ADVANCED LMSD INTERSYSTEM HANDOFF

• US 20120294280A1
• Filed: 10/21/2011
• Published: 11/22/2012
• Est. Priority Date: 05/20/2011
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bienn, Marvin, Stephens, Gary
• Granted Patent: US 9,949,171 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/0022 for transferring data sessions between adjacent core network technologies
• CPC Class Codes: H04W 36/00226 wherein the core network technologies comprise IP multimedia system [IMS], e.g. single radio voice call continuity [SRVCC]
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 76/22 Manipulation of transport tunnels

Abstract

An Anchor Mobile Switching Center emulation (MSCe) and a Target MSCe are described herein that take part in an intersystem handoff of a Mobile Station (MS) which is in communication with a B-party. Upon the MS establishing a connection with the Target MSCe, the Anchor MSCe may perform SDP offer/answer exchange between the Target network and the B-Party for the purpose of codec renegotiation to correct a transcoding incompatibility or to enhance the voice bearer path characteristics or to minimize the number of transcodings in the bearer path, between the two parties. The Anchor MSCe and the Target MSCe both support Advanced Legacy Mobile Station Domain (ALMSD) implying that only the SIP transport is used for intersystem handoff communications.

Claims

1. An Anchor Mobile Switching Center emulation (MSCe) for supporting an intersystem handoff of a Mobile Station (MS) from an Anchor Network to a Target Network, wherein the MS is in communication with a B-Party, wherein the Anchor Network includes an Anchor Base Station (BS), the Anchor MSCe and an Anchor Media Gateway (MGW), and wherein the Target Network includes a Target BS, a Target MSCe and a Target MGW, the Anchor MSCe comprising:

a Target MSCe message interface configured to send a Handoff Request message to the Target MSCe, wherein the Handoff Request message further includes a Session Initiation Protocol (SIP) INVITE message that contains a TIA/EIA-41 FacilitiesDirective2 INVOKE message.

2. The Anchor MSCe of claim 1, wherein the Target MSCe message interface is further configured to receive from the Target MSCe a SIP Provisional Response which contains aTIA/EIA-41 FacilitiesDirective2 RETURN RESULT message.

3. The Anchor MSCe of claim 2, wherein the Target MSCe message interface is further configured to receive from the Target MSCe a SIP 200 OK (INVITE) message indicating that the MS has established a connection with the Target BS.

4. The Anchor MSCe of claim 3, wherein the Anchor MSCe is configured to evaluate if the Anchor MGW can support transcoding between a first codec established for a first termination to the B-Party and a second codec established for a second termination to the Target MGW which will result in a voice bearer that meets or exceeds a pre-established criteria:

if yes, then the Anchor MSCe instructs the Anchor MGW to connect the first termination to the second termination; and

if no, then the Anchor MSCe solicits an SDP offer/answer exchange between the B-Party and the Target MGW to establish a first codec for the first termination to the B-Party and a second codec for the second termination to the Target MGW which will result in a voice bearer that meets or exceeds the pre-established criteria

5. The Anchor MSCe of claim 4 wherein the Anchor MSCe solicits an SDP offer/answer exchange between the B-Party and the Target MOW by:

sending a command to the Anchor MGW to remove the first termination to the B-Party; and

sending a SIP re-INVITE which does not contain a SDP offer to the B-Party; and

receiving a reliable non-failure SIP response message which contains a SDP offer from the B-Party.

6. The Anchor MSCe of claim 5, wherein the Anchor MSCe further solicits an SDP offer/answer exchange between the B-Party and the Target MGW by:

sending a command to the Anchor MGW to modify the second termination to the Target MGW based on a codec list in the SDP offer obtained from the B-Party; and

receiving a reply from the Anchor MGW that contains a local SDP including a list of codecs that are in common with codecs in the codec list in the SDP offer obtained from the B-Party and a list of codecs for which the Anchor MGW can transcode based on the codec list in the SDP offer obtained from the B-Party.

7. The Anchor MSCe of claim 6, wherein the Anchor MSCe further solicits an SDP offer/answer exchange between the B-Party and the Target MGW by:

sending a SIP re-INVITE to the Target MSCe where the SIP re-INVITE contains a SDP offer based upon the local SDP of the second termination from the Anchor MGW to the Target MGW; and

receiving a reliable non-failure SIP response message from the Target MSCe where the reliable non-failure SIP response message contains an SDP answer to the SDP offer.

8. The Anchor MSCe of claim 7, wherein the Anchor MSCe further solicits an SDP offer/answer exchange between the B-Party and the Target MGW by:

sending a command to the Anchor MGW to modify the second termination to the Target MGW based on the SDP answer obtained from the Target MSCe;

sending a command to the Anchor MGW to add the first termination to the B-Party based on the SDP offer received from the B-Party;

receiving a reply from the Anchor MGW that contains a local SDP for the first termination to the B-Party including a list of codecs that are in common with the codec list in the SDP offer obtained from the B-Party and a list codecs for which the Anchor MGW can transcode based on the codec list in the SDP offer obtained from the B-Party;

receiving a reply from the Anchor MGW where the reply contains a local SDP for the second termination to the Target MGW which has a list of codecs that are in common with the codec list in the SDP answer obtained from the Target MSCe and a list of codecs for which the Anchor MGW can transcode based on the codec list in the SDP answer obtained from the Target MSCe; and

sending to the B-Party a SIP Response containing an SDP answer based on the local SDP of the first termination to the B-Party.

9. A method implemented by an Anchor Mobile Switching Center emulation (MSCe) for supporting an intersystem handoff of a Mobile Station (MS) from an Anchor Network to a Target Network, wherein the MS is in communication with a B-Party, wherein the Anchor Network includes an Anchor Base Station (BS), the Anchor MSCe and an Anchor Media Gateway (MGW), and wherein the Target Network includes a Target BS, a Target MSCe and a Target MGW, the method comprising the step of:

sending a Handoff Request message to the Target MSCe, wherein the Handoff Request message further includes a Session Initiation Protocol (SIP) INVITE message that contains a TIA/EIA-41 FacilitiesDirective2 INVOKE message.

10. The method of claim 9, further comprising the step of:

receiving from the Target MSCe a SIP Provisional Response which contains a TIA/EIA-41 FacilitiesDirective2 RETURN RESULT message.

11. The method of claim 10, further comprising the step of:

receiving from the Target MSCe a SIP 200 OK (INVITE) message indicating that the MS has established a connection with the Target BS.

12. The method of claim 11, further comprising the step of evaluating if the Anchor MGW can support transcoding between a first codec established for a first termination to the B-Party and a second codec established for a second termination to the Target MGW which will result in a voice bearer that meets or exceeds a pre-established criteria:

if yes, then instructing the Anchor MGW to connect the first termination to the second termination; and

if no, then soliciting an SDP offer/answer exchange between the B-Party and the Target MOW to establish a first codec for the first termination to the B-Party and a second codec for the second termination to the Target MGW which will result in a voice bearer that meets or exceeds the pre-established criteria.

13. The method of claim 12, wherein the step of soliciting an SDP offer/answer exchange between the B-Party and the Target MGW further comprises:

sending a command to the Anchor MGW to remove the first termination to the B-Party;

sending a SIP re-INVITE which does not contain a SDP offer to the B-Party; and

receiving a reliable non-failure SIP response message which contains a SDP offer from the B-Party.

14. The method of claim 13, wherein the step of soliciting an SDP offer/answer exchange between the B-Party and the Target MGW further comprises:

sending a command to the Anchor MGW to modify the second termination to the Target MGW based on a codec list in the SDP offer obtained from the B-Party; and

receiving a reply from the Anchor MGW that contains a local SDP including a list of codecs that are in common with codecs in the codec list in the SDP offer obtained from the B-Party and a list of codecs for which the Anchor MGW can transcode based on the codec list in the SDP offer obtained from the B-Party.

15. The method of claim 14, wherein the step of soliciting an SDP offer/answer exchange between the B-Party and the Target MGW further comprises:

sending a SIP re-INVITE to the Target MSCe which contains a SDP offer based upon the local SDP of the second termination from the Anchor MGW to the Target MGW; and

receiving a reliable non-failure SIP response message from the Target MSCe where the reliable non-failure SIP response message contains an SDP answer to the SDP offer.

16. The method of claim 15, wherein the step of soliciting the SDP offer/answer exchange between the B-Party and the Target MGW further comprises:

sending a command to the Anchor MGW to modify the second termination to the Target MGW based on the SDP answer obtained from the Target MSCe;

sending a command to the Anchor MGW to add the first termination to the B-Party based the SDP Offer received from the B-Party;

receiving a reply from the Anchor MGW that contains a local SDP for the first termination to the B-Party including a list of codecs that are in common with the codec list in the SDP offer obtained from the B-Party and a list codecs for which the Anchor MGW can transcode based on the codec list in the SDP offer obtained from the B-Party;

receiving a reply from the Anchor MGW where the reply contains the local SDP for the second termination to the Target MGW including a list of codecs that are in common with the codec list in the SDP answer obtained from the Target MSCe and a list codecs for which the Anchor MGW can transcode based on the codec list in the SDP answer obtained from the Target MSCe; and

sending to the B-Party a SIP Response containing an SDP answer based upon the local SDP of the first termination to the B-Party.

17. A Target Mobile Switching Center emulation (MSCe) for supporting an intersystem handoff of a Mobile Station (MS) from an Anchor Network to a Target Network, wherein the MS is in communication with a B-Party, wherein the Anchor Network includes an Anchor Base Station (BS), an Anchor MSCe and an Anchor Media Gateway (MGW), and wherein the Target Network includes a Target BS, the Target MSCe and a Target MGW, the Target MSCEe comprising:

an Anchor MSCe message interface configured to receive a Handoff Request message from the Anchor MSCe, wherein the Handoff Request message further includes a Session Initiation Protocol (SIP) INVITE message that contains a TIA/EIA-41 FacilitiesDirective2 INVOKE message.

18. The Target MSCe of claim 17, wherein the Anchor MSCe message interface is further configured to send to the Anchor MSCe a SIP Provisional Response which contains aTIA/EIA-41 FacilitiesDirective2 RETURN RESULT message.

19. The Target MSCe of claim 18, wherein the Target MSCe is configured to establish bearer resources in the Target MGW and the Target BS.

20. The Target MSCe of claim 19, wherein the Anchor MSCe message interface is further configured to send to the Anchor MSCe a SIP 200 OK (INVITE) message indicating that the MS has established a connection with the Target BS.

21. The Target MSCe of claim 20, wherein the Target MSCe is further configured to:

receive a SIP re-INVITE from the Anchor MSCe where the SIP re-INVITE contains an SDP offer;

send a command to the Target MGW to modify the first termination to the Anchor MGW based on the codec list in the SDP offer;

receive a reply from the Target MGW where the reply contains a local SDP including a list of codecs that are in common with codecs in the codec list in the SDP offer and a list of codecs for which the Target MGW can transcode based on the codec list in the SDP offer; and

send a reliable non-failure SIP response message to the Anchor MSCe where the reliable non-failure SIP response message contains a SDP answer to the SDP offer.

22. A method implemented by a Target Mobile Switching Center emulation (MSCe) for supporting an intersystem handoff of a Mobile Station (MS) from an Anchor Network to a Target Network, wherein the MS is in communication with a B-Party, wherein the Anchor Network includes an Anchor Base Station (BS), an Anchor MSCe and an Anchor Media Gateway (MGW), and wherein the Target Network includes a Target BS, the Target MSCe and a Target MGW, the method comprising the step of:

receiving a Handoff Request message from the Anchor MSCe, wherein the Handoff Request message further includes a Session Initiation Protocol (SIP) INVITE message that contains a TIA/EIA-41 FacilitiesDirective2 INVOKE message.

23. The method of claim 22, further comprising the step of:

sending to the Anchor MSCe a SIP Provisional Response which contains aTIA/EIA-41 FacilitiesDirective2 RETURN RESULT message.

24. The method of claim 23, further comprising the step of:

establishing bearer resources in the Target MGW and the Target BS.

25. The method of claim 24, further comprising the step of

sending to the Anchor MSCe a SIP 200 OK (INVITE) message indicating that the MS has established a connection with the Target BS.

26. The method of claim 25, further comprising the steps of:

receiving a SIP re-INVITE from the Anchor MSCe where the SIP re-INVITE contains an SDP offer; and

sending a command to the Target MGW to modify the first termination to the Anchor MGW based on the codec list in the SDP offer;

receiving a reply from the Target MGW where the reply contains a local SDP including a list of codecs that are in common with codecs in the codec list in the SDP offer and a list of codecs for which the Target MGW can transcode based on the codec list in the SDP offer; and

sending a reliable non-failure SIP response message to the Anchor MSCe where the reliable non-failure SIP response message contains a SDP answer to the SDP offer.