WO2015062643A1

WO2015062643A1 - Keeping user equipment in a state attached to a cellular communication network during offloading of cellular data to another communication network

Info

Publication number: WO2015062643A1
Application number: PCT/EP2013/072666
Authority: WO
Inventors: Wolfgang Hahn; Gyorgy Tamas Wolfner
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2013-10-30
Filing date: 2013-10-30
Publication date: 2015-05-07

Abstract

The present invention provides apparatuses, methods, systems, computer programs, computer program products and computer-readable media usable for keeping user equipment in a state attached to a cellular communication system during offloading of cellular data to another communication system. The method includes preparing, at a user equipment, an indication that a data connection of the user equipment over a cellular communication system is to be maintained, and transmitting the indication to an access point of a non-cellular communication system.

Description

DESCRIPTION

TITLE

Keeping user equipment in a state attached to a cellular communication network during offloading of cellular data to another communication network

Field of the invention

The present invention relates to apparatuses, methods, systems, computer programs, computer program products and computer-readable media usable for keeping user equipment in a state attached to a cellular communication system during offloading of cellular data to another communication system.

Background of the invention

In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), DSL (Digital Subscriber Line), or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) like the (UMTS) and fourth generation (4G) communication networks based e.g. on LTE , enhanced communication networks like LTE-A, cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolution (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN or Wi- Fi), Bluetooth or Worldwide Interoperability for Microwave Access (WiMAX), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project

(3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WiMAX Forum and the like are working on standards for telecommunication network and access environments.

Generally, for properly establishing and handling a communication connection between terminal devices such as a user device or user equipment (UE) and another communication network element or user device, a database, a server, host etc., one or more intermediate network elements such as communication network control elements, such as access points, base stations, control nodes, support nodes or service nodes are involved which may belong to different communication networks. Basically, a cellular communication network is typically divided into several cells controlled by a communication network control element like a base station (BS), evolved NodeB (eNB), and the like, which can communicate with one or more UEs e.g. via an air interface. In case a UE connected to one serving BS leaves the coverage area (i.e. cell) of the BS and enters a coverage area (cell) of another (neighboring) BS, a communication connection switching of the UE, also referred to as handover, is conducted in the communication network for changing the connection of the UE to the new BS. A handover may be also conducted in case of other reasons, such as traffic offload, quality improvement, etc.

Due to the increasing usage of communication networks, and in particular, wireless communication networks and the increasing use of smart phones, tablets etc., operators are faced with increasing bandwidth demand in mobile networks. A solution to increase the capacity is the deployment and use Wi-Fi Access Points (APs) as a cost efficient alternative. The offloading of cellular data traffic to Wi-Fi networks is currently of very high interest to mobile network operators. A crucial point is to enable efficient and effective WLAN - 3GPP network load balancing in order to increase system capacity, system utilization and improve the user experience.

Due to such interests, there has been introduced a specific new study item in 3GPP Radio Access Network specification working group 2 (RAN WG2) to investigate better mechanisms for interworking between WLAN - 3GPP communication systems.

In this regard, it is aimed at providing an effective and efficient mechanism to steer the devices for network controlled load balancing between the access technologies (based on the current load situation and associated expected user experience). 3GPP RAN WG2 has started to define improved and more predictable network control for steering the UE between cellular and Wi-Fi access. Basically two solutions have been discussed so far: in one solution the UE is provided with assistance information from the base station and decides based on this whether to select either cellular or Wi-Fi access. In the other solution the UE shall send the collected information about the APs it sees to the BS and the BS instructs then the UE with traffic steering (TS) commands.

In both cases, connectivity of the UE with the cellular network is assumed. This means that it is assumed that the UE is always attached to the 3GPP network (in idle or active mode). If the UE is at least in IDLE mode in the 3GPP network, it would be able to read for example the broadcasted traffic steering information in the system information block SIB send by the BS. The assumption that UE has connectivity to the cellular network even if WLAN is used is essential to enable networks to steer UEs back from WLAN to cellular access, e.g. when an operator prefers UEs to come back to their cellular access after an overloaded situation disappeared instead of using a WLAN of a roaming partner.

According to the 3GPP specifications (see 3GPP TS 23.402) there are a number of ways how a UE can use a WLAN to get services. One method is that it handovers one or more PDN (Packet Data Network) connections with IP (Internet Protocol) address preservations. In this case the UE attaches to the WLAN and then establishes the PDN connection(s) with handover indication. The network from this indication knows that the existing connection should be moved over WLAN and the resources to the PDN connection in the 3GPP access are released. The problem is that in case of LTE no UE can stay in attached state without a PDN connection over LTE. Thus if the UE moves all of the PDN connections to WLAN then it is automatically detached from LTE. In this regard, it is noted that it is quite typical that a UE has only a single PDN connection. Thus, when it starts using WLAN and moves this PDN connection to WLAN, then it is detached from the LTE network.

Currently, there are two ways of solving the above problem. One way is to enable UEs to stay in connected mode without a PDN connection. This, however, would mean a principle change in the LTE system, and thus, it is hardly possible to change the specification to support such a state.

Another way is using flow based mobility (aka IFOM (IP flow mobility)). In this case, both the LTE network and WLAN can be used simultaneously for data transfer for a PDN connection. Of course this means that the UE has a PDN connection over LTE even if it may not use it actually. Although 3GPP specifications would support this feature, due to its complexity, it is not expected that networks and UEs will support it in the near future.

Summary of the Invention

It is therefore an object of the present invention to overcome the above mentioned problems and to provide apparatuses, methods, systems, computer programs, computer program products and computer-readable media usable for keeping user equipment in a state attached to a cellular communication system during offloading of cellular data to another communication system.

According to an aspect of the present invention there is provided a method comprising: preparing, at a user equipment, an indication that a data connection of the user equipment over a cellular communication system is to be maintained, and transmitting the indication to an access point of a non-cellular communication system.

According to another aspect of the present invention there is provided a method comprising:

receiving, at a gateway, a request for creating a packet data connection of a user equipment over a non-cellular communication network, the request including an indication that a data connection of the user equipment over a cellular communication network, to which the user equipment is attached at the time of receiving the request, is to be maintained, establishing a data connection for the user equipment over the non-cellular communication network; and releasing bearers of the user equipment except for a bearer of the data connection of the user equipment over the cellular communication network.

receiving, at a user equipment, a trigger for initiating a handover from a non- cellular communication network to a cellular communication network, initiating a service request procedure for activating a bearer for a data connection of the user equipment over the cellular communication network, and transmitting a data packet over the bearer for the data connection of the user equipment over the cellular communication network.

receiving, at a gateway, a data packet from a user equipment over a bearer for a data connection of the user equipment over a cellular communication network, and initiating a handover of the user equipment to the cellular communication network.

receiving, at a user equipment, a trigger for a handover of a first data connection from a cellular communication network to a non-cellular communication network, initiating, by the user equipment, establishment of a second data connection of the user equipment over the cellular communication network, before performing the handover of the first data connection, performing handover of the first data connection to the non-cellular communication network, and maintaining the second data connection of the user equipment over the cellular communication network.

According to another aspect of the present invention there is provided an apparatus, comprising: at least one processor, and at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: preparing an indication that a data connection of a user equipment over a cellular communication system is to be maintained, and transmitting the indication to an access point of a non-cellular communication system. According to another aspect of the present invention there is provided an apparatus, comprising: at least one processor, and at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: receiving a request for creating a packet data connection of a user equipment over a non-cellular communication network, the request including an indication that a data connection of the user equipment over a cellular communication network, to which the user equipment is attached at the time of receiving the request, is to be maintained, establishing a data connection for the user equipment over the non-cellular communication network; and releasing bearers of the user equipment except for a bearer of the data connection of the user equipment over the cellular communication network.

According to another aspect of the present invention there is provided an apparatus, comprising: at least one processor, and at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: receiving a trigger for initiating a handover of a user equipment from a non-cellular communication network to a cellular communication network, initiating a service request procedure for activating a bearer for a data connection of the user equipment over the cellular communication network, and transmitting a data packet over the bearer for the data connection of the user equipment over the cellular communication network.

According to another aspect of the present invention there is provided an apparatus, comprising: at least one processor, and at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: receiving a data packet from a user equipment over a bearer for a data connection of the user equipment over a cellular communication network, and initiating a handover of the user equipment to the cellular communication network. According to another aspect of the present invention there is provided an apparatus, comprising: at least one processor, and at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: receiving a trigger for a handover of a first data connection of a user equipment from a cellular communication network to a non-cellular communication network, initiating establishment of a second data connection of the user equipment over the cellular communication network, before performing the handover of the first data connection, performing handover of the first data connection to the non-cellular communication network, and maintaining the second data connection of the user equipment over the cellular communication network.

According to another aspect of the present invention there is provided an apparatus, comprising: means for preparing an indication that a data connection of a user equipment over a cellular communication system is to be maintained, and means for transmitting the indication to an access point of a non-cellular communication system. According to another aspect of the present invention there is provided an apparatus, comprising: means for receiving a request for creating a packet data connection of a user equipment over a non-cellular communication network, the request including an indication that a data connection of the user equipment over a cellular communication network, to which the user equipment is attached at the time of receiving the request, is to be maintained, means for establishing a data connection for the user equipment over the non- cellular communication network; and means for releasing bearers of the user equipment except for a bearer of the data connection of the user equipment over the cellular communication network.

According to another aspect of the present invention there is provided an apparatus, comprising: means for receiving a trigger for initiating a handover of a user equipment from a non-cellular communication network to a cellular communication network, means for initiating a service request procedure for activating a bearer for a data connection of the user equipment over the cellular communication network, and means for transmitting a data packet over the bearer for the data connection of the user equipment over the cellular communication network.

According to another aspect of the present invention there is provided an apparatus, comprising: means for receiving a data packet from a user equipment over a bearer for a data connection of the user equipment over a cellular communication network, and means for initiating a handover of the user equipment to the cellular communication network. According to another aspect of the present invention there is provided an apparatus, comprising: means for receiving a trigger for a handover of a first data connection of a user equipment from a cellular communication network to a non-cellular communication network, means for initiating establishment of a second data connection of the user equipment over the cellular communication network, before performing the handover of the first data connection, means for performing handover of the first data connection to the non-cellular communication network, and means for maintaining the second data connection of the user equipment over the cellular communication network.

According to another aspect of the present invention there is provided a computer program product comprising code means adapted to produce steps of any of the methods as described above when loaded into the memory of a computer.

According to a still further aspect of the invention there is provided a computer program product as defined above, wherein the computer program product comprises a computer- readable medium on which the software code portions are stored.

According to a still further aspect of the invention there is provided a computer program product as defined above, wherein the program is directly loadable into an internal memory of the processing device.

Brief Description of the Drawings These and other objects, features, details and advantages will become more fully apparent from the following detailed description of aspects/embodiments of the present invention which is to be taken in conjunction with the appended drawings, in which:

Fig. 1 is a signaling diagram illustrating signaling involved in a handover from a cellular communication system to a non-cellular communication system according to example versions of the present invention; Fig. 2 is a flowchart illustrating an example of a method according to example versions of the present invention;

Fig. 3 is a diagram illustrating an example of an apparatus according to example versions of the present invention;

Fig. 4 is a flowchart illustrating another example of a method according to example versions of the present invention; Fig. 5 is a diagram illustrating another example of an apparatus according to example versions of the present invention;

Fig. 6 is a signaling diagram illustrating signaling involved in a handover from a non- cellular communication system to a cellular communication system according to example versions of the present invention ;

Fig. 7 is a flowchart illustrating another example of a method according to example versions of the present invention; Fig. 8 is a diagram illustrating another example of an apparatus according to example versions of the present invention;

Fig. 9 is a flowchart illustrating another example of a method according to example versions of the present invention;

Fig. 10 is a diagram illustrating another example of an apparatus according to

example versions of the present invention;

Fig. 1 1 is a flowchart illustrating another example of a method according to example versions of the present invention;

Fig. 12 is a diagram illustrating another example of an apparatus according to example versions of the present invention.

Detailed Description In the following, some example versions of the disclosure and embodiments of the present invention are described with reference to the drawings. For illustrating the present invention, the examples and embodiments will be described in connection with a cellular communication network based on a 3GPP based communication system, for example an LTE/LTE-A based system., and a wireless communication network such as, for example, WLAN. However, it is to be noted that the present invention is not limited to an application using such types of communication systems or communication networks, but is also applicable in other types of communication systems or communication networks and the like. The following examples versions and embodiments are to be understood only as illustrative examples. Although the specification may refer to "an", "one", or "some" example version(s) or embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same example version(s) or embodiment(s), or that the feature only applies to a single example version or embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such example versions and embodiments may also contain also features, structures, units, modules etc. that have not been specifically mentioned. The basic system architecture of a communication network where examples of embodiments of the invention are applicable may comprise a commonly known architecture of one or more communication systems comprising a wired or wireless access network subsystem and a core network. Such an architecture may comprise one or more communication network control elements, access network elements, radio access network elements, access service network gateways or base transceiver stations, such as a base station (BS), an access point or an eNB, which control a respective coverage area or cell and with which one or more communication elements or terminal devices such as a UE or another device having a similar function, such as a modem chipset, a chip, a module etc., which can also be part of a UE or attached as a separate element to a UE, or the like, are capable to communicate via one or more channels for transmitting several types of data. Furthermore, core network elements such as gateway network elements, policy and charging control network elements, mobility management entities, operation and maintenance elements, and the like may be comprised. The general functions and interconnections of the described elements, which also depend on the actual network type, are known to those skilled in the art and described in corresponding specifications, so that a detailed description thereof is omitted herein. However, it is to be noted that several additional network elements and signaling links may be employed for a communication to or from a communication element or terminal device like a UE and a communication network control element like a radio network controller, besides those described in detail herein below.

The communication network is also able to communicate with other networks, such as a public switched telephone network or the Internet. The communication network may also be able to support the usage of cloud services. It should be appreciated that BSs and/or eNBs or their functionalities may be implemented by using any node, host, server or access node etc. entity suitable for such a usage.

Furthermore, the described network elements and communication devices, such as terminal devices or user devices like UEs, communication network control elements of a cell, like a BS or an eNB, access network elements like APs and the like, as well as corresponding functions as described herein may be implemented by software, e.g. by a computer program product for a computer, and/or by hardware. In any case, for executing their respective functions, correspondingly used devices, nodes or network elements may comprise several means, modules, units, components, etc. (not shown) which are required for control, processing and/or communication/signaling functionality. Such means, modules, units and components may comprise, for example, one or more processors or processor units including one or more processing portions for executing instructions and/or programs and/or for processing data, storage or memory units or means for storing instructions, programs and/or data, for serving as a work area of the processor or processing portion and the like (e.g. ROM, RAM, EEPROM, and the like), input or interface means for inputting data and instructions by software (e.g. floppy disc, CD-ROM, EEPROM, and the like), a user interface for providing monitor and manipulation possibilities to a user (e.g. a screen, a keyboard and the like), other interface or means for establishing links and/or connections under the control of the processor unit or portion (e.g. wired and wireless interface means, radio interface means comprising e.g. an antenna unit or the like, means for forming a radio communication part etc.) and the like, wherein respective means forming an interface, such as a radio communication part, can be also located on a remote site (e.g. a radio head or a radio station etc.). It is to be noted that in the present specification processing portions should not be only considered to represent physical portions of one or more processors, but may also be considered as a logical division of the referred processing tasks performed by one or more processors.

According to some example versions of the disclosure, a mobility management processing is described where a user equipment is kept in a state attached to a cellular communication network during offloading of cellular data to another communication network.

According to some example versions of the disclosure, in order to solve the problem that a UE is detached when it handovers all of its PDN connections to WLAN, it is proposed to keep a "standby" PDN connection in case the UE traffic is handed over to WLAN, i.e. a default bearer in the cellular side instead of releasing the PDN connection and possibly detaching the UE.

Such a proposal does not involve an introduction of new states for the mobility or session management for the network or UE. It is just like a UE in IDLE state that does not use the PDN connection as long as it is using the Wi-Fi connection.

The "cost" of keeping the PDN connection in 3GPP side would require some additional storage space for state information in the gateways (GWs), and the mobility management entity (MME).

The implementation of the new proposed functions according to some example versions of the present invention can be UE based or network based or may need both enhancements in the UE and network, i.e. UE based with network support (at least with network support in the PGW (packet data network gateway)).

UE based implementation with network support In the following, an UE based implementation with network support for a handover from a

3GPP network to a non-3GPP network according to some example versions of the present invention will be described in detail.

According to such an implementation, the PDN connection is not completely removed from 3GPP side, but it is kept both in the UE and in the network in "idle state". The concept is that the default bearer of the last PDN connection of the UE is kept (not released either by the UE or by the network) over LTE after the handover to Wi-Fi, but it is not used for uplink or downlink data transmission.

When the UE initiates the handover to the Wi-Fi it indicates to the network (e.g. by means of new attach type or handover indicator) that the network should not release the PDN connection after HO as this is the only one the UE has to the 3GPP access side. This information is carried from the non-3GPP access network to the PGW. (The PGW is not aware if this is the last PDN connection of the UE as the UE can have several connections to several different PGWs in the network). The PGW then may release all bearers of the UE except for the default bearer of the PDN connection that is to be handed over to WLAN. (According to the current specifications, the PGW triggers the release of all resources of the PDN connection within 3GPP RAN after the successful handover using PDN GW initiated Resource Allocation Deactivation, as defined in 23.402, section 7.9). After the handover, the EPS bearer over LTE will not be used for data transfer and all packets are sent over WLAN. Optionally, as the UE shows no activity over LTE, the 3GPP network may move the UE in ECM-IDLE mode after a time. However, when this happens or whether it happens at all depends on the 3GPP RAN configuration. As a specific example the required changes in the 3GPP to Non-3GPP handover procedure are presented for the case of trusted Wi-Fi, as shown in Fig. 1 . The call flow shown in Fig. 1 is based on the current specification, as described in TS 23.402, section 8.2.2 and includes changes according to the specific example according to example versions of the present invention. Note that similar changes can be added for the case when untrusted Wi-Fi network is used.

As shown in Fig. 1 , the UE is served by 3GPP access and a GTP (GPRS tunnelling protocol) tunnel is established between the Serving GW (SGW) and the PDN GW (PGW) in the evolved packet core (step 1 ).

In a step 2, the UE discovers a trusted non-3GPP access system, i.e. WLAN access, and determines to transfer its current sessions from the currently used 3GPP Access to the discovered trusted non-3GPP IP access system, i.e. to perform a handover to the non- 3GPP access system. In this step, the UE could be guided or commanded by steering information send by the BS or eNB to check for non-cellular access networks for traffic offload. A mechanism that aids the UE to discover the trusted non-3GPP IP access system is the above mentioned Access Network Discovery and Selection Function (ANDSF).

In a step 3, access authentication is performed by the UE in the non-3GPP access system. The 3GPP AAA (Authentication Authorization and Accounting) server authenticates and authorizes the UE for access in the trusted non-3GPP system.

After successful authentication and authorization, in step 4, the L3 attach procedure is triggered. According to the specific example according to example versions of the present invention, here, the UE should send an indication that the PGW should not release the resources in the 3GPP access network. This is especially useful if the UE is aware that this is the only PDN connection it uses. As an advantageous implementation the UE shall send the indication only if the UE has recognized in step 2 that the 3GPP RAN provides the related steering information to UEs. This might be configurable by the network operator in UE policy setting. Or the indication might be also set in every HO and for every PDN connection to improve the HO performance as described later. This indication is sent to the non-3GPP access network in step 4 and is forwarded in step 5 from the non-3GPP access network to the PGW.

In step 5, the trusted non-3GPP access network initiates a session by sending a create session request to the PGW (including the above mentioned indication).

Then, in steps 6A and 6B, a PCEF initiated IP-CAN session modification procedure is performed and the AAA server and HSS are updated (which will not be described in detail).

In step 7, a create session response message including the IP address is sent from the PGW to the non-3GPP access network.

In step 8, the L3 attach procedure is completed and the IP address(es) assigned to the UE by the PGW is conveyed to the UE.

In step 9, the GTP tunnel is set up between the Trusted Non-3GPP IP Access and the PGW. At this point, the UE can send/receive IP packets. Optionally, for connectivity to multiple PDNs, in step 10, the UE establishes connectivity to all the PDNs that are being transferred from 3GPP access besides the PDN connection that was established in the above mentioned steps 3 to 9.

Then, in step 1 1 , according to the current specifications, the PGW shall initiate the PGW Initiated PDN Disconnection procedure in 3GPP access or the PDN GW Initiated Bearer Deactivation procedure as defined in TS 23.401 , clause 5.4.4.1 . However, according to the specific example according to example versions of the present invention, here, the PGW should only release the dedicated bearers, i.e. all bearers of the UE except for the default bearer of the PDN connection to the 3GPP access side, according to the indication sent in steps 4 and 5 for the marked PDN connection, as described above. Optionally, if multiple PDN connections have been handed over and those other PDN connections are not marked with the indication according to this invention, those PDN connections can be released with all its default and dedicated bearers.

Thus, according to the specific example according to example versions of the present invention, a PDN connection of the UE over the 3GPP access network is not released but kept in an idle state, and all packets are sent over the non-3GPP network.

In summary, the required changes are as follows:

• the UE should send an indication that the PGW should not release the resources in the 3GPP access network (cf. step 4 in Fig. 1 ). This indication should be forwarded to the PDN GW (cf. step 4 and 5 in Fig. 1 ).

• the PGW should only release the dedicated bearers and maintain the default bearer of the PDN connection (cf. step 1 1 in Fig. 1 ). Optionally, in step 3, the HSS could be informed about the indication as well.

Fig. 2 is a flowchart illustrating an example of a method according to example versions of the present invention.

According to example versions of the present invention, the method may be implemented in a communication device, like a user equipment (UE) or the like. In step S22, the UE prepares an indication that a packet data network connection to a cellular communication system is to be maintained. Then, the user equipment transmits the indication to an access point of a non-cellular communication system in a step S23, and the indication is then forwarded by the access point to a gateway.

Optionally, prior to transmitting the indication to the access point, the UE may perform discovery of a non-cellular access network and initiate a handover to the non-cellular communication network in a step S21 . The indication may be inserted in a Layer 3 attach procedure or a handover request message that is transmitted from the UE to the access point, and according to the indication, the data connection of the UE over the cellular communication network is maintained in an idle state.

Optionally, the method may further comprise receiving traffic steering information from the cellular radio access network / base station. Then, the indication may be prepared depending on the reception of the traffic steering information from the cellular radio access network. That is, according to example versions of the present invention, the indication may only be prepared if the traffic steering information has been received.

Further, the indication may be prepared in the handover of the last data connection of the user equipment over the cellular communication system only or for any data connection depending on policies stored in the user equipment.

In Fig. 3, a diagram illustrating an example of a configuration of an apparatus 30, such as of a user equipment or part of a user equipment according to some example versions of the disclosure is shown, which is configured to implement the processing as described in connection with some of the example versions of the disclosure. It is to be noted that the apparatus 30, like the user equipment, shown in Fig. 3 may comprise further elements or functions besides those described herein below. Furthermore, even though reference is made to a user equipment, the apparatus may be also another device having a similar function, such as a chipset, a chip, a module etc., which can also be part of a UE or attached as a separate element to a UE, or the like. It should be understood that each block and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry.

The user equipment shown in Fig. 3 may comprise a processing function, control unit or processor 31 , such as a CPU or the like, which is suitable for executing instructions given by programs or the like related to the above described procedure. The processor 31 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference sign 32 denotes a transceiver or input/output (I/O) unit (interface) connected to the processor 31 . The I/O unit 32 may be used for communicating with one or more communication elements like UEs or with other communication network control elements, e.g. a base station, eNB, or the like. The I/O unit 32 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 33 denotes a memory usable, for example, for storing data and programs to be executed by the processor 31 and/or as a working storage of the processor 31 .

The processor 31 is configured to execute processing related to the above described procedure. In particular, the processor 31 comprises a sub-portion 31 1 as a processing portion which is usable for conducting a preparation of an indication. The portion 31 1 may be configured to perform processing according to S22 of Fig. 2. Furthermore, the processor 31 comprises a sub-portion 312 usable as a portion for transmitting the indication. The portion 312 may be configured to perform processing according to S23 of Fig. 2. Furthermore, the processor 31 may (optionally) comprise a sub-portion 313 usable as a portion for discovering a non-cellular access network and initiating a handover to the non-cellular communication network. The portion 313 may be configured to perform a processing according to S21 of Fig. 2.

Fig. 4 is a flowchart illustrating another example of a method according to example versions of the present invention. According to example versions of the present invention, the method may be implemented in a network element, like a gateway or the like. In step S41 , the gateway receives a request for creating a packet data connection for a user equipment over a non-cellular communication network. The request includes an indication that a data connection of the user equipment via a cellular communication network, to which the user equipment is attached at the time of receiving the request, is to be maintained. In case multiple PDN connections are used at cellular and/or non-3GPP access side, the PDN connections can be identified and distinguished by means of a bearer identifier. The indication to maintain a connection might be only applied to one bearer. Then, in a step S42, the gateway establishes a data connection for the user equipment over the non-cellular communication network, and then, in a step S43, the gateway releases the bearers of the user equipment in the cellular network except for the default bearer of the data connection of the user equipment over the cellular communication network that relates to the PDN connection that was handed over to non-3GPP access and was marked with the indication according to this invention.

The data connection of the user equipment over the cellular communication system is maintained in an idle state.

In Fig. 5, a diagram illustrating an example of a configuration of an apparatus 50, such as of a gateway or part of a gateway according to some example versions of the disclosure is shown, which is configured to implement the processing as described in connection with some of the example versions of the disclosure. It is to be noted that the apparatus 50, like the gateway, shown in Fig. 5 may comprise further elements or functions besides those described herein below. Furthermore, even though reference is made to a gateway, the apparatus may be also another device having a similar function, such as a chipset, a chip, a module etc., which can also be part of a gateway or attached as a separate element to a gateway, or the like. It should be understood that each block and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry or software in a cloud computing environment. The apparatus shown in Fig. 5 may comprise a processing function, control unit or processor 51 , such as a CPU or the like, which is suitable for executing instructions given by programs or the like related to the above described procedure. The processor 51 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference sign 52 denotes a transceiver or input/output (I/O) unit (interface) connected to the processor 51 . The I/O unit 52 may be used for communicating with one or more communication network elements, e.g. a base station, eNB, a Serving GW, or the like, or communication network control and management elements, like a MME, or the like. The I/O unit 52 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 53 denotes a memory usable, for example, for storing data and programs to be executed by the processor 51 and/or as a working storage of the processor 51 .

The processor 51 is configured to execute processing related to the above described procedure. In particular, the processor 51 comprises a sub-portion 51 1 as a processing portion which is usable for receiving and analyzing a request for creating a data connection. The portion 51 1 may be configured to perform processing according to S41 of Fig. 4. Furthermore, the processor 51 comprises a sub-portion 51 2 usable as a portion for establishing a data connection. The portion 51 2 may be configured to perform processing according to S42 of Fig. 4. Furthermore, the processor 51 comprises a sub-portion 51 3 usable as a portion for releasing bearers of the user equipment. The portion 51 3 may be configured to perform a processing according to S43 of Fig. 4.

Handover from WLAN to 3GPP

In the following, a case will be described where the UE moves back from the WLAN network to the 3GPP network.

When the UE would like to move back from the WLAN network (e.g. when it receives an indication from RAN that the overload situation in the cellular network is over) it starts using the "idle" PDN connection over LTE. If the UE is in ECM (evolved packet system connection management) - IDLE mode, then it performs a service request procedure in the same way as it would be done when UE would like to start using any other PDN connection after being in ECM-IDLE mode. The PGW shall interpret the 1 ^st received uplink packet from the UE in the default bearer that was maintained but not used as a handover request of the PDN connection, and thus shall trigger the allocation of the resources over LTE side (e.g. may contact PCC (policy control and charging), create the appropriate dedicated bearers), start sending downlink packets over LTE and trigger the removal of the resources of the PDN connection from the WLAN.

An alternative solution to the interpretation of the first packet over 3GPP access as HO indication from non-3GPP to 3GPP access would be a signaling indication in the Service request message send by the UE to the MME with a new code indicating the reactivation of the 3GPP bearer (explicit indication). This information would have to be passed from the SGW (serving gateway) to PGW in a Modify Bearer Request message, see 23.401 , 5.3.4.1 : UE triggered Service Request procedure, enhancement to step 9. Thus this alternative requires more specification and implementation effort. Fig. 6 is a signaling diagram illustrating a handover from WLAN to LTE according to a specific example of the example versions of the present invention.

In step 61 of Fig. 6, the UE receives a trigger from the eNB to move from WLAN (as an example for the non-3GPP, non-cellular communication network) to LTE (as an example for the 3GPP, cellular communication network). The UE is able to receive this RAN traffic steering indication as still being attached to LTE. It is noted that there might also be other triggers for the handover, like e.g. a loss of WLAN coverage or the like.

In step 62, an initial bearer establishment is performed between the UE, the eNB, and the MME/SGW. If the UE is ECM-IDLE mode then it shall initiate a service request procedure to activate EPS bearers. This is the normal UE behavior when it would like to send an uplink packet when it is in ECMJDLE state. In such a case, it is noted that no change in current eNB, MME and SGW behavior is needed. In the alternative solution, as mentioned above, a signaling indication is used in the Service Request message from UE to MME and Bearer Modification message from MME to SGW and PGW.

Then, in step 63, the UE sends its first uplink packet over LTE. From this point it shall not use WLAN to send packets for this PDN connection. When receiving the packet from the UE via the eNB and the SGW, the PGW interprets the 1 ^st received packet over LTE as a handover request and it starts using LTE for downlink packets (step 64). The PGW may interact with the Policy Charging and Rules Function (PCRF) for Policy Control and Charging (PCC) due to the access network change (step 65). As shown in Fig. 6 and described above, this procedure is now triggered by step 63 and 64 in Fig. 6. In current procedures this step is triggered by the Modify Bearer Request signaling (e.g. of the Service Request procedure).

In step 66, existing bearers may be modified and/or additional bearers may be created according to the need of the PDN connection, e.g. based on PCC rules.

Then, in step 67, the PGW triggers the release of the resources of the PDN connection in the WLAN as it is performed during a handover from WLAN to LTE according to the current specifications.

Fig. 7 is a flowchart illustrating an example of a method according to example versions of the present invention.

According to example versions of the present invention, the method may be implemented in a network element, like a user equipment (UE) or the like. In step S71 , the user equipment receives a trigger for initiating a handover from a non-cellular communication network to a cellular communication network. Then, in step S72, the UE initiates a service request procedure for activating a bearer for a data connection for the user equipment over the cellular communication network, and then, in step S73, it transmits a data packet over the bearer for the data connection for the user equipment over the cellular communication network.

According to example versions of the present invention, the data connection of the user equipment over the cellular communication network is maintained in a standby state prior to receiving the trigger. According to example versions of the present invention, the method further comprises receiving, at the user equipment, traffic steering information from the cellular radio access network. Further, the traffic steering information may include the trigger.

Further, it is noted that the trigger may also be generated inside the UE, e.g. based on certain measurements or the like.

In Fig. 8, a diagram illustrating an example of a configuration of an apparatus 80, such as of a user equipment or part of a user equipment according to some example versions of the disclosure is shown, which is configured to implement the processing as described in connection with some of the example versions of the disclosure. It is to be noted that the apparatus 80, like the user equipment, shown in Fig. 8 may comprise further elements or functions besides those described herein below. Furthermore, even though reference is made to a user equipment, the apparatus may be also another device having a similar function, such as a chipset, a chip, a module etc., which can also be part of a UE or attached as a separate element to a UE, or the like. It should be understood that each block and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry.

The user equipment shown in Fig. 8 may comprise a processing function, control unit or processor 81 , such as a CPU or the like, which is suitable for executing instructions given by programs or the like related to the above described procedure. The processor 81 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference sign 82 denotes a transceiver or input/output (I/O) unit (interface) connected to the processor 81 . The I/O unit 82 may be used for communicating with one or more communication elements like UEs or with other communication network control elements, e.g. a base station, eNB, or the like. The I/O unit 82 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 83 denotes a memory usable, for example, for storing data and programs to be executed by the processor 81 and/or as a working storage of the processor 81 . The processor 81 is configured to execute processing related to the above described procedure. In particular, the processor 81 comprises a sub-portion 81 1 as a processing portion which is usable for receiving a trigger for initiating a handover. The portion 81 1 may be configured to perform processing according to S71 of Fig. 7. Furthermore, the processor 81 comprises a sub-portion 812 usable as a portion for initiating a service procedure for activating a bearer for a data connection. The portion 812 may be configured to perform processing according to S72 of Fig. 7. Furthermore, the processor 81 comprises a sub-portion 813 usable as a portion for transmitting a data packet. The portion 813 may be configured to perform a processing according to S73 of Fig. 7. Fig. 9 is a flowchart illustrating another example of a method according to example versions of the present invention.

According to example versions of the present invention, the method may be implemented in a network element, like a gateway or the like. The gateway receives a data packet from a user equipment over a bearer for a data connection for the user equipment over a cellular communication network what was maintained but disabled for data transmission in a step S91 , and then initiates a handover of the user equipment to the cellular communication network in a step S92.

Further, in a step S93, the gateway stops transmitting data packets over the bearer according to the data connection over the non-cellular network to the user equipment and starts transmitting data packets to the user equipment over the bearer of the data connection of the user equipment over the cellular communication network. Then, the bearers for the data connection of the user equipment over a non-cellular communication network are released by the gateway. In Fig. 10, a diagram illustrating an example of a configuration of an apparatus 100, such as of a gateway or part of a gateway according to some example versions of the disclosure is shown, which is configured to implement the processing as described in connection with some of the example versions of the disclosure. It is to be noted that the apparatus 100, like the gateway, shown in Fig. 10 may comprise further elements or functions besides those described herein below. Furthermore, even though reference is made to a gateway, the apparatus may be also another device having a similar function, such as a chipset, a chip, a module etc., which can also be part of a gateway or attached as a separate element to a gateway, or the like. It should be understood that each block and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry.

The apparatus shown in Fig. 1 0 may comprise a processing function, control unit or processor 101 , such as a CPU or the like, which is suitable for executing instructions given by programs or the like related to the above described procedure. The processor 101 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference sign 1 02 denotes a transceiver or input/output (I/O) unit (interface) connected to the processor 101 . The I/O unit 102 may be used for communicating with one or more communication network elements, e.g. a base station, eNB, or the like, or communication network control and management elements, like a MME, or the like. The I/O unit 1 02 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 1 03 denotes a memory usable, for example, for storing data and programs to be executed by the processor 1 01 and/or as a working storage of the processor 101 .

The processor 101 is configured to execute processing related to the above described procedure. In particular, the processor 101 comprises a sub-portion 101 1 as a processing portion which is usable for receiving a data packet from a user equipment. The portion 101 1 may be configured to perform processing according to S91 of Fig. 9. Furthermore, the processor 101 comprises a sub-portion 1012 usable as a portion for initiating a handover. The portion 1012 may be configured to perform processing according to S92 of Fig. 9. Furthermore, the processor 101 comprise a sub-portions 1 01 3 and 1014 usable as portions transmitting data packets to the user equipment and for releasing respective bearers of the user equipment. The portions 1 014 may be configured to perform a processing according to S93 of Fig. 9.

According to example versions of the present invention as described above, the handover from a non-3GPP access network to a 3GPP access network is quite simple and can be performed much faster than the normal handover from a non-3GPP access network to a 3GPP access network, as currently defined. Namely, in the normal handover, the UE should perform a complete attach procedure with 3GPP network as described in section 8.2.1 of 3GPP TS 23.402. Thus the proposed solution according to example versions of the present invention results in a much better handover performance.

Therefore this mechanism might be used not only to preserve the UE in LTE attached state for better network controlled traffic steering of the U E to the right access system, but also to improve the handover performance. This can be important when the UE uses realtime services over WLAN, as the coverage of a WLAN might be lost extremely quickly due to small spots of WLAN coverage. This would enable operates to use both Voice over LTE (VoLTE) and Voice over Wi-Fi (VoWi-Fi), for example. UE based implementation

Next, an U E based implementation for a handover from a 3GPP network to a non-3GPP network according to some example versions of the present invention will be described in detail.

In a case where there is only one PDN connection that is targeted to switch to WLAN, it is proposed that the UE establishes a second PDN connection before handover of the first PDN connection to WLAN is performed. When the first PDN connection is then handed over to WLAN, this second connection will be kept by the UE but will not be used for data transfer.

The UE can enable this functions based on operator policy provided by ANDSF (Access Network Discovery and Selection Function) and these function are conditionally activated if the UE sees the RAN providing traffic steering information e.g. in broadcasted SIBs. If the UE camps in a RAN area not supporting this feature, the UE will hand over the traffic to WLAN and release the 3GPP resources as usual.

Fig. 1 1 is a flowchart illustrating an example of a method according to example versions of the present invention.

According to example versions of the present invention, the method may be implemented in a communication device, like a user equipment or the like. In a step S1 1 1 , the user equipment receives a trigger for a handover of a first data connection from a cellular communication network to a non-cellular communication network, i.e. to move from a LTE network to a WLAN network. This trigger might be facilitated by RAN traffic steering information. In particular, in a similar manner as described above, the UE may have received traffic steering information from the cellular network/BS and may perform discovery of a non-cellular access network. Then, in step S1 1 2, the user equipment initiates an establishment of a second data connection of the user equipment over the cellular communication network, before performing the handover of the first data connection. Thereafter, in step S1 13, the user equipment performs the handover of the first data connection to the non-cellular communication network, while maintaining the second data connection of the user equipment over the cellular communication network in step S1 14.

According to example versions of the present invention, the method may further comprise receiving traffic steering information from the cellular radio access network, and performing discovery of a non-cellular access network based on the traffic steering information received from the cellular radio access network. Further, according to example versions of the present invention, the traffic steering information may include the trigger.

After the handover, the user equipment transmits data packets only over the first data connection of the user equipment over the non-cellular communication network which has been handed over. The second data connection of the user equipment over the cellular communication network is not used for data transmission but is maintained in an idle state. Thus, the second data connection is not released after the handover.

In this regard, if additional network support will be provided for this solution, further optimizations to reduce the signaling effort are possible. Namely, the UE may indicate with special information that the second PDN connection request is only a request for a standby bearer. This can be also coded with dedicated APNs (Access Point Names). For example, if the UE performs a HO (handover) to WLAN for the APN "Internet", the APN "Internet standby" could be used for the second PDN connection. If the MME is aware of the special kind of PDN connection, it can skip the establishment of radio bearers and establishes the session only in the core network. The UE can then easy be switched to IDLE mode.

In Fig. 1 2, a diagram illustrating an example of a configuration of an apparatus 1 20, such as of a user equipment or part of a user equipment according to some example versions of the disclosure is shown, which is configured to implement the processing as described in connection with some of the example versions of the disclosure. It is to be noted that the apparatus 120, like the user equipment, shown in Fig. 12 may comprise further elements or functions besides those described herein below. Furthermore, even though reference is made to a user equipment, the apparatus may be also another device having a similar function, such as a chipset, a chip, a module etc., which can also be part of a UE or attached as a separate element to a UE, or the like. It should be understood that each block and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry.

The user equipment shown in Fig. 1 2 may comprise a processing function, control unit or processor 121 , such as a CPU or the like, which is suitable for executing instructions given by programs or the like related to the above described procedure. The processor 121 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference sign 1 22 denotes a transceiver or input/output (I/O) unit (interface) connected to the processor 121 . The I/O unit 122 may be used for communicating with one or more communication elements like UEs or with other communication network control elements, e.g. a base station, eNB, or the like. The I/O unit 122 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 123 denotes a memory usable, for example, for storing data and programs to be executed by the processor 121 and/or as a working storage of the processor 1 21 .

The processor 121 is configured to execute processing related to the above described procedure. In particular, the processor 121 comprises a sub-portion 121 1 as a processing portion which is usable for receiving a handover trigger. The portion 121 1 may be configured to perform processing according to S1 1 1 of Fig. 1 1 . Furthermore, the processor 121 comprises a sub-portion 1 212 usable as a portion for initiating an establishment of a data connection. The portion 1212 may be configured to perform processing according to S1 1 2 of Fig. 1 1 . Furthermore, the processor 1 21 comprises a sub-portion 1213 usable as a portion for performing handover. The portion 1213 may be configured to perform a processing according to S1 1 3 of Fig. 1 1 . Additionally, the processor 121 comprises a sub-portion 1214 usable as a portion for maintaining the second data connection. The portion 1214 may be configured to perform a processing according to S1 14 of Fig. 1 1 .

In view of the above, according to example versions of the present invention, it is proposed that it is assured that a user equipment is always attached to a 3GPP access network, like e.g. LTE, when offloading data a non-3GPP access network, like e.g. WLAN.

In such a case, it is possible that the UE receives traffic steering information from the 3GPP Access network, e.g. in order to switch back from the non-3GPP access network to the 3GPP access network if a congestion situation in the 3GPP access network has disappeared.

Further, there is also provided a method for fast handover between the non-3GPP access network and the 3GPP access network, i.e. a fast and smooth switch of data transfer between the different access systems. Further, a fast switch back to the cellular communication system is possible, if the conditions in Wi-Fi get worse. In the foregoing exemplary description of the apparatuses, only the units/means that are relevant for understanding the principles of the invention have been described using functional blocks. The apparatus may comprise further units/means that are necessary for its respective operation as network element, like user equipment, gateway, and the like, respectively. However, a description of these units/means is omitted in this specification. The arrangement of the functional blocks of the apparatus is not construed to limit the invention, and the functions may be performed by one block or further split into sub- blocks.

When in the foregoing description it is stated that the apparatus (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that a (i.e. at least one) processor or corresponding circuitry, potentially in cooperation with computer program code stored in the memory of the respective apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured circuitry or means for performing the respective function (i.e. the expression "unit configured to" is construed to be equivalent to an expression such as "means for"). For the purpose of the present invention as described herein above, it should be noted that

- method steps likely to be implemented as software code portions and being run using a processor at an apparatus (as examples of devices, apparatuses and/or modules thereof, or as examples of entities including apparatuses and/or modules therefore), are software code independent and can be specified using any known or future developed programming language as long as the functionality defined by the method steps is preserved;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the aspects/embodiments and its modification in terms of the functionality implemented;

- method steps and/or devices, units or means likely to be implemented as hardware components at the above-defined apparatuses, or any module(s) thereof, (e.g., devices carrying out the functions of the apparatuses according to the aspects/embodiments as described above) are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field- programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components;

- devices, units or means (e.g. the above-defined apparatuses, or any one of their respective units/means) can be implemented as individual devices, units or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device, unit or means is preserved;

- an apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor;

- a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example. In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.

Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention. Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.

Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.

It is noted that the aspects/embodiments and general and specific examples described above are provided for illustrative purposes only and are in no way intended that the present invention is restricted thereto. Rather, it is the intention that all variations and modifications which fall within the scope of the appended claims are covered. Abbreviations:

3GPP 3rd Generation Partnership Project

AAA Authentication Authorization and Accounting

ANDSF Access Network Discovery and Selection Function, specified in 3GPP AP Access Point (base station in Wi-Fi networks)

APN Access Point Name

(used to identify PDN connections and direct to right networks) API Application Programming Interface

App Application software for mobile devices

BS Base Station

CDMA Code Division Multiple Access

DSL Digital Subscriber Line

ECM Evolved packet system Connection Management

EDGE Enhanced Data Rates for Global Evolution eNB eNodeB, E-UTRAN node B, BS in LTE

GW Gateway, S/P-GW

GTP GPRS tunnelling protocol

GPRS General Packet Radio Service

HO Handover

HSS Home Subscriber Server

IEEE Institute of Electrical and Electronics Engineers IETF Internet Engineering Task Force

IFOM Internet Protocol Flow Mobility

ISDN Integrated Services Digital Network

ITU International Telecommunication Union

LTE Long-Term Evolution

LTE-A Long-Term Evolution Advanced

MME Mobilty Management Entity

PCC Policy Control and Charging

PCEF Policy and Charging Enforcement Function

PCRF Policy Charging and Rules Function PDN Packet Data Network

PGW Packet Data Network Gateway

PLMN Public Land Mobile Network

RAN Radio Access Network RAN WG2 Radio Access Network Working Group 2 (in 3GPP standardization)

SIB System Information Block

SGW Serving Gateway

TISPAN Telecoms & Internet converged Services & Protocols for Advanced

Networks TS Traffic Steering

UE User Equipment

UMTS Universal Mobile Telecommunications System

UP User Plane

Wi-Fi synonym for WLAN WiMAX Worldwide Interoperability for Microwave Access,

WLAN Wireless LAN (local area network)

Claims

1 . A method, comprising: preparing, at a user equipment, an indication that a data connection of the user equipment over a cellular communication system is to be maintained, and transmitting the indication to an access point of a non-cellular communication system.

2. The method according to claim 1 , wherein the indication is inserted in a handover request message.

3. The method according to claim 1 or 2, wherein the data connection of the user equipment over the cellular communication system is maintained in an idle state.

4. The method according to any one of claims 1 to 3, further comprising : discovering a non-cellular access network, initiating a handover to the non-cellular communication network, and transmitting the indication to the access point of the non-cellular communication system after the non-cellular communication network is discovered and the handover is initiated.

5. The method according to any one of claims 1 to 4, further comprising : receiving traffic steering information from the cellular radio access network, preparing the indication depending on reception of the traffic steering information from the cellular radio access network.

6. The method according to any one of claims 1 to 5, further comprising : preparing the indication in the handover of the last data connection of the user equipment over the cellular communication system only or for any data connection depending on policies stored in the user equipment.

7. A method, comprising: receiving, at a gateway, a request for creating a packet data connection of a user equipment over a non-cellular communication network, the request including an indication that a data connection of the user equipment over a cellular communication network, to which the user equipment is attached at the time of receiving the request, is to be maintained, establishing a data connection for the user equipment over the non-cellular communication network; and releasing bearers of the user equipment except for a bearer of the data connection of the user equipment over the cellular communication network.

8. The method according to claim 7, further comprising : maintaining the data connection of the user equipment over the cellular communication system in an idle state.

9. A method, comprising: receiving, at a user equipment, a trigger for initiating a handover from a non- cellular communication network to a cellular communication network, initiating a service request procedure for activating a bearer for a data connection of the user equipment over the cellular communication network, and transmitting a data packet over the bearer for the data connection of the user equipment over the cellular communication network.

10. The method according to claim 9, wherein the data connection of the user equipment over the cellular communication network is maintained in a standby state prior to receiving the trigger.

1 1 . The method according to claim 9 or 10, further comprising receiving, at the user equipment, traffic steering information from the cellular radio access network.

12. The method according to claim 1 1 , wherein the traffic steering information includes the trigger.

13. A method, comprising: receiving, at a gateway, a data packet from a user equipment over a bearer for a data connection of the user equipment over a cellular communication network, and initiating a handover of the user equipment to the cellular communication network.

14. The method according to claim 13, further comprising: transmitting data packets to the user equipment over the bearer for data connection of the user equipment over the cellular communication network, and releasing bearers for the data connection of the user equipment over a non-cellular communication network.

15. A method, comprising: receiving, at a user equipment, a trigger for a handover of a first data connection from a cellular communication network to a non-cellular communication network, initiating, by the user equipment, establishment of a second data connection of the user equipment over the cellular communication network, before performing the handover of the first data connection, performing handover of the first data connection to the non-cellular communication network, and maintaining the second data connection of the user equipment over the cellular communication network.

16. The method according to claim 15, wherein data packets are transmitted over the first data connection, and the second data connection is not used for data transmission after performing the handover.

17. The method according to claim 15 or 16, wherein the initiation for establishing the second data connection includes an indication that the second data connection will be used in a standby state.

18. The method according to any one of claims 15 to 17, further comprising: receiving traffic steering information from the cellular radio access network, and performing discovery of a non-cellular access network based on the traffic steering information received from the cellular radio access network.

19. The method according to claim 18, wherein the traffic steering information includes the trigger.

20. An apparatus comprising at least one processor, and

at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: preparing an indication that a data connection of a user equipment over a cellular communication system is to be maintained, and transmitting the indication to an access point of a non-cellular communication system.

21 . The apparatus according to claim 20, wherein the indication is inserted in a handover request message.

22. The apparatus according to claim 20 or 21 , wherein the data connection of the user equipment over the cellular communication system is maintained in an idle state.

23. The apparatus according to any one of claims 20 to 22, wherein the at least one memory and the instructions are further configured to, with the at least one processor, cause the apparatus at least to perform: discovering a non-cellular access network, initiating a handover to the non-cellular communication network, and transmitting the indication to the access point of the non-cellular communication system after the non-cellular communication network is discovered and the handover is initiated.

24. The apparatus according to any one of claims 20 to 23, wherein the at least one memory and the instructions are further configured to, with the at least one processor, cause the apparatus at least to perform: receiving traffic steering information from the cellular radio access network, preparing the indication depending on reception of the traffic steering information from the cellular radio access network.

25. The apparatus according to any one of claims 20 to 24, wherein the at least one memory and the instructions are further configured to, with the at least one processor, cause the apparatus at least to perform: preparing the indication in the handover of the last data connection of the user equipment over the cellular communication system only or for any data connection depending on policies stored in the user equipment.

26. An apparatus comprising at least one processor, and

at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: receiving a request for creating a packet data connection of a user equipment over a non-cellular communication network, the request including an indication that a data connection of the user equipment over a cellular communication network, to which the user equipment is attached at the time of receiving the request, is to be maintained, establishing a data connection for the user equipment over the non-cellular communication network; and releasing bearers of the user equipment except for a bearer of the data connection of the user equipment over the cellular communication network.

27. The apparatus according to claim 26, wherein the at least one memory and the instructions are further configured to, with the at least one processor, cause the apparatus at least to perform: maintaining the data connection of the user equipment over the cellular communication system in an idle state.

28. An apparatus comprising at least one processor, and

at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: receiving a trigger for initiating a handover of a user equipment from a non-cellular communication network to a cellular communication network, initiating a service request procedure for activating a bearer for a data connection of the user equipment over the cellular communication network, and transmitting a data packet over the bearer for the data connection of the user equipment over the cellular communication network.

29. The apparatus according to claim 28, wherein the data connection of the user equipment over the cellular communication network is maintained in a standby state prior to receiving the trigger.

30. The apparatus according to claim 28 or 29, wherein the at least one memory and the instructions are further configured to, with the at least one processor, cause the apparatus at least to perform: receiving traffic steering information from the cellular radio access network.

31 . The apparatus according to claim 29, wherein the traffic steering information includes the trigger.

32. An apparatus comprising at least one processor, and

at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: receiving a data packet from a user equipment over a bearer for a data connection of the user equipment over a cellular communication network, and initiating a handover of the user equipment to the cellular communication network.

33. The apparatus according to claim 32, wherein the at least one memory and the instructions are further configured to, with the at least one processor, cause the apparatus at least to perform: transmitting data packets to the user equipment over the bearer for data connection of the user equipment over the cellular communication network, and releasing bearers for the data connection of the user equipment over a non-cellular communication network.

34. An apparatus comprising at least one processor, and

at least one memory for storing instructions to be executed by the processor, wherein the at least one memory and the instructions are configured to, with the at least one processor, cause the apparatus at least to perform: receiving a trigger for a handover of a first data connection of a user equipment from a cellular communication network to a non-cellular communication network, initiating establishment of a second data connection of the user equipment over the cellular communication network, before performing the handover of the first data connection, performing handover of the first data connection to the non-cellular communication network, and maintaining the second data connection of the user equipment over the cellular communication network.

35. The apparatus according to claim 34, wherein data packets are transmitted over the first data connection, and the second data connection is not used for data transmission after performing the handover.

36. The apparatus according to claim 34 or 35, wherein the initiation for establishing the second data connection includes an indication that the second data connection will be used in a standby state.

37. The apparatus according to any one of claims 34 to 36, wherein the at least one memory and the instructions are further configured to, with the at least one processor, cause the apparatus at least to perform: receiving traffic steering information from the cellular radio access network, and performing discovery of a non-cellular access network based on the traffic steering information received from the cellular radio access network.

38. The apparatus according to claim 37, wherein the traffic steering information includes the trigger.

39. A computer program product including a program for a processing device, comprising software code portions for performing the steps of any one of claims 1 to 19 when the program is run on the processing device.

40. The computer program product according to claim 39, wherein the computer program product comprises a computer-readable medium on which the software code portions are stored.

41 . The computer program product according to claim 39, wherein the program is directly loadable into an internal memory of the processing device.

42. An apparatus comprising: means for preparing an indication that a data connection of a user equipment over a cellular communication system is to be maintained, and means for transmitting the indication to an access point of a non-cellular communication system.

43. An apparatus comprising: means for receiving a request for creating a packet data connection of a user equipment over a non-cellular communication network, the request including an indication that a data connection of the user equipment over a cellular communication network, to which the user equipment is attached at the time of receiving the request, is to be maintained, means for establishing a data connection for the user equipment over the non- cellular communication network; and means for releasing bearers of the user equipment except for a bearer of the data connection of the user equipment over the cellular communication network.

44. An apparatus comprising: means for receiving a trigger for initiating a handover of a user equipment from a non-cellular communication network to a cellular communication network, means for initiating a service request procedure for activating a bearer for a data connection of the user equipment over the cellular communication network, and means for transmitting a data packet over the bearer for the data connection of the user equipment over the cellular communication network.

45. An apparatus comprising: means for receiving a data packet from a user equipment over a bearer for a data connection of the user equipment over a cellular communication network, and means for initiating a handover of the user equipment to the cellular communication network.

46. An apparatus comprising: means for receiving a trigger for a handover of a first data connection of a user equipment from a cellular communication network to a non-cellular communication network, means for initiating establishment of a second data connection of the user equipment over the cellular communication network, before performing the handover of the first data connection, means for performing handover of the first data connection to the non-cellular communication network, and means for maintaining the second data connection of the user equipment over the cellular communication network.