WO2008088126A1

WO2008088126A1 - Method for supporting session mobility of terminal

Info

Publication number: WO2008088126A1
Application number: PCT/KR2007/006274
Authority: WO
Inventors: Jae-Seung Song; Kyung-Ae Yoon; Mi-Seon Ra
Original assignee: Lg Electronics Inc.
Priority date: 2007-01-18
Filing date: 2007-12-05
Publication date: 2008-07-24

Abstract

A method for supporting session mobility of a terminal is disclosed. When a terminal moves from a communication network, information regarding session updating reflecting a current communication environment is provided to a server, to thus performing optimum session mobility.

Description

METHOD FOR SUPPORTING SESSION MOBILITY OF TERMINAL

TECHNICAL FIELD

The present invention relates to supporting of session mobility of a terminal using session mobility mode information.

BACKGROUND ART

In general, when session mobility occurs, for example, when a terminal moves from a WLAN to a UTRAN/GERAN, the terminal generates a VDI (VCC Domain Transfer URI) for non-voice media and an INVITE message having a replace header and also generates a CS SETUP message including a VDN (VCC Domain Transfer Number) for voice media.

When an INVITE message for a VCC is received, an AS (Application

Server) creates a re-l NVITE message with respect to the voice data. When an INVITE for non-voice data is received, the AS creates a re-INVITE message with respect to the non-voice data. Here, the AS is able to combine two operations into a single re-INVITE message, and in this case, a loss in a media flow (similar to the loss in the current VCC) can be minimized. Transmission in a different direction (from the UTRAN/GERAN to the WLAN) may be performed in a nearly similar manner.

Such function may be specified by a VCC application part or something separated therefrom. In any case, the interworking (cooperation) with the VCC and the transmission order of the non-voice data components should be specified to obtain an operation (working) solution with respect to multimedia session handling.

The above-mentioned operation will now be described in detail with reference to FIG. 1. FIG. 1 is an exemplary view showing session mobility support according to the related art. With reference to FIG. 1 , a UE-a maintains a session with a UE-b (S11 ).

The UE-a moves from a WLAN to a UTRAN/GERAN (S12).

As the UE-a moves from the WLAN to the UTRAN/GERAN, UE-a transmits a CS SETUP message via a CS domain to a MGCF to maintain a session with respect to voice over the change of communication network (S13).

The MGCF receives the CS SETUP message and transmits an INVITE request wherein a URI is a VDN (INVITE R-URI=VDN) to an application server (AS) (S 14).

The AS receives the message and transmits re-INVITE to the UE-b in order to establish again a session between the UE-a and the UE-b with respect to voice (S15).

Likewise, when the UE-a moves (or changes) its communication network, the UE-a transmits an INVITE request wherein a URI is a VDI

(INVITE R-URI=VDI) together with a replace header to the AS in order to maintain the session with respect to the non-voice data over the movement of communication network (S16). The AS receives such message and transmits a re-l NVITE to the UE:-b in order to establish again a session between the UE-a and the UE-b with respect to the non-voice data (S 17).

Through such processes, the UE-a and the UE-b can continuously maintain the session.

In supporting session mobility in the related art, when the UE-a moves (or changes) its communication network from the WLAN to the UTRAN/GERAN, the AS may expect to receive an INVITE with respect to voice or an INVITE with respect to non-voice data. Thus, it is ideal that when the AS receives an INVITE via the CS network and an INVITE via the UTRAN/GERAN, the AS simultaneously transmits re-INVITE to the UE-b.

However, the session mobility is dependent upon the radio environment where the UE-a is currently located. Namely, if the UE-a is not in a Multi-RAB/DTM environment supporting the CS and PS dual mode, and if the UE-a cannot be simultaneously connected with the PS (or IMS) domain and the CS domain, even though session mobility occurs, at least one of voice and non-voice data can be lost.

Resultantly, if such radio environment information is not transferred, although the session mobility occurs, it would be difficult for the AS to determine whether to update a session between the UE-a and the UE-b after receiving only one INVITE via the CS domain or via the PS domain, or after receiving both INVITES via the CS domain and the PS domain.

Namely, when the UE-a is in the Multi-RAB/DTM environment, the AS receives two INVITES, but because the AS cannot obtain such radio environment information in advance, it performs session updating between the UE-a and the UE-b based on the first received INVITE and then performs again session updating between the UE-a and the UE-b based on the different INVITE received later. Thus, the AS performs session updating twice, which could have been performed at a single time, causing waste.

TECHNICAL GIST OF THE PRESENT INVENTION

Therefore, it is an object of the present invention to support session mobility of a terminal such that when the terminal moves or changes its communication network, the terminal transfers session mobility mode information to an application server (AS) to thus support optimum session mobility.

Another object of the present invention is to support session mobility of a terminal such that an AS previously stores session mobility mode information, and when a terminal moves or changes its communication network, the terminal transfers radio environment information to the AS, to thus support optimum session mobility.

Still another object of the present invention is to achieve load balancing of a network by allowing an AS to transfer terminal session mode information to a terminal so that the terminal can perform session mobility.

To achieve the above objects, there is provided a method for supporting session mobility of a terminal that moves from a first communication network to a second communication network, the method including: (a) transmitting session mobility mode information to a server via the first communication network or the second communication network; (b) initiating transmission of one or more of voice and non-voice data via the second communication network when an approval message with respect to session mobility according to the session mobility mode information is received from the server.

To achieve the above objects, there is also provided a method for supporting session mobility of a terminal that moves from a first communication network to a second communication network, the method including: (a) receiving a message including session mobility mode information from the terminal; (b) analyzing the session mobility mode information; and (c) performing session updating between the terminal and a counterpart entity (e.g., a counterpart terminal or a service providing server) according to the analysis.

To achieve the above objects, there is also provided a method for supporting session mobility of a terminal that moves from a first communication network to a second communication network, the method including: (a) transmitting a message including radio environment information of the terminal to a server via the first or second communication network; and (b) initiating transmission of one or more of voice or non-voice data via the second communication network, when an approval message corresponding to a type of session updating determined by the server based on the radio environment information of the terminal is received from the server.

To achieve the above objects, there is also provided a method for supporting session mobility of a terminal that moves from a first communication network to a second communication network, the method including: (a) receiving a message including radio environment information of the terminal from the terminal; (b) determining a type of session updating by using the radio environment information included in the message; and (c) updating the session between the terminal and a counterpart entity with the terminal according to the determined type of session updating.

To achieve the above objects, there is also provided a terminal including: a communication module; and a controller that controls the communication module to transmit session mobility mode information or radio environment information to a server via a first or second communication network, when the terminal moves from a first network to an area where it can use a second network.

To achieve the above objects, there is provided an application server that transfers session mobility mode information to a terminal to trigger the terminal to perform session mobility. According to one aspect of the present invention, in case of movement between communication networks, session mobility mode information or radio environment information is provided to an application server (AS), thereby effectively performing session updating without delay. According to another aspect of the present invention, in case of movement between communication networks, session mobility mode information is provided from a first executed domain to the AS, thereby simplifying a procedure of a domain executed thereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary view showing session mobility according to the related art;

FIG. 2 is an exemplary view showing a process of performing session mobility by providing session mobility mode information via a target network according to a first embodiment of the present invention;

FIG. 3 is an exemplary view showing a process of performing session mobility by providing session mobility information through a PS domain of a target network according to a second embodiment of the present invention; FIG. 4 is an exemplary view showing a process of performing session mobility by providing session mobility information through a CS domain of a target network according to the second embodiment of the present invention;

FIG. 5 is an exemplary view showing a process of performing session mobility by providing session mobility information via an original network according to a third embodiment of the present invention;

FIG. 6 is an exemplary view showing a process of moving a single session including voice and non-voice data to a target network, when the UE-a moves from an original network to the target network according to a fourth embodiment of the present invention;

FIG. 7 is an exemplary view showing a process of combining two sessions, namely, a session for voice and a session for non-voice data, into a single session and moving the combined session to a target network, when the UE-a moves from an original network to the target network according to a fifth embodiment of the present invention;

FIG. 8 is an exemplary view showing a process of performing session mobility by providing radio environment information via a target network according to a sixth embodiment of the present invention;

FIG. 9 is an exemplary view showing a process of performing session mobility by providing radio environment information via an original network according to a seventh embodiment of the present invention; and

FIG. 10 is a view showing the construction of a UE and an application server according to the present invention.

MODE FOR CARRYING OUT THE PREFERRED EMBODIMENTS

An exemplary UE (User Equipment) is shown in the accompanying drawings and may be referred to as a terminal, an ME (Mobile Equipment) or the like. In addition, the UE may be a portable device such as a mobile phone, a PDA, a smart phone, a multimedia device, a notebook computer, or the like, or may be a device that cannot be portable such as a PC of a vehicle-mounted device. Before describing the present invention, the techniques and terms used herein will be explained as follows to help understand the present invention.

(1 ) Types of session updates 1 ) Combined session update: This means that when a UE-a (or, terminal) moves to a target network while transmitting and receiving voice data and non-voice data to and from a UE-b via an original network, the UE-a transmits and receives the voice data and the non-voice data in the same manner via the target network. For the combined session update, there can be three cases as follows.

A first case is that when the UE-a moves to the target network comprised of a PS (Packet Switching) domain and CS (Circuit Switching) domain such as a mobile communication network (e.g., UTRAN/GERAN), while transmitting the voice data and the non-voice data in a single session via the original network comprised of a PS (Packet Switching) domain (e.g., a WLAN), the single session can be divided into a CS-based session for the voice data and a PS-based session for the non-voice data and the dived two sessions can be proceeded via the target network. This is called PS to CS+PS. In the first case, in order to update a session, the UE-a should transmit a call set-up message (or a call request message) (e.g., a SETUP message) via the CS domain of the target network (e.g., UTRAN/GERAN) and transmit a session invitation message (or a session initiation request message) (e.g., an SIP-based INVITE message) via the PS domain of the target network (e.g., UTRAN/GERAN). Thus, an application server (referred to as 'AS', hereinafter) does not transmit the session invitation message to the UE-b to update the session until it receives all of the two messages via both the PS and CS domains. Thus, when the AS receives one message only via one domain of the target network, it waits to receive another message via another domain. In this case, the AS may operate a timer (not shown). If the AS does not receive another message via another domain even after the timer expires, the AS transmits the session invitation message to the UE-b based on only the previously received message.

A second case is that when the UE-a moves to a target network comprised of a CS domain and a PS domain such as the mobile communication network (e.g., the UTRAN/GERAN), while transmitting voice data and non-voice data in a single session via an original network comprised of the PS domain (e.g., the WLAN) (or, when the UE-a moves to a target network comprised of a PS domain such as the WLAN while transmitting the voice data and the non-voice data in a single session via only a PS domain in an original network comprised of a CS domain and the PS domain such as the UTRAN/GERAN), the UE-a can transmit the voice data and the non-voice data in the single session via the PS domain of the target network in the same manner. This is called PS to PS. In the second case, in order to update the session, the UE-a transmits a session initiation message (or a session initiation request message) (e.g., an SIP-based INVITE message) via only the PS domain of the target network to update the session. When the AS receives the session invitation message, it immediately transmits the session invitation message to the UE-b.

The third case is the opposite to the first case. Namely, when the UEΞ-a moves to the target network comprised of only PS domain, e.g., the WLAN, while at least two sessions, for example, a CS domain-based session for the voice data and a PS domain-based session for the non-voice data are in progress with the UE-b via the original network comprised of a CS domain and a PS domain, e.g., the UTRAN/GERAN, the two sessions are combined into a single session and the combined session proceeds in the target network. This is called CS+PS to PS. In the third case, the UE-a transmits a single of a session invitation message (or session initiation request message) (e.g., an SIP-based INVITE message) via the target network. Accordingly, when the AS receives the session initiation message, it immediately transmits the session invitation message to the UE-b.

2) Split session update: This means that when the UE-a moves to the target network while transmitting the voice data and the non-voice data via the original network, the UE-a transmits one of the voice data and the non-voice data via the target network and the other via the original network as it is.

In this case, when the AS receives a session invitation message through any one of the PS domain and the CS domain, it immediately transmits the session invitation message.

3) Split session update with dropping: This means that when the UE-a moves to the target network while transmitting the voice data and non-voice data via the original network, if transmission of one of the voice data and the non-voice data is not supported by the target network or if the user or a service provider does not want transmission of particular data to be not continued via the target network, the transmission of one type of data is stopped and only transmission of the other type of data is performed via the target network.

In the same manner as described above, when the AS receives a session invitation message through any one of the PS domain an the CS domain, it immediately transmits the session invitation message to the UE-b.

(2) Session mobility information

This is also referred to as a domain transfer mode (DTM) information.

The session mobility information is used to inform the AS about a type of a session update desired by the UE-a, among the above-mentioned types of session updates. The session mobility information may be provided to the server by a notification message, a feature tag and a VDI/VDN as follows.

1 ) Notification message: This is used to inform the AS which one of the combined session update, the split session update and the split session update with dropping is desired by the UE-a. It can be a notification message or an SIP-based NOTIFY message. Here, when the session update desired by the UE-a is the combined session update, information about whether it is PS to CS+PS, PS to PS, CS+PS to PS may be additionally included. Such notification message may have a different format depending on whether it is transmitted through the CS or the PS.

2) Feature tag

This is a tag attached to the message transmitted through the PS domain or the CS domain in order to inform the AS about a type of session update desired by the UE-e. Examples of the feature tags are as follows. a) Tags attached to a message transmitted through the PS domain

b) Tags attached to a message transmitted through the CS domain

3) Additional tag for VDI (VCC Domain Transfer URI)/VDN (VCC Domain Transfer Number)

In general, VDI is a tag attached to a session initiation message (or session initiation request message) (e.g., an SIP-based INVITE message) by the UE in order to move to the PS domain, and the VDN is a tag attached to a call setup message (or a call origination message) (e.g., a SETUP message) by the UE in order to move to the CS domain. The UE may add an additional tag indicating a type of desired session update to the VDI tag or the VDN tag. Examples of the additional tags for the VDI/VDN are as follows.

a) VDI

b) Tag attached to a message transmitted through the CS domain

(3) Radio environment information

Radio environment information includes information indicating whether the UE supports both a CS-based service and a PS-based service (namely, whether the UE supports Multi-RAB/DTM) and information about whether a network at which the UE is located supports both the CS-based service and the PS-based service (namely, whether the network in which the UE is located supports Multi-RAB/DTM).

When the UE-a moves to the target network, the UE-a transmits the radio environment information, so that the AS can determine which session update is suitable for the UE-a based on the radio environment information, and perform the determined session update.

The radio environment information may be transmitted by being included in the call setup message (or the call origination message) (e.g., the SETUP message), the session invitation message (or session initiation request message) (e.g., the SIP-based INVITE message), or the notification message.

Meanwhile, the AS may receive from the terminal the radio environment information. Or, the AS may receive from a particular entity located in the network the radio environment information of the terminal or information about an available radio access or the like.

When the AS receives the radio environment information, the AS determines which type of session update is suitable for the UE-a based on the radio environment information. And then, the AS transfers, to the terminal, corresponding session mobility information according to the type of the determined session update to trigger the terminal to perform session mobility. Here, the session mobility information may be transmitted to the terminal through a Ut interface, an SMS, a USSD, etc. In the determination, the AS may consider loads of the original and target networks and conduct a load balancing. In order for this, the AS may consider the information regarding registration of the terminal (multiple registration, etc.) and information about an ongoing session.

Upon receiving the session mobility information in such a manner, the terminal performs suitable session mobility. In order to perform the suitable session mobility, the terminal transmits the session invitation message

(SIP-based INVITE message) or call setup message (SETUP message).

Here, the session invitation message or the call message need not include session mobility information, because the session mobility information has been received from the AS.

FIGs. 2 to 9 show seven embodiments of the present invention. To better understand the embodiments, differences among the embodiments will now be described briefly. Schematically, the first to third embodiments as shown in FIGs. 2 to 5 relate to the combined session update, and specifically, relate to the PS to CS+PS update (namely, one session is updated to two sessions) of the combined session update. In detail, the first embodiment as shown in FIG. 2 is for an explanation that the terminal, which moves to the target network, transmits the above-mentioned session mobility information through both the CS and the PS of the target network in order to perform session mobility. The second embodiment as shown in FIGs. 3 and 4 is for an explanation that the terminal, which moves to the target network, transmits the session mobility information through any single domain that can be first accessed among the CS domain and the PS domain of the target network in order to perform session mobility. The third embodiment as shown in FIG. 5 is for an explanation that the terminal, which moves to the target network, transmits the session mobility mode information via the original network in order to perform session mobility. Meanwhile, the fourth embodiment as shown in FIG. 6 relates to the

PS to PS update (namely, one session is updated to one session) of the above-described combined session update, and is for an explanation that the terminal, which moves to the target network, transmits session mobility information via the target network in order to perform session mobility. The fifth embodiment as shown in FIG. 7 relates to the CS+PS to PS update (namely, two sessions are updated to one session) and is for an explanation that the terminal transmits the session mobility information via the target network in order to perform session mobility.

The sixth embodiment as shown in FIG. 8 is for an explanation that radio environment information of the terminal is transferred to the AS via the target network, so that the AS determines the type of session update based on the radio environment information and makes the terminal perform session mobility based on the determined type of session update. The sixth embodiment as shown in FIG. 9 is for an explanation that radio environment information of the terminal is transferred to the AS via the original network, so that the AS determines the type of session update based on the radio environment information and makes the terminal perform session mobility based on the determined type of session update.

FIG. 2 is an exemplary view showing a process of performing session mobility by providing session mobility mode information via a target network according to the first embodiment of the present invention.

The first embodiment relates to the PS to CS+PS update of the combined session update and is for an explanation that the UE-a 110 (or, terminal) transmits session mobility mode information through both the PS domain and the CS domain to perform session mobility.

The first embodiment will be described with reference to FIG. 2 as follows.

1 ) The UE-a 110 performs a session with the UE-b 120, in which voice and non-voice data are combined, via the first network (original network), e.g., the WLAN (S21). 2) The UE-a 110 moves to an area where it can use the second network (target network), e.g., the UTRAN/GERAN (S22). In this case, the second network, e.g., the UTRAN/GERAN, includes the CS domain and the PS domain, and the UE-a 110 can be connected to both domains. Thus, although the UE-a 110 moves to the second network, it is determined that voice data with the UE-b 120 will proceed through the CS domain of the second network and the non-voice data will proceed through the PS domain of the second network (namely, the UE-a 110 desires the combined session update, specifically, the PS to CS+PS of the combined session update).

3) Then, in order to move to the second network the voice data of the session which is now proceeded through the first network such as the WLAN , the UE-a 110 first transmits session mobility information (or also called domain transfer mode information) (the PS to CS+PS of the combined session update in FIG. 2) to an MGCF of the CS domain of the UTRAN/GERAN (S23). In this case, the session mobility information may be transmitted by being included in a call setup message (or a call origination message) (e.g., a SETUP message) as shown. If the session mobility information is included in the call setup message, the session mobility information may be a feature tag (e.g., #12) or an additional tag for the VDN (e.g., +823145019117#12). Or, the session mobility information may be transmitted by being included in the notification message (instead of the call setup message). If the session mobility information is included in the notification message, the session mobility information may be a feature tag (e.g., #12).

4) Then, in response to the reception of the call setup message (SETUP), the MGCF generates a session invitation message (or a session initiation message) (e.g., an SIP-based INVITE message) and transmits it to the AS (S24). In this case, the session invitation message includes the session mobility information. In addition, a header or a body of the session invitation message includes a value having a URI as a VDN (R-URI=VDN).

5) The AS receives the session invitation message (INVITE message) and analyzes the session mobility information included in the message (S25). In this case, the session mobility information indicates the PS to CS+PS of the combined session update, so the AS waits until a different session invitation message is additionally received. Namely, the AS waits to receive two INVITE messages through the PS and CS domains. In this case, the AS may operate an internal timer (not shown). Thus, the AS waits for a certain time set in the timer, and if the session invitation message (INVITE message) is not received until the set time, the AS generates a session invitation message (INVITE message) by using the already received session invitation message (INVITE message) and transmits it to the UE-b 120. 6) Meanwhile, in order to move the non-voice data, which is now proceeded through the first network, to the second network, the UE-a 110 transmits the session mobility information (or the domain transfer mode information) to the AS through the PS domain of the second network, i.e., UTRAN/GERAN (S26). In this case, the session mobility information may be transmitted by being included in the session invitation message (or the session initiation request message) (e.g., the SIP-based INVITE message). Here, the session invitation message includes a replaces header and a value having the URI as the VDI (R-URI=VDI) together with the session mobility information as shown. If the session mobility information is included in the session invitation message, the session mobility information may be a feature tag (e.g., the DTM12) or may be an additional tag for VDI (e.g., domain.xfer@etf1.home1.net#DTM12). Or, as mentioned above, the session mobility information may be transmitted by being included in the notification message or the SIP-based NOTIFY message. When the session mobility information is included in the notification message, it may be a feature tag (e.g., the DTM12). The reason for including the session mobility information in both the call setup message for the voice data and the session invitation message for the non-voice data is because it cannot be known which message would first arrive at the AS, so the AS is allowed to obtain session mobility information from the first arriving message regardless of the arrival order.

7) When the two session invitation messages (INVITE messages) are all received, the AS transmits a session invitation message (re-INVITE) to the UE-b 120 for session updating (S27).

Finally, although not shown, when the UE-b 120 receives the session invitation message, it transmits a response message. Then, the UE-a 110 updates the session with the UE-b 120 and proceeds with the voice session and the non-voice session with the UE-b 120 via the second network (e.g., the UTRAN/GERAN).

Meanwhile, although not shown in FIG. 2, if the UE-a 110 desires to move only one of the voice data or non-voice data to the second network or if the UE-a 110 can be connected to only one of the PS domain and the CS domain of the second network and thus the UE-a 110 can inevitably move only one of the voice and non-voice data to the second network, the UE-a

110 may include the split session update (e.g., DTM30, #30) or the split session update with dropping (e.g., DTM40, #40) in the session mobility information. Then, although the AS receives only a single session invitation message, it transmits the session invitation message (re-INVITE) to the

UEE-b 120.

FIG. 3 is an exemplary view showing a process of performing session mobility by providing session mobility information via the PS domain of a target network according to the second embodiment of the present invention.

The second embodiment as shown in FIG. 3 relates to the PS to CS+PS update of the combined session update and is for an explanation that the UE-a 110 (or, terminal) transmits session mobility mode information through any single domain, to which the UE-a 100 can be first accessed among the CS domain and the PS domain of the target network, in order to perform session mobility. In this case, it should be noted that although the session mobility information is transmitted through any one of the domains, the UE-a 100 should still transmit both a call setup message and a session invitation message through the CS domain and the PS domain.

With reference to FIG. 3, the UE-a 110 proceeds a single session for voice data and non-voice data with the UE-b 120 via the original network, e.g., the WLAN. The UE-a 110 moves to an area where it can use the second network (the target network), e.g., the UTRAN/GERAN. In this case, the second network such as the UTRAN/GERAN, includes the CS domain and the PS domain and the UE-a 110 can be connected with both the domains (in this case, the UE-a 110 may be first connected to the PS domain then to the CS domain). Thus, although the UE-a 110 moves to the target network such as UTRAN/GERAN, it is determined that voice data with the UE-b 120 will proceed through the CS domain of the target network and the non-voice data will proceed through the PS domain of the target network (namely, the UE-a 110 desires the combined session update, specifically, the PS to CS+PS of the combined session update).

1 ) In order to move non-voice data in the session from the original network such as the WLAN to the second network (target network), i.e., the UTRAN/GERAN, the UE-a 110 transmits session mobility information (or domain transfer mode information) to an S-CSCF#1 (S301 ). In this case, the session mobility information may be transmitted by being included in a session invitation message (or session initiation request message) (e.g., an SIP-based INVITE message). Here, the session invitation message includes a replace header and a value having a URI as a VDI (R-URI=VDI) together with the session mobility information. If the session mobility information is included in the session invitation message, the session mobility information may be a feature tag (e.g., DTM12) or may be an additional tag (e.g., domain.xfer@dtf1.home1.net#DTM12) for the VDI. Or, the session mobility information may be transmitted by being included in a notification message or an SIP-based NOTIFY message.

2) Then, the S-CSCF#1 transmits the INVITE message received from the UE-a 1 10 to the AS (S302).

3) The AS analyzes whether the received INVITE includes the session mobility information and performs logic operations (S303). Namely, when the AS determines that the combined session update (specifically, PS to CS+PS) is requested upon analyzing the session mobility information, the AS waits to additionally receive a different session message (INVITE message). 4) The AS transmits a response message, e.g., an Ack message, or an SIP-based 200 OK message, with respect to the INVITE (S304).

5) In order to move voice data in the session from the original network such as the WLAN to the target network, the UE-a 110 transmits a call setup message (or call origination message) (e.g., a SETUP message) to an MSC

(Mobile Switching Center) of the CS domain of the UTRAN/GERAN (S305).

6) ~ 8) Then, the MSC transmits an ISUP/IAM message to the MGCF in response to the reception of the SETUP message (S306). Then, in response to the reception, the MGCF generates a session invitation message (e.g., an SIP-based INVITE message) and transmits it to the

S-CSCF#1 (S307). Then, the S-CSCF#1 transmits the session invitation message to the AS (S308).

9) ~ 11 ) When the AS receives both the session invitation message (INVITE message) for the non-voice data and a session invitation message for the voice data, the AS generates a session invitation message

(re-INVITE message) based on the two messages (S309) and transmits it to the UE-b 120 via the S-CSCF#2 (S310 and S311).

12) ~ 13) In response to the reception of the session invitation message (re-INVITE message), the UE-b 120 transfers a response message (or an accept message), e.g., a SIP-based 200 OK message, to the AS via the S-CSCF#2 (S312 and S313).

14) ~ 16) Upon receiving the response message (200 OK message), the AS splits the response message (200 OK message) into a response message (200 OK message) for the voice data and a response message (200 OK message) for the non-voice data, and transmits the response message (200 OK message) for the non-voice data to the UE-a 110 via the S-CSCF#1 of the PS domain (S314) and the response message (200 OK message) for the voice data to the S-CSCF#1 (S315).

17) ~ 19) The S-CSCF#1 transmits the response message for the voice data to the MGCF (S317). Then, in response to the reception of the response message (200 OK), the MGCF transmits an ISUP/IAM message to the UE-a 110 via the MSC of the CS domain (S318 and S319).

Then, the UE-a 110 updates the session with the UE-b 120, and can perform a voice session with the UE-b 120 through the CS domain of the second network (e.g., the UTRAN/GERAN) and can perform a non-voice session with the UE-b 120 through the PS domain of the second network. Meanwhile, although not shown in FIG. 3, if the type of the session update is the split session update, the session mobility information may be, for example, DTM30 or #30. Or, in case of the split session update with dropping, the session mobility information may be, for example, DTM40 or #40. In such split session update with dropping, although the AS receives only one session invitation message, it transmits the session invitation message (re-INVITE) to the UE-b 120.

FIG. 4 is an exemplary view showing a process of performing session mobility by providing session mobility information via the CS domain of the target network according to the second embodiment of the present invention.

The second embodiment as shown in FIG. 4 relates to the PS to CS-PS update of the combined session update and is for an explanation that the UE-a 110 (or, terminal) transmits the session mobility information through only the CS domain, to which the UE-a 110 can be first connected among the CS domain and the PS domain of the target network, in order to perform session mobility. The description for the second embodiment is similar to the process as shown in FIG. 3, thus such would also be applicable to the second embodiment.

FIG. 5 is an exemplary view showing a process of performing session mobility by providing session mobility information via the original network according to a third embodiment of the present invention.

The third embodiment as shown in FIG. 5 relates to the PS to CS+PS update of the combined session update and is for an explanation that the

UEΞ-a 110 (or, terminal) transmits session mobility mode information through the original network to perform session mobility. In this case, it is noted that although the session mobility mode information is transmitted via the original network, the UE-a 100 should still transmit a call setup message and a session invitation message via the target network, namely, through the CS domain and the PS domain of the UTRAN/GERAN.

The third embodiment of the present invention will now be described with reference to FIG. 5.

1 ) The UE-a 110 progresses a session (in which voice and non-voice data are combined) with the UE-b 120 via the first network (original network), e.g., the WLAN (S51).

2) The UE-a 110 moves to an area where it can use (access) the second network (target network), e.g., the UTRAN/GERAN (S52). In this case, the second network, e.g., the UTRAN/GERAN, includes the CS domain and the PS domain, and the UE-a 110 can be connected with both of the two domains. Thus, although the UE-a 110 moves to the UTRAN/GERAN, it is determined that voice data with the UE-b 120 will proceed through the CS domain and the non-voice data with the UE-b 120 will proceed through the PS domain (namely, the UE-a 110 desires the combined session update, specifically, the PS to CS+PS of the combined session update).

3) Then, the UE-a 110 transmits session mobility information (or domain transfer mode information) to the AS via the original network (namely, the WLAN) (S53). In this case, the UE-a 110 may transmit the session mobility information to the AS by using an Ut interface formed with the AS via the original network e.g., WLAN. The Ut interface is an interface between the UE-a (or, terminal) and the server and XCAP may be used as its communication protocol. As mentioned above, the session mobility information may be transmitted by being included in a notification message or an SIP-based NOTIFY message. If the session mobility information is included in the notification message, the session mobility information may be a feature tag (e.g., DTM 12). 4) In order to move the voice data in the session from the WLAN to the target network, the UE-a 110 first transmits a call setup message (or a call origination message) (e.g., an SETUP message) to the MGCF of the CS domain (S54). 5) Then, in response to the reception of the call setup message (SETUP), the MGCF generates a session invitation message (or session initiation request message) (e.g., an SIP-based INVITE message) and transmits it to the AS (S55). In this case, a header or a body of the session invitation message includes a value having a URI as a VDN (R-URI=VDN).

6) The AS receives the session invitation message (INVITE message) and analyzes the session mobility information received in step S52 (S56).

In this case, the session mobility information is relates to the PS to CS+PS OF the combined session update, so the AS additionally waits to receive a different session invitation message. The AS operates a timer (not shown) and waits for a certain time, but if the INVITE is not received until them, the AS executes session updating using only the already received INVITE with the UE-b. 7) In order to move the non-voice data IN the session from the WLAN to the target network (or, second network), the UE-a 110 transmits a session invitation message (or a session initiation request message) (e.g., an SIP-based INVITE message) to the AS (S57). Here, as shown, the session invitation message includes a replaces header and a value having the URI as the VDI (R-URI=VDI).

8) When the AS receives both of the two session invitation messages (INVITE messages), the AS transmits a session invitation message (re-INVITE) to the UE-b 120. Finally, although not shown, when the UE-b 120 receives the session invitation message, it transmits a response message. Then, the UE-a 110 updates the session with the UE-b120 and proceeds the voice session and the non-voice session with the UE-b 120 via the target network (or, second network) (e.g., the UTRAN/GERAN).

FIG. 6 is an exemplary view showing a process of moving a single session including voice and non-voice data to a single session in the same manner, when moving from the original network to the target network according to a fourth embodiment of the present invention. The fourth embodiment as shown in FIG. 6 relates to the PS to PS update of the combined session update and is for explanation that the UE-a (or, terminal) transmits session mobility information via the target network to perform session mobility.

As shown, when the session mobility information is transmitted by being included in a session invitation message (or a session initiation request message) (e.g., an SIP-based INVITE message), the session mobility information may be a feature tag (e.g., DTM11 ) or may be an additional tag (e.g., domain.xfer@dtf1.home1.net#DTM11 ) for the VDI. Or, as mentioned above, when the session mobility information is transmitted by being included in a notification message or an SIP-based NOTIFY message, the session mobility information may be a feature tag (e.g, DTM11).

When the AS receives the session mobility information, it immediately transmits a session invitation message (INVITE message) to the UE-b 120. Other matters are similar to the case as shown in FIG. 2, so its repetitive description will be omitted.

Meanwhile, although not shown, if the type of a session update is the split session update, the session mobility information may be, for example, DTM30 or #30. Or, in case of the split session update with dropping, the session mobility information may be DTM40 or #40.

Meanwhile, although not shown, the session mobility information may be transmitted via the original network.

FIG. 7 is an exemplary view showing a process of combining two sessions, namely, a session for voice data and a session for non-voice data, into a single session and moving the same, when moving from the original network to the target network according to a fifth embodiment of the present invention.

The fifth embodiment as shown in FIG. 7 relates to the CS+PS to PS update of the combined session update and is for explanation that the UE-a (or terminal) transmits session mobility mode information via the target network to perform session mobility.

In this case, when the session mobility information is transmitted by being included in a session invitation message (or a session initiation request message) (e.g., an SIP-based INVITE message), the session mobility information may be a feature tag (e.g., DTM21 ) or may be an additional tag (e.g., domain.xfer@dtf1.homel .netw#DTM21 ) for the VDI. Or, when the session mobility information is transmitted by being included in the notification message or the SIP-based NOTIFY message, the session mobility information may be a feature tag (e.g., DTM21).

When the session mobility information is received, the AS immediately transmits a session invitation message (INVITE message) to the UE-b 120.

Other matters are similar to FIG. 2, so they will not be described.

Meanwhile, although not shown in FIG. 7, if the type of the session update is the split session update, the session mobility information may be

DTM30 or #30. Or if the type of the session update is the split session update with dropping, the session mobility information may be, for example,

DTM40 or #40.

Meanwhile, although not shown in FIG. 7, the session mobility information may be transmitted via the original network. When the session mobility information is transmitted via the original network, it may be transmitted through both the PS domain and the CS domain or through only one of them as shown in FIGs. 3 and 4.

FIG. 8 is an exemplary view showing a process of performing session mobility by providing radio environment information via the target network according to a sixth embodiment of the present invention. The sixth embodiment as shown in FIG. 8 is for an explanation that the UE-a (or, terminal) transmits radio environment information of itself to the AS via the target network, so that the AS determines the type of session update based on the radio environment information and makes the terminal perform session mobility based on the determined type of session update.

Such will be described in detail as follows.

1) The UE-a 110 progresses a session with UE-b in which voice and non-voice data are combined through the first network (the original network) (S81).

The UE-a 110 moves to an area where it can use the second network (the target network), e.g., the UTRAN/GERAN (S82). In this case, the second network, e.g., the UTRA/GERAN includes the CS domain and the PS domain (namely, the second network provides Multi-RAB/DTM), and the UE-1 110 can be connected with both of the two domains (namely, the UE-a supports the Multi-RAB/DTM). Thus, the radio environment information includes such matters.

3) Then, the UE-a 110 transmits the radio environment information to an MGCF through the CS domain of the UTRAN/GERAN (S83). In this case, the radio environment information may be transmitted by being included in a call setup message (or a call origination message) (e.g., a SETUP message). Or, the radio environment information may be transmitted by being included in the notification message as mentioned above.

4) In response to the reception of the call setup message (SETUP), the MGCF generates a session invitation message (or a session initiation request message) (e.g., an SIP-based INVITE message) and transmits it to the AS (S84). In this case, the session invitation message includes the radio environment information. 5) Upon receiving the session invitation message (INVITE message), the AS analyzes the radio environment information included in the session invitation message and determines a type of a session update according to the radio environment information (S85). In this case, if the determined type of session update is the PS to CS+PS of the split session update, the AS waits to additionally receive a different session invitation message.

6) The UE-a 110 transmits the radio environment information to the AS through the PS domain of the UTRAN/GERAN (S86). In this case, the radio environment information may be transmitted by being included in a session invitation message (or a session initiation request message) (e.g., an SIP-based INVITE message) as shown. Or, the radio environment information may be transmitted by being included in a notification message or an SIP-based NOTIFY message.

7) When the AS receives the two session invitation messages (INVITE messages), it transmits a session invitation message (re-INVITE) message to the UE-b 120.

Finally, although not shown, when the UE-b 120 receives the session invitation message, it transmits a response message. Then, the UE-a 110 updates the session with the UE-b 120 and proceeds with a voice session and a non-voice session with the UE-b 120 via the second network

(UTRAN/GERAN).

Meanwhile, FIG. 8 shows that the UE-a 110 transmits the radio environment information through both the PS domain and the CS domain of the target network, e.g., the UTRAN/GERAN. However, the radio environment information can be transmitted through only one of the domains as shown in FIGs. 3 and 4.

Also, in FIG. 8, the AS determines the PS to CS+PS of the combined session update as the type of session update according to the radio environment information. However, the AS may determine the PS to PS of the combined session update as the type of session update.

Although not shown in FIG. 8, if the target network, e.g., the UTRAN/GERAN, may support a transmission of only one of either voice data or non-voice data, and the radio environment information includes such matters, then the AS may determine the split session update or the split session update with dropping as the type of session update according to the radio environment information.

Although not shown in FIG. 8, the sixth embodiment of the present invention may be applicable to the embodiment of FIG. 7 in which the original network is UTRAN/GERAN and the target network is WLAN.

FIG. 9 is an exemplary view showing a process of performing session mobility by providing radio environment information via the original network according to a seventh embodiment of the present invention. The seventh embodiment as shown in FIG. 9 is for an explanation that the UE-a transmits the radio environment information of itself to the AS via the original network, so that the AS can determine the type of session update based on the radio environment information and make the terminal perform session mobility accordingly.

The seventh embodiment of the present invention can be sufficiently understood by those skilled in the art with reference to FIGs. 5 and 8, so its detailed description will be omitted. The methods according to the present invention described thus far can be implemented as software, hardware or their combination. For example, the method according to the present invention may be stored in a storage medium (e.g., an internal memory of a mobile terminal, a flash memory, a hard disk, and the like), and may be implemented as codes or commands in a software program that can be executed by a processor (e.g., an internal microprocessor of the mobile terminal).

The UE 100 according to the present invention as shown in FIG. 10 corresponds to the UE-a 110 and the UE-b120 as shown in FIGs. 2 to 9. The UE 100 and the AS 500 will now be described and any descriptive content with respect to FIGs. 2 to 9 will be applicable.

The UE 100 may include a first communication module 101 , a second communication module 102, and a controller 103. The first communication module 101 may be comprised of various electronic components that can be used to access the first network, e.g., IEEE 802.11 (or WLAN) or IEEE 802.16 type network.

The second communication module 102 may be comprised of various ekϊctronic components that can be used to access the second network, e.g., CDMA, GSM, GPRS, TDMA, IMT-2000, WCDMA, HSDPA, UTRAN/GERAN networks.

The controller 103 controls the first and second communication modules 101 and 102. Specifically, when the UE 100 moves from the first network (the original network) to an area where it can use the second network (target network), the controller checks the radio environment information.

The controller 103 determines the type of session update according to the checked radio environment information. As shown in FIGs. 2 to 7, the controller 103 controls the first communication module 101 to transmit session mobility mode information to the AS via the first network (original network) or controls the second communication module 102 to transmit the session mobility mode information to the AS via the second network (target network) according to the determined type of the session update.

Or, as shown in FIGs. 8 and 9, the controller 103 controls the first communication module 101 to transmit the checked radio environment information to the AS via the first network (original network), or controls the second communication module 102 to transmit the checked radio environment information to the AS via the second network (target network).

Other matters regarding the first communication module 101 , the second communication module 102, and the controller 103 can be easily implemented by those skilled in the art to which the present invention pertains with reference to the present specification, so its detailed description will be omitted.

The AS 500 includes a communication module 601 and a controller 502. As shown in FIGs. 2 to 7, characteristically, the UE 100 may receive the session mobility mode information. Or, as shown in FIGs. 8 and 9, the communication module 501 may receive the radio environment information from the UE 100. When the session mobility mode information is received, the controller 502 analyzes the session mobility information. When the combined session update is checked according to analysis of the session mobility information, the controller 502 waits until two session invitation messages (e.g., the SIP-based INVITE message). In this case, as mentioned above, the controller 502 may drive the timer.

When the radio environment information is received, the controller 502 analyzes the radio environment information and determines a type of the session update.

Other matters regarding the communication module 501 and the controller 502 can be easily implemented by those skilled in the art to which the present invention pertains with reference to the present specification, so its detailed description will be omitted.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

1. A method for supporting session mode mobility of a terminal that moves from a first communication network to a second communication network, the method comprising:

(a) transmitting session mobility mode information to a server via the first communication network or via the second communication network; and

(b) initiating transmission of one or more of voice data and non-voice data via the second communication network when an approval message with respect to session mobility according to the session mobility mode information is received from the server.

2. The method of claim 1 , wherein the session mobility mode information is transmitted by being included in at least one of a call setup message, a session invitation message and a notification message.

3. The method of claim 2, wherein the call setup message corresponds to a SETUP message, the session invitation message corresponds to an SIP-based INVITE message, and the notification message corresponds to an SIP-based NOTIFY message.

4. The method of claim 1 , wherein the session mobility information is transmitted by being included in a feature tag, or in an additional tag for a VDI (VCC Transfer Domain URI) or a VDN (VCC Transfer Domain Number).

5. The method of claim 1 , wherein the first communication network may be a WLAN, or the second communication network may be a UTRAN/GERAN.

6. The method of claim 1 , wherein if the first communication network or the second communication network is a UTRAN/GERAN, the session mobility mode information is transmitted via one or more of a CS domain and a PS domain of the UTRAN/GERAN.

7. The method of claim 1 , wherein if the first communication network is the WLAN, the session mobility mode information is transmitted via the WLAN, or the session mobility mode information is transmitted through a Ut interface between the terminal and the server via the first communication network.

8. The method of claim 1 , wherein the session mobility mode information includes one of a combined session update, a split session update and a split session update with dropping.

9 The method of claim 8, wherein, in case of the combined session update, the session mobility mode information further includes at least one of information indicating PS to CS+PS, information indicating PS to PS₁ and information indicating CS+PS to CS.

10. The method of claim 8, wherein, in the initiating step, in case of the combined session update, transmission of both voice data and non-voice data via the second communication network is initiated, in case of the split session update, transmission of one of voice data and non-voice data via the first communication network is maintained while transmission of the other of voice data and non-voice data via the second communication network is initiated, and in case of the split session update with dropping, transmission of one of voice data and non-voice data via the first communication network is dropped while transmission of the other of voice data and non-voice data via the second communication network is initiated.

11. The method of claim 1 , wherein the server is an application server (AS).

12. A method for supporting session mobility of a terminal that moves from a first communication network to a second communication network, the method comprising:

(a) receiving a message including session mobility mode information from the terminal; (b) analyzing the session mobility mode information; and

(c) performing session updating between the terminal and a counterpart entity according to the analysis.

13. The method of claim 12, wherein the message is at least one of a call setup message, a session invitation message and a notification message.

14. The method of claim 12, wherein the session mobility information is received by being included as a feature tag in the message, or being included as an additional tag for a VDI (VCC Transfer Domain URI) or a VDN (VCC Transfer Domain Number) in the message and.

15. The method of claim 12, wherein the session mobility mode information includes one of a combined session update, a split session update and a split session update with dropping.

16. The method of claim 15, wherein in case of the combined session update, the session mobility mode information further includes at least one of information indicating PS to CS+PS, information indicating PS to PS, and information indicating CS+PS to CS.

17. The method of claim 12, further comprising, if the combined session update is determined according to the analysis, waiting for a certain time to receive an additional message from the terminal; and generating and transmitting to the counterpart entity a new message based on a previously received message and an additional message, when the additional message is received within the certain time.

18. A method for supporting session mobility of a terminal that moves from a first communication network to a second communication network, the method comprising:

(a) transmitting a message including radio environment information of the terminal to a server via the first or second communication network; and

(b) initiating transmission of one or more of voice data or non-voice data via the second communication network, when an approval message corresponding to a type of session updating determined by the server based on the radio environment information of the terminal is received from the server.

19. The method of claim 18, wherein the message may be at least one of a call setup message, a session invitation message and a notification message.

20. The method of claim 19, wherein the call setup message may be a SETUP message, the session invitation message may be an SiP-based INVITE message, and the notification message may be an SIP-based NOTIFY message.

21. The method of claim 18, wherein when the first communication network or the second communication network is a UTRAN/GERAN, the radio environment information is transmitted through one or more of the CS domain and the PS domain of the UTRAN/GERAN in step (a).

22. The method of claim 18, wherein the types of session updates include one or more of a combined session update, a split session update and a split session update with dropping.

23. The method of claim 18, wherein if the first communication network is a WLAN, the radio environment information is transmitted via the

WLAN, or the radio environment information is transmitted through a Ut interface between the terminal and the server via the first communication network.

24. A method for supporting session mobility of a terminal that moves from a first communication network to a second communication network, the method comprising:

(a) receiving, from the terminal, a message including radio environment information of the terminal;

(b) determining a type of session updating by using the radio environment information included in the message; and

(c) updating a session between the terminal and a counterpart entity with the terminal according to the determined type of session updating.

25. The method of claim 25, wherein the message corresponds to at least one of a call setup message, a session invitation message and a notification message.

26. A terminal comprising: a communication module; and a controller that controls the communication module to transmit session mobility mode information or radio environment information to a server via a first or second communication network, when the terminal moves from a first network to an area where access to a second network is possible.

27. The terminal of claim 26, wherein the session mobility mode information or the radio environment information is transmitted by being included in at least one of a call setup message, a session invitation message and a notification message.

28. The terminal of claim 27, wherein the call setup message may be a SETUP message, the session invitation message may be an SIP-based INVITE message, and the notification message may be an SIP-based NOTIFY message.

29. The terminal of claim 26, wherein the session mobility information is transmitted by being included in a feature tag or by being included in an additional tag for a VDD (VCC Transfer Domain URI) or a VDN (VCC Transfer Domain Number).