System and method of minimizing the number of voice transcodings during a conference call in a packet-switched network

• US 6,574,469 B1
• Filed: 05/09/2000
• Issued: 06/03/2003
• Est. Priority Date: 05/09/2000
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Turcotte, Eric, Xiang, Zeng-Jun
• Primary Examiner(s): Vo, Nguyen T.
• Assistant Examiner(s): NGUYEN, TU X
• Application Number:
  US09/568,455
• Time in Patent Office: 1,120 Days
• Field of Search: 455/416, 370/328, 370/329, 370/338, 370/352, 370/353, 370/354, 370/355, 370/356, 370/400, 370/401, 370/410, 370/465, 370/466, 370/260, 370/261, 370/262
• US Class Current: 455/416
• CPC Class Codes: G10L 19/173 Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding
• CPC Class Codes: H04L 65/1043 Gateway controllers, e.g. media gateway control protocol [MGCP] controllers
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/1106 Call signalling protocols; H.323 and related
• CPC Class Codes: H04L 65/403 Arrangements for multi-party communication, e.g. for conferences data switching systems for conference H04L12/18; arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities H04M3/56; television conferencing systems H04N7/15
• CPC Class Codes: H04L 69/08 Protocols for interworking; Protocol conversion
• CPC Class Codes: H04L 69/24 Negotiation of communication capabilities
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04M 2203/5018 Initiating a conference during a two-party conversation, i.e. three-party-service or three-way-call computer conference organisation arrangements H04L12/1818
• CPC Class Codes: H04M 3/56 Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities video conference systems H04N7/15
• CPC Class Codes: H04M 7/0072 Speech codec negotiation H04L65/1069 takes precedence
• CPC Class Codes: H04M 7/1205 where the types of switching equipement comprises PSTN/ISDN equipment and switching equipment of networks other than PSTN/ISDN, e.g. Internet Protocol networks
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 4/00 Services specially adapted for wireless communication networks; Facilities therefor
• CPC Class Codes: H04W 88/181 Transcoding devices; Rate adaptation devices

Abstract

A system, method and access gateway for minimizing the number of transcodings of a speech signal during a Voice-over-IP (VoIP) conference call in a packet-switched network in which Tandem Free Operation (TFO) is utilized. The system includes a first gateway connecting the first mobile subscriber to the network, a second gateway connecting the second subscriber, and a third gateway connecting the third subscriber. The second gateway sends a message to the first gateway indicating a speech coding mode being utilized between the second gateway and the second subscriber. The third gateway sends a message to the first gateway indicating a speech coding mode being utilized between the third gateway and the third subscriber. When a three-way conference call is initiated, the first gateway encodes the call path to the second subscriber with the speech coding mode being utilized between the second gateway and the second subscriber. The first gateway also encodes the speech signal for the call leg to the third subscriber with the speech coding mode being utilized between the third gateway and the third subscriber.

Claims

1. A method of minimizing the number of transcodings of a speech signal during a conference call between a first mobile subscriber, a second subscriber, and a third subscriber, said call being transported over a packet-switched network in which Tandem Free Operation (TFO) is utilized to control transcoding of the speech signal, said method comprising the steps of:

establishing a first call between the first mobile subscriber and the second subscriber using TFO;

sending a message from a gateway connecting the second subscriber to the network (second gateway) to a gateway connecting the first subscriber to the network (first gateway), said message indicating a speech coding mode being utilized between the second subscriber and the second gateway;

receiving an input in a Mobile Switching Center (MSC) serving the first subscriber indicating that the third subscriber should be joined in the call;

establishing communications between the first gateway and a third gateway connecting the third subscriber to the network;

sending a message from the third gateway to the first gateway indicating a speech coding mode being utilized between the third subscriber and the third gateway;

establishing a three-way call bridge by a Conference Call Device (CCD) in the MSC serving the first subscriber, said call bridge providing a first call path to the first subscriber, a second call path to the second subscriber, and a third call path to the third subscriber, the second and third call paths going to the first gateway and using a speech coding mode supported by the CCD;

encoding within the first gateway, the speech signal for the call leg to the second subscriber with the speech coding mode being utilized between the second subscriber and the second gateway; and

encoding within the first gateway, the speech signal for the call leg to the third subscriber with the speech coding mode being utilized between the third subscriber and the third gateway.

2. The method of claim 1 wherein the second subscriber is a subscriber in the Public Switched Telephone Network (PSTN), and the step of encoding the speech signal for the call leg to the second subscriber includes encoding the speech signal with a speech coding mode utilized by the PSTN.

3. The method of claim 2 wherein the step of encoding the speech signal with a speech coding mode utilized by the PSTN includes encoding the speech signal with G.711 coding.

4. The method of claim 3 wherein the CCD supports the G.711 coding mode, and the step of encoding the speech signal with G.711 coding includes the steps of:

receiving the speech signal in the first gateway encoded with G.711 coding; and

transmitting the speech signal to the second gateway encoded with G.711 coding.

5. The method of claim 2 wherein the third subscriber is a second mobile subscriber, and the step of encoding the speech signal for the call leg to the third subscriber includes encoding the speech signal with a speech coding mode utilized over an air interface radio link with mobile stations.

6. The method of claim 5 wherein the step of encoding the speech signal with a speech coding mode utilized over an air interface radio link with mobile stations includes encoding the speech signal with Algebraic Code Excited Linear Prediction (ACELP) coding.

7. The method of claim 6 wherein the CCD supports the G.711 coding mode, and the step of encoding the speech signal with ACELP coding includes the steps of:

receiving the speech signal in the first gateway encoded with G.711 coding;

transcoding the speech signal to ACELP coding; and

transmitting the speech signal to the second gateway encoded with ACELP coding.

8. The method of claim 1 wherein the second subscriber is a second mobile subscriber, and the step of encoding the speech signal for the call leg to the second subscriber includes encoding the speech signal with a speech coding mode utilized over an air interface radio link with mobile stations.

9. The method of claim 8 wherein the third subscriber is a subscriber in the Public Switched Telephone Network (PSTN), and the step of encoding the speech signal for the call leg to the third subscriber includes encoding the speech signal with a speech coding mode utilized by the PSTN.

10. A system for minimizing the number of transcodings of a speech signal during a conference call between a first mobile subscriber, a second subscriber, and a third subscriber, said call being transported over a packet-switched network in which Tandem Free Operation (TFO) is utilized to control transcoding of the speech signal, said system comprising:

means for establishing a first call between the first mobile subscriber and the second subscriber using TFO;

a first gateway connecting the first mobile subscriber to the network;

a second gateway connecting the second subscriber to the network, said second gateway including means for sending a message to the first gateway indicating a speech coding mode being utilized between the second gateway and the second subscriber;

a third gateway connecting the third subscriber to the network, said third gateway including means for sending a message to the first gateway indicating a speech coding mode being utilized between the third gateway and the third subscriber;

means for establishing communications between the first gateway and the third gateway upon initiation of a conference call joining the third subscriber;

a Mobile Switching Center (MSC) serving the first mobile subscriber, said MSC including a Conference Call Device (CCD) for establishing a three-way call bridge, said call bridge providing a first call path to the first subscriber, a second call path to the second subscriber, and a third call path to the third subscriber, the second and third call paths going to the first gateway and using a speech coding mode supported by the CCD;

a first speech signal encoder within the first gateway for encoding the speech signal for the call leg to the second subscriber with the speech coding mode being utilized between the second gateway and the second subscriber; and

a second speech signal encoder within the first gateway for encoding the speech signal for the call leg to the third subscriber with the speech coding mode being utilized between the third gateway and the third subscriber.

11. An access gateway for enabling a mobile subscriber to access a packet-switched network and to place a conference call between the first mobile subscriber, a second subscriber, and a third subscriber using Tandem Free Operation (TFO) to control transcoding of a speech signal during the call, said access gateway comprising:

a first connection to a Mobile Switching Center (MSC) serving the first mobile subscriber, said MSC including a Conference Call Device (CCD) for establishing over the first connection, a call leg to the second subscriber and a call leg to the third subscriber;

a second connection to a second gateway connecting the second subscriber to the network, said second connection for receiving a message from the second gateway indicating a speech coding mode being utilized between the second gateway and the second subscriber;

a third connection to a third gateway connecting the third subscriber to the network, said third connection for receiving a message from the third gateway indicating a speech coding mode being utilized between the third gateway and the third subscriber;

a first speech signal encoder for encoding the call leg to the second subscriber with the speech coding mode being utilized between the second gateway and the second subscriber; and

a second speech signal encoder for encoding the call leg to the third subscriber with the speech coding mode being utilized between the third gateway and the third subscriber.

12. The access gateway of claim 11 wherein the second subscriber is a subscriber in the Public Switched Telephone Network (PSTN), and the call leg to the second subscriber is encoded with a speech coding mode utilized by the PSTN.

13. The access gateway of claim 12 wherein the speech coding mode utilized by the PSTN is G.711 coding.

14. The access gateway of claim 13 wherein the CCD supports the G.711 coding mode, and the first speech signal encoder includes:

means for receiving the call leg to the second subscriber encoded with G.711 coding; and

means for transmitting the call leg to the second subscriber to the second gateway encoded with G.711 coding.

15. The access gateway of claim 12 wherein the third subscriber is a second mobile subscriber, and the call leg to the third subscriber is encoded with a speech coding mode utilized over an air interface radio link with mobile stations.

16. The access gateway of claim 15 wherein the speech coding mode utilized over an air interface radio link with mobile stations is Algebraic Code Excited Linear Prediction (ACELP) coding.

17. The access gateway of claim 16 wherein the CCD supports the G.711 coding mode, and the second speech signal encoder includes:

means for receiving the call leg to the third subscriber encoded with G.711 coding;

means for transcoding the call leg to the third subscriber to ACELP coding; and

means for transmitting the call leg to the third subscriber to the gateway connecting the third subscriber encoded with ACELP coding.

18. The access gateway of claim 11 wherein the second subscriber is a second mobile subscriber, and the call leg to the second subscriber is encoded with a speech coding mode utilized over an air interface radio link with mobile stations.

19. The access gateway of claim 18 wherein the third subscriber is a subscriber in the Public Switched Telephone Network (PSTN), and the call leg to the third subscriber is encoded with a speech coding mode utilized by the PSTN.