Method and apparatus for detecting bad data packets received by a mobile telephone using decoded speech parameters

• US 6,205,130 B1
• Filed: 09/25/1996
• Issued: 03/20/2001
• Est. Priority Date: 09/25/1996
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: DeJaco, Andrew P.
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US08/719,358
• Time in Patent Office: 1,637 Days
• Field of Search: 370/335, 370/342, 370/252, 445/63, 445/221, 445/222, 445/212, 445/225, 445/226.1, 445/296, 445/303, 445/312, 371/5.5, 371/51, 375/200, 375/224, 375/240, 375/350, 375/241, 704/264, 704/220, 704/221, 704/222, 704/223, 704/224, 704/228, 704/219
• US Class Current: 370/335
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: H03M 13/00 Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes error detection or error correction for analogue/digital, digital/analogue or code conversion H03M1/00 – H03M11/00; specially adapted for digital computers G06F11/08; for information storage based on relative movement between record carrier and transducer G11B, e.g. G11B20/18; for static stores G11C

Abstract

The mobile telephone detects bad data packets by decoding speech parameters represented by the packets and comparing those speech parameters against acceptable ranges of speech parameters. If the speech parameters do not lie within the acceptable ranges, the packets are discarded. This speech parameter-based detection of bad data packets is particularly useful in mobile telephones receiving variable rate data packets wherein an error in determining the rate of a packet results in the entire packet being decoded at an incorrect rate, thereby likely causing an annoying audible artifact in the decode speech signal. Such rate detection errors can occur even though a CRC or other conventional error detection check fails to detect the bad packet. In an exemplary implementation, the mobile telephone receives signals encoded with TIA/EIA/IS-95-A standards. Linear speech parameter frequencies and codebook gain parameters determined using linear predictive coding techniques are tested against acceptable ranges to detect bad data packets.

Claims

1. A signal reception system for use in a mobile telephone system, said reception system comprising:

a receiver that outputs a digitized signal containing received speech parameters representative of speech;

a decoder, responsive to a bit rate detection unit, that generates processed speech parameters from the received speech parameters, the processed speech parameters being based at least in part on a detected bit rate of the received speech parameters;

a comparator that compares the processed speech parameters with at least one predetermined range of acceptable speech parameters to identify and discard atypical processed speech parameters outside of said predetermined ranges, the comparing being based at least in part on a rate of change of the processed speech parameters; and

a speaker that outputs an audio signal associated with processed speech parameters lying within said predetermined ranges.

2. The system of claim 1, wherein said ranges of acceptable speech parameters are predetermined based on probabilities of encountering ranges of speech parameters in transmitted speech.

3. The system of claim 1, wherein said portions of said digitized signal are variable rate data packets.

4. The system of claim 3, further including means for determining the rate of each packet.

5. The system of claim 3, wherein said packets include cyclic redundancy check (CRC) bits and wherein the system further includes:

means for performing a CRC on each packet using said CRC bits; and

means for eliminating packets failing said CRC.

6. The system of claim 1, wherein the receiver, decoder, and speaker are within a mobile telephone.

7. The system of claim 1, wherein said predetermined ranges of acceptable speech parameters are provided in a table.

8. The system of claim 5, wherein said comparator examines packets which were already checked by said means for performing a CRC.

9. A mobile telephone comprising:

means for receiving variable rate packets containing received digitized speech parameters;

means for determining the frame rate of each packet;

means for performing error detection on said packets to identify transmission errors therein or to determine whether the packet is subject to a frame rate detection error;

frame erasure means for eliminating packets found to contain transmission errors or found to be subject to a frame rate detection error;

a decoder, responsive to said means for determining the rate of each packet, tat generates processed speech parameters from the received speech parameters from packets not eliminated by the frame erasure means, the processed speech parameters being based at least in part on the frame rate of the packet;

a comparator that compares the processed speech parameters with at least one preselected range of acceptable speech parameters, the comparing being based at least in part on a rate of change of the processed speech parameters; and

means for applying packets having processed speech parameters found to deviate from said preselected ranges of acceptable speech parameters to said frame erasure means.

10. A mobile telephone comprising:

a receiver for outputting packets containing received digitized speech parameters;

a frame rate detection unit for determining the frame rate for each packet;

an error detection unit for performing error detection on said packets to identify transmission errors therein or to determine whether the packet is subject to a frame rate detection error;

a frame erasure unit for eliminating packets found to contain transmission errors or found to be subject to a frame rate detection error;

a decoder, responsive to said frame rate detection unit, that generates processed speech parameters from the received speech parameters from packets not eliminated by the frame erasure unit, the processed speech parameters being based at least in part on the detected frame rate of the packet;

a comparator that compares the processed speech parameters with at least one preselected range of acceptable speech parameters, the comparing being based at least in part on a rate of change of the processed speech parameters; and

means for applying packets having processed speech parameters found to deviate from said preselected ranges of acceptable speech parameters to the frame erasure unit.

11. A signal reception method for use in a mobile telephone system, said method comprising the steps of:

receiving a digitized signal containing received speech parameters representative of speech;

decoding, responsive to a detected bit rate, the received speech parameters to generate processed speech parameters, the processed speech parameters being based at least in part on the detected bit rate;

comparing the processed speech parameters with at least one predetermined range of acceptable speech parameters to identify and discard atypical speech parameters outside of said predetermined ranges, said comparing being based at least in part on a rate of change of the processed speech parameters; and

outputting, through a speaker, an audio signal associated with processed speech parameters lying within said predetermined ranges.

12. The method of claim 11, wherein said ranges of acceptable speech parameters are predetermined based on probabilities of encountering ranges of speech parameters in transmitted speech.

13. The method of claim 11, wherein said portions of said digitized signal are variable rate data packets.

14. The method of claim 13, further including the step of determining the rate of each packet.

15. The method of claims 13, wherein said packets include cyclic redundancy check (CRC) bits and wherein the method further includes the steps of:

performing a CRC on each packet using said CRC bits; and

eliminating packets failing said CRC.

16. The method of claim 11, wherein the steps of receiving, decoding, and outputting are performed by a mobile telephone.

17. The method of claim 11, wherein said predetermined ranges of acceptable speech parameters are provided in a table.

18. The method of claim 15, wherein said step of comparing is performed subsequent to said step of performing a CRC.

19. A method for use in a mobile telephone comprising the steps of:

receiving variable rate packets containing received digitized speech parameters;

determining the frame rate of each packet;

performing error detection on frames of said packets to identify transmission errors therein or to determine whether the packet is subject to a frame rate detection error;

eliminating frames found to contain transmission errors or found to be subject to a frame rate detection error;

decoding, responsive to said step of determining the frame rate of each packet, the received speech parameters from frames not eliminated by the step of eliminating frames to thereby generate processed speech parameters, the processed speech parameters being based at least in part on the frame rate of the packet;

comparing the processed speech parameters with at least one preselected range of acceptable speech parameters, said comparing being based at least in part on a rate of change of the processed speech parameters; and

eliminating frames having processed speech parameters found to deviate from said preselected ranges of acceptable speech parameters.