Concatenated coding system for satellite communications

• US 6,138,261 A
• Filed: 04/29/1998
• Issued: 10/24/2000
• Est. Priority Date: 04/29/1998
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Perahia, Eldad, Wilcoxson, Donald C., Kchao, Chamroeun
• Primary Examiner(s): MOISE, EMMANUEL LIONEL
• Application Number:
  US09/069,681
• Time in Patent Office: 909 Days
• Field of Search: 714/774, 714/784, 714/756, 714/786, 714/755, 370/307, 370/316, 370/319, 370/320, 370/330, 375/274, 455/12.1, 455/13.3, 455/20
• US Class Current: 714/755
• CPC Class Codes: H03M 13/15 Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, Bose-Chaudhuri-Hocquenghem [BCH] codes H03M13/17 takes precedence

Abstract

The present invention provides a method for custom coding uplink signals and downlink beams in a satellite communications system. The method includes the step of applying, at a ground station (100), an outer code (102) to an uplink signal to produce an outer coded uplink signal. Next, the ground station (100) applies a selected reduced complexity inner code (104) to the outer coded uplink signal to produce a concatenated coded uplink signal. The ground station (100) transmits the concatenated coded uplink signal to a satellite (110). At the satellite (110), the inner code of the concatenated coded uplink signal is decoded (116) to produce an outer coded satellite data stream. Next, the satellite (110) applies a selected inner code (120) to a portion of the outer coded satellite data stream to produce a concatenated coded satellite data stream. The satellite (110) then transmits the concatenated coded satellite data stream in a downlink beam to a destination ground station (126).

Claims

1. A method for custom coding uplink signals at a ground station and downlink beams at a satellite, the method comprising the following steps:

applying, at an originating ground station, an outer code to a first uplink signal to produce an outer coded uplink signal;

applying a reduced complexity inner code to said outer coded uplink signal to produce a concatenated coded uplink signal;

transmitting said concatenated coded uplink signal to a satellite;

decoding, at said satellite, said reduced complexity inner code on said concatenated coded uplink signal to produce an outer coded satellite data stream;

applying at least one selected inner code, at said satellite, to said outer coded satellite data stream, without decoding said outer code at said satellite, to produce a concatenated coded satellite data stream; and

transmitting said concatenated coded satellite data stream in a downlink beam to a destination ground station, wherein said first uplink signal remains encoded with said outer code from transmission to the satellite until received by the destination ground station.

2. The method of claim 1, wherein said step of applying a reduced complexity inner code applies a reduced complexity block code.

3. The method of claim 1, wherein said step of applying a reduced complexity block code applies a (16,8) block code.

4. The method of claim 1, wherein said step of applying a reduced complexity block code applies a (8,4) block code.

5. The method of claim 1, wherein said step of applying a reduced complexity block code applies a (12,8) block code.

6. The method of claim 1, wherein said step of applying a reduced complexity inner code applies a reduced complexity convolutional code.

7. The method of claim 6, wherein said step of applying a reduced complexity convolutional code applies a convolutional code with a constraint length between 2-4 inclusive.

8. The method of claim 1, wherein said step of applying a reduced complexity inner code applies an inner code requiring less than approximately 20% of available processing power at said satellite to decode.

9. The method of claim 1, wherein said step of applying a selected inner code applies said selected inner code only to one individual data channel located in said outer coded satellite data stream.

10. The method of claim 1, wherein said step of applying a selected inner code applies said selected inner code to an individual downlink beam.

11. The method of claim 1, wherein said step of applying a selected inner code adaptively punctures a single inner code in accordance with a BER required for each individual data channel in said outer coded satellite data stream.

12. The method of claim 1, wherein said step of applying a selected inner code chooses said selected inner code according to a desired downlink BER.

13. The method of claim 1, wherein said step of applying a selected inner code chooses said selected inner code according to market driven criteria.

14. The method of claim 1 wherein said step of applying a reduced complexity innercode comprises adapatively selecting inner code based upon at least one of measured downlink signal-to-noise ratio and symbol error rate.

15. The method of claim 1 comprising interleaving coded Reed Solomon Symbols before applying selected inner code at said satellites.

16. The method of claim 1, wherein said decoding and applying steps at said satellite further comprise the following steps:

conveying said outer coded uplink signal though said satellite without decoding said outer code.

17. The method of claim 1, further comprising the following steps:

measuring at the destination ground station a signal to noise ratio of said downlink beam; and

changing a coding rate of said inner code selected by said satellite based on said measured signal-to-noise ratio.

18. The method of claim 1, further comprising the following step:

selecting a coding rate of said inner code applied at said satellite to said satellite data stream independent of a coding rate of said inner code applied to said uplink signal.

19. A method for custom coding downlink beams at a satellite, the method comprising the following steps:

receiving, at a satellite, a concatenated coded uplink signal including a reduced complexity inner code having a first inner coding rate;

decoding, at said satellite, said reduced complexity inner code on said concatenated coded uplink signal to produce an outer coded satellite data stream;

applying at least one selected inner code having a second inner coding rate, at said satellite, to said outer coded satellite data stream to produce a concatenated coded satellite data stream, said first and second inner coding rates being different; and

transmitting said concatenated coded satellite data stream in a downlink beam to a destination ground station, wherein said satellite does not decode an outer code applied to the outer coded satellite data stream.

20. The method of claim 19, wherein said reduced complexity inner code is a reduced complexity block code.

21. The method of claim 19, wherein said reduced complexity inner code is a reduced complexity convolutional code.

22. The method of claim 21, wherein said reduced complexity convolutional code applies is convolutional code with a constraint length between 2-4 inclusive.

23. The method of claim 19, wherein said step of decoding said reduced complexity inner code requires less than approximately 20% of available processing power at said satellite.

24. The method of claim 19, wherein said step of applying a selected inner code applies said selected inner code to at least one individual data channel located in said outer coded satellite data stream.

25. The method of claim 19, wherein said step of applying a selected inner code applies said selected inner code to an individual downlink beam.

26. The method of claim 19, wherein said step of applying a selected inner code chooses said selected inner code according to a desired downlink BER.

27. The method of claim 19, wherein said step of applying a selected inner code adaptively punctures a single inner code in accordance with a BER required for each individual data channel in said outer coded satellite data stream.

28. The method of claim 19 wherein said step of applying a selected inner code adaptively selects an inner code based upon measured downlink signal to noise ratio or symbol error rate.

29. The method of claim 19 wherein said step of applying a reduced complexity innercode comprises adapatively selecting inner code based upon at least one of measured downlink signal-to-noise ratio and symbol error rate.

30. The method of claim 19 comprising interleaving coded RS Symbols before applying selected inner code at said satellites.

31. The method of claim 19, further comprising the following step:

conveying outer coded data received in said concatenated coded uplink signal through said satellite to be transmitted in said concatenated coded satellite data stream without decoding on the satellite an outer code of said outer coded data.

32. The method of claim 19, further comprising the following steps:

receiving, via uplink signals to the satellite, adaptation change information indicative of conditions for downlink channels in the downlink beam; and

changing said second inner coding rate based on said adaptation change information.

33. The method of claim 19, further comprising the following step:

selecting said second inner coding rate based on channel conditions of the downlink beam and independent of said first inner coding rate.