Method and system for providing broadband mobile access from geostationary satellites to platforms using small, low profile antennas

• US 20030203733A1
• Filed: 04/29/2003
• Published: 10/30/2003
• Est. Priority Date: 04/29/2002
• Status: Active Grant

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Etherware LLC
• Inventors: Sharon, Thomas E.
• Granted Patent: US 6,694,137 B2
• Time in Patent Office: Days
• US Class Current: 455/427
• CPC Class Codes: H01Q 1/288 Satellite antennas
• CPC Class Codes: H01Q 19/192 with dual offset reflectors
• CPC Class Codes: H04B 7/18589 Arrangements for controlling an end to end session, i.e. for initialising, synchronising or terminating an end to end link

Abstract

A satellite-based communications system operating at high data rates in a broadcasting (multicasting) mode enables the use of mobile ground terminals with low profile antennas whose areas are significantly smaller than previous embodiments not using this invention. The invention can be applied to existing (in-orbit) or new satellites (including those in non-geostationary orbits) operating with linearly polarized downlink transponders. Important embodiments include the use of Ku FSS satellites providing service within the continental U.S. (“CONUS”), and the use of Ku BSS satellites operating within Europe. Transponder pairs on board the satellite with opposite linear polarization, but overlapping frequency bands, receive a specially processed uplink waveform from an uplink facility. Service may be optimized for (1) a particular geographical area by using receiving sensors located in that area, monitoring the polarization of the broadcast signal; or (2) a particular location with the satellite operating in a unicasting mode (delivery of Internet data or “local” video/audio broadcasts). A spread-spectrum waveform can also be used on the downlink, with the resultant processing gain applying directly to antenna area reduction and improved interference. Redundancy or increased capacity can be achieved by locating a second satellite in the same orbital location broadcasting the orthogonal circular (as received on the ground) polarization.

Claims

1. A satellite-based communications network, comprising

a plurality of mobile user terminals with integrated tracking antennas;

a communications satellite comprising at least a pair of transponders having overlapping frequency ranges and operative to transmit a downlink signal having certain polarization components and comprising video and audio content for reception by the mobile user terminals operating within a coverage area of the communications satellite;

a plurality of remote monitoring terminals positioned at locations within the coverage area of the communications satellite, each monitoring terminal operative to monitor the polarization components of the downlink signal as received by the monitoring terminal and to output measured polarization data in response to monitoring of the downlink signal; and

an uplink transmitting facility for transmitting an uplink signal for reception by the transponders of the communications satellite, the uplink transmitting facility responsive to the measured polarization data output by the monitoring terminals to control the relative phase and amplitude of the uplink signal,

whereby the transponders are responsive to the relative phase and amplitude of the uplink signal to maintain at least a predetermined threshold of quality in the polarization components for the downlink signal received by the mobile user terminals operating in at least a portion of the coverage area for the communications satellite.

2. The network recited by claim 1, further comprising a content aggregation network operative to accept the video and audio content from a plurality of sources and to deliver the video and audio content to the uplink transmitting facility, wherein the uplink signal transmitted by the uplink transmitting facility further comprises the video and audio content for subsequent broadcast by the communications satellite in accordance with a programming schedule.

3. The network recited by claim 1, further comprising a return link between at least one of the mobile user terminals and the uplink transmitting facility to communicate user content requests and location data from the mobile user terminal to the uplink transmitting facility.

4. The network recited by claim 1, further comprising a network operations center operative to generate aggregated broadcast content by aggregating and formatting broadcast content for delivery to the uplink transmitting facility, wherein the uplink signal transmitted by the uplink transmitting facility further comprises the aggregated broadcast content for subsequent broadcast by the communications satellite within the coverage area of the communications satellite.

5. The network recited by claim 1 wherein the downlink signal output by the transponders of the communications satellite further comprises a spread spectrum code to support a reduction in the size of each tracking antenna required for reception of the downlink signal by the mobile user terminals and to reduce adjacent satellite interference in the reception of the downlink signal by the mobile user terminals.

6. The network recited by claim 1 further comprising a second communications satellite positioned in the same orbital location as the communications satellite for reception by the mobile user terminals, the second communications satellite having at least one pair of transponders operative to output another downlink signal having polarization components orthogonal to the polarization components of the downlink signal output by the communications satellite, the other downlink signal comprising the video and audio content of the downlink signal output by the communications satellite.

7. The network recited by claim 1, wherein the polarization components comprise a pair of opposite linear polarizations and the transponders are responsive to the relative phase and amplitude of the uplink signal to produce the downlink signal having a new carrier center frequency within the overlap region of the overlapping frequency ranges and exhibiting circular polarization for reception at ground level by the mobile user terminals.

8. A satellite-based communications network, comprising

a plurality of mobile user terminals with integrated tracking antennas;

a communications satellite comprising at least a pair of transponders having overlapping frequency ranges and operative to communicate a downlink signal having certain polarization components and comprising Internet data for reception by the mobile user terminals operating within a coverage area of the communications satellite;

a plurality of remote monitoring terminals positioned within the coverage area of the communications satellite, each monitoring terminal operative to monitor the polarization components of the downlink signal and to output measured polarization data in response to monitoring of the downlink signal;

a plurality of remote monitoring terminals positioned at locations within the coverage area of the communications satellite, each monitoring terminal operative to monitor the polarization components of the downlink signal as received by the monitoring terminal and to output measured polarization data in response to monitoring of the downlink signal; and

an uplink transmitting facility for transmitting an uplink signal for reception by the transponders of the communications satellite, the uplink transmitting facility responsive to the measured polarization data output by the monitoring terminals to adjust at least one correction factor for the uplink signal,

whereby the transponders are responsive each correction factor of the uplink signal to maintain at least a predetermined threshold of quality in the polarization components of the downlink signal received by the mobile user terminals operating in at least a portion of the coverage area for the communications satellite.

9. The network recited by claim 8, further comprising a return link between at least one of the mobile user terminals and the uplink transmitting facility to communicate user data requests, location data and return link data from the mobile user terminal to the uplink transmitting facility.

10. The network recited by claim 8, further comprising a network operations center, coupled to the Internet, operative to store and sequence Internet data for intended delivery to the uplink transmitting facility, wherein the uplink signal transmitted by the uplink transmitting facility further comprises the Internet data for subsequent communication by the communications satellite within the coverage area of the communications satellite.

11. The network recited by claim 8 wherein the downlink signal output by the transponders of the communications satellite further comprises a spread spectrum code to support a reduction in the size of each tracking antenna required for reception of the downlink signal by the mobile user terminals and to reduce adjacent satellite interference in the reception of the downlink signal by the mobile user terminals.

12. The network recited by claim 8 further comprising a second communications satellite positioned in the same orbital location as the communications satellite for reception by the mobile user terminals, the second communications satellite having at least one pair of transponders operative to output another downlink signal having polarization components orthogonal to the polarization components of the downlink signal output by the communications satellite, the other downlink signal comprising the Internet data of the downlink signal output by the communications satellite.

13. The network recited by claim 8, wherein the polarization components comprise a pair of opposite linear polarizations and the transponders are responsive to the correction factors of the uplink signal to produce the downlink signal having a new carrier center frequency within the overlap region of the overlapping frequency ranges and exhibiting circular polarization for reception at ground level by the mobile user terminals.

14. A method for communicating a downlink signal via a communications satellite to a plurality of mobile user terminals operating within at least a portion of the coverage area for the communications satellite, the downlink signal having certain polarization parameters and comprising broadcast content, comprising the steps:

generating measured polarization data by measuring the polarization parameters of the downlink signal in response to monitoring the downlink signal at one or more ground locations within the coverage area of the communications satellite;

outputting the measured polarization data;

transmitting uplink signals for reception by the communications satellite, the uplink signals comprising adjustment factors for adjusting at least one of the polarization parameters of the downlink signal; and

varying at least one of the adjustment factors for the uplink signals in response to receipt of the measured polarization data to maintain at least a predetermined threshold of quality for the polarization parameters of the downlink signal as received at ground level by the mobile user terminals.

15. A method for communicating a downlink signal output via a communications satellite to a plurality of mobile user terminals operating within at least a portion of the coverage area for the communications satellite, the downlink signal having certain polarization parameters and comprising broadcast content, comprising the steps:

transmitting uplink signals for reception by the communications satellite, the uplink signals comprising adjustment factors for adjusting the polarization parameters of the downlink signal; and

varying at least one of the adjustment factors for the uplink signals based on measured polarization data to maintain at least a predetermined threshold of quality for the polarization parameters of the downlink signal as received at ground level by the mobile user terminals, the measured polarization data comprising measurements of the polarization parameters of the downlink signal, the measurements collected at one or more ground locations within the coverage area of the communications satellite.