Encoding/decoding scheme for communication of low latency data for the subcarrier traffic information channel

• US 5,949,822 A
• Filed: 05/30/1997
• Issued: 09/07/1999
• Est. Priority Date: 05/30/1997
• Status: Expired due to Term

• Current Assignee: ViaSat Incorporated
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Hancharik, David J.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Ghayour, Mohammad
• Application Number:
  US08/866,075
• Time in Patent Office: 830 Days
• Field of Search: 375/242, 370/427, 370/429, 370/441, 370/449, 370/458
• US Class Current: 375/242
• CPC Class Codes: H04H 20/55 for traffic information
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence

Abstract

A communication system for communicating low latency data in a fading channel environment using a data structure having data frames modulated on a subcarrier signal and on a commercial radio channel bandwidth. Low latency data is updated relatively rapidly at the low latency data generator. Because of this constant changing of low latency data at the point of generation in the transmitter end, the present invention communicates low latency data from the transmitter end to the receiver end of the communication system with relatively low delay. This communication system encodes and decodes low latency data using a single block encoding/decoding scheme. Such an encoding/decoding scheme introduces relatively less delay during the encoding/decoding processes while ensuring satisfactory data integrity for data communication in a fading channel environment. Using such an encoding/decoding scheme leads to more currently generated low latency data transmission at the transmitter end and in relatively less time for the decoding process with the decoder structure being more simple at the receiver end.

Claims

1. A method for communicating low latency data to a mobile vehicle within a communication system that uses a data structure having data frames modulated on a subcarrier signal and on a commercial radio channel bandwidth, said method including the steps of:

A. receiving a data word from a data word generator, said data word comprising a first predetermined number of bits, said data word being updated every predetermined time period by said data word generator;

B. generating an encoded word from said data word, said encoded word comprising a second predetermined number of bits that are consecutively within a block of data bits, said block of data bits fitting within a low latency time slot within each data frame of said data structure in said communication system, said step B further comprising the steps of

appending a predetermined number of high bits to said first predetermined number of bits of said data word to generate a first extended data word;

generating a bit parity word by taking a remainder of a binary polynomial division of said first extended data word by a generator polynomial to generate a second extended data word by appending said bit parity word to said first extended data word;

appending a predetermined number of low bits to said second extended data word to generate said encoded word; and

C. repeating steps A and B for each update of said data word to generate a respective updated encoded word for each update of said data word until a current low latency time slot within a current data frame is reached, said current low latency time slot being used to carry a last updated encoded word which is said encoded word generated last in step B when said current low latency time slot is reached.

2. The method for communicating low latency data as recited in claim 1, further including the steps of:

D. incorporating said last updated encoded word into said current low latency time slot within said current data frame;

E. modulating said current data frame onto said subcarrier signal; and

F. transmitting the modulated subcarrier signal via said commercial radio channel bandwidth.

3. The method for communicating low latency data as recited in claim 2, further including the steps of:

G. receiving said transmitted modulated subcarrier signal at said mobile vehicle;

H. demodulating said modulated subcarrier signal to recover said last updated encoded word; and

I. decoding said last updated encoded word, upon recovery of said block of second predetermined number of bits of said last updated encoded word in step H, to generate a decoded word which is substantially similar to said data word that was generated by said data word generator and that was encoded into said last updated encoded word in one of steps B and C.

4. The method for communicating low latency data as recited in claim 3, further including the step of:

J. sending said decoded word to a data processor for processing said decoded word.

5. The method for communicating low latency data as recited in claim 4, wherein said data word comprises Differential Global Positioning System (GPS) data.

6. The method for communicating low latency data as recited in claim 3, wherein step I includes the step of:

detecting incorrect bits within said decoded data word that are in error using majority logic decoding; and

correcting at least a predetermined number of said incorrect bits by changing the state of said predetermined number of said incorrect bits using majority logic decoding.

7. A method for communicating low latency data to a mobile vehicle within a communication system that uses a data structure having data frames modulated on a subcarrier signal within a radio channel bandwidth, said method including the steps of:

A. receiving a data word from a data word generator, said data word comprising a first predetermined number of bits, said data word being updated every predetermined time period by said data word generator;

B. generating an encoded word from said data word, said encoded word comprising a second predetermined number of bits that are consecutively within a block of data bits, said block of data bits fitting within a low latency time slot within each data frame of said data structure in said communication system, said step B including the steps of

appending a predetermined number of high bits to said first predetermined number of bits of said data word to generate a first extended data word;

generating a bit parity word by taking a remainder of a binary polynomial division of said first extended data word by a generator polynomial to generate a second extended data word by appending said bit parity word to said first extended data word; and

appending a predetermined number of low bits to said second extended data word to generate said encoded word;

C. repeating steps A and B for each update of said data word to generate a respective updated encoded word for each update of said data word until a current low latency time slot within a current data frame is reached, said current low latency time slot being used to carry a last updated encoded word which is said encoded word generated last in step B when said current low latency time slot is reached;

D. incorporating said last updated encoded word into said current low latency time slot within said current data frame;

E. modulating said current data frame onto said subcarrier signal;

F. transmitting said modulated subcarrier signal via a commercial radio channel bandwidth;

G. receiving said transmitted modulated subcarrier signal at said mobile vehicle;

H. demodulating said modulated subcarrier signal to recover said last updated encoded word;

I. decoding said last updated encoded word, upon recovery of said block of second predetermined number of bits of said last updated encoded word from said current data frame in step H, to generate a decoded data word which is substantially similar to said data word that was generated by said data word generator and that was encoded into said last updated encoded word in one of steps B and C, said step I including the steps of

detecting incorrect bits within said decoded data word that are in error using majority logic decoding; and

correcting at least a predetermined number of said incorrect bits by changing the state of said predetermined number of said incorrect bits using majority logic decoding; and

J. sending said decoded data word to a data processor for processing said decoded data word.

8. The method for communicating low latency data as recited in claim 7, wherein said data word comprises Differential Global Positioning System (GPS) data.

9. A transmitter of a communication system for communicating low latency data to a mobile vehicle within a data structure having data frames modulated on a subcarrier signal and on a commercial radio channel bandwidth, said transmitter comprising:

a data word receiver for receiving a data word having a first predetermined number of bits from a data word generator, said data word being updated every predetermined time period by said data word generator;

an encoder, operatively coupled to said data word receiver, for encoding said data word and each update of said data word from said data word receiver into an encoded word, said encoded word comprising a second predetermined number of bits that are consecutively within a block of data bits, said block of data bits fitting within a low latency time slot within each data frame of said data structure in said communication system, wherein said encoder further includes

a high bit extension generator for generating a predetermined number of high bits to be appended to said first predetermined number of bits of said data word to generate a first extended data word;

a bit parity word generator for generating a bit parity word by taking a remainder of a binary polynomial division of said first extended data word by a generator polynomial to generate a second extended data word by appending said bit parity word to said extended data word,

a low bit extension generator for generating a predetermined number of low bits to be appended to said second extended data word to generate said encoded word; and

a data frame synchronization circuit, operatively coupled to said encoder, for inserting a last updated encoded word generated last in said encoder into a current low latency time slot within a current data frame when said current low latency time slot is reached within said current data frame.

10. The transmitter as recited in claim 9, further comprising:

a subcarrier signal generator for generating said subcarrier signal;

a modulator, operatively coupled to said subcarrier signal generator and said data frame synchronization circuit, for modulating said data frames onto said subcarrier signal to generate a modulated subcarrier signal; and

a transmitter for transmitting said modulated subcarrier signal via a commercial radio channel bandwidth.

11. A communication system for communicating low latency data to a mobile vehicle within a data structure having data frames modulated on a subcarrier signal within a radio channel bandwidth, said apparatus comprising:

a data word receiver for receiving a data word having a first predetermined number of bits from a data word generator, said data word being updated every predetermined time period by said data word generator;

an encoder, operatively coupled to said data word receiver, for encoding said data word and each update of said data word from said data word receiver into an encoded word, said encoded word comprising a second predetermined number of bits that are consecutively within a block of data bits, said block of data bits fitting within a low latency time slot within each data frame of said data structure in said communication system, said encoder further comprising;

a high bit extension generator for generating a predetermined number of high bits to be appended to said first predetermined number of bits of said data word to generate a first extended data word;

a bit parity word generator for generating a bit parity word by taking a remainder of a binary polynomial division of said first extended data word by a generator polynomial to generate a second extended data word by appending said bit parity word to said first extended data word; and

a low bit extension generator for generating a predetermined number of low bits to be appended to said second extended data word to generate said encoded word;

a data frame synchronization circuit, operatively coupled to said encoder, for inserting a last updated encoded word generated last in said encoder into a current low latency time slot within a current data frame when said current low latency time slot is reached within said current data frame;

a subcarrier signal generator for generating said subcarrier signal;

a modulator, operatively coupled to said subcarrier signal generator and said data frame synchronization circuit, for modulating said data frames onto said subcarrier signal to generate a modulated subcarrier signal;

a transmitter for transmitting said modulated subcarrier signal via a commercial radio channel bandwidth;

a radio channel antenna, disposed on said mobile vehicle, for receiving said modulated subcarrier signal transmitted by said transmitter;

a demodulator, operatively coupled to said radio channel antenna, for demodulating said modulated subcarrier signal to recover said last updated encoded word;

a decoder, operatively coupled to said demodulator, for decoding said last updated encoded word to generate a decoded word which is substantially similar to said data word that was generated by said data word generator and that was encoded into said last updated encoded word by said encoder, said decoder further comprising;

a majority logic decoder for detecting incorrect bits within said decoded data word that are in error and for correcting at least a predetermined number of said incorrect bits by changing the state of said predetermined number of said incorrect bits; and

a data processor, operatively coupled to said decoder, for processing said decoded word.

12. The communication system as recited in claim 11, wherein said data word includes Differential GPS (Global Positioning System) data.