Telecommunication system and method for controlling switching of a user terminal between two networks

The invention relates to a telecommunications system that includes a first network and a second network and a method for controlling the passage of a subscriber terminal between a first network and a second network.

[0002] In present times, the spread of third generation telephony networks is increasingly increasing, i.e. compliant with the Universal Mobile Telecommunications System, UMTS. At the same time, other radio networks are being developed that aim to provide subscribers with large bandwidths to enable large amounts of data to be transferred in a shorter period of time. Such a radio network has been planned for some time by many interested parties who have joined the so-called WiMAX, Forum Worldwide Interoperability for Microwave Access (<a href="http://www.wimaxforum.org">www.wimaxforum.org</a>) to develop a standard for the WiMAX radio network. It is planned that terminals of subscribers, such as mobile phones or portable computers, should have access to both existing mobile networks, such as the UMTS network, as well as to the WiMAX radio network. In this way, subscribers can choose the network that suits them most according to certain criteria, such as availability, price, quality etc. and, if necessary, switch between two different networks.

[0003] During the transition between two networks, data may be lost and / or the connection may be lost, which should be avoided. To this end, this type of transition between two different networks is implemented using the mobility protocol. The purpose of the mobility protocol is to keep existing connections while changing the network

- 3 communicating subscribers and avoiding or at least minimizing interruptions.

[0004] Such a mobility protocol has been presented for the Internet Engineering Task Force, IETF, for example, by the WiMAX Forum primarily based on the so-called Mobile IP protocols, in particular the Mobile IP version 4, MIPv4 protocol. WiMAX forum defined two different variants of using Mobile IP. In the first one, a so-called Client Mobile IP, CMIP is defined, i.e. a client which is installed directly in the subscriber's terminal and which realizes the signaling of the transition between two networks by the subscriber's terminal. The second one defines the so-called Proxy Mobile IP, PMIP, which is the client that is installed on the network and is the substitute for the subscriber's terminal in the network regarding the transition between networks. PMIP implements signaling of the transition between networks for the subscriber's terminal. In this case,

[⁰⁰⁰5] ^{In you}m ^ 06 ^ 0 ^ ^dokument ^IN0 200⁴/ 006⁴⁴7 o^pithe telecommunications system with a cellular network and a wireless LAN, W-LAN. The mobile terminal of the subscriber should be able to pass smoothly between both networks. The telecommunications system includes an AAA-Client that works for both mobile networks as well as for wireless LAN. The authentication is obtained using the DIAMETER protocol by AAA-Client (AAAh, AAAf).

[0006] The present invention aims to provide a largely seamless transition between the cellular telephone network and the so-called WiMAX radio network. [0007] According to the invention, this object is achieved by means of a telecommunications system with the features of claim 1 and according to a method for controlling a transition.

A subscriber between the mobile telephone network and the WiMAX radio network, having the features set forth in claim 10.

[0008] With regard to the equipment, the telecommunications system of the invention comprises a first network that is a mobile telephone network, a second network that is a so-called WiMAX radio network, Worldwide Interoperability for Microwave Access and a so-called AAA server, Authentication, Authorization and Accounting, used to store subscriber's subscriber's data.

[0009] The subscriber's terminal is intended both to use the first network as well as the second network. The hAA server is so located in the ttlehkmunicational system that both the first network and the other side of the network have access to the subscriber data of the subscriber's terminal stored in the AAA server.

[0010] According to a method, the passage of a subscriber terminal is controlled between a first network that is a mobile telephone network and a second network that is a so-called WiMAX radio network, Worldwide Interoperability for Microwave Access. In addition, the subscriber's subscriber data, which may have access to both the first network as well as to the other network, are stored in the so-called AAA server, Authentication, Authorization and Accounting. The subscriber's subscriber data stored in the AAA server is available from both the first network and the second network.

[0011] On the basis of the present invention, a smooth transition between the cellular network and the WiMAX radio network can be advantageously made such that the interruption of the existing connection can be completely or almost completely prevented. This guarantees particularly high

-5efficiency and high quality when changing the network. In addition, AAA infrastructure, which is common to both networks, can be easily used to complete the transition. The AAA server, defined with respect to WiMAX, can preferably be modified according to the invention in such a way that it allows access from both networks.

[0012] According to a preferred further development of the invention, the telecommunications system is modified so that when establishing a connection between the subscriber terminal and the first network or the second network, a check is made to ensure that the subscriber's terminal is already connected to another network. If this is the case, the subscriber's subscriber's data is read from the AAA server. In a technically simple way, you can use the subscriber data already existing in the AAA server to establish a connection to one of the two networks as a result of connecting to the other network. This simplifies signaling in the event of a transition between both networks. In addition, it is ensured that the subscriber data that is needed to set up the new connection is at least partly the same as it was used to compose an existing connection. This leads to a seamless network change.

[0013] It is particularly advantageous to modify the telecommunications system that the subscriber data obtained at the connection setup is stored in the AAA server if the subscriber's terminal is no longer connected to the second network. In this case, the subscriber data stored in the AAA server when compiling a new connection can be used in the event of a later transition to another network. For this purpose, you can reach the subscriber data already stored in the AAA server at the transition to obtain a transition without interrupting the connection.

[0014] In another particularly preferred embodiment of the invention, a mobility protocol is implemented to pass the subscriber terminal between the first network and the second network. The said mobility protocol enables a safe transition and ensures that the participating transition signals of the telecommunications system components can complete the transition. The mobility protocol is a particular so-called Mobile IP mobility protocol. The subscriber's terminal can also keep its IP address when switching to another network.

[0015] It is particularly advantageous to define, in a mobility protocol, a Mobil-Client customer for a subscriber's terminal that realizes by means of a subscriber's terminal signaling during a subscriber terminal passage between networks. In this way, a suitably equipped subscriber terminal can itself provide signaling. This simplifies signaling and keeps expenses low. The Mobil-Client is in particular the so-called Client Mobile IP, CMIP, client of the mobility protocol^Mabout^bile ^IP.

[0016] According to a preferred further development of the invention, in the mobility protocol there is defined a MobilClient Proxy which acts as a substitute for the subscriber's terminal to perform signaling when performing the subscriber terminal transition between the networks. In this way it is also possible in the case of a subscriber terminal in which the appropriate seamless network change is not installed.

especially the so-called Proxy Mobile IP, PMIP, the customer of the Mobile IP mobility protocol.

[0017] Preferably, such a Proxy Mobil-Client is implemented in the first network. In this way, the cellular telephone network is intended to be signaled for

Mobil-Client, get

The Proxy Mobil-Client is in

-7 assist the deputy for the subscriber's terminal based on the mobility protocol. In a particularly simple way, it is possible to make a transition in a mobile network, preferably to access the AAA server and also send data about the cellular network to it.

According to another advantageous further development of the invention, a so-called home agent, HA, is defined in the mobility protocol, for the home network assigned to the subscriber's terminal and so-called foreign agent FA for the foreign network used by the subscriber terminal, which is not its home network. The foreign agent, FA, is made in such a way that it receives the subscriber's data from the home network, directed to the subscriber's terminal and usage data. The home agent, HA, may in particular be a computer or router that is installed in the home network of the subscriber's terminal. The home agent sends to the subscriber's terminal, primarily in the home network, data packets, which are intended for the subscriber's terminal, if the subscriber's terminal is not in the home network. The home agent also manages the location information of the subscriber's terminal. A foreign agent, FA, can also be a special computer or router that is installed on a foreign network that is not the home network of the subscriber's terminal. Aggerrt foreign makes the routing service to a foreign network available to the subscriber's terminal in the area of ​​the external network. In particular, the foreign agent sends to the subscriber's terminal data packets obtained from the home agent of the subscriber's terminal. The terms parent network and foreign network are used here in the sense of the appropriate terminology referring to the mobility protocol. Aggerrt foreign makes the routing service to a foreign network available to the subscriber's terminal in the area of ​​the external network. In particular, the foreign agent sends to the subscriber's terminal data packets obtained from the home agent of the subscriber's terminal. The terms parent network and foreign network are used here in the sense of the appropriate terminology referring to the mobility protocol. Aggerrt foreign makes the routing service to a foreign network available to the subscriber's terminal in the area of ​​the external network. In particular, the foreign agent sends to the subscriber's terminal data packets obtained from the home agent of the subscriber's terminal. The terms parent network and foreign network are used here in the sense of the appropriate terminology referring to the mobility protocol.

[0019] It is particularly advantageous to have a foreign agent FA in the first network, which is so equipped that it can transmit mobility-specific signaling data between the Mobil-Client Proxy and the home agent, while the actual user data of the subscriber is transmitted between the subscriber's terminal and the home agent. In this technically simple way, it is possible to obtain effective data transfer from and to the subscriber's terminal.

According to another preferred further development of the invention, the subscriber data stored in the AAA server includes at least one, in particular all of the following information: - information that is used by the so-called Mobile Security Association, MSA, to protect the transmission protocol-specific mobility of signaling data between the subscriber's terminal and the parent agent, such as a common secret to generate the so-called Message Authentication Codes, MAC, algorithm information for generating Message Authentication Codes, MACs, playback protection, etc. - address the home agent of the subscriber's terminal and - the home address of the subscriber's terminal in its home network. With one or more, in particular all information, You can effectively ensure a smooth transition between both networks. [0021] It is particularly advantageous if the telecommunications system is arranged such that when the subscriber terminal passes between the first network and the second network, it maintains the subscriber's existing connection to one of the two networks prior to the transition, in particular for a certain duration of time after which it is executed. new connection of the subscriber's terminal with another of the two networks. In this way, it can be advantageously ensured that the newly formed ones after which a new connection of the subscriber's terminal with another of the two networks is made. In this way, it can be advantageously ensured that the newly formed ones after which a new connection of the subscriber's terminal with another of the two networks is made. In this way, it can be advantageously ensured that the newly formed ones

- connection is secure and works before the "old" connection that existed before the new connection was established, will be interrupted if necessary. On demand, you can easily retrieve the "old" connection and thus be able to return.

[0022] According to a preferred further development of the invention, the first network complies with the so-called Universal Mobile Telecommunications System, UMTS. The combination of UMTS network and WiMAX network provides the subscriber with particularly large freedom of movement and convenience.

[0023] Other preferred embodiments and further developments of the invention are described below with reference to the drawings.

The invention will now be explained in more detail with reference to an embodiment schematically illustrated in the drawings, in which:

Figure 1 shows a first embodiment of a telecommunications system according to the invention with a UMTS network and a WiMAX network that includes a Proxy Mobile IP client of a mobility protocol;

Figure 2 is a first flow chart in which a time signaling diagram is shown for establishing a subscriber terminal connection in a UMTS network of a telecommunications system according to Figure 1;

Figure 3 is a second flow chart illustrating a time signaling scheme for establishing a subscriber terminal connection in a WiMAX network of the telecommunications system of Figure 1;

Figure 4 shows a second embodiment of a telecommunications system according to the invention with a UMTS network and a WiMAX network, wherein the subscriber terminal includes a Client Mobile IP client of the mobility protocol, and

Figure 5 is a third flow chart in which a time signaling diagram is shown for establishing a subscriber terminal connection in a UMTS network of a telecommunications system according to Fig. 4;

In the drawings of the drawing, the same or similar elements and signals - unless otherwise indicated - are designated by the same referring symbols.

Fig. 1 shows a first embodiment of the telecommunications system 1 according to the invention with a first network, which here is a UMTS network 2 and a secondary network, which is a WiMAX 3 network. The UMTS 2 network includes a so-called UMTS^{TS T}errestrial Radio Access ^ worE U^TRAN, 4, which serves as the UMTS 2 network access network. The UMTS 2 network also includes the so-called Serving GPRS Support Node, SGSN, 5, which is the master control unit of the UMTS network 2 and is connected to special network nodes, the so-called Gateway ^GPRS Eiupport Node, 'Gtóoi-b 6. ^sie^{WiMAX 3} has more than one structure defined by the WiMAX Forum. The WiMAX 3 network includes the so-called Access Service Network, ASN, 7, and also the so-called Connectivity Service Network, CSN. The WiNX 3 network CSN is in the illustrated embodiment, in order to simplify the illustration, connected to the so-called network^Pat^blic Lan^{d M}about^bile tótóorE ^ PLIkl, stóci. UMTtó 2, create^andc common PLMN / CSN network 8. PLMN and CSN can also be separate networks. In particular, it is possible to

In the implementation example, the UMTS 2 network, as well as the WiMAX 3 network, shared a common operator.

[0027] The telecommunications system 1 further comprises a mobile station 9 which is a subscriber terminal and in this case is a mobile telephone. The mobile station 9 has both access to the UMTS 2 network as well as to the WiMAX 3 network and can connect alternately with both networks. To show this, the mobile station 9 is shown in Fig. 1 twice. In one position it is connected to the UTRAN 4 of the UMTS 2 network, and in the second position it is connected to the base station BS 10, located in the ASN 7 of the WiMAX network 3. In order to pass between the two networks, in the telecommunications system 1 a mobility protocol is implemented, which supports the transition from one network to another. The mobility protocol is the so-called Mobile IP protocol, MIP. MIP defines the home agent, HA, to which the mobile station 9 is assigned. Herein the HA 11 home agent is the 8. MIP network further defines a foreign FA agent. In this case, the first foreign agent FA 12 is located in the GGSN 6 UMTS 2 network. The second foreign agent^{FA 13} thi^t present in ^Gateway ^{ASN-GW 14} in ^{ASN 7} in sbci. ^INiMAX

3. The HA 11 home agent is connected to both the FA 12 foreign agent as well as the foreign agent FA 13. The foreign agent FA 12 is further connected to the SGSN 5 and the foreign agent FA 13 is connected to the base station 10.

[0028] In the use of the mobility protocol defined by the WiMAX Forum, a MobilClient Proxy is also defined to perform signaling during the transition of the mobile station between both networks 2 and 3. The Mobil-Client proxy is here a Proxy Mobile IP client, PMIP protocol mobility. PMIP serves as a substitute for mobile station 9 so that the protocol

-12mobility does not have to be located here. The first PMIP client 15 is present in the UMTS network 2. In the embodiment shown, the PMIP client 15 is located in the GGSN 6. However, this is not necessary. The PMIP client may also be located outside the GGSN 6 in the UMTS 2 network. In Fig. 1 the PIMP client 15 is connected to the external agent FA 12. Dru^{gi kli}en^{t PMIP 16} thi^t about^becn^yand suci. ^wiMAX 3 in A3^N 7. The PMIP client 16 is connected in Fig. 1 to the foreign agent FA 13. The parent agent HA 11 also serves as a transition to other areas of the telecommunications system 1. For example, in Fig. 1 is shown the so-called Correspondent Node CN 17, which e.g. be a web server on the Internet. [0029]^INe ws^halfhere ^PLMN/^CSN 8 is^t us^ytuowan^ytand^k called AAA 18 server, Authentication, Authorization and Accounting. The AAA 18 server primarily supports authentication, authorization and billing for WiMAX 3 networks, as well as charging for data transmission or communication messages. In order to communicate with the AAA server¹⁸ UM^TS 2, in ^GGSN 6, present is^{t kli}en^t AAA ¹⁹ behind^ś in ^{WiMAX 3}in ^{ASN-GW 14} present is^tAAA proxy 20. The AAA server 18 is here connected to both the UMTS 2 network, the AAA 19 client, as well as the WiMAX 3 network, and the AAA 20 proxy. According to the invention, one can access the AAA 18 server both from the UMTS 2 network, and also from the WiMAX 3 network. Correspondingly, the AAA 18 server can send data to both networks 2 and 3.

[0030] In the AAA server 18, it is possible to remember and use primarily data that is assigned to the mobile station 9 and needed for the transition^tACJ^and can^bilfootball ⁹ about^d make a POI^{TS 2 d}about ^wiMAK ³. ^lat^bconversely, that the required MIP operations and signaling can be performed. The information needed to compile the "new" connection also corresponds to the information.

- obtained for the "old" connection to this network, to which the connection is already established. From the point of view of the home agent HA 11, there is a simple change of the so-called care-of address, CoA behind the transition to another network. Said CoA corresponds to the address of the mobile station 9 in the foreign network, i.e. the address at which the mobile station 9 is reachable, when it is in a foreign network. Such CoA change can be made during signaling by so-called Registration Request. The information stored in the AAA 18 server for mobile station 9, which can be accessed when switching to networks 2 or 3, is as follows: - information, MSA data that is needed for the so-called Mobile Security Association, MSA, to protect the transmission signaling data, specific to the mobility protocol, between the mobile station 9 and the home agent 11, such as a common secret to generate the so-called Message Authentication Codes, MAC, MAC generation information, playback protection, etc., - HA address of the home agent 11 of the mobile station 9 and - address the mother HoA of the mobile station 9 in its home network 8 (in the WiMAX standard, said home address is referred to as Point of Attachment, PoA). This information is obtained at the first connection of the mobile station 9 to one of the two networks 2 or 3 and are stored in a special area of ​​the AAA server 18. If the network 2 or 3 is changed, the information can be retrieved and called. The information is then sent to the PMIP client of the "new" 2 or 3 network so that it can perform the necessary MIP operations and signaling to perform the transition. In the event of a change, MSA, HA @ and HoA data remain the same and only CoA is changed. [0031] Fig. 2 shows a first flow chart in which a time signaling exchange diagram is shown when setting up a mobile station connection 9

And UMTS network 2 of the telecommunications system 1 according to FIG.

1. In the beginning, the mobile station 9 authenticates itself via SGSN 5 and the so-called Home Location Register, HLR, by means of the so-called Authentication and Key Agreement, AKA, in ^dabout^youchczasowej ^proce^dUrze ^{GPRS /}UM^TS P^S. ^{SGSN 5} uz^ss^kand then the subscriber profile of the mobile station 9 from HLR. The access to the UMTS network 2 by SGSN 5 is not relevant here and will not be described in more detail and is not shown in Fig. 2. The following description of the so-called Packet Data Protocol, PDP, procedure for creating The context based on Fig. 2 relates both to the case where the mobile station 9 establishes a "new" connection to the UMTS network 2, without prior connection to the WiMAX network 3, as well as to the case where the mobile station 9 establishes a "new" connection. with the UMTS 2 network, while it is already connected to the WiMAX 3 network.

[0032] In Fig. 2 are shown various components of the telecommunications system 1 involved in the signaling. In the first step 21, the mobile station 9 sends the so-called Context Activation Request PDP by SGSN 5 to GGSN 6. In the GGSN 6, an access point, the so-called Access Point Name, APN, which supports roaming between the WiMAX 3 network and the network is preferably selected. UMTS 2. Such an APN must make the PMIP functionality available and it must be possible for it to achieve both the HA 11 home agent by means of MIP signaling, for data transport as well as the AAA 18 server, by the AAA infrastructure. Alternatively, it is also possible that in the subscriber profile assigned to the mobile station 9, it is found that the mobile station 9 can only select specific APNs with PMIP functionality,

[0033] When the GGSN 6 receives the Context Activation Request PDP, it sends in step 22 the so-called AAA Request to the AAA 18 server. This is done by the AAA client 19, which is located in the GGSN 6. The AAA Request may include the so-called Network Access Identifier, NAI, which in particular can be sent from a mobile station 9 with a password, in order to provide additional security measures for access to APN services. The AAA Request may further include the so-called International Mobile Subscriber Identity, IMSI, as the identification of the mobile station 9 in the UMTS 2 network and / or the canonical NAI which identifies the subscriber data in the AAA server.

18. Such NAI is in particular described in specification 3^{GPP TS 29}.0⁶¹: "3r^{d G}eneration ^Partners^hand^{p P}Rojec^t; Technical Specification Group Core Network and Terminals; Interworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Data Networks (PDN); Release 6 "; Section 16. Obtaining the canonical NAI from IMSI is described in particular in 3GPP TS 23.003: "3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Numbering, addressing and identification; Release 6 ". More information can therefore be obtained in the mentioned specifications. Based on the information sent in step 22, the AAA server 18 must be able to access the relevant subscriber data stored therein.

[0034] In the following eeap 22, ssrwwr AAA, 11 transmits GGSN 6 using so-called AAA Reply and sends the following parameters and information: - the IP address that serves as the home address HoA of the mobile station 9 in the MIP (this address is referred to as PoA according to the WiMAX standard), - HA @ home agent's HA 11 address and - other data that is needed to secure with MSA

- communication between the PMIP client 15, which here for the purpose of signaling, takes over the role of the mobile station 9 and the home agent HA 11. Optionally, the address of the original ASN-GW 14 can be additionally sent. In the case when such ASN-GW 14 address will be sent and received by GGSN 6, GGSN 6 can optionally create a so-called R4 tunnel to ASNGW 14. The information described here, provided there was an "old" connection to the WiMAX 3 network, are already, due to the said "old" connection, stored in AAA server

18. If the said "old" connection does not exist, said information is first obtained again and then remembered in the AAA server 18.

[0035] ^IN ff^ęe. e^tand^pie 2^{4 GGSN 6} releases Uient ^PMIP15 using so-called Start_PMIP commands. In this way, the registration of MIP and specific to MIP begins, in particular obtained from the AAA 18 server, the information is^pslaughter ^{GGSN 6 p}lashes^veinane ^dabout the customer ^{PMIP 15}. KMen^{t PMIP 15}he can then confirm receipt of this information in step 25 by means of the Start_PMIP_ACK message sent to the GGSN

6.

[⁰⁰³6] ^{In k}about^lEJN^sme^tand^pie ^{26 kli}en^{t PMIP 15} in^ss^veinand ^tand^kreferred to as the MIP Registration Request to the home agent 11. The foreign agent's address 12 is used as the CoA and HoA address of the mobile station 9, which are provided by GGSN

6. It is advantageously possible to preserve the "old" MIP relationship between the home agent 11 and the foreign agent 13 of the WiMAX network. This can be obtained by means of a corresponding flag in the client signaling of the PMIP 15, which is set for this purpose. In this case, the home agent sends data packets to both foreign agents, the &amp; quot; new &amp; quot; foreign agent 12 and the &amp; quot; old &amp; quot; foreign agent 13. In this way, an even smoother transition between both networks 2 and 3 can be ensured without interrupting the connection to the mobile station

-179. Such a parallel connection to both networks 2 and 3 can be maintained in particular for a predetermined duration which can be appropriately selected until it is ensured that the "new" connection to the UMTS network 2 is secure and performs its functions stably. mobile station 9 interrupts connection to WiMAX 3 network, WiMAX 3 PMIP network client 16 unregisters its connections, as a consequence of which the MIP transmission tunnel is deleted, Alternatively, PMIP client 16 can delete the MIP transmission tunnel when it receives a message saying that mobile station 9 uses the UMTS 2 network without interrupting the connection to the WiMAX 3 network. In this case, the PMIP client 16 can easily re-create the MIP transmission tunnel if the PMIP 16 client receives a message,

[0037] If the mobile station 9 was not previously connected to the WiMAX 3 network, the home agent 11 contacts in the next step 27 with the AAA server 18, to obtain the MSA data and the HoA address. With the help of this information, an MSA can then be created between the PMIP client 15 and the home agent HA 11. In the next step 28, the data from the AAA server 18 is sent to the home agent HA 11. In this embodiment, the home agent HA 11 requests the data from the AAA server 18. It is also possible that the AAA server 18 sends the necessary information to the home agent 11 after step 22. Steps 27 and 28 are not necessary here as long as the mobile station 9 was previously connected to the WiMAX 3 network. In this case, the agent HA 11 mother knows this information already.

[0038] In step 29, the HA home agent 11 sends to the PMIP client 15 a so-called MIP Reg_Reply message. Said transmission via a foreign agent 12.

Next, the PMIP client 15 responds in step 30 with the message Reg_Complete, in order to notify GGSN 6 about the successful registration of the MIP. In the subsequent step 31, the GGSN 6 indicates in the Activate PDP Context Reply the HoA address of the mobile station 9 obtained and finishes the structure of the PDP context. [0039] The mobile station 9 can now start sending and receiving data packets via the GGSN 6 of the UMTS 2 network. When receiving user data for the mobile station 9, they are sent by the foreign agent 12 to the mobile station 9, while the signaling as described above, it is implemented by the PMIP client 15. In the case where the R4 tunnel was previously created to the "old" ASN-GW 14, it can be deleted when the GGSN 6 detects that the home agent 11 receives data for the mobile station 9.

[0040] Fig. 3 shows a second flow chart in which a time signaling flow is shown when setting up a mobile station 9 connection in the WiMAX 3 network of the telecommunications system 1 according to Fig. 1. According to the illustrated flow diagram, the network transition takes place. ^{UMTS 2 d}about the stakes. ^{WiMAX 3}. procedures^{y WiMAX} n^andes^and basically changed in relation to the WiMAX standard. In this case, data of the MIP subscriber of the mobile station 9 are already stored in the AAA 18 server, which were obtained at the previous collation of the "old" connection in the UMTS network

2. The subscriber's data can be made available via the AAA server for signaling during the transition to WiMAX 3 network. In the case where the mobile station 9 sets up the first connection to the WiMAX 3 network and has not previously connected to the UMTS 2 network, the AAA server 18 gets new

- the data of the MIP subscriber, as provided for in the current WiMAX procedures, and the acquired MIP subscriber data are then stored in the AAA server so that they can be restored at the next network change.

[0041] First, in step 32, the access of the mobile station 9 to the WiMAX 3 network is performed using the AAA server 18. For this purpose, the MSA data and other MIP data from the AAA server 18 are sent to the so-called Authenticator. The above mentioned Authenticator is located in ASN 7. With Authenticator it is possible to determine first of all whether the mobile station 9 can use the WiMAX network 3. In particular, the Authenticator includes a PMIP client 16. In Fig. 3, the Authenticator and the PMIP client 16 are connected in a common component . In step 32, therefore, the Authenticator is sent, in particular, the key AAA for generating the Message Authentication Code, the MAC, the address HA @ and the IP address HoA of the mobile station 9. In the next step 33 are sent to the ASN-GW 14, in particular the ID of the mobile station^{9 and} IP address, ^HoA ^lat^b PoA, p^tACJ^and can^bilfootball ⁹. ^{ASN-GW 14 and}the foreign agent 13 performs various functions, but for simplicity in Fig. 3 they are combined into a common component.

[0042] In steps 34, 35 and 36, the mobile station 9 requests its IP address from the ASN-GW 14. In this case, the GN 14 ASN plays the role of the so-called Dynamic Host Configuration Protocol, DHCP. The signal flow is implemented in accordance with the current WiMAX procedures by the DHCP Discover message from the mobile station 9 to the ASN-GW 14 in step 34, the subsequent DHCP offer from the ASN-GW 14 to the mobile station 9 in step 35 and the DHCP Request message from the mobile station 9 to ASN-GW 14 in step 36.

[⁰⁰⁴3] ^IN e^tand^pie ^{37 ASN-GW 14,} behind ^phe aid^and hemunAató PoA_Address, sends to the PMIP client 16 the IP address of the mobile station 9, which has already been sent to

-20Authenticator. Receiving the IP address HoA or PoA is confirmed by the PMIP client 16 with the message PoA_Address_Ack in step 38.

[0044] The reception of the PoA_Address message by the PMIP client 16 also starts the MIP procedure. It is implemented in the next stages 39-44. In step 39, the MIP registration procedure begins with the MIP Registration Request message. Steps 39-44 largely correspond to steps 26-29, which are described with reference to Fig. 2. However, there is an "old" foreign agent 12 and a "new" foreign agent 13. "Old" MIP dependencies are respectively between the parent agent 11 and the foreign agent 12 of the UMTS 2 network, while the "new" MIP dependencies are between the parent agent 11 and the foreign agent 13 of the WiMAX 3 network. Due to the largely repeated state of affairs, its description will be omitted.

[0045] In the previous steps, in particular in the MIP registration procedure, the transmission of the IP address HoA, PoA of the mobile station 9 to the mobile station 9 has been delayed. In steps 45 and 46, using the DHCP gating release and DHCP gating messages, the IP address HoA, PoA is sent. In step 47, the ASN-GW 14 sends a DHCP Ack message to the mobile station 9 so that it can start sending data packets.

[0046] During the procedure of Fig. 3 it is also possible to obtain the address of the foreign agent 12 as "the old ASN-GW". In this way, information is obtained that the mobile station 9 is temporarily registered in the UMTS network

2. In this way, the "new" ASN-GW 7 can create a so-called R4 tunnel to GGSN 6 to avoid data loss when changing the network. The mentioned R4 transmission tunnel can then be deleted again as soon as it is no longer needed.

[0047] Fig. 4 shows a second embodiment of a telecommunications system 1 according to the invention with a UMTS network 2 and a WiMAX network 3. In contrast to the first embodiment according to Fig. 1, both networks 2 and 3 do not include PMIP clients, which as a substitute for mobile station 9, they can provide signaling for network change. In the illustrated embodiment, the functionality for implementing the Mobile IP mobility protocol, MIP, is shifted directly to the mobile station 9. It contains a MIP client for this purpose. The telecommunications system 1 according to Fig. 4 comprises, in addition to both PMIP clients 12 and 13, the same components as the telecommunications system 1 according to Fig. 1.

[0048] In the following, it will be described based on F: 1c. 5 only a signal exchange scheme in which the mobile station 9 receives a connection to the UMTS 2 network. This can be done either by switching from the WiMAX 3 network to the UMTS network 2, as well as in a situation where the mobile station 9 is not previously connected to the WiMAX network 3. In step 48, the mobile station 9 creates a so-called PDP context by means of a UMTS network 2. For this purpose, the mobile station 9 transmits to the GGSN 6 the Activate message FDP Context Request. In the event that the mobile station 9 at this point knows that it will probably (again) go down later.^wiMAK ³it is preferable to use an APN that supports MIP and a change to the WiMAX network. In step 49, the GGSN 6 sends the Activate PDP Context Reply to the mobile station 9. In this way, the Context PDP is created, but no IP address is assigned to the mobile station 9. This happens at a later time, during the MIP registration procedure. This is a traditional procedure as described, for example, in 3GPP TS 29.061: "3rd Generation Partnership Project; Technical Specification Group Core Network and

-22Terminals; Interworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Da^ta Iletworks (^PD^N); Rebase 6 "and in 3^{GPP T}S ²9.060: "3r^dGeneration Partnership Project; Technical Specification Group Services and System Aspects; Generall Packet Radio Service (GPRS); service description; Stage 2; Release 6. "In the next step 50, the foreign agent 12 starts sending so-called Agent Advertisements to the mobile station 9. In this way, the mobile station 9 receives CoA and starts the MIP registration procedure.

In the following steps 51-56, a MIP registration procedure is performed for a case where the mobile station 9 has not previously been connected to the WiMAX 3 network. Therefore, probably no information about the mobile station 9, in particular MSA data and other MIP data, such as addresses HA @ and HoA, are not available for MIP registration. The AAA infrastructure planned, in particular the AAA 18 server, can be used to obtain this information. After receiving the Reg_Reply message in step 56 by the mobile station 9, it presents all necessary information so that it can start sending and receiving data.

[0050] In the case where the mobile station 9 is previously connected to the WiMAX 3 network, then a transition from WiMAX 3 to the UMTS 2 network is performed, steps 51-56 are not performed. Instead, after step 50, a step 57 follows in which a Reg_Req message is sent from the mobile station 9 by the foreign agent 12 to the home agent 11 to perform the MIP registration procedure. Then, from the home agent 11, by the foreign agent 12, a Reg_Reply message is sent to the mobile station 9, after which the mobile station 9 can start transmitting and receiving data. In this case, it is not necessary for the AAA infrastructure to be involved in

- performing the MIP procedure, because the mobile station, thanks to its connection to the WiMAX 3 network, already has all the MIP information needed to complete the transition.

[0051] In the event that the mobile station 9 wants to establish a connection to the WiMAX network 3, the procedure for establishing a connection is substantially analogous to that described above with reference to Fig. 3. However, instead of the PMIP client 13, a mobile station 9 is directly present. First, the mobile station 9 performs authentication of access to the WiMAX network. If the mobile station 9 has not previously been connected to the UMTS 2 network, the AAA server 18 sends new MIP information, like MSA data, HA @ and HoA addresses, to the mobile station 9. If the mobile station 9 was previously connected to the UMTS 2 network, the server AAA 18 states this and does not send MIP information to mobile station 9, because they are already there. Alternatively, the AAA server 18 may however send MIP data for simplicity. The mobile station 9 can then perform the normal MIP registration procedure.

[0052] Although the present invention has been described based on preferred embodiments, it is not limited thereto, but can be modified in many ways.