System and method of separately coding the header and payload of a data packet for use in satellite data communication

• US 6,263,466 B1
• Filed: 03/05/1998
• Issued: 07/17/2001
• Est. Priority Date: 03/05/1998
• Status: Expired due to Fees

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Teledesic, LLC (Michael J. Larson, MBA)
• Inventors: Million, Samson, Hinedi, Sami M., Griep, Karl R.
• Primary Examiner(s): Decady, Albert
• Assistant Examiner(s): Ton, David
• Application Number:
  US09/035,645
• Time in Patent Office: 1,230 Days
• Field of Search: 714/755, 342/357.16, 342/354, 244/158.R, 375/330, 375/341, 375/220, 370/349, 370/476, 370/389
• US Class Current: 714/755
• CPC Class Codes: H03M 13/2903 Methods and arrangements specifically for encoding, e.g. parallel encoding of a plurality of constituent codes
• CPC Class Codes: H03M 13/2933 using a block and a convolutional code H03M13/2957 takes precedence
• CPC Class Codes: H03M 13/2939 using convolutional codes H03M13/2957 takes precedence
• CPC Class Codes: H03M 13/47 Error detection, forward error correction or error protection, not provided for in groups H03M13/01 - H03M13/37
• CPC Class Codes: H03M 13/6513 Support of multiple code types, e.g. unified decoder for LDPC and turbo codes
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04L 1/0053 specially adapted for power saving
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 2001/0097 Relays
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A data communication system for a constellation of satellites (13a, 13b, . . . ) that employ Earth-fixed cellular beam management technology is disclosed. The data to be communicated is formed into data packets by a transmitting ground terminal (60). Each data packet includes a header (41) with control information and a payload (43) of data to be communicated. The information contained in the header is used to route the data packets through the satellite constellation to the appropriate intended satellite or to a downlink satellite (104). The header and payload databits are outer forward error correction (FEC) encoded (64, 70), optionally interleaved separately (66, 72), and inner error correction encoded by inner FEC encoders (68, 74). After receipt by an uplink satellite (62), processing of the header is accomplished to recover the header of the original signal. That information may then be used to identify and separate the payload into payload intended for the receiving satellite and payload not intended for the receiving satellite. If receiving satellite payload codewords are identified, the corresponding data is processed and used by the satellite. In one embodiment, a hard decision (102) is applied to the payload data packets that are not intended for use by the receiving satellite. In another embodiment, a hard decision is applied to all payload data. The information contained in the header is then used to route the data packets through the satellite constellation to the appropriate intended satellite or to a downlink satellite (104).

Claims

1. A data communication system for a communication network comprising a constellation of low-Earth orbit (LEO) satellites and ground terminals for sending data packets to and receiving data packets from the low-Earth orbit satellites forming said constellation, said data packets including header databits and payload databits, said header databits including information regarding the destination of the payload databits, said data communication system comprising:

a forward error correction (FEC) coding system located in said ground terminals for;

(i) separately outer FEC encoding the header and payload databits of said data packets;

(ii) separately inner FEC encoding said outer encoded header and payload codewords to produce concatenated coded header and payload codewords;

(iii) mixing said concatenated coded header and payload codewords to produce concatenated coded data packets; and

(iv) transmitting said concatenated coded data packets to one of said low-Earth orbit satellites;

an FEC decoding system located in said low-Earth orbit satellites for;

(i) receiving said concatenated coded data packets;

(ii) demixing said concatenated coded data packets to recover said concatenated coded header and payload codewords;

(iii) decoding said concatenated coded header codewords to recover said outer encoded header codewords;

(iv) outer decoding said header codewords to recover said header databits;

(v) separating said concatenated coded payload codewords to recover concatenated coded payload codewords intended for the satellite receiving said concatenated coded data packets;

(vi) decoding said concatenated coded payload codewords intended for the satellite receiving said concatenated coded data packets, but not other concatenated coded payload codewords, to recover outer encoded receiving satellite payload codewords;

(vii) outer decoding said receiving satellite payload codewords to recover said receiving satellite payload databits; and

(viii) making a hard decision on the bits of said other concatenated coded payload codewords;

an FEC coding system located in said low-Earth orbit satellites for;

(i) receiving from other satellites data packets comprising header databits and concatenated coded payload codewords intended for one of said ground terminals;

(ii) re-outer FEC encoding the header databits received from other satellites;

(iii) re-inner FEC encoding said re-outer encoded header codewords to produce re-concatenated coded header codewords;

(iv) mixing said re-concatenated coded header codewords and said concatenated coded payload codewords intended for one of said ground terminals to produce re-concatenated coded data packets; and

(v) transmitting said re-concatenated coded data packets to one of said ground terminals; and

an FEC decoding system located in said ground terminals for;

(i) receiving said re-concatenated coded data packets;

(ii) demixing said re-concatenated coded data packets to recover said re-concatenated coded header codewords and said concatenated coded payload codewords;

(iii) separately inner decoding said re-concatenated coded header codewords and said concatenated coded payload codewords to recover said re-outer encoded header and outer encoded payload codewords; and

(iv) separately outer decoding said header and payload codewords to recover said header and payload databits.

2. A data communication system as claimed in claim 1, wherein said FEC coding system located in said ground terminals includes:

a header outer encoder for outer FEC encoding the header databits of said data packets to produce outer encoded header codewords;

a payload outer encoder for outer FEC encoding the payload databits of said data packets to produce outer encoded payload codewords;

a header inner encoder for inner FEC encoding said outer encoded header codewords to produce said concatenated coded header codewords;

a payload inner encoder for inner FEC encoding said outer encoded payload codewords to produce said concatenated coded payload codewords; and

a mixer for mixing said concatenated coded header and payload codewords to produce concatenated coded data packets.

3. A data communication system as claimed in claim 2, wherein said FEC decoding system located in said low-Earth orbit satellites includes:

a demixer for demixing said concatenated coded data packets to recover said concatenated coded header and payload codewords;

a header inner decoder for inner decoding said concatenated coded header codewords to recover said outer encoded header codewords;

a header outer decoder for outer decoding said header codewords to recover said header databits;

a separator for separating said concatenated coded payload codewords to recover concatenated coded payload codewords intended for the satellite receiving said concatenated coded data packets and other concatenated coded payload codewords;

a payload inner decoder for decoding said concatenated coded payload codewords intended for the satellite receiving said concatenated coded data packets to recover said outer encoded satellite payload codewords;

a payload outer decoder for outer decoding the outer encoded satellite payload databits; and

a hard decision for forcing the bits of said other concatenated coded payload codewords to take on +1 or −

1 values.

4. A data communication system as claimed in claim 3, wherein said FEC coding system located in said low-Earth orbit satellites includes:

a header outer encoder for re-outer FEC encoding header databits received from other satellites to produce re-outer encoded header codewords;

a header inner encoder for re-inner FEC encoding said re-outer encoded header codewords to produce said re-concatenated coded header codewords; and

a mixer for mixing said re-concatenated coded header codewords and said concatenated coded payload codewords intended for one of said ground terminals to produce said re-concatenated coded data packets.

5. A data communication system as claimed in claim 4, wherein said FEC decoding system located in said ground terminals includes:

a demixer for demixing said re-concatenated coded data packets to recover said re-concatenated coded header codewords and said concatenated coded payload codewords;

a header inner decoder for decoding said re-concatenated coded header codewords to recover said re-outer encoded header codewords;

a payload inner decoder for decoding said concatenated coded payload codewords to recover said outer encoded payload codewords;

a header outer decoder for outer decoding the re-outer encoded header codewords to recover said header databits; and

a payload outer decoder for outer decoding said outer encoded payload codewords to recover said payload databits.

6. A data communication system as claimed in claim 5, wherein said FEC coding system located in said low-Earth orbit satellites also includes a payload inner encoder for applying a second inner code to the concatenated coded payload codewords intended for one of said ground terminals.

7. A data communication system as claimed in claim 6, wherein said FEC decoding system located in said ground terminals also includes a further payload inner decoder for removing said second inner coder applied to said concatenated coded payload codewords by said payload inner encoder located in said low-Earth orbit satellites.

8. A data communication system as claimed in claim 5, wherein said FEC coding system located in said low-Earth orbit satellites also includes a payload bit interleaver for bit interleaving said concatenated coded payload codewords intended for one of said ground terminals and a payload inner encoder for encoding the bit interleaved concatenated coded payload codewords intended for one of said ground terminals a second time.

9. A data communication system as claimed in claim 8, wherein said payload inner decoder located in said ground terminals is a serial concatenated convolutional code (SCCC) decoder.

10. A data communication system as claimed in claim 1, wherein said low-Earth orbit satellites forward data packets from satellite to satellite via intersatellite links and wherein said low-Earth orbit satellites also include an intersatellite coding and decoding system for:

(i) FEC intersatellite encoding of said recovered header databits and combining the resulting header codewords with said concatenated coded payload codewords prior to forwarding a data packet from one satellite to another satellite;

(ii) decombining said resulting header codewords from said concatenated coded payload codewords of forwarded data packets and, then, FEC decoding said resulting header codewords to recover said header databits; and

(iii) decoding said concatenated coded payload codewords intended for the satellite receiving said forwarded data packets, but not other concatenated coded payload codewords, to recover receiving satellite databits.

11. A data communication system as claimed in claim 10, wherein said low-Earth orbit satellites include:

an encoder for FEC intersatellite encoding said recovered header databits and producing resulting header codewords;

a combiner for combining said resulting header codewords with said concatenated coded payload codewords;

a decombiner for decombining said resulting header codewords from said concatenated coded payload codewords of forwarded data packets;

a decoder for decoding said resulting header codewords to receive said header databits;

a separator for separating concatenated coded payload codewords intended for the satellite receiving said forwarded data packets from other concatenated coded payload codewords;

a payload inner decoder for decoding said concatenated coded payload codewords intended for the satellite receiving said forwarded data packets to recover outer encoded receiving satellite payload codewords;

a payload outer decoder for outer decoding said outer encoded receiving satellite payload codewords; and

a hard decision circuit for making a hard decision on said other concatenated coded payload codewords.

12. A data communication system as claimed in claim 1, wherein:

said FEC coding system located in said ground terminals interleaves the symbols of the header and payload codewords resulting from outer FEC encoding the header and payload databits of said data packets;

said FEC decoding system located in said low-Earth orbit satellites;

(i) de-interleaves the symbols of the outer encoded header codewords after the outer encoded header codewords are recovered; and

(ii) de-interleaves the symbols of the outer encoded receiving satellite payload codewords after said outer encoded receiving satellite payload codewords are recovered;

said FEC coding system located in said low-Earth orbit satellites interleaves the symbols of the resulting header codewords prior to re-inner FEC coding said re-outer encoded header codewords to produce re-concatenated coded header codewords; and

said FEC decoding system located in said ground terminals de-interleaves said re-outer encoded header and outer encoded payload codewords.

13. A data communication system as claimed in claim 12, wherein said FEC coding system located in said ground terminals includes:

a header outer encoder for outer FEC encoding the header databits of said data packets to produce outer encoded header codewords;

a payload outer encoder for outer FEC encoding the payload databits of said data packets to produce outer encoded payload codewords;

a header interleaver for interleaving the symbols of said outer encoded header codewords;

a payload interleaver for interleaving the symbols of said outer encoded payload codewords;

a header inner encoder for inner FEC encoding interleaved, outer encoded header codewords to produce concatenated coded, interleaved header codewords;

a payload inner encoder for inner FEC encoding interleaved, outer encoded payload codewords to produce concatenated coded, interleaved payload codewords; and

a mixer for mixing said concatenated coded, interleaved header and payload codewords to produce concatenated coded, interleaved data packets.

14. A data communication system as claimed in claim 13, wherein said FEC decoding system located in said low-Earth orbit satellites includes:

a demixer for demixing said concatenated coded, interleaved data packets to recover said concatenated coded, interleaved header and payload codewords;

a header inner decoder for decoding said concatenated coded, interleaved header codewords to recover said interleaved, outer encoded header codewords;

a header de-interleaver for de-interleaving the symbols of said interleaved, outer encoded header codewords;

a header outer decoder for outer decoding said header codewords to recover said header databits;

a separator for separating said concatenated coded, interleaved payload codewords to recover concatenated coded, interleaved payload codewords intended for the satellite receiving said concatenated coded, interleaved data packets and other concatenated coded, interleaved payload codewords;

a payload inner decoder for decoding said concatenated coded, interleaved payload codewords intended for the satellite receiving said concatenated coded, interleaved data packets to recover said interleaved, outer encoded satellite payload codewords;

a payload de-interleaver for de-interleaving the symbols of said interleaved, outer encoded satellite payload codewords;

a payload outer decoder for outer decoding the outer encoded satellite payload databits; and

a hard decision for forcing the other bits of said concatenated coded, interleaved payload codewords to take on +1 or −

1 values.

15. A data communication system as claimed in claim 14, wherein said FEC coding system located in said low-Earth orbit satellites includes:

a header outer encoder for re-outer FEC encoding header databits received from other satellites to produce re-outer encoded header codewords;

a header interleaver for interleaving the symbols of said re-outer encoded header codewords;

a header inner encoder for re-inner FEC encoding said interleaved, re-outer encoded header codewords to produce said re-concatenated coded, interleaved header codewords; and

a mixer for mixing said re-concatenated coded, interleaved header codewords and said concatenated coded, interleaved payload codewords intended for one of said ground terminals to produce said re-concatenated coded, interleaved data packets.

16. A data communication system as claimed in claim 15, wherein said FEC decoding system located in said ground terminals includes:

a demixer for demixing said re-concatenated coded, interleaved data packets to recover said re-concatenated coded, interleaved header codewords and said concatenated coded, interleaved payload codewords;

a header inner decoder for decoding said re-concatenated coded, interleaved header codewords to recover said interleaved, re-outer encoded header codewords;

a payload inner decoder for decoding said concatenated coded, interleaved payload codewords to recover said interleaved, outer encoded payload codewords;

a header de-interleaver for de-interleaving the symbols of said interleaved, re-outer encoded header codewords;

a payload de-interleaver for de-interleaving the symbols of said interleaved, outer encoded payload codewords;

a header outer decoder for outer decoding the re-outer encoded header codewords to recover said header databits; and

a payload outer decoder for outer decoding said outer encoded payload codewords to recover said payload databits.

17. A data communication system as claimed in claim 16, wherein said FEC coding system located in said low-Earth orbit satellites also includes a payload inner encoder for applying a second inner code to the concatenated coded, interleaved payload codewords intended for one of said ground terminals.

18. A data communication system as claimed in claim 17, wherein said FEC decoding system located in said ground terminals also includes a further payload inner decoder for removing said second inner coder applied to said concatenated coded, interleaved payload codewords by said payload inner encoder located in said low-Earth orbit satellites.

19. A data communication system as claimed in claim 16, wherein said FEC coding system located in said low-Earth orbit satellites also includes a payload bit interleaver for bit interleaving said concatenated coded, interleaved payload codewords intended for one of said ground terminals and a payload inner encoder for encoding the bit interleaved concatenated coded, interleaved payload codewords intended for one of said ground terminals a second time.

20. A data communication system as claimed in claim 19, wherein said payload inner decoder located in said ground terminals is a serial concatenated convolutional code (SCCC) decoder.

21. A data communication system as claimed in claim 12, wherein said low-Earth orbit satellites forward data packets from satellite to satellite via intersatellite links and wherein said low-Earth orbit satellites also include an intersatellite coding and decoding system for:

(i) FEC intersatellite encoding of said recovered header databits and combining the resulting header codewords with concatenated coded, interleaved payload codewords prior to forwarding a data packet from one satellite to another satellite;

(ii) decombining said resulting header codewords from said concatenated coded, interleaved payload codewords of forwarded data packets and, then, FEC decoding said resulting header codewords to recover said header databits; and

(iii) decoding and de-interleaving said concatenated coded, interleaved payload codewords intended for the satellite receiving said forwarded data packets, but not other concatenated coded, interleaved payload codewords, to recover receiving satellite databits.

22. A data communication system as claimed in claim 21, wherein said low-Earth orbit satellites include:

an encoder for FEC intersatellite encoding said recovered header databits and producing resulting header codewords;

a combiner for combining said resulting header codewords with said concatenated coded, interleaved payload codewords;

a decombiner for decombining said resulting header codewords from said concatenated coded, interleaved payload codewords of forwarded data packets;

a decoder for decoding said resulting header codewords to receive said header databits;

a separator for separating concatenated coded, interleaved payload codewords intended for the satellite receiving said forwarded data packets from other concatenated coded, interleaved payload codewords;

a payload inner decoder for decoding said concatenated coded, interleaved payload codewords intended for the satellite receiving said forwarded data packets to recover outer encoded, interleaved receiving satellite payload codewords;

a payload de-interleaver for de-interleaving the symbols of said recovered outer encoded, interleaved receiving satellite payload codewords;

a payload outer decoder for outer decoding said outer encoded receiving satellite payload codewords; and

a hard decision circuit for making a hard decision on said other concatenated coded payload codewords.

23. A data communication system for a communication network comprising a constellation of low-Earth orbit (LEO) satellites and ground terminals for sending data packets to and receiving data packets from the low-Earth orbit satellites forming said constellation, said data packets including header databits and payload databits, said header databits including information regarding the destination of the payload databits, said data communication system comprising:

a forward error correction (FEC) coding system located in said ground terminals for;

(i) separately outer FEC encoding the header and payload databits of said data packets;

(ii) separately inner FEC encoding said outer encoded header and payload codewords to produce concatenated coded header and payload codewords;

(iii) mixing said concatenated coded header and payload codewords to produce concatenated coded data packets; and

(iv) transmitting said concatenated coded data packets to one of said low-Earth orbit satellites;

an FEC decoding system located in said low-Earth orbit satellites for;

(i) receiving said concatenated coded data packets;

(ii) demixing said concatenated coded data packets to recover said concatenated coded header and payload codewords;

(iii) decoding said concatenated coded header codewords to recover said outer encoded header codewords;

(iv) outer decoding said header codewords to recover said header databits; and

(v) making a hard decision on the bits of, but not decoding, said concatenated coded payload codewords;

an FEC coding system located in said low-Earth orbit satellites for;

(i) receiving from other satellites data packets comprising header databits and concatenated coded payload codewords;

(ii) re-outer FEC encoding the header databits received from other satellites;

(iii) re-inner FEC encoding said re-outer encoded header codewords to produce re-concatenated coded header codewords;

(iv) mixing said re-concatenated coded header codewords and said concatenated coded payload codewords to produce re-concatenated coded data packets; and

(v) transmitting said re-concatenated coded data packets to one of said ground terminals; and

an FEC decoding system located in said ground terminals for;

(i) receiving said re-concatenated coded data packets;

(ii) demixing said re-concatenated coded data packets to recover said re-concatenated coded header codewords and said concatenated coded payload codewords;

(iii) separately inner decoding said re-concatenated coded header codewords and said concatenated coded payload codewords to recover said re-outer encoded header and outer encoded payload codewords; and

(iv) separately outer decoding said header and payload codewords to recover said header and payload databits.

24. A data communication system as claimed in claim 23, wherein said FEC coding system located in said ground terminals includes:

a header outer encoder for outer FEC encoding the header databits of said data packets to produce outer encoded header codewords;

a payload outer encoder for outer FEC encoding the payload databits of said data packets to produce outer encoded payload codewords;

a header inner encoder for inner FEC encoding said outer encoded header codewords to produce said concatenated coded header codewords;

a payload inner encoder for inner FEC encoding said outer encoded payload codewords to produce said concatenated coded payload codewords; and

a mixer for mixing said concatenated coded header and payload codewords to produce concatenated coded data packets.

25. A data communication system as claimed in claim 24, wherein said FEC decoding system located in said low-Earth orbit satellites includes:

a demixer for demixing said concatenated coded data packets to recover said concatenated coded header and payload codewords;

a header inner decoder for decoding said concatenated coded header codewords to recover said outer encoded header codewords;

a header outer decoder for outer decoding said header codewords to recover said header databits; and

a hard decision for forcing the bits of said concatenated coded payload codewords to take on +1 or −

1 values.

26. A data communication system as claimed in claim 25, wherein said FEC coding system located in said low-Earth orbit satellites includes:

a header outer encoder for re-outer FEC encoding header databits received from other satellites to produce re-outer encoded header codewords;

a header inner encoder for re-inner FEC encoding said re-outer encoded header codewords to produce said re-concatenated coded header codewords; and

a mixer for mixing said re-concatenated coded header codewords and said concatenated coded payload codewords to produce said re-concatenated coded data packets.

27. A data communication system as claimed in claim 26, wherein said FEC decoding system located in said ground terminals includes:

a demixer for demixing said re-concatenated coded data packets to recover said re-concatenated coded header codewords and said concatenated coded payload codewords;

a header inner decoder for decoding said re-concatenated coded header codewords to recover said re-outer encoded header codewords;

a payload inner decoder for decoding said concatenated coded payload codewords to recover said outer encoded payload codewords;

a header outer decoder for outer decoding the re-outer encoded header codewords to recover said header databits; and

a payload outer decoder for outer decoding said outer encoded payload codewords to recover said payload databits.

28. A data communication system as claimed in claim 27, wherein said FEC coding system located in said low-Earth orbit satellites also includes a payload inner encoder for applying a second inner code to the concatenated coded payload codewords intended for one of said ground terminals.

29. A data communication system as claimed in claim 28, wherein said FEC decoding system located in said ground terminals also includes a further payload inner decoder for removing said second inner coder applied to said concatenated coded payload codewords by said payload inner encoder located in said low-Earth orbit satellites.

30. A data communication system as claimed in claim 27, wherein said FEC coding system located in said low-Earth orbit satellites also includes a payload bit interleaver for bit interleaving said concatenated coded payload codewords intended for one of said ground terminals and a payload inner encoder for encoding the bit interleaved concatenated coded payload codewords intended for one of said ground terminals a second time.

31. A data communication system as claimed in claim 30, wherein said payload inner decoder located in said ground terminals is a serial concatenated convolutional code (SCCC) decoder.

32. A data communication system as claimed in claim 23, wherein said low-Earth orbit satellites forward data packets from satellite to satellite via intersatellite links and wherein said low-Earth orbit satellites also include an intersatellite coding and decoding system for:

(i) FEC intersatellite encoding of said recovered header databits and combining the resulting header codewords with said concatenated coded payload codewords prior to forwarding a data packet from one satellite to another satellite; and

(ii) decombining said resulting header codewords from said concatenated coded payload codewords of forwarded data packets and, then, FEC decoding said resulting header codewords to recover said header databits.

33. A data communication system as claimed in claim 32, where said low-Earth orbit satellites include a hard decision circuit for making a hard decision on said concatenated coded payload codewords forwarded from one satellite to another satellite prior to forwarding data packets from one satellite to another satellite.

34. A data communication system as claimed in claim 23, wherein:

said FEC coding system located in said ground terminals interleaves the symbols of the header and payload codewords resulting from outer FEC encoding the header and payload databits of said data packets;

said FEC decoding system located in said low-Earth orbit satellites;

(i) de-interleaves the symbols of the outer encoded header codewords after the outer encoded header codewords are recovered; and

(ii) de-interleaves the symbols of the outer encoded receiving satellite payload codewords after said outer encoded receiving satellite payload codewords are recovered;

said FEC coding system located in said low-Earth orbit satellites interleaves the symbols of the resulting header codewords prior to re-inner FEC coding said re-outer encoded header codewords to produce re-concatenated coded header codewords; and

said FEC decoding system located in said ground terminals de-interleave said re-outer encoded header and outer encoded payload codewords.

35. A data communication system as claimed in claim 34, wherein said FEC coding system located in said ground terminals includes:

a header outer encoder for outer FEC encoding the header databits of said data packets to produce outer encoded header codewords;

a payload outer encoder for outer FEC encoding the payload databits of said data packets to produce outer encoded payload codewords;

a header interleaver for interleaving the symbols of said outer encoded header codewords;

a payload interleaver for interleaving the symbols of said outer encoded payload codewords;

a header inner encoder for inner FEC encoding interleaved, outer encoded header codewords to produce concatenated coded, interleaved header codewords;

a payload inner encoder for inner FEC encoding interleaved, outer encoded payload codewords to produce said concatenated coded, interleaved payload codewords; and

a mixer for mixing said concatenated coded, interleaved header and payload codewords to produce concatenated coded, interleaved data packets.

36. A data communication system as claimed in claim 35, wherein said FEC decoding system located in said low-Earth orbit satellites includes:

a demixer for demixing said concatenated coded, interleaved data packets to recover said concatenated coded, interleaved header and payload codewords;

a header inner decoder for decoding said concatenated coded, interleaved header codewords to recover said interleaved, outer encoded header codewords;

a header de-interleaver for de-interleaving the symbols of said interleaved, outer encoded header codewords;

a header outer decoder for outer decoding said header codewords to recover said header databits; and

a hard decision for forcing the bits of said concatenated coded, interleaved payload codewords to take on +1 or −

1 values.

37. A data communication system as claimed in claim 36, wherein said FEC coding system located in said low-Earth orbit satellites includes:

a header outer encoder for re-outer FEC encoding header databits received from other satellites to produce re-outer encoded header codewords;

a header interleaver for interleaving the symbols of said re-outer encoded header codewords;

a header inner encoder for re-inner FEC encoding said interleaved, re-outer encoded header codewords to produce said re-concatenated coded, interleaved header codewords; and

a mixer for mixing said re-concatenated coded, interleaved header codewords and said concatenated coded, interleaved payload codewords to produce said re-concatenated coded, interleaved data packets.

38. A data communication system as claimed in claim 37, wherein said FEC decoding system located in said ground terminals includes:

a demixer for demixing said re-concatenated coded, interleaved data packets to recover said re-concatenated coded, interleaved header codewords and said concatenated coded, interleaved payload codewords;

a header inner decoder for decoding said re-concatenated coded, interleaved header codewords to recover said interleaved, re-outer encoded header codewords;

a payload inner decoder for decoding said concatenated coded, interleaved payload codewords to recover said interleaved, outer encoded payload codewords;

a header de-interleaver for de-interleaving the symbols of said interleaved, re-outer encoded header codewords;

a payload de-interleaver for de-interleaving the symbols of said interleaved, outer encoded payload codewords;

a header outer decoder for outer decoding the re-outer encoded header codewords to recover said header databits; and

a payload outer decoder for outer decoding said outer encoded payload codewords to recover said payload databits.

39. A data communication system as claimed in claim 38, wherein said FEC coding system located in said low-Earth orbit satellites also includes a payload inner encoder for applying a second inner code to the concatenated coded, interleaved payload codewords intended for one of said ground terminals.

40. A data communication system as claimed in claim 39, wherein said FEC decoding system located in said ground terminals also includes a further payload inner decoder for removing said second inner coder applied to said concatenated coded, interleaved payload codewords by said payload inner encoder located in said low-Earth orbit satellites.

41. A data communication system as claimed in claim 38, wherein said FEC coding system located in said low-Earth orbit satellites also includes a payload bit interleaver for bit interleaving said concatenated coded, interleaved payload codewords intended for one of said ground terminals and a payload inner encoder for encoding the bit interleaved concatenated coded, interleaved payload codewords intended for one of said ground terminals a second time.

42. A data communication system as claimed in claim 41, wherein said payload inner decoder located in said ground terminals is a serial concatenated convolutional code (SCCC) decoder.

43. A data communication system as claimed in claim 34, wherein said low-Earth orbit satellites forward data packets from satellite to satellite via intersatellite links and wherein said low-Earth orbit satellites also include an intersatellite coding and decoding system for:

(i) FEC intersatellite encoding of said recovered header databits and combining the resulting header codewords with said concatenated coded, interleaved payload codewords prior to forwarding a data packet from one satellite to another satellite; and

(ii) decombining said resulting header codewords from said concatenated coded, interleaved payload codewords of forwarded data packets and, then, FEC decoding said resulting header codewords to recover said header databits.

44. A data communication system as claimed in claim 43, where said low-Earth orbit satellites include a hard decision circuit for making a hard decision on said concatenated coded, interleaved payload codewords forwarded from one satellite to another satellite prior to forwarding data packets from one satellite to another satellite.

45. A data communication method for a communication network comprising a constellation of low-Earth orbit (LEO) satellites and a plurality of ground stations for transmitting data packets to and receiving data packets from said low-Earth orbit satellites forming said constellation, said data packets including header databits and payload databits, said header databits including information regarding the destination of the payload databits, said method comprising:

forward error correction (FEC) coding data packets to be transmitted by said ground terminals to one of said LEO satellites prior to transmission by;

(i) separately outer FEC encoding the header and payload databits of said data packets;

(ii) separately inner FEC encoding said outer encoded header and payload codewords to produce concatenated coded header and payload codewords; and

(iii) mixing said concatenated coded header and payload codewords to produce concatenated coded data packets;

transmitting said concatenated coded data packets to one of said LEO satellites;

receiving said concatenated coded data packets at one of said LEO satellites;

FEC decoding said concatenated coded data packets at said one of said LEO satellites by;

(i) demixing said concatenated coded data packets to recover said concatenated coded header and payload codewords;

(ii) inner decoding said concatenated coded header codewords to recover said outer encoded header codewords, (iii) outer decoding said header codewords to recover said header databits;

(iv) separating said concatenate d coded payload data packets to recover concatenated coded payload codewords intended for the satellite receiving said concatenated coded data packets;

(v) inner decoding said concatenated coded payload codewords intended for the satellite receiving said concatenated coded data packets, but not other concatenated coded payload codewords, to recover outer encoded receiving satellite payload codewords;

(vi) outer decoding said receiving satellite payload codewords to recover said receiving satellite payload databits; and

(vii) making a hard decision on the bits of said other coded payload codewords; and

conveying said header databits and said other concatenated coded payload codewords through said constellation of LEO satellites to another of said LEO satellites.

46. A data communication method as claimed in claim 45, wherein said method includes:

FEC coding said header databits at said other satellite by;

(i) re-outer FEC encoding the header databits;

(ii) re-inner FEC encoding said re-outer encoded header codewords to produce re-concatenated coded header codewords; and

(iii) mixing said re-concatenated coded header codewords and said concatenated coded payload codewords intended for one of said ground terminals to produce re-concatenated coded data packets;

transmitting said re-concatenated coded data packets to a ground terminal;

receiving said re-concatenated coded data packets at a ground terminal; and

FEC decoding said re-concatenated coded data packets at said ground terminal by;

(i) demixing said re-concatenated coded data packets to recover said re-concatenated coded header codewords and concatenated coded payload codewords;

(ii) inner decoding said re-concatenated coded header codewords and said concatenated coded payload codewords to recover said re-outer encoded header and outer encoded payload codewords;

(iii) outer decoding said header and payload codewords to recover said header and payload databits.

47. A data communication method as claimed in claim 46, wherein said method includes second inner encoding said concatenated coded payload codewords intended for one of said ground terminals at said other satellite prior to mixing said re-concatenated coded header codewords with said double inner concatenated coded payload codewords.

48. A data communication method as claimed in claim 47, wherein said double inner concatenated coded payload codewords are inner decoded twice at said ground terminal prior to outer decoding said concatenated coded payload codewords.

49. A data communication method as claimed in claim 46, wherein said method includes bit interleaving and second inner encoding said concatenated coded payload codewords intended for one of said ground terminals at said other satellite prior to mixing the re-concatenated coded header codewords with said bit interleaved double inner concatenated coded payload codewords.

50. A data communication method as claimed in claim 49, wherein said inner decoding of said bit interleaved double inner concatenated coded payload data packets at said ground terminal is accomplished by a serial concatenated convolutional code (SCCC) decoder.

51. A data communication method as claimed in claim 46, wherein said low-Earth orbit satellites forward data packets from satellite to satellite and wherein said method includes:

(i) intersatellite FEC encoding said recovered header databits and combining the resulting header codewords with said concatenated coded payload codewords prior to forwarding a data packet from one satellite to another satellite;

(ii) decombining said resulting header codewords from said concatenated coded payload codewords of forwarded data packets and, then, decoding said resulting header codewords to recover said header databits; and

(iii) decoding said concatenated coded payload codewords intended for the satellite receiving said forwarded data packets, but not other concatenated coded payload codewords to recover receiving satellite databits.

52. A data communication method as claimed in claim 51, wherein said method includes:

FEC intersatellite encoding said recovered header databits to produce resulting header codewords;

combining said resulting header codewords with said concatenated coded payload codewords;

decombining said resulting header codewords from said concatenated coded payload codewords of forwarded data packets;

decoding said resulting header codewords to recover said header databits;

separating said concatenated coded payload codewords intended for the satellite receiving said forwarded data packets from other concatenated coded payload codewords;

inner decoding said concatenated coded payload codewords intended for the satellite receiving said forwarded data packets to recover outer encoded receiving satellite payload codewords;

outer decoding said outer encoded receiving satellite payload codewords; and

making an intersatellite hard decision on said other concatenated coded payload codewords.

53. A data communications method as claimed in claim 46, wherein:

the symbols of said header and payload codewords resulting from said outer encoding of said header and payload databits of said data packets are interleaved;

the symbols of the outer encoded header codewords are de-interleaved after the outer encoded header codewords are recovered and the symbols of the outer encoded receiving satellite payload codewords are de-interleaved after the outer encoded receiving satellite payload codewords are recovered;

the symbols of the resulting header codewords are interleaved prior to re-inner FEC coding said re-outer encoded header codewords to produce re-concatenated coded header codewords; and

the symbols of the re-outer encoded header and outer encoded payload codewords are de-interleaved after the re-outer encoded header and outer encoded payload codewords are recovered.

54. A data communication method as claimed in claim 53, wherein said method includes second inner encoding concatenated coded, interleaved payload codewords intended for one of said ground terminals at said other satellite prior to mixing re-concatenated coded, interleaved header codewords with the resulting double inner concatenated coded, interleaved payload codewords.

55. A data communication method as claimed in claim 54, wherein said double inner concatenated coded, interleaved payload codewords are inner decoded twice at said ground terminal prior to de-interleaving and outer decoding said concatenated coded, interleaved payload codewords.

56. A data communication method as claimed in claim 53, wherein said method includes bit interleaving and second inner encoding said concatenated coded, interleaved payload codewords intended for one of said ground terminals at said other satellite prior to mixing the re-concatenated coded, interleaved header codewords with the resulting bit interleaved double inner concatenated coded, interleaved payload codewords.

57. A data communication method as claimed in claim 56, wherein said inner decoding of said bit interleaved double inner concatenated coded, interleaved payload data packets at said ground terminal is accomplished by a serial concatenated convolutional code (SCCC) decoder.

58. A data communication method as claimed in claim 53, wherein said low-Earth orbit satellites forward data packets from satellite to satellite and wherein said method includes:

(i) intersatellite FEC encoding said recovered header databits and combining the resulting header codewords with concatenated coded, interleaved payload codewords prior to forwarding a data packet from one satellite to another satellite;

(ii) decombining said resulting header codewords from said concatenated coded, interleaved payload codewords of forwarded data packets and, then, decoding said resulting header codewords to recover said header databits; and

(iii) decoding and de-interleaving said concatenated coded, interleaved payload codewords intended for the satellite receiving said forwarded data packets, but not other concatenated coded, interleaved payload codewords, to recover receiving satellite databits.

59. A data communication method as claimed in claim 58, wherein said method includes:

FEC intersatellite encoding said recovered header databits to produce resulting header codewords;

combining said resulting header codewords with said concatenated coded, interleaved payload codewords;

decombining said resulting header codewords from said concatenated coded, interleaved payload codewords of forwarded data packets;

decoding said resulting header codewords to recover said header databits;

separating said concatenated coded, interleaved payload codewords intended for the satellite receiving said forwarded data packets from other concatenated coded, interleaved payload codewords;

inner decoding said concatenated coded, interleaved payload codewords intended for the satellite receiving said forwarded data packets to recover outer encoded, interleaved receiving satellite payload codewords;

de-interleaving said outer encoded, interleaved receiving satellite payload codewords to recover outer encoded receiving satellite payload codewords;

outer decoding said outer encoded receiving satellite payload codewords; and

making an intersatellite hard decision on said other concatenated coded, interleaved payload codewords.

60. A data communication method for a communication network comprising a constellation of low-Earth orbit (LEO) satellites and a plurality of ground stations for transmitting data packets to and receiving data packets from said low-Earth orbit satellites forming said constellation, said data packets including header databits and payload databits, said header databits including information regarding the destination of the payload databits, said method comprising:

forward error correction (FEC) coding data packets to be transmitted by said ground terminals to one of said LEO satellites prior to transmission by;

(i) separately outer FEC encoding the header and payload databits of said data packets;

(ii) separately inner FEC encoding said outer encoded header and payload codewords to produce concatenated coded header and payload codewords; and

(iii) mixing said concatenated coded header and payload codewords to produce concatenated coded data packets;

transmitting said concatenated coded data packets to one of said LEO satellites;

receiving said concatenated coded data packets at one of said LEO satellites;

FEC decoding said concatenated coded data packets at said one of said LEO satellites by;

(i) demixing said concatenated coded data packets to recover said concatenated coded header and payload codewords;

(ii) inner decoding said concatenated coded header codewords to recover said outer encoded header codewords;

(iii) outer decoding said header codewords to recover said header databits; and

(iv) making a hard decision on the bits of, but not decoding, said concatenated coded payload codewords; and

conveying said header databits and said concatenated coded payload codewords through said constellation of LEO satellites to another of said LEO satellites.

61. A data communication method as claimed in claim 60, wherein said method includes:

FEC coding said header databits at said other satellite by;

(i) re-outer FEC encoding the header databits;

(ii) re-inner FEC encoding said re-outer encoded header codewords to produce re-concatenated coded header codewords; and

(iv) mixing said re-concatenated coded header codewords in said concatenated coded payload codewords to produce re-concatenated coded data packets;

transmitting said re-concatenated coded data packets to a ground terminal;

receiving said re-concatenated coded data packets at a ground terminal; and

FEC decoding said re-concatenated coded data packets at said ground terminal by;

(i) demixing said re-concatenated coded data packets to recover said re-concatenated coded header codewords and concatenated coded payload codewords;

(ii) inner decoding said re-concatenated coded header codewords and concatenated coded payload codewords to recover said re-outer encoded header and outer encoded payload codewords; and

(iii) outer decoding said header and payload codewords to recover said header and payload databits.

62. A data communication method as claimed in claim 61, wherein said method includes second inner encoding said concatenated coded payload codewords intended for one of said ground terminals at said other satellite prior to mixing said re-concatenated coded header codewords with the resulting double inner concatenated coded payload codewords.

63. A data communication method as claimed in claim 62, wherein said double inner concatenated coded payload codewords are inner decoded twice at said ground terminal prior to outer decoding said concatenated coded payload codewords.

64. A data communication method as claimed in claim 61, wherein said method includes bit interleaving and second inner encoding said concatenated coded payload codewords intended for one of said ground terminals at said other satellite prior to mixing the re-concatenated coded header codewords with the resulting bit interleaved double inner concatenated coded payload codewords.

65. A data communication method as claimed in claim 64, wherein said inner decoding of said bit interleaved double inner concatenated coded payload data packets at said ground terminal is accomplished by a serial concatenated convolutional code (SCCC) decoder.

66. A data communication method as claimed in claim 61, wherein said low-Earth orbit satellites forward data packets from satellite to satellite and wherein said method includes:

(i) intersatellite FEC encoding said recovered header databits and combining the resulting header codewords with said concatenated coded payload codewords prior to forwarding data packets from one satellite to another satellite; and

(ii) decombining said resulting header codewords from said concatenated coded payload codewords of forwarded data packets and, then, decoding said resulting header codewords to recover said header databits.

67. A data communication method as claimed in claim 66, wherein said method includes making an intersatellite hard decision on said concatenated coded payload codewords forwarded from one satellite to another satellite prior to forwarding data packets from one satellite to another satellite.

68. A data communications method as claimed in claim 61, wherein:

the symbols of said header and payload codewords resulting from said outer encoding of said header and payload databits of said data packets are interleaved;

the symbols of the outer encoded header codewords are de-interleaved after the outer encoded header codewords are recovered and the symbols of the outer encoded receiving satellite payload codewords are de-interleaved after the outer encoded receiving satellite payload codewords are recovered;

the symbols of the resulting header codewords are interleaved prior to re-inner FEC coding said re-outer encoded header codewords to produce re-concatenated coded header codewords; and

the symbols of the re-outer encoded header and outer encoded payload codewords are de-interleaved after the re-outer encoded header and outer encoded payload codewords are recovered.

69. A data communication method as claimed in claim 68, wherein said method includes second inner encoding said concatenated coded, interleaved payload codewords intended for one of said ground terminals at said other satellite prior to mixing said re-concatenated coded, interleaved header codewords with the resulting double inner concatenated coded, interleaved payload codewords.

70. A data communication method as claimed in claim 69, wherein said double inner concatenated coded, interleaved payload codewords are inner decoded twice at said ground terminal prior to de-interleaving and outer decoding said concatenated coded, interleaved payload codewords.

71. A data communication method as claimed in claim 68, wherein said method includes bit interleaving and second inner encoding said concatenated coded, interleaved payload codewords intended for one of said ground terminals at said other satellite prior to mixing the re-concatenated coded, interleaved header codewords with the resulting bit interleaved double inner concatenated coded, interleaved payload codewords.

72. A data communication method as claimed in claim 71, wherein said inner decoding of said bit interleaved double inner concatenated coded, interleaved payload data packets at said ground terminal is accomplished by a serial concatenated convolutional code (SCCC) decoder.

73. A data communication method as claimed in claim 68, wherein said low-Earth orbit satellites forward data packets from satellite to satellite and wherein said method includes:

(i) intersatellite FEC encoding said recovered header databits and combining the resulting header codewords with said concatenated coded, interleaved payload codewords prior to forwarding a data packet from one satellite to another satellite; and

(ii) decombining said resulting header codewords from said concatenated coded, interleaved payload codewords of forwarded data packets and, then, decoding said resulting header codewords to recover said header databits.

74. A data communication method as claimed in claim 73, wherein said method includes making an intersatellite hard decision on said concatenated coded, interleaved payload codewords forwarded from one satellite to another satellite prior to forwarding data packets from one satellite to another satellite.