Positioning and location updating of users in a home network of a mobile phone system formed by a multimedia core network

This invention relates to a system and a method for determining and updating the location of users in a home network of a public mobile phone system formed by a multimedia core network by means of a mobility proxy (MPRX) according to the present invention.

Virtual mobile communication operation has developed from mobile communication service operation. At first, service providers operated as retail dealers of mobile network operators (MNO). Their selection of services was initially very limited, but recently it has expanded and nowadays several service providers have their own apparatuses for operating quite independently within a network of a host network operator by productizing and pricing their services and also by producing new, competing services. For operation they may have their own SIM card (subscriber identity module) and their own mobile switching centre (MSC), as well as a home location register (HLR). These service providers are internationally referred to as "enhanced service providers" (ESP). However, they are still service providers, not licensed network operators. They rent connection services and the required network capacity in the form of access rights mainly from a host network operator and their traffic to other networks is directed via a connection interface of the host network operator. ESPs are not far from virtual mobile network operators (MVNO), which use their own mobile switching centre for connecting calls, connect their network to other telecommunication networks and have connection contracts with them. A phone call between subscribers of a mobile network operator and a service provider is operationally and expense-wise the same as between the subscribers of the mobile network operator or between the subscribers of the service provider. A virtual mobile network operator with its own wiring is a separate network operator competing with the host network, whose phone calls are routed in its own mobile switching centre.

The establishment expenses create a certain threshold for starting the operation of a virtual network operator. With the current technology, a virtual mobile network operator must invest in a conventional mobile service switching centre technology, including the different service development and distribution solutions connected to it, conventional intelligent network solutions, etc, because there is no other alternative. This, in turn, has led to the fact that producing individual and distinguishable services is challenging, because each operator uses the same technology. In addition, producing new services is slow and customer-specific customization is very challenging in practice.

By means of the invention it is now possible to lower the threshold of starting a virtual mobile network operation significantly, because it changes the existing multimedia core network to operate as a home network of a public mobile phone system, in which case those service providers that are already producing telecommunication services for their customers by using the multimedia core network can start operating as a virtual mobile network operator and start providing mobile communication services to their customers by utilizing their existing multimedia core network as such. The invention also makes it possible for virtual mobile network operators to develop and produce new customer-specific mobile communication services by utilizing the existing, known application developers. This, in turn, opens different possibilities, for example, for software companies and expert organizations of the Internet community for producing new kinds of mobile communication services, which can be distributed quickly to even a large number of users and the most interesting ones from the point of view of the virtual mobile network operator can be taken into use by the virtual mobile network operator and they may produce corresponding services for their other customers. In addition, when connecting to the above-mentioned multimedia core network a radio network using unlicensed radio frequencies, such as, for example, a wireless local area network in its different forms (for

example different versions of IEEE 802.11) and Bluetooth networks, with a packet-switched mode for circuit-switched services (reference: UMA), the virtual mobile network operator may become a real mobile network operator without it having to acquire a license or build a radio system covering the entire country. UMA (Unlicensed Mobile Access) refers to a manner specified by the UMA consortium for relaying the circuit-switched signalling protocols of a public mobile phone system over a TCP/IP connection by utilizing, for example, any unlicensed radio frequency.

Figure 1 shows the structure of a home network of a host network operator and a virtual mobile network operator in the present situation;

Figure 2 shows a system according to the invention which changes the multimedia core network to operate as a home core network of a virtual mobile network operator;

The home networks (100) and (101) of the host network operator and the virtual mobile network operator according to figure 1 comprise a home location register (1), which in turn comprises an authentication centre (AuC), an equipment identity register (EIR) (2), a service control point (SCP) (3), a short message/multimedia messaging centre (SMSC/MMSC) (4), a mobile switching centre/visitor location register (MSC/VLR) (5), and a gateway mobile switching centre (GMSC) (6). As mentioned before, a virtual mobile network operator has its own interconnection gateway to external networks (102). For the part of uplink traffic, the traffic through the interconnection gateway travels from the mobile phone (7) of a subscriber of a virtual mobile network operator via a base station of a host network operator (NodeB/BTS) (8) and a base station controller (RNC/BSC) (9) to the mobile switching centre (5) of the host network company. On the basis of the visitor location register data of the MSC/VLR (5) the phone call is directed to the mobile switching centre (10) of the virtual mobile network operator. On the basis of

the data of the home location register (1) of the virtual mobile network operator the phone call is forwarded to the right destination. For the part of downlink traffic, the phone calls to the network of the virtual mobile network operator are directed via its own interconnection gateways. The phone call is directed to a mobile switching centre (10), and on the basis of data provided by the connected home location register (1) the phone call is forwarded via a radio path of a host network operator to a subscriber (7) of the virtual mobile network operator. An internal phone call within the virtual mobile network operator travels from a subscriber (7) of the virtual mobile network operator via a base station (8) of the host network company, a base station controller (9) and a mobile switching centre (5) to the mobile switching centre (10) of the virtual mobile network controller and from there via the network of the host network operator back to a second subscriber of the virtual mobile network operator.

The home network (101) of a virtual mobile network operator according to figure 2 comprises a home location register (1), an equipment identity register (2), a user agent server (UAS) (10), a mobility proxy (11), a media gateway controller (MGC) (12), a signalling gateway (SGW) (13) and a media gateway (MGW) (14). A user agent server (10) now produces the mobile services of a conventional mobile phone system based on multimedia services of a user agent server (10), the most central of which is an IP telephone service, which implements, and possibly in the future also replaces, conventional circuit-switched telephone services (i.e. teleservices) as well as supplementary services connected to them (i.e. call transfer, call holding/call pickup, etc.) in public mobile phone networks as well. The IP telephone service can, in turn be a generic IP telephone service according to IETF (Internet Engineering Task Force) specifications or a proprietary IP telephone service, such as Skype. It can also be a multimedia service of an IP Multimedia Subsystem (IMS) specified by 3GPP (the 3 ^rd Generation Partnership Project). The wireless access network is formed of a generic

radio network utilizing unlicensed frequencies and comprised of wireless access points (15).

The more specific structure and operation of the home network of figure 2 utilizing the invention is described with terms, interfaces and protocols known from 3GPP and IETF recommendations.

The interfaces of the home network according to figure 2 and the mobility proxy comprised by it are described more in detail hereinbelow.

The interface (50) is a signalling interface between mobile switching centres and utilizing BICC or ISUP protocol, where the lower level protocols are MTP protocols or Sigtran protocols, such as SCTP/IP or M3UA/IP. Via the interface (51), media is transferred between the base station controller (9) of the host network operator and the media gateway (14) of the virtual mobile network operator by using a conventional pulse code modulation method (PCM). The interface (52) is an interface according to SIP session procedure. The interface (53) is an MAP interface, where the lower level protocols are MTP protocols or Sigtran protocols, such as SCTP/IP or M3UA/IP. The interface (54) is an Up interface according to UMA specifications.

The mobility proxy (11) according to the invention of figure 2 comprises the following functions. An UNC GW function (20) comprises an UMA radio resource protocol gateway, via which the terminal (6) equipped with UMA properties registers and communicates with the mobility proxy (11) and through that with the home network (101). The mobility proxy (11) does not implement the actual UMA network controller, but only the UMA radio resource protocol gateway. A VLR function (22) comprises the visitor location register extended with controlling the address-of-record of the IP telephone service and address binding connected to sessions. An SIP Proxy function (23) comprises a SIP proxy server extended with the registration function of a user agent client (UAC). A SGW function (21) is the core of the protocol

routing operation of the mobility proxy (11), which receives and relays the location updating, registering, identification, connection, disconnection requests and responses coming from and going to different interfaces.

The operation of the system according to figure 2 utilizing the invention in connection with registering to the home network is described more in detail hereinbelow. The description of the function is based on the functions according to the 3GPP and IETF specifications.

When the SGW function (21) shown in figure 2 receives a location updating request from the terminal (16) relayed by the UNC GW function (20) via the interface (54), it relays the request further to the VLR function (22). The VLR function (22) signals the location updating via the interface (53) with the previous MSC/VLR (i.e. the MSC/VLR (5) or some other MSC/VLR that is not shown in figure 2) and the home location register of the subscriber in question (i.e. the home location register (1) or the home location register of some other home network, which is not shown in figure 2; for the purpose of example let us assume that the home core network of the subscriber in question is the home network (101)). In connection with location updating the user and terminal identifications are performed, which the VLR function (22) signals via the SGW (21) and UNC GW (20) functions between the terminal (16) and the home (1) and equipment identity register (2) of the subscriber. In connection with location updating, the home location register (1) relays to the VLR function (22) the subscriber data of the user related the circuit-switched services etc. of the public mobile phone system, which the VLR function (22) saves in its database (or a corresponding memory). When the home location register (1) has accepted the location updating and the VLR function (22) has relayed the acceptance to the SGW function (21), the SGW function (21 ) activates the SIP Proxy function (23) to perform the registration according to the SIP session procedure to the user agent server (10) via the interface (52). The SIP Proxy function (23) sets the home network registrar's domain name to the Request URI (Uniform Resource Identifier) of the SIP

registration request, which domain name the SIP Proxy function (23) derives from the country and network codes of the user's International Mobile Subscriber Identity (IMSI) according to the 3GPP specifications. In the To header field of the SIP registration request the SIP Proxy function (23) sets the registration address, which is the public user identity of the registering user presented in the form of a uniform resource locator (URL) meant for a phone number, which in this case is the international mobile phone number (mobile station ISDN, MSISDN) of the above-mentioned registering user. In the From header field of the SIP registration request the SIP Proxy function (23) sets the address connection connected to the SIP session services of the user's SIP end point, which address connection follows the resource identifier structure according to the SIP session procedure, including the user's international mobile phone number as a character string + '@' character + domain name of the mobility proxy (11) or its numeric IP address. In the Contact header field of the SIP registration request the SIP Proxy function (23) relays to the user agent server (10) the address connection connected to the SIP session services of the user's SIP end point, which address connection the SIP Proxy function (23) also relays to the VLR function (22) to be stored in a database (or a corresponding memory). The above-mentioned address connection of the session services of the SIP end point now specifies the location of the terminal (16) in the home network (101) and is the same as the address connection relayed in the From header field, i.e. the user's international mobile phone number as a character string + '@' character + domain name of the mobility proxy (11) or its numeric IP address. The address connection in question specified by the location may also be formed of the user's international mobile phone number as a character string + domain name of the media gateway controller (12) or its numeric IP address. After a successful SIP registration the SIP Proxy function (23) relays the subscriber data stored by the VLR function (22) to the directory service of the user agent server (10) or the like. This can be implemented by using, for example, the LDAP protocol (Lightweight Directory Access Protocol) specified by IETF. In this case it is necessary to specifically

know the schema of the directory service of the user agent server (10), because even if the access protocol of the directory or the like is standardized, its schema is not. Another way to implement the relay of subscriber data is to use, for example, an application programming interface (API) of the directory service of the user agent server (10) for adding, changing and removing subscriber data. When the subscriber data has been relayed to the user agent server (10), the SIP Proxy function (23) sends a location updating response indicating acceptance to the SGW function (21), which relays it to the terminal (16) via the UNC GW function (20). If the SIP registration fails for some reason, the SIP Proxy (23) activates the cancellation of location updating to the home location register (1). The cancellation of location updating is performed by the VLR function (22) and the SGW function (22) signals it between the terminal (16) and the VLR function (19) via the UNC GW function (20). The home location register (1) can also reject the original location updating request, which rejection is signalled by the SGW function (22) to the terminal (16) via the UNC GW function (20) after receiving it from the VLR function (22).

In the following, the functions connected to phone call establishing/cancellation are described more in detail.

When the SIP Proxy function (23) of the mobility proxy (11) receives a SIP connection session request from the media gateway controller (12) via the interface (52), the SIP Proxy function (23) requests the VLR function (22) to search the routing information from the home location register of the sought subscriber (i.e. the home location register (1) or the home location register of some other home network, which is not shown in figure 2) via the interface (53). The VLR function (22) derives the home location register address of the sought subscriber from the phone number of the sought user, which the SIP Proxy function (23) picks up from the To header field of the received SIP session request and relays to the VLR function (22). The To header field of the received SIP session request includes the phone number of the sought

user (i.e. public identity) shown in the form of a resource locator meant for telephone numbers. The home location register of the sought subscriber sends as a routing address the number of that mobile switching centre, via which the connection to the sought subscriber is formed (i.e. the number of that mobile switching centre whose visitor location register area the sought subscriber at that moment is located). After receiving the routing address the VLR function (22) relays the routing address and the international identity of the subscriber to the SIP Proxy function (23), which performs the (re) registration of a third party of the sought subscriber by sending a SIP registration request to the registrar of the home network of the sought subscriber via the interface (52) if the above-mentioned routing address differs from the mobile switching centre number corresponding to the mobile proxy (11) in question. To the request URI of the SIP registration request the SIP Proxy function (23) sets the domain name of the home network registrar of the sought subscriber, which the SIP Proxy function (23) derives from the country and network codes of the sought subscriber's international identity according to 3GPP specifications. In the To header field of the SIP registration request the SIP Proxy function (23) sets a registration address, which is the sought subscriber's telephone number (i.e. public identity) shown in the form of a resource locator meant for telephone numbers. In the From header field of the SIP registration request the SIP Proxy function (23) sets the address connection connected to the SIP session procedure of the seeking SIP end point, which address connection follows the resource identifier structure according to the SIP session procedure, including the seeking subscriber's international mobile phone number as a character string + '©' character + domain name of the mobility proxy (11) or its numeric IP address. In the Contact header field of the SIP registration request the SIP Proxy function (23) relays to the registrar of the sought subscriber's home network the address connection connected to the SIP session services of the SIP end point of the sought subscriber, which address connection defines the location of the SIP end point of the sought subscriber and which is the phone number of the sought user as a character string + ' ^@ ' character +

domain name of that mobility proxy of media gateway controller that is associated to the mobile switching centre received in the routing data query (i.e. the mobility proxy or media gateway controller, via which the mobile switching centre in question can be accessed). The domain name of the mobility proxy or the media gateway controller in question can be derived from the country and network codes of the mobile switching centre number in question according to the 3GPP specifications, or it can be received from the network configuration data. When the SIP Proxy function (23) of the mobility proxy (11 ) receives an OK response to the SIP registration request it has sent, the (re) registration to the home network of the sought subscriber has succeeded. If the Contact header field of the received OK response now also has some other address connection, which follows the resource identity structure according to the SIP session procedure including the user's phone number as a character string + '©' character + some domain name or a numeric IP address, i.e. the previous registration to the home network of the sought subscriber via some other mobility proxy, that other address connection is removed by sending a registration request to the home network registrar of the sought subscriber, the expiration time of which request is 0 seconds and the Contact header field now has that other address connection. When registration to the home network of the sought subscriber has succeeded, the SIP Proxy function (23) (re)registers the phone number of the seeking subscriber as an address connection to the mobility proxy (11) or as an address connection pointing to the media gateway controller (12), which follows the resource identity structure according to SIP session procedure, including the phone number of the sought subscriber as a character string + '@' character + domain name of the mobility proxy (11) or the media gateway controller (12) or its numeric IP address. The registration is performed to the home network registrar of the seeking subscriber, whose address the SIP Proxy (23) derives from the phone number of the seeking subscriber in the From header field of the received SIP session request or from the country and network codes of the internationally identity of the seeking subscriber picked up from the database of the VLR function (22) (or

a corresponding memory) according to 3GPP specifications. When the SIP Proxy function (23) of the mobility proxy (11) receives an OK response to the registration, the (re)registration to the home network of the seeking subscriber has succeeded. If the Contact header field of the received OK response now again has some other address connection, which follows the resource identity structure according to the SIP session procedure including the seeking user's phone number as a character string + '©' character + some domain name or a numeric IP address, i.e. the previous registration to the home network of the seeking subscriber via some other mobility proxy, that other address connection is removed by sending a registration request to the home network registrar of the seeking subscriber, the expiration time of which request is 0 seconds and whose Contact header field now has that other address connection. When the registration also to the home network of the seeking subscriber has succeeded, the SIP Proxy function (23) relays a SIP session request to the user agent server (10), after which the SIP session is formed between the terminal (16) and the multimedia core network via the mobility proxy (11). The SIP session is cancelled in a corresponding manner via the mobility proxy (11).