DE102004031126A1 - Communication system, has universal mobile telecommunication system, and net access device that has control device, which is furnished to diminish communication connections between participant device and one of networks - Google Patents

Abstract

The system has universal mobile telecommunication system communication networks, a participant device and a net access device (415), which is assigned to a switching layer address. The access device has a control device, which is furnished to diminish communication connections between the participant device and one of the networks, where the address is used during data transmission of one of the connections. An independent claim is also included for a method for controlling a communication system.

Description

The The invention relates to a communication system, a method for controlling a communication system, a network access device and a Method for controlling a network access device.

In In recent years it has become obvious that opportunity exists almost everywhere to make mobile calls.

since There is also the option of packet-switched Mobile (communication) services with high data rates.

The currently used mobile communications systems of the second Generation, such as mobile systems according to the GSM (Global System of Mobile Communications) standard, are prioritized for cellular voice connections and are because of the low transmission data rates, the such a mobile system provides only bad for the transmission greater Data volumes suitable.

It have been and are being developed several mobile communication systems which are capable of packet-switched services with a high data rate provide.

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

One UMTS communication system, that is a communication system according to the UMTS standard, provides users with various circuit-switched services and Packet-switched services ready and will be available in the near future others are available in much of Europe.

Further are so-called "wireless Local Area Networks "(WLAN), known. WLANs are especially for the radio transmission designed by packet-switched services.

WLANs enable the data transmission with compared to higher data rate UMTS communication systems but not mobility the user to the extent as made possible by UMTS communication systems.

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

Become future (mobile) subscriber devices expected to be set up, in addition to cellular communication systems the second generation also UMTS communication systems and to use Wi-Fi, that is, Communication links to UMTS communication systems and WLAN build and transmit data by means of the communication links.

Accordingly becomes common the situation occurs that a user of a subscriber device a packet-switched service by means of a communication connection uses to a wifi and while the communication connection from the coverage area of a WLAN radio cell, this means the geographical area in which the WLAN is used by means of the subscriber device can be moved out.

typically, would in in this case the communication connection to the WLAN is terminated, even if outside the WLAN radio cell, the supply by a UMTS communication system is given, that is, that the subscriber device the packet-switched service by means of a communication connection could continue to use to the UMTS communication system.

In order to the subscriber device the packet-switched service by means of a communication connection to the UMTS communication system can continue to use is a communication system change of the WLAN to the UMTS communication system required, so that always a communication link to the WLAN or a communication connection to the UMTS communication system consists.

The Collaboration between UMTS communication systems and WLAN will by the standardization body of 3GPP under the designation "3GPP system to WLAN Interworking "standardized.

Of the Degree of cooperation between UMTS communication systems and WLAN has been in Divided 6 levels and 6 scenarios were defined, which be referred to as Scenario 1 to Scenario 6. According to Scenario 1 is the lowest level of cooperation and Scenario 6 is the greatest degree cooperation. From Scenario 4, that is, according to Scenario 4, Scenario 5 and Scenario 6, there is the possibility an inter-system handover, that is, a communication system change between UMTS communication systems and WLAN (see [1], chapter 6.5).

Currently Scenario 3 is specified. Procedures for an Inter-System Handover have not been specified yet.

1 shows a UMTS communication system 100 for the provision of packet-switched services.

A subscriber device 101 is by means of a first base station 102 , which is called NodeB in the UMTS standard, with a UMTS radio network 103 coupled.

The first base station 102 is the radio interface between the subscriber device 101 and the UMTS wireless network 103 and enables the transmission of UMTS radio signals.

The first base station 102 is with an RNC (Radio Network Controller) 104 coupled. 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 can be more base stations with the RNC 104 coupled, here, for example, a second base station 110 ,

The Internet Protocol (IP) is used to transmit data packets. SGSN (Serving GPRS (General Packet Radio Service) Support Node) 105 coupled, vividly speaking from the point of view of the IP, the subscriber device 101 with the UMTS radio network 103 and provides the functionality of a router. The SGSN 105 continues to authenticate users to mobility management.

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

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

One IMS is a packet-based communication system. The IMS standard was developed to offer services, the typical of a circuit-switched transmission are, such as voice telephony.

An HLR (Home Location Register) 109 Contains all the data needed to establish a communication connection and to authenticate the user of the user equipment 101 required are.

2 shows a communication system 200 with a wireless access network 203 ,

A subscriber device 201 is by means of a first access point (AP) 202 with the wireless access network 203 coupled. The first access point 202 serves as a radio interface and enables the transmission of radio signals.

The access point 202 and possibly other access points, here for example a second access point 204 , are with an access router (AR) 205 coupled. The access router 205 is for controlling handover between the connected access point 202 . 204 responsible and couples the subscriber device 201 with 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 user's authority.

Furthermore, the AAA server generates 207 the data used to collect communication connection charges.

3 shows a communication system 300 with a wireless / 3G interworking network 310 ,

The WLAN / 3G Interworking Network 310 is designed according to the 3GPP standard for Scenario 3.

The WLAN / 3G Interworking Network 310 couples a UMTS communication system 311 that's referring to 1 explained network architecture, with a wireless communication system 312 that's referring to 2 has explained network architecture.

The UMTS communication system 311 points, as with respect to 1 described, base stations 302 . 303 by means of an RNC 304 with a SGSN 305 coupled, a GGSN 306 who with the SGSN 305 the internet 307 , an IMS 308 and an HLR 309 is coupled, up.

The wireless communication system 312 points, as with respect to 2 described access points 313 . 314 and one using one of the access points 313 . 314 with an access router 316 coupled subscriber device 315 on.

The communication system 300 allows access of the user equipment 315 using the wireless access network 312 to packet-switched (communication) services using the UMTS communication network 311 be provided, for example, access to the IMS 308 ,

Would like the user of the user equipment 315 use these services, so is an authentication and authorization using an AAA server 316 of the WLAN / 3G interworking network 310 required.

An AAA server using the wireless access network 312 possibly has, can not be used for it.

A PDG (Packet Data Gateway) 317 allows access to the Internet 307 and the IMS 308 and provides the functionality of a router.

To collect communication connection charges, the AAA server is 316 with the PDG 317 coupled.

A WAG (WLAN Access Gateway) 318 The main object of the invention is to provide a communication link to the home UMTS communication network (not shown) of a user of a user equipment (not shown) if a communication connection from the user equipment to the UMTS communication network 311 and this is a visited UMTS communication network and not the user's home UMTS communication network.

The WAG points this out 318 a communication connection to the PDG of the home UMTS communication system (not shown).

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

The WAG 318 provides the functionality of a router.

In [2] the GPRS (General Packet Radio Service) communication standard is disclosed.

In [3] discloses a method of operating a radio communication network by means of which using a key, between a mobile device and a node of the communication network is exchanged, security problems in wireless data transmission, especially when switching between LAN communication networks and UMTS communication networks, solved can be.

In [4] is a method of handover a mobile between discloses different access networks, wherein a logical interface the communication between the mobile device and a physical Interface layer assigns IP addresses.

pamphlet [5] discloses a communication system in which a terminal with different Communication networks of the communication system is coupled and in particular by means of an interface communication services means the different communication networks can use.

In [6] discloses a method of data transmission, where a part of a dataset to be transmitted is transmitted by means of a secure interface and the rest Part of the transfer Data volume transmitted by means of a not specially secured interface is, for example by means of a WLAN.

In [7] are a method and architecture for a communication system discloses which is a vertical handoff, that is, a handover between different access networks, for example, a Provide communication link between a terminal and the Internet can, enable.

[8th] discloses a modification of a PDG having a GGSN element with functions a GGSN has.

Of the Invention is based on the problem, an efficient method for a Handover of a user device from a first access communication network to a second Provide access communication network.

The Task is through a communication system, a method of controlling a communication system, a network access device and a A method of controlling a network access device having the features solved according to the independent claims.

A communication system is provided having a first communication network, a second communication network, a third communication network, a user equipment and a network access device to which network access device is assigned a network layer address, the network access device being configured to provide access from the first communication network to the third Communication network and the access from the second communication network to the third communication network to enable; the communication system has a communication link between the Subscriber device and the third communication network by means of the first communication network and by means of the network access device, wherein in the data transmission by means of the first communication connection, the network layer address of the network access device is used; and the network access device has a control device that is configured to reduce the first communication connection and establish a second communication connection between the subscriber device and the third communication network by means of the second communication network and by means of the network access device, wherein in the data transmission by means of the second communication connection the network layer address of the network access device is used.

Further be a method for controlling a communication system, a A network access device and a method for controlling a network access device according to the above provided communication system described.

A The idea underlying the invention can be seen therein. the network access device provides access to a subscriber device to the third communication network both by means of the first as well as via the second communication network can and that when breaking down the first communication link and the construction of the second communication link, which is illustrative an (inter-system) handover of the user equipment from the first communication network to the second communication network, the network layer address the network access device does not change.

preferred Further developments of the invention will become apparent from the dependent claims. The others Embodiments of the invention, in connection with the provided Communication system are described, apply mutatis mutandis to the provided A method of controlling a communication system that provides Network access device and the method provided for controlling a network access device.

Preferably gets in the data transfer by means of the first communication connection and / or during the data transmission by means of the second communication connection, the network layer address the network access device by means of an APN (Access Point Name) specified.

The APNs used to specify the network layer address can, can be different, you have to only correspond to the same network layer address.

clear For example, the APNs are "mapped" to the same network layer address, for example the same IP protocol address.

It It is preferable that the first communication network is a WLAN communication network is called a WLAN, and the second communication network a UMTS communication network, the is called a UMTS communication system, is.

The first communication connection is thus preferably a WLAN communication link and the second communication connection is preferably a UMTS communication connection.

It it is further preferred that the subscriber device has a transmission device, which is set up, a message to the network access device to send, which has the request, the first communication link dismantle and set up the second communication link.

In an embodiment the message is sent by the first communication network transmit the network access device.

This is advantageous because in this case to implement the invention only a few changes using an existing UMTS communication network made on the network elements of the UMTS communication network Need to become. This makes the implementation easy and inexpensive.

In this embodiment is the WLAN communication connection until the complete Structure of the UMTS communication connection required.

In a second embodiment it is preferred that the message by means of the second communication network transmitted to the network access device becomes.

On This way, an inter-system handaver is still possible if the wireless communication connection is already interrupted, for example because of the supply area of the WLAN was left. This is an advantage, because thus the WLAN communication connection as long as possible can be used and because an inter-system handover also at An unexpected demolition of the WLAN communication connection is possible.

Preferably the third communication network is the internet.

In this case, the network layer address of the network access device is one IP address of the network access device.

It it is preferred that the network access device comprises a WLAN network access device, which has the function of a PDG of the WLAN communication network, a UMTS network access device, which has the function of a GGSN of the UMTS communication network, and has a memory on which memory the WLAN network access device and access the UMTS network access device.

clear Thus, the two network elements PDG and GGSN are in one element united.

The is particularly in an inter-system handover between the WLAN communication network and the UMTS communication network advantageous because no signaling during the inter-system handover between a PDG and a GGSN is required.

Further the access point of the user equipment to the Internet remains before and after identical to the inter-system handover, which is why after the inter-system handover no new route needs to be created on the internet.

embodiments The invention is illustrated in the figures and will be discussed below explained in more detail.

1 shows a UMTS communication system for providing packet-switched services;

2 shows a communication system with a WLAN access network;

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

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

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

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

7 shows an arrangement of latches according to an embodiment of the invention.

8th shows an arrangement of latches according to an 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 described above with reference to FIG 3 is explained.

A UMTS communication system 401 has base stations 402 . 403 by means of an RNC 404 with a SGSN 405 coupled, an IMS 406 , an HLR 407 , an AAA server 409 and a WAG 408 , respectively, with reference to 1 and 3 described functionality.

A wireless communication system 410 has access points 413 . 414 and one using one of the access points 413 . 414 with an access router 416 coupled subscriber device 415 , respectively, with reference to 2 and 3 described functionality.

Unlike the related to 3 explained network architecture has the UMTS communication network 401 instead of a GGSN and a PDG a PDG / GGSN 411 on.

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

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

The mobile subscriber device 415 is equipped with a UMTS transmitter and a UMTS receiver and with a WLAN transmitter and WLAN receiver, that is, the mobile user equipment 415 both with the UMTS communication system 401 as well as with the WLAN 410 can communicate.

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

In the following it is assumed that an active packet-switched communication connection between the subscriber device 415 and a (further) communication terminal (not shown) by means of the WLAN 410 consists.

The communication terminal can be like the subscriber device 415 a mobile subscriber device, or it is a stationary device such as a PC (personal computer).

Furthermore, it is assumed below that the communication terminal is part of the Internet 412 is.

This is for however, the invention is not required.

in the Below, a handover is always understood to mean an inter-system handover.

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

The message flow shown occurs between the following network elements: a subscriber device 501 , an access router 502 , a base station 503 , a WAG 504 , an RNC 505 , a SGSN 506 , a PDG / GGSN 507 , an AAA server 508 , an HLR 509 and the internet 510 ,

These network elements are described with reference to FIG 4 In particular, each of the network elements is part of a WLAN access network, a UMTS communication network or a WLAN / 3G interworking network.

In 5 actions to be performed are represented by rectangles. Transmissions of messages are represented by an arrow. Double arrows indicate a combination of messages and actions.

News, Actions and network elements that are part of the Wi-Fi access network or the WLAN / 3G interworking network, or elements Wi-Fi access network or the Wi-Fi / 3G interworking network accomplished or transferred are shown in dashed lines.

News, Actions and network elements that are part of the UMTS communication system are executed or transmitted by means of elements of the UMTS communication system are shown in solid lines.

In step 511 determines the user of the user equipment 501 which radio technologies are to be activated in his terminal.

It It is assumed that the user determines that both the UMTS transmitter and the UMTS receiver as well as the WLAN transmitter and the wireless receiver should be activated.

Furthermore, the user determines how the subscriber device 501 in the case of a handover behaves.

• 1. Ein Inter-System-Handover wird nie durchgeführt;
• 2. Ein Inter-System-Handover wird vom Benutzer manuell angeordnet, wobei der Benutzer von seinem Teilnehmergerät benachrichtigt wird, wenn ein Inter-System-Handover möglich ist;
• 3. Ein Inter-System-Handover wird von dem Teilnehmergerät 501 selbständig initiiert, wobei der Benutzer von dem Teilnehmergerät 501 benachrichtigt wird, wenn ein Inter-System-Handover durchgeführt wird.

The user selects from the following three options:

• 1. An inter-system handover is never performed;
• 2. An inter-system handover is manually arranged by the user, whereby the user is notified by his user equipment if an inter-system handover is possible;
• 3. An inter-system handover is performed by the user equipment 501 independently initiated, the user of the user equipment 501 is notified when an inter-system handover is performed.

It is assumed below that the user in step 511 the option 2 or 3 chooses.

The subscriber device 501 provides appropriate means so that the aforementioned options can be performed by the user to perform the respective notifications required and to implement the chosen option.

As mentioned, it is believed that in step 512 an active (communication) connection via the WLAN access network to a communication terminal (not shown) that is part of the Internet 510 is, exists.

In particular, it is assumed that a communication connection setup has taken place and that the user equipment 501 by means of the AAA server 508 authenticated and authorized for the existing communication connection.

In the event that the subscriber device 501 located outside the UMTS coverage area, or that the subscriber unit 501 is not yet registered in the packet-switched area of the UMTS communication system, that is, that no GPRS Attach (General Packet Radio Service Attach) has been executed, the process goes to step 513 continued.

In the event that the subscriber device 501 If a GPRS attach has already been executed before establishing the communication connection, the procedure in step 517 continued.

In step 513 the user moves into a UMTS coverage area. This means that the subscriber device 501 receives the provided according to the UMTS standard pilot channel.

In step 514 reads the subscriber device 501 by means of the base station 503 from the RNC 505 sent system information.

In step 515 represents the subscriber device 501 using the system information determines whether the UMTS communication network, which is the base station 503 comprising, the home network of the subscriber device 501 is.

If this is the case, as will be assumed below, the subscriber device will hit 501 the decision to subscribe to the UMTS communications network.

The Log into the packet-switched part of the UMTS communication network is called a GPRS attach.

In step 516 initiates the subscriber device 501 the procedure for a GPRS attach and sends a message with an identification of the user equipment 501 to the SGSN 506 ,

If this identification is the SGSN 506 is not known, becomes the subscriber device 501 authenticated.

It is also possible that the subscriber device 501 simultaneously logged into the circuit-switched part of the UMTS communication network.

In step 517 leads the subscriber device 501 Measurements on the air interface of the WLAN and the UMTS communication network. This is optional.

The UE Measures, for example, the reception field strengths of the WLAN and the UMTS communication network and the data rate of the existing WLAN communication link.

Preferably, the subscriber device measures 501 the reception field strength and the average data rate of the existing WLAN communication connection at regular intervals.

If a predeterminable limit is exceeded, the process goes to step 518 continued and initiated a handover.

The Border is chosen that data transfer by means of the WLAN at or shortly after falling below the limit still possible is. Otherwise, could the handover will not be initiated.

In step 518 If the user chooses the second option, the user will be notified that an inter-system handover is now possible.

In addition, can the user as a decision aid the quality of the existing WLAN communication connection and the possible UMTS communication links displayed, for example, the reception field strengths of the WLAN and the UMTS communications network and the average data rate the existing WLAN communication connection.

If the user agrees to a handover, the process goes to step 519 continued.

If the user has selected the third option, then the subscriber device will run 501 automatically the step 519 out.

In step 519 decides the subscriber device 501 if there are several communication connections by means of the WLAN, which are provided for the handover, that is, which of them should be continued by means of the UMTS communication system, and sends a message to the PDG / GGSN by means of the WLAN transmitter 507 that signals the subscriber device 501 request a handover.

In The message includes an identification of the user from the point of view of the WLAN / 3G interworking network, which identification hereinafter referred to as WLAN ID, and one or more Identifications of for the handover provided WLAN communication links, that is communication links, which consist of the WLAN included.

The identification of a WLAN communication connection is the W-APN (WLAN Access Point Name) of the WLAN communication connection that the user or the user equipment 501 when setting up the WLAN communication connection.

The PDG / GGSN 507 checks if there is SGSN address of the subscriber device 501 that is the address of the SGSN 506 , the subscriber device 501 is assigned, that is, by means of which the subscriber device 501 Can establish communication links with the UMTS communication system has stored.

If this is the case, then the sequence with step 522 otherwise, the procedure goes to step 520 continued.

In step 520 sends the PDG / GGSN 507 a message to the HLR 509 that specifies the SGSN address of the user equipment 501 requests.

In This message includes the WLAN ID.

In step 521 looking for the HLR 509 under Ver using the WLAN ID according to the SGSN address of the user equipment 501 ,

If the HLR 509 does not find the SGSN address, the HLR converts 509 translates the WLAN ID into an International Mobile Subscriber Identity (IMSI) and searches for the SGSN address using the IMSI.

In addition, the PDP address for this IMSI is searched, which PDP address is the subscriber device 501 assigned.

Then the HLR sends 509 the SGSN address, the IMSI, the WLAN ID and the PDP address of the user equipment 501 to the PDG / GGSN 507 ,

The HLR 509 has a table by means of which, using the WLAN ID, the IMSI of the user equipment 501 can be determined.

The steps 522 to 532 are executed once for each WLAN communication connection to be continued by means of a UMTS communication connection of the UMTS communication network.

With The WLAN communication connection is always one of the following continue using UMTS WLAN communication connections meant with UMTS communication connection to be established below is always the UMTS communication connection meant to continue the WLAN communication connection is used.

In step 522 The PDG / GGSN 507, using the type of WLAN communication connection, determines the appropriate PDP (Packet Data Protocol) type for the UMTS communication link to be established. The PDP type of a communication connection specifies the protocol to be used for a communication service used by the communication connection, for example, the Internet Protocol is used in the PDP type "IP".

In addition will from the W-APN a suitably modified APN (Access Point Name), that is one Designation for the UMTS communication connection to be established is determined.

This APN is determined to be the SGSN 506 using the APN the PDG / GGSN 507 can address that using the APN the same services can be requested as that used by the WLAN communication links and that the user equipment 501 using the APN can identify from which W-APN the APN has been determined.

Of the Modified APN is also referred to below as M-APN.

The PDG / GGSN 507 determines a PDP address that the subscriber device 501 is assigned: either the one from the HLR 509 received UMTS-specific PDP address or the WLAN address, that is, the address by means of the subscriber device 501 can be addressed via the WLAN communication connection.

Usually, the PDP address is an IP address. Preferably, the WLAN address is used as the PDP address. Otherwise, it is required that the PDG / GGSN 507 the PDP address is converted into the WLAN address for each data packet, or the WLAN address is converted into the PDP address, so that the communication connection to the communication terminal (not shown) remains in the Internet.

Subsequently, the PDG / GGSN sends 507 for the WLAN communication connection, which is to be continued by means of the UMTS communication network, a message to the SGSN 506 whose address is in the in step 521 from the HLR 509 sent and from the PDG / GGSN 507 received message was included.

With the message sent is the SGSN 506 signals that data packets for the subscriber device 501 available. The sending of these messages is independent of whether at this moment actually data packets by means of the WLAN access network to the user equipment 501 be sent or not.

In of the message include the values of the following parameters include: IMSI, PDP type, PDP address and M-APN. The parameter values are, as determined in the previous processing steps.

In step 523 confirms the SGSN 506 the PDG / GGSN 507 by means of a confirmation message that the SGSN 506 the subscriber device 501 signals that data packets are present. The PDG / GGSN 507 then provides a first buffer for the data packets provided by the user equipment 501 be sent to the communication terminal in the Internet by means of the UMTS communication link to be established in the future.

The data packets are buffered until the PDG / GGSN 507 Switches to the UMTS communication link (she hey step 535 ).

As mentioned above, the steps are 522 to 532 for each WLAN communication connection, which is to be continued by means of a UMTS communication connection of the UMTS communication network, once executed. In particular, a confirmation message is sent for each WLAN communication connection which is to be continued by means of the UMTS communication system.

In step 524 sends the SGSN 506 a message to the subscriber device 501 to request the construction of a PDP-context.

In This message contains values of the following parameters: Transaction Identifier (TI), which is a bidirectional data flow, for example in the context of a communication service, which uses the WLAN communication connection is carried out is specified, PDP type, PDP address and M-APN.

As mentioned above, the steps become 522 to 532 for each WLAN communication connection, which is to be continued by means of a UMTS communication connection of the UMTS communication network, once executed. In particular, for each WLAN communication connection to be continued by means of the UMTS communication system, the SGSN 506 sent this message once.

In step 525 selects the subscriber device 501 for the UMTS communication link to be established, the desired bit rate, the maximum delay time and the maximum bit error rate for both directions of the data transmission in the context of the UMTS communication connection to be established.

In this case, the subscriber device 501 take into account the equivalent values of the existing WLAN communication connections and special wishes of the user.

Subsequently, the subscriber device sends 501 for the WLAN communication connection, which is to be continued in the UMTS, a message with the request for the establishment of a PDP-context to the SGSN 506 ,

In This message contains values of the following parameters: TI, NSAPI (Network Layer Service Access Point Identifier), which uses the Service access point of the network layer specifies the PDP context PDP Type, PDP Address, M-APN, PDP Configuration Options specifying additional PDP options and QoS (Quality of Service) Requested, which specifies the required communication quality, For example, the bit rates, the maximum delay times and the maximum Bit error rates, each for both directions of data transmission as part of the UMTS communication connection to be established.

In this case, the M-APN selected as the M-APN is that contained in the message that was created in step 524 from the subscriber device 501 was received.

In step 526 decides the SGSN 506 whether by means of in step 525 received message requested PDP-context should be established or not.

The SGSN checks for this 506 whether it can provide the desired QoS parameter values and whether the user is enabled, ie authorized, for these QoS parameter values.

If necessary corrected, that is, changed, the SGSN 506 the values or rejects the structure of the PDP-context.

The corrected QoS parameters are referred to as QoS-Negotiated.

Subsequently, using the method described in step 525 message received M-APN the PDG / GGSN 507 informed by means of a message about the PDP-context to be established.

As mentioned above, the steps become 522 to 532 for each WLAN communication connection, which is to be continued by means of a UMTS communication connection of the UMTS communication network, once executed. In particular, for each WLAN communication connection which is to be continued by means of the UMTS communication system, a message with information about the PDP context to be set up is sent to the PDG / GGSN 507 Posted.

The message contains values of the following parameters: TEID (Tunnel Endpoint Identifier), which specifies an end point in the UMTS communication network, PDP type, PDP address, M-APN, QoS-Negotiated, NSAPI, MSISDN, that is the telephone number , Charging Characteristics, which specifies the type of communication connection charges, Selection Mode, which specifies how the Charging Characteristics parameter was selected, Trace Reference, Trace Type, and Trigger Id, which provide three parameter values for creating trace records, specifying which way data will travel through the communication system, OMC Identity (Identification of the Operation and Maintenance Center) and PDP Configuration Options.

In step 527 checks the PDG / GGSN 507 whether the desired QoS parameters are compatible with the PDP-context to be established.

If this is the case, it creates a new entry in the PDP context table and determines a new charging ID for tariffing, that is, an identifier that is used for cost accounting. It then sends a message to the SGSN 506 with the parameters PDP-Address, PDP-Configuration-Options, QoS-Negotiated, Charging-Id and Cause. The value of the Cause parameter indicates whether the PDP context to be established has been established or not. In the event that the PDP context to be established has not been established, the value of the Cause parameter indicates the reason why it was not established.

Otherwise the PDP-context is not established.

In step 528 correct the SGSN 506 optionally, the QoS parameter values and initiates the establishment of the air interface by sending a message to the RNC 505 sends.

At the procedure for establishment of air interface are out of SGSN 506 the RNC 505 and the subscriber device 501 involved. This procedure is designed as described in [2] (section: RAB Assignment Procedure).

As mentioned above, the steps are 522 to 532 for each WLAN communication connection, which is to be continued by means of a UMTS communication connection of the UMTS communication network, once executed. In particular, for each WLAN communication connection which is continued by means of the UMTS communication system, the procedure for establishing the air interface is carried out.

In step 529 after the air interface is established, which may be in step 528 corrected QoS parameter values to the PDG / GGSN 507 notified by means of a change notification message.

Because steps 522 to 532 for each WLAN communication connection which is to be continued by means of a UMTS communication connection of the UMTS communication network are executed once, in particular for each WLAN communication connection, which is continued by means of the UMTS communication system, a change notification message is sent.

In step 530 becomes the change notification from the PDG / GGSN 507 to the SGSN 506 confirmed by an appropriate message.

In step 531 adds the SGSN 506 for the communication link to be established, the NSAPI and the GGSN address, that is the address of the PDG / GGSN 507 , to the PDP-context.

After building a PDP-context, the structure of the PDP-context becomes the user equipment 501 approved.

In step 532 checks the subscriber device 501 for each acknowledgment, the QoS parameter values given to the subscriber device 501 vividly spoken.

The exam can be done by the subscriber device automatically accomplished or the user can be asked if he is using these QoS parameter values.

If the QoS parameter values do not correspond to the predefinable conditions, for example because the user does not agree, the subscriber device transmits 501 a message that triggers the removal of the affected PDP-context.

In In this case, the WLAN communication link is still maintained and the process is for this WLAN communication connection completed.

If the QoS parameter values are accepted, the process goes to step 533 continued.

In step 533 sends the user equipment 501 by means of a WLAN communication connection a message to the PDG / GGSN 507 with which it announces the separation of the continued via UMTS communication links WLAN communication links.

The Message contains the WLAN-ID and the M-APN of all WLAN-communication connections, which by means of of the UMTS communication system continued become.

In addition, will a second buffer for the received by means of UMTS communication links from the communication terminal in the Internet User data set up.

These user data are buffered until the user equipment 501 the in step 535 sent message or until a timer expires, specifically for this action in the user equipment 501 since the end of the step 532 running.

After switching to UMTS in step 534 sends the user equipment 501 the user data in the uplink corresponding to the continuing WLAN communication connections only to the communication terminal in the Internet by means of the UMTS communication connections which continue the WLAN communication connections.

In step 535 allows the PDG / GGSN 507 after receiving the in step 533 sent message the transmission of user data from the user equipment 501 the continuing wireless communication links only by means of the WLAN communication links continuing UMTS communication links.

Data that has already been received using one of the UMTS communication links, and is now in the one in step 523 furnished first buffer are forwarded in chronological order to the communication terminal on the Internet.

If all WLAN communication connections are continued by means of UMTS communication connections, the PDG / GGSN sends 507 By means of each WLAN communication connection, a termination message to all units involved in the WLAN communication connection, that is the WAG 504 , the access router 502 , the AAA server 508 , the HLR 509 and the subscriber device 501 , by means of which message the separation of the WLAN communication connection is initiated.

All from the communication terminal on the Internet to the user equipment 501 transmitted data are only using the UMTS communication links to the subscriber device 501 transfer.

If at least one WLAN communication connection not by means of a UMTS communication connection is to be continued, but continue by means of the WLAN access network should, the WLAN communication connection remains continue to exist and it will be sent to everyone on this wireless communication link involved units sent a continuation message that the Termination of continued Wireless communication links signals, but not the degradation of the WLAN communication connection, which persists, signals.

Further lead in step 535 All units involved in the WLAN communication connection after receiving the termination message from the necessary measures to terminate the respective WLAN communication connection.

If transmit a continuation message was, is the wireless communication link of the involved Units not finished.

The subscriber device 501 processes the data already received via the UMTS communication link and in step 533 stored second caches, in the chronological order in which they were received.

The user is from the subscriber device 501 Notifies that an inter-system handover has occurred.

In the event that several WLAN communication connections of a user equipment 501 to pass on, that is, to continue to be, which are provided by means of different PDG / GGSN, the sequence described above is executed by each affected PDG / GGSN.

The PDG / GGSN can be distinguished by the W-APN.

The referring to 5 The illustrated embodiment is distinguished by comparison with the embodiment described below with reference to FIG 6 is explained, the required changes of the UMTS communication network compared to a typical UMTS communication network are very low.

6 shows a message flow diagram 600 according to an embodiment of the invention.

Analogous to that with respect to 5 described embodiment, the message flow shown takes place between the following network elements: A user device 601 , an access router 602 , a base station 603 , a WAG 604 , an RNC 605 , a SGSN 606 , a PDG / GGSN 607 , an AAA server 608 , an HLR 609 and the internet 610 ,

Analogous to that with respect to 5 described embodiment, these network elements according to with reference to 4 In particular, each of the network elements is part of a WLAN access network, a UMTS communication network or a WLAN / 3G interworking network.

Analogous to 5 be in 6 actions to be performed are represented by rectangles. about Messages of messages are indicated by an arrow. Double arrows indicate a combination of messages and actions.

News, Actions and network elements that are part of the Wi-Fi access network or the WLAN / 3G interworking network, or elements Wi-Fi access network or the Wi-Fi / 3G interworking network accomplished or transferred are shown in dashed lines.

News, Actions and network elements that are part of the UMTS communication system are executed or transmitted by elements of the UMTS communication system are shown in solid lines.

The following with reference to 6 described embodiment differs from that with reference to

5 described embodiment in that the handover of the subscriber device 501 by sending a message by means of the UMTS communication system instead of using the WLAN communication system.

One An essential advantage of the following embodiment is that in This handover procedure is still possible if the wireless communication connection is already interrupted, for example, because the user the wireless coverage area with the subscriber device has left.

Thereby can use the WLAN communication connection as long as possible and a handover is also an unexpected crash the WLAN communication connection possible.

The embodiment described below differs from that with reference to FIG 5 described embodiment further in that the steps 519 to 524 analogous steps are not required.

The embodiment described below can be applied when the subscriber device 601 the IP address of the PDG / GGSN 607 , by means of which the WLAN communication link to be transferred is provided, is known.

The steps 611 to 616 are analogous to those with respect to 5 described steps 511 to 516 ,

In step 617 leads the subscriber device 601 Optionally, after a GPRS attach has been performed, take measurements on the air interface of the WLAN communication system and the UMTS communication system.

For example, the subscriber device measures 601 the reception field strengths of the WLAN communication system and the UMTS communication system and the data rate of the existing WLAN communication connections.

Preferably, the subscriber device measures 601 at regular intervals the reception field strength and the average data rate of the WLAN communication links.

If a predefined limit is exceeded, then the handover with step 618 initiated. In contrast to that with respect to 5 described embodiment, the WLAN communication connection to set up the UMTS communication connection is not required.

In step 618 if the user gets the possibility 1 (see step 511 above), the notification that an inter-system handover is possible.

In addition, can the user as a decision aid the respective quality of the active, this means existing, wireless communication links and the possible UMTS communication links displayed, for example, the reception field strength of Signals of the WLAN access network and the UMTS communication network and the average data rate of existing WLAN communication links.

If the user agrees to a handover, the process goes to step 619 continued. If the user has the opportunity 3 has dialed, then leads the subscriber device 601 automatically the step 619 out.

In step 619 directs the subscriber device, after using the subscriber device 601 the decision was made to initiate a handover, a first buffer memory, which in the event that the existing WLAN communication links abort, stores the payload data to be sent until UMTS communication links are established.

Subsequently, the subscriber device decides 601 if there are several WLAN communication connections, for which WLAN communication connections a new UMTS communication connection is to be established by means of the UMTS communication network and selects the desired bit rates, the maximum Ver, for the UMTS communication connections to be established delay times and the maximum bit error rates for both data transmission directions of the UMTS communication link.

In this case, the subscriber device 601 take into account the equivalent values of the current WLAN communication connections and special wishes of the user.

Subsequently, the subscriber device sends 601 a message requesting the establishment of a PDP context for use for a communications service to the SGSN 606 ,

The message contains values of the following parameters: APN, TI, IP address of the currently used PDG / GGSN 607 , NSAPI, PDP Type, PDP Address, PDP Configuration Options and QoS Requested.

The APN chosen is the subscriber device 601 also selected for the WLAN communication connection, which is to be continued by means of the PDP contexts to be set up, the so-called W-APN. If several communication connections are to be continued by means of the UMTS communication network, the above message is sent once to the SGSN for each WLAN communication connection 606 Posted.

In step 620 decides the SGSN 606 for each in step 619 transmitted message, whether the PDP-context should be established or not. The SGSN checks for this 606 whether it can provide the desired QoS parameters and whether the user is authorized, that is, enabled, for these QoP parameters and for the requested communication service provided by means of the requested PDP contexts.

If the SGSN 606 Required information is not known, it asks with step 621 this information from the HLR 609 at.

Otherwise, the process goes to step 623 continued.

In step 621 demands the SGSN 606 the missing information about the user of the user equipment 601 from the HLR 609 at.

The missing information can for example, information about the authorization to use the requested communication service and the requested QoS parameter. For every UMTS communication connection to be established If necessary, the missing information is requested.

In step 622 sends the HLR 609 the requested information to the SGSN 606 ,

In step 623 if the SGSN 609 the required information is known, the SGSN corrects 609 if necessary, the QoS parameters or rejects the structure of the PDP-context. The corrected QoS parameters are referred to as QoS-Negotiated. Subsequently, the SGSN informs 609 using the subscriber device 601 transmitted IP address the PDG / GGSN 607 about the PDP context to be established by means of a PDG / GGSN 607 sent message.

In the message contains values of the following parameters: PDP-Type, PDP-Address, APN, QoS-Negotiated, NSAPI, MSISDN, Selection-Mode, Charging Characteristics, Trace Reference, Trace Type, Trigger ID, OMC Identity, and PDP Configuration Options.

For each UMTS communication connection to be established, such a message is sent to the PDG / GGSN 607 Posted.

In step 624 checks the PDG / GGSN 607 for each received, in step 623 sent message, whether the given QoS parameter values are compatible with the corresponding PDP-context to be built.

If so, the PDG generates / GGSN 607 a new entry in his PDP context table and determines a new Charging ID for tariffing. It then sends a message to the SGSN for each WLAN communication connection to be continued by means of the UMTS communication network 606 with values of the parameters PDP-Address, PDP-Configuration-Options, QoS-Negotiated, Charging-Id, Cause.

Otherwise the PDP-context is not established.

If at least one PDP-context is established, the PDG / GGSN sets 607 two latches, a second buffer which, in the event that the corresponding WLAN communication connection aborts, to the subscriber device 601 to be sent user data stores until the corresponding, that is, the WLAN communication connection continuing, UMTS communication connection is established, and a third buffer that the from the user equipment 601 stores data received via the UMTS communication network until the WLAN communication connection has been terminated.

In step 625 correct the SGSN 606 optionally, the QoS parameter values and direct the Establish the air interface by sending a message to the RNC for each WLAN communication connection to be continued via the UMTS communication network 605 sends.

At the procedure for establishment of air interface are out of SGSN 606 the RNC 605 and the subscriber device 601 involved. This procedure is designed as described in [2] (Section: RAB Assignment Procedure).

These Procedure is for any WLAN communication connection using the UMTS communication network continued should be done once.

In step 626 after the air interface has been established, which may be in step 625 corrected QoS parameter values to the PDG / GGSN 607 notified by means of a change notification message. For each WLAN communication connection that is to be continued in UMTS, a change message is sent.

In step 627 becomes the change notification from the PDG / GGSN 607 the SGSN 606 confirmed by an appropriate message.

In step 628 adds the SGSN 606 for the communication link to be established, the NSAPI and the GGSN address, that is the address of the PDG / GGSN 607 , to the PDP-context.

After building a PDP-context, the structure of the PDP-context becomes the user equipment 601 approved.

In step 629 checks the subscriber device 601 for each acknowledgment, the QoS parameter values given to the subscriber device 601 vividly spoken.

If the QoS parameter values do not correspond to predefinable conditions, for example because the user does not agree, the user equipment transmits 601 a message that triggers the removal of the corresponding PDP-context.

In In this case, the WLAN communication link is still maintained and the process is for this WLAN communication connection completed.

If the QoS parameter values are accepted for at least one PDP-context, the process goes to step 630 continued.

Otherwise No handover is performed and the WLAN communication connection remains.

In step 630 sends the user equipment 601 in the event that all for the subscriber device 601 by means of the WLAN access network provided by the UMTS communication network to be continued, by means of a UMTS communication connection, a first announcement message to the PDG / GGSN 607 with which it announces the separation of the WLAN communication connections.

The first announcement message contains The following parameter values: The WLAN ID and the M-APN of all WLAN communication connections, the be continued by means of the UMTS communication network should.

In addition, will a fourth cache for the means of UMTS communication connections from the communication terminal in the Internet received user data set up.

If at least one WLAN communication connection is to remain, a second announcement message is sent to the PDG / GGSN 607 by which is communicated which PDP contexts of the user equipment 601 were accepted, and which were rejected.

After switching to UMTS in step 631 sends the user equipment 601 the user data corresponding to the continuing WLAN communication connections only to the communication terminal in the Internet by means of the UMTS communication connections which continue the WLAN communication connections.

The user receives from the user equipment 601 the notification that an inter-system handover has taken place.

In step 632 allows the PDG / GGSN after receiving the in step 630 sent message the transmission of user data from the user equipment 601 the continuing wireless communication links only by means of the WLAN communication links continuing UMTS communication links.

Data already using one of the UMTS communication links from the subscriber device 601 have been transferred and now in the step 624 configured third caches are forwarded in the chronological order in which they were transmitted by the user equipment to the communication terminal on the Internet.

If user data in the second buffer for the subscriber device 601 who are these also in the chronological order in which they were stored in the cache to the user equipment 601 forwarded.

Subsequently, the PDG sends / GGSN 607 By means of a WLAN communication connection to be separated, a termination message to all units involved in the WLAN communication connection, these are the WAG 604 , the access router 602 , the AAA server 608 , the HLR 609 and the subscriber device 601 , by means of which message the separation of the WLAN communication connection is initiated.

Data that is transmitted in the context of a communication service whose data transmission was performed before the separation by means of the separate WLAN communication connection, only by means of the WLAN communication connection continuing UMTS communication connection to the subscriber device 601 transfer.

If the PDG / GGSN 607 has received the second announcement message, remain the wireless communication links that are to remain persist, and it is sent to all participating in the ongoing wireless communication links units a continuation message that signals the termination of the continued wireless communication links, but not to reduce all WLAN communication connections leads.

Further lead in step 632 All units involved in the continued WLAN communication connections after receiving the termination message from the necessary measures to terminate the continued wireless communication link.

The subscriber device 601 after disconnecting the WLAN communication connection, the data which has already been received by means of the UMTS communication connection and which is now in the fourth buffer is processed in the chronological order in which it was received.

If useful data for the communication terminal on the Internet in the first cache, these are now in the chronological order in which they are in the cache were sent to the communication terminal on the Internet.

If transmit a continuation message was, is the wireless communication link of the involved Units not finished.

In the event that several WLAN communication connections of a user equipment 601 to pass on, that is, to continue to be, which are provided by means of different PDG / GGSN, the sequence described above is executed by each affected PDG / GGSN.

The PDG / GGSN can be distinguished by the W-APN.

For a better understanding, the arrangement of the temporary storage used in the reference to 5 described embodiment and the arrangement of the latches used in with reference to 6 described embodiment explained.

7 shows an arrangement of latches 700 according to an embodiment of the invention.

The buffers are in a subscriber device 701 that the subscriber device 501 corresponds, as well as a PDG / GGSN 702 , the PDG / GGSN 507 corresponds, arranged.

In the PDG / GGSN 702 is a first cache 703 who in the explanation of 5 corresponds to said first cache, arranged.

In the subscriber device 701 is a second cache 704 who in the explanation of 5 corresponds to said second temporary storage arranged.

As above with respect to 5 explained, stores the first cache 703 the data provided by the subscriber device 701 be sent by means of an already established UMTS communication connection to the communication terminal in the Internet.

These Data is forwarded only if the corresponding WLAN communication connection, this means the WLAN communication connection, which continues the UMTS communication connection degraded is.

This allows the simultaneous existence of the UMTS communication connection and the WLAN communication connection.

As can be seen, the uplink data stream by means of the UMTS communication link is not from the PDG / GGSN 702 is passed through but cached, it is not required that the PDG / GGSN 702 at the same time forwarding two data streams to the Internet, for which the double An number of network layer instances would be required.

clear spoken is the first cache so under the Network layer, in this embodiment of the Internet Protocol layer.

The second cache 704 has the function analogous to the first buffer. As above with respect to 5 explained, stores the second cache 704 the data provided by the subscriber device 701 by means of the already established UMTS communication connection received data.

These Data is not processed until the corresponding WLAN communication connection, this means the WLAN communication connection, which continues the UMTS communication connection, degraded is.

Analogous to the first buffer 703 this allows the parallel existence of the UMTS communication connection and the WLAN communication connection.

The first cache 703 and the second cache 704 can be considered as receive buffers because the first cache 703 Data stores by the PDG / GGSN 704 were received and the second cache 704 Data stores by the subscriber unit 701 were received.

8th shows an arrangement of latches 800 according to an embodiment of the invention.

The buffers are in a subscriber device 801 that the subscriber device 601 corresponds, as well as a PDG / GGSN 802 , the PDG / GGSN 607 corresponds, arranged.

In the PDG / GGSN 802 is a third cache 803 who in the explanation of 6 as well as a second buffer 803 who in the explanation of 6 corresponds to said second temporary storage arranged.

In the subscriber device 801 is a fourth cache 804 who in the explanation of 6 as well as a first buffer 805 who in the explanation of 6 corresponds to said first cache, arranged.

The third cache 803 has one related to that 7 explained first cache 703 analogue functionality.

The fourth cache 804 has one related to that 7 explained second cache 704 analogue functionality.

The third cache 803 and the fourth cache 804 will therefore not be explained further below.

As above with respect to 6 explained, stores the first cache 805 the data provided by the subscriber device 801 by means of an already degraded WLAN communication connection in the uplink to be sent. These data are sent as explained with the appropriate UMTS communication link when it is established.

As above with respect to 6 explained, stores the second cache 806 the data sent to the subscriber device 801 to be sent by means of an already degraded WLAN communication connection in the downlink. These data are sent as explained with the appropriate UMTS communication link when it is established.

The first cache 805 and the second cache 806 clearly illustrate that the degraded WLAN communication links are used as long as possible and also in the sudden termination of the WLAN communication links, for example, arises because the user of the user equipment 801 a WLAN cell leaves, no data is lost.

In This document cites the following publications:

• [1] 3GPP TSG-SA, TR 22.934, feasibility study to 3GPP system to Wireless Local Area Network Interworking
• [2] 3GPP TSG-SA, TS 23.060, General Packet Radio Service (GPRS); Service description; Stage 2
• [3] US 2003/0031151 A1
• [4] AU 200135071 A1
• [5] WO 02/15598
• [6] EP 1 284 568 A1
• [7] Hyosoon Park, Sunghoon Yoon, Taehyoun Kim, Jungshin Park, Misun Do, Jaiyong Lee "Vertical Handoff Procedure and Algorithm between IEEE802.11 WLAN and CDMA Cellular Network ", Lecture Notes in Computer Science (LNCS), No. 2524, pp. 103-112, 2003
• [8] 3GPP Change Request, 23.234 CR 26

100

UMTS communication system

101

UE

102

base station

103

UMTS radio network

104

RNC

105

SGSN

106

GGSN

107

Internet

108

IMS

109

HLR

200

communication system

201

UE

202

Access Points

203

Wi-Fi network

204

Access Points

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 communication system

312

Wireless communication system

313 314

Access Points

315

UE

316

AAA server

317

PDG

318

WAG

400

communication system

401

UMTS communication system

402 403

base station

404

RNC

405

SGSN

406

IMS

407

HLR

408

WAG

409

AAA server

410

Wireless communication system

411

GGSN / PDG

412

Internet

413 414

Access Points

415

UE

416

Access router

500

Message flow diagram

501

UE

502

Access router

503

base station

504

WAG

505

RNC

506

SGSN

507

PDG / GGSN

508

AAA server

509

HLR

510

Internet

511-535

processing steps

600

Message flow diagram

601

UE

602

Access router

603

base station

604

WAG

605

RNC

606

SGSN

607

PDG / GGSN

608

AAA server

609

HLR

610

Internet

611-632

processing steps

700

Buffer storage arrangement

701

UE

702

PDG / GGSN

703

first cache

704

second cache

800

Buffer storage arrangement

801

UE

802

PDG / GGSN

803

third cache

804

fourth cache

805

first cache

806

second cache

Claims (11)

Communication system, which is a first communications network, a second communication network, a third communication network, a subscriber device and a network access device, which network access device a network layer address is assigned, wherein - the network access device is set up, the access from the first communication network to the third communication network and access from the second Communication network to the third communication network to enable; - the communication system a communication connection between the user equipment and the third Communication network by means of the first communication network and by means of the network access device, wherein in the data transmission the network layer address by means of the first communication connection the network access device is used; and - the network access device a control device that is configured, the first Reduce communication link and a second communication link between the subscriber device and the third communication network by means of the second communication network and by means of the network access device, wherein the data transfer by means of the second communication connection, the network layer address of Network access device is used. Communication system according to claim 1, wherein in the data transfer by means of the first communication connection and / or during the data transmission by means of the second communication connection, the network layer address the network access device specified by means of an access point name becomes. A communication system according to claim 1 or 2, wherein the subscriber device a transmission device which is set up, a message to the network access device to send, which has the request, the first communication link dismantle and set up the second communication link. Communication system according to claim 3, wherein the message transmitted by the first communication network to the network access device becomes. Communication system according to claim 3, wherein the message transmitted by the second communication network to the network access device becomes. Communication system according to one of claims 1 to 5, wherein the third communication network is the Internet. Communication system according to one of claims 1 to 6, wherein the first communication network is a WLAN communication network and the second communication network, a UMTS communication network is. Communication system according to claim 7, wherein the network access device a WLAN network access device having the function of a PDG of the WLAN communication network a UMTS network access device that performs the function of a GGSN of the UMTS communication network, and a memory on which memory the WLAN network access device and the UMTS network access device access. Method for controlling a communication system, which communication system a first communication network, a second communication network, a third communication network, a subscriber device and a network access device, which network access device a network layer address is assigned and which network access device the access from the first communication network to the third Communication network and access from the second communication network to the third communication network, according to the method - in the data transfer by means of a first communication link between the UE and the third communication network via the first communication network and by means of the network access device, the network layer address the network access device is used; - the network access device breaks down the first communication connection; - the network access device a second communication connection between the user equipment and the third communication network by means of the second communication network and by means of the network access device; and - in the data transfer by means of the second communication connection, the network layer address the network access device is used. Network access device of a communication system, a first communication network, a second communication network, a third communication network, and a subscriber device, which network access device is a network layer address is assigned, where - the Network access device is set up, the access from the first Communication network to the third communication network and the access from the second communication network to the third Enable communication network; - the network access device a control device that is configured, a first Break down communication link, the first communication link between the subscriber device and the third communication network via the first communication network and by means of the network access device and wherein at the data transfer the network layer address by means of the first communication connection the network access device is used, and which control device is further set up a second communication link between the subscriber device and the third communication network via the second communication network and by means of the network access device, wherein the data transfer by means of the second communication connection, the network layer address the network access device is used. A method for controlling a network access device of a communication system comprising a first communication network, a second communication network, a third communication network, and a user equipment, which network access device is associated with a network layer address, and which network access device provides access from the first communication network to the third communication network and access from the second comm and wherein according to the method - the network access device degrades a first communication connection, wherein the first communication connection between the subscriber device and the third communication network by means of the first communication network and by means of the network access device and wherein in the data transmission by means of the first communication connection, the network layer Address of the network access device is used; and - the network access device establishes a second communication connection between the subscriber device and the third communication network by means of the second communication network and by means of the network access device, wherein in the data transmission by means of the second communication connection the network layer address of the network access device is used.