Ground network for end-to-end beamforming

• US 10,200,114 B2
• Filed: 09/26/2017
• Issued: 02/05/2019
• Est. Priority Date: 04/10/2015
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Buer, Kenneth V., Miller, Mark J., Cronin, Christopher J.
• Primary Examiner(s): Myers, Eric
• Application Number:
  US15/715,497
• Publication Number:
  US 20180034540A1
• Time in Patent Office: 497 Days
• CPC Class Codes: H01Q 1/06 Means for the lighting or illuminating of antennas, e.g. for purpose of warning
• CPC Class Codes: H01Q 1/247 with frequency mixer, e.g. for direct satellite reception or Doppler radar
• CPC Class Codes: H01Q 1/288 Satellite antennas
• CPC Class Codes: H01Q 19/132 Horn reflector antennas; Off-set feeding
• CPC Class Codes: H01Q 21/0025 Modular arrays
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 25/001 Crossed polarisation dual antennas orthomode horns H01Q13/0258; cross-polarised rear feeds H01Q19/136; orthomode transducers H01P1/161
• CPC Class Codes: H01Q 3/247 by switching different parts of a primary active element
• CPC Class Codes: H01Q 3/40 with phasing matrix
• CPC Class Codes: H01Q 5/50 Feeding or matching arrangements for broad-band or multi-band operation
• CPC Class Codes: H04B 10/118 specially adapted for satellite communication
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/18508 with satellite system used as relay, i.e. aeronautical mobile satellite service
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays
• CPC Class Codes: H04B 7/18517 Transmission equipment in earth stations
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity
• CPC Class Codes: H04B 7/1858 Arrangements for data transmission on the physical system, i.e. for data bit transmission between network components
• CPC Class Codes: H04B 7/18586 : Arrangements for data transporting, e.g. for an end to end data transport or check
• 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
• CPC Class Codes: H04B 7/204 : Multiple access
• CPC Class Codes: H04B 7/2041 : Spot beam multiple access
• CPC Class Codes: H04W 16/26 : Cell enhancers or enhancement, e.g. for tunnels, building shadow
• CPC Class Codes: H04W 16/28 : using beam steering
• CPC Class Codes: H04W 4/00 : Services specially adapted for wireless communication networks; Facilities therefor
• CPC Class Codes: H04W 40/20 : based on geographic position or location
• CPC Class Codes: H04W 76/10 : Connection setup
• CPC Class Codes: H04W 84/06 : Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

Methods and systems are described for providing end-to-end beamforming. For example, end-to-end beamforming systems include end-to-end relays and ground networks to provide communications to user terminals located in user beam coverage areas. The ground segment can include geographically distributed access nodes and a central processing system. Return uplink signals, transmitted from the user terminals, have multipath induced by a plurality of receive/transmit signal paths in the end to end relay and are relayed to the ground network. The ground network, using beamformers, recovers user data streams transmitted by the user terminals from return downlink signals. The ground network, using beamformers generates forward uplink signals from appropriately weighted combinations of user data streams that, after relay by the end-end-end relay, produce forward downlink signals that combine to form user beams.

Claims

1. A method of providing a communication service to user terminals distributed over a user coverage area via an end-to-end relay comprising multiple forward receive/transmit signal paths, the method comprising:

obtaining multiple forward beam signals comprising forward user data streams for transmission to a plurality of the user terminals grouped by multiple forward user beam coverage areas;

identifying a forward beam weight matrix for end-to-end beamforming of transmissions from a plurality of access nodes at geographically distributed locations to the multiple forward user beam coverage areas via the end-to-end relay;

generating respective access node-specific forward signals for transmission by the plurality of access nodes, each of the respective access node-specific forward signals comprising a composite of respective forward beam signals weighted by respective forward beamforming weights of the forward beam weight matrix; and

transmitting respective forward uplink signals from the plurality of access nodes based on the respective access node-specific forward signals, wherein the respective forward uplink signals are pre-corrected to compensate for respective path delays and phase shifts between the plurality of access nodes and the end-to-end relay.

2. The method of claim 1, further comprising:

transmitting respective access node beacon signals from the plurality of access nodes to the end-to-end relay;

receiving, at the plurality of access nodes, a relay beacon signal transmitted from the end-to-end relay and relayed access node beacon signals relayed by the end-to-end relay; and

adjusting the respective forward uplink signals to perform the pre-correction based at least in part on the relay beacon signal and the relayed access node beacon signals.

3. The method of claim 2, further comprising:

demodulating the respective received relay beacon signals to obtain respective receive timing information and respective receive phase information;

demodulating the relayed access node beacon signals to obtain respective transmit timing information and respective transmit phase information.

4. The method of claim 3, wherein the demodulating of one of the relayed access node beacon signals comprises demodulating the one of the relayed access node beacon signals in downlink signals received by more than one of the plurality of access nodes.

5. The method of claim 2, wherein the adjusting comprises adjusting phase of the respective forward uplink signals to compensate for phase shift differences between the plurality of access nodes and the end-to-end relay.

6. The method of claim 2, wherein the adjusting comprises adjusting timing of the respective forward uplink signals to compensate for time delay differences between the plurality of access nodes and the end-to-end relay.

7. The method of claim 2, wherein the relay beacon signal comprises a pseudo-noise (PN) code.

8. The method of claim 2, wherein the relay beacon signal comprises frame timing information.

9. The method of claim 2, wherein each of the plurality of access nodes transmits an access node beacon signal that comprises a pseudo-noise (PN) code associated with that access node.

10. The method of claim 1, further comprising distributing the respective access node-specific forward signals to the plurality of access nodes with synchronization timing information.

11. The method of claim 10, wherein the transmitting comprises transmitting, from the plurality of access nodes, the respective access node-specific forward signals using the synchronization timing information to cause the respective access node-specific forward signals to be synchronized when received by the end-to-end relay.

12. The method of claim 10, wherein the distributing comprises:

multiplexing the respective access node-specific forward signals with the synchronization timing information to obtain respective multiplexed access node-specific forward signals; and

sending, to each of the plurality of access nodes, one of the respective multiplexed access node-specific forward signals.

13. The method of claim 1, further comprising:

receiving, at the plurality of access nodes, respective return downlink signals from the end-to-end relay, each of the respective return downlink signals comprising return user data streams transmitted from a second plurality of the user terminals and relayed by the end-to-end relay via multiple return receive/transmit signal paths of the end-to-end relay, to form a composite return signal;

identifying a return beam weight matrix for end-to-end beamforming of transmissions from multiple return user beam coverage areas to the plurality of access nodes via the end-to-end relay;

applying, to each of the respective composite return signals, respective beamforming weights of the return beam weight matrix to obtain a respective plurality of weighted composite return signals associated with each of the multiple return user beam coverage areas; and

combining, for the each of the multiple return user beam coverage areas, the respective plurality of weighted composite return signals to obtain a return beam signal associated with the each of the multiple return user beam coverage areas, wherein the respective plurality of weighted composite return signals are corrected to compensate for the respective path delays and phase shifts between the end-to-end relay and the plurality of access nodes prior to the combining.

14. The method of claim 1, wherein each of the plurality of access nodes transmits a respective one of the respective forward uplink signal for relay to a respective plurality of the multiple forward user beam coverage areas via a respective plurality of the multiple forward receive/transmit signal paths of the end-to-end relay.

15. The method of claim 1, wherein the obtaining comprises:

grouping the forward user data streams according to the multiple forward user beam coverage areas to obtain multiple forward beam data streams, each of the multiple forward beam data streams comprising a respective subset of the forward user data streams; and

modulating the multiple forward beam data streams according to one or more modulation schemes to obtain the multiple forward beam signals.

16. The method of claim 1, wherein the plurality of access nodes are distributed across an access node coverage area corresponding to a coverage area of a feeder link antenna of the end-to-end relay.

17. The method of claim 16, wherein the multiple forward user beam coverage areas comprise the user coverage area, and wherein the access node coverage area is at least partially overlapping with the user coverage area.

18. The method of claim 1, wherein more than one of the plurality of access nodes are located within one of the multiple forward user beam coverage areas.

19. The method of claim 1, wherein at least one of the multiple forward user beam coverage areas covers an area where no access node is located.

20. The method of claim 1, wherein the plurality of access nodes has a first number of the access nodes and the end-to-end relay has a second number of the forward receive/transmit signal paths, and wherein the second number is different than the first number.

21. The method of claim 20, wherein the first number is greater than the second number.

22. The method of claim 20, wherein the multiple forward user beam coverage areas has a third number of the forward user beam coverage areas, and wherein the third number is different than the first number.

23. The method of claim 1, wherein the end-to-end relay is a satellite.

24. The method of claim 1, wherein the plurality of access nodes transmit the respective forward uplink signals in a forward uplink frequency range and the end-to-end relay relays the respective forward uplink signals via the forward receive/transmit signal paths to the multiple forward user beam coverage areas using a forward downlink frequency range, and wherein the forward downlink frequency range is different than the forward uplink frequency range.

25. The method of claim 1, wherein at least one of the plurality of access nodes transmits a respective forward uplink signal that comprises a plurality of modulated signals transmitted over different frequency sub-bands, wherein each of the plurality of modulated signals is based on an access node-specific forward signal associated with one of the different frequency sub-bands.

26. The method of claim 25, wherein the multiple forward user beam coverage areas comprise a plurality of subsets of forward user beam coverage areas associated with the different frequency sub-bands.

27. The method of claim 26, wherein each of the plurality of subsets of forward user beam coverage areas comprises a plurality of non-overlapping forward user beam coverage areas.

28. The method of claim 25, wherein a bandwidth for each of the different frequency sub-bands is greater than or equal to 500 MegaHertz.

29. The method of claim 1, wherein the forward beam weight matrix has dimensions corresponding to a number of the plurality of access nodes and a number of the multiple forward user beam coverage areas.