Methods and systems for enhanced detection of e-Navigation messages
Methods and systems for enhancing the detectability of maritime e-Navigation messages are provided. Transmitters apply error protection encoding to the payload portion of messages to be transmitted, which are wrapped in a standard e-Navigation message format such as that used by the Automatic Identification System. Transmitted messages are received by a satellite or other surveillance platform employing a compatible radio frequency receiver to collect message signals over a large area or great distance. Candidate messages are identified and the error protection encoding decoded to recover messages.
1. A method of generating an e-Navigation message with enhanced detectability, the method comprising:
generating a binary payload;
error protection encoding the binary payload; and
encapsulating the binary payload in a message wrapper to produce the e-Navigation message.
2. The method of claim 1 , wherein the error protection encoding is selected from one or more of the group consisting of block coding the binary payload, convolutional coding the binary payload and interleaving the binary payload.
3. The method of claim 1 , wherein an error protection scheme used in the error protection encoding is selected from one or more of the group consisting of Low Density Parity Check coding, Turbo coding, Bose-Chaudhuri-Hocquenghem coding, and Reed-Solomon coding.
4. The method of claim 1 , wherein the error protection encoding comprises joint coding and modulation.
5. The method of claim 1 , wherein the message wrapper and the binary payload form one or more standards-compliant AIS messages.
6. The method of claim 5 , wherein each of the one or more standards-compliant AIS messages has a variable length.
7. A method of recovering message data from an e-Navigation signal, wherein the message data is encoded with error protection encoding, the method comprising:
receiving input signal data, the input signal data having been produced by demodulating and decoding the e-Navigation signal;
identifying a candidate message in the input signal data;
extracting a binary payload from the candidate message, the binary payload comprising at least one error protection encoding; and
decoding the at least one error protection encoding of the binary payload to recover the message data.
8. The method of claim 7 , wherein the candidate message contains one or more bit errors.
9. The method of claim 7 , wherein the at least one error protection comprises interleaving, and wherein the decoding comprises de-interleaving the binary payload.
10. The method of claim 7 , wherein the at least one error protection comprises convolutional coding, and wherein the decoding comprises Viterbi decoding.
11. The method of claim 7 , wherein the at least one error protection comprises block coding, and wherein the decoding comprises block decoding.
12. The method of claim 7 , wherein the at least one error protection is selected from one or more of the group consisting of Low Density Parity Check coding, Turbo coding, Bose-Chaudhuri-Hocquenghem coding, and Reed-Solomon coding.
13. The method of claim 7 , wherein the candidate message is identified by correlating at least a portion of the candidate message to a predetermined sequence.
14. The method of claim 13 , wherein the predetermined sequence is selected from one or more of the group consisting of an AIS training sequence, an AIS start flag, and an AIS end flag.
15. The method of claim 7 , wherein the binary payload is extracted using a predetermined bit offset within the candidate message.
16. The method of claim 7 , wherein the candidate message is one or more standards-compliant AIS messages.
17. The method of claim 16 , wherein each of the one or more standards-compliant AIS messages has a variable length.
18. A transponder for generating and transmitting an e-Navigation signal comprising an e-Navigation message with enhanced detectability, the transponder comprising:
a message data module configured to receive message data to be transmitted, and generate a binary payload based on the message data;
an error protection module configured to encode the binary payload using at least one error protection scheme; and
a message formatting module configured to encapsulate the binary payload in a message wrapper of the e-Navigation message.
19. A receiver for recovering message data from an e-Navigation signal, wherein the e-Navigation signal comprises an e-Navigation message with enhanced detectability, the receiver comprising:
a message processing module configured to identify a candidate message in input signal data, the input signal data having been produced by demodulating and decoding the e-Navigation signal;
a payload processing module configured to:
extract a binary payload from the candidate message, the binary payload having at least one error protection scheme; and
decode the at least one error protection encoding scheme of the binary payload to recover the message data.
20. An e-Navigation messaging system comprising:
a transponder for generating and transmitting an e-Navigation signal comprising an e-Navigation message with enhanced detectability, the transponder comprising:
a message data module configured to receive message data to be transmitted, and generate a binary payload based on the message data;
an error protection module configured to encode the binary payload using at least one error protection scheme; and
a message formatting module configured to encapsulate the binary payload in a message wrapper of the e-Navigation message; and
a receiver for recovering the message data from the e-Navigation signal, the receiver comprising:
a message processing module configured to identify a candidate message in input signal data, the input signal data having been produced by demodulating and decoding the e-Navigation signal;
a payload processing module configured to:
extract the binary payload from the candidate message, the binary payload having the at least one error protection scheme; and
decode the at least one error protection encoding scheme of the binary payload to recover the message data.