Method and apparatus supporting TDD/TTY modulation over vocoded channels

Abstract

A method, apparatus, and article of manufacture used to encode/decode a low activity communication signal—such as a Baudot tone—for transmission over a telecommunications system. The telecommunications system may include any number of wireless links. Once the system is noticed that a low activity signal needs to be transmitted, each vocoder used in the system to encode/decode the signal performs a unique encoding/decoding process. In one embodiment, frames containing errors adversely affecting a signal are delivered to the vocoder and the “soft bits” contained therein are used to determine the original signal transmitted. In another embodiment, encoding of the signal may include encoding the signal using redundancy with the encoded signal being spread across multiple vocoder frames.

What is claimed is:  
     
         1 . A method comprising: 
 receiving a low activity communication signal;    encoding the low activity communication signal in a first frame using channel-coding redundancy, the encoding comprising interleaving a sequence of bits representing the low activity signal across multiple frames; and    transmitting the multiple frames to a destination.    
     
     
         2 . The method of  claim 1  wherein encoding the low activity communication signal includes using vocoder signatures containing sequenced bits that are spaced further apart than sequenced bits contained within standard vocoder parameters.  
     
     
         3 . The method of  claim 1  further comprising: 
 receiving the multiple frames at the destination;  
 decoding the received frames to retrieve the sequence of bits representing the low activity communication signal, wherein the decoding comprising retrieving the sequence of bits representing the low activity communication signal based on information contained in frames adjacent to the first frame if the first frame is not received at said destination.  
 
     
     
         4 . The method of  claim 1  wherein the low activity communication signal comprises a Baudot signal.  
     
     
         5 . An apparatus comprising: 
 an encoder to receive and encode a low activity communication signal in a first frame, the first encoder to interleave a sequence of bits representing the low activity communication signal across multiple frames and to transmit the multiple frames to a destination; and    a decoder to receive the multiple frames at the destination, the decoder to retrieve the sequence of bits representing the low activity communication signal based on information contained in frames adjacent to the first frame if the first frame is not received at the destination.    
     
     
         6 . The apparatus of  claim 5  wherein encoding the low activity communication signal includes using vocoder signatures containing sequenced bits that are spaced further apart than sequenced bits contained within standard vocoder parameters.  
     
     
         7 . The apparatus of  claim 5  wherein the low activity communication signal comprises a Baudot signal.  
     
     
         8 . A machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations including: 
 receiving a low activity communication signal;    encoding the low activity communication signal in a first frame using channel-coding redundancy, the encoding comprising interleaving a sequence of bits representing the low activity signal across multiple frames; and    transmitting the multiple frames to a destination.    
     
     
         9 . The machine-readable medium of  claim 8  wherein encoding the low activity communication signal includes using vocoder signatures containing sequenced bits that are spaced further apart than sequenced bits contained within standard vocoder parameters.  
     
     
         10 . The machine-readable medium of  claim 9  further comprising: 
 receiving the multiple frames at the destination;  
 decoding the received frames to retrieve the sequence of bits representing the low activity communication signal, wherein the decoding comprising retrieving the sequence of bits representing the low activity communication signal based on information contained in frames adjacent to the first frame if the first frame is not received at said destination.  
 
     
     
         11 . The machine-readable medium of  claim 8  wherein the low activity communication signal comprises a Baudot signal.