WWAN CONTROL PLANE SIGNALLING VIA WLAN

Technical field

[0001 ] The present disclosure relates to wireless communication and in particular to control signalling of Wireless Wide Area Networks, WWANs, via Wireless Local Area Networks, WLANs.

Background

[0002] Wireless wide area networks (WWANs) employ wireless access technologies that generally provide wider wireless coverage than those employed by wireless local area networks (WLANs). WWANs may employ for instance wireless access technologies such as GSM, WCDMA, Long Term Evolution (LTE), or other cellular technologies specified by the 3 ^rd Generation Partnership Project (3GPP), whereas WLANs may employ wireless access technologies such as those specified by IEEE 802.1 1 standards. As another differentiator, WWANs historically have operated in wireless spectrum portions that are licensed to specific WWAN operators, whereas WLANs typically operate in spectrum portions that are unlicensed, i.e., available for use by essentially anyone.

[0003] Different methods to integrate WWAN and WLAN have been explored, for accomplishing different purposes. One method involves for instance steering user equipment (UE) to one of WWAN or WLAN, e.g., based upon signal strength measurements. These signal strength measurements are typically made by a UE on signals that are transmitted from a network node, such as a WLAN Access Point (AP), or on base stations such as an eNB in a WWAN (e.g., LTE) radio access network. If signal conditions are more favourable in one or the other of these two radio access methods, the more favourable method will be used for communication between a UE and a network node. In addition to such traffic steering, solutions have been described to allow the UE to make an informed decision of selection of access. ANDSF (Access Network Discovery and Selection Function), as specified in 3GPP, provides additional information to the UE to select a preferred access method. [0004] More advanced solutions have also been described. In 3GPP Release 13, and as described in 3GPP TS 36.300, LTE - WLAN Aggregation (LWA) provides a solution for splitting traffic between both a WLAN AP and an LTE/4G eNB simultaneously. For example, data that reaches an eNB may be routed either over an LTE air interface or over a WLAN air interface, via an Xw interface between the eNB and a WLAN entity, known as a WLAN termination point (WT).

[0005] Figure 1 illustrates a selected set of entities involved in LWA. The wireless communication system 100 includes the logical nodes eNB 1 10, with an interface Xw 120 to a wireless termination point, WT 130, and a WLAN AP 150. The WLAN AP 150 can communicate wirelessly with the UE 170 utilizing techniques specified by IEEE 802.1 1 WG over a WLAN air interface 160. Further, the eNB 1 10 can communicate wirelessly with the UE 170 utilizing techniques specified by 3GPP over an LTE air interface 140. With LWA, it is the eNB that decides how data should be routed. It should be noted that implementation of the different logical nodes may be done in a number of different ways. For example, the WT 130 may be implemented in the same physical location / casing as the WLAN Access Point 150 and/or in combination with, e.g., a WLAN Access

Controller (not illustrated in the picture), or in a stand-alone fashion. There may thus be one WT entity to serve one or several WLAN Access points.

[0006] The main purpose of all of the methods described above is to provide an efficient way to both offload traffic from LTE (through routing, selection) but also to explore possibilities for higher aggregated rates (utilizing both WLAN and LTE simultaneously) and provide a higher performance.

[0007] As described, and in particular for LWA, the UE may receive and transmit using links to both eNB and WLAN AP. The feature has originally only been standardized for downlink communication, i.e., for communication from the network to the UE, however there are ambitions to also include support for uplink communication in the 3GPP standard and work is ongoing.

[0008] The routing of data in the eNB occurs on the PDCP (Packet Data

Convergence Protocol) layer. The PDCP layer is specified in 3GPP TS 36.321 . For PDCP Packed Data Units (PDCP PDU's) the eNB may dynamically decide how to route them to the UE, either to the UE using LTE protocols (i.e., LTE RLC, LTE MAC and LTE Physical Layers) or via the Xw interface 120 to the WT 130 and further to the WLAN AP 150 and over the WLAN air interface 160, using the WLAN MAC and PHY. The Xw interface is defined by 3GPP to be between eNB and WT which is a 3GPP logical WLAN node. It is not defined by standards what is between the WT and WLAN MAC.

[0009] Figure 2 illustrates a protocol architecture for LTE WLAN Aggregation.

[00010] The PDCP Protocol Layer handles PDCP PDU's. For Routing over LTE, the PDU's are further transmitted and handled over a Radio Link Control (RLC) Protocol 220, a Medium Access Control (MAC) Protocol 230, and a PHY Link / Layer 1 240. For routing over WLAN, the PDUs are further transmitted and handled over an LWA AP (LWA Adaptation Protocol) 250, further to a WLAN MAC 260 and a WLAN PHY/Layer 1 270 protocol.

[0001 1 ] The PDCP layer can split the traffic for downlink transmission and decide to route a PDCP PDU either via LTE or via WLAN. On the UE side, PDCP implements a continuous re-ordering such that PDCP PDU's may be received in the wrong order, e.g., due to different delays over the different links. This will secure in-sequence delivery of PDCP PDU's to higher layers. It should be noted that in Figure 2, only the lower protocol layers are illustrated and that above PDCP, other protocol levels, such as UDP, TCP are traversed.

[00012] The LWA AP 250 has a specific purpose. It is possible to offload and aggregate PDCP PDUs from different bearers via WLAN and to be able to separate the PDUs from and associate them to a correct bearer. In this regard, a bearer identifier is added by the eNB. This is done on the LWA AP 250 layer. The LWA AP is further described in 3GPP TS 36.360.

[00013] Figure 3 illustrate a UE with a similar protocol architecture as that illustrated in Figure 2, for the network. [00014] As mentioned above, in a coming 3GPP specification, it is expected that support for uplink LWA aggregation will be supported too. This is indicated by a Work Item description governing the scope of work in 3GPP, RP-160600.

[00015] Note that LWA only focuses on offloading or aggregating user plane traffic (e.g., data radio bearers). Indeed, LWA and other WWAN-WLAN integration approaches rely on the WWAN air interface to transfer control signalling plane traffic (e.g., radio resource control, RRC and Non-Access Stratum, NAS information), since the WWAN radio access network controls whether user data traffic is routed over the WWAN radio access, the WLAN radio access, or both.

Summary

[00016] The object is to obviate at least some of the problems outlined above. In particular, it is an object to provide a wireless device operable in a WWAN and a WLAN employing different RATs, a WWAN radio access node, a WLAN node and respective methods performed thereby. These objects and others may be obtained by providing a wireless device, a WWAN radio access node, a WLAN node and a method in a wireless device, a WWAN radio access node, a WLAN node according to the independent claims attached below.

[00017] According to an aspect, a method performed by a wireless device operable in a WWAN and a WLAN employing different RATs is provided. The method comprises establishing a WLAN radio access with a WLAN node. When WWAN radio access is unavailable to the wireless device, the method comprises transmitting and/or receiving a control signalling plane message to and/or from a WWAN radio access node via the WLAN node.

[00018] According to an aspect, a method performed by a WWAN radio access node operable in a WWAN is provided. The method comprises establishing an interface between the WWAN radio access node and a WLAN node of a WLAN. When WWAN radio access is unavailable to a wireless device, the method comprises transmitting and/or receiving a control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface. [00019] According to an aspect, a method performed by a WLAN node operable in a WLAN is provided. The method comprises establishing an interface between the WLAN node and a WWAN radio access node of a WWAN. When WWAN radio access is unavailable to a wireless device, the method comprises forwarding a control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access and the established interface.

[00020] According to an aspect, a wireless device operable in a WWAN and a WLAN employing different RATs is provided. The wireless device is configured for establishing a WLAN radio access with a WLAN node. When WWAN radio access is unavailable to the wireless device, the wireless device is configured for transmitting and/or receiving a control signalling plane message to and/or from a WWAN radio access node via the WLAN node.

[00021 ] According to an aspect, a WWAN radio access node operable in a WWAN is provided. The WWAN radio access node is configured for establishing an interface between the WWAN radio access node and a WLAN node of a WLAN. When WWAN radio access is unavailable to a wireless device, the WWAN radio access node is configured for transmitting and/or receiving a control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the

established interface.

[00022] According to an aspect, a WLAN node operable in a WLAN is provided. The WLAN node is configured for establishing an interface between the WLAN node and a WWAN radio access node of a WWAN. When WWAN radio access is unavailable to a wireless device, the WLAN node is configured for forwarding a control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access and the established interface.

[00023] The wireless device, the WWAN radio access node, the WLAN node and the respective method performed thereby have several advantages. One possible advantage is that communication towards the WWAN, e.g. a 3GPP network, may continue by means of LWA, even in situations when WWAN, e.g. LTE, coverage is lost. The RRC anchoring and the UE context may be kept in the WWAN network node, e.g. an eNB, so this is also transparent to the EPC and to the rest of the RAN. An additional advantage is that the wireless device may provide radio measurements even outside the coverage of the WWAN; this may be particularly beneficial in conjunction with SON functionality in order to provide additional information about problematic areas. Another possible advantage is that the significant impact is limited to RRC routing inside the WWAN network node and the wireless device; it is possible to support functionality without any change to the LWA architecture according to 3GPP release 13.

Brief description of drawings

[00024] Embodiments will now be described in more detail in relation to the accompanying drawings, in which:

[00025] Figure 1 illustrates a selected set of entities involved in LWA.

[00026] Figure 2 illustrates a protocol architecture for LTE WLAN Aggregation.

[00027] Figure 3 illustrates a wireless device, e.g. a UE, with a similar protocol architecture as that illustrated in figure 2, for the network.

[00028] Figure 4 is a schematic illustration of the control signalling plane message between a WWAN radio access node and a wireless device via a WLAN node.

[00029] Figure 5 schematically illustrates a control signalling plane message 28 in the form of an RRC message 28A.

[00030] Figure 6 illustrates an exemplifying system view according to some LWA embodiments.

[00031 ] Figure 7 illustrates further details of a WWAN radio access node, e.g. eNB, and the wireless device, e.g. UE, and E-UTRAN (WWAN) protocol layers and more specifically, the user plane protocol stack for user data traffic. [00032] Figure 8 is a corresponding figure to Figure 7, but for the control plane, i.e. the signalling.

[00033] Figure 9 illustrates a state diagram with two different RRC states, applicable for UE's that are attached to the EPC.

[00034] Figure 10 further illustrates the LWA AP protocol layer in the eNB 1001 and in the UE 1002.

[00035] Figure 1 1 is an illustration of the LWA AP data PDU 1 100. [00036] Figure 12 illustrates how a WT is added.

[00037] Figure 13 shows details of the eNB, UE, and E-UTRAN protocol layers for the control plane according to some of these embodiments that extend LWA to the control plane.

[00038] Figure 14 illustrates one or more embodiments for establishing an RRC connection with an LTE eNB via WLAN radio access, even when LTE radio access is unavailable.

[00039] Figure 15 shows one example of a WT Addition Request sent from the WT 1430 to the eNB 1440 to request the addition of LWA bearers for a specific UE (Step 4).

[00040] Figure 16 illustrates one example of a message informing the WT 1430 that the WT initiated WT Addition Preparation was successful.

[00041 ] Figure 17 illustrates one example of a message informing the WT 1430 that the WT initiated WT Addition Preparation has failed.

[00042] Figure 18 illustrates one example message structure.

[00043] Figure 19 illustrates a method 1500 performed by a user equipment 16 in a wireless communication system 10 according to some embodiments. [00044] Figure 20 illustrates a corresponding method 1600 performed by a wireless wide area network (WWAN) radio access node 20 of a WWAN 12.

[00045] Figure 21 correspondingly illustrates a method 1700 performed by a wireless local area network (WLAN) node 24 of a WLAN 14.

[00046] Figure 22 illustrates the user equipment 16 in the form of a user equipment 16A in accordance with one or more embodiments.

[00047] Figure 23 illustrates the user equipment 16 in the form of a user equipment 16B implemented in accordance with one or more other embodiments.

[00048] Figure 24 illustrates the WWAN radio access node 20 in the form of a WWAN radio access node 20A in accordance with one or more embodiments.

[00049] Figure 25 illustrates the WWAN radio access node 20 in the form of a WWAN radio access node 20B implemented in accordance with one or more other embodiments.

[00050] Figure 26 illustrates the WLAN node 24 in the form of a WLAN radio access node 24A in accordance with one or more embodiments.

[00051 ] Figure 27 illustrates the WLAN node 24 in the form of a WLAN node 24B implemented in accordance with one or more other embodiments.

[00052] Figure 28 illustrates an exemplifying embodiment of implementation of SRB support over LWA AP.

[00053] Figure 29 illustrates another exemplifying embodiment of implementation of SRB support over LWA AP.

[00054] Figure 30 is a flowchart of a method performed by wireless device operable in a Wireless Wide Area Network, WWAN, and a Wireless Local Area Network, WLAN, employing different Radio Access Technologies, RATs, according to an exemplifying embodiment. [00055] Figure 31 a is a flowchart of a method performed by a WWAN radio access node operable in a WWAN, according to an exemplifying embodiment.

[00056] Figure 31 b is a flowchart of a method performed by a WWAN radio access node operable in a WWAN, according to yet an exemplifying embodiment.

[00057] Figure 31 c is a flowchart of a method performed by a WWAN radio access node operable in a WWAN, according to still an exemplifying embodiment.

[00058] Figure 32a is a flowchart of a method performed by a WLAN node operable in a WLAN, according to an exemplifying embodiment.

[00059] Figure 32b is a flowchart of a method performed by a WLAN node operable in a WLAN, according to yet an exemplifying embodiment.

[00060] Figure 32c is a flowchart of a method performed by a WLAN node operable in a WLAN, according to still an exemplifying embodiment.

[00061 ] Figure 32d is a flowchart of a method performed by a WLAN node operable in a WLAN, according to another exemplifying embodiment.

[00062] Figure 33 is a block diagram of a wireless device operable in a WWAN and a WLAN employing different RATs, according to an exemplifying embodiment.

[00063] Figure 34 is a block diagram of a wireless device operable in a WWAN and a WLAN employing different Radio Access Technologies, RATs, according to another exemplifying embodiment.

[00064] Figure 35 is a block diagram of a WWAN radio access node operable in a WWAN, according to an exemplifying embodiment.

[00065] Figure 36 is a block diagram of a WWAN radio access node operable in a WWAN, according to another exemplifying embodiment.

[00066] Figure 37 is a block diagram of a WLAN node operable in a WLAN, according to an exemplifying embodiment. [00067] Figure 38 is a block diagram of a WLAN node operable in a WLAN, according to another exemplifying embodiment.

[00068] Figure 39 a block diagram of an arrangement in a wireless device operable in a WWAN and a WLAN employing different RATs, according to an exemplifying embodiment.

[00069] Figure 40 is a block diagram of an arrangement in a WWAN radio access node operable in a WWAN, according to an exemplifying embodiment.

[00070] Figure 41 is a block diagram of an arrangement in a WLAN node operable in a WLAN, according to an exemplifying embodiment.

Detailed description

[00071 ] One or more embodiments herein transfer a control signalling plane message (e.g., an RRC or NAS message) between a UE and a WWAN radio access node via WLAN radio access. Embodiments may do so, for example, when WWAN radio access is unavailable or no control signalling plane is established over WWAN radio access. Decoupling transfer of control plane signalling from WWAN radio access in this way, some embodiments herein establish or continue an RRC connection to the WWAN irrespective of WWAN radio access availability. This in turn makes WWAN-WLAN integration robust to WWAN radio access availability according to some embodiments.

[00072] In particular, embodiments herein include a method performed by a user equipment in a wireless communication system. The method comprises

establishing wireless local area network (WLAN) radio access. The method also comprises, when wireless wide area network (WWAN) radio access is unavailable to the user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmitting or receiving a control signalling plane message to or from a WWAN radio access node via the WLAN radio access.

[00073] Other embodiments herein include a method performed by a wireless wide area network (WWAN) radio access node of a WWAN. The method includes establishing an interface between the WWAN radio access node and a wireless local area network (WLAN) node of a WLAN. The method further includes, for example when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmitting or receiving a control signalling plane message to or from the user equipment via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface.

[00074] Embodiments also include a corresponding method performed by a wireless local area network (WLAN) node of a WLAN. The method comprises establishing an interface between the WLAN radio access node and a wireless wide area network (WWAN) radio access node of a WWAN. The method further comprises, when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN, forwarding a control signalling plane message between the user equipment and the WWAN radio access node via WLAN radio access and the established interface.

[00075] Embodiments further include corresponding apparatus, computer programs, and carriers (e.g., computer program products).

[00076] Figure 4 shows a wireless communication system 10 according to some embodiments. As shown, the system 10 includes a wireless wide area network (WWAN) 12 such as a Long Term Evolution (LTE) network, as well as a wireless local area network (WLAN) 14 such as a Wi-Fi network. A user equipment (UE) 16 in the system 10 is capable of establishing radio access to the WWAN 12 and the WLAN 14, either simultaneously or at separate times. As shown, for instance, the UE 16 is capable of establishing WWAN radio access 18 over which the UE 16 may wirelessly communicate with the WWAN 12, e.g., via a WWAN radio access node 20 such as an LTE eNodeB. The UE 16 is also capable of establishing WLAN radio access 22 over which the UE 16 may wirelessly communicate with the WLAN 14, e.g., via a WLAN node 24 such as a WLAN termination point (WT), a WLAN Access Point (AP), or a combined WLAN WT/AP. The WWAN 12 and WLAN 14 may interwork with one another such as via an interface 26 established between WWAN radio access node 20 and WLAN radio access node 24.

[00077] The UE 16 and the WWAN radio access node 20 implement a control signalling plane protocol to transfer control plane signalling for the WWAN 12. This control plane signalling may include for instance radio resource control (RRC) signalling and/or non-access stratum (NAS) signalling. As shown, control plane signalling may be transferred at Layer 3, e.g., for the control of Layer 1 (e.g., physical) and Layer 2 (e.g., medium access control, MAC) in a WWAN radio interface protocol stack. In this and other embodiments, for instance, control plane signalling may involve RRC connection establishment and release, system information broadcast, radio bearer establishment, reconfiguration, and release, RRC connection mobility procedures, paging notification, outer loop power control, and the like.

[00078] According to one or more embodiments, the UE 16 and the WWAN radio access node 20 transfer control plane signalling between one another via WLAN radio access 22 (and via the interface 26 between the WWAN radio access node 20 and the WLAN node 24). As shown, for example, the UE 16 may transmit or receive a control signalling plane message 28 to or from the WWAN radio access node 20 via the WLAN radio access 22. Correspondingly, the WWAN radio access node 20 transmits or receives a control signalling plane message 28 to or from the UE 16 via the WLAN radio access 22, by transmitting or receiving the RRC message 28 via its interface 26 with the WLAN node 24. The WLAN node 24 thereby forwards the control signalling plane message 28 between the UE 16 and the WWAN radio access node 20 via the WLAN radio access 22 and the WWAN- WLAN interface 26.

[00079] In some embodiments, the control signalling plane message 28 is advantageously transferred in this way when the WWAN radio access 18 is unavailable or when no control signalling plane is established over WWAN radio access 18. WWAN radio access 18 may be unavailable for instance when the UE 16 is geographically located outside a radio coverage area of the WWAN 12, when channel conditions for the WWAN radio access 18 are poor to the point of radio link failure, or when any other conditions exist preventing the UE's radio access to the WWAN 12. Of course, even if WWAN radio access 18 is available, a control signalling plane may not actually be established for the user equipment 16 over WWAN radio access 18. Despite the unavailability of WWAN radio access 18 or the lack of a control signalling plane for the user equipment 16 over WWAN radio access 18, though, the UE 16 and WWAN radio access node 20 are still able to transfer a control signalling plane message 28 between themselves, via the WLAN radio access 22. That is, even though the control signalling plane message 28 concerns control plane signalling for the WWAN 12, the control signalling plane message 28 is transferred via the WLAN radio access 22. This effectively decouples transfer of control plane signalling from WWAN radio access 18, so as to for instance make the establishment or continuing of an RRC connection with the WWAN 12 robust to WWAN radio access availability.

[00080] In one or more embodiments, for example, the control signalling plane message 28 includes information for requesting, setting up, re-establishing, reconfiguring, or otherwise managing an RRC connection between the user equipment 16 and the WWAN radio access node 20. In LTE-based embodiments, the control signalling plane message 28 may therefore be an RRC Connection Request, an RRC Connection Setup message, an RRC Connection Re- establishment Request, an RRC Connection Reconfiguration message, or other message for managing an RRC connection.

[00081 ] Consider for instance embodiments (LTE-based or otherwise) where all or part of the signalling for an RRC connection establishment procedure is transferred over WLAN radio access 22. In this case, the user equipment 16 may transmit the RRC connection request message to the WWAN radio access node 20 via the WLAN radio access 22, even though the message requests an RRC connection with the WWAN 12.

[00082] The user equipment 16 may do so selectively, though, based on WWAN and/or WLAN radio access availability. For instance, in some embodiments, the user equipment 16 or the WWAN radio access node 20 selects between the WLAN radio access 22 and the WWAN radio access 18 as the radio access via which an RRC connection request message is to be transmitted by the user equipment 16 to the WWAN radio access node 20, based on availability of the WLAN radio access 22 and the WWAN radio access 18. If for instance WLAN radio access 22 is available but WWAN radio access 18 is unavailable, the user equipment 16 may transmit the RRC connection request message via the WLAN radio access 22. In some embodiments, if WWAN radio access 18 is available, the user equipment 16 preferentially transmits the RRC connection request message via the WWAN radio access 18, even if WLAN radio access 22 is available. In other embodiments, though, the user equipment 16 may compare the signal strength or other radio related measures between WLAN radio access 22 and WWAN radio access 18 and select whichever radio access has better radio related measures, e.g., as being the radio access most likely to remain available. In this and other embodiments, therefore, the user equipment 16 and WWAN radio access node 20 may dynamically switch between WWAN and WLAN radio access for control plane signalling, based on WWAN and WLAN radio access availability.

[00083] Note that, in some embodiments, the RRC connection request message may include an establishment cause or other information indicating that the connection request message is transmitted via the WLAN radio access 22. The user equipment 16 may generate the RRC connection request message in this way so that the WWAN radio access node 20 can continue the RRC connection establishment procedure via the WLAN radio access 22, rather than the WWAN radio access 18.

[00084] In one or more embodiments, for instance, the WWAN radio access node 20 (upon receiving an RRC connection request message from the user equipment 16) transmits an RRC connection setup message to the user equipment 16. That is, the control signalling plane message 28 in Figure 4 may be an RRC connection setup message, e.g., identifying a signalling radio bearer (SRB) and indicating RRC connection configuration parameters.

[00085] Performing all or part of an RRC connection establishment procedure via WLAN radio access proves advantageous in some embodiments for enabling the user equipment 16 to attach to the WWAN 12 (and establish the necessary RRC signalling needed therefore) even when the user equipment 16 is not in radio coverage of the WWAN 12. Additionally or alternatively, it may enable WWAN services (e.g., voice, data, multimedia broadcast-multicast, etc.) to be provided to user equipment that are in unfavourable or even unavailable WWAN radio access, such as when user equipment are in buildings or coverage blind spots.

Furthermore, at a later point when WWAN radio access 18 becomes more favourable or available, the procedure for it to connect to the WWAN radio access 18 may be simplified and/or compressed.

[00086] In other embodiments, irrespective of whether an RRC connection is initially established via WWAN radio access 18 or WLAN radio access 22, signalling for re-establishing or re-configuring the RRC connection may be transferred via the WLAN radio access 22. This may be configured to occur for instance responsive to WWAN radio access 18 becoming unavailable, e.g., suddenly without opportunity for re-establishing or re-configuring the RRC connection via the WWAN radio access 18. Detection of physical layer problems or radio link failure may therefore trigger RRC connection reconfiguration via WLAN radio access 18. Even if RRC signalling had been transferred via WWAN radio access 18 previously, then, RRC signalling would thereafter be transferred via WLAN radio access 22 instead. In this way, the user equipment 16 and WWAN radio access node 20 may dynamically switch signalling for an RRC connection between WWAN radio access 18 and WLAN radio access 22 on an as needed basis in order to maintain and sustain the RRC connection.

[00087] Note that the WLAN node 24 may assist the WWAN radio access node 20 and the user equipment 16 in transferring control plane signalling via WLAN radio access 22. In some embodiments, for instance, the WLAN node 24 advertises its capability to forward control signalling plane messages between user equipment and one or more WWAN radio access nodes via WLAN radio access. A UE detecting and interpreting such capabilities can thus act accordingly and potentially associate and initiate an RRC connection establishment procedure with the WWAN 12 over WLAN radio access 18. The announcement can be done via broadcasting in a WLAN beacon transmission, through an ANQP procedure or prior to or in connection to an association or authentication procedure. In one embodiment, the WLAN node 24 actually advertises which WWAN radio access nodes it is capable of forwarding control signalling plane messages for, such as by advertising one or more WWAN radio access node identities. Further advertising details may also include ,e.g., if a specific PLMN supports SRB and RRC

signalling over WLAN radio access 22. In other embodiments, though, the WLAN node 24 just generally advertises its forwarding capability without specifically indicating WWAN radio access nodes the forwarding is for.

[00088] In fact, in some embodiments, the WLAN node 24 in the WLAN access network 14 is configured by default to forward control signalling plane messages to or from a default WWAN radio access node. This default configuration may be provisioned for instance by an operations and maintenance node in the system 10. The default WWAN radio access node may be chosen by the operations and maintenance node as the WWAN radio access node that the WLAN node 24 is to forward all control signalling plane messages to and from, e.g., irrespective of what particular WLAN Access Point that are used for forwarding control signalling plane messages. Once the WLAN node 24 learns the identity of this default WWAN radio access node, some embodiments implement a DNS or FQDN query procedure to resolve a transport address of this default WWAN radio access node, in order to establish an interface to it. If the WLAN node 24 is not provisioned with the name of the default WWAN radio access node, it may alternatively take a PLMN indicated by the user equipment 16 to perform a Query for a default WWAN radio access node to this PLMN. This default WWAN radio access node may even be dedicated solely for the purpose of connecting WLAN nodes to the WWAN 12 radio access network.

[00089] In other embodiments, the WLAN node 24 may dynamically select which of multiple possible WWAN radio access nodes to forward a control signalling plane message to or from. This selection may be made based on a geographical distance between the WLAN node 24 and the different possible WWAN radio access nodes' respective wireless coverage areas, so as to for instance select the geographically closest WWAN radio access node. Alternatively or additionally, the selection may be based on traffic loads of the respective WWAN radio access nodes, so as to preferentially choose WWAN radio access nodes with lighter traffic loads. In still other embodiments, the selection may instead or also be based on a kind or quality of services provided by the respective WWAN radio access nodes, e.g., in order to select a WWAN radio access node which supports user equipment requirements (e.g., bit rate requirements).

[00090] In these and other embodiments, therefore, the WLAN node 24 may itself trigger or initiate establishment of an interface between the WLAN node 24 and a particular WWAN radio access node 20. That is, interface establishment is initiated by the WLAN node 24, not the WWAN radio access node 20. This may be initiated for instance upon being provisioned by operations and maintenance, or

dynamically responsive to the need to forward control plane signalling. The WLAN node 24 may initiate interface establishment for instance when the WLAN node 24 receives an RRC message from a user equipment 16 for which it does not yet have an a user plane interface towards a WWAN radio access node (e.g., an Xw user plane toward an eNB in LTE embodiments). In this case, the WLAN node 24 may initiate an interface addition procedure (e.g., initiate WT addition in LTE) and forwards the RRC message (e.g., an RRC connection request) to the WWAN radio access node.

[00091 ] In one LTE embodiment, for instance, an eNB receives an RRC connection request coming from the user equipment 16 through the Xw-interface instead of directly through the LTE air interface. In this case, the eNB may determine that the user equipment 16 should be granted an RRC connection, and accepts the RRC connection request by setting up a user equipment context and replying through the Xw interface, thereby setting up the RRC connection through the WLAN radio access 22. All subsequent RRC procedures toward the same user equipment 16 may be transported through the Xw interface.

[00092] Subsequent RRC procedures may include for example measurement configurations in which the eNB may take into account if it knows that there is no WWAN radio access coverage in that area and configure the user equipment 16 with less WWAN radio access measurements. Subsequent RRC procedures may alternatively or additionally include system information forwarding as a dedicated RRC message about intra and inter-frequency measurements, eMBMS, or public warnings.

[00093] In one embodiment, if the user equipment 16 does have WLAN access to a WLAN node that has indicated its capability to forward RRC messages as stated above and it does not have an RRC connection to a WWAN node and is thus in idle state, the paging messages may be forwarded to that user equipment by WLAN radio access. In this case, the user equipment 16 may not be required to be camping on an e.g. LTE cell as it may be that WLAN radio network operates as a coverage extension to the WWAN network.

[00094] Note that in at least some embodiments the user equipment 16 may exploit the ability to transfer control plane signalling via WLAN radio access 22 for various purposes. In one embodiment, for instance, the user equipment 16 scans for WWAN radio access less often when a control signalling plane is established over the WLAN radio access 22 than when no control signalling plane is established over WLAN radio access 22 or WWAN radio access 18. For example, the user equipment 16 may scan for WWAN radio access less often when WWAN radio access 18 is unavailable but the user equipment 16 has an RRC connection with the WWAN radio access node 20 via the WLAN radio access 22 (and an Xw- interface) than when WWAN radio access 18 is unavailable and the user equipment 16 does not have such an RRC connection.

[00095] The specifics of if a different scanning procedure for WWAN should be executed may either be initiated from the network, e.g., by way of a new signalling message from RRC, or it could be determined within the user equipment 16, or from a combination of indications from the network and user equipment decision. For example, in a situation when an RRC connection is established to an eNB (WWAN) over WLAN and Xw-RRC, the eNB/RRC may signal a scanning reduction indication allowing the user equipment 16 to reduce its search for an LTE eNB signal. The indication could be an offset from how the scanning would be performed if there was no RRC connection established at all. Alternatively, as it is the user equipment 16 that performs the scanning, it may decide on its own how to handle scanning for an LTE eNB signal/cell. To support such decision, it may be possible to use, e.g., the WLAN performance (such as signal strength, a throughput estimate, a delay estimate or similar) to assess, e.g., how reliable the WLAN connection is and that may determine a scanning behaviour to find a WWAN/LTE connection. In addition, a user equipment 16 may also scan more or less actively for an LTE connection dependent on battery level and the existence of an RRC connection to WWAN over WLAN. Thus, if there is an RRC connection over WLAN and the battery level in the user equipment 16 is low, this may also be a factor determining how active and/or frequent the scanning for an LTE cell should be.

[00096] In any event, the user equipment 16 may therefore in some embodiments exploit the fact that it has an RRC connection via WLAN radio access in order to minimize or at least reduce its WWAN radio access scanning. This may in turn conserve power and/or optimize battery performance at the user equipment 16.

[00097] In fact, in some embodiments, the WLAN node 24 may be configured to transmit signalling via the WLAN radio access 22 indicating availability of the WWAN radio access 18. In this case, the user equipment 16 may delay its attempts at WWAN radio access 18 until the user equipment 16 receives such signalling. Consider for instance a scenario where the WLAN 14 spans across multiple radio access nodes or coverage areas, some of which are overlapping with WWAN radio coverage, while others are not (e.g., a multi-floor building where WWAN coverage is only available outside the building and on the high floors). In this case, when the user equipment 16 enters the WLAN coverage area of a WLAN radio access node which has overlapping coverage with the WWAN 12, that WLAN radio access node may notify the user equipment to scan for WWAN radio access. In some embodiments, the WLAN node may also provide the user equipment 16 with any neighbour relations or other information needed to perform such scan (e.g., in order to limit search space). This signalling may be provided via RRC or be part of neighbour relation information known to the WLAN network nodes or the WT or some other method. [00098] As a general matter, therefore, the user equipment 16 may be configured to operate differently depending on whether the user equipment 16 has an RRC connection over WLAN. In some embodiments, this distinction is embodied in the form of different RRC connected states associated with different radio access types (WWAN or WLAN) via which the user equipment 16 has an RRC

connection. For example, in one embodiment, the user equipment is configured to operate in a WLAN RRC connected state when the user equipment 16 has an RRC connection over WLAN radio access 22 and to operate in a WWAN RRC connected state when the user equipment 16 has an RRC connection over WWAN radio access 18. The WLAN RRC connected state and the WWAN RRC

connected state may thus be managed with different parameters. For example, the WLAN and WWAN RRC connected states may have different parameters governing how long the user equipment 16 is to stay in the respective RRC connected states, which default bearer is to be established, or the like. In one embodiment, the user equipment 16 preferentially operates in WWAN RRC connected state, such that it only operates in the WLAN RRC connected state if and when WWAN radio access 18 is unavailable.

[00099] In still other embodiments, by contrast, the user equipment 16 operates in the same RRC connected state irrespective of whether the RRC connection is established over WWAN radio access 18 or WLAN radio access 22, i.e., only an RRC connected state is defined, not both a WWAN RRC connected state and a WLAN RRC connected state. This RRC connected state may correspond for instance to the LTE-based RRC connected state specified in 3GPP TS 36.331 .

[000100] Thus, once the RRC connection establishment procedure is executed over WLAN, the UE is in E-UTRA RRC connected state and the state handling of the UE will follow the procedures similar to what is done for UE's that are in E- UTRA RRC Connected state when establishment occurred over LTE/WWAN. Once in this RRC Connected state, a default bearer will be established and various timers will support management of how long a UE should stay in RRC connected mode, e.g., governing how long a UE should stay in the RRC

connected state. In one embodiment, the timers used when there is no LTE/WWAN connection are different from the timers used when there is an LTE/WWAN connection available. Alternatively, the same set of timers will be used.

[000101 ] Alternatively, a rule may be applied that if a UE only has a WLAN connection it will be set in a new WLAN-RRC Connected state where connection management is governed by a specific set of timers and timer values, but as soon as an LTE/WWAN link is added/available, the UE will be transferred to the RRC Connected state, with new timers according to timers applicable for the

LTE/WWAN connection management. This aspect proposes to include a new state for UEs that are connected in an LWA configuration with only a WLAN connectivity option available. Examples of a few parameters or timers that may or may not take different values dependent on whether the RRC connection is realized over WLAN only or also over WWAN/LTE may be, e.g. modifications or originals of the already specified, T301 -controlling

RRCConnectionReestablishments, T304-controlling

RRCConnectionReconfigurations or T310- controlling radio link failures, but other parameters may also equally well be configured to be different, or even have interpretations that are specific to WLAN, when RRC connection is realized over WLAN.

[000102] In either case, though, the user equipment 16 may not leave an RRC connected state unless both WWAN radio access 18 and WLAN radio access 22 are lost or due to inactivity. This may be for instance because the WWAN radio access coverage is lost and the user equipment 16 becomes disassociated from the WLAN 14. In this case, in one embodiment, the user equipment 16 attempts to send a radio link failure indication to WWAN using WWAN radio interface if possible. In another embodiment, WLAN radio access needs to send a radio access failure indication for that user equipment 16 to WWAN radio access 18.

[000103] Note that the control signalling plane message 28 may be transferred between the user equipment 16 and the WWAN radio access node 20 via the WLAN radio access 22 using any of a number of possible approaches. In some embodiments, for example, the control signalling plane message 28 is encapsulated over WLAN. For instance, as shown in Figure 5 for a control signalling plane message 28 in the form of an RRC message 28A, the RRC message 28A may be generated by an RRC layer 30 of a WWAN protocol stack 32 and then transmitted over either a WWAN radio access stack 34 or a WLAN radio access stack 36. When transmitted over the WLAN radio access stack 36, the RRC message 28A is encapsulated by a WLAN tunnelling layer 38 in order to tunnel the RRC message 28A through the WLAN radio access stack 36. This encapsulation may involve for instance wrapping or otherwise packaging the RRC message 28A for transmission over WLAN radio access layers. The encapsulated RRC message 28A upon receipt may then be de-encapsulated from radio access layers of the WLAN protocol stack and returned back to the WWAN protocol stack.

[000104] Note that, although not illustrated in Figure 5, the RRC message 28A may traverse one or more intermediate layers before being processed by the WLAN tunnelling layer 38. In some embodiments, therefore, the WLAN tunnelling layer 36 may be implemented directly adjacent (e.g., below for transmission and above for reception) the RRC layer 32 that generates the RRC message 28A. In other embodiments, though, the WLAN tunnelling layer 36 may be implemented directly adjacent an intermediate layer between the RRC layer 32 and the WLAN tunnelling layer 38.

[000105] Consider for instance some embodiments where the WWAN is an LTE network which is integrated with WLAN according to a solution referred to as LTE-WLAN Aggregation (LWA). In this case, the WLAN tunnelling layer 38 may be an LTE-WLAN aggregation (LWA) adaptation protocol (LWAAP) layer. The

LWAAP layer is therefore extended to not only transfer user plane data via WLAN, but also control plane data, e.g., in the form of RRC signalling.

[000106] In more detail, Figure 6 illustrates an exemplary system view

according to some LWA embodiments. A UE 410 communicates with a WWAN radio access node in the form of an eNB 420 over an LTE air interface 415 or a WLAN AP 430 over a WLAN air interface 425. The WLAN AP and the eNB are interconnected, through a WLAN termination point (WT) 440. The interface between the WT 440 and the eNB 420 is called Xw interface 445. It should be noted that connectivity between the WT and the AP is obviously needed, but the interface between these two entities are not further specified. In some

deployments, it could be the same physical entity.

[000107] The eNB is further connected to a Serving Gateway 450, through an S1 -U interface 455 and to an MME 460 through an S1 -MME interface 465. The Serving gateway is connected to a Packet Gateway, PGW 470 that provides connectivity to, e.g., the internet. The WLAN AP may also be connected to an ePDG 480 for providing access to the PGW 470 and internet in a similar way as when accessed via an eNB. This connection is called S2b 485 between the ePDG 480 and the PGW 470 and the interface from the AP to the ePDG is called SWn 495. Further details about the interfaces are found in 3GPP TS 24.302.

[000108] On the network side, the eNB used to be referred to as E-UTRAN and the MME, SGW and PGW used to be referred to as EPC-Evolved Packet Core. The functionality of the eNB is for example Radio Bearer control, admission and connection mobility control. The Protocol layers in the eNB are RRC, PDCP, RLC, MAC and PHY. The MME 460 is the control node for LTE access, responsible for, e.g., idle mode UE's (for example paging). It is also involved in bearer activation / deactivation process and for choosing an SGW for a UE in an initial attach procedure and authentication towards a Home Subscriber Server and AAA nodes (these are not illustrated). The MME is also responsible for allocation of identities to the UE. The SGW 450 routes and forwards user data packets and is also acting as a mobility anchor for the user plane during, e.g., handovers between different eNB's. For idle state UEs the SGW triggers paging when downlink data arrives for a UE. It manages and stores UE contexts, e.g., parameters for bearer service, routing information. The PGW 470 provides connectivity to external packet data networks acting as a point of entry/exit for all the traffic going to/from the EPC. The PGW also performs policy enforcement and packet filtering for users and provide charging support. The ePDG, evolved Packet Data Gateway 480 secures data transmission to untrusted networks, such as, e.g., WLAN. It acts as a termination node of IPsec tunnels established with the UE. [000109] Figure 6 illustrates two different ways of connecting to a wireless communication network and its packet gateway 470 from WLAN. Either through a solution based on LWA aggregation and connectivity via an eNB or directly through an ePDG and to the PGW. In the following, focus will be on the solution that utilizes LWA aggregation.

[0001 10] Figure 7 illustrates further details of eNB and the UE and E-UTRAN (WWAN) protocol layers and more specifically, the user plane protocol stack for user data traffic.

[0001 1 1 ] The PDCP protocol 510, 520 in Figure 7 illustrates the user plane protocols used for WWAN user data traffic. This protocol level is specified in 3GPP TS 36.323. The PDCP protocol includes services to upper layers such as transfer of user plane data, header compression, ciphering and integrity protection. A PDCP allow for a lower layer acknowledged or unacknowledged data transfer, in- sequence delivery and duplicate discarding.

[0001 12] The RLC protocol layer 530, 540 is further specified in 3GPP TS 36.322 and supports transmission of acknowledged or unacknowledged data transfer including indications of successful delivery of upper layer PDU's (Packet Data Units). To this end, RLC includes error correction, concatenation,

segmentation and re-segmentation for AM data transfer, reordering, duplicated detection, discard, RLC re-establishment and protocol error detection.

[0001 13] The MAC layer 550,560 provides support for data transfer and for notifying higher layers about transmission opportunities. Functions included in MAC are for example multiplexing of MAC Service Data Units SDP's from one or different logical channel onto transport blocks, scheduling information reporting, error correction through HARQ, priority handling, scheduling and transport format selection (modulation and coding).

[0001 14] The PHY layer 570,580 provides resources for data transfer, signalling of HARQ feedback, signalling of scheduling requests and

measurements. [0001 15] Figure 8 is a corresponding figure to Figure 7, but for the control plane, i.e., the signalling.

[0001 16] The NAS layer incorporates signalling to higher layers outside of E- UTRA, i.e., to the core network. This is transparent to the eNB in that it is encapsulated in a signalling radio bearer and not interpreted by the eNB. The RRC 608,609 is the Radio Resource Control layer, responsible for signalling between the UE and the eNB. This layer is specified in 3GPP TS 36.331 . The signalling radio bearers are only used for transmission of RRC and NAS messages. The service provided to higher layers are broadcast and control information

transmission, notification of UE's in RRC idle, and transfer of dedicated control information.

[0001 17] SRB's may also enjoy PDCP integrity protection and ciphering from PDCP and reliable in sequence transfer of information from RLC.

[0001 18] There are different types of Signalling radio bearers, SRBs.

[0001 19] SRB0 is for RRC messages using a common channel. SRB0 is used before security procedures are passed. SRB1 and SRB2 are always used after security is activated.

[000120] SRB1 is for RRC messages using a dedicated channel.

[000121 ] SRB2 is a lower priority version of SRB1 , e.g., including logged measurement information and NAS messages.

[000122] Among the functions included in RRC are for example broadcast of system information, RRC connection control including establishment modification and release of RRC connections and Signalling Radio Bearers (SRBs) and data Radio bearers (DRBs) for user data, initial security activation, measurement configuration and reporting, mobility procedures, QoS control, recovery from failure and much more.

[000123] Figure 9 illustrate a state diagram with two different RRC states, applicable for UE's that are attached to the EPC. [000124] In RRC connected state 710, transfer of data is possible and the network controls the mobility through handover functionality, cell change orders etc. Thus, the E-UTRA eNB is aware of the UE and maintains a UE context in the eNB. The UE monitors a paging channel and listen to System information to detect system information change and the UE will also provide channel quality and feedback information.

[000125] In RRC Idle state 720, it is the UE that controls the mobility and no transfer of data is possible, since the UE is not known in E-UTRAN/eNB. It is however known in EPC and it has an IP address. The UE still monitors a paging channel to detect incoming calls, system information change etc. and it performs measurement and cell re-selection. An MME may initiate paging in a large area (Tracking Area) for downlink data transmission.

[000126] Returning now to LTE-WLAN Aggregation, LWA, E-UTRA supports LWA whereby a UE in RRC connected state may be configured by the eNB to utilize radio resources of both LTE and WLAN. The overall architecture is illustrated in Figure 1 , as described above. It should be noted that a WT 130 could be connected to more than one eNB 1 10 and one and the same eNB 1 10 may be connected to several WT 130. Figure 2 and 3 illustrate the protocol architecture for LWA including indications 275 for what parts that belong to the eNB logical node and what parts that belong to the WLAN access point logical node.

[000127] The WT 130 is connected to the eNB via an Xw interface 120.

Implementation of WT-to-WLAN AP is implementation specific and may, e.g., be solved by integrating the WT with a WLAN controller entity that connects to several WLAN APs 150.

[000128] As illustrated in Figure 2 and 3 of the different protocol layers specified for LWA operation, the LWA AP protocol layer is illustrated.

[000129] Figure 10 further illustrates the LWA AP protocol layer in the eNB 1001 and in the UE 1002. One function of LWAAP is to provide transfer of user plane data (LWA AP SDU's) and to be able to identify LWA bearers and to which particular LWA AP SDUs belong. At the eNB and for downlink communication, the LWA AP entity receives LWAAP SDUs from upper layers and constructs a corresponding LWA AP PDU and delivers it to lower Layers. Correspondingly for the UE, the LWA AP entity will receive LWAAP PDU's from lower layers and reassemble corresponding LWAAP SDU's and deliver it to higher layers. A corresponding procedure would be executed for uplink communication, but the roles of the eNB and the UE would be reversed. As can be recognized, the

LWAAP essentially adds an identifier to the incoming LWAAP SDUs. The identifiers are, for downlink communication, added 1030 in the LWAAP entity on the eNB side 1010 and removed 1040 in the LWAAP entity on the UE side 1020.

[000130] The LWA AP data PDU 1 100 is illustrated in Figure 1 1 . The PDU consist of a header 1 120 with three reserved bits 1 101 , 1 102, 1 103 and an identity field, DRB ID 1 1 10. The reserved bits are not used and the DRBID field indicates the DRB identity to which a corresponding LWAAP SDU belongs. The DRB ID field is 5 bits.

[000131 ] The Xw interface consist of a user plane / data portion Xw-U and a control plane portion, Xw-C. The Xw-U interface is used to deliver LWA PDUs between the eNB and the WT and the Xw-C protocol (called Xw-AP protocol) is used for transfer of WLAN metrics from WT to eNB, for establishment, modification and release of a UE context at the WT, for control plane and user plane tunnels between the eNB and WT and for general handling over the interface, e.g., error indications, setting up and resetting the Xw interface.

[000132] On the WLAN-side, a mobility set is defined. A mobility set is a set of one or more WLAN Access Points within which WLAN mobility mechanisms apply while the UE is configured with LWA bearers, i.e., the UE may perform mobility between WLAN APs belonging to a mobility set without informing the eNB about it. It is however the eNB that provides the UE with information about the WLAN mobility set. When the UE is configured it will attempt to connect to a WLAN whose identifiers (BSSID/HESSID/SSID) match the ones of the configured mobility set. All AP's that belong to a mobility set share a common WT, which terminates the Xw-C and Xw-U interface. [000133] Figure 12 illustrates how a WT is added. The eNB decides to request the WT to allocate WLAN resources for a specific user, indicating the

characteristics of the request in a WT addition request 910. If the WT is able to admit the resource request, it responds with an acknowledge message 920. The eNB then sends an RRCConnectionReconfiguration message to the UE 930, including in the message the new radio resource configuration. The UE then applies this new configuration and replies with RRC connection reconfiguration complete 940. After this, the UE performs the WLAN association to a WLAN Access point after which the configuration is ready for use. The WT then sends the WT association confirmation message 950 and if configured, the UE start to report the WLAN connection status to the eNB, e.g., for purposes of routing or further reconfiguration. The procedures related to further actions over the Xw interface and for setting up, releasing and modifying the WT is found in 3GPP TS 36.300.

[000134] According to one or more embodiments herein, LWA is extended to not only transfer user plane data via WLAN, but also control plane data. RRC signalling is established or reconfigured to be transmitted over the WLAN part of LWA by being encapsulated in an LWA bearer. At least some embodiments, therefore, allow a UE to attach to the LTE network (and establish the necessary RRC signalling needed therefor) even when the UE is not in LTE coverage. The embodiments may for instance utilize the WLAN network to encapsulate the necessary RRC signalling towards the LTE network.

[000135] Alternatively or additionally, embodiments herein facilitate continuing an ongoing LWA connection even in situations when LTE coverage is lost (e.g., upon entering a building with only WLAN radio coverage). RRC signalling may be moved from being transmitted over LTE to being transmitted over the WLAN part of LWA, by being encapsulated in an LWA bearer. Accordingly, communication towards a 3GPP network may continue, even in situations when LTE coverage is lost. The RRC anchoring and UE context may be kept in the eNB so that this is transparent to the evolved packet core (EPC) and to the rest of the radio access network. Significant impact may therefore be limited to RRC routing inside the eNB and UE, such that this functionality may be implemented without any change to the Rel-13 LWA architecture.

[000136] In some embodiments, a UE may even provide radio measurements to the eNB despite being outside of LTE coverage. This may be particularly beneficial in conjunction with SON functionality in order to provide additional information about problematic areas.

[000137] Figure 13 shows details of the eNB, UE, and E-UTRAN protocol layers for the control plane according to some of these embodiments that extend LWA to the control plane. Contrasted with the protocol layers of Figures 2, 3, and 8, those in Figure 13 include an LWA AP layer 835 on the UE side that may transmit/receive an RRC message directly to/from the RRC layer 808 or indirectly via the PDCP layer 810. Correspondingly, the LWA AP layer 845 on the eNB side may transmit/receive an RRC message directly to/from the RRC layer 818 or indirectly via the PDCP layer 820. Direct interaction with the RRC layer (i.e., between the LWA AP layer and the RRC layer) may occur for instance prior to RRC connected mode (e.g., for SRB0) whereas indirect interaction (between the LWA AP layer and the RRC layer) via PDCP may occur after RRC connected mode (e.g., for SRB1 and 2)

[000138] With the protocol stacks configured in this way, Figure 14 illustrates one or more embodiments for establishing an RRC connection with an LTE eNB via WLAN radio access, even when LTE radio access is unavailable. As shown, initially, a WT 1430 has an existing Xw control plane signalling interface

established with an eNB 1440 (or sometimes multiple eNBs) (Step 0). There are several reasons why the connection could have been established: the WT 1430 could already have UEs that have LWA enabled with this particular eNB 1440, or some eNB transport address could have been pre-provisioned in the WT 1430 (possibly via an O&M system). The procedure for Xw setup already specified in 3GPP TS 36.463 can be reused to establish an Xw between a WT 1430 and an eNB 1440. This procedure is currently eNB-initiated, but as described herein may be WT-initiated instead. This Xw procedure is non-UE-specific. [000139] In order for the UE to know that a certain AP/this WLAN network supports encapsulating LTE RRC over WLAN signalling, the WLAN AP 1420 may advertise a beacon or probe to the UE 1410 (Step 1 ). This advertisement may include "RRC Connection encapsulation" capability and possibly a Global eNB-ID (which also includes the PLMN identity). The Global eNB-ID belongs to the same eNB to which the WT 1430 has already existing control plane signalling. This may be an eNB that normally serves traffic using LTE carriers, or alternatively, it may be a dedicated eNB entity, e.g., solely for purposes of connecting WLAN AP's to the 3GPP RAN. It could also be part of an eNB deployment with a centralized eNB entity serving one or several eNB coverage areas. The WLAN AP 1430 may use the "3GPP Cellular Network" ANQP-element (see 3GPP TS 24.302, Annex H) for the advertisement, or there may be a newly introduced information element (IE) that carries the information, then specified in the IEEE 802.1 1 specification. Either broadcast or unicast signalling may be used for the purpose. Some example means to implemented those are (but not limited to): Beacon frame, Fast Initial Link Setup Discover frame (FILS-DF), Generic Advertisement Service (GAS), Access Network Query Protocol (ANQP), Probe Request/Response frames, etc.) In case there are many eNBs attached to a WT the selected id may be based on which eNB is nearest eNB from a geographical coverage sense and/or based on traffic load in eNB and/or based on what kind of services are provided in the eNB (e.g. bit rate capabilities etc.). The WT1430 may make the choice if no specific eNB id was signalled to the UE or it may also select another eNB if so required based on load etc. It may also be that the chosen eNB cannot provide a service and rejects WT addition, meaning that the WT 1430 may choose a new eNB if available. The WT 1430 in this regard may make several requests of information to eNBs connected to it, for example to learn if the UE has been recently connected to that eNB.

[000140] As further shown in Figure 14, the UE 1410 may transmit an Open System Authentication (OSA) towards the WLAN access point 1420 (Step 2). The IEEE 802.1 X control port in this regard may be blocked and allow only particular types of frames to be sent by the UE to the AP (in this particular case those are either authentication frames or encapsulated RRC frames). The encapsulated RRC frames may be distinguishable also by an AP, e.g., as a combination of content and Ethertype used.

[000141 ] In Step 3 of Figure 14, the UE 1410 sends an RRC Connection Request to the WLAN AP 1420, i.e., via WLAN radio access. The RRC

Connection request may be coded in a similar way as is described for

transmission over LTE according to the 3GPP TS 36.331 specification, i.e., including an identity and/or a random value together with an establishment cause. In some embodiments, though, a new establishmentCause indicates to network RRC layer that the message is transmitted over WLAN radio access. On the UE side, the RRC connection request originates from the RRC layer sent to the LWAAP sublayer, where an identity may be added, that is a recognizable signalling bearer identity also to the LWAAP sublayer on the network side. In any event, the WLAN AP 1420 forwards the RRC Connection Request to the WLAN Termination function 1430 (Step 3b). The WLAN has already existing association with the WT 1430. Recognizing traffic going to the WT may for example be solved by using the previously introduced Ethertype for LWA.

[000142] In Step 4, the WT 1430 triggers an Xw WT-lnitiated WT Addition Preparation in order to establish the signalling needed to encapsulate the RRC Connection Request from the UE 1410. The RRC traffic encapsulated over Xw is hereon referred to as Xw-RRC. The WT 1430 already has control plane signalling to a particular eNB 1440 so this is the eNB to which it sends the Xw WT Addition Request. The WT-lnitiated WT Addition Preparation procedure may be specified as shown in Figures 15-17.

[000143] Figure 15 shows one example of a WT Addition Request sent from the WT 1430 to the eNB 1440 to request the addition of LWA bearers for a specific UE (Step 4). Notice that the SRB Indication IE indicates that the requested E-RAB contains an SRB for the UE and should therefore be terminated in the eNB.

[000144] If the eNB 1440 is able to accept at least one of the requested bearers, it replies with a WT ADDITION CONFIRM message as its response (Step 5). Figure 16 illustrates one example of such a message informing the WT 1430 that the WT initiated WT Addition Preparation was successful.

[000145] If on the other hand the 3NB 1440 cannot accept any of the requested bearers, it will respond with a WT Addition Refuse message. Figure 17 illustrates one example of such a message informing the WT 1430 that the WT initiated WT Addition Preparation has failed.

[000146] In the alternative, the WT 1430 may be provisioned with a "default" eNB (per PLMN) address, to which all requests are to be sent. If there are various options to forward the RRC Connection requests to different eNB's, there may even be re-tries, e.g., as indicated in step 2 above.

[000147] Once the Xw-RRC is established, the WT 1430 forwards the RRC Connection Request message (encapsulated) that it had previously received from the UE (Step 3c in Figure 14).

[000148] The eNB 1440 responds to the UE 1410 with a RRC Connection Setup over the Xw-RRC using the same identity as was indicated by the RRC connection request message (Step 7). This RRC response is routed directly from RRC on the network side, through the LWAAP back to the WT 1410 over Xw. The LWAAP maintains the association between the specific WT 1410 from where the message originates and the specific request identity used during the RRC connection request procedure.

[000149] In step 7, the UE responds with a RRC Connection Setup Complete in a similar way as if the message sequence was executed over LTE radio access, using the now already established connection to the eNB 1440. This is the first message that is sent over a dedicated channel, i.e., the SRB1 .

[000150] In step 8, the UE performs the regular E-UTRAN attach procedure as specified in 3GPP TS 24.301 , now using the WLAN connection as air interface. Once the UE completes the E-UTRAN attach procedure, the LWA is activated by the eNB (as described in 3GPP TS 36.300) (Step 9). At this point, the UE 1410 also completes the authentication procedure with the WLAN network (based on the LWA authentication principle) and the data over both the cellular and WLAN links is encrypted.

[000151 ] In an alternative embodiment, already in step 7, the connection between the UE 1410 and the network is established in an LWA mode, i.e., in the connection setup message, the configuration that is communicated to the UE 1410 via the radioresourceconfig Dedicated IE already includes a configuration for setting up the SRB in a new "LWA" mode. This means then that the attach procedure is conducted when already in LWA mode.

[000152] In any event, with LWA extended to facilitate RRC connection establishment via WLAN radio access, LWAAP according to some embodiments is extended to communicate directly with the RRC layer, rather than just the PDCP layer. This is because certain RRC messages for RRC connection establishment, such as RRC Connection Request and RRC Connection Step, do not traverse the PDCP layer over SRB0. Some embodiments therefore do not forward certain RRC messages to PDCP but instead transfer them towards RRC directly.

[000153] RRC messages that should be routed to PDCP may be distinguished from RRC messages that should be transferred to RRC directly in any number of ways. In one embodiment, for example, these RRC messages are distinguished with identifiers (e.g., in the LWAAP headers) indicating the radio bearer over the messages are sent (e.g., SRB0 or SRB1 ). In another embodiment, the RRC messages are distinguished using reserved bits (e.g., bits 1 101 , 1 102, 1 103 in Figure 1 1 ) to indicate to LWAAP the type of RRC message and/or the type of SRB over which it is transmitted (e.g., SRB0). This is indicated in Figure 29, with the reserved bits (2901 , 2902, 2903) being used for indicating signalling bearer type, (R or D/C), for example in particular SRB0 (as indicated being 2903), that should be routed directly to RRC and not to PDCP. It should be noted that even though all reserved bits are illustrated as being used to indicate signalling/control plane bearers (via the R or D/C indication), it may very well only be one or two of the reserved bits that are used, e.g., for indicating SRB0 in particular, or for indicating that a particular bearer identity addition (1030/2870) identifies an SRB (e.g., SRB1 or SRB2). Thus, one of the reserved bits may be used to further specify bearer identity type. Different options are possible. It may even be possible to extend the bearer identity field and reserve certain values for signalling radio bearers of different or particular types. Including a specific bearer ID or other indication in this way enables the recipient to correctly identify and route the RRC message.

Indeed, once an RRC message is received, the LWAAP may detect the indication that the message is RRC signalling that should be forwarded to RRC directly and instead of routing to PDCP, it is routed directly to RRC.

[000154] Figure 28 and 29 illustrate example embodiments of implementation of SRB support over LWA AP. In Figure 28, SRB bearer identities may be added/removed (2870/2880) in a similar way as DRB bearer identities. Figure 28 also illustrate that the bearers handled by LWA AP may both be SRB0 coming directly from RRC or SRB1 where upper layer is PDCP. When the RRC message is an RRC Connection Request, the eNB may respond to that RRC message with an RRC Connection Setup message which may be returned via the same path as the request was received, i.e., through the LWAAP layer. Thus, on the RRC layer, it should be possible to detect that an incoming message is transmitted over WLAN and the response message (e.g., RRC connection setup) should be returned the same path as the request was received. For this purpose, an indication from LWA AP may for example be forwarded to RRC, or the RRC message itself may include a new indication for indicating that the message has been transmitted over WLAN. Such an indication would then be set already by the transmitting side, e.g., the UE in case of an RRC connection request message. One example of such an RRC message is the RRC connection setup request message, transmitted from an UE to an eNB. If this message is sent utilizing WLAN connectivity to a WLAN AP, a new establishment cause may be defined, where the establishment cause indicates to an eNB RRC protocol level that a certain request has been transmitted over a WLAN connection. In one, this establishment cause is added by the UE.

[000155] It should be emphasized that once the first two messages of the RRC connection establishment procedure are exchanged and the configuration for a dedicated signalling bearer, SRB1 is communicated, the PDCP sublayer is traversed and the mechanisms for separating control from data on PDCP may be used. Thus, the RRC connection setup complete message may traverse PDCP with already specified behaviour on PDCP and RRC level.

[000156] The WLAN network (WLAN AP and WT) may route encapsulated RRC signalling in a corresponding manner. In order to differentiate the RRC signalling from the other types of data carried by the WLAN network, a new protocol identifier may be allocated by the Internet Assigned Numbers Authority, IANA, (similarly to what is currently used for PDCP) or the same Ethertype could be used as is already specified for LWA in Release 13/14.

[000157] Embodiments herein also contemplate encapsulating RRC signalling over WLAN even if the RRC connection is initially established over LTE air interface. Such RRC signalling may concern for instance RRC connection re- establishment or reconfiguration.

[000158] Consider for instance a UE that is engaged in an RRC connection over LTE. The UE may be requested to report WLAN measurements to the eNB. When the measurements fulfil certain criteria, the LTE only connection may be reconfigured to an LWA configuration. This procedure is triggered by the eNB transmitting an RRC Connection Reconfiguration Request message to the UE to add WLAN access. The LTE connection will be re-configured to add an LWA connection, e.g., a split bearer connection.

[000159] The sequence for this was illustrated in Figure 12. Prior to the RRC Connection Reconfiguration, the eNB has also communicated with the WT to negotiate resources for the incoming WLAN aggregation connection. On the PDCP level, routing of packets on either WLAN or LTE will now occur. In this situation, all RRC control plane signalling (i.e., SRB1 and SRB2) occur over LTE. The LWAAP layer, with the task to handle different bearers for WLAN aggregation is handling the bearer identities, e.g., as illustrated in Figure 10.

[000160] If the LTE coverage/connection deteriorates, this may be detected in the UE and the eNB and at some point this deterioration triggers yet another reconfiguration procedure. This time the reconfiguration is such that there may not necessarily be a change of configuration for the LWA data radio bearers, but the signalling radio bearers may be moved from an LTE-only to an LWA configuration mode. In this case, typically the UE will provide measurements to the eNB where e.g. one or more WLAN APs are very strong but no LTE cells are strong enough to allow LTE mobility.

[000161 ] If there is still sufficient (but likely deteriorating) LTE coverage, the reconfiguration of the signalling radio bearers may follow a similar procedure as reconfiguration of already existing data radio bearers. For the data radio bearers, the following is specified in 3GPP TS 36.331 :

LWA specific DRB addition or reconfiguration

For the drb-ldentity value for which this procedure is initiated, the UE shall:

... if the DRB indicated by drb-ldentity is not an LWA DRB (i.e. LTE only to LWA

DRB):

> reconfigure the PDCP entity in accordance with the pdcp-Config, if included in drb-ToAddModList;

> reconfigure the RLC entity and/ or the DTCH logical channel in accordance with the rlc-Config and logicalChannelConfig, if included in drb- ToAdd Mod List;

> enable the LWAAP entity which handles reception of data from WLAN for this DRB;

[000162] According to some embodiments, a similar procedure may be executed also for SRB1 and SRB2 and their respective identities (srb-ldentity) will be included in an srb-ToAddModList for SRB reconfiguration.

[000163] In order to establish the bearer over Xw in the WLAN, the eNB needs to trigger an eNB-lnitiated WT Modification Preparation procedure (according to TS 36.463 Sec. 8.9) adding the new bearer which contains the RRC signalling. If the WT replies with the WT MODIFICATION REQUEST ACKNOWLEDGE, the new LWA bearer has been established.

[000164] To be able to distinguish the SRB's from the DRB's, e.g., over the Xw interface, an indication similar to what is present in PDCP headers (D/C= Data/Control bit) could be included in the first Reserved bit of the LWAAP header, and in case the header indicates control, the same srb identity could be used as is used by PDCP, i.e., the SRBID. As indicated above, and in connection to Figure 28 and 29, similar constructions as described in connection to other embodiments may be used.

[000165] This information can be signalled in addition to the other E-RAB- related lEs in the WT MODIFICATION REQUEST message from the eNB. Figure 18 illustrates one example message structure. As shown, the SRB Indication IE may be defined as the first octet of the LWAAP data PDU as defined in TS 36.360 Sec. 6.1 .2, in which case it would take the form OCTET STRING (SIZE(1 )).

[000166] In an alternative, the SRB indication may also be implicit, by using a "dummy" value for the E-RAB ID signalled in the E-RAB ID IE. In this case, the WT MODIFICATION REQUEST message structure would not be impacted, but an extension of the E-RAB ID IE (defined in TS 36.463 Sec. 9.2.18) may be required as it is currently limited to 16 possible values. Now, both the SRBs and the DRBs are in LWA mode. The RRC entities in the eNB and the UE will route all messages over the newly established LWA bearer instead of Uu (the LTE air interface),

[000167] If the LTE coverage further deteriorates, and ultimately is lost, this may be treated in a number of different ways.

[000168] As a first option, nothing may be done. It will just be accepted that the connection is lost and all traffic and signalling is routed over WLAN. This would in essence mean that the configuration is still considered to be an LWA

configuration, but it would not be possible to route anything over LTE.

[000169] Another option perform yet another RRC connection reconfiguration, now to a WLAN only mode (this is a new mode that is currently not existing in the 3GPP specifications, but with the same consequences, that it is not possible to route anything over LTE). [000170] With the changes proposed above, it will be possible to put also a signalling radio bearer in an LWA mode, and also possible to distinguish this from DRB's and LWAAP PDU's to lower layers.

[000171 ] In an alternative embodiment, the LTE coverage may drop suddenly and there is no possibility to communicate the RRC Connection Reconfiguration messages. In such scenarios, when there already is at least one DRB that is configured for LWA, it may be possible to send the RRC Connection

Reconfiguration message (with the new Radio Resource configuration) directly over WLAN. The trigger for this may be a detection of physical layer problems or radio link failure etc.

[000172] In one embodiment, upon detection of physical layer problems, this may work as a trigger for also establishing SRBs in an LWA mode according to above.

[000173] Alternatively, in any situation when there is at least one DRB in LWA mode, the SRBs are always configured in LWA mode, but routing is generally done on LTE side, unless there are physical layer problems.

[000174] It should be noted that the UE may not leave the RRC_Connected state in a situation when the SRBs can be handled on both WLAN and LTE, until both connections are lost. This may, e.g., be the result of that LTE coverage is lost and the UE is disassociated from WLAN.

[000175] In some embodiments, routing rules are added in an eNB or a UE for transmission of RRC information when both LTE/WWAN as well as WLAN connectivity is possible or available. In particular, all RRC information is routed over LTE/WWAN as soon as LTE/WWAN connectivity is present. In another embodiment, at least portions of RRC signalling are sent over WLAN connection also in the presence of both LTE/WWAN and WLAN coverage. For example, signalling that is considered to be high-priority or urgency signalling may be transmitted on the link that is assessed to be the most robust link, whereas signalling that is considered to be of lower priority or lower urgency may be transmitted over a link that is assessed to be less robust. This could be of particular importance in high-load situations. If for example an LTE node or cell is heavily loaded with high-priority traffic, signalling related to an LWA configuration where both LTE and WLAN access is available, with lower priority traffic, may also be sent over the WLAN access, whereas signalling related to an LWA

configuration where both LTE and WLAN access is available, with higher priority traffic may still be sent over the LTE access. In some embodiments, it may also be advantageous to transmit the same control information (RRC, NAS) over both WLAN and LTE, for purposes of redundancy and making it more likely that the information reach the UE reliably and / or with minimum delay.

[000176] Note that the term user equipment (UE) broadly denotes any device communicating with an access point, base station, or any other radio access node in a wireless network. The term AP (Access Point) may denote a node serving a UE with connectivity utilizing a WLAN access. The term eNB may denote a node serving a UE with connectivity using a 4G/LTE communication system. It should be understood that the term eNB is used generally and that the node serving the UE with connectivity could equally well be an access node for, e.g., 2G/GSM, 3G/WCDMA, or any other existing or future system for wireless communication.

[000177] With this in mind, a radio node herein is any type of node (e.g., a base station or wireless communication device) capable of communicating with another node over radio signals. A radio access node is any type of radio node that provides radio access to a wireless communication device, such as a base station or access point.

[000178] A wireless communication device is any type of radio node capable of communicating with a radio access node over radio signals. A wireless

communication device may therefore refer to a machine-to-machine (M2M) device, a machine-type communications (MTC) device, a NB-loT device, etc. The wireless device may also be a user equipment (UE), however it should be noted that the UE does not necessarily have a "user" in the sense of an individual person owning and/or operating the device. A wireless device may also be referred to as a radio device, a radio communication device, a wireless terminal, or simply a terminal - unless the context indicates otherwise, the use of any of these terms is intended to include device-to-device UEs or devices, machine-type devices or devices capable of machine-to-machine communication, sensors equipped with a wireless device, wireless-enabled table computers, mobile terminals, smart phones, laptop- embedded equipped (LEE), laptop-mounted equipment (LME), USB dongles, wireless customer-premises equipment (CPE), etc. In the discussion herein, the terms machine-to-machine (M2M) device, machine-type communication (MTC) device, wireless sensor, and sensor may also be used. It should be understood that these devices may be UEs, but are generally configured to transmit and/or receive data without direct human interaction.

[000179] In an IOT scenario, a wireless communication device as described herein may be, or may be comprised in, a machine or device that performs monitoring or measurements, and transmits the results of such monitoring measurements to another device or a network. Particular examples of such machines are power meters, industrial machinery, or home or personal

appliances, e.g. refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a wireless communication device as described herein may be comprised in a vehicle and may perform monitoring and/or reporting of the vehicle's operational status or other functions associated with the vehicle.

[000180] In view of the above modifications and variations, Figure 19 illustrates a method 1500 performed by a user equipment 16 in a wireless communication system 10 according to some embodiments. As shown, the method includes establishing wireless local area network (WLAN) radio access 22 (Block 1510). The method 1500 also comprises, when wireless wide area network (WWAN) radio access 18 is unavailable to the user equipment 16 or no control signalling plane is established for the user equipment 16 over WWAN radio access 18, transmitting or receiving a control signalling plane message 28 to or from a WWAN radio access node 24 via the WLAN radio access 22 (Block 1520).

[000181 ] Figure 20 illustrates a corresponding method 1600 performed by a wireless wide area network (WWAN) radio access node 20 of a WWAN 12. The method 1600 includes establishing an interface 26 between the WWAN radio access node 20 and a wireless local area network (WLAN) node 24 of a WLAN 14 (Block 1610). The method 1600 further includes, when WWAN radio access 18 is unavailable to a user equipment 16 or no control signalling plane is established for the user equipment 16 over WWAN radio access 18, transmitting or receiving a control signalling plane message 28 to or from the user equipment 16 via WLAN radio access 22, by transmitting or receiving the control signalling plane message 28 via the established interface 26 (Block 1620).

[000182] Figure 21 correspondingly illustrates a method 1700 performed by a wireless local area network (WLAN) node 24 of a WLAN 14. The method 1700 includes establishing an interface 26 between the WLAN node 24 and a wireless wide area network (WWAN) radio access node 20 of a WWAN 12 (Block 1710). The WLAN node 24 in some embodiments initiates this establishment.

Regardless, the method 1700 further includes, when WWAN radio access 18 is unavailable to a user equipment 16 or no control signalling plane is established for the user equipment 16 over WWAN radio access 18, forwarding a control signalling plane message 28 between the user equipment 16 and the WWAN radio access node 20 via WLAN radio access 22 and the established interface 26 (Block 1720).

[000183] Note that a user equipment 16 as described above may perform the method 1500 and any other processing herein by implementing any functional means or units. In one embodiment, for example, the user equipment 16 comprises respective circuits or circuitry configured to perform the steps shown in Figure 19. The circuits or circuitry in this regard may comprise circuits dedicated to performing certain functional processing and/or one or more microprocessors in conjunction with memory. In embodiments that employ memory, which may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc., the memory stores program code that, when executed by the one or more processors, carries out the techniques described herein. It should also be noted that while several of the embodiments above have been described exemplifying transmission of RRC information, embodiments also apply when a signal radio bearer sends other types of information, e.g., Non-Access Stratum, NAS information, as described in connection to the definitions of the different SRB's above. Consequently, while description about SRBO and SRB1 has been used to exemplify, other types of SRB's may also be considered.

[000184] Figure 22 illustrates the user equipment 16 in the form of a user equipment 16A in accordance with one or more embodiments. As shown, the user equipment 16A includes processing circuitry 1800 and communication circuitry 1810. The communication circuitry 1810 is configured to transmit and/or receive information to and/or from one or more other nodes, e.g., via any communication technology. Such communication may occur via one or more antennas that are either internal or external to the user equipment 16A. The processing circuitry 1800 is configured to perform processing described above, e.g., in Figure 19, such as by executing instructions stored in memory 1820. The processing circuitry 1800 in this regard may implement certain functional means, units, or modules.

[000185] Figure 23 illustrates the user equipment 16 in the form of a user equipment 16B implemented in accordance with one or more other embodiments. As shown, the user equipment 16B implements various functional means, units, or modules, e.g., via the processing circuitry 1800 in Figure 22 and/or via software code. These functional means, units, or modules, e.g., for implementing the method in Figure 19, include for instance an establishing unit or module 1900 for establishing wireless local area network (WLAN) radio access 22. Also included is a transmitting or receiving unit or module 1910 for when wireless wide area network (WWAN) radio access 18 is unavailable to the user equipment 16 or no control signalling plane is established for the user equipment 16 over WWAN radio access 18, transmitting or receiving a control signalling plane message 28 to or from a WWAN radio access node 24 via the WLAN radio access 22.

[000186] Note that also that a WWAN radio access node 20 as described above may perform the method 1600 and any other processing herein by implementing any functional means or units. In one embodiment, for example, the WWAN radio access node 20 comprises respective circuits or circuitry configured to perform the steps shown in Figure 20. The circuits or circuitry in this regard may comprise circuits dedicated to performing certain functional processing and/or one or more microprocessors in conjunction with memory. In embodiments that employ memory, which may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc., the memory stores program code that, when executed by the one or more processors, carries out the techniques described herein.

[000187] Figure 24 illustrates the WWAN radio access node 20 in the form of a WWAN radio access node 20A in accordance with one or more embodiments. As shown, the WWAN radio access node 20A includes processing circuitry 2000 and communication circuitry 2010. The communication circuitry 2010 is configured to transmit and/or receive information to and/or from one or more other nodes, e.g., via any communication technology. Such communication may occur via one or more antennas that are either internal or external to the WWAN radio access node 20A. The processing circuitry 2000 is configured to perform processing described above, e.g., in Figure 20, such as by executing instructions stored in memory 2020. The processing circuitry 2000 in this regard may implement certain functional means, units, or modules.

[000188] Figure 25 illustrates the WWAN radio access node 20 in the form of a WWAN radio access node 20B implemented in accordance with one or more other embodiments. As shown, the WWAN radio access node 20B implements various functional means, units, or modules, e.g., via the processing circuitry 2000 in Figure 24 and/or via software code. These functional means, units, or modules, e.g., for implementing the method in Figure 20, include for instance an establishing unit or module 2100 for establishing an interface 26 between the WWAN radio access node 20 and a wireless local area network (WLAN) node 24 of a WLAN 14. Also included is a transmitting or receiving unit or module 21 10 for when WWAN radio access 18 is unavailable to a user equipment 16 or no control signalling plane is established for the user equipment 16 over WWAN radio access 18, transmitting or receiving a control signalling plane message 28 to or from the user equipment 16 via WLAN radio access 22, by transmitting or receiving the control signalling plane message 28 via the established interface 26.

[000189] Note that also that a WLAN node 24 as described above may perform the method 1700 and any other processing herein by implementing any functional means or units. In one embodiment, for example, the WLAN node 24 comprises respective circuits or circuitry configured to perform the steps shown in Figure 21 . The circuits or circuitry in this regard may comprise circuits dedicated to

performing certain functional processing and/or one or more microprocessors in conjunction with memory. In embodiments that employ memory, which may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc., the memory stores program code that, when executed by the one or more processors, carries out the techniques described herein.

[000190] Figure 26 illustrates the WLAN node 24 in the form of a WLAN radio access node 24A in accordance with one or more embodiments. As shown, the WLAN node 24A includes processing circuitry 2200 and communication circuitry 2210. The communication circuitry 2210 is configured to transmit and/or receive information to and/or from one or more other nodes, e.g., via any communication technology. Such communication may occur via one or more antennas that are either internal or external to the WLAN node 24A. The processing circuitry 2200 is configured to perform processing described above, e.g., in Figure 21 , such as by executing instructions stored in memory 2220. The processing circuitry 2200 in this regard may implement certain functional means, units, or modules.

[000191 ] Figure 27 illustrates the WLAN node 24 in the form of a WLAN node 24B implemented in accordance with one or more other embodiments. As shown, the WLAN node 24B implements various functional means, units, or modules, e.g., via the processing circuitry 2200 in Figure 26 and/or via software code. These functional means, units, or modules, e.g., for implementing the method in Figure 21 , include for instance an establishing unit or module 2300 for establishing an interface 26 between the WLAN node 24 and a wireless wide area network

(WWAN) radio access node 20 of a WWAN 12. Also included is a forwarding unit or module 2310 for when WWAN radio access 18 is unavailable to a user equipment 16 or no control signalling plane is established for the user equipment 16 over WWAN radio access 18, forwarding a control signalling plane message 28 between the user equipment 16 and the WWAN radio access node 20 via WLAN radio access 22 and the established interface 26.

[000192] Those skilled in the art will also appreciate that embodiments herein further include corresponding computer programs.

[000193] A computer program comprises instructions which, when executed on at least one processor of a node, cause the node to carry out any of the respective processing described above. A computer program in this regard may comprise one or more code modules corresponding to the means or units described above.

[000194] Embodiments further include a carrier containing such a computer program. This carrier may comprise one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

[000195] In this regard, embodiments herein also include a computer program product stored on a non-transitory computer readable (storage or recording) medium and comprising instructions that, when executed by a processor of a node, cause the node to perform as described above.

[000196] Embodiments further include a computer program product comprising program code portions for performing the steps of any of the embodiments herein when the computer program product is executed by a computing device. This computer program product may be stored on a computer readable recording medium.

[000197] Below follow various embodiments and examples thereof.

1 . A method performed by a user equipment in a wireless communication system, the method comprising:

establishing wireless local area network (WLAN) radio access; and when wireless wide area network (WWAN) radio access is unavailable to the user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmitting or receiving a control signalling plane message to or from a WWAN radio access node via the WLAN radio access.

2. The method of embodiment 1 , further comprising scanning for availability of WWAN radio access less often when a control signalling plane is established over the WLAN radio access than when no control signalling plane is established over WLAN radio access or WWAN radio access.

3. The method of any of embodiments 1 -2, further comprising delaying user equipment attempts at WWAN radio access until the user equipment receives signalling via the WLAN radio access indicating availability of WWAN radio access.

4. A method performed by a wireless wide area network (WWAN) radio access node of a WWAN, the method comprising:

establishing an interface between the WWAN radio access node and a wireless local area network (WLAN) node of a WLAN; and

when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmitting or receiving a control signalling plane message to or from the user equipment via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface.

5. The method of any of embodiments 1 -4, comprising selecting between the WLAN radio access and the WWAN radio access as the radio access via which an RRC connection request message is to be transmitted by the user equipment to the WWAN radio access node, based on availability of the WLAN radio access and the WWAN radio access. 6. A method performed by a wireless local area network (WLAN) node of a WLAN, the method comprising:

establishing an interface between the WLAN node and a wireless wide area network (WWAN) radio access node of a WWAN; and when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, forwarding a control signalling plane message between the user equipment and the WWAN radio access node via WLAN radio access and the established interface.

7. The method of embodiment 6, further comprising initiating the establishment of the interface.

8. The method of any of embodiments 6-7, further comprising selecting the WWAN radio access node based on at least one of a geographical distance between the WLAN node and the WWAN radio access node, a traffic load of the WWAN radio access node, and a quality or kind of services provided by the WWAN radio access node.

9. The method of embodiment 6, wherein the WWAN radio access node is a default WWAN radio access node to which the WLAN node is configured by default to establish the interface.

10. The method of any of embodiments 6-9, further comprising advertising a capability to forward control signalling plane messages between user equipment and one or more WWAN radio access nodes via WLAN radio access, a WWAN radio access node identity for which the WLAN node is capable of forwarding control signalling plane messages, or both.

1 1 . The method of any of embodiments 1 -10, wherein the control signalling plane message is a radio resource control (RRC) message. 12. The method of any of embodiments 1 -1 1 , wherein the control signalling plane message includes information for requesting, setting up, re-establishing, or reconfiguring an RRC connection between the user equipment and the WWAN radio access node.

13. The method of any of embodiments 1 -12, wherein the control signalling plane message is transmitted or received as part of an RRC connection establishment procedure for establishing an RRC connection between the user equipment and the WWAN radio access node.

14. The method of any of embodiments 1 -13, wherein the control signalling plane message is an RRC connection request message, wherein the user equipment transmits the RRC connection request message to the WWAN radio access node via the WLAN radio access.

15. The method of embodiment 14, wherein the RRC connection request message includes an establishment cause indicating that the RRC connection request message is transmitted or received via the WLAN radio access.

16. The method of any of embodiments 1 -15, wherein the control signalling plane message is an RRC connection setup message, and wherein the user equipment receives the RRC connection setup message from the WWAN radio access node via the WLAN radio access.

17. The method of embodiment 16, wherein the WWAN is a Long Term Evolution (LTE) network, and wherein the RRC connection setup message indicates an LTE-WLAN aggregation (LWA) configuration for setting up a signalling radio bearer over WLAN radio access.

18. The method of any of embodiments 1 -17, wherein the control signalling plane message is an RRC connection reconfiguration message, and wherein, responsive to WWAN radio access becoming unavailable, the user equipment receives the RRC connection reconfiguration message from the WWAN radio access node via the WLAN radio access.

19. The method of any of embodiments 1 -18, wherein the control signalling plane message is a Non-Access Stratum, NAS, message.

20. The method of any of embodiments 1 -19, wherein said transmitting or receiving comprises encapsulating or de-encapsulating the control signalling plane message at a WLAN tunnelling layer implemented directly above or below an RRC layer, a NAS layer, or a packet data convergence protocol (PDCP) layer of a WWAN protocol stack.

21 . The method of embodiment 20, wherein the WWAN is a Long Term Evolution (LTE) network, and the WLAN tunnelling layer is a LTE-WLAN

aggregation (LWA) adaptation protocol layer.

22. The method of any of embodiments 20-21 , wherein the encapsulated control signalling plane message includes header information indicating a radio bearer identity.

23. The method of any of embodiments 20-22, wherein the encapsulated control signalling plane message includes forwarding information indicating whether the control signalling plane message, once de-encapsulated at the WLAN tunnelling layer, is to be forwarded to the RRC layer, the NAS layer, or the PDCP layer of the WWAN protocol stack.

24. The method of embodiment 23, wherein the forwarding information comprises a signalling radio bearer identity or information indicating a type of the control signalling plane message.

25. The method of any of embodiments 1 -24, wherein the user equipment operates in a WLAN RRC connected state when the user equipment has an RRC connection over WLAN radio access and operates in a WWAN RRC connected state when the user equipment has an RRC connection over WWAN radio access, wherein the WLAN RRC connected state and the WWAN RRC connected state are managed with different parameters.

26. A user equipment in a wireless communication system, the user equipment configured to:

establish wireless local area network (WLAN) radio access; and

when wireless wide area network (WWAN) radio access is unavailable to the user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmit or receive a control signalling plane message to or from a WWAN radio access node via the WLAN radio access.

27. The user equipment of embodiment 24, configured to perform the method of any of embodiments 2-3, 5, and 1 1 -25.

28. A wireless wide area network (WWAN) radio access node of a

WWAN, the WWAN radio access node configured to:

establish an interface between the WWAN radio access node and a

wireless local area network (WLAN) node of a WLAN; and when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmit or receive a control signalling plane message to or from the user equipment via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface.

29. The WWAN radio access node of embodiment 28, configured to perform the method of any of embodiments 5 and 1 1 -25. 30. A wireless local area network (WLAN) node of a WLAN, the WLAN node configured to:

establish an interface between the WLAN node and a wireless wide area network (WWAN) radio access node of a WWAN; and when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, forward a control signalling plane message between the user equipment and the WWAN radio access node via WLAN radio access and the established interface.

31 . The WLAN node of embodiment 30, configured to perform the method of any of embodiments 7-25.

32. A computer program comprising instructions which, when executed by at least one processor of a user equipment, causes the user equipment to carry out the method of any of embodiments 1 -3, 5, and 1 1 -25.

33. A carrier containing the computer program of embodiment 32, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

34. A computer program comprising instructions which, when executed by at least one processor of a node, causes the node to carry out the method of any of embodiments 4-25.

35. A carrier containing the computer program of embodiment 34, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

36. A user equipment in a wireless communication system, the user equipment comprising: a processor and a memory, the memory containing instructions executable by the processor whereby the user equipment is configured to:

establish wireless local area network (WLAN) radio access; and when wireless wide area network (WWAN) radio access is

unavailable to the user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmit or receive a control signalling plane message to or from a WWAN radio access node via the WLAN radio access.

37. The user equipment of embodiment 36, wherein the memory contains instructions executable by the processor whereby the user equipment is configured to perform the method of any of embodiments 2-3, 5, and 1 1 -25.

38. A wireless wide area network (WWAN) radio access node of a WWAN, the WWAN radio access node comprising:

a processor and a memory, the memory containing instructions executable by the processor whereby the WWAN radio access node is configured to:

establish an interface between the WWAN radio access node and a wireless local area network (WLAN) node of a WLAN; and when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmit or receive a control signalling plane message to or from the user equipment via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface.

39. The WWAN radio access node of embodiment 38, wherein the memory contains instructions executable by the processor whereby the WWAN radio access node is configured to perform the method of any of embodiments 5 and 1 1 -25. 40. A wireless local area network (WLAN) node of a WLAN, the WLAN node comprising:

a processor and a memory, the memory containing instructions executable by the processor whereby the WLAN node is configured to:

establish an interface between the WLAN node and a wireless wide area network (WWAN) radio access node of a WWAN; and when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, forward a control signalling plane message between the user equipment and the WWAN radio access node via WLAN radio access and the established interface.

41 . The WLAN node of embodiment 40, wherein the memory contains instructions executable by the processor whereby the WLAN node is configured to perform the method of any of embodiments 7-25.

42. A user equipment in a wireless communication system, the user equipment comprising:

an establishing module for establishing wireless local area network (WLAN) radio access; and

a transmitting or receiving module for, when wireless wide area network (WWAN) radio access is unavailable to the user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmitting or receiving a control signalling plane message to or from a WWAN radio access node via the WLAN radio access.

43. The user equipment of embodiment 41 , configured to perform the method of any of embodiments 2-3, 5, and 1 1 -25. 44. A wireless wide area network (WWAN) radio access node of a

WWAN, the WWAN radio access node comprising:

an establishing module for establishing an interface between the WWAN radio access node and a wireless local area network (WLAN) node of a WLAN; and

a transmitting or receiving module for, when WWAN radio access is

unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, transmitting or receiving a control signalling plane message to or from the user equipment via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface.

45. The WWAN radio access node of embodiment 44, configured to perform the method of any of embodiments 5 and 1 1 -25.

46. A wireless local area network (WLAN) node of a WLAN, the WLAN node configured to:

an establishing module for establishing an interface between the WLAN node and a wireless wide area network (WWAN) radio access node of a WWAN; and

a forwarding module for, when WWAN radio access is unavailable to a user equipment or no control signalling plane is established for the user equipment over WWAN radio access, forwarding a control signalling plane message between the user equipment and the WWAN radio access node via WLAN radio access and the established interface.

45. The WLAN node of embodiment 44, configured to perform the method of any of embodiments 7-25.

[000198] Embodiments herein also relate to a method performed by a wireless device operable in a Wireless Wide Area Network, WWAN, and a Wireless Local Area Network, WLAN, employing different Radio Access Technologies, RATs. The method comprises establishing 3020 a WLAN radio access with a WLAN node. When WWAN radio access is unavailable to the wireless device, the method comprises transmitting 3040 and/or receiving a control signalling plane message to and/or from a WWAN radio access node via the WLAN node.

[000199] The wireless device, is operable in at least two different types of communication network, a WWAN and a WLAN, the communication networks employing different RATs. Generally, when the wireless device is connected to WWAN, control signalling associated with the WWAN is transmitted on a channel of the WWAN. However, it might be that the wireless device is in a geographical position in which WWAN coverage is poor or even non-existing. At the

geographical position of the wireless device there may be a WLAN to which the wireless device may establish a connection in order to get connected to the WLAN by means of a WLAN node. The wireless device may thus establish a WLAN radio access with that WLAN node. The WWAN and the WLAN may be "connected" to each other, e.g. such that the WLAN node and a WWAN radio access node are connected by means of an interface e.g. an Xw user and control plane. The wireless device may then transmit 3040 and/or receive a control signalling plane message to and/or from a WWAN radio access node via the WLAN node.

[000200] The wireless device may or may not previously have a connection to the WWAN, in case the wireless device does not have a connection to WWAN, the wireless device may first establish the WLAN radio access with the WLAN node. The wireless device may thus establish a connection to the WWAN by means of the WLAN node as will be described in more detail below.

[000201 ] The method performed by the wireless device has several advantages. One possible advantage is that communication towards the WWAN, e.g. a 3GPP network, may continue by means of LWA, even in situations when WWAN, e.g. LTE, coverage is lost. The RRC anchoring and the UE context may be kept in the WWAN network node, e.g. an eNB, so this is also transparent to the EPC and to the rest of the RAN. An additional advantage is that the wireless device may provide radio measurements even outside the coverage of the WWAN; this may be particularly beneficial in conjunction with SON functionality in order to provide additional infornnation about problematic areas. Another possible advantage is that the significant impact is limited to RRC routing inside the WWAN network node and the wireless device; it is possible to support functionality without any change to the LWA architecture according to 3GPP release 13.

[000202] A connection establishment with the WWAN node may be initiated through communication via the WLAN node.

[000203] When the wireless device has established the WLAN radio access with the WLAN node, the wireless device may request the WLAN node to establish a connection with the WWAN node. The wireless device may e.g. transmit a type of connection request message to the WLAN node in order for the WLAN node to initiate the establishment of the connection to the WWAN node as will be described in more detail below.

[000204] The control signalling plane message may be a RRC message.

[000205] The control signalling plane message may include information for requesting, setting up, re-establishing, or reconfiguring an RRC connection between the wireless device and the WWAN radio access node.

[000206] It may be that the wireless device previously has a connection to the WWAN radio access node, wherein the wireless device may need to re-establish or reconfigure the RRC connection, e.g. due to a change in signal quality and/or signal strength. It may also be that the wireless device does not have a previous connection to the WWAN radio access node, wherein the wireless device may set up the RRC connection to the WWAN radio access node.

[000207] The control signalling plane message may be transmitted or received as part of an RRC connection establishment procedure for establishing an RRC connection between the wireless device and the WWAN radio access node.

[000208] As described above, the wireless device may not previously have a connection to the WWAN radio access node, but only has established the WLAN radio access to the WLAN node. Then, when the wireless device wishes to establish the RRC connection to the WWAN radio access node via the WLAN node, the control signalling plane message between the WWAN radio access node and the wireless device transmitted via the WLAN node may then be part of the RRC connection establishment procedure for establishing the RRC connection between the wireless device and the WWAN radio access node

[000209] The RRC connection request message may include an establishment cause indicating that the RRC connection request message is transmitted or received via the WLAN radio access.

[000210] There may be a cause for the wireless device initiating the RRC connection to the WWAN radio access node via the WLAN node. The cause may for e.g. be cause or other information indicating that the connection request message is transmitted via the WLAN radio access and not directly between the WWAN radio access node and the wireless device.

[00021 1 ] The control signalling plane message may be an RRC connection setup message sent from the WWAN node to the wireless device, and wherein the wireless device receives the RRC connection setup message from the WWAN radio access node via the WLAN radio access.

[000212] The WWAN may be a LTE network, and wherein the RRC connection setup message indicates an LTE-WLAN aggregation, LWA, configuration for setting up a signalling radio bearer over WLAN radio access.

[000213] The transmitting and/or receiving may comprise encapsulating or de- encapsulating the control signalling plane message at a WLAN tunnelling layer implemented directly above or below an RRC layer, a NAS layer, or a Packet Data Convergence Protocol, PDCP, layer of a WWAN protocol stack.

[000214] By encapsulating or de-encapsulating the control signalling plane message at a WLAN tunnelling layer, the wireless device and the WWAN radio access node may communicate control signalling between themselves via the WLAN node. The WLAN node thus provide communication between the wireless device and the WWAN radio access node by means of the encapsulating or de- encapsulating the control signalling plane message at a WLAN tunnelling layer. The WLAN tunnelling layer may be implemented at different layers of the WWAN protocol stack. In one example, the WLAN tunnelling layer is implemented directly above or below the RRC layer, the NAS layer, or the PDCP layer of the WWAN protocol stack.

[000215] The WWAN may be a LTE network, and the WLAN tunnelling layer may be a LWA adaptation protocol layer.

[000216] One function of LWAAP is to provide transfer of user plane data (LWA AP SDU's) and to be able to identify LWA bearers and to which particular LWA AP SDUs belong. At the eNB and for downlink communication, the LWA AP entity receives LWAAP SDUs from upper layers and constructs a corresponding LWA AP PDU and delivers it to lower Layers. Correspondingly for the wireless device (e.g. UE), the LWA AP entity will receive LWAAP PDU's from lower layers and reassemble corresponding LWAAP SDU's and deliver it to higher layers. A corresponding procedure would be executed for uplink communication, but the roles of the WWAN radio access node (e.g. eNB) and the wireless device (e.g. UE) would be reversed. As can be recognised, the LWAAP essentially adds an identifier to the incoming LWAAP SDUs. The identifiers are, for downlink

communication, added in the LWAAP entity on the WWAN radio access node (e.g. eNB) side and removed in the LWAAP entity on the wireless device (e.g. UE) side. The LWA AP is further described in 3GPP TS 36.360

[000217] The encapsulated control signalling plane message may include header information indicating a radio bearer identity.

[000218] Embodiments herein also relate to a method performed by a WWAN radio access node operable in a WWAN. The method comprises establishing an interface between the WWAN radio access node and a wireless local area network, WLAN, node of a WLAN. When WWAN radio access is unavailable to a wireless device, the method comprises transmitting and/or receiving a control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the

established interface.

[000219] As described above for the wireless device, the WWAN radio access node may, or may not, have a previous connection with the wireless device. The WWAN radio access node establishes the interface between the WWAN radio access node and a wireless local area network, WLAN, node of a WLAN. In this manner, the WLAN and the WWAN radio access node may communicate by means of the established interface. Using this established interface, the WWAN radio access node may transmit and/or receive the control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface, when WWAN radio access is unavailable to a wireless device.

[000220] The method performed by the WWAN radio access node has several advantages. One possible advantage is that communication towards the WWAN, e.g. a 3GPP network, may continue by means of LWA, even in situations when WWAN, e.g. LTE, coverage is lost. The RRC anchoring and the UE context may be kept in the WWAN network node, e.g. an eNB, so this is also transparent to the EPC and to the rest of the RAN. An additional advantage is that the wireless device may provide radio measurements even outside the coverage of the

WWAN; this may be particularly beneficial in conjunction with SON functionality in order to provide additional information about problematic areas. Another possible advantage is that the significant impact is limited to RRC routing inside the WWAN network node and the wireless device; it is possible to support functionality without any change to the LWA architecture according to 3GPP release 13.

[000221 ] The method may further comprise receiving a request for the establishing of the interface between the WWAN radio access node and the WLAN node of the WLAN.

[000222] As described above, the wireless device may request the WLAN node to establish the interface, or connection, to the WWAN radio access node. Once the WLAN node receives such a request, the WLAN node may transmit a request to the WWAN radio access node for the establishing of the interface between the WWAN radio access node and the WLAN node of the WLAN. Once the WWAN radio access node receives the request, the WWAN radio access node may establish the interface, or connection, between the WWAN radio access node and the WLAN node of the WLAN.

[000223] The method may still further comprise selecting between the WLAN radio access and the WWAN radio access as the radio access via which an RRC connection request message is to be transmitted by the wireless device to the WWAN radio access node, based on availability of the WLAN radio access and the WWAN radio access.

[000224] The transmitting and/or receiving may comprise encapsulating or de- encapsulating the control signalling plane message at a WLAN tunnelling layer implemented directly above or below an RRC layer, a NAS layer, or a PDCP layer of a WWAN protocol stack.

[000225] Embodiments herein also relate to a method performed by a WLAN node operable in a WLAN. The method comprises establishing an interface between the WLAN node and a WWAN radio access node of a WWAN. When WWAN radio access is unavailable to a wireless device, the method comprises forwarding a control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access and the established interface.

[000226] When the wireless device wishes to establish a connection with the WWAN radio access node via the WLAN node, the wireless device transmits a request to the WLAN node. The WLAN node thus establishes the interface, e.g. Xw interface, between the WLAN node and the WWAN radio access node of a WWAN. Using this established interface, the WLAN may forward control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access when WWAN radio access is unavailable to the wireless device. In this manner, the wireless device and the WWAN radio access node may exchange control signalling via the WLAN node and the wireless device does not need to have a direct connection to the WWAN radio access node e.g. when WWAN radio coverage is poor or unavailable.

[000227] The method performed by the WLAN node has several advantages. One possible advantage is that communication towards the WWAN, e.g. a 3GPP network, may continue by means of LWA, even in situations when WWAN, e.g. LTE, coverage is lost. The RRC anchoring and the UE context may be kept in the WWAN network node, e.g. an eNB, so this is also transparent to the EPC and to the rest of the RAN. An additional advantage is that the wireless device may provide radio measurements even outside the coverage of the WWAN; this may be particularly beneficial in conjunction with SON functionality in order to provide additional information about problematic areas. Another possible advantage is that the significant impact is limited to RRC routing inside the WWAN network node and the wireless device; it is possible to support functionality without any change to the LWA architecture according to 3GPP release 13.

[000228] The method may further comprise initiating the establishment of the interface.

[000229] As described above, the wireless device may transmit a request to the WLAN node for establishing the interface between the WLAN node and the WWAN radio access node. Thus, once the WLAN node receives such a request from the wireless device, the WLAN node may initiate the establishment of the interface, which may be an Xw interface for example.

[000230] The initiating 5010 of the establishment of the interface may comprise transmitting, to the WWAN, a request for the establishing 5020 of the interface between the WWAN radio access node and a WLAN node of a WLAN.

[000231 ] The method may further comprise selecting 5015 the WWAN radio access node based on at least one of a geographical distance between the WLAN node and the WWAN radio access node, a traffic load of the WWAN radio access node, and a quality or kind of services provided by the WWAN radio access node. [000232] There may be different ways for the WLAN node to select which WWAN radio access node to select. In one example, the WLAN node makes its selection based on at least one of a geographical distance between the WLAN node and the WWAN radio access node, a traffic load of the WWAN radio access node, and a quality or kind of services provided by the WWAN radio access node. In this manner, the WLAN node may select a node that is relatively close to the WLAN, and/or has a reasonable (i.e. not too high) traffic load, and/or acceptable signal quality, and/or is able to provide services provided by the WWAN radio access node.

[000233] The WWAN radio access node may be a default WWAN radio access node to which the WLAN node is configured by default to establish the interface.

[000234] In another example, the WLAN may select the default WWAN radio access node. This means that there is one WWAN radio access node that is the default WWAN radio access node for the WLAN node, wherein the WLAN node always selects the default WWAN radio access node.

[000235] The method may further comprise advertising 5005 a capability to forward control signalling plane messages between wireless device and one or more WWAN radio access nodes via WLAN radio access, a WWAN radio access node identity for which the WLAN node is capable of forwarding control signalling plane messages, or both.

[000236] Embodiments herein also relate to a wireless device 3300, 3400 operable in a WWAN and in a WLAN employing different RATs. The wireless device has the same technical features, objects and advantages as the method performed by the wireless device described above. The wireless device will thus only be described in brief in order to avoid unnecessary repetition. The wireless device is configured for establishing a WLAN radio access with a WLAN node, and when WWAN radio access is unavailable to the wireless device, transmitting and/or receiving a control signalling plane message to and/or from a WWAN radio access node via the WLAN node. [000237] The wireless device may be realised or implemented in various different ways. An exemplifying implementation is illustrated in figure 33. Figure 33

illustrates the wireless device 3300 comprising a processor 6021 and memory

3322, the memory comprising instructions, e.g. by means of a computer program

3323, which when executed by the processor 3321 causes the wireless device 3300 to establish a WLAN radio access with a WLAN node; and when WWAN radio access is unavailable to the wireless device, to transmit and/or receiving a control signalling plane message to and/or from a WWAN radio access node via the WLAN node.

[000238] Figure 33 also illustrates the wireless device 3300 comprising a memory 3310. It shall be pointed out that figure 33 is merely an exemplifying illustration and memory 3310 may optionally, be a part of the memory 3322 or be a further memory of the wireless device 3300 operable in the communication system. The memory may for example comprise information relating to the wireless device 3300, to statistics of operation of the wireless device 3300, just to give a couple of illustrating examples. Figure 33 further illustrates the wireless device 3300 comprising processing means 3320, which comprises the memory 3322 and the processor 3321 . Still further, figure 33 illustrates the wireless device 3300 comprising a communication unit 3330. The communication unit 6030 may comprise an interface through which the wireless device 3300 communicates with other nodes, access points, wireless devices or entities of any of the

communication networks (WWAN and WLAN). Figure 33 also illustrates the wireless device 3300 comprising further functionality 3340. The further

functionality 6040 may comprise hardware of software necessary for the wireless device 3300 to perform different tasks that are not disclosed herein.

[000239] An alternative exemplifying implementation of the wireless device 3300, 3400 is illustrated in figure 34. Figure 34 illustrates the wireless device 3400 comprising an establishing unit 3403 for establishing a WLAN radio access with a WLAN node. Figure 34 also illustrates the wireless device 3400 comprising a transceiver unit 3404 for transmitting and/or receiving a control signalling plane message to and/or from a WWAN radio access node via the WLAN node, when WWAN radio access is unavailable to the wireless device.

[000240] In figure 34, the wireless device 3400 operable in a WWAN and in a WLAN employing different RATs is also illustrated comprising a communication unit 3401 . Through this unit, the wireless device 3400 is adapted to communicate with other nodes and/or entities in the wireless communication networks or systems. The communication unit 3401 may comprise more than one receiving arrangement. For example, the communication unit may be connected to both a wire and an antenna, by means of which the wireless device 3400 is enabled to communicate with other nodes and/or entities in the communication networks. Similarly, the communication unit 3401 may comprise more than one transmitting arrangement, which in turn are connected to both a wire and an antenna, by means of which the wireless device 3400 is enabled to communicate with other nodes and/or entities in the wireless communication networks. The wireless device 3400 further comprises a memory 3402 for storing data. Further, the wireless device 3400 may comprise a control or processing unit (not shown) which in turn is connected to the different units 3403-3404. It shall be pointed out that this is merely an illustrative example and the wireless device 3400 may comprise more, less or other units or modules which execute the functions of the wireless device 3400 in the same manner as the units illustrated in figure 34.

[000241 ] It should be noted that figure 34 merely illustrates various functional units in the wireless device 3400 in a logical sense. The functions in practice may be implemented using any suitable software and hardware means/circuits etc. Thus, the embodiments are generally not limited to the shown structures of the wireless device 3400 and the functional units. Hence, the previously described exemplary embodiments may be realised in many ways. For example, one embodiment includes a computer-readable medium having instructions stored thereon that are executable by the control or processing unit for executing the method steps in the wireless device 3400. The instructions executable by the computing system and stored on the computer-readable medium perform the method steps of the wireless device 3400 as set forth in the claims. [000242] The wireless device has the same advantages as the method performed by the wireless device. One possible advantage is that communication towards the WWAN, e.g. a 3GPP network, may continue by means of LWA, even in situations when WWAN, e.g. LTE, coverage is lost. The RRC anchoring and the UE context may be kept in the WWAN network node, e.g. an eNB, so this is also transparent to the EPC and to the rest of the RAN. An additional advantage is that the wireless device may provide radio measurements even outside the coverage of the

WWAN; this may be particularly beneficial in conjunction with SON functionality in order to provide additional information about problematic areas. Another possible advantage is that the significant impact is limited to RRC routing inside the WWAN network node and the wireless device; it is possible to support functionality without any change to the LWA architecture according to 3GPP release 13.

[000243] A connection establishment with the WWAN node may be initiated through communication via the WLAN node.

[000244] The control signalling plane message may be a RRC message.

[000245] The control signalling plane message may include information for requesting, setting up, re-establishing, or reconfiguring an RRC connection between the wireless device and the WWAN radio access node.

[000246] The control signalling plane message may be transmitted or received as part of an RRC connection establishment procedure for establishing an RRC connection between the wireless device and the WWAN radio access node.

[000247] The RRC connection request message may include an establishment cause indicating that the RRC connection request message is transmitted or received via the WLAN radio access.

[000248] The control signalling plane message may be an RRC connection setup message sent from the WWAN node to the wireless device, and wherein the wireless device is configured for receiving the RRC connection setup message from the WWAN radio access node via the WLAN radio access. [000249] The WWAN may be a LTE network, and wherein the RRC connection setup message indicates an LWA configuration for setting up a signalling radio bearer over WLAN radio access.

[000250] The transmitting and/or receiving may comprise encapsulating or de- encapsulating the control signalling plane message at a WLAN tunnelling layer implemented directly above or below an RRC layer, a NAS layer, or a PDCP layer of a WWAN protocol stack.

[000251 ] The WWAN may be a LTE network, and the WLAN tunnelling layer may be a LWA adaptation protocol layer.

[000252] The encapsulated control signalling plane message may include header information indicating a radio bearer identity.

[000253] Embodiments herein also relate to a WWAN radio access node 3500, 3600 operable in a WWAN. The WWAN radio access node has the same technical features, objects and advantages as the method performed by the WWAN radio access node described above. The WWAN radio access node will thus only be described in brief in order to avoid unnecessary repetition. The WWAN radio access node is configured for establishing an interface between the WWAN radio access node and a WLAN node of a WLAN; and when WWAN radio access is unavailable to a wireless device, for transmitting and/or receiving a control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the

established interface.

[000254] The WWAN radio access node may be implemented or realised in various different ways. An exemplifying implementation is illustrated in figure 35. Figure 35 illustrates the WWAN radio access node 3500 comprising a processor 3521 and memory 3522, the memory comprising instructions, e.g. by means of a computer program 3523, which when executed by the processor 3521 causes the WWAN radio access node 3500 to establish an interface between the WWAN radio access node and a WLAN node of a WLAN; and when WWAN radio access is unavailable to the wireless device, to transmit and/or receive a control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface.

[000255] Figure 35 also illustrates the WWAN radio access node 3500 comprising a memory 3510. It shall be pointed out that figure 35 is merely an exemplifying illustration and memory 3510 may optionally, be a part of the memory 3522 or be a further memory of the WWAN radio access node 3500 operable in the

communication system. The memory may for example comprise information relating to the WWAN radio access node 3500, to statistics of operation of the WWAN radio access node 3500, just to give a couple of illustrating examples. Figure 35 further illustrates the WWAN radio access node 3500 comprising processing means 8020, which comprises the memory 3522 and the processor 3521 . Still further, figure 35 illustrates the WWAN radio access node 3500 comprising a communication unit 3530. The communication unit 3530 may comprise an interface through which the WWAN radio access node 3500 communicates with other nodes, access points, wireless devices or entities of any of the communication networks (WWAN and WLAN). Figure 35 also illustrates the WWAN radio access node 3500 comprising further functionality 3540. The further functionality 3540 may comprise hardware of software necessary for the WWAN radio access node 3500 to perform different tasks that are not disclosed herein.

[000256] An alternative exemplifying implementation of the WWAN radio access node 3500, 3600 is illustrated in figure 36. Figure 36 illustrates the WWAN radio access node 3600 comprising an establishing unit 3603 for establishing an interface between the WWAN radio access node and a WLAN node of a WLAN. Figure 36 also illustrates the WWAN radio access node 3600 comprising a transceiver unit 3604 for transmitting and/or receiving a control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface, when WWAN radio access is unavailable to the wireless device. [000257] In figure 36, the WWAN radio access node 3600 is also illustrated comprising a communication unit 3601 . Through this unit, the WWAN radio access node 3600 is adapted to communicate with other nodes and/or entities in the wireless communication networks or systems. The communication unit 3601 may comprise more than one receiving arrangement. For example, the communication unit may be connected to both a wire and an antenna, by means of which the WWAN radio access node 3600 is enabled to communicate with other nodes and/or entities in the communication networks. Similarly, the communication unit 3601 may comprise more than one transmitting arrangement, which in turn are connected to both a wire and an antenna, by means of which the WWAN radio access node 3600 is enabled to communicate with other nodes and/or entities in the wireless communication networks. The WWAN radio access node 3600 further comprises a memory 3602 for storing data. Further, the WWAN radio access node 3600 may comprise a control or processing unit (not shown) which in turn is connected to the different units 3603-3604. It shall be pointed out that this is merely an illustrative example and the WWAN radio access node 3600 may comprise more, less or other units or modules which execute the functions of the WWAN radio access node 3600 in the same manner as the units illustrated in figure 36.

[000258] It should be noted that figure 36 merely illustrates various functional units in the WWAN radio access node 3600 in a logical sense. The functions in practice may be implemented using any suitable software and hardware

means/circuits etc. Thus, the embodiments are generally not limited to the shown structures of the WWAN radio access node 3600 and the functional units. Hence, the previously described exemplary embodiments may be realised in many ways. For example, one embodiment includes a computer-readable medium having instructions stored thereon that are executable by the control or processing unit for executing the method steps in the WWAN radio access node 3600. The

instructions executable by the computing system and stored on the computer- readable medium perform the method steps of the WWAN radio access node 3600 as set forth in the claims. [000259] The WWAN radio access node has the same advantages as the method performed by the WWAN radio access node. One possible advantage is that communication towards the WWAN, e.g. a 3GPP network, may continue by means of LWA, even in situations when WWAN, e.g. LTE, coverage is lost. The RRC anchoring and the UE context may be kept in the WWAN network node, e.g. an eNB, so this is also transparent to the EPC and to the rest of the RAN. An additional advantage is that the wireless device may provide radio measurements even outside the coverage of the WWAN; this may be particularly beneficial in conjunction with SON functionality in order to provide additional information about problematic areas. Another possible advantage is that the significant impact is limited to RRC routing inside the WWAN network node and the wireless device; it is possible to support functionality without any change to the LWA architecture according to 3GPP release 13.

[000260] The WWAN radio access node may further be configured for receiving a request for the establishing of the interface between the WWAN radio access node and the WLAN node of the WLAN.

[000261 ] The WWAN radio access node may still further be configured for selecting between the WLAN radio access and the WWAN radio access as the radio access via which an RRC connection request message is to be transmitted by the wireless device to the WWAN radio access node, based on availability of the WLAN radio access and the WWAN radio access.

[000262] The transmitting and/or receiving may comprise encapsulating or de- encapsulating the control signalling plane message at a WLAN tunnelling layer implemented directly above or below an RRC layer, a NAS layer, or a Packet Data Convergence Protocol, PDCP, layer of a WWAN protocol stack.

[000263] Embodiments herein also relate to a WLAN node operable in a WWAN. The WLAN node has the same technical features, objects and advantages as the method performed by the WLAN node described above. The WLAN node will thus only be described in brief in order to avoid unnecessary repetition. The WLAN node is configured for establishing an interface between the WLAN node and a WWAN radio access node of a WWAN; and when WWAN radio access is unavailable to a wireless device, for forwarding a control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access and the established interface.

[000264] The WLAN node may be realised or implemented in various different ways. An exemplifying implementation is illustrated in figure 37. Figure 37

illustrates the WLAN node 10000 comprising a processor 10021 and memory

10022, the memory comprising instructions, e.g. by means of a computer program

10023, which when executed by the processor 10021 causes the WLAN node 10000 to establish an interface between the WLAN node and a WWAN radio access node of a WWAN; and when WWAN radio access is unavailable to the wireless device, to forward a control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access and the established interface.

[000265] Figure 37 also illustrates the WLAN node 3700 comprising a memory 3710. It shall be pointed out that figure 37 is merely an exemplifying illustration and memory 3710 may optionally, be a part of the memory 3722 or be a further memory of the WLAN node 3700 operable in the communication system. The memory may for example comprise information relating to the WLAN node 3700, to statistics of operation of WLAN node 3700, just to give a couple of illustrating examples. Figure 35 further illustrates the WLAN node 3700 comprising

processing means 3720, which comprises the memory 3722 and the processor 3721 . Still further, figure 37 illustrates the WLAN node 3700 comprising a communication unit 3730. The communication unit 3730 may comprise an interface through which the WLAN node 3700 communicates with other nodes, access points, wireless devices or entities of any of the communication networks (WWAN and WLAN). Figure 37 also illustrates the WLAN node 3700 comprising further functionality 3740. The further functionality 3740 may comprise hardware of software necessary for the WLAN node 3700 to perform different tasks that are not disclosed herein. [000266] An alternative exemplifying implementation of the WLAN node 3700, 3800 is illustrated in figure 38. Figure 38 illustrates the WLAN node 3800 comprising an establishing unit 3803 for establishing an interface between the WLAN node and a WWAN radio access node of a WWAN. Figure 38 also illustrates the WLAN node 3800 comprising a forwarding unit 3804 for forwarding a control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access and the established interface when WWAN radio access is unavailable to a wireless device.

[000267] In figure 38, the WLAN node 3800 is also illustrated comprising a communication unit 3801 . Through this unit, the WLAN node 3800 is adapted to communicate with other nodes and/or entities in the wireless communication networks or systems. The communication unit 3801 may comprise more than one receiving arrangement. For example, the communication unit may be connected to both a wire and an antenna, by means of which the WLAN node 3800 is enabled to communicate with other nodes and/or entities in the communication networks. Similarly, the communication unit 3801 may comprise more than one transmitting arrangement, which in turn are connected to both a wire and an antenna, by means of which the WLAN node 3800 is enabled to communicate with other nodes and/or entities in the wireless communication networks. The WLAN node 3800 further comprises a memory 3802 for storing data. Further, the WLAN node 3800 may comprise a control or processing unit (not shown) which in turn is connected to the different units 3803-3804. It shall be pointed out that this is merely an illustrative example and the WLAN node 3800 may comprise more, less or other units or modules which execute the functions of the WLAN node 3800 in the same manner as the units illustrated in figure 38.

[000268] It should be noted that figure 38 merely illustrates various functional units in the WLAN node 3800 in a logical sense. The functions in practice may be implemented using any suitable software and hardware means/circuits etc. Thus, the embodiments are generally not limited to the shown structures of the WLAN node 3800 and the functional units. Hence, the previously described exemplary embodiments may be realised in many ways. For example, one embodiment includes a computer-readable medium having instructions stored thereon that are executable by the control or processing unit for executing the method steps in the WLAN node 3800. The instructions executable by the computing system and stored on the computer-readable medium perform the method steps of the WLAN node 3800 as set forth in the claims.

[000269] The WLAN node has the same advantages as the method performed by the WLAN node. One possible advantage is that communication towards the WWAN, e.g. a 3GPP network, may continue by means of LWA, even in situations when WWAN, e.g. LTE, coverage is lost. The RRC anchoring and the UE context may be kept in the WWAN network node, e.g. an eNB, so this is also transparent to the EPC and to the rest of the RAN. An additional advantage is that the wireless device may provide radio measurements even outside the coverage of the

WWAN; this may be particularly beneficial in conjunction with SON functionality in order to provide additional information about problematic areas. Another possible advantage is that the significant impact is limited to RRC routing inside the WWAN network node and the wireless device; it is possible to support functionality without any change to the LWA architecture according to 3GPP release 13.

[000270] The WLAN node may further be configured for initiating the

establishment of the interface.

[000271 ] The initiating of the establishment of the interface may comprise transmitting, to the WWAN, a request for the establishing 5020 of the interface between the WWAN radio access node and a WLAN node of a WLAN.

[000272] The WLAN node may further be configured for selecting the WWAN radio access node based on at least one of a geographical distance between the WLAN node and the WWAN radio access node, a traffic load of the WWAN radio access node, and a quality or kind of services provided by the WWAN radio access node.

[000273] The WWAN radio access node may be a default WWAN radio access node to which the WLAN node is configured by default to establish the interface. [000274] The WLAN node may further be configured for advertising a capability to forward control signalling plane messages between wireless device and one or more WWAN radio access nodes via WLAN radio access, a WWAN radio access node identity for which the WLAN node is capable of forwarding control signalling plane messages, or both.

[000275] Figure 39 schematically shows an embodiment of an arrangement 3900 in a wireless device 3400 operable in a WWAN and in a WLAN employing different RATs. Comprised in the arrangement 3900 in the wireless device 3400 are here a processing unit 3906, e.g. with a Digital Signal Processor, DSP. The processing unit 3906 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 3900 of the wireless device 3400 may also comprise an input unit 3902 for receiving signals from other entities, and an output unit 3904 for providing signal(s) to other entities. The input unit and the output unit may be arranged as an integrated entity or as illustrated in the example of figure 34, as one or more interfaces 3401 .

[000276] Furthermore, the arrangement 3900 in the wireless device 3400 comprises at least one computer program product 3908 in the form of a nonvolatile memory, e.g. an Electrically Erasable Programmable Read-Only Memory, EEPROM, a flash memory and a hard drive. The computer program product 3908 comprises a computer program 3900, which comprises code means, which when executed in the processing unit 3906 in the arrangement 3900 in the wireless device 3400 causes the wireless device 3400 to perform the actions e.g. of the procedure described earlier in conjunction with figure 30.

[000277] The computer program 3900 may be configured as a computer program code structured in computer program modules 3900a-3900e. Hence, in an exemplifying embodiment, the code means in the computer program of the arrangement 3900 in the wireless device 3400 comprises an establishing unit, or module, for establishing a WLAN radio access with a WLAN node; and a transceiver unit, or module, for transmitting and/or receiving a control signalling plane message to and/or from a WWAN radio access node via the WLAN node when WWAN radio access is unavailable to the wireless device. [000278] The computer program modules could essentially perform the actions of the flow illustrated in figure 30, to emulate the wireless device 3400. In other words, when the different computer program modules are executed in the processing unit 3906, they may correspond to the units 3403-3404 of figure 34.

[000279] Figure 40 schematically shows an embodiment of an arrangement 4000 in a WWAN radio access node 3600 operable in a WWAN. Comprised in the arrangement 4000 in the WWAN radio access node 3600 are here a processing unit 4006, e.g. with a Digital Signal Processor. The processing unit 4006 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 4000 in the WWAN radio access node 3600 may also comprise an input unit 4002 for receiving signals from other entities, and an output unit 4004 for providing signal(s) to other entities. The input unit and the output unit may be arranged as an integrated entity or as illustrated in the example of figure 36, as one or more interfaces 3601 .

[000280] Furthermore, the arrangement 4000 in the WWAN radio access node 3600 comprises at least one computer program product 4008 in the form of a nonvolatile memory, e.g. an Electrically Erasable Programmable Read-Only Memory, EEPROM, a flash memory and a hard drive. The computer program product 4008 comprises a computer program 3910, which comprises code means, which when executed in the processing unit 4006 in the arrangement 4000 in the WWAN radio access node 3600 causes the WWAN radio access node 3600 to perform the actions e.g. of the procedure described earlier in conjunction with figures 31a- 31c.

[000281 ] The computer program 4010 may be configured as a computer program code structured in computer program modules 4010a-4010e. Hence, in an exemplifying embodiment, the code means in the computer program of the arrangement 4000 in the WWAN radio access node 3600 comprises an

establishing unit, or module, for establishing an interface between the WWAN radio access node and a wireless local area network, WLAN, node of a WLAN. The computer program further comprises a transceiver unit, or module, for transmitting and/or receiving a control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface when WWAN radio access is unavailable to a wireless device.

[000282] The computer program modules could essentially perform the actions of the flow illustrated in figures 31a-31c, to emulate the WWAN radio access node 3600. In other words, when the different computer program modules are executed in the processing unit 4006, they may correspond to the units 3603-3604 of figure 36.

[000283] Figure 41 schematically shows an embodiment of an arrangement 4100 in a WLAN node 3800 operable in a WLAN. Comprised in the arrangement 4100 in the WLAN node 3800 are here a processing unit 4106, e.g. with a Digital Signal Processor. The processing unit 4106 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 4100 in the WLAN node 3800 may also comprise an input unit 4102 for receiving signals from other entities, and an output unit 4104 for providing signal(s) to other entities. The input unit and the output unit may be arranged as an integrated entity or as illustrated in the example of figure 38, as one or more interfaces 3801 .

[000284] Furthermore, the arrangement 4100 in the WLAN node 3800 comprises at least one computer program product 4108 in the form of a nonvolatile memory, e.g. an Electrically Erasable Programmable Read-Only Memory, EEPROM, a flash memory and a hard drive. The computer program product 4108 comprises a computer program 41 10, which comprises code means, which when executed in the processing unit 4106 in the arrangement 4100 in the WLAN node 3800 causes the WLAN node 3800 to perform the actions e.g. of the procedure described earlier in conjunction with figures 32a-32d.

[000285] The computer program 41 10 may be configured as a computer program code structured in computer program modules 41 10a-41 10e. Hence, in an exemplifying embodiment, the code means in the computer program of the arrangement 4100 in the WLAN node 3800 comprises an establishing unit, or module, for establishing an interface between the WLAN node and a wireless wide area network, WWAN, radio access node of a WWAN. The computer program further comprises a forwarding unit, or module, for forwarding a control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access and the established interface when WWAN radio access is unavailable to a wireless device.

[000286] The computer program modules could essentially perform the actions of the flow illustrated in figures 32a-32d, to emulate the WLAN node 3800. In other words, when the different computer program modules are executed in the processing unit 4106, they may correspond to the units 3803-3806 of figure 38.

[000287] Although the code means in the respective embodiments disclosed above in conjunction with figures 34, 36 and 38 are implemented as computer program modules which when executed in the respective processing unit causes the wireless device, the WWAN radio access node and the WLAN node

respectively to perform the actions described above in the conjunction with figures mentioned above, at least one of the code means may in alternative embodiments be implemented at least partly as hardware circuits.

[000288] The processor may be a single Central Processing Unit, CPU, but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuits, ASICs. The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-Access Memory RAM, Read-Only Memory, ROM, or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories within the wireless device, the WWAN radio access node and the WLAN node respectively. [000289] It is to be understood that the choice of interacting units, as well as the naming of the units within this disclosure are only for exemplifying purpose, and nodes suitable to execute any of the methods described above may be configured in a plurality of alternative ways in order to be able to execute the suggested procedure actions.

[000290] Exemplifying embodiments herein also relate to a method performed by a wireless device operable in a WWAN and a WLAN employing different RATs. The method may comprise establishing a WLAN radio access with a WLAN node, and establishing a radio access with a WWAN radio access node. When WWAN radio access is unavailable to the wireless device, the method comprises transmitting and/or receiving a control signalling plane message to and/or from a WWAN radio access node via the WLAN node.

[000291 ] Exemplifying embodiments herein also relate to a method performed by a WWAN radio access node operable in a WWAN. The method comprises establishing a radio access with a wireless device, and establishing an interface between the WWAN radio access node and a WLAN, node of a WLAN. When WWAN radio access is unavailable to the wireless device, the method comprises transmitting and/or receiving a control signalling plane message to or from the wireless device via WLAN radio access, by transmitting or receiving the control signalling plane message via the established interface.

[000292] Exemplifying embodiments herein also relate to a method performed by a WLAN node operable in a WLAN. The method comprises establishing a radio access with a wireless device, and establishing an interface between the WLAN node and a WWAN radio access node of a WWAN. When WWAN radio access is unavailable to the wireless device, the method comprises forwarding a control signalling plane message between the wireless device and the WWAN radio access node via WLAN radio access and the established interface.

[000293] It should also be noted that the units described in this disclosure are to be regarded as logical entities and not with necessity as separate physical entities. [000294] While the embodiments have been described in terms of several embodiments, it is contemplated that alternatives, modifications, permutations and equivalents thereof will become apparent upon reading of the specifications and study of the drawings. It is therefore intended that the following appended claims include such alternatives, modifications, permutations and equivalents as fall within the scope of the embodiments and defined by the pending claims.