Method for detecting and correcting data errors in an RF data link

1. A method for correcting errors in a block of digital data transmitted over a wireless link that is a part of a Tire Pressure Monitoring System (TPMS), the data block comprising a plurality of transmitted data frames, and each data frame including at least one sequence of data bits, the method comprising:

a. identifying valid data frames and corrupted data frames by measuring a data corruption level for each transmitted data frame by detecting a number and position of invalid data bits in the transmitted data frame, the number of invalid data bits detected using edge detection windows, said edge detection windows determined by detecting an edge of a one bit and an edge of a subsequent bit of said data frame;

b. comparing the measured data corruption level for each corrupted data frame to a data corruption threshold;

c. reconstructing the corrupted data frames having a data corruption level below the data corruption threshold;

d. reconstructing the data block using data from valid and reconstructed data frames; and

e. verifying the data in the reconstructed data block,

wherein determination of said edge detection windows further comprises:

determining if a bit time between said one bit and said subsequent bit is within predetermined tolerances;

using said bit time between said one bit and said subsequent bit as an edge detection window if said bit time between said one bit and said subsequent bit is within said predetermined tolerances; and

using a predetermined nominal bit time as said edge detection window if said bit time between said one bit and said subsequent bit is not within said predetermined tolerances.

2. The method of claim 1 wherein measuring the data corruption level further comprises time synchronizing the edge detection windows after detection of each data bit.

3. The method of claim 1 wherein said one bit and said subsequent bit are a part of the preamble of said frame.

4. A method for detecting and correcting data errors in a wireless link that is part of a Tire Pressure Monitoring System (TPMS), the method comprising:

(a) detecting data errors in encoded data frames received over the wireless link, wherein the encoded data frames comprise symbols, by examining whether the symbols are received over finite time intervals, said finite time intervals determined by detecting an edge of a one bit and an edge of a subsequent bit in said data frame;

(b) designating symbols not received over the finite time intervals as data errors;

(c) correcting the detected data errors that fall within a detected error threshold; and

(d) validating data frames containing corrected data errors by checking the corrected data frames against programmable boundary parameters,

wherein determination of said finite time intervals further comprises:

determining if a bit time between said one bit and said subsequent bit is within predetermined tolerances;

using said bit time between said one bit and said subsequent bit as an finite time interval if said bit time between said one bit and said subsequent bit is within said predetermined tolerances; and

using a predetermined nominal bit time as said finite time interval if said bit time between said one bit and said subsequent bit is not within said predetermined tolerances.

5. The method of claim 4 , wherein the symbols have a period, and wherein the finite time intervals have a duration of one symbol period.

6. The method of claim 4 , wherein said detecting the bit edges is used to determine an edge detection window over the finite time interval.

7. The method of claim 6 , wherein the edge detection window is resynchronized with the detection of every received symbol.

8. The method of claim 4 , further comprising the symbols being Manchester encoded.

9. The method of claim 4 , wherein said designating further comprises correcting detected errors by using a cyclic redundancy check algorithm.

10. The method of claim 4 , wherein each detected data error has a location in the received data frame and the location of the data error is stored in a memory.

11. The method of claim 10 , wherein an error correction algorithm is used to correct the data errors, the number of iterations computed by the error correction algorithm is reduced by recalling the locations of the data errors and attempting to correct the data frame by changing only the known data errors so that iterations of the error correction algorithm involving changes to known correct data will not be attempted.

12. The method of claim 4 , further comprising implementing the error detection and correction methods in software.

13. The method of claim 4 wherein said one bit and said subsequent bit are a part of the preamble of said frame.

14. A method for detecting and correcting data errors in a wireless channel that is part of a Tire Pressure Monitoring System (TPMS), the method comprising:

(a) detecting data errors in data frames received over the wireless channel, wherein the data frames comprise symbols, and wherein the data errors are detected by examining the presence of received symbols utilizing edge detection windows over finite time intervals, said edge detection windows over finite time intervals determined by detecting an edge of a one bit and an edge of a subsequent bit in said data frame;

(b) determining if the detected data errors are correctable and discarding the data frames that contain uncorrectable data errors;

(c) correcting detected data errors in the data frames containing correctable errors; and

(d) validating corrected data frames by checking corrected data frames against boundary thresholds,

wherein determination of said edge detection windows over finite time intervals further comprises:

determining if a bit time between said one bit and said subsequent bit is within predetermined tolerances;

using said bit time between said one bit and said subsequent bit as an edge detection window over a finite time interval if said bit time between said one bit and said subsequent bit is within said predetermined tolerances; and

using a predetermined nominal bit time as said edge detection window over said finite time interval if said bit time between said one bit and said subsequent bit is not within said predetermined tolerances.

15. The method of claim 14 , wherein in said detecting, the data frames have checksums and said determining further comprises using a data determination algorithm to manipulate only the detected data errors in the data frame while attempting to satisfy the checksum and subsequently storing any manipulated data frames that satisfy the checksum, wherein the received data frame is correctable only if exactly one manipulated data frame from the data determination algorithm satisfies the checksum.

16. The method of claim 15 , wherein the data determination algorithm comprises a cyclic redundancy check algorithm.

17. The method of claim 14 wherein said one bit and said subsequent bit are a part of the preamble of said frame.

18. A method for detecting and correcting data errors in a wireless link that is part of a Tire Pressure Monitoring System (TPMS), the method comprising:

(a) receiving Manchester encoded data frames over the wireless link, wherein the data frames have checksums and are comprised of symbols, the symbols each having a symbol period;

(b) detecting errors in the received data frames by determining whether each symbol is present in the received data frame, wherein each data error has a location in the received data frame and the presence of each symbol is detected by utilizing edge detection windows having a duration of one symbol period, said one symbol period determined by detecting an edge of a one bit and an edge of a subsequent bit in a preamble of said data frame, the symbols in the received data frame marked as data errors if the edge detection window closes without a symbol being detected;

(c) storing the location of each data error in a memory;

(d) discarding data frames if the number of data errors exceeds a programmable threshold level;

(e) determining if the data frames are correctable by utilizing a data correction algorithm, wherein the data correction algorithm recalls and changes only the data errors in an attempt to satisfy the checksum so that the number of iterations used by the data correction algorithm in attempting to satisfy the checksum is reduced by not attempting iterations with changes to known good data, and wherein all modified data frames that satisfy the checksum are stored to the memory;

(f) correcting the received data frames if only exactly one modified data frame satisfies the checksum and discarding all other uncorrectable data frames; and

(g) validating the corrected data frames against programmable boundary thresholds

wherein determination of said one symbol period further comprises:

determining if a bit time between said one bit and said subsequent bit is within predetermined tolerances;

using said bit time between said one bit and said subsequent bit as said one symbol period if said bit time between said one bit and said subsequent bit is within said predetermined tolerances; and

using a predetermined nominal bit time as said one symbol period if said bit time between said one bit and said subsequent bit is not within said predetermined tolerances.

19. The method of claim 18 , wherein in said correcting discards the received data frames if the number of data errors exceeds four.

20. The method of claim 18 , wherein in said data correction algorithm is a cyclic redundancy check algorithm.

21. The method of claim 18 , wherein the method for detecting and correcting data errors is implemented in software.