Method and system for transmitting a DTMF signal with compressed voice in a packet switching network

• US 6,650,662 B1
• Filed: 09/09/1998
• Issued: 11/18/2003
• Est. Priority Date: 12/12/1997
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Arnaud, Charles, Richter, Gerard, Cesaro, Claude
• Primary Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US09/149,913
• Time in Patent Office: 1,896 Days
• Field of Search: 370/352, 370/353, 370/354, 370/355, 370/356, 370/252, 370/526, 379/283, 379/286, 379/351, 379/90.01, 379/93.01, 379/93.08, 379/93.09, 379/93.15, 379/93.26, 375/240
• US Class Current: 370/526
• CPC Class Codes: H04M 7/1295 Details of dual tone multiple frequency signalling
• CPC Class Codes: H04Q 1/4575 which are transmitted in digital form

Abstract

The present invention discloses a system and a method for transmitting DTMF signals over high speed digital networks using voice compression algorithms, and particularly to a system for ensuring the integrity of DTMF signals at the destination node of a network after compression and decompression of data on a voice connection. A DTMF Detector is placed in parallel with a voice compression unit performing the compression algorithm. When a candidate DTMF signal is detected, the signal component at the higher frequency in the candidate is filtered out to eliminate the possibility of double DTMF detection at end user equipment. When the candidate DTMF signal is finally validated by the source node as representing a true DTMF signal, only the data essential for reconstituting the DTMF signal are transferred to the destination node.

Claims

1. For use in a source node in a packet switching communication network having a plurality of nodes interconnected with transmission links, a method of transmitting data comprising the steps of:

receiving an input signal comprising voice signals and Dual Tone MultiFrequency (DTMF) signals having two signal components, each at a respective frequency;

detecting candidate DTMF signals in the input signal;

modifying each candidate DTMF signal by filtering the signal component occurring at one of the two frequencies in said candidate DTMF signal;

packetizing the voice signals and modified candidate DTMF signals;

transmitting the resulting packets into the network;

compressing voice signals and modified candidate DTMF signals prior to the step of packetizing such signals;

performing signal verification operations on a candidate DTMF signal to determine whether the signal is a valid DTMF signal;

generating a packet representing a valid DTMF signal; and

transmitting said packet into the network;

 

wherein the packet representing a valid DTMF signal comprises a packet identifier field for identifying the packet as representing a DTMF signal, a key field for identifying the pair of DTMF signals comprising the DTMF signal, a type field for identifying the tone-on and tone-off periods of the DTMF signal, and two energy fields representing, respectively, the energy level of the signal components at one of the two frequencies.

2. A source node for use in a packet switching communication network having a plurality of nodes interconnected with transmission links, said source node comprising:

a Dual Tone MultiFrequency (DTMF) detector for detecting candidate DTMF signals in a received signal comprising voice or DTMF signals wherein each DTMF signal has two signal components, each at a respective frequency;

a filter for modifying each detected candidate DTMF signal by removing the signal component at one of the two frequencies defining said detected candidate DTMF signal;

a packet generator for generating packets representing either voice signals or modified candidate DTMF signals;

a transmit interface for transmitting generated packets into the network;

compression logic for compressing the voice signals and the modified candidate DTMF signals prior to the generation of packets including such signals;

a DTMF verification logic component for determining whether a candidate DTMF signal is a true DTMF signal; and

packet generating logic for generating a packet representing the true DTMF signal;

 

wherein said packet representing a valid DTMF signal comprises a packet identifier field for identifying the packet as representing a DTMF signal, a key field for identifying the pair of DTMF signals comprising the DTMF signal, a type field for identifying the tone-on and tone-off periods of the DTMF signal, and two energy fields representing, respectively, the energy level of the signal components at one of the two frequencies.

3. A method of receiving data for use in a receiving node in a packet switching communication network having a plurality of nodes interconnected with transmission links, comprising the steps of:

receiving an input signal comprising compressed voice signals and packets representing DTMF signals having two signal components, each at a respective frequency;

detecting a packet representing DTMF signals in the received input signal;

reconstituting a DTMF signal represented by said packet; and

,

transmitting a reconstituted DTMF signal;

 

wherein the step of reconstituting includes decompressing voice packets and packets representing DTMF signals, and wherein said packets representing DTMF signals comprise

a packet identifier field for identifying the packet as representing a DTMF signal;

a key field for identifying the pair of DTMF signal components comprising the DTMF signal;

a type field for identifying the tone-on and tone-off periods of the DTMF signal;

and two energy fields, wherein each energy field represents a level of energy for a signal components at a respective frequency.

4. A destination node for use in a packet switching communication network having a plurality of nodes interconnected with transmission links, said destination node comprising:

an interface unit for detecting compressed DTMF packets in a received signal;

a DTMF generator for creating reconstituted DTMF signals from said DTMF packets, the reconstituted DTMF signals representing modified DTMF signals;

an interface for transmitting the reconstituted DTMF signals, wherein said compressed DTMF packets in a received signal comprise compressed voice signals, compressed DTMF packets, or both; and

decompression logic means for decompressing the voice signals and DMTF signal generation logic for reconstituting the DTMF signals prior to transmitting the voice signals and DTMF signals;

 

wherein the packet representing a valid DTMF signal comprises a packet identifier field for identifying the packet as representing a DTMF signal, a key field for identifying the pair of DTMF signals comprising the DTMF signal, a type field for identifying the tone-on and tone-off periods of the DTMF signal, and two energy fields representing, respectively, the energy level of the signal components at one of the two frequencies.