Method and apparatus for acoustic echo cancellation in a communication system providing TTY/TDD service

Abstract

A method and apparatus are disclosed for canceling acoustic echo generated during transmission of text information in a communication system supporting a TTY/TDD service. When a mobile-to-land call is established between a mobile subscriber and a PSTN subscriber, a decoder notifies an encoder of detection of TTY/TDD text in a BS vocoder. The encoder then transmits a packet having silence information, which prevents acoustic echo reproduction of the text in the TTY/TDD device.

1 . A method for canceling acoustic echo generated from a second mobile station (MS) during transmission of text information from a first teletype/ telecommunications device for the deaf (TTY/TDD) device to a second TTY/TDD device in a communication system having a first base station (BS), a second BS, a mobile switching center (MSC) for connecting the first and second BSs, a first MS connected wirelessly to the first BS, the first MS having the first TTY/TDD device for transmitting and receiving text information, and the second MS connected wirelessly to the second BS, and the second MS having the second TTY/TDD device for transmitting and receiving text information, the method comprising: 
 determining whether text information has been received in the second BS from the first TTY/TDD device of the first BS; and    discontinuing reception of text information from the second MS for a predetermined time in the second BS, if the text information has been received.    
   
   
       2 . The method of  claim 1 , wherein a vocoder of the second BS detects the text information.  
   
   
       3 . The method of  claim 1 , wherein the vocoder of the second BS discontinues the text information reception from the second MS for the predetermined time.  
   
   
       4 . The method of  claim 1 , wherein the predetermined time is at least the time required for decoding in a decoder and encoding in an encoder of the second MS.  
   
   
       5 . A method for canceling acoustic echo generated from a second mobile station (MS) during transmission of text information from a first teletype/ telecommunications device for the deaf (TTY/TDD) device to a second TTY/TDD device in a communication system having a first base station (BS), a second BS, a mobile switching center (MSC) for connecting the first and second BSs, a first MS connected wirelessly to the first BS, the second MS connected wirelessly to the second BS, the first TTY/TDD device connected to the first MS, for transmitting and receiving text information to and from the first MS, and the second TTY/TDD device connected to the second MS, for transmitting and receiving text information to and from the second MS, the method comprising: 
 determining whether text information has been received in the second BS from the first TTY/TDD device through the first BS and the MSC; and    discontinuing reception of text information from the second MS for a predetermined time in the second BS, if the text information has been received.    
   
   
       6 . The method of  claim 5 , wherein a vocoder of the second BS detects the text information.  
   
   
       7 . The method of  claim 5 , wherein the vocoder of the second BS discontinues the text information reception from the second MS for the predetermined time.  
   
   
       8 . The method of  claim 5 , wherein the predetermined time is at least the time required for decoding in a decoder and encoding in an encoder of the second MS.