Method for providing roaming service among private mobile switching centers

Abstract: Disclosed is a method for providing a roaming service among private mobile switching centers (MSCs) interconnected to one another via a public switched telephone network (PSTN). The method comprises connecting the private mobile switching centers to a virtual private network (VPN) via the PSTN; if a mobile station sends a private mobile communication service registration request to a selected one of the private mobile switching centers, storing, by the selected private mobile switching center, information about the mobile station registered for the private mobile communication service and associated mobile station location information; transmitting the mobile station information and the mobile station location information to other private mobile switching centers via the virtual private network; and if the mobile station sends a private mobile communication service request to a selected one of the private mobile switching centers, providing, by the selected private mobile switching center, the private mobile communication service using the stored mobile station information and mobile station location information, and the virtual private network.

Description: The present invention relates generally to a mobile communication system, and in particular, to a method and corresponding system for providing a roaming service among private mobile switching centers. In general, private (or local) mobile switching centers (MSCs) provide the mobile communication service only to the mobile subscribers registered therein. Therefore, the mobile subscribers cannot be provided with the mobile communication service, when they move into a service area (or coverage area) of a private mobile switching center in which they are not registered. That is, a mobile subscriber registered in a certain private mobile switching center can be provided with a call originating service, a call terminating service and other additional services only in a service area of the private mobile switching center. Utilization of a virtual private network in a mobile communication system is described in the following references: U. S. Patent No. 6,029,067 to Matthias Pfundstein entitled Virtual Private Network for Mobile Subscribers ; U.S. Patent No. 6,101,382 to Christer Granberg entitled Transfer of Calling Party Identification in a Mobile Communication System ; and U.S. Patent No. 6,175,622 to Sima Chiniwala et al. entitled Virtual Private Network for a Telephone Network . A private network system and mobile radio telephones that enable moving from one private branch exchange to a different is described in US 5479483 A. Roaming from one micro cellular communication network to another micro cellular communication network for a mobile subscriber unit is disclosed in WO 9939527. It is, therefore, the object of the present invention to provide a method for providing a roaming service among private mobile switching centers. According to an aspect of the present invention, there is provided a method for enabling a mobile subscriber to be provided with a call terminating service and a call originating service in any service area of a plurality of private mobile switching centers. To achieve the above object, there is provided a method for providing a roaming service among private mobile switching centers (MSCs) interconnected to one another via a public switched telephone network (PSTN). The method comprises connecting the private MSCs to a virtual private network (VPN) via the PSTN; if a mobile station sends a private mobile communication service registration request to a selected one of the private MSCs, storing, by the selected private MSC, information about the mobile station registered for the private mobile communication service and associated mobile station location information; transmitting the mobile station information and the mobile station location information to other private MSCs via the VPN; and if the mobile station sends a private mobile communication service request to a selected one of the private MSCs, providing, by the selected private MSC, the private mobile communication service using the stored mobile station information and mobile station location information, and the VPN. To further achieve the above object, there is provided a corresponding system for providing a roaming service among a plurality of private mobile switching centers. A more complete appreciation of the present invention, and many of the attendant advantages thereof, will become readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: FIG. 1 is a diagram illustrating the connection between private mobile switching centers; FIG. 2 is a diagram illustrating a network structure for providing a roaming service among private mobile switching centers according to an embodiment of the present invention; FIG. 3 is a detailed block diagram illustrating the call managers shown in FIG. 2; and FIG. 4 is a flow chart illustrating a procedure for providing a roaming service among private mobile switching centers according to an embodiment of the present invention. Referring to FIG. 1, private mobile switching centers 2 and 12 are connected in common to a public switched telephone network (PSTN) 10. Further, the private mobile switching centers (MSCs) 2 and 12 include radio interfaces (I/F) 4 and 14, respectively. The private mobile switching center 2 provides the mobile communication service only to mobile stations (MSs) 6 and 8 registered therein, while the private mobile switching center 12 provides the mobile communication service only to mobile stations 16 and 18 registered therein. Therefore, when the mobile stations 16 and 18 registered in the private mobile switching center 12 move into a service area 20 of the mobile switching center 2, they cannot be provided with the mobile communication service. Likewise, when the mobile stations 6 and 8 registered in the private mobile switching center 2 move into a service area 22 of the mobile switching center 12, they cannot be provided with the mobile communication service. The private mobile switching centers and shown in FIG. 1 are chiefly designed to manage in-building mobile switching, so that they cannot be connected to a public mobile communication network. FIG. 2 shows a network structure for providing a roaming service among private mobile switching centers according to an embodiment of the present invention. Referring to FIG. 2, a public mobile communication network 33 includes a mobile switching center (MSC) 38, a plurality of base station controllers (BSCs) 40-1 to 40-N, and a plurality of base station transceiver subsystems (BTSs) 42-1 to 42-N. A public mobile communication network 53 includes a mobile switching center (MSC) 58, a plurality of base station controllers (BSCs) 60-1 to 60-N, and a plurality of base station transceiver subsystems (BTSs) 62-1 to 62-N. A public mobile communication network 73 includes a mobile switching center (MSC) 78, a plurality of base station controllers (BSCs) 80-1 to 80-N, and a plurality of base station transceiver subsystems (BTSs) 72-1 to 72-N. A plurality of private mobile switching centers 30, 50 and 70 are connected to the public mobile communication networks 33, 53 and 73, respectively. As illustrated, the private mobile switching centers 30, 50 and 70 share public/private common cells 36, 56 and 76 with their associated public mobile communication networks 33, 53 and 73, respectively. That is, the base station transceiver subsystems (BTSs) 42-N, 62-N and 72-N in the public/private common cells 36, 56 and 76 are commonly used for both the public mobile communication service and the private mobile communication service. The other cells serviced by the BTSs of the public mobile communication networks 33, 53 and 73, except the public/private common cells 36, 56 and 76, are used as public-only cells 37, 57 and 77, as shown in FIG. 2. In FIG. 2, the private mobile switching centers 30, 50 and 70 include radio interfaces (I/F) 31, 51 and 71, respectively, and are connected to their associated public mobile communication networks 33, 53 and 73 via the radio interfaces 31, 51 and 71. To connect the private mobile switching centers 30, 50 and 70 to their associated public mobile communication networks 33, 53 and 73, there are provided call managers 32, 52 and 72, which include message (MSG) routers 34, 54 and 74, respectively. In FIG. 2, the message routers 34, 54 and 74 are separated from the call managers 32, 52 and 72, for convenience of explanation. However, it is preferable that the message routers 34, 54 and 74 are included in the call managers 32, 52 and 72, respectively. The message routers 34, 54 and 74 are connected to the BTSs 42-N, 62-N and 72-N in the public/private common cells 36, 56 and 76, respectively, and also connected to the base station controllers (BSCs) 40-N, 60-N and 80-N, respectively, which are upper BSCs of the BTSs 42-N, 62-N and 72-N. In addition, the message routers 34, 54 and 74 are also connected to the private mobile switching centers 30, 50 and 70, respectively. The message routers 34, 54 and 74 analyze such event messages as a call origination message, a call termination message, a location registration message and an SMS (Short Message Service) message, and then, designate a path according to the analyzed results. The message routers 34, 54 and 74 each have a router table, in which the designated path information is mapped with the associated events, and transmit a received message to a related device by consulting the router table. The call managers 32, 52 and 72 are connected to the private mobile switching centers 30, 50 and 70 via a local area network (LAN). The call managers 32, 52 and 72 analyze the messages received from the message routers 34, 54 and 74 to determine whether the received messages are for the public mobile communication service or the private mobile communication service, and then, perform the service control according to the determined results. FIG. 3 shows a detailed structure of the call managers 32, 52 and 72 of FIG. 2. Referring to FIG. 3, the call manager includes a private BSC 92 and a private MSC 94 corresponding to the BSC and the MSC of the public mobile communication network, and has a VLR (Visitor Location Register) 96, connected to the private MSC 94, for registering mobile stations intended to be provided with the private mobile communication service. Further, the call manager has a database (DB) 98 connected to the private BSC 92. In addition, the call manager includes a radio interface 99 connected to the private MSC 94, for communication with its associated private mobile switching center. Turning back to FIG. 2, the private mobile switching centers 30, 50 and 70 are connected in common to the PSTN 44. In order to provide the roaming service among the private mobile switching centers 30, 50 and 70 according to an embodiment of the present invention, the private mobile switching centers 30, 50 and 70 are connected in common to a virtual private network (VPN) via the PSTN 44. FIG. 4 shows a procedure for controlling a roaming service among the private mobile switching centers 30, 50 and 70 connected to the virtual private network. Now, a method for providing the roaming service among the private mobile switching centers 30, 50 and 70 according to an embodiment of the present invention will be described in detail with reference to FIGs. 2 to 4. For the roaming service among the private mobile switching centers 20, 50 and 70, information about the mobile stations registered for the private mobile communication service and location information of the registered mobile stations are stored in each VLR 96 of the call managers 32, 52 and 72 associated with the private mobile switching centers 30, 50 and 70 connected to the virtual private network. The mobile station location information includes information about a virtual private network prefix for the private mobile switching center where the mobile station is located. After storage of the mobile station location information, the information about the mobile stations registered for the private mobile communication service and the location information of the registered mobile stations are also sent to the call managers associated with the other mobile switching centers connected to the virtual private network. The detailed description will be given below. The call managers 32, 52 and72 manage the mobile stations registered for the private mobile communication service using their VLR 96 shown in FIG. 3. If a new mobile station is registered for the private mobile communication service, the call manager for the associated public/private common cell provides the information about the mobile stations registered for the mobile communication service to the call managers associated with the private mobile switching centers connected to the virtual private network. If, for example, a new mobile station located in the public/private common cell 36 is registered in the call manager 32 for the private mobile communication service, the call manager 32 provides the information about the mobile stations registered for the private mobile communication service to the call managers 52 and 72 associated with the private mobile switching centers 50 and 70 connected to the virtual private network, through the private mobile switching center 30 and the PSTN 44. The other call managers 52 and 72 then store the information about the mobile stations registered for the private mobile communication service in their VLR 96, together with the mobile station location information. In this state, if a certain mobile station moves into a public/private common cell of another private mobile communication network, the call manager for this public/private common cell updates the mobile station location information stored in its VLR 96 through the location registration process or the call origination process, and provides the updated mobile station location information to the call managers associated with the other private mobile switching centers connected to the virtual private network. The call managers then update the mobile station location information stored in their VLR 96. In the state where the mobile station information and the associated mobile station location information are stored and updated in the call managers 32, 52 and 72 so as to enable the roaming service among the private mobile switching centers, an originating call from the mobile station belonging to any one of the public/private common cells 36, 56 and 76 is managed in the common process for the mobile originating call. Distinguishing the private mobile communication service from the public mobile communication service is performed by the call managers 32, 52 and 72. After a mobile communication network to provide the mobile communication service is determined by the call managers 32, 52 and 72, a message is provided to the determined mobile communication network to perform the call service. Meanwhile, a terminating call in the public mobile communication networks 33, 53 and 73 is managed in the common call terminating process of the public mobile communication network, and the call managers 32, 52 and 72 provide the received message intact to the BTSs 42-N, 62-N and 72-N. On the other hand, a terminating call in the private mobile communication network is provided to the call managers 32, 52 and 72. The call managers 32, 52 and 72 then receive a call termination request message in step 200 of FIG. 4, and consult their VLR 96 in step 202. More specifically, when the terminating call is provided to the MSC 94 of the call managers 32, 52 and 72, the MSC 94 acquires the location information of the corresponding mobile station by consulting the VLR 96, to thereby detect a location of the mobile station. After step 202, the call managers 32, 52 and 72 determine in step 204 whether the location of the mobile station belongs to their public/private common cells or another public/private common cell. If the location of the mobile station belongs to their public/private common cells, the call managers 32, 52 and 72 perform the call termination process in step 206. Otherwise, if the location of the mobile station belongs to another public/private common cell, a call termination message is provided to the corresponding mobile station through the roaming service among the private mobile switching centers according to an embodiment of the present invention. More specifically, if it is determined in step 204 that the location of the mobile station belongs to another public/private common cell, the call managers 32, 52 and 72 search in step 208 the VLR 96 for a virtual private network prefix corresponding to the private mobile communication network where the mobile station is located. Thereafter, in step 210, the call managers 32, 52 and 72 transmit the call termination message to the private mobile communication network where the mobile station is located, by consulting the searched virtual private network prefix. More specifically describing the operation performed in step 210, the call managers 32, 52 and 72 transmit the call termination request message to a target private mobile switching center in the private mobile communication network where the mobile station is located, through their associated message routers 34, 54 and/or 74, private mobile switching centers and the PSTN. The call manager for the target mobile switching center then performs the call terminating service through steps 200 to 206. As described above, the mobile subscriber registered in both the public mobile communication network and the private mobile communication network can be provided with the call originating service, call terminating service and other additional services, even though the mobile subscriber moves to any cell where the private mobile switching center sharing the public/private common cell with the public communication network is connected to the virtual private network. In addition, it is also possible to service not only a call terminated in a specific area but also a call terminated in another area through the PSTN. While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein, e.g., although the invention has been described with reference to the roaming service among the private mobile switching centers in a system providing both the public mobile communication service and the private mobile communication service, the invention can also be applied to a roaming service among the private mobile switching centers connected to the virtual private network.

Claims: A method for providing a roaming service among a plurality of private mobile switching centers (30, 50, 70), associated with a corresponding plurality of private mobile communication networks, interconnected to one another via a public switched telephone network, comprising the steps of: connecting the private mobile switching centers to a virtual private network via said public switched telephone network; storing, at a selected one of said private mobile switching centers, information about a mobile station registered for a private mobile communication service and associated mobile station location information, when said mobile station sends a private mobile communication service registration request to said selected one of said private mobile switching centers via a base station transceiver subsystem (42-N, 62-N, 72-N) shared by the public mobile communication network and a private mobile communication network associated with the selected one of said private mobile switching centers; transmitting the mobile station information and the mobile station location information from said selected one of said private mobile switching centers to the remaining private mobile switching centers via the virtual private network; and providing the private mobile communication service to said mobile station, by a predetermined one of said private mobile switching centers, using the stored mobile station information and mobile station location information, and the virtual private network, when said mobile station sends a private mobile communication service request to said predetermined one of the private mobile switching centers via one of a plurality of base station transceiver subsystems shared by the public mobile communication network and the private mobile communication networks. A method of claim 1, wherein the plurality of private mobile switching centers has associated call managers (32, 52, 72) and an associated common cell area for public and private network communications and each of said private mobile switching centers is connected in common to a virtual private network via a common public switching telephone network, said method further comprising: registering said mobile station in one of said call managers associated with a predetermined one of said private mobile switching centers for private mobile communication service, when said mobile station is in the associated common cell area of said predetermined one of said private mobile switching centers; providing, from said one of said call managers associated with said predetermined one of said private mobile switching centers, information about said mobile station to the other call managers associated with the other private mobile switching centers connected to in common to said virtual private network via said common public switching telephone network; storing said information of said mobile station in said other call managers to enable a roaming service to said mobile station among said plurality of private mobile switching centers when said mobile station moves to the common cell areas respectively associated with the private mobile switching centers. A system for providing a roaming service among a plurality of private mobile switching centers (30, 50, 70), associated with a corresponding plurality of private mobile communication networks, interconnected to one another via a public switched telephone network (44), comprising: connecting means for connecting the private mobile switching centers to a virtual private network via said public switched telephone network; storing means (96) for storing, at a selected one of said private mobile switching centers, information about a mobile station registered for a private mobile communication service and associated mobile station location information, when said mobile station sends a private mobile communication service registration request to said selected one of said private mobile switching centers via a base station transceiver subsystem (42-N, 62-N, 72-N) shared by the public mobile communication network and a private mobile communication network associated with the selected one of said private mobile switching centers; transmitting means for transmitting the mobile station information and the mobile station location information from said selected one of said private mobile switching centers to the remaining private mobile switching centers via the virtual private network; and providing means for providing the private mobile communication service to said mobile station, by a predetermined one of said private mobile switching centers, using the stored mobile station information and mobile station location information, and the virtual private network, when said mobile station sends a private mobile communication service request to said predetermined one of the private mobile switching centers via one of a plurality of base station transceiver subsystems shared by the public mobile communication network and the private mobile communication networks. The system of claim 3, further comprising: call managers (32, 52, 72) associated with the plurality of private mobile switching centers, registering means for registering said mobile station in one of said call managers associated with a predetermined one of said private mobile switching centers for private mobile communication service, when said mobile station is in the associated common cell area of said predetermined one of said private mobile switching centers, wherein the plurality of private mobile switching centers has an associated common cell area for public and private network communications and each of said private mobile switching centers is connected in common to a virtual private network via the common public switching telephone network, and wherein the providing means are further arranged for providing from said one of said call managers associated with said predetermined one of said private mobile switching centers information about said mobile station to the other call managers associated with the other private mobile switching centers connected to in common to said virtual private network via said common public switching telephone network, and wherein said storing means are further arranged for storing said information of said mobile station in said other call managers to enable a roaming service to said mobile station among said plurality of private mobile switching centers when said mobile station moves to the common cell areas respectively associated with the private mobile switching centers.

Inventors: YANG DOO-YONG, YANG, DOO-YONG
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 2001
Main classification: H04Q7
IPC codes: H04W84, H04W8