Method of error control coding and decoding of messages in a packet-based data transmission system
View Patent ↗Initially the message frame comprising a header with length information, a data portion and a check sequence is expanded with gaps inserted to the data portion and the frame check sequence and the frame length information is updated, the frame is then scrambled and forward error correction data is generated and written into the gaps. An outer check sequence is generated and appended as part of the frame, after which the entire frame is transmitted. Error control decoding of the transmitted frame is achieved between reception and descrambling at a receiving device. The outer check sequence is optionally checked and removed, an error correction algorithm is applied to the frame in response to errors, after which the frame is descrambled, the forward error correction data and the inserted gaps are removed and the frame is restored to its original state and the length information is updated to its original value.
1. A method of error control coding and decoding of messages in a packet-based data transmission system, where each message comprises a header, which includes frame length information, a data portion and a frame check sequence, comprising the steps of:
at a transmitting device:
a) receiving said message including the header, the data portion and the frame check sequence and inserting gaps into the data portion and the frame check sequence of the frame,
b) updating the length information of the header to reflect the length of the frame including the gaps and a future outer frame check sequence,
c) applying a scrambling algorithm to at least part of the frame,
d) applying a forward error correction algorithm to at least part of the frame scrambled in step c) to generate forward error correction data,
e) inserting the generated forward error correction data into the gaps,
f) generating a scrambled outer frame check sequence and including the scrambled outer frame check sequence in the frame,
g) transmitting the scrambled frame with the forward error correction data and the outer frame check sequence,
at a receiving device:
h) receiving the scrambled frame with the forward error correction data and the scrambled outer frame check sequence,
i) checking whether or not the scrambled outer frame check sequence is correct,
j) if yes, removing the outer frame check sequence, removing the forward error correction data, descrambling the frame, removing the gaps, and updating the length information of the header to its original value,
k) if no, removing the outer frame check sequence, applying an error correction algorithm based on the inserted forward error correction data to at least part of the remainder of the frame, removing the inserted forward error correction data, descrambling the frame, removing the inserted gaps, and updating the length information of the header to its original value.
2. The method according to claim 1 , wherein the step of generating the scrambled outer frame check sequence comprises descrambling the scrambled frame including the forward error correction data, calculating an outer frame check sequence over at least part of the frame, including the calculated outer frame check sequence in the unscrambled frame and re-scrambling the frame with the outer frame check sequence.
3. A method of error control coding and decoding of messages in a packet-based data transmission system, where each message comprises a header, which includes frame length information, a data portion and a frame check sequence, comprising the steps of:
at a transmitting device:
a) receiving said message including the header, the data portion and the frame check sequence and inserting gaps into the data portion and the frame check sequence of the frame,
b) updating the length information of the header to reflect the length of the frame including the gaps and a future outer frame check sequence,
c) applying a scrambling algorithm to at least part of the frame
d) applying a forward error correction algorithm to at least part of the frame scrambled in step c) to generate forward error correction data,
e) inserting the generated forward error correction data into the gaps,
f) generating a scrambled outer frame check sequence and including the scrambled outer frame check sequence in the frame,
g) transmitting the scrambled frame with the forward error correction data and the scrambled outer frame check sequence, at a receiving device,
h) receiving the scrambled frame with the forward error correction data and the scrambled outer frame check sequence,
i) discarding the scrambled outer frame check sequence, applying an error correction algorithm based on the forward error correction data to at least part of the remainder of the frame, removing the forward error correction data, descrambling the frame, removing the gaps, and updating the length information of the header to its original value.
4. The method according to claim 3 , wherein the step of generating the scrambled outer frame check sequence comprises descrambling the scrambled frame including the forward error correction data, calculating an outer frame check sequence over at least part of the frame, including the calculated outer frame check sequence in the unscrambled frame and re-scrambling the frame with the outer frame check sequence.
5. A method of error control coding and decoding of messages in a packet-based data transmission system, where each message comprises a header, which includes frame length information, and a data portion, and a frame check sequence, comprising the steps of:
at a transmitting device:
a) receiving said message including the header, the data portion and the frame check sequence and updating the length information of the header in order to allow for a future expansion of the length of the frame,
b) applying a scrambling algorithm to at least part of the frame,
c) applying a forward error correction algorithm to at least part of the frame scrambled in step b) to generate forward error correction data,
d) inserting the generated forward error correction data into the data portion and the frame check sequence of the scrambled frame,
e) generating a scrambled outer frame check sequence and including the scrambled outer frame check sequence in the frame,
f) transmitting the scrambled frame with the forward error correction data and the scrambled outer frame check sequence,
at a receiving device:
g) receiving the transmitted scrambled frame with the forward error correction data and the scrambled outer frame check sequence,
h) checking whether or not the scrambled outer frame check sequence is correct,
i) if yes, removing the scrambled outer frame check sequence, removing the forward error correction data from the frame, descrambling the frame and restoring the length information of the header to its original value,
j) if no, removing the scrambled outer frame check sequence, applying an error correction algorithm to at least part of the frame based on the forward error correction data, removing the inserted forward error correction data from the frame, descrambling the frame and restoring the length information of the header to its original value.
6. The method according to claim 5 , wherein the step of generating the scrambled outer frame check sequence comprises de scrambling the scrambled frame with the forward error correction, calculating an outer frame check sequence over at least part of the frame, including the calculated outer frame check sequence in the unscrambled frame and re-scrambling the frame with the outer frame check sequence.
7. A method of error control coding and decoding of messages in a packet-based data transmission system, where each message comprises a header, which includes frame length information, and a data portion, and a frame check sequence, comprising the steps of:
at a transmitting device:
a) receiving said message including the header, the data portion and the frame check sequence and updating the length field of the header in order to allow for a future expansion of the length of the frame,
b) applying a scrambling algorithm to at least part of the frame,
c) applying a forward error correction algorithm to at least part of the frame scrambled in step b) to generate forward error correction data,
d) inserting the generated forward error correction data into the data portion and the frame check sequence of the scrambled frame,
e) generating a scrambled outer frame check sequence and including the scrambled outer frame check sequence in the frame,
f) transmitting the scrambled frame with the forward error correction data and the scrambled outer frame check sequence, at a receiving device,
g) receiving the transmitted scrambled frame with the forward error correction data and the scrambled outer frame check sequence,
h) discarding the scrambled outer frame check sequence, applying an error correction algorithm to the frame based on the forward error correction data, removing the inserted forward error correction data from the frame, descrambling the frame and restoring the length information of the header to its original value.
8. The method according to claim 7 , wherein the step of generating the scrambled outer frame check sequence comprises descrambling the scrambled frame including the forward error correction data, calculating an outer frame check sequence over at least part of the frame, including the calculated outer frame check sequence in the unscrambled frame and re-scrambling the frame with the outer frame check sequence.
9. The method according to any of the above claims, wherein all steps are performed at a physical protocol layer of the transmitting device and the receiving device, respectively.