Access node for end-to-end beamforming communications systems

Patent metadata

Field	Value
Publication number	US-9954601-B2
Application number	US-201715719272-A
Country	US
Kind code	B2
Filing date	Sep 28, 2017
Priority date	Apr 10, 2015
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

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.

First claim

What is claimed is:

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.

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.

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 metho

Assignees

• Viasat Inc

Inventors

• Buer Kenneth V
• Miller Mark J
• Cronin Christopher J

Classifications

• H04W4/00

  Services specially adapted for wireless communication networks; Facilities therefor · CPC title

• H04B7/0413

  MIMO systems · CPC title

• H04B7/024

  Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems · CPC title

• H04B7/204

  Multiple access · CPC title

• H04B7/18508

  with satellite system used as relay, i.e. aeronautical mobile satellite service · CPC title