particular rotation speed, wherein the orbits are inclined to an equator and have a radius less than that of geostationary orbits, wherein the satellites are triply geosynchronous, and wherein each satellite comprises an arrangement of antennas for generating at least one beam with a radiation pattern directed towards a surface of the terrestrial globe and associated with a frequency band of frequencies of particular bandwidth, the method comprising at least the following steps:
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dividing said beam into a particular number of contiguous pencil beams, wherein said each of said pencil beams is associated with a frequency sub-band and wherein said frequency sub-band is a subdivision of said particular bandwidth; setting up a communication link in at least one direction between said one fixed terrestrial terminal station and a first user terminal of said user terminals via a first satellite of said satellite network, wherein a first portion of said communication link between said first satellite and said first user terminal is set up by using an instantaneous transmission frequency in a first frequency sub-band associated with a first pencil beam which illuminates said first user terminal when said first satellite flies over said first user terminal and wherein a second portion of said communication link is set up between said first satellite and said one fixed terrestrial terminal station; and progressively shifting said transmission frequency during a period of the first portion of said communication link towards a second frequency sub-band associated with an adjacent pencil beam and at a rate proportional to said particular rotation speed so as to compensate said rotation and to enable tracking of said satellite. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of transmitting radio signals between a first user terminal and a satellite network comprising a first satellite which rotates around a terrestrial body at a particular rotation speed, the method comprising the steps of:
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(a) dividing a frequency beam generated by said satellite into a predetermined number of contiguous pencil beams, wherein said frequency beam is associated with a frequency band having a particular bandwidth, wherein said pencil beams are respectively associated with frequency sub-bands, and wherein said frequency sub-bands respectively relate to subdivisions of said particular bandwidth; (b) setting up a communication link between said first user terminal and said first satellite by using an instantaneous transmission frequency in a first frequency sub-band associated with a first pencil beam which illuminates said first user terminal when said first satellite flies over said first user terminal; and (c) progressively shifting said instantaneous transmission frequency during a period of the communication link towards a second frequency sub-band associated with an adjacent pencil beam, wherein said instantaneous transmission frequency is shifted at a rate proportional to said particular rotation speed of said first satellite. - View Dependent Claims (13, 14, 15, 16)
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17. A system comprising a satellite network, at least one fixed terrestrial station, and user terminals, for transmitting radio signals via said satellite network between said at least one fixed terrestrial station and said user terminals, wherein the satellite network comprises a plurality of satellites rotating about a terrestrial globe in a circular orbit and at a particular rotation speed, wherein the orbits are inclined to an equator and have a radius less than that of geostationary orbits, wherein the satellites are triply geosynchronous, and wherein each satellite comprises an arrangement of antennas for generating at least one beam with a radiation pattern directed towards a surface of the terrestrial globe and associated with a frequency band of frequencies of particular bandwidth, the system comprising:
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means for dividing said beam into a particular number of contiguous pencil beams, wherein said each of said pencil beams is associated with a frequency sub-band and wherein said frequency sub-band is a subdivision of said particular bandwidth; means for setting up a communication link in at least one direction between said one fixed terrestrial terminal station and a first user terminal of said user terminals via a first satellite of said satellite network, wherein a first portion of said communication link between said first satellite and said first user terminal is set up by using an instantaneous transmission frequency in a first frequency sub-band associated with a first pencil beam which illuminates said first user terminal when said first satellite flies over said first user terminal and wherein a second portion of said communication link is set up between said first satellite and said one fixed terrestrial terminal station; and means for progressively shifting said transmission frequency during a period of the first portion of said communication link towards a second frequency sub-band associated with an adjacent pencil beam and at a rate proportional to said particular rotation speed so as to compensate said rotation and to enable tracking of said satellite. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification