Access node for end-to-end beamforming communications systems

• US 9,954,601 B2
• Filed: 09/28/2017
• Issued: 04/24/2018
• 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): DEAN, RAYMOND S
• Application Number:
  US15/719,272
• Publication Number:
  US 20180019806A1
• Time in Patent Office: 208 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
• CPC Class Codes: H05K 999/99 : dummy group

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 communication at an access node of a communication system comprising a plurality of access nodes at geographically distributed locations providing a communication service to user terminals distributed over multiple forward user beam coverage areas via an end-to-end relay comprising multiple forward receive/transmit signal paths, the method comprising:

obtaining an access node-specific forward signal for transmission via the end-to-end relay to a plurality of the user terminals grouped by the multiple forward user beam coverage areas, the access node-specific forward signal comprising a composite of forward beam signals corresponding to a plurality of the multiple forward user beam coverage areas, the forward beam signals weighted by respective beam weights of a beam weight vector associated with the access node;

identifying forward signal transmit timing information indicating transmission timing for the access node-specific forward signal;

transmitting a forward uplink signal comprising the access node-specific forward signal and an access node beacon signal to the end-to-end relay, the access node-specific forward signal having the forward signal transmit timing information synchronized to corresponding transmit timing information in the access node beacon signal;

receiving signaling from the end-to-end relay comprising a relay beacon signal and the access node beacon signal relayed from the end-to-end relay; and

adjusting the forward uplink signal to time and phase align the relayed access node beacon signal with the received relay beacon signal.

2. The method of claim 1, further comprising:

demodulating the relay beacon signal to obtain receive timing information and receive phase information.

3. The method of claim 2, further comprising:

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

4. The method of claim 3, wherein the adjusting comprises:

adjusting timing of the forward uplink signal based on comparing the receive timing information to the relayed transmit timing information.

5. The method of claim 3, wherein the adjusting comprises:

adjusting a phase of the forward uplink signal based on comparing the receive phase information to the relayed transmit phase information.

6. The method of claim 1, wherein the identifying comprises:

demultiplexing the forward signal transmit timing information from a multiplexed access node-specific forward signal received at the access node.

7. The method of claim 1, wherein the access node-specific forward signal comprises a plurality of time-domain subsets of samples.

8. The method of claim 1, wherein:

the access node-specific forward signal comprises a plurality of sub-signals associated with different subsets of the multiple forward user beam coverage areas; and

the transmitting the forward uplink signal comprises upconverting the plurality of sub-signals to different carrier frequencies.

9. The method of claim 1, wherein:

the forward uplink signal comprises a plurality of signals transmitted over different frequency sub-bands; and

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.

18. The method of claim 7, wherein each of the plurality of time-domain subsets of samples comprises a plurality of interleaved samples for the access node-specific forward signal, the method further comprising:

de-interleaving the interleaved samples of the access node-specific forward signal.

19. The method of claim 1, wherein the relay beacon signal comprises a pseudo-noise (PN) code.

20. The method of claim 1, wherein the relay beacon signal comprises relay frame timing information.

21. The method of claim 1, wherein the access node beacon signal comprises a pseudo-noise (PN) code associated with the access node.

22. The method of claim 21, wherein the access node beacon signal comprises transmit frame timing information.

23. The method of claim 21, wherein the adjusting the forward uplink signal comprises:

adjusting a chip timing of the PN code.

24. The method of claim 9, wherein each of the plurality of subsets of forward user beam coverage areas comprises a plurality of non-overlapping forward user beam coverage areas.

25. The method of claim 9, wherein a bandwidth for each of the different frequency sub-bands is greater than or equal to 500 MegaHertz.

10. An access node for communication in a communication system comprising a plurality of access nodes at geographically distributed locations providing a communication service to user terminals distributed over multiple forward user beam coverage areas via an end-to-end relay comprising multiple forward receive/transmit signal paths, comprising:

a network interface that obtains an access node-specific forward signal for transmission to a plurality of the user terminals grouped by the multiple forward user beam coverage areas via the end-to-end relay, the access node-specific forward signal comprising a composite of forward beam signals corresponding to a plurality of the multiple forward user beam coverage areas, the forward beam signals weighted by respective beam weights of a beam weight vector associated with the access node;

a de-multiplexer that obtains forward signal transmit timing and phase information for the access node-specific forward signal;

a transmitter that transmits a forward uplink signal comprising an access node beacon signal and the access node-specific forward signal to the end-to-end relay;

a receiver that receives a downlink signal from the end-to-end relay, the downlink signal comprising a relay beacon signal and the relayed access node beacon signal relayed from the end-to-end relay;

a controller that determines a timing and phase adjustment to align relayed transmit timing and phase information in the relayed access node beacon signal with received relay timing and phase information in the received relay beacon signal; and

a transmit timing and phase compensator that outputs the forward uplink signal to the transmitter based on the timing and phase adjustment, the transmit timing and phase compensator multiplexing the access node-specific forward signal with the access node beacon signal such that the forward signal transmit timing and phase information is synchronized to corresponding transmit timing and phase information in the access node beacon signal.

11. The access node of claim 10, further comprising:

a relay beacon signal demodulator that demodulates the relay beacon signal to obtain receive timing and phase information.

12. The access node of claim 11, further comprising:

an access beacon signal demodulator that demodulates the relayed access node beacon signal to obtain relayed transmit timing and phase information.

13. The access node of claim 12, wherein the controller determines the timing and phase adjustment based on a comparison of the receive timing and phase information with the relayed transmit timing and phase information.

14. The access node of claim 10, wherein the access node-specific forward signal comprises a plurality of time-domain subsets of samples.

15. The access node of claim 10, wherein:

the access node-specific forward signal comprises a plurality of sub-signals associated with different subsets of the multiple forward user beam coverage areas; and

the transmitting the forward uplink signal comprises upconverting the plurality of sub-signals to different carrier frequencies.

16. The access node of claim 10, 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, wherein the first number is greater than the second number.

17. The access node of claim 10, wherein:

the forward uplink signal comprises a plurality of signals transmitted over different frequency sub-bands; and

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.

26. The access node of claim 10, wherein the relay beacon signal comprises a pseudo-noise (PN) code.

27. The access node of claim 10, wherein the relay beacon signal comprises relay frame timing information.

28. The access node of claim 10, wherein the access node beacon signal comprises a pseudo-noise (PN) code associated with the access node.

29. The access node of claim 28, wherein the access node beacon signal comprises transmit frame timing information.

30. The access node of claim 17, wherein each of the plurality of subsets of forward user beam coverage areas comprises a plurality of non-overlapping forward user beam coverage areas.