WO2006086952A1

WO2006086952A1 - Communication system method for operation of a communication system communication network and method for operation of a communication network

Info

Publication number: WO2006086952A1
Application number: PCT/DE2006/000249
Authority: WO
Inventors: Maik Bienas; Achim Luft; Holger Schmidt
Original assignee: Infineon Technologies Ag
Priority date: 2005-02-17
Filing date: 2006-02-13
Publication date: 2006-08-24
Also published as: DE102005007339A1

Abstract

A communication system, comprising a communication terminal and a communication network are disclosed, whereby the communication network comprises an allocation device, embodied to transform the network layer addresses of a communication provider server to a unique identifier for the communication provider sever and transmission of the same to the communication terminal. The network layer addresses of a communication provider server can thus be kept secret from the communication terminal.

Description

A communication system, a method of operating a communication system, a communication network, and a method of operating a communication network

The invention relates to a communication system, a method for operating a communication system, a communication network and a method for operating a communication network.

In recent years, it has become a matter of course that there is the possibility to make mobile calls almost everywhere.

Recently, it has also been possible to use packet-switched (communication) services with high data rates for mobile use.

The second generation mobile radio systems typically used today, such as Global System of Mobile Communications (GSM) mobile communications systems, are primarily intended for cellular voice communications, and are poorly suited for the low transmission data rates provided by such a mobile radio system

Transmission of large amounts of data suitable.

Several mobile communication systems have been and are being developed that are capable of providing high-rate packet-switched services.

For example, work for the development and standardization of UMTS (Universal Mobile Telecomunication System) standards as part of the 3rd Generation Partnership Project (3GPP).

A UMTS communication system, that is, a UMTS standard communication system, provides users with various circuit-switched services and packet-switched services, and will be available in the near future among others in much of Europe.

Furthermore, so-called "Wireless Local Area Networks"

(WLANs), known. WLANs are specially designed for the radio transmission of packet-switched services.

WLANs enable data transmission with higher data rates compared to UMTS communication systems, but do not allow the mobility of users to the extent that UMTS communication systems allow.

WLANs are specified, for example, by the IEEE 802.11 standard and the HIPERLAN or HIPERLAN / 2 standard.

Future (mobile) subscriber devices are expected to be set up to use not only second-generation mobile radio communication systems but also UMTS communication systems and WLAN, that is,

Establish communication links to UMTS communication systems and WLANs and transmit data by means of the communication connections.

Accordingly, the situation will often arise that a user of a subscriber device uses a packet-switched communication service by means of a communication connection to a UMTS communication system and, during the communication connection is moved into the coverage area of a WLAN radio cell, that is to say into the geographical area in which a WLAN can be used by means of the subscriber device.

It may be advantageous for the user as well as for the operator of the UMTS communication system if the user uses the communication connection by means of the WLÄN instead of the UMTS communication system, for example because a higher data rate can be made available by means of the WLAN. In conventional UMTS communication systems, however, the communication connection using the UMTS communication system remains. When the user leaves the coverage area of the UMTS communication system, i. the geographical area in which the user can use the UMTS communication system by means of his user equipment, the communication connection to the UMTS communication system would be terminated and not be continued by means of a communication connection to a WLAN, even if the user is in a WLAN radio cell located. In particular, the use of the communication service would have to be interrupted because a change of the communication system by means of which the communication service is used is currently not possible without interruption.

So that the subscriber device can continue to use the packet-switched communication service without interruption by means of a communication connection to the WLAN, a communication system change from the UMTS communication system to the WLAN is required, so that always a communication connection to the WLAN or a There is a communication connection to the UMTS communication system.

Collaboration between UMTS communications systems and WLANs is being standardized by the standardization body of 3GPP under the name "3GPP System to WLAN Interworking".

The degree of cooperation between UMTS communication systems and WLAN was divided into β stages and 6 scenarios were defined, which are referred to as Scenario 1 to Scenario 6. According to Scenario 1, there is the least degree of cooperation, and according to Scenario 6, there is the greatest degree of cooperation. From Scenario 4, that is, according to Scenario 4, Scenario 5 and Scenario 6, there is the possibility of an inter-system handover, that is, a communication system change between UMTS communication systems and WLANs (see [1], Chapter 6.5).

Currently Scenario 3 is specified. Procedures for inter-system handover have not yet been specified.

FIG. 1 shows a UMTS communication system 100 for providing packet-switched services.

A subscriber device 101 is coupled to a UMTS mobile network 103 by means of a first base station 102, which is referred to as NodeB in the UMTS standard.

The first base station 102 is the radio interface between the user equipment 101 and the UMTS mobile radio network 103 and enables the transmission of radio signals. The first base station 102 is coupled to a Radio Network Controller (RNC) 104. The RNC 104 essentially has tasks related to the control of the air interface, such as the allocation of radio resources in a communication connection setup.

There may be further base stations coupled to the RNC 104, here for example a second base station 110.

The Internet Protocol (IP) is used to transmit data packets. A SGSN (Serving GPRS Support Node) 105, illustratively speaking from the point of view of the IP, couples the subscriber device 101 to the UMTS mobile radio network 103 and provides the functionality of a router. The SGSN 105 is still used for

Authentication of users for mobility management.

By means of a GGSN (Gateway GPRS Support Node) 106, the UMTS mobile radio network 103 is coupled to external packet-based communication networks, here for example the Internet 107. The GGSN 106 also provides the functionality of a router.

The GGSN is further coupled to an IMS (IP Multimedia Subsystem) 108, that is, a communication system according to the IMS standard.

An IMS is a packet-based communication system. The IMS standard has been developed to offer services that are typical of circuit-switched transmission, such as voice telephony. An HLR (Home Location Register) 109 contains data required to establish a communication connection and to authenticate the user of the user equipment 101.

In addition to the GGSN 106, the UMTS communication system 100 may include further GGSNs (not shown). In this way, through redundancy, a higher reliability and above all availability can be achieved and data traffic can be distributed over several network elements. Demands that

Subscriber device 101 to a communication service, for which a GGSN is required, the GGSN 106 or one of the other GGSN is selected by a DNS (Domain Name Service) server.

The subscriber device 101 requests a communication service by sending a PDP context request to the SGSN 105. The PDP Context Request optionally contains an APN (Access Point Name). An APN is a non-unique reference to a GGSN and always has an identification specifying the communication service requested by the user equipment 101.

Further, the APN may include an operator identification (Operator ID) specifying a communication network by which the communication service is to be used. In this way, it is possible for the subscriber device 101 to use a communication service provided by a communication network other than the UMTS mobile network 103. The operator identification is optionally included in the APN. If no operator identification is included in the APN, then the communication service of the current communication network, in this case the UMTS radio network 103, provided.

To determine an IP address of a GGSN corresponding to the APN, the SGSN 105 sends a request to a

DNS (Domain Name Service) server (not shown). The DNS server contains a mapping table by means of which an IP address can be assigned to the APN. However, this assignment is not unique. The DNS server transmits to the SGSN 105 the IP address of any GGSN that can provide the requested communication service. This is the GGSN 106 shown in this example.

In order to achieve a uniform utilization of the GGSNs of the UMTS mobile radio network 103, e.g. a round

Robin method used, i. at each request for the provision of the communication service, the next GGSN is selected in a list of the GGSNs suitable for the communication service.

For example, the APN has the form myIMS.mncO12.mcc345.grps. The string myIMS is the required communication service identification and the string mncO12, mcc345 is the optional operator identification (network identification). The label gprs indicates that the APN is used in the context of a communication network according to the 3GPP standard. After the SGSN 105 has resolved the APN, i. In this case, the IP address of the GGSN 106, SGSN 105 establishes a direct communication link to the GGSN 106.

2 shows a communication system 200 with a WLAN access network 203. A subscriber device 201 is coupled to the WLAN access network 203 by means of a first access point (AP) 202. The first access point 202 serves as a radio interface and enables the transmission of radio signals.

The access point 202 and possibly further access points, here for example a second access point 204, are coupled to an access router (AR) 205. The access router 205 is responsible for controlling handovers between the connected access points 202, 204 and couples the subscriber device 201 to the Internet 206 and an AAA server (Authentication, Authorization and Accounting Server) 207.

The Access Router 205 provides the functionality of a router.

The AAA server 207 is used to authenticate and verify the authority of the users. Further, the AAA server 207 generates the data used for detecting communication connection charges.

3 shows a communication system 300 with a WLAN / 3G interworking network 310.

The WLAN / 3G interworking network 310 is configured according to the 3GPP standard for Scenario 3.

The WLAN / 3G interworking network 310 couples a UMTS mobile network 311 having the network architecture discussed with reference to FIG. 1 to a WLAN access network 312, which has the network architecture explained with reference to FIG.

As described with reference to FIG. 1, the UMTS mobile radio network 311 has base stations 302, 303 which are connected by means of an RNC

304 are coupled to an SGSN 305, a GGSN 306 coupled to the SGSN 305, the Internet 307, an IMS 308, and an HLR 309.

The WLAN access network 312 comprises access points 313, 314 and an access router 316 as described with reference to FIG. A subscriber device 315 is coupled to the access router 316 via one of the access points 313, 314.

The communication system 300 allows the access of the

Subscriber device 315 by means of the WLAN access network 312 on packet-switched (communication) services, which are provided by means of the UMTS communication network 311, for example, access to the IMS 308th

If the user of the subscriber device 315 wishes to use these services, authentication and authorization by means of an AAA server 316 of the WLAN / 3G interworking network 310 is required.

An AAA server, which the WLAN access network 312 may have, can not be used for this.

A PDG (Packet Data Gateway) 317 provides access to the Internet 307 and IMS 308 and provides the functionality of a router. For detecting communication connection charges, the AAA server 316 is coupled to the PDG 317.

A WAG (WLAN Access Gateway) 318 has, in essence, the task of providing a communication connection to the home UMTS communication network (not shown) of a user of a subscriber device (not shown) if there is a communication connection from the subscriber device to the UMTS mobile radio network 311 and this is a visited UMTS communication network and not the user's home UMTS communication network.

For this, the WAG 318 has a communication connection to the PDG of the home UMTS communication network (not shown). The WAG 318 provides the functionality of a router.

The possibility of communicating with the home UMTS communication network by means of a visited UMTS communication network is called roaming.

If a user of the subscriber device 315 wishes to use a communication service by means of the WLAN access network 312, the selection of a PDG and the determination of the IP address of the selected PDG are similar to the case of a UMTS mobile radio network, as explained above with reference to FIG , The subscriber device 315 contacts a DNS server which converts a W-APN (WLAN Access Point Name) into the IP address of a PDG suitable for providing the communication service, ie the IP address of a suitable PDG, for example the PDG 317 shown, transmitted to the subscriber device 315. Unlike in the case of a UMTS mobile network, the user equipment 315 itself requests an IP address at a DNS server and not an intervening network element such as the SGSN 305 in the case of a UMTS mobile network.

In particular, the subscriber device 315 receives the IP address of the selected PDG 317 directly. The user equipment 315 directly contacts the PDG 317 using the IP address. Clearly, the WAG 318 is transparent to the subscriber device.

It is advantageous for an improved inter-system handover between the UMTS mobile network 311 and the WLAN access network 312 to combine the PDG 317 and the GGSN 306 in a network element common to the UMTS mobile network 311 and the WLAN access network 312. In this case, the common network element has different interfaces to the SGSN 315 (illustratively to the UMTS side) and to the WAG 318 (illustratively to the WLAN side) as well as to further communication systems, for example the Internet 307.

WLAN interworking according to 3GPP is described in [2]. GPRS according to 3GPP is described in [3].

Document [4] describes a communication system with a WLAN and a UMTS communication network, in which a communication terminal sends a request with the specification of an access point name of a communication service server to a Domain Name Service server in order to transmit the

Determine network layer address of the communication service server. The invention is based on the problem of providing a method for an inter-system handover between a UMTS communication network and a WLAN, in which the security of the UMTS communication network is ensured.

The problem is solved by a communication system, a method for operating a communication system, a communication network and a method for operating a communication network having the features according to the independent patent claims.

There is provided a communication system having a communication terminal and a communication network, wherein the communication network has a

Communication service server that is configured to provide a communication service. The communication terminal is set up to transmit a request for the provision of the communication service to the communication network. The

Communication network has an allocation device that is configured to map the network layer address of the communication service server to a unique identification of the communication service server and a signaling device that is configured to transmit the identification to the communication terminal. The communication terminal is configured to request using the identification that the communication service server provides the communication service for the communication terminal.

The communication network clearly communicates the identification of the communication terminal to the communication terminal Communication service servers with it

Communication terminal allows to address the communication service server and to submit a request for the provision of the communication service to the communication service server without the communication terminal the network layer address of the communication service server is known (the request can be done indirectly, that is by means of a another network element to which the identification of the communication service server is notified by the communication terminal).

In this way, in particular the network layer address of the communication service server before the communication terminal and before the user of the

Communication service terminal are kept secret. Details about the network topology of the communication network are thus kept secret from the user of the communication terminal, thereby increasing the network security of the communication network.

For example, details about the communication network remain hidden from a potential hacker, and the hacker can not launch an attack on the communication service server because the network layer address of the communication server is not

Communication service server is not known. In the event that the communication network has a UMTS (Universal Mobile Telecommunication System) communication network and a WLAN (Wireless Local Area Network), it becomes the communication terminal, for example a mobile subscriber unit, in the case of an inter-system handover from the UMTS Communication network to the WLAN allows the communication service server, such as a GGSN (GPRS Support GPRS General Packet Radio Service) to address, which is particularly advantageous if the GGSN is combined with a PDG (Packet Data Gateway) to a network element, since in this case the mobile subscriber unit in the course of the inter-system handover the PDG can address.

The mobile subscriber device thus makes it possible to uniquely refer to the GGSN without the mobile subscriber device being informed of details about the network topology of the communication network. Clearly, as described below, the APN (Access Point Name) - resolution of the SGSN (Serving GPRS Support Node), which is assigned to the mobile subscriber unit, extended. In this case, the mapping of the network layer address, which in this case is an IP (Internet Protocol) address, is done by a Domain Name Service (DNS) server. The mobile subscriber unit remains hidden the IP address of the GGSN and the mobile subscriber unit, it is not possible to contact the DNS server itself and so dissolve the identification in an IP address. By means of the identification, the mobile radio subscriber device can determine in the course of an inter-system handover a W-APN (WLAN Access Point Name), which uniquely references the PDG, which is combined with the GGSN to form a network element.

If the GGSN provides a communication connection to the Internet for the mobile radio subscriber unit as a communication service, then it is easily possible for the PDG, which is combined with the GGSN to form a GGSN / PDG, to provide the communication service after an inter-system handover. In this way, a fast inter- System handovers are performed (without interrupting the communication service), since the external network layer address, ie the network layer address that is used to address the network element that provides the Koinmunikationsdienst, ie the GGSN / PDG, from the Internet, in History of inter-system handover does not change. Thus, no re-routing must be performed, but the redirection of the data transmitted in the context of the communication service can be done by simply switching to GGSN / PDG.

If, on the other hand, different network elements were used to provide the communication service by means of the UMTS communication network or the WLAN, a complex forwarding of the data between the

Network elements are implemented, which would result in delays in the continuation of the communication service using the WLAN in the context of an inter-system handover.

Thus, significant delays are avoided in the inter-system handover without the IP address of the GGSN is transmitted to the mobile subscriber unit.

Further, a method of operating a communication system, a communication network, and a

Method for operating a communication network according to the communication system described above.

Preferred developments of the invention will become apparent from the dependent claims. The further embodiments of the

Invention, which are described in connection with the communication system, apply mutatis mutandis to the method for operating a communication system, the Communication network: and the method for operating a communication network.

In one embodiment, the communication network has a first access network and a second access network, the request is a request for the provision of the communication service by means of the first access network and the signaling device is set up, the identification to the communication terminal as a result of the request of the communication terminal to the communication terminal to convey.

For example, the communication terminal is configured to request using the identification that the communication service server provides the communication service for the communication terminal via the second access network.

As explained above, the invention is illustratively used in the context of an inter-system handover from the first access network (for example a UMTS communication network) to the second access network (for example a WLAN).

In one embodiment, the first access network is a

UMTS communication network, the communication service server GGSN and / or the signaling device SGSN.

For example, the second access network is a WLAN.

In one embodiment, the unique identifier is an APN. In one embodiment, the allocation device is a DNS server.

For example, the communication service is providing a communication connection to another communication system.

In one embodiment, the communication connection is a packet-switched communication connection.

The other communication system can be the Internet.

Illustratively, for example, a GGSN as a communication service provides a communication link from a mobile radio subscriber device to the Internet, which should exist seamlessly (without interruption) as part of an inter-system handover, that is to say by means of the access network to which the inter-system handover takes place. should be continued without interruption.

In one embodiment, the network layer address is an IP address of the communications service server by means of which the communications service server is addressable within the communications network.

Due to the fact that the IP address is not known when using the invention, the invention is particularly suitable as part of an inter-system handover of a UMTS mobile network to a WLAN.

Embodiments of the invention are illustrated in the figures and are explained in more detail below. FIG. 1 shows a UMTS cortiming system for

Provision of packet-switched services;

Figure 2 shows a communication system with a WLAN access network;

Figure 3 shows communication system with a WLAN / 3G interworking network;

Figure 4 shows a communication system according to an embodiment of the invention.

FIG. 5 shows a message flow diagram according to FIG

Embodiment of the invention.

4 shows a communication system 400 according to an embodiment of the invention.

The architecture of the communication system 400 is based on the architecture of a WLAN / 3G interworking network according to

Scenario 3, as explained above with reference to FIG.

A UMTS mobile radio network 401 has base stations 402, 403 coupled to an SGSN 405 by a Radio Network Controller (RNC) 404, an IMS (IP Multimedia Subsystem) 406, an HLR (Home Location Register) 407, an AAA (Authentication , Authorization and Accounting Server) - Server 409 and a WAG (WLAN Access Gateway) 408, each with the functionality described with reference to Fig.l and Fig.3. A WLAN 410 has access points 413, 414 and an access router 416, each with the functionality described with reference to FIGS. 2 and 3.

The communication system further includes a user equipment 415.

In contrast to the network architecture explained with reference to FIG. 3, the UMTS mobile radio network 401 has a PDG / GGSN 411 instead of a GGSN and a PDG.

The PDG / GGSN 411 provides the functionality of a GGSN and the functionality of a PDG.

By means of the PDG / GGSN 411, the SGSN 405, the IMS 406, the HLR 407, the AAA server 409, the WAG 408 and the Internet 412 are coupled together.

The mobile subscriber device 415 is provided with a UMTS transmitter and a UMTS receiver and with a WLAN transmitter and WLAN

Receiver, that is, the user equipment 415 can communicate with both the UMTS mobile network 401 and the WLAN 410.

The UMTS transmitter of the user equipment 415, the UMTS receiver of the user equipment 415, the WLAN transmitter of the user equipment 415 and the WLAN receiver of the user equipment 415 can be operated simultaneously.

In the following, a handover is always understood to mean an inter-system handover. The following describes how the user equipment 415 requests a communication service provided by the UMTS communication system 401 and how to perform an inter-system handover so that the communication service is no longer disconnected from the UMTS mobile network 401 without interruption is provided to the WLAN 410, that is, by means of the WLAN 410 is continued.

5 shows a message flow diagram 500 according to an embodiment of the invention.

The illustrated message flow occurs between a user equipment 501, an SGSN 502, a first Domain Name Service (DNS) server 503, an HLR 504, a GGSN / PDG 505, a second DNS server 506, and an AAA server 507. The user equipment 501, the SGSN 502, the HLR 504, the GGSN / PDG 505 and the AAA server 507 are arranged and configured as explained with reference to FIG. In particular, a GGSN 550 and a PDG 551 are combined to the GGSN / PDG 505.

It is assumed that there is a radio communication link between the user equipment 501 and the UMTS mobile radio network 401 and that the user equipment is registered in the packet switched area of the UMTS mobile radio network 401, i.e., that a GPRS attach has been performed.

It is assumed that the user of the user equipment 501 wishes to set up an Internet session in step 508, that is, establish a communication connection from the user equipment 501 to the Internet 412. The subscriber device 501 transmits a PDP Context Request message 536 to the SGSN 502. The PDP context request message 536 specifies a PDP context requested by the user equipment 501. In particular, a first APN is specified, which in this example has the form Internet@mncO12.mcc345.gprs.

In step 509, the SGSN 502 checks, based on the user device's internal policies and user profile of the subscriber device 501 stored in the HLR 504, whether the user is authorized to use the requested PDP context. Clearly, an authorization is carried out.

In step 510, if the PDP context is authorized, the SGSN 502 requests a resolution of the first APN at the first DNS server 503, i. sends a first APN resolution request 537 to the first DNS server 503, requesting that the first DNS server 503 send the IP address of a GGSN that can provide a communication link to the Internet for the subscriber device 501 to the SGSN 502 is transmitted.

In step 511, the first DNS server 503 correspondingly transmits a first IP address 538 to the SGSN 502. The first IP address has the form 134.219.233.86. The first IP address is the IP address of a GGSN that can provide a communication link to the Internet 412 for the subscriber device 501. It is believed that this is the GGSN 550. The first IP address 538 is thus the UMTS-side IP address of the GGSN / PDG 505, ie the IP address of the GGSN / PDG 505, by means of which the GGSN / PDG 505 within the UMTS mobile radio network 401 is addressed. However, the association between the first APN and the first IP address 538 is not unique. As the UMTS mobile network 401 may have multiple GGSNs, the first DNS server 503 could also select the IP address of a GGSN other than that of the GGSN 550.

In step 512, the SGSN 502 queries the first DNS server 503 for a unique name (unique identifier) of the GGSN 550.

In step 513, the first DNS server 503 responds to the request of the SGSN 502 and transmits a second APN uniquely assigned to the first IP address. The second APN in this example is GGSN7325@mnc012.mcc345.gprs.

In step 514, the SGSN 502 acknowledges the request of the PDP context by means of a first PDP Context ACK message 539 containing the second APN.

In step 515, the communication link between the Internet 412 and the user equipment 501 is established. Subscriber device 501 now sends payload data to SGSN 502, which forwards the payload data to GGSN / PDG 505, which has the functionality of a gateway to Internet 412. Conversely, the GGSN / PDG 505 receives payload data for the

Subscriber device 501 from the Internet 412. The GGSN / PDG 505 is within the Internet by means of a second IP address (in this example, this is the IP address 86.245.12.63) addressed. The data received from the GGSN / PDG 505 from the Internet 412 is forwarded from the GGSN / PDG 505 to the SGSN 502 and ultimately forwarded by it to the subscriber device 501. The logical co-communication connection between the user equipment 501 and the GGSN / PDG 505 is made by means of the PDP context requested in step 508.

It is assumed that the user of the

Subscriber device 501 in step 516 in a WLAN radio cell of the WLAN 410, that is in the geographical coverage of the WLAN 410, moves. Since a higher bandwidth can be provided by means of the WLAN 410 than by means of the UMTS mobile radio network 401, it is assumed that the user of the subscriber device 501 wishes to continue the communication connection to the Internet by means of the WLAN 410, that is, the communication connection to the Internet from now on be provided by means of a radio communication link from the subscriber device 501 to the WLAN 410.

For this purpose, the user equipment 501 first authenticates in the WLAN 410 (this is done in a conventional manner and will not be described in detail) and a wireless communication link is established from the user equipment 501 to the WLAN 410.

In step 517, the user equipment 501 sends a second APN resolution request 544 to the second DNS server 506 by which it requests the resolution of the second APN.

In step 518, the second DNS server 506 transmits the IP address of the PDG combined with the GGSN specified by the second APN to a GGSN / PDG, that is, the IP address of the PDG 551, to the user equipment 501. The IP address of the PDG 551 is 134.219.73.42. In step 519, the user equipment 501 sets up a tunnel to the PDG 551. This is done using the IP address of the PDG 551 (134.219.73.42).

In step 520, after successful establishment of the tunnel, the subscriber device 501 transmits an APN request message 541 to the PDG 551. The APN request message 541 specifies an APN request, the third APN used for this purpose being used as service ID (communication service). Identification) includes the identification of the communication service desired by the user of the user equipment 501 (in this case a communication connection to the Internet 412). By means of the APN request message is further signaled that the desired communication service is already provided by means of the UMTS mobile radio network 401 and is now to be provided by means of the WLAN 410, i. to be continued by means of the WLAN 410. The third APN used for the APN request also has (eg at the end) the second APN. The third APN thus has, for example, the form Internet / HO: GGSN7325@mnc072.mcc345. gprs.

The signaling of the second APN by means of the third APN enables the PDG 551 to check whether it is actually the PDG that is merged with the GGSN into a GGSN / PDG that provides the communication service so far via the UMTS mobile network 401.

In step 521, the PDG 551 checks by asking the AAA server 507 if the APN request from step 520 is authorized. In step 522, the PDG 551 confirms to the subscriber device 501 the use of the desired communication service.

In step 523, after successful authorization in the GGSN / PDG 505, the routing of the data received from the Internet 412 for the subscriber device 501 from the GGSN / PDG is switched from the GGSN 550 to the PDG 551. This means that in the subsequent step 524 the data received from the Internet 412 by the GGSN / PDG 505 and intended for the subscriber device 501 are forwarded by the PDG 551 to the subscriber device 501 by means of the WLAN 410. '

The switching from the GGSN 550 to the PDG 551 for the data coming from the Internet can be performed without delay because the GGSN 550 and the PDG 551 are merged to the GGSN / PDG 505 to a physical device and not other network elements via the switching of the routing must be informed. Specifically, the data coming from the Internet 412 destined for the user equipment 501 is sent to the same IP address since the GGSN / PDG 505 and thus the GGSN 550 and the PDG 551 are sent by means of a single IP address (the IP address 86.245. 12.63) within the Internet.

In step 525, the remaining PDP context (which is associated with the first APN Internet@mncO12.mcc345.gprs) is degraded because the user equipment 501 is now the communication service by means of the WLAN 410 (corresponding to the third APN Internet / HO: GGSN7325 @ mncO12 .mcc345. gprs). For this purpose, the user equipment 501 sends a PDP Release Request message 542 to the SGSN 502, which confirms the removal of the PDP context by means of a Release ACK message 543 in step 526. It is assumed that the user with his user equipment 501 moves out of the coverage area of WLAN 410 in step 527. In particular, the communication service (ie the communication connection to the Internet 412) is to be provided again by means of the UMTS mobile radio network 401.

In step 528, the user equipment 501 sends a second PDP context request message 543 to the SGSN 502, signaling the third APN to the SGSN 502.

Analogous to step 509, an authorization of the requested PDP context is performed in step 529.

In step 530, analogously to step 510, the SGSN 502 transmits a third APN resolution request 544 to the first DNS server 503 containing the third APN.

Since the second APN uniquely specifying the GGSN 550 is part of the third APN, the first DNS server 503 in response transmits the first IP address 538, which is the IP address of the GGSN 550 within the UMTS mobile network 401 ,

Accordingly, to provide the requested PDP context, the SGSN 502 contacts the GGSN 550 and, in step 532, transmits a second PDP context ACK message 539 to the user equipment 501 as confirmation of the establishment of the requested PDP context.

In step 533, the communication service is now provided again by means of the UMTS mobile radio network 401. Since it is no longer necessary for the communication service to be provided by means of WLAN 410, in step 534, the user equipment 501 sends an APN removal request message 540 to the GGSN / PDG 505, which terminates the provision of the communication service via the WLAN 410 and transmit an APN Release ACK message 541 to the subscriber device 501 for confirmation.

In the procedure described becomes the first IP address

(134.219.223.86) has never been communicated to user equipment 501. The IP addressing of the GGSN 550 thus remains network-internal.

This document cites the following publications:

[1] 3GPP TSG-SA, TR 22.934, 3rd Generation Partnership

Project; Technical Specification Group Services and System Aspects; Feasibility study on 3GPP System to

Wireless Local Area Network (WLAN) interworking (Release 6)

[2] 3GPP TSG-SA, TS 23.234 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; 3GPP System to Wireless Local Area Network (WLAN) Interworking; System Description (Release 6)

[3] 3GPP TSG-SA, TS 23.060 3rd Generation Partnership

Project; Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS); Service description; Stage 2 (Release 6)

[4] Salkintzis, Apostolis K .: WLAN / 3G Interworking

Architectures for Next Generation Hybrid Data Networks. 2004 IEEE International Conference on Communications, 20-24 June 2004. Proceedings, Vol. 7, pp. 3984 - 3988

LIST OF REFERENCE NUMBERS

100 ÜMTS communication system

101 subscriber device

102 base station

103 UMTS mobile network

104 RNC

105 SGSN

106 GGSN

107 Internet

108 IMS

109 HLR

200 communication system

201 subscriber device

202 access point

203 Wi-Fi access network

204 access point

205 access router

206 Internet

207 AAA server

300 communication system

302,303 base station

304 RNC

305 SGSN

306 GGSN

307 Internet

308 IMS

309 HLR

310 WLAN / 3G Interworking Network

311 UMTS mobile network

312 Wi-Fi access network

313,314 access point

315 subscriber device

316 AAA server 317 PDG

318 WAG

400 communication system

401 UMTS mobile network

402,403 base station

404 RNC

405 SGSN

406 IMS

407 HLR

408 WAG

409 AAA server

410 WiFi

411 GGSN / PDG

412 Internet

413,414 access points

415 subscriber device

416 Access Router

500 message flowchart

501 subscriber device

502 SGSN

503 first DNS server

504 HLR

505 GGSN / PDG

506 second DNS server

507 AAA server

508-535 process steps

536,537 messages

538 first IP address

539-544 news

Claims

claims

A communication system comprising a communication terminal and a communication network, wherein - the communication network comprises a communication service server configured to provide a communication service;

- The communication terminal is arranged to transmit a request for the provision of the communication service to the communication network;

- The communication network has an allocation device which is adapted to map the network layer address of the communication service server to a unique identification of the communication service server; - The communication network has a signaling device which is adapted to transmit the identification to the communication terminal; and

- The communication terminal is arranged to request using the identification that the communication service server provides the communication service for the communication terminal.

The communication system according to claim 1, wherein the communication network comprises a first access network and a second access network, the request is a request for the provision of the communication service by means of the first access network and the signaling device is set up, the identification to the communication terminal as a result of the request from the Communicate communication terminal to the communication terminal.

3. The communication system according to claim 2, wherein the communication terminal is configured to request, using the identification, that the communication service server provides the communication service for the communication terminal via the second access network.

4. Communication system according to claim 2 or 3, wherein the first access network is a UMTS communication network.

The communication system according to claim 4, wherein the communication service server is a GGSN.

The communication system according to claim 4, wherein the signaling means is an SGSN.

The communication system according to one of claims 2 to 6, wherein the second access network is a WLAN.

The communication system according to one of claims 1 to 7, wherein the unique identification is an APN.

9. Communication system according to one of claims 1 to 8, wherein the allocation means is a DNS server.

The communication system according to one of claims 1 to 9, wherein the communication service is to provide a communication connection to another communication system.

The communication system according to claim 10, wherein the communication connection is a packet-switched communication connection.

12. Kornmunikationssystem according to claim 10 or 11, wherein the further communication system is the Internet.

The communication system according to one of claims 1 to 12, wherein the network layer address is an IP address of the communication service server by means of which the communication service server is addressable within the communication network.

14. A method for operating a communication system with a communication terminal and a

A communication network, wherein the communication network comprises a communication service server configured to provide a communication service, and wherein according to the method

- the communication terminal transmits a request for the provision of the communication service to the communication network; the communication network maps the network layer address of the communication service server to a unique identification of the communication service server;

the communication network transmits the identification to the communication terminal and the communication terminal using the

Identification requests that the communication service server provide the communication service for the communication terminal.

15. Communication network of a communication system, which communication system comprises a communication terminal, wherein the co-communication network has a communication service server that is set up to provide a communication service;

- The Koπununikationsnetzwerk has a receiving device which is adapted to a request for the

Providing the communication service to receive from the communication terminal;

- The communication network has an allocation device which is adapted to map the network layer address of the communication service server to a unique identification of the communication service server;

- The communication network has a signaling device which is adapted to transmit the identification to the communication terminal.

16. A method of operating a communication network of a communication system, the communication system comprising a communication terminal, the communication network having a communication service server configured to provide a communication service, and wherein according to the method

the co-communication network receives a request for the provision of the communication service from the communication terminal; the communication network maps the network layer address of the communication service server to a unique identification of the communication service server;

- The communication network transmits the identification to the communication terminal.