This application claims the benefit under 35 U.S.C. § 119(a) of application Serial No. 2005-36406, filed in the Korean Intellectual Property Office on Apr. 29, 2005 and application Serial No. 2005-36408, filed in the Korean Intellectual Property Office on Apr. 29, 2005, the entire disclosures of both of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to a system and method for voice data handoff between a cellular network and a WiBro/WLAN network in a heterogeneous network environment. More particularly, the present invention relates to a system and method which seamlessly provide a 3rd generation (3G) voice service to a mobile terminal while it moves between a cellular network and a Wireless Broadband (WiBro, also known as “Portable Internet”) network or a wireless local area network (WLAN) in an Internet protocol Multimedia Subsystem (IMS)-based heterogeneous network environment.
2. Description of the Related Art
In the following description, the heterogeneous networks include a cellular network (CDMA 2000 1X system) and a WiBro network, by way of example. IMS in the cellular network is a core technology for providing users with ubiquitous services, such as wire/wireless integrated service, voice/data integrated service, and communication/broadcasting convergence service, in a broadband integrated network. IMS users can exchange with each other multimedia contents, such as pictures, video clips, and sound clips, through session-based messages. For example, the session-based message includes a Session Initiation Protocol (SIP) message.
The major functional elements of a core network subsystem for MBS service include a Call Session Control Function (CSCF), a Home Subscriber Server (HSS), a Media Gateway Control Function (MGCF), and an IMS-Media Gateway (IMS-MGW). The CSCF performs a call and session processing-related function, and is classified into a Proxy CSCF (P-CSCF), an Integrating CSCF (I-CSCF), and a Serving CSCF (S-CSCF) according to its function.
The P-CSCF is an element for performing a gateway function when a terminal first accesses the network to receive MBS service, and performs a Proxy and User Agent function. Basically, the P-CSCF replays SIP messages between the terminal and the network. The I-CSCF serves as a contact point for all calls incoming to connect with subscribers in the network, and inquires of an HSS for location detection of a called subscriber before routing a call. In addition, the I-CSCF, as it serves as a gateway with another IMS network, also serves as a firewall for hiding a topology in the network for security.
The S-CSCF performs, during its registration, a Register function and various authentication functions necessary therefor. The S-CSCF performs a series of mechanisms for directly interworking with application servers to provide various multimedia services, routing a call based on triggering information, and providing services.
The MGCF, located in the contact point between an IMS network and a Public Switch Telephone Network/Plain Land Mobile Network (PSTN/PLMN) network, takes charge of interworking a call, and performs an SIP and ISDN User Part (ISUP) signaling protocol translation function according thereto. The MGCF performs a function of managing and controlling resources in the IMS-MGW for call processing.
The IMS-MGW, an MGW used in the IMS network, performs a function of converting IP packet media data into the format that can be transmitted on a bearer of a circuit switched network in order to interwork with the PSTN/PLMN network, and performs such functions as transcoding and echo canceling, for that purpose.
The HSS, an evolved type of the conventional Home Location Register (HLR), is an addition of an Authentication Center (AuC) function to the conventional HLR function. The HSS is a subscriber's master database for managing user number-related information, location information, and service profile information.
Meanwhile, the core functional elements of the WiBro network include a Radio Access Station (RAS) and an Access Control Router (ACR). The RAS provides a wireless access function, a wireless resource management and control function, and a handoff support function of Portable Internet (WiBro). The ACR provides IP routing and mobility management functions.
The issue in the foregoing vertical handoff (or handoff between heterogeneous networks) process is a handoff time and a packet loss caused by the handoff. Therefore, an efficient interworking scheme between the heterogeneous networks should be able to minimize the handoff time and the packet loss. However, there has been no standard defined for the handoff procedure necessary for the case where a user receiving voice service in a heterogeneous network environment moves from the cellular network to the WiBro/WLAN network, making it impossible to perform fast handoff between the heterogeneous networks.
Accordingly, there is a need for an improved system and method for voice data handoff between a cellular network and a WiBro/WLAN network in a heterogeneous network environment.
Exemplary embodiments of the present invention address at least the above problems and/or disadvantages and provide at least the advantages described below. It is, therefore, an exemplary object of the present invention to provide a system and method which provide seamless voice service when a mobile terminal moves between cellular coverage and Portable Internet (WiBro) coverage in a heterogeneous network environment.
According to an exemplary aspect of the present invention, a system and method are provided for performing voice data handoff from a cellular network to a portable Internet/wireless local area network (WLAN) network by a mobile terminal in a heterogeneous network environment. The system and method are provided wherein, whether to perform handoff of the mobile terminal is determined and a location of the terminal in the portable Internet/WLAN network is registered, a request for handoff to the cellular network is sent, and in response thereto a request for voice-over-Internet protocol (VoIP) call setup through a specific upper node of the portable Internet/WLAN network is received, and the VoIP call to the upper node of the portable Internet/WLAN network is set up, and resources of a circuit voice call to a specific upper node of the cellular network are released.
According to another exemplary aspect of the present invention, there are provided a system and method for performing voice data handoff to a cellular network by a first mobile terminal among the first mobile terminal located in a portable Internet/wireless local area network (WLAN) network and a second mobile terminal located in the portable Internet/WLAN network or the cellular network in a heterogeneous network environment. The system and method are provided in which the first mobile terminal determines whether it has entered the cellular network and its location in the cellular network according to the determination result is registered, the first mobile terminal sends a request for handoff to a specific upper node of the portable Internet/WLAN network, and the upper node of the portable Internet/WLAN network sets up a circuit voice call of the first mobile terminal to the cellular network through a specific upper node of the cellular network.
The above and other objects, features and advantages of the exemplary embodiments of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:
Several exemplary embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for clarity and conciseness.
Referring to
The DBDM mobile terminal and a Base Station System (BSS) of the cellular network according to an exemplary embodiment of the present invention have the following requirements.
The DBDM mobile terminal, in cellular coverage, receives information indicating the presence or absence of a WiBro cell through an overhead message. The DBDM transmits a Pilot Strength Measurement Message (PSMM) to the BSS of the cellular network if signal strength of a Pseudo Noise (PN) value from a cellular base station overlapping with a WiBro base station exceeds a threshold. Upon recognizing the presence of the WiBro cell, the DBDM terminal activates a WiBro modem. The DBDM terminal, after activating the WiBro modem, registers at the WiBro network and performs location registration (WiBro-CDMA dual-activated state) in an IMS network.
The BSS of the cellular network manages a cellular-WiBro cell overlapping area with a neighbor list. The BSS inserts an indicator in an overhead message and sends the overhead message to the DBDM mobile terminal in order to indicate the presence of the WiBro cell. If a PN sequence transmitted by the DBDM mobile terminal is a cell identifier (ID) of the cellular-WiBro cell overlapping area, a request for hard handoff is sent to a Mobile Switching Center (MSC).
In the first exemplary embodiment, described with reference to
Referring to
In step 304, the BTS/BSC transmits a Handoff Required message to an MSC. In step 305, the MSC transmits a FacilitiesDirective (FACDIR) message indicating a start of a handoff procedure to an MGC of an IMS network if a target Cell ID included in the Handoff Required message overlaps with the WiBro cell. Upon receiving the FACDIR message, the MGC selects a channel and determines available media capacity through communication with an IMS-MGW.
In step 306, the MGC uses a Mobile Identification Number (MIN) of the MT1 as an SIP Uniform Resource Locator (URL), and delivers the MIN and an ESN of the MT1 to an I-CSCF along with an SIP INVITE message. In step 307, the I-CSCF queries an HSS about an address of an S-CSCF that takes charge of a session of an MT2, and receives an address of the S-CSCF from the HSS. In step 308, the I-CSCF transmits an INVITE message to the S-CSCF. The S-CSCF determines whether this session setup is appropriate. In steps 309 and 310, the INVITE message is delivered to the MT1 via a P-CSCF. At this moment, the MT1 recognizes an IP and a port number of an MGW, included in an SDP.
In step 311, the MT1 transmits an SIP 2000K message indicating connection of a voice call, to the MGC. In step 312, the MGC delivers a FACDIR message to the MSC because a Voice-over-IP (VoIP) session to the handoff requiring MT1 is set up. In steps 313 and 314, the MSC receiving the FACDIR message exchanges Handoff Command/Handoff Commenced messages defined in the International Organization for Standardization (IOS) standard with the source BTS/BSC. However, the 3G BTS/BSC may not transmit a Handoff Direction message to the MT1 and may include a Proprietary Field in the Handoff Command message in order to simulate as if it transmitted the Handoff Direction message to the MT1. In step 315, the MGC transmits an ACK message to the MT1.
In step 316, if a channel to the MT1 and a voice path between the MSC and the trunk are completely set up, the MGC transmits an MSONCH message to the MSC. In step 317, the MSC transmits a Clear Command message to the BTS/BSC to request release of resources for the corresponding call.
Referring to
In the exemplary embodiment described with reference to
Referring to
In step 604, the BTS/BSC transmits a Handoff Required message to an MSC of the cellular network. In step 605, the MSC transmits a FacilitiesDirective (FACDIR) message indicating a start of a handoff procedure to an MGC of an IMS network if a target Cell ID included in the Handoff Required message overlaps with the WiBro cell. Upon receiving the FACDIR message, the MGC selects a channel and determines available media capacity through communication with an IMS-MGW.
In step 606, the MGC uses a MIN of the MT1 as an SIP URL, and delivers the MIN and an ESN of the MT1 to an I-CSCF along with an SIP INVITE message. In step 607, the I-CSCF queries an HSS about an address of an S-CSCF that takes charge of a session of an MT2, and receives an address of the S-CSCF from the HSS. In step 608, the I-CSCF transmits an INVITE message to the S-CSCF. The S-CSCF determines whether this session setup is appropriate. In steps 609 and 610, the INVITE message is delivered to the MT1 via a P-CSCF. At this moment, the MT1 recognizes an IP and a port number of an MGW, included in an SDP.
In step 611, the MT1 transmits an SIP 2000K message indicating connection of a voice call, to the MGC. In step 612, the MGC delivers a FACDIR message to the MSC because a VoIP session to the handoff requiring MT1 is set up. In steps 613 and 614, the MSC receiving the FACDIR message exchanges Handoff Command/Handoff Commenced messages defined in the IOS standard with the source BTS/BSC. However, the 3G BTS/BSC may not transmit a Handoff Direction message to the MT1, and may include a Proprietary Field in the Handoff Command message in order to simulate as if it transmitted the Handoff Direction message to the MT1. In step 615, the MGC transmits an ACK message to the MT1.
In step 616, the MGC transmits a FacilitiesRelease (FACREL) message to the MSC in order to request release of the trunk to the MSC. In step 617, upon receiving the FACREL message, the MSC changes the trunk into an idle state through communication with the MGW, and responds to the FACREL message. In step 618, the MSC transmits a Clear Command message to the BTS/BSC to request release of resources for the corresponding call.
Referring to
Referring to
In the third exemplary embodiment, described with reference to
Referring to
In step 905, the MT1 transmits a re-INVITE message for the current VoIP SIP session. The re-INVITE message has a Session ID of the current session, a Target Cell ID, and an Indicator indicating the ongoing handoff to the cellular network, all of which are included in a predetermined field of its Body. A P-CSCF performs a Network Initiated Session Release procedure for the MT1 and the MT2, upon receiving a re-INVITE Request message with a handoff indicator.
In steps 906 to 908, upon receiving the re-INVITE Request message, an MGC sets up a new session to the MT2.
In step 909, the MGC transmits a FACDIR message indicating a start of a handoff procedure to an MSC of a target cell ID network. In steps 910 to 912, upon receiving the FACDIR message, the MSC transmits a Handoff Request message to a target BSC. After allocating resources of a target BTS, the target BSC transmits a response message to a target MSC in response to the handoff request. In step 913, the MSC transmits a FACDIR message to the MGC to notify its completed preparation for the handoff. In this case, the MSC transmits channel information of the target cell together.
In step 914, upon receiving the FACDIR message, the MGC transmits a 200 OK message indicating a start of handoff to the MT1 along with the channel information. In step 915, the MT1 transmits an ACK message in response to the 2000K message.
In step 916, the MT1 performs handoff to the cellular network using the channel information, and transmits a message indicating completion of the handoff procedure to the target BTS/BSC. In step 917, the target BSC delivers a message indicating completion of the handoff procedure to the target MSC. In step 918, the target MSC transmits a Mobile Station on Channel (MSONCH) message indicating completion of the voice path setup up to the mobile terminal to the MGC.
Referring to
Referring to
In the fourth exemplary embodiment, described with reference to
Referring to
In step 1205, the MT1 transmits a re-INVITE message for the current VoIP SIP session. The re-INVITE message has a Session ID of the current session, a Target Cell ID, and an Indicator indicating the ongoing handoff to the cellular network, all of which are included in a predetermined field of its Body. A P-CSCF performs a Network Initiated Session Release procedure for the MT1 and the MT2, upon receiving a re-INVITE Request message with a handoff indicator.
In step 1209, an MGC transmits a FACDIR message indicating a start of a handoff procedure to an MSC of a target Cell ID network.
In steps 1210 to 1212, upon receiving the FACDIR message, the MSC transmits a Handoff Request message to a target BSC. The target BSC allocates resources of a target BTS, and then transmits a response message to a target MSC in response to the handoff request.
In step 1213, the MSC transmits an FACDIR message to the MGC to indicate its completed preparation for the handoff. In this case, the MSC transmits channel information of the target cell together. In step 1214, upon receiving the FACDIR message, the MGC transmits a 2000K message indicating a start of handoff to the MT1 along with the channel information.
In step 1215, the MT1 transmits an ACK message in response to the 2000K message. In step 1216, the MT1 performs handoff to the cellular network using the channel information, and transmits a message indicating completion of the handoff procedure to the target BTS/BSC. In step 1217, the target BSC delivers a message indicating completion of the handoff procedure to the target MSC.
In step 1218, the target MSC transmits a FACREL message to the MGC to request release of the trunk to the MGC. In step 1219, upon receiving the FACREL message, the MGC changes the trunk into an idle state through communication with the MGW, and responds to the FACREL message.
Referring to
Referring to
As can be understood from the foregoing description, the exemplary embodiments of the present invention propose a system and method for fast handoff process between a cellular network and a Portable Internet (WiBro), thereby securing competitive one-phone service.
In addition, the exemplary embodiments of the present invention allow a circuit network service provider to simply launch wire/wireless integrated voice service.
Further, the exemplary embodiments of the present invention can serve as a catalytic technology for activating the wire/wireless integrated voice service.
While the invention has been shown and described with reference to a certain exemplary embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and the full scope of equivalents thereof.
Number | Date | Country | Kind |
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2005-36406 | Apr 2005 | KR | national |
2005-36408 | Apr 2005 | KR | national |