Apparatus, and associated method, for decoding convolutionally encoded data

• US 8,381,084 B2
• Filed: 10/22/2008
• Issued: 02/19/2013
• Est. Priority Date: 10/23/2007
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Research In Motion Limited (Blackberry Limited)
• Inventors: Furbeck, David
• Primary Examiner(s): LOHN, JOSHUA A
• Application Number:
  US12/256,358
• Publication Number:
  US 20090193320A1
• Time in Patent Office: 1,581 Days
• Field of Search: 714/786, 714/794, 714/795, 340/425.5, 340/436
• US Class Current: 714/794
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 76/50 for emergency connections

Abstract

An apparatus, and an associated method, for correcting errors in decoded data, decoded by a convolutional decoder, such as an SOVA (Soft Output Viterbi Algorithm). A CRC check is performed upon the decoded data. If the CRC check fails, a conclusion is made that the decoded data contains errors. Portions of the decoded data indicated to exhibit low levels of reliability are toggled with values of most-likely error events. A corrected sequence of the decoded data is formed that corrects for the errors in the decoded data.

Claims

1. An apparatus for facilitating recovery of automatically transmitted data of an emergency message, said apparatus comprising:

a decoder configured to decode the transmitted data of the emergency message, the emergency message including information associated with a vehicular emergency;

a decoded data recovery checker configured to check whether the transmitted data, once decoded, is successfully decoded;

a storage element configured to store at least one value corresponding to a coded data part of the transmitted data of the emergency message whose decoding is associated with a likely error event; and

a bit changer configured to change part of the transmitted data of the emergency message once decoded associated with reliability levels less than a threshold, the change being in accordance with the at least one value stored in the storage element and that is retrieved by said bit changer, if said decoded data recovery checker determines the transmitted data to be unsuccessfully decoded and to return the transmitted data having the changed part to the decoded data recovery checker, the transmitted data of the emergency message with the changed part, once successfully decoded, permitting use of the information associated with the vehicular emergency while obviating necessity to request retransmission of the transmitted data of the emergency message.

2. The apparatus of claim 1 wherein said decoded data recovery checker is further configured to check whether the transmitted data, once decoded, and with the part changed by said bit changer is successfully decoded.

3. The apparatus of claim 2 wherein said decoded data recovery checker and said bit changer are configured to operate iteratively.

4. The apparatus of claim 1 wherein said bit changer is configured to toggle selected bits of the part of the transmitted data, once decoded, that is associated with the reliability levels less than the threshold.

5. The apparatus of claim 1 wherein said decoder comprises a convolutional decoder.

6. The apparatus of claim 1 wherein said decoded data recovery checker comprises a CRC, cyclic redundancy code, checker.

7. The apparatus of claim 1 wherein said storage element is further configured to store a plurality of values.

8. The apparatus of claim 1 wherein the value corresponds to a coded data part whose decoding is associated with a likely error event.

9. The apparatus of claim 1 wherein the transmitted data checked by said decoded data recovery checker comprises voice-band modem data.

10. The apparatus of claim 1 wherein said decoded data recovery checker is embodied at a PSAP, Public Safety Access Point.

11. A method for facilitating recovery of automatically transmitted data of an emergency message, said method comprising:

decoding the transmitted data of the emergency message, the emergency message including information associated with a vehicular emergency;

checking whether the transmitted data, once decoded, is successfully decoded;

storing at least one value corresponding to a coded data part of the transmitted data whose decoding is associated with a likely error event;

changing part of the transmitted data, once decoded, associated with reliability levels less than a threshold if the transmitted data is unsuccessfully decoded, the change being in accordance with the at least one value stored in, and retrieved from, the storage element, if the transmitted data is unsuccessfully decoded; and

checking whether transmitted data having the changed part is successfully decoded, the transmitted data of the emergency message with the changed part, once successfully decoded, permitting use of information associated with the vehicular emergency while obviating necessity to request retransmission of the transmitted data of the emergency message.

12. The method of claim 11 wherein said checking comprises performing a CRC, Cyclic Redundancy Code, check upon a CRC contained in the transmitted data.

13. The method of claim 11 wherein said checking and said changing are performed iteratively.

14. The method of claim 11 wherein said checking further comprises checking whether the transmitted data, once decoded, and with the part changed responsive to said changing the part of the transmitted data is successfully decoded.

15. The method of claim 11 wherein said changing comprises toggling selected bits of the part of the transmitted data, once decoded, that is associated with the reliability levels less than the threshold.

16. The method of claim 11 further comprising storing a value used when changing the part of the transmitted data, once decoded.

17. The method of claim 16 wherein said storing comprises storing a plurality of values.

18. The method of claim 16 wherein the value corresponds to a coded data part whose decoding is associated with a likely error event.