Method for forward end-to-end beamforming

• US 10,396,888 B1
• Filed: 04/25/2019
• Issued: 08/27/2019
• Est. Priority Date: 04/10/2015
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Buer, Kenneth V., Miller, Mark J.
• Primary Examiner(s): Moutaouakil, Mounir
• Application Number:
  US16/394,802
• Publication Number:
  US 20190253131A1
• Time in Patent Office: 124 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 for end-to-end beamforming using an end-to-end relay, the method comprising:

computing forward beam weights for a plurality of end-to-end forward multipath channels that couple a plurality of geographically-distributed access nodes with a user terminal in a forward user beam coverage area via a plurality of transponders of the end-to-end relay, each end-to-end forward multipath channel having multipath induced by the transponders;

generating a plurality of forward uplink signals by applying the forward beam weights to a forward beam signal, such that each forward uplink signal is unique to a respective one of the access nodes;

transmitting each forward uplink signal in a time-synchronized manner by its respective access node;

receiving a respective composite input forward signal by each of the plurality of transponders of the end-to-end relay from the plurality of access nodes, each respective composite input forward signal comprising a superposition of the plurality of forward uplink signals; and

transmitting a respective forward downlink signal corresponding to the respective composite input forward signal by each of the plurality of transponders, such that the forward downlink signals form a forward user beam.

2. The method of claim 1, further comprising:

receiving a superposition of the forward downlink signals at the user terminal; and

recovering at least a portion of the forward data signal by the user terminal from the received superposition of the forward downlink signals.

3. The method of claim 1, wherein:

receiving the composite input forward signals is by a plurality of receive antenna elements;

transmitting the forward downlink signals is by a plurality of transmit antenna elements; and

each of the plurality of transponders couples a respective one of the receive antenna elements with a respective one of the transmit antenna elements.

4. The method of claim 1, wherein:

the forward user beam is one of a plurality of forward user beams, each corresponding to a forward user beam coverage 4 area that services a respective set of user terminals; and

the computing comprises computing respective forward beam weights for each end-to-end forward multipath channel, such that transmitting the forward downlink signals forms the plurality of forward user beams.

5. The method of claim 4, wherein:

the forward beam signal is one of a plurality of forward beam signals, each for transmission to an associated one of the forward user beams; and

the generating comprises applying the forward beam weights to each forward beam signal according to the end-to-end forward multipath channels corresponding to the associated forward user beam.

6. The method of claim 4, wherein there are more forward user beams than transponders.

7. The method of claim 1, wherein the generating comprises forming the forward beam signal by multiplexing a plurality of user data streams according to at least one of time-division or frequency-division multiplexing, each of the plurality of user data streams for transmission to at least one of a plurality of user terminals serviced by the forward user beam.

8. The method of claim 1, wherein there are more access nodes than transponders.

9. The method of claim 1, wherein the number of access nodes is not equal to the number of forward user beams.

10. The method of claim 1, wherein the computing comprises estimating end-to-end forward channel gains for each of the plurality of the end-to-end forward multipath channels.

11. The method of claim 10, wherein the estimating comprises estimating end-to-end forward channel gains for each of a plurality of end-to-end forward multipath channels, each end-to-end forward multipath channel coupling one of the plurality of access nodes with a reference location in one of a plurality of forward user beam coverage areas.

12. The method of claim 10, wherein:

the estimating comprises estimating a forward channel matrix as At×

E×

Cr, such that each element of the forward channel matrix models one of the plurality of end-to-end forward multipath channels, wherein;

At is a downlink radiation matrix that models a plurality of downlinks from the end-to-end relay to the user terminal,

E is a payload matrix that models the plurality of transponders, and

Cr is an uplink radiation matrix that models a plurality of uplinks from the access nodes to the end-to-end relay.

13. The method of claim 12, wherein the forward channel matrix has M vectors, each having a dimensionality equal to K, such that each vector models the end-to-end forward channel gains for multipath communications between a respective one of the plurality of access nodes and reference locations in K forward user beam coverage areas.

14. The method of claim 12, further comprising:

estimating the payload matrix by a diagonal matrix.

15. The method of claim 12, further comprising:

estimating at least one of At, E, or Cr after deployment of a craft having the end-to-end relay disposed thereon.

16. The method of claim 1, further comprising:

receiving the forward beam signal,

wherein the computing is performed before the receiving.

17. The method of claim 1, further comprising:

receiving the forward beam signal at a forward beamformer; and

communicating the forward uplink signals to the plurality of access nodes from the forward beamformer after applying the forward beam weights to the forward beam signal at the forward beamformer.

18. The method of claim 1, further comprising:

re-computing the forward beam weights as a function of re-estimated end-to-end forward channel gains after a change in composition of the plurality of access nodes.

19. The method of claim 1, further comprising forming a return user beam by:

receiving a respective return uplink signal at each of the plurality of transponders of the end-to-end relay from the user terminal;

transmitting a plurality of return downlink signals by the plurality of transponders, each return downlink signal corresponding to a respective one of the return uplink signals; and

receiving a respective return downlink signal to form a composite return signal at each of the plurality of access nodes, each respective composite return signal comprising a superposition of the plurality of return downlink signals; and

applying return beam weights to the plurality of composite return signals, the return beam weights computed for end-to-end return multipath channels that couple the user terminal with the plurality of access nodes via the plurality of transponders,

wherein applying the return beam weights comprises applying, to each composite return signal, the return beam weight associated with the access node that received that composite return signal.

20. The method of claim 19, further comprising:

transmitting the return uplink signals by the user terminal to the plurality of transponders,

wherein transmitting the forward uplink signals is by the plurality of access nodes to the plurality of transponders, and

the transmitting of the forward uplink signals and the transmitting of the return uplink signals are time-division duplexed.

21. The method of claim 19, wherein:

a first frequency range is allocated to the forward uplink signals; and

a second frequency range, that is non-overlapping with the first frequency range, is allocated to the return uplink signals.