Discontinuous transmission (DTX) controller system and method

• US 20020172364A1
• Filed: 12/19/2000
• Published: 11/21/2002
• Est. Priority Date: 12/19/2000
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Mauro, Anthony
• Granted Patent: US 7,505,594 B2
• Time in Patent Office: Days
• US Class Current: 380/270
• CPC Class Codes: H04K 1/00 Secret communication

Abstract

A method and apparatus for controlling a discontinuous transmission process. Audio information is digitized and provided to a vocoder. A voice activity level is determined from the digitized audio signal, and if voice activity is present, active vocoder frames are generated at a predetermined output rate. If voice activity is not detected, inactive vocoder frames are generated. During transitions between periods of speech activity and speech inactivity, transition frames are generated, the transition frames comprising background noise information.

Claims

1. A method for controlling discontinuous transmissions, comprising the steps of:

determining a voice activity level in a digitized audio signal;

generating a control signal based on the level of voice activity detected;

generating active vocoder frames at a predetermined rate in a transmitter if said control signal indicates a first level of speech activity;

generating inactive vocoder frames if said control signal indicates a second level of speech activity; and

generating transition frames if said control signal indicates a transition from said first level to said second level, said transition frames comprising background noise information.

2. A method for controlling discontinuous transmissions, comprising the steps of:

generating data frames at a receiver;

storing said data frames in a queue;

providing at least one of said data frames from said queue to a decryption module if available in said queue;

providing a state vector to said decryption module, said state vector incremented at a predetermined rate;

generating a codebook from said decryption module, using at least said state vector, said codebook for decrypting at least one of said data frames; and

disabling said state vector when said queue is in an underflow condition.

3. The method of claim 2, wherein the step of disabling said state vector comprises the steps of:

determining that none of said data frames are available for decryption in said queue;

disabling said state vector;

determining that at least one of said data frames is available for decryption in said queue;

enabling said state vector; and

incrementing said state vector by a value of one.

4. A discontinuous transmission controller, comprising:

a vocoder for generating active vocoder frames from said digitized audio signal at a predetermined output rate if speech is present, for generating inactive vocoder frames during periods of speech inactivity, and for generating transition frames during transitions from speech activity to speech inactivity, said transition frames comprising background noise information.

5. The receiver of claim 4 wherein said state vector is enabled when at least one data frame becomes available for encryption in said queue.