Method and apparatus for paging a user terminal within the “sweet spot” of a satellite
First Claim
1. In a satellite communications system comprising at least one gateway, one satellite, and a user terminal (UT), wherein the satellite produces a footprint formed by a plurality of beams and each beam includes a plurality of channels, a method for sending a page to the UT, comprising:
- (a) recalling a location of the UT that corresponds to a known location of the UT at a time t1;
(b) determining an area defined by a radius originating at the UT location, within which the UT is assumed to be located at a later time t2, and based on a distance the UT could have traveled in a time period t2−
t1;
(c) determining when all locations within the area are located within a predetermined preferential higher gain portion of the footprint of the satellite at a time t3, where t3≧
t2; and
(d) sending the page from the gateway to the UT on at least one of the channels.
1 Assignment
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Accused Products
Abstract
An apparatus and method for paging a user terminal (UT) using a satellite communications system having a gateway and one or more satellites, wherein each satellite produces a plurality of beams and each beam includes a plurality of channels. The method of the present invention includes the step of recalling a location of the UT, wherein the recalled location corresponds to a location of the UT at a time t1. In one embodiment this is accomplished by performing a lookup in a table that includes location information for user terminals at different points in time. The method also includes the step of determining an area, based on the recalled location, within which the UT is assumed to be located at a time t2, where time t2 is later in time than time t1. The next step is to determine a time t3, where t3 is equal to or later in time than time t2, when the following two criteria are satisfied. First a satellite of the one or more satellites has an elevation angle between θ1 and θ2. Second, all locations within the area are located within a footprint of the satellite (that has an elevation angle between θ1 and θ2). The elevation angles θ1 and θ2 can be determined from the perspective of the recalled location. Alternatively, the elevation angle can be determined from the perspective of all locations within the area. This ensures that the UT is in the “sweet spot” of the satellite (where the gain of signals sent from the satellite are highest) when the UT is paged. A page is then sent from the gateway to the UT on a channel of a beam of the satellite at time t3. The page can be sent on a channel of every beam of a plurality of beams that make up the footprint of the satellite at time t3. Alternatively, the page can be sent on a channel of selected beams of the footprint. By waiting until the UT is within the “sweet spot” to page the UT, less power can be used by the satellite. In addition, this type of operation allows the UT to use an antenna that has a substantial gain only when the UT is within the “sweet spot”. This allows the use of satellite power to be reduced further.
214 Citations
43 Claims
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1. In a satellite communications system comprising at least one gateway, one satellite, and a user terminal (UT), wherein the satellite produces a footprint formed by a plurality of beams and each beam includes a plurality of channels, a method for sending a page to the UT, comprising:
-
(a) recalling a location of the UT that corresponds to a known location of the UT at a time t1;
(b) determining an area defined by a radius originating at the UT location, within which the UT is assumed to be located at a later time t2, and based on a distance the UT could have traveled in a time period t2−
t1;
(c) determining when all locations within the area are located within a predetermined preferential higher gain portion of the footprint of the satellite at a time t3, where t3≧
t2; and
(d) sending the page from the gateway to the UT on at least one of the channels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
(i) determining a group (g1) of beams that have a coverage area that covers any location within the area at the time t3, wherein the group (g1) of beams is selected from the plurality of beams that form the footprint; and
(ii) sending the page from the gateway to the UT on a channel of each of the group (g1) of beams at the time t3.
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3. The method of claim 1, wherein the UT employs a higher gain beam of the plurality of beams to receive pages which is available in said preferential portion of the footprint.
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4. The method of claim 1, wherein the UT employs a higher gain beam of the plurality of beams to receive pages which is available within said sweet spot of the satellite.
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5. The method of claim 1, wherein the UT employs a higher gain beam of the plurality of beams to receive pages which is available when said satellite has said predetermined preferential orbital position.
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6. The method of claim 1, wherein said predetermined preferential portion of the footprint of the satellite is defined as a region in which the satellite has an elevation angle between θ
-
1 and θ
2 with respect to the UT location.
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1 and θ
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7. The method of claim 6, wherein the elevation angle is determined from a perspective of the all locations within the area such that the satellite has the elevation angle between θ
-
1 and θ
2 for the all locations within the area at the time t3.
-
1 and θ
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8. The method of claim 6, wherein the UT comprises an antenna with a gain that is highest when it receives a signal having an elevation angle of arrival between θ
-
1 and θ
2.
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1 and θ
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9. The method of claim 6, wherein the elevation angle is determined from a perspective of the UT location.
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10. The method of claim 9, wherein θ
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1 is approximately 25 degrees and θ
2 is approximately 40 degrees.
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1 is approximately 25 degrees and θ
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11. In a satellite communications system having at least one gateway, one satellite, and a user terminal (UT), wherein the satellite produces a footprint formed by a plurality of beams and each beam includes a plurality of channels, a method for sending a page to the UT, comprising:
-
(a) recalling a location of the UT that corresponds to a known location of the UT at a time tl;
(b) determining an area defined by a radius originating at the UT location, within which the UT is assumed to be located at a later time t2, and based on a distance the UT could have traveled in a time t2−
t1;
(c) determining a time t3, where t3≧
t2, when all locations within the area are within a “
sweet spot”
of the satellite; and
(d) sending the page from the gateway to the UT at least one of the channels at the time t3. - View Dependent Claims (12, 13, 14)
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15. In a satellite communications system having at least one gateway, satellite, and user terminal (UT), wherein each satellite produces a footprint formed by a plurality of beams and each beam includes a plurality of channels, an apparatus for sending a page to the UT, comprising:
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means for recalling a location of the UT that corresponds to a known location of the UT at a time t1;
means for determining an area defined by a radius originating at the UT location, within which the UT is assumed to be located at a later time t2, and based on a distance the UT could have traveled in a time t2−
t1, whenthe satellite has a predetermined preferential orbital position relative to the UT, and all locations within the area are located within the footprint; and
means for sending the page from the gateway to the UT on at least one of the channels at a time t3. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. In a satellite communications system comprising at least one gateway, one satellite, and a user terminal (UT), wherein the satellite produces a footprint formed by a plurality of beams and each beam includes a plurality of channels, an apparatus for sending a page to the UT, comprising:
-
means for recalling a location of the UT corresponding to a known location of the UT at a time t1;
means for determining an area defined by a radius originating at the UT location, within which the UT is assumed to be located at a later time t2, and based on a distance the UT could have traveled in a time period t2−
t1;
means for determining at a time t3 where t3≧
t2, when all locations within the area are within a “
sweet spot”
of the satellite; and
means for sending the page from the gateway to the UT on at least one of the channels at the time t3. - View Dependent Claims (25, 26, 27)
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28. In a satellite communications system having at least one gateway and a plurality of satellites, wherein each satellite produces a footprint formed by a plurality of beams and each beam includes a plurality of channels, a method for sending a page to a user terminal UT, comprising:
-
(a) recalling a location of the UT corresponding to a known location of the UT at a time t1;
(b) determining an area defined by a radius originating at the UT location, within which the UT is assumed to be located at a later time t2, and based on a distance the UT could have traveled during a time period t2−
t1;
(c) determining a time t3, where t3≧
t2, whena satellite of the plurality of satellites has an elevation angle between θ
1 and θ
2, all locations within the area are located within a beam coverage area of one beam of the satellite, andthe one beam theoretically has a power at all locations within the area that is at least a predetermined amount of power higher than any other beam covering any location within the area; and
(d) sending the page from the gateway to the UT on at least one of the channels of the one beam at the time t3. - View Dependent Claims (29, 30, 31, 32, 33)
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34. In a satellite communications system having at least one gateway, a plurality of satellites, wherein each satellite produces a footprint formed by a plurality of beams and each beam includes a plurality of channels, an apparatus for sending a page to a user terminal (UT), comprising:
-
means for recalling a location of the UT corresponding to a known location of the UT at a time t1;
means for determining an area defined by a radius originating at the UT location, within which the UT is assumed to be located at a later time t2, and based on a distance the UT could have traveled in a time t2−
t1;
means for determining at a time t3 where t3≧
t2,a satellite of the plurality of satellites has an elevation angle between θ
1 and θ
2,all locations within the area are within a beam coverage area of one beam of the satellite, and the one beam theoretically has a power at all locations within the area that is at least a predetermined amount of power higher than any other beam covering any location within the area; and
means for sending the page from the gateway to the UT on at least one of the channels of the one beam at the time t3. - View Dependent Claims (35, 36, 37, 38, 39)
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40. In a satellite communications system comprising a gateway, a satellite, and a user terminal (UT), a method for sending a page to the UT, comprising:
-
(a) recalling a location of the UT corresponding to a known location of the UT at a time tl;
(b) determining an area defined by a radius originating at the UT location, within which the UT is assumed to be located at a later time t2, and based on a distance the UT could have traveled during a time t2−
t1;
(c) determining a time t3 where t3≧
t2, when signals sent by the satellite will be received from a preferential area in space with respect to all locations within the area; and
(d) sending the page from the gateway to the UT on at least one of the channels of the one beam at the time t3. - View Dependent Claims (41, 42, 43)
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Specification