Voice activity detection (VAD) dependent retransmission scheme for wireless communication systems

• US 8,327,211 B2
• Filed: 01/26/2009
• Issued: 12/04/2012
• Est. Priority Date: 01/26/2009
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Zopf, Robert W.
• Primary Examiner(s): Baderman, Scott
• Assistant Examiner(s): MILES, NEIL D
• Application Number:
  US12/359,700
• Publication Number:
  US 20100192033A1
• Time in Patent Office: 1,408 Days
• Field of Search: 714/748
• US Class Current: 714/748
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal
• CPC Class Codes: H04L 1/1825 Adaptation of specific ARQ protocol parameters according to transmission conditions
• CPC Class Codes: H04L 1/1854 Scheduling and prioritising arrangements
• CPC Class Codes: H04L 1/1887 Scheduling and prioritising arrangements

Abstract

A voice activity detection (VAD) dependent retransmission scheme is described that mitigates the effect of packet loss on an audio signal transmitted between terminals in a wireless communication system in a manner that is generally more robust than conventional state-of-the art packet loss concealment algorithms but that consumes less terminal power as compared to conventional retransmission schemes. In one implementation, this is achieved by allowing retransmissions to be requested by a terminal only when a packet received by the terminal is deemed bad and when a portion of an audio signal currently being received by the terminal is deemed to comprise active speech. In other implementations, the processing of retransmission requests received by a terminal is inhibited or turned off entirely during periods when a portion of an audio signal currently being transmitted by the terminal is deemed not to comprise active speech.

Claims

1. A method for selectively issuing retransmission requests by a terminal in a wireless communication system, comprising:

determining whether a packet received over a wireless channel from a remote terminal and carrying encoded audio samples representative of a frame of an audio signal is deemed bad;

responsive to determining that the packet is deemed bad;

determining whether voice activity has been detected in the audio signal based on an analysis of at least one previously-received frame of the audio signal;

determining if an immediately preceding packet was lost;

generating a retransmission request for the packet for transmission to the remote terminal responsive to determining that voice activity has been detected; and

generating a retransmission request for the packet for transmission to the remote terminal responsive to determining that voice activity has not been detected and the immediately preceding packet was lost.

2. The method of claim 1, wherein determining whether a packet received over a wireless channel and carrying audio samples representative of a frame of an audio signal is deemed bad comprises:

performing error detection and/or error correction operations on the packet.

3. The method of claim 1, wherein the wireless channel comprises a Bluetooth®

Extended Synchronous Connection Oriented (eSCO) channel.

4. The method of claim 1, wherein determining whether voice activity has been detected in the audio signal comprises:

analyzing at least one frame of the audio signal output from an audio decoder.

5. The method of claim 1, wherein generating a retransmission request for the packet for transmission to the remote terminal responsive to determining that voice activity has been detected comprises:

generating a retransmission request for the packet responsive to determining that voice activity has been detected and that a maximum number of retransmission requests has not been reached for the packet.

6. The method of claim 1, further comprising:

sending a signal indicating that the packet is lost to packet loss concealment logic responsive to determining that voice activity has not been detected; and

synthesizing digital audio samples corresponding to the encoded audio samples in the packet loss concealment logic responsive to receiving the signal indicating that the packet is lost.

19. The method of claim 1, wherein generating a retransmission request for the packet for transmission to the remote terminal responsive to determining that voice activity has not been detected and that the previous packet was lost comprises:

generating a retransmission request for the packet responsive to determining that voice activity has not been detected, that the previous packet was lost and that a maximum number of retransmission requests has not been reached for the packet.

7. A terminal for use in a wireless communication system, comprising:

a demodulator/channel decoder configured to determine whether a packet received over a wireless channel from a remote terminal and carrying encoded audio samples representative of a frame of an audio signal is deemed bad;

a voice activity detector configured to determine whether voice activity has been detected in the audio signal based on an analysis of at least one previously-received frame of the audio signal; and

a retransmission request generator connected to the demodulator/channel decoder and the voice activity detector, the retransmission request generator configured to generate a retransmission request for the packet for transmission to the remote terminal responsive to a combination of a determination by the demodulator/channel decoder that the packet is deemed bad and a determination by the voice activity detector that voice activity has been detected in the audio signal, the retransmission request generator being further configured to generate a retransmission request for the packet for transmission to the remote terminal responsive to a combination of a determination by the demodulator/channel decoder that the packet is deemed bad, a determination by the voice activity detector that voice activity has not been detected in the audio signal, and a determination that an immediately preceding packet was lost.

8. The terminal of claim 7, wherein the terminal comprises a wireless headset.

9. The terminal of claim 7, wherein the terminal comprises a cellular telephone.

10. The terminal of claim 7, wherein the demodulator/channel decoder is configured to determine whether the packet is deemed bad by performing error detection and/or error correction operations on the packet.

11. The terminal of claim 7, wherein the wireless channel comprises a Bluetooth®

Extended Synchronous Connection Oriented (eSCO) channel.

12. The terminal of claim 7, further comprising:

an audio decoder connected to the demodulator/channel decoder and the voice activity detector;

wherein the voice activity detector is configured to determine whether voice activity has been detected in the audio signal by analyzing at least one frame of the audio signal output by the audio decoder.

13. The terminal of claim 7, wherein the retransmission request generator is configured to generate the retransmission request for the packet responsive to a determination by the demodulator/channel decoder that the packet is deemed bad, to a determination by the voice activity detector that voice activity has been detected in the audio signal, and to a determination that a maximum number of retransmission requests has not been reached for the packet.

14. The terminal of claim 7, further comprising:

packet loss concealment logic connected to the retransmission request generator;

wherein the retransmission request generator is further configured to send a signal indicating that the packet is lost to the packet loss concealment logic responsive to a determination by the demodulator/channel decoder that the packet is deemed bad and to a determination by the voice activity detector that voice activity has not been detected, and

wherein the packet loss concealment logic is configured to synthesize digital audio samples corresponding to the encoded audio samples responsive to receiving the signal indicating that the packet is lost.

20. The terminal of claim 7, wherein the retransmission request generator further configured to generate a retransmission request for the packet for transmission to the remote terminal responsive to a determination by the demodulator/channel decoder that the packet is deemed bad, to a determination by the voice activity detector that voice activity has not been detected in the audio signal, to a determination that a previous packet was lost and to a determination that a maximum number of retransmission requests has not been reached for the packet.

15. A method for managing the processing of retransmission requests by a terminal in a wireless communication system, comprising:

monitoring an audio signal to be transmitted to a remote terminal over a wireless channel to determine whether voice activity has been detected in the audio signal; and

turning off logic that demodulates/decodes such retransmission requests responsive to determining that no voice activity has been detected in the audio signal.

16. The method of claim 15, further comprising:

turning off an antenna that monitors the wireless channel for retransmission requests from the remote terminal responsive to determining that no voice activity has been detected in the audio signal.

17. The method of claim 15, wherein the wireless channel comprises a Bluetooth®

Extended Synchronous Connection Oriented (eSCO) channel.

18. The method of claim 15, wherein monitoring an audio signal to be transmitted to a remote terminal over a wireless channel to determine whether voice activity has been detected in the audio signal comprises:

analyzing at least one frame of the audio signal output from an analog-to-digital converter.

21. A terminal for use in a wireless communication system, comprising:

a voice activity detector configured to determine whether voice activity has been detected in an audio signal to be transmitted to a remote terminal over a wireless channel;

an antenna configured to monitor the wireless channel for retransmission requests from the remote terminal; and

logic configured to demodulate/decode such retransmission requests;

wherein the terminal is operable to turn off the logic configured to demodulate/decode such retransmission requests responsive to a determination by the voice activity detector that voice activity has not been detected in the audio signal.

22. The terminal of claim 21, wherein the terminal is further operable to turn off the antenna responsive to the determination by the voice activity detector that voice activity has not been detected in the audio signal.