This application is based on European Patent Application No. 09305340.3 filed Apr. 21, 2009, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is hereby claimed under 35 U.S.C. §119.
The present invention generally relates to mobile communication networks and systems.
Detailed descriptions of mobile communication networks and systems can be found in the literature, in particular in Technical Specifications published by standardisation bodies such as for example 3GPP (3rd Generation Partnership Project).
Single Radio Voice Call Continuity SRVCC is specified in particular in 3GPP TS 26.216 specification. SRVCC provides voice call continuity between IP Multimedia Subsystem IMS over Packet Switched PS access and Circuit Switched CS access for calls that are anchored in IMS when the User Equipment UE is capable of transmitting/receiving on only one of those access networks at a given time.
3GPP TS 23.216 specifies SRVCC between E-UTRAN access and 3GPP2's 1xCS, and between E-UTRAN access and 3GPP's UTRAN/GERAN accesses and between UTRAN (HSPA) access and 3GPP's UTRAN/GERAN accesses, for CS calls that are anchored in the IP Multimedia Subsystem IMS.
For example, SRVCC from E-UTRAN to GERAN procedure, as specified in 3GPP TS 23.216, is recalled in
Generally, there is a need to improve SRVCC functionality. In particular, there is a need to reduce communication breaks occurring during SRVCC procedure such as for example SRVCC from E-UTRAN to GERAN procedure recalled in
Embodiments of the present invention in particular address such needs.
These and other objects are achieved, in one aspect of the present invention, in an embodiment, by a method for the reduction of flow break in Single Radio Voice Call Continuity SRVCC mobility for a User Equipment UE, SRVCC mobility including Hand-Over HO execution procedure and Voice Call Continuity VCC procedure, said method comprising a step of:
delaying HO execution at the UE, to coordinate HO execution procedure and VCC procedure.
These and other objects are achieved in other aspects of the present invention, by a User Equipment, and by network entities (including entities of Radio Access Network RAN such as E-UTRAN or UTRAN (HSPA) for example, as well as entities of Core Network such as CS Core Network and Evolved Packet Core EPC or PS Core Network for example) configured for carrying out such method.
Some embodiments of apparatus and/or methods in accordance with embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings, in which:
SRVCC from E-UTRAN to GERAN procedure as recalled in
SRVCC procedure such as for example SRVCC from E-UTRAN to GERAN procedure, as illustrated in
Elements illustrated in
MSC Server/MGW: Mobile Switching Center Server/Media Gateway, where MSC Server corresponds to MSC Server enhanced for SRVCC, in particular MSC Server invoking the Session Transfer procedure, and coordinating the HO procedure and the Session Transfer procedure,
VCC procedure in the example illustrated in
HO execution procedure in the example illustrated in
Generally, a HO command (ordering HO to an UE) to be sent on the radio interface between the UE and the network, is built by the Target RAN and sent to the UE while the UE is still in the Source RAN (the HO command being carried transparently in messages sent to the UE via the Source RAN)
In the example illustrated in
In the example of
Embodiments of the present invention that will be described hereinafter are based in particular on the following ideas.
SRVCC procedure is invoked when a mobile, that is engaged in an IMS/sip call/session with a voice component, has to move from a source radio coverage where Voice over IP is carried over the radio towards a target radio coverage where the voice bearer needs to be carried by the CS domain, i.e. controlled by a MSC (server). SRVCC procedure is standardized for GERAN, UTRAN and 1xRTT CDMA2000 target systems.
During this procedure, the address to which the remote terminal environment sends voice traffic towards the mobile has to be changed from the address used on the source radio into the address used to reach the MSC (server)/MGW that will serve the mobile after the mobility event has taken place.
In order for SRVCC procedure to work in the case where the mobile has got only one radio chain working at a given time (“Single Radio”) the responsible network node (the new MSC (server) allocated to the UE) issues the two following parallel procedures after having reserved Radio Access Network resources on the Target Radio Subsystem i.e.
1. Changing the path between the moving mobile and the Core Network: i.e. ordering the mobile to tune its radio to the target cell i.e. to stop camping on the source radio and to start camping on the target radio. The message sent by the source Radio Access Network to the mobile is called a Hand-Over Command in the present application even though the actual message sent to the mobile may depend on the Radio Access Technology (GERAN, UTRAN, E-UTRAN, . . . )
2. Changing the path between the remote UE and the Core Network: i.e. issuing a VCC procedure (Voice Call Continuity), also called Session Transfer, in which a call to a specific Application Server (AS) sitting on IMS is initiated, in order for this application server (SCC AS) to update the remote terminal environment with the new address to which voice traffic towards the moving mobile should be sent.
Both procedures have impacts on the transmission path used to carry voice traffic between the UE that moves and the remote UE. As soon as one path has been changed, the UE that moves and the remote UE are no more able to exchange voice traffic until the other path has been changed.
The issue is that nothing synchronizes those 2 events occurring at different places of the network
1. The change of radio tuning by the moving mobile is carried out locally and its duration depends on radio conditions and on the load of the target Radio Subsystem;
2. The VCC procedure is carried out remotely and its duration depends on the differences in performance in a multi-vendor environment, on whether the UE is roaming or not (different IMS signalling), and on the load of the IMS network as well as on the load of the remote terminal environment;
As those events are not synchronized then there is the risk that they happen consecutively (with very likely the radio re-tuning happening first) instead of simultaneously, thus bringing a long service interruption delay.
In current SRVCC R8 procedure, the Session Transfer is initiated by the MSC (server) at the same Time Tstart than the change of radio is commanded by the MSC (server) towards the UE.
The break in communication depends on when the PS “break” occurs and when the CS “make” occurs, as illustrated in
Thus following scenarios are possible for what events determine the break in communication between the UE's:
1. Tupdate is less than Tcscon (the interruption time is Tcscon−Tleave)
2. Tupdate is greater than Tcscon (the interruption time is Tupdate−Tleave)
For scenario 1 the existing procedures seem sufficient to minimize the communication break and the service interruption time corresponds roughly to the one experienced today in case of a native CS domain inter-BSS/UTRAN mobility.
Thus, it is worth optimizing the procedures (or minimizing the break) in scenario 2 as this is the most likely case.
A possible approach might be as follows.
As illustrated in
One of the reasons why this does not work properly is that sometimes sending the Hand-Over command cannot be delayed due to radio conditions dwindling too rapidly. Delaying the sending of the Hand-Over command would in those cases mean losing the UE, as in those cases, the UE may be no more reachable over the source radio when the Hand-Over command is actually sent.
Embodiments of the present invention described hereinafter in particular enable to avoid drawbacks of such possible approach.
In an embodiment, illustrated in
The UE itself may delay tuning to the new RAN, even though it has received the HO command. This solution allows:
The UE may decide when to tune according to following algorithms:
A further optimization of this variant, illustrated in
The message corresponding to this notification of path establishment depends on the actual network call control signalling protocol used by the MSC (server) for the call associated with the VCC procedure (it may be an ISUP, a BICC or SIP appropriate message (ACM, ANM, 200 OK . . . )).
Thus, as can be seen from
In an embodiment, the present invention provides that the Hand-Over Command is sent to the UE as soon as possible i.e. in parallel with the launch of the VCC procedure. But this Hand-Over command contains a new parameter—a delay whereby the mobile is assumed to wait for the completion of the delay before actually carrying out the change of radio camping, unless local radio conditions at the mobile make it mandatory to carry out the Hand-Over at once to avoid a call drop.
Various embodiments of the present invention are considered in the following:
1) During the SRVCC procedure, a delay parameter is added to the Hand-Over command message sent over the source radio to the UE, and the HO execution procedure is delayed accordingly by the UE, as illustrated in
A UE conforming to an embodiment of the present invention, sets a timer with the value received from the Hand-Over command and then waits to actually carry out the change of cell camping for the first of following events to happen
2) As an improvement of this procedure, it is the MSC (server) that determines this delay parameter added to the Hand-Over command message and passes its value to the source Radio Access Network along with the request of starting the Hand-Over execution phase. This makes it possible to have the value of this delay depending on global network conditions such as whether the mobile is roaming from a far country, from a neighbour country or not roaming.
The delay value may also be adapted to the Radio Access Technology (3G, LTE, . . . ) of the source radio (i.e. of the radio on which the Hand-Over command is to be sent).
3) Another associated improvement of the synchronization can be performed by the following mechanism: the MSC (server) sends the Hand-Over command with the delay as soon as possible i.e. in parallel with the launch of the VCC procedure as described above, as illustrated at step 13 in figure—(the HO command then being sent by the Source MME to the Source E-UTRAN at step 14, and by the Source E-UTRAN to the UE at step 15). Later on when it is notified that the path between its MGW and the remote UE environment has been established, the MSC (server) sends another Hand-Over Command message with delay=zero (or no delay parameter), as also illustrated at step 13 in
A UE conforming to an embodiment of the present invention, sets a timer with the value received from the Hand-Over command and then waits to actually carry out the change of cell camping for the first of following events to happen
This mechanism allows preventing that a too long delay set by the MSC (server) in the first Hand-Over command would make the UE start changing of radio camping too late, thus increasing the flow break instead of reducing it
The message corresponding to this notification of path establishment depends on the actual network call control signalling protocol used by the MSC (server) for the call associated with the VCC procedure (it may be an ISUP, a BICC or SIP appropriate message (ACM, ANM, SIP 200 OK . . . )).
4) Same principles apply for SRVCC from E-UTRAN and 1xRTT where the 1xCS IWS plays the role of the Serving MSC as described in TS 23.216.
5) When the source Radio Access Network is an Evolved UTRAN (E-UTRAN), the Radio Access Network is an Evolved Node B (ENB) and is controlled via a Mobility management Entity (MME) defined in 3GPP TS 23.401. When the source Radio Access Network is an UTRAN, the Radio Access Network is made up of a RNC and a Node B and is controlled by a SGSN. All these functional entities are further defined in 3GPP TS 23.002. Other source Radio Access Networks may also support embodiments of the invention.
6) In case of Hand-Over from E-UTRAN to legacy 3gpp coverage (GSM, UTRAN), the message flow from the MSC (server) towards the UE via the radio takes the form of
In an embodiment, the delay parameter is added to each of those messages.
7) A mobile not conforming to embodiments of the present invention does not take into account the delay parameter added to the Hand-Over command message received over radio and acts per 3GPP TS 23.216 Rel-8.
In order to avoid a mobile not conforming to embodiments of the present invention to experience a too long flow break, a specific delay can be added in the source Radio Access Network for these mobiles. To achieve this differentiation between a mobile that conforms to embodiments of the present invention from a mobile that does not, the mobile that conforms to embodiments of the present invention can also notify its capability to the network together, for example via a new parameter in the existing “UE Radio Capabilities” defined in e.g. 3GPP TS 25.306 for UTRAN and TS 36.306 for E-UTRAN.
In one aspect, in an embodiment, the present invention provides a method for the reduction of flow break in Single Radio Voice Call Continuity SRVCC mobility for a User Equipment UE, SRVCC mobility including Hand-Over HO execution procedure and Voice Call Continuity VCC procedure, said method comprising a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, at least one message including signaled delay information, corresponds to a message carrying a HO command.
In an embodiment, signaling delay information includes signaling a delay parameter, followed if necessary by signaling a command ordering immediate HO execution.
In an embodiment, signaling a command ordering immediate HO execution includes signaling a delay parameter with a value zero.
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of:
In an embodiment, said method comprises a step of, in the case of SRVCC from a source Radio Access Network RAN corresponding to E-UTRAN to a target RAN corresponding to GERAN or UTRAN :
In an embodiment, said method comprises a step of, in the case of SRVCC from a source Radio Access Network RAN corresponding to E-UTRAN to a target RAN corresponding to GERAN or UTRAN:
In an embodiment, said method comprises a step of, in the case of SRVCC from a source Radio Access Network RAN corresponding to E-UTRAN to a target RAN corresponding to GERAN or UTRAN:
In an embodiment, said method comprises a step of, in the case of SRVCC from a source Radio Access Network RAN corresponding to an UTRAN to a target RAN corresponding to GERAN or UTRAN:
In an embodiment, said method comprises a step of, in the case of SRVCC from a source Radio Access Network RAN corresponding to an UTRAN to a target RAN corresponding to GERAN or UTRAN:
In an embodiment, said method comprises a step of, in the case of SRVCC from a source Radio Access Network RAN corresponding to an UTRAN to a target RAN corresponding to GERAN or UTRAN:
In another aspect, there is provided a network entity, configured to perform such method.
In an embodiment, the present invention provides a network entity configured, for the reduction of flow break in Single Radio Voice Call Continuity SRVCC mobility for a User Equipment UE, SRVCC mobility including Hand-Over HO execution procedure and Voice Call Continuity VCC procedure:
In an embodiment, said network entity is configured:
In an embodiment, a network entity in charge of said coordination is configured:
In an embodiment, at least one network entity in charge of signaling is configured:
In an embodiment, a network entity in charge of signaling is configured:
In an embodiment, a network entity in charge of signaling is configured:
In an embodiment, at least one message including signaled delay information, corresponds to a message carrying a HO command.
In an embodiment, signaling delay information includes signaling a delay parameter, followed if necessary by signaling a command ordering immediate HO execution.
In an embodiment, signaling a command ordering immediate HO execution includes signaling a delay parameter with a value zero.
In an embodiment, a network entity in charge of said coordination is configured:
In an embodiment, a network entity in charge of said coordination is configured:
In an embodiment, network entity in charge of said coordination is configured:
In an embodiment, a network entity in charge of said coordination is configured:
In an embodiment, a network entity in charge of said coordination is configured:
In an embodiment, the present invention provides, in the case of SRVCC from a source Radio Access Network RAN corresponding to E-UTRAN to a target RAN corresponding to GERAN or UTRAN, a MSC Server configured:
In an embodiment, the present invention provides, in the case of SRVCC from a source Radio Access Network RAN corresponding to E-UTRAN to a target RAN corresponding to GERAN or UTRAN, a Mobility Management Entity MME configured:
In an embodiment, the present invention provides, in the case of SRVCC from a source Radio Access Network RAN corresponding to E-UTRAN to a target RAN corresponding to GERAN or UTRAN, an Evolved Node B ENB configured:
In an embodiment, the present invention provides, in the case of SRVCC from a source Radio Access Network RAN corresponding to an UTRAN to a target RAN corresponding to GERAN or UTRAN, a MSC Server configured:
In an embodiment, the present invention provides, in the case of SRVCC from a source Radio Access Network RAN corresponding to an UTRAN to a target RAN corresponding to GERAN or UTRAN, a Serving GPRS Support Node SGSN configured:
In an embodiment, the present invention provides, in the case of SRVCC from a source Radio Access Network RAN corresponding to an UTRAN to a target RAN corresponding to GERAN or UTRAN, an Node B configured:
In another aspect, the present invention provides a User Equipment, configured for performing such method.
In an embodiment, the present invention provides, a User Equipment UE configured, for the reduction of flow break in Single Radio Voice Call Continuity SRVCC mobility for a User Equipment UE, SRVCC mobility including Hand-Over HO execution procedure and Voice Call Continuity VCC procedure:
In an embodiment, said User Equipement UE is configured:
In an embodiment, said User Equipement UE is configured:
In an embodiment, said User Equipement UE is configured:
In an embodiment, at least one message including signaled delay information, corresponds to a message carrying a HO command.
In an embodiment, signaling delay information includes signaling a delay parameter, followed if necessary by signaling a command ordering immediate HO execution.
In an embodiment, signaling a command ordering immediate HO execution includes signaling a delay parameter with a value zero.
In an embodiment, said User Equipement UE is configured:
In an embodiment, said User Equipement UE is configured:
In an embodiment, said User Equipement UE is configured:
In an embodiment, said User Equipement UE is configured:
The detailed implementation of the above-mentioned means does not raise any special problem for a person skilled in the art, and therefore such means do not need to be more fully disclosed than has been made above, by their function, for a person skilled in the art.
A person of skill in the art would readily recognize that steps of various above-described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods.
Number | Date | Country | Kind |
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093053403 | Apr 2009 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2010/054190 | 3/30/2010 | WO | 00 | 2/17/2012 |