Dynamic forward error correction bypass in a digital communications system

• US 10,116,377 B2
• Filed: 01/06/2016
• Issued: 10/30/2018
• Est. Priority Date: 01/06/2016
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: Lohman, Michael Stephen
• Primary Examiner(s): Elallam, Ahmed
• Application Number:
  US14/989,223
• Publication Number:
  US 20170195037A1
• Time in Patent Office: 1,028 Days
• CPC Class Codes: H04B 7/185 Space-based or airborne stations; Stations for satellite systemsH04B7/204 takes precedence
• CPC Class Codes: H04B 7/18504 Aircraft used as relay or high altitude atmospheric platform
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 2001/0097 Relays

Abstract

A system and method of improving communications is provided. A gateway is communicatively coupled to an end terminal through an unmanned air vehicle (UAV), wherein a first link communicatively couples the gateway to the UAV, and a second link communicatively couples the UAV to the end terminal. At least one of the gateway and the UAV is configured to determine a signal quality on at least the first link between the gateway and the UAV in a first direction. If the signal quality exceeds a predetermined threshold, a received packet is encoded at the gateway for processing by the end terminal. The packet is further tagged with an indicator that the packet should bypass forward error correction (FEC) at the UAV.

Claims

1. A method of improving communications, comprising:

receiving a first packet at a gateway communicatively coupled to an end terminal through an unmanned air vehicle (UAV), wherein a first wireless link communicatively couples the gateway to the UAV, and a second wireless link communicatively couples the UAV to the end terminal;

determining, with one or more processors, a signal quality on at least the first link between the gateway and the UAV in a first direction;

when the signal quality exceeds a first predetermined threshold;

encoding, at the gateway, the first received packet for processing by the end terminal;

tagging the first received packet with an indicator to bypass forward error correction (FEC) at the UAV;

monitoring, with the one or more processors at the gateway, the signal quality on at least the first link;

comparing the monitored signal quality to a second threshold lower than the first threshold; and

when the monitored signal quality falls below the second threshold lower, encoding, at the gateway, the first received packets for processing by the UAV.

2. The method of claim 1, further comprising:

receiving, at the gateway, a second packet from the UAV, the second packet originating from the end terminal;

determining, with the one or more processors, whether the second packet was FEC decoded and encoded at the UAV; and

when it is determined that the second packet was not FEC decoded and encoded at the UAV, decoding the second packet at the gateway using end terminal modem processing.

3. The method of claim 1, wherein determining the signal quality comprises determining an aggregate signal quality on the first link and the second link.

4. The method of claim 1, wherein determining the signal quality comprises computing at least one of signal strength, frame error rate, and bit error rate.

5. The method of claim 1, wherein tagging the received packet further comprises indicating a particular user link on which the UAV is to transmit the received packet to the end terminal.

6. The method of claim 1, further comprising

continuing encoding and tagging packets for FEC bypass at the UAV until the monitored signal quality falls below the second threshold.

7. A gateway, comprising:

an interface configured to be communicatively coupled with an unmanned air vehicle (UAV) over a first link and with at least one end terminal over a second link between the UAV and the at least one end terminal;

at least one forward error correction (FEC) encoder configured to be interfaced with a backhaul and to receive a first packet from the backhaul;

a formatting unit coupled to the FEC encoder; and

a controller communicatively coupled to the at least one FEC encoder and the formatting unit;

wherein the controller is configured to determine whether a signal quality over the first link exceeds a first predetermined threshold;

wherein when the signal quality is determined to exceed the first predetermined threshold, the gateway switches from a first mode with the first received packet encoded for decoding by the UAV to a second mode, wherein in the second mode;

the at least one FEC encoder is configured to encode the received first packet for processing by the end terminal; and

the formatting unit is configured to tag the received first packet with an indicator to bypass FEC at the UAV; and

wherein;

when the gateway is in the second mode, the gateway monitors whether the signal quality falls below a second threshold lower than the first threshold; and

when the signal quality falls below the second threshold, the gateway switches back to the first mode, wherein the first received packet is encoded for decoding by the UAV.

8. The gateway of claim 7, wherein the formatting unit is further configured to identify a particular end terminal link, from a plurality of end terminal links between the UAV and a plurality of end terminals, over which the first packet should be sent.

9. The gateway of claim 8, wherein in tagging the first packet and in identifying the particular end terminal link, the formatting unit modifies a header of the first packet.

10. The gateway of claim 7, wherein the signal quality is computed based on both the first link and the second link.

11. The gateway of claim 10, wherein the signal quality is computed as a function of at least one of signal strength, bit error rate, and frame error rate.

12. The gateway of claim 7, wherein:

the interface is configured to receive at least one second packet from the UAV over the first link;

the formatting unit is configured to determine whether the second packet was decoded and encoded at the UAV; and

the controller is configured to select one of a first decoder and a second decoder for decoding the second packet based on the determination by the formatting unit.

13. The gateway of claim 7, wherein the gateway remains in the second mode until the monitored signal quality falls below the second threshold.

14. An unmanned air vehicle (UAV), comprising:

a first interface configured for receiving a first packet from a gateway communicatively coupled to the UAV via a first wireless link;

a second interface configured for receiving a second packet from an end terminal communicatively coupled to the UAV via a second wireless link;

a forward error correction (FEC) encoder coupled between the first interface and the second interface;

a FEC decoder coupled between the first interface and the second interface;

a bypass link coupled between the first interface and the second interface and bypassing the FEC encoder and the FEC decoder; and

a controller in communication with at least the first interface and the second interface, the controller configured to;

determine whether the first packet has been encoded for end terminal processing; and

cause the first packet to be sent on the bypass link when it has been determined that the first packet has been encoded for end terminal processing.

15. The UAV of claim 14, wherein the controller is further configured to:

determine a signal quality over at least one of the first and second wireless links; and

if the signal quality exceeds a predetermined threshold, cause the second packet to be sent on the bypass link.

16. The UAV of claim 15, wherein determining the signal quality comprises computing an indicator based on at least one of signal strength, bit error rate, and frame error rate.

17. The UAV of claim 15, further comprising a formatting unit programmed to format the first packet for FEC decoding at the gateway when the first packet is sent on the bypass link.

18. The UAV of claim 17, wherein the controller is further configured to:

determine a capacity of the first wireless link; and

if the capacity exceeds a predetermined capacity threshold, send soft decision bits of the packet to the formatting unit.

19. The UAV of claim 18, further comprising a bit width reducer coupled between the second interface and the formatting unit, the bit width reducer configured to reduce a width of the soft decision bits.

20. The UAV of claim 18, wherein if the capacity of the second wireless link does not exceed the capacity threshold, the controller is configured to send raw samples to the formatting unit.