Low-latency, low-overhead data framing method for capacity-limited delay-sensitive long distance communication
A communication method is configured to increase speed of messages reception over a bandwidth limited channel such as high frequency (HF) radio. User data arriving from a high-speed network is transformed into a format suitable for transmission over the radio channel. Message packets that will take longer to reach a destination via the radio channel as compared to alternative channels, such as a fiber optic network, are rejected for radio transmission. When the packet is received, the receiver deduces message length by using information from various error handling techniques, such as forward error correction (FEC) and cyclic redundancy check (CRC) techniques. Fill data is transmitted between message packets when no data is available. The FEC and CRC information for the fill data is modified so that the fill data will fail FEC and CRC checks at the receiving station.
1. A method, comprising:
receiving a message from a primary communication channel at a receiving station;
wherein said receiving the message includes receiving the message through a message data stream;
wherein the message data stream includes user data and fill data;
wherein the user data has been encoded in accordance with a parity check code and an error correction scheme;
wherein the fill data has been encoded in accordance with the parity check code and the error correction scheme;
wherein the till data has been modified to fail a parity check code test;
maintaining a signal lock on the message data stream through the fill data;
detecting a message boundary of the message through the parity check code in combination with the error correction scheme;
wherein said detecting the message boundary includes determining with the receiving station that the fill data has failed the parity check code test; and
wherein said detecting the message boundary includes decoding with the receiving station the user data successfully through the parity check code and the error correction scheme.
2. The method of claim 1 , wherein the primary communication channel includes a low bandwidth, low latency communication link.
3. The method of claim 2 , wherein the primary communication channel includes a high frequency radio channel.
4. The method of claim 1 , wherein the user data is encoded in an asynchronous manner in the message data stream.
5. The method of claim 1 , wherein the fill data includes a pseudorandom binary sequence (PRBS).
6. The method of claim 5 , wherein the fill data includes a version of the PRBS modified by the parity check code and the error correction scheme.
7. The method of claim 6 , further comprising:
detecting a false message with the version of the PRBS.
8. The method of claim 7 , wherein the version of the PRBS has been modified to fail a parity check code test.
9. The method of claim 7 , wherein the version of the PRBS has been modified to fail an error correction scheme test.
10. The method of claim 1 , wherein the parity check code includes a checksum.
11. The method of claim 1 , wherein the parity check code includes a cyclic redundancy check (CRC).
12. The method of claim 1 , wherein the error correction scheme includes forward error correction (FEC).
13. The method of claim 1 , wherein the error correction scheme includes a convolution code scheme.
14. The method of claim 13 , wherein the error correction scheme includes a tail-biting Viterbi decoding algorithm.
15. The method of claim 1 , wherein the error correction scheme includes a block code scheme.
16. The method of claim 15 , wherein the error correction scheme includes a turbo block code scheme.
17. A method, comprising:
encoding a message data stream with user data and fill data;
modifying the fill data to reduce a chance of false message detection;
encoding the message data stream with a parity check code in combination with an error correction scheme;
creating a modified version of the fill data in which the modified version fails a test for the parity check code;
wherein the user data is unmodified to pass a parity test and error correction test; and
transmitting the message data stream from a transmission station.
18. The method of claim 17 , further comprising:
creating a modified version of the fill data in which the modified version fails a test for the error correction scheme.
19. The method of claim 17 , wherein the fill data includes a pseudorandom binary sequence (PRBS).
20. The method of claim 19 , wherein the fill data includes a version of the PRBS modified by the parity check code and the error correction scheme.
21. The method of claim 19 , wherein the parity check code includes a checksum.
22. The method of claim 19 , wherein the parity check code includes a cyclic redundancy check (CRC).
23. The method of claim 19 , wherein the error correction scheme includes forward error correction (FEC).
24. The method of claim 17 , further comprising:
maintaining a signal lock on the message data stream through the fill data.
25. A method, comprising:
receiving a user data packet from a high speed network at a transmission station;
calculating a message transmission time for the user data packet across a primary communication channel;
wherein the primary communication channel has lower bandwidth than the high speed network;
wherein the transmission time across the primary communication channel is longer than across the high speed data network;
calculating an inter-message transmission time between user data packets from the high speed network;
determining whether to transmit the user data packet over the primary communication channel at least based on message transmission time and inter-message transmission time;
accepting the user data packet for transmission over a primary communication channel when the message transmission time across the primary communication channel is more than an inter-message transmission time between user data packets; and
transmitting a message including the user data across the primary communication channel.
26. The method of claim 25 , further comprising:
rejecting the user data packet for transmission over a primary communication channel when a message transmission time is more than an inter-message transmission time.
27. The method of claim 26 , further comprising:
transmitting a message including the user data across a backend communication channel.
28. The method of claim 25 , wherein the user data packet concerns a transaction for a financial instrument.
29. The method of claim 1 , wherein the message has an integer number of modulated symbols.