Roaming Communication Network

Field of the Invention

The invention relates to a roaming communication network or visited network which is in a roaming relationship with a public land mobile network (PLMN).

Description of the relevant State of the Art

Today's public land mobile networks provide roaming between different networks, i.e. users belonging to a Home PLMN (HPLMN) can roam into a number of roaming or Visited PLMN (VPLMN) in the same or a foreign country and make use of the services and resources provided by the VPLMN. Roaming is a general term in wireless telecommunications that refers to the extending of connectivity service in a location that is different from the home location where the service was registered. Traditional GSM Roaming is defined as the ability for a cellular customer to automatically make and receive voice calls, send and receive data, or access other services, including home data services, when travelling outside the geographical coverage area of the home network, by means of using a visited network. Roaming is technically supported by mobility management, authentication, authorization and billing procedures.

The differentiation between home network and visited network is technically given by the type of subscriber entry in a specific network. If a subscriber has no entry in the home subscriber register of the network (e.g. Home Location Register (HLR) in

GSM networks or local customer database in WLANs (Wireless Local Area

Networks)), the required subscriber data must first be requested by the visited network e.g. from the subscriber's home network in order that the subscriber can be authenticated and any authorization for using the network services can be checked. The "visiting" subscriber acquires an entry in a user database of the visited network (e.g. Visited Location Register (VLR)) and the authorized network

services are enabled. For the roaming procedure in practice, the possibility of assigning the subscriber data is always indispensable in order that authentication, authorization and billing of the subscriber can be performed in the corresponding network.

The technical term "roaming" also encompasses roaming between networks of different network standards, such as e.g. WLAN or GSM. Device equipment and functionality, such as SIM card capability, antenna and network interfaces, and power management, determine the access possibilities.

The known forms of roaming are static from a timing perspective as well static from a location perspective: Once a roaming agreement is established between two operators of a PLMN or another network and the associated technical interconnections are build up, the roaming ability is continuously available. Also the two networks which provide mutual roaming capabilities are bound to specific locations, e.g. countries, where the networks are operated.

Disclosure of the Invention

It is the object of the invention to providing a roaming network which is independent of a static roaming relationship regarding the time and / or the location of roaming.

According to the invention, this object is achieved by providing a method and network as specified in the independent claims.

Other features which are considered to be characteristic for the invention are set forth in the dependent claims.

The roaming communication network according to the invention is characterized in that it is a moving roaming network. The moving roaming network offers roaming services for a limited time and/or a changing location area.

Compared to the known forms of roaming in a PLMN, the proposed "moving roaming network" (MRN) has quite different characteristics: The MRN network which establishes a roaming relationship to another network is itself "on the move". The MRN may establish a roaming relationship only for a limited timeframe and /or at a limited location area and therefore can also be called a visited local network VLN.

The moving roaming networks according to the invention are foreseen to be applied to smaller local area networks, like e.g. vehicular networks, which however understand themselves as independent networks (from a business and technology perspective) and which would like to enter into a roaming relationship with a usual HPLMN, i.e. a standard type of mobile network. This is not at least motivated by the intent to generate revenues from allowing inbound roamers, i.e. subscribers of the HPLMN, to make use of the local resources offered by the MRN, very much like in a standard roaming scenario. However the type of visited MRN providing local resources may be of quite different type as today and may interconnect to the roaming partner by quite different means:

The visited local network may e.g. be a car network, a personal network or an in- house network which from an outside view behave very much like a standard PLMN (GSM / UMTS / NGMN) ₁ although it may internally behave quite different for example like a WLAN based network.

The connectivity between the visited local network and the home PLMN is build up dynamically either e.g. via a wired interface, e.g. a Digital Subscriber Line (DSL), or via an air interface provided by a public PLMN which can either be the HPLMN itself or any other usual roaming partner of the HPLMN. This allows the new type of moving roaming networks to be located anywhere, e.g. inside the region of another VPLMN. The method may as well allow providing subnetworks of a HPLMN as islands in a VPLMN.

There are several advantages in using the proposed moving roaming networks:

- Any type of local network can be treated like a VPLMN as known from GSM/UMTS, although it may internally behave quite differently (e.g. a WLAN based in-house network).

- local moving roaming networks can be operated as "islands" in other networks, which may allow the HPLMN to extent coverage area, if it treats the local network as an own subnetwork.

- Visited local networks do become mobile, while maintaining the ability for roaming.

The method of operation of the invention, together with additional objects and advantages thereof, will be best understood from the following description of a preferred embodiment when read in connection with the accompanying drawing.

Brief Description of the Drawings

Figure 1 schematically shows a moving visited local network with a roaming relationship to a HPLNM.

Figure 2 schematically shows a moving visited local network being located within the coverage area of a HPLNM.

Figure 3 schematically shows a moving visited local network being located within the coverage area of another network, e.g. VPLMN

Figure 4 schematically shows a moving visited local network with a roaming relationship to a HPLNM and roaming session functions in VLN and HPLMN.

Figure 5 schematically shows a moving visited local network with a roaming relationship to a HPLNM and a VPLMN emulation function in the VPN.

Figure 6 schematically shows details of a moving visited local network with a roaming relationship to a HPLNM and a VPLMN emulation function in the VPN.

Detailed Description of Preferred Embodiments of the Invention

In Figure 1 depicts a home public land mobile network (HPLMN) 10 which is for example a GSM or UMTS type cellular network. Remote from the HPLMN 10 is a visited local network (VLN) 12 which is for example a WLAN network or a local GSM type network. The VLN 12 has a roaming agreement with the HPLMN 10 and is connected to the HPLMN via a connection interface 14. The VLN 12 allows subscribers of the HPLMN 10 to use its communication services as defined in the roaming agreement. According to the invention, the VLN 12 is a movable network which can change its location. The VLN 12 acts as a moving roaming network MRN. The roaming connectivity may be of standard type. The GSM / UMTS standard foresees roaming interfaces between the core network HPLMN elements, e.g. mobile switching centre (MSC), Visited Location Register (VLR), Serving GPRS Support Node (SGSN), Gateway GPRS Support Node (GGSN) and Home Location Register (HLR) and the associated protocols. The moving visited local network is connected via the interface 14 to the HPLMN 10. The interface 14 can be an air interface or a wired interface and supports standard roaming protocols, e.g. over the air by an air interface and / or the wired interface, for example over DSL. The VLN 12 emulates and supports the typical functions of the HPLMN, in particular the control and switching functions. Further, gateway function must be realized within the VLN 12 which for example uses internally WLAN or DECT and externally UMTS or NGMN for communicating with the roaming subscribers. The subscriber will not notice any difference whether he is communicating over the VLN 12 or the HPLMN 10.

The VLN 12 includes at least one transceiver unit which acts as the base station or "fixed station" of the VLN and covers the area of the VLN 12 with radio signals with through which the roaming subscribers can communicate. The base station can be a transceiver unit installed on a vehicle which connects to the HPLMN 10 via a wireless interface. Also a personal computer or laptop can function as a base station having a transceiver unit which connects with the HPLMN 10 via a DSL line.

Figure 2 shows a moving visited local network VLN 12 being located within the coverage area of a HPLNM 10. The VLN 12 is connected to the HPLMN 10 via an interface 14 and acts as a local (roaming) provider of telecommunication services which may be different or supplemental to the services offered by the HPLMM 10.

Figure 3 shows a moving visited local network VLN 12 being located within the coverage area of another network, e.g. a Visited PLMN 16. The VPLMN 16 as well as the VLN12 have a roaming agreement with a HPLMN 10 and are connected via interface lines 18 and 14 to the HPLMN 10. The VLN may work like a conventional roaming network or may be a subnetwork of the HPLMN 10 being an "island" in the VPLMN 16.

Figure 4 schematically shows a moving visited local network VLN 12 with a roaming relationship to a HPLNM 10 using roaming session functions 20 in VLN 12 and HPLMN 10. Carrying roaming protocols across GSM / UMTS or DSL-lines requires establishing some form of tunnel protocol and an associated roaming session originating in the VLN 12 and terminating in the HPLMN 10 and vice versa. Dynamically establishing a "roaming session" is performed by a new functional entity called roaming session function (RSF) 20. The roaming session function may be realized as an extension to a GPRS Support Node or an MSC of the HPLMN 10. It allows for the dynamic setup and teardown of roaming sessions. The nature of the tunneling protocol depends on the mutual authentication of networks and used tunnel mechanisms.

Figure 5 shows a moving visited local network VLN 12 with a roaming relationship to a HPLNM 10 and a VPLMN emulation function 22 in the VLN 12. Any type of local network, e.g. GSM, WLAN, DECT, etc., may emulate the behavior of a VPLMN, although it has quite different internal functionality. The emulation of the functionality of a VPLMN is realized by a VPLMN emulation function 22 which maps the internal functionality of the VLN 12 on the protocols used in the HPLMN 10 being a GSM / UMTS network. If the VLN 12 is of type VPLMN by nature this function is empty.

Figure 6 schematically shows details of the network setup depicted in Figure 5. Generally, the connection interface 14 between the VLN 12 and the HPLMN 10 is split up into a logical and a physical connection. In case that the VLN 12 is roaming within a VPLMN 16, the physical connection can be a standard telephone connection, a GRX network, or an Internet link. In case that the VLN 12 is roaming in its own HPLMN 14, the physical connection can be the network internal communication paths. Further this physical connection can be a DSL or Internet connection.

From the side of the logical connection, a roaming connection between the HPLMN 10 and the VLN 12 is set up as if the VLN 12 was a terminal device of the HPLMN 10. Via this logical connection which may use a tunneling procedure, the VLN 12 sets up connection to a subscriber's terminal device 20 which is roaming in the VLN 12. The HPLMN 10 is preferably equipped with a gateway function 28 for setting up a connection to the VLN 12 via a tunneling protocol and further to terminal devices 30 of subscribers roaming in the VLN 12. The gateway function 28 can be realized as an own network node (as shown) or can be integrated in an existing network node, for example a gateway GPRS switching node (GGSN).

The connection between HPLMN 10 and VLN 12 can be considered as a network connection, whereas the connection between the subscriber's terminal device 30 and the VLN 12 can be considered as tunneled standard connection.

When setting up a connection to the HPLMN 10 the VLN 12 behaves like a terminal device from the HPLMN's point of view. For this reason the connection interface 14 must support any standard communication protocols. The gateway function 28 acts as a communication partner for the VLN within the HPLMN 10. The communication connection is afterwards used as a tunnel for the communication between the subscriber's terminal device 30 roaming in the VLN 12 and the HPLMN 10. The tunneling protocol should be a secure tunneling protocol, e.g. virtual personal network (VPN), iPsec tunnel, etc.

The VLN 12 comprises an application logic which is preferably part of the VPLMN emulation function 22. In step 1 , the VLN 12 registers itself via a communication link 14, e.g. a wireless access interface, in the network where it is currently located (this can be HPLMN or VPLMN). If a wireless access network is unavailable, the VLN 12 can register via a wired connection, e.g. DSL. In step 2, the VLN 12 builds up a communication relationship to the gateway function 28 in the HPLMN 10 via an existing network node 24, e.g. GMSC or GGSN. For this the wireless or wired communication link 14 is used. In step 3, the subscriber terminal device 30 registers itself with the VLN 12 via a wireless transceiver station 32 of the VLN 12. The communication connection set up in step 2 is used for retrieving the necessary information to authenticate the subscriber. For authentication, the gateway function 28 forwards an authentication request to a responsible network element of the core network 34 of the HPLMN 10, e.g. a home location register HLR. In step 4, the terminal device 30 can now set up a communication with a desired communication partner, via the VPLMN emulation function 22 and the gateway function 28 to the core network 34 of the HPLMN 10. For this, the communication connection set up in step 2 is used as a tunnel. Gateway and Interworking functions of the VPLMN emulating function 22 are used for adapting signalization protocols and content formats.

The VPLMN emulation function provides 22 all the functions necessary to enable the subscriber's terminal device 30 to communicate with other terminal devices or

services within the VLN 12 or any other network, e.g. the HPLMN 10. These functions include authentication, authorization, switching, switching control and content transport. In a classical GSM type network these functions are provided by mobile switching centers MSC, visited location register VLR, serving GPRS support nodes, gateway GPRS support nodes, and home location register HLR. On the other hand, from the HPLMN's point of view the VPLMN emulation function 22 behaves like a conventional terminal device.

The VPLMN emulation function 22 together with the gateway function 28 are responsible for tunneling the communication from the terminal device 30 roaming in the VLN to the core network 34 of the HPLMN 10.

List of reference numerals

10 Home Public Land Mobile Network (HPLMN) 12 Visited Local Network (VLN)

14 Connection Interface

16 Visited Public Land Mobile Network (VPLMN)

18 Connection Interface

20 Roaming Session Function (RSF) 22 VPLMN Emulation Function (VPLMN EF)