WO2016144240A1

WO2016144240A1 - Mobility during traffic aggregation

Info

Publication number: WO2016144240A1
Application number: PCT/SE2016/050177
Authority: WO
Inventors: Oumer Teyeb; Filip MESTANOV; Jari Vikberg
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-03-12
Filing date: 2016-03-04
Publication date: 2016-09-15

Abstract

There is provided a method of operating a source node (10) in a first network that is operating according to a first radio access technology, RAT, wherein a terminal device (12) has one or more tight aggregation bearers through the source node (10) and a first node (14) in a second network that is operating according to a second RAT, the method comprising on or during handover of the terminal device (12) from the source node (10) to a target node (11) in the first network, sending information to the first node (14) or a control node (40) in the second network for the first node (14) for use in enabling the tight aggregation to be established through the target node (11) and the first node (14) following the handover.

Description

Mobility during traffic aggregation Technical Field

The disclosure relates to terminal devices that support multiple radio access technologies (RATs) and to mobility during traffic aggregation through nodes in multiple networks operating according to different RATs.

Background

The wireless local-area network (WLAN) technology known as "Wi-Fi" has been standardized by IEEE in the 802.11 series of specifications (i.e., as "IEEE Standard for Information technology— Telecommunications and information exchange between systems. Local and metropolitan area networks— Specific requirements. Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications').

The IEEE 802.11 specifications regulate the functions and operations of the Wi-Fi access points (APs) or wireless terminals, collectively known as "stations" or "STA," in the IEEE 802.1 1 , including the physical layer protocols, Medium Access Control (MAC) layer protocols, and other aspects needed to secure compatibility and inter-operability between access points and portable terminals. Wi-Fi is commonly used as wireless extensions to fixed broadband access, e.g., in domestic environments and in so-called hotspots, like airports, train stations and restaurants.

Recently, Wi-Fi has been subject to increased interest from cellular network operators, who are studying the possibility of using Wi-Fi for purposes beyond its conventional role as an extension to fixed broadband access. These operators are responding to the ever-increasing market demands for wireless bandwidth, and are interested in using Wi-Fi technology as an extension of, or alternative to, cellular radio access network technologies (RATs). Cellular operators that are currently serving mobile users with, for example, any of the technologies standardized by the 3^rd-Generation Partnership Project 3GPP), including the radio-access technologies known as Long- Term Evolution (LTE), Universal Mobile Telecommunications System (UMTSyWideband Code-Division Multiple Access (WCDMA), and Global System for Mobile Communications (GSM), see Wi-Fi as a wireless technology that can provide good additional support for users in their regular cellular networks. Within the scope of 3GPP Release-13, there has been a growing interest in realizing even tighter integration/aggregation between 3GPP-specified networks and WLAN (for example in "LTE-WLAN Radio Level Integration and Interworking Enhancement", 3GPP RP-150262). For example, in the same way as carrier aggregation between multiple carriers in 3GPP, tighter integration/aggregation between 3GPP and WLAN means that the WLAN is used as just another carrier for the terminal device. Such an aggregation is expected to make it possible for a more optimal aggregation opportunity as compared to multipath transmission control protocol (MPTCP), as the aggregation is performed at a lower layer and as such the scheduling and flow control of the data on the WLAN and 3GPP links can be controlled by considering dynamic radio network conditions. The term 'tight aggregation' is used in this document to refer to the aggregation of at least one carrier in the 3GPP network and at least one carrier in the WLAN, i.e. aggregation of carriers through networks operating according to different radio access technologies (RATs). Alternative terms to 'tight aggregation' include 'radio level aggregation' and 'lower layer aggregation'.

Figure 1 illustrates the protocol stack of a user equipment (UE - the 3GPP term for terminal device), with three different protocol options of aggregation: at the packet data convergence protocol, PDCP, level (Figure 1 (a)), radio link protocol, RLC, level (Figure 1 (b)) and medium access control, MAC, level (Figure 1 (c)). The figure shows the main principles for these three aggregation levels and additional functionality that may be needed. For example in the PDCP-level aggregation, an additional protocol layer may be used between the PDCP layer and the 802.2 LLC (logical link control) layer to convey information about the UE and the radio bearer the traffic is associated with (this additional protocol layer is shown as "Glue-1" in Figures 2(a) and 2(b)).

In the case of a standalone AP and eNB - a radio access network node in LTE - (i.e. where the AP and eNB are non co-located), the protocol stack for supporting aggregation is a little bit different, as the LLC frames have now to be relayed towards the standalone eNB. Figure 2(a) illustrates this for the case of PDCP level aggregation. In this case, once the LLC packet is decoded at the AP (in the uplink direction from the UE to the AP), and the AP realizes that this packet is a PDCP packet that has to be routed to an eNB, the forwarding can be performed via normal TCP/IP (transmission control protocol/Internet protocol) protocol stack. Figure 2(b) shows PDCP level aggregation with a co-located/combined eNB and AP. In current evolved packet core (EPC) systems, a control entity in the radio access network (RAN), such as the serving eNB for the UE, decides when the UE shall perform a handover from the serving eNB (also referred to herein as the source eNB) to another eNB (called target eNB in the context of handover). The eNB is aware of (radio) bearers but not of PDN (packet data network) connections or IP flows. The decision made in the RAN is based on multiple inputs with the main goal to maximize the number of satisfied users in the network. The input information consists, for example, of radio network topology information; radio link quality for the UE in the current cell and other cells as measured by the UE; Cell Load in the current cell for the UE and in other cells as measured by the UE; UE capabilities; Cell capabilities (current cell and other cells as measured by the UE); UE activity/traffic volume; and/or subscription based information (received from the core network (CN)).

The handover from source eNB to target eNB can be performed in different ways using either S1 -based handover or X2-based handover procedures. The names of these procedures indicate the interface(s) used for the handover preparation signalling between the source and the target eNBs. In the X2-based handover the handover preparation is performed directly using an X2-interface between the source and target eNBs. In S1-based handover the MME relays the signalling between the source and target eNBs using two different S1 -interfaces.

Typically, WLAN mobility (i.e. moving between WLANs) is controlled by the STA/UE. This means that the STA decides when it is time to leave a WLAN AP and connect to another WLAN AP. In existing WLAN deployments it is typical that the STA (UE) needs to perform full authentication when it moves to another WLAN AP. IEEE 802.1 1 r (now part of IEEE 802.1 1-2012) introduces a "Fast BSS Transition" management feature to support seamless handovers between APs. In that way, when a STA performs a handover between different APs that are part of the same mobility domain, it will not need to perform a complete authentication with the target AP, but only renew the over- the-air encryption.

Figure 3 illustrates an evolved UMTS Terrestrial Radio Access Network (EUTRAN) architecture as part of an LTE-based communications system 2 and a WLAN 3 in which tight aggregation can be used. Figure 3 is described in more detail later, but for the purposes of this discussion, the LTE network 2 consists of a single UE 12, two eNodeBs (eNB1 - 10 and eNB2 - 1 1), two WLAN APs (AP1 - H and AP2 - 15) and on the core network 4 side only an MME 6 and the SGW 8 are shown. The tight aggregation solution is enabled between the eNBs 10, 11 and the APs 14, 15 so that both APs are connected to both eNBs. This is shown by the Tight Aggregation (TA) interface between the eNBs and APs. Other interfaces shown are the S1-MME (the S1 interface between the MME 6 and the eNBs 10, 1 1), S1-U (the S1 interface between the SGW 8 and eNBs 10, 1 1) and X2 interfaces. The TA interface between the eNBs and APs may be based on additional functionality on the Xw-interface currently being discussed in 3GPP. Figure 4(a) shows a specific case of the tight aggregation solution in a simplified version of Figure 3 (i.e. the inter-node interfaces from Figure 3 have been omitted). The UE 12 is connected to both eNB1 10 and AP1 14 and tight aggregation has been activated for at least one bearer for the UE 12 (the bearer being shown by the lines from the UE 12 to eNB1 and from the UE 12 through AP1 14 to eNB1 10 and from eNB1 to SGW 8 in Figure 4(a)). Although not shown in Figure 4, there will also be a signalling/control plane bearer between MME 6, eNB1 10 and the UE 12.

The UE 12 is in most cases a mobile device (i.e. it can move around the coverage area of the network 2/WLAN 3) and there are different mobility scenarios that may take place from the scenario shown in Figure 4(a).

The UE 12 may be handed over on the LTE-side from eNB1 10 to eNB2 1 1 as shown in Figure 4(b) so that the tight aggregated bearer is from UE 12 to eNB2 1 1 and from the UE 12 through AP1 14 and from eNB2 11 to SGW 8.

The UE 12 may move from AP1 14 to AP2 15 on WLAN-side as shown in Figure 4(c) so that the tight aggregated bearer is from UE 12 to eNB1 10 and from UE 12 through AP2 15 to eNB1 10, and from eNB1 10 to SGW 8. In addition, it is also possible that mobility on both the LTE and WLAN sides takes place simultaneously. The main reason for this is that the eNB 10 controls mobility on LTE-side and the UE 12 typically controls mobility on WLAN side. This is shown in Figure 4(d) where the tight aggregated bearer is via AP2 15 and eNB2 after the dual handover.

Summary When any of the above described mobility scenarios takes place it is desired to recreate the tight aggregation association between the eNB and the AP. For example, when UE 12 is handed over from eNB1 10 to eNB2 1 1 , the tight aggregation association between eNB1 10 and AP1 14 needs to be established between eNB2 11 and AP1 14. If this is not performed in a controlled way and integrated with the mobility signalling in the different mobility scenarios, service interruption for the UE 12 may take place (for example in the form of packet losses). The techniques presented herein provide solutions to this problem. According to a first aspect, there is provided a method of operating a terminal device that has one or more tight aggregation bearers through a source node in a first network that is operating according to a first RAT and a first node in a second network that is operating according to a second RAT, with the method comprising, on or during handover of the terminal device from the source node to a target node in the first network, sending information to another node for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

Various embodiments of the first aspect are set out below. The described embodiments can be used individually or in any combination.

In various embodiments the information is sent to (i.e. the 'another node' is) one or more of the source node, the target node, the first node in the second network, a control node (in the first network) for the source node, a control node (in the first network) for the target node and a control node (in the second network) for the first node in the second network.

In various embodiments the method further comprises the step of initiating the handover of the terminal device from the source node to the target node. In various embodiments the step of sending information is performed on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network. According to a second aspect, there is provided a terminal device that is adapted to operate with one or more tight aggregation bearers through a source node in a first network that is operating according to a first RAT and a first node in a second network that is operating according to a second RAT, with the terminal device being adapted (or one or more components of the terminal device being adapted) to send information to another node on or during handover of the terminal device from the source node to a target node in the first network for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

According to a third aspect, there is provided a terminal device that is adapted to operate with one or more tight aggregation bearers through a source node in a first network that is operating according to a first RAT and a first node in a second network that is operating according to a second RAT, wherein the terminal device comprises a processor and a memory, said memory containing instructions executable by said processor whereby said terminal device is operative to send information to another node on or during handover of the terminal device from the source node to a target node in the first network for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

According to a fourth aspect, there is provided a terminal device that is adapted to operate with one or more tight aggregation bearers through a source node in a first network that is operating according to a first RAT and a first node in a second network that is operating according to a second RAT, with the terminal device comprising a first module configured to send information to another node on or during handover of the terminal device from the source node to a target node in the first network for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

Various embodiments of the terminal device corresponding to the above method embodiments are also contemplated. According to a fifth aspect, there is provided a method of operating a source node in a first network that is operating according to a first RAT, wherein a terminal device has one or more tight aggregation bearers through the source node and a first node in a second network that is operating according to a second RAT, the method comprising, on or during handover of the terminal device from the source node to a target node in the first network, one or both of the steps of: sending information for use in enabling the tight aggregation to be established through the target node and the first node following the handover; and receiving information for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

Various embodiments of the fifth aspect are set out below. The described embodiments can be used individually or in any combination.

In various embodiments the information is sent to one or more of the target node, the first node in the second network, a control node (in the first network) for the source node, a control node (in the first network) for the target node and a control node (in the second network) for the first node in the second network.

In various embodiments the information can be received from the terminal device or a control node for the source node. In various embodiments the method further comprises the step of initiating the handover of the terminal device from the source node to the target node.

In various embodiments the step of sending information, and/or the step of receiving is performed on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network.

According to a sixth aspect, there is provided a source node for use in a first network that is operating according to a first RAT, wherein a terminal device has one or more tight aggregation bearers through the source node and a first node in a second network that is operating according to a second RAT, the source node being adapted (or one or more components of the source node being adapted) to do one or both of: send information for use in enabling the tight aggregation to be established through a target node in the first network and the first node following a handover of the terminal device from the source node to the target node; and receive information for use in enabling the tight aggregation to be established through a target node in the first network and the first node following a handover of the terminal device from the source node to the target node. According to a seventh aspect, there is provided a source node for use in a first network that is operating according to a first RAT, wherein a terminal device has one or more tight aggregation bearers through the source node and a first node in a second network that is operating according to a second RAT, wherein the source node comprises a processor and a memory, said memory containing instructions executable by said processor whereby said source node is operative to do one or both of: send information for use in enabling the tight aggregation to be established through a target node in the first network and the first node following a handover of the terminal device from the source node to the target node; and receive information for use in enabling the tight aggregation to be established through a target node in the first network and the first node following a handover of the terminal device from the source node to the target node.

According to an eighth aspect, there is provided a source node for use in a first network that is operating according to a first RAT, wherein a terminal device has one or more tight aggregation bearers through the source node and a first node in a second network that is operating according to a second RAT, the source node comprising one or more of a first module configured to send information for use in enabling the tight aggregation to be established through a target node in the first network and the first node following a handover of the terminal device from the source node to the target node; and a second module configured to receive information for use in enabling the tight aggregation to be established through a target node in the first network and the first node following a handover of the terminal device from the source node to the target node.

Various embodiments of the source node corresponding to the above method embodiments are also contemplated.

According to a ninth aspect, there is provided a method of operating a target node in a first network that is operating according to a first RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in the first network and a first node in a second network that is operating according to a second RAT, the method comprising, on or during handover of the terminal device from the source node to the target node, one or both of the steps of: receiving information for use in enabling the tight aggregation to be established through the target node and the first node following the handover; and establishing the tight aggregation for the terminal device with the first node following a handover of the terminal device from the source node to the target node. Various embodiments of the ninth aspect are set out below. The described embodiments can be used individually or in any combination. In various embodiments the information is received from one or more of the terminal device, the source node, the first node in the second network, a control node (in the first network) for the source node, a control node (in the first network) for the target node and a control node (in the second network) for the first node in the second network.

In various embodiments the step of establishing the tight aggregation comprises sending a signal to the first node or a control node for the first node to establish the tight aggregation with the first node. In various embodiments the step of establishing is performed after receiving the information.

In various alternative embodiments, the step of establishing the tight aggregation comprises receiving a signal from the first node or a control node for the first node to establish the tight aggregation with the first node.

In various embodiments the step of receiving and/or the step of establishing is performed on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network.

According to a tenth aspect, there is provided a target node for use in a first network that is operating according to a first RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in the first network and a first node in a second network that is operating according to a second RAT, the target node being adapted (or one or more components of the target node being adapted) to do one or both of: receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and establish the tight aggregation for the terminal device with the first node following a handover of the terminal device from the source node to the target node. According to an eleventh aspect, there is provided a target node for use in a first network that is operating according to a first RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in the first network and a first node in a second network that is operating according to a second RAT, wherein the target node comprises a processor and a memory, said memory containing instructions executable by said processor whereby said target node is operative to do one or both of: receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and establish the tight aggregation for the terminal device with the first node following a handover of the terminal device from the source node to the target node.

According to a twelfth aspect, there is provided a target node for use in a first network that is operating according to a first RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in the first network and a first node in a second network that is operating according to a second RAT, the target node comprising one or more of a first module configured to receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and a second module configured to establish the tight aggregation for the terminal device with the first node following a handover of the terminal device from the source node to the target node. Various embodiments of the target node corresponding to the above method embodiments are also contemplated.

According to a thirteenth aspect, there is provided a method of operating a first node in a second network that is operating according to a second RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network operating according to a first RAT and the first node, the method comprising, on or during handover of the terminal device from the source node to the target node, one or both of the steps of: receiving information for use in enabling the tight aggregation to be established through the target node and the first node following the handover; and establishing the tight aggregation for the terminal device with the target node following a handover of the terminal device from the source node to the target node.

Various embodiments of the thirteenth aspect are set out below. The described embodiments can be used individually or in any combination.

In various embodiments the information is received from one or more of the terminal device, the source node, the target node, a control node (in the first network) for the source node, a control node (in the first network) for the target node and a control node (in the second network) for the first node in the second network.

In various embodiments the step of establishing the tight aggregation comprises sending a signal to the target node or a control node to establish the tight aggregation with the target node.

In various embodiments the step of establishing is performed after receiving the information.

In various alternative embodiments, the step of establishing the tight aggregation comprises receiving a signal from the target node or a control node for the target node to establish the tight aggregation with the target node.

According to a fourteenth aspect, there is provided a first node for use in a second network that is operating according to a second RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network operating according to a first RAT and the first node, the first node being adapted (or one or more components of the first node being adapted) to do one or more of the following: receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and establish the tight aggregation for the terminal device with the target node following a handover of the terminal device from the source node to the target node.

According to a fifteenth aspect, there is provided a first node for use in a second network that is operating according to a second RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network operating according to a first RAT and the first node, wherein the first node comprises a processor and a memory, said memory containing instructions executable by said processor whereby said first node is operative to do one or more of: receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and establish the tight aggregation for the terminal device with the target node following a handover of the terminal device from the source node to the target node.

According to a sixteenth aspect, there is provided a first node for use in a second network that is operating according to a second RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network operating according to a first RAT and the first node, the first node comprising one or more of a first module configured to receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and a second module configured to establish the tight aggregation for the terminal device with the target node following a handover of the terminal device from the source node to the target node.

Various embodiments of the first node corresponding to the above method embodiments are also contemplated. According to a seventeenth aspect, there is provided a method of operating a control node in a network, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network that is operating according to a first RAT and a first node in a second network that is operating according to a second RAT, wherein the control node is a control node for one or more of the source node, the first node in the second network and a target node in the first network, the method comprising, on or during handover of the terminal device from the source node to the target node, one or more of the steps of: sending information to another node for use in enabling the tight aggregation to be established through the target node and the first node following the handover; receiving information for use in enabling the tight aggregation to be established through the target node and the first node following the handover; and establishing the tight aggregation for the terminal device with the target node and the first node following the handover.

Various embodiments of the seventeenth aspect are set out below. The described embodiments can be used individually or in any combination.

In various embodiments the information is received from one or more of the terminal device, the source node, the target node, the first node in the second network, a control node (in the first network) for the source node, a control node (in the first network) for the target node and a control node (in the second network) for the first node in the second network.

In various embodiments the step of establishing the tight aggregation comprises sending a signal to the first node, the target node, a control node for the first node, or a control node for the target node to establish the tight aggregation between the first node and the target node.

In various alternative embodiments, the step of establishing the tight aggregation comprises receiving a signal from the first node, the target node, a control node for the first node or a control node for the target node to establish the tight aggregation with the first node. In various embodiments the method further comprises the step of initiating the handover of the terminal device from the source node to the target node.

In various embodiments any one or more of the steps of the method are performed on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network.

According to an eighteenth aspect, there is provided a control node for use in a network, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network that is operating according to a first RAT and a first node in a second network that is operating according to a second RAT, wherein the control node is a control node for one or more of the source node, the first node in the second network and a target node in the first network, the control node being adapted (or one or more components of the control node being adapted) to do one or more of: send information to another node for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and establish the tight aggregation for the terminal device with the target node and the first node following a handover of the terminal device from the source node to the target node. According to a nineteenth aspect, there is provided a control node for use in a network, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network that is operating according to a first RAT and a first node in a second network that is operating according to a second RAT, wherein the control node is a control node for one or more of the source node, the first node in the second network and a target node in the first network, wherein the control node comprises a processor and a memory, said memory containing instructions executable by said processor whereby said control node is operative to do one or more of: send information to another node for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and establish the tight aggregation for the terminal device with the target node and the first node following a handover of the terminal device from the source node to the target node.

According to a twentieth aspect, there is provided a control node for use in a network, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network that is operating according to a first RAT and a first node in a second network that is operating according to a second RAT, wherein the control node is a control node for one or more of the source node, the first node in the second network and a target node in the first network, the control node comprising one or more of: a first module configured to send information to another node for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; a second module configured to receive information for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node; and a third module configured to establish the tight aggregation for the terminal device with the target node and the first node following a handover of the terminal device from the source node to the target node.

Various embodiments of the control node corresponding to the above method embodiments are also contemplated. According to a further aspect, there is provided a computer program product comprising a computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform any of the above method embodiments.

In any of the above aspects and embodiments, the information can comprise information that identifies any one or more of: the terminal device, the source node, the target node, the first node in the second network, a control node (in the first network) for the source node, a control node (in the first network) for the target node and a control node (in the second network) for the first node in the second network. In any of the above aspects and embodiments, the information can comprise or further comprise any one or more of: information that identifies a bearer or bearers for which tight aggregation is activated, information required to establish and/or use an interface between the target node and the first node in the second network, and a security key used by the source node and the first node in the second network.

In any of the above aspects and embodiments, the information can be provided in one or more information elements, lEs. In any of the above aspects and embodiments, the information can comprise any information required to establish tight aggregation for the target node and first node in the second network.

In any of the above aspects and embodiments, the first RAT can be a 3GPP-specified RAT or a non-3GPP specified RAT. The first RAT can be any one of Wi-Fi, Long-Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS), Wideband Code-Division Multiple Access (WCDMA), Global System for Mobile Communications (GSM), or Worldwide Interoperability for Microwave Access (WMAX). In any of the above aspects and embodiments, the second RAT can be a 3GPP- specified RAT or a non-3GPP specified RAT. The second RAT can be any one of Wi- Fi, Long-Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS), Wideband Code-Division Multiple Access (WCDMA), Global System for Mobile Communications (GSM), or Worldwide Interoperability for Microwave Access (WMAX).

In any of the above aspects and embodiments, one of the first RAT and second RAT is LTE, and the other one of the first RAT and second RAT is W-Fi.

In any of the above aspects and embodiments, the source node can be any of a base station, eNodeB, eNB, NodeB, macro/micro/pico/femto radio base station, access point (AP), Access Controller (AC), home eNodeB, femto base station, relay, repeater, sensor, a transmitting-only radio node and a receiving-only radio node.

In any of the above aspects and embodiments, the target node can be any of a base station, eNodeB, eNB, NodeB, macro/micro/pico/femto radio base station, access point (AP), Access Controller (AC), home eNodeB, femto base station, relay, repeater, sensor, a transmitting-only radio node and a receiving-only radio node.

In any of the above aspects and embodiments, the first node in the second network can be any of a base station, eNodeB, eNB, NodeB, macro/micro/pico/femto radio base station, access point (AP), Access Controller (AC), home eNodeB, femto base station, relay, repeater, sensor, a transmitting-only radio node and a receiving-only radio node. Brief Description of the Drawings

Features, objects and advantages of the presently disclosed techniques will become apparent to those skilled in the art by reading the following detailed description where references will be made to the appended figures in which: Figures 1 (a)-(c) illustrates a UE protocol stack for different levels of tight aggregation;

Figure 2(a) and (b) illustrate PDCP level aggregation for a standalone AP and eNB and co-located/combined eNB; Figure 3 is a block diagram illustrating an LTE network and WLAN;

Figures 4(a)-(d) illustrate different mobility scenarios;

Figure 5 is a block diagram of a terminal device according to an embodiment;

Figure 6 is a block diagram of a RAN node according to an embodiment;

Figure 7 is a block diagram of a control node according to an embodiment; Figure 8 illustrates the signalling between various nodes for an LTE mobility scenario;

Figures 9(a)-(c) illustrate various embodiments of the signalling between nodes for establishing tight aggregation in an LTE mobility scenario; Figure 10 illustrates the signalling between various nodes for a WLAN mobility scenario; and Figures 1 1 (a)-(g) illustrate various embodiments of the signalling between nodes for establishing tight aggregation in a WLAN mobility scenario. Detailed Description

The following sets forth specific details, such as particular embodiments for purposes of explanation and not limitation. But it will be appreciated by one skilled in the art that other embodiments may be employed apart from these specific details. In some instances, detailed descriptions of well known methods, nodes, interfaces, circuits, and devices are omitted so as not obscure the description with unnecessary detail. Those skilled in the art will appreciate that the functions described may be implemented in one or more nodes using hardware circuitry (e.g., analog and/or discrete logic gates interconnected to perform a specialized function, ASICs, PLAs, etc.) and/or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. Nodes that communicate using the air interface also have suitable radio communications circuitry. Moreover, the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor and also in some cases a transceiver component, or a receiver component and/or transmitter component to carry out the techniques described herein.

Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

In terms of computer implementation, a computer is generally understood to comprise one or more processors, one or more processing units, one or more processing modules or one or more controllers, and the terms computer, processor, processing unit, processing module and controller may be employed interchangeably. When provided by a computer, processor, processing unit, processing module or controller, the functions may be provided by a single dedicated computer, processor, processing unit, processing module or controller, by a single shared computer, processor, processing unit, processing module or controller, or by a plurality of individual computers, processors, processing units, processing modules or controllers, some of which may be shared or distributed. Moreover, the terms "processor", "processing unit", "processing module" or "controller" also refer to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

Although the description is given for a terminal device or user equipment (UE), it should be understood by the skilled in the art that "terminal device" and "UE" are non-limiting terms comprising any mobile, non-mobile or wireless device or node equipped with a radio interface allowing for at least one of: transmitting signals in uplink (UL) and receiving and/or measuring signals in downlink (DL). A UE herein may comprise a UE (in its general sense) capable of operating or at least performing measurements in one or more frequencies, carrier frequencies, component carriers or frequency bands. It is typically a UE operating in a multi-radio access technology (RAT) or multi-standard mode (although single RAT-mode operation may also be possible). As well as "UE" and "terminal device", the term "mobile device" is used interchangeably in the following description, and it will be appreciated that such a device does not necessarily have to be mobile in the sense that it is carried by a user. Instead, the term "mobile device", as with "terminal device", encompasses any device that is capable of communicating with communication networks that operate according to one or more mobile communication standards, such as GSM, UMTS, LTE, Wi-Fi, etc.

A cell is associated with a radio access network (RAN) node, where a RAN node comprises in a general sense any node transmitting radio signals in the downlink (DL) to a terminal device and/or receiving radio signals in the uplink (UL) from a terminal device. Some example RAN nodes, or terms used for describing RAN nodes, are base station, eNodeB, eNB, NodeB, macro/micro/pico/femto radio base station, access point (AP), Access Controller (AC), home eNodeB (also known as femto base station), relay, repeater, sensor, transmitting-only radio nodes or receiving-only radio nodes. A RAN node may operate or at least perform measurements in one or more frequencies, carrier frequencies or frequency bands and may be capable of carrier aggregation. It may also be a single-radio access technology (RAT), multi-RAT, or multi-standard node, e.g., using the same or different base band circuitry for different RATs. It should be noted that unless otherwise indicated, the use of the general term "network node" as used herein refers to a RAN node in a telecommunication network, such as a base station, an eNodeB, a network node in the RAN responsible for resource management, such as a radio network controller (RNC), a core network node, such as a mobility management entity (MME) or SGW, or a WLAN Access Point (AP), a WLAN access controller (AC) or any other type of WLAN node in which the WLAN Termination (WT) is implemented, the WT being the logical entity in which the Xw interface between the WLAN and the mobile communication network is terminated.

The signalling described is either via direct links or logical links (e.g. via higher layer protocols and/or via one or more network nodes). For example, signalling from a coordinating node may pass another network node, e.g., a radio node.

As noted above, Figure 3 shows an exemplary diagram of an evolved UMTS Terrestrial Radio Access Network (EUTRAN) architecture as part of an LTE-based communications system 2. Nodes in the core network 4 include one or more Mobility Management Entities (MMEs) 6, a key control node for the LTE access network, and one or more Serving Gateways (SGWs) 8 which route and forward user data packets while acting as a mobility anchor. They communicate with base stations 10, 11 in the RAN referred to in LTE as eNBs or eNodeBs, over an interface, for example an S1 interface. The eNBs 10, 11 can include the same or different categories of eNBs, e.g. macro eNBs, and/or micro/pico/femto eNBs. The eNBs 10, 1 1 communicate with each other over an interface, for example an X2 interface. The S1 interface and X2 interface are defined in the LTE standard. A UE 12 can receive downlink data from and send uplink data to one of the base stations 10, 1 1 with that base station 10, 1 1 being referred to as the serving base station (or source base station) of the UE 12. Two access points (APs) 14, 15 that are part of a WLAN 3 are also shown in Figure 3, although it will be appreciated that the WLAN 3 and APs 14, 15 are not part of the EUTRAN architecture.

In order to implement the various embodiments described herein, a communication path is required between the WLAN AP 14 and the nodes 10 in the LTE network 2 so that tight aggregation (TA) can be established for the UE 12 via a node in the LTE network 2 and a node in the WLAN 3. This communication path/interface is shown as a TA interface in Figure 3 (although another type of interface could be used), and it will be appreciated that this connection would typically be established via the WLAN AP's 14, 15 broadband connection, rather than there being a direct (e.g. air interface) signalling connection between the AP 14, 15 and eNB 10, 1 1. It will also be appreciated that where an AP 14, 15 is within the coverage area of several eNBs 10, the AP 14, 15 may have separate interfaces to each of those eNBs 10, 1 1.

Although embodiments of the techniques presented herein are described with reference to scenarios based on Figure 3 (i.e. with tight aggregation established between LTE and WLAN), it will be appreciated that the techniques are not limited to these types of radio access technology (RAT), and the techniques can be applied to tight aggregation via any two types of RAT, such as WLAN and any other type of 3GPP-specified RAT (e.g. UMTS); WLAN and any type of non-3GPP-specified RAT (e.g. Worldwide Interoperability for Microwave Access (WiMAX)); or between two types of 3GPP-specified Rat (e.g. LTE and UMTS).

Figure 5 shows a terminal device 12 or user equipment (UE) that can be adapted for use in one or more of the non-limiting example embodiments described. The terminal device 12 comprises a processing unit 22 that controls the operation of the terminal device 12. The processing unit 22 is connected to receiver circuitry, transmitter circuitry or transceiver circuitry 24 (which comprises a receiver and a transmitter) with associated antenna(s) 26 which are used to receive signals from or both transmit signals to and receive signals from two different types of radio access network (i.e. two radio access networks that are operating according to different radio access technologies, RATs), such as RAN node 10 in the LTE network 2 and access point (AP) 14 in a WLAN 3. The terminal device 12 also comprises a memory unit 28 that is connected to the processing unit 22 and that stores computer program code and other information and data required for the operation of the terminal device 12.

Figure 6 shows a RAN node 10, 14 (for example a base station, NodeB, an eNodeB or an AP) that can be adapted for use in example embodiments described. The RAN node 10 comprises a processing unit 32 that controls the operation of the base station 10, 14. The processing unit 32 is connected to receiver circuitry, transmitter circuitry or transceiver circuitry 34 (which comprises a receiver and a transmitter) with associated antenna(s) 35 which are used to transmit signals to, and receive signals from, terminal devices 12 in the network 2. The RAN node 10 also includes inter-node interface circuitry 36 for allowing the RAN node 10 to exchange information with other nodes operating according to the same or a different RAT (e.g. in a 3GPP RAN, a core network or a WLAN). The inter-node interface circuitry 36 can therefore be adapted to communicate via an X2 interface, S1 interface, TA interface, etc. The RAN node 10, 14 also comprises a memory unit 38 that is connected to the processing unit 32 and that stores computer program code and other information and data required for the operation of the RAN node 10, 14. It will be appreciated that RAN nodes adapted for use in certain types of network (e.g. UTRAN or WCDMA RAN) will include similar components to those shown in Figure 6 and appropriate interface circuitry 36 for enabling communications with the other network nodes in those types of networks (e.g. other base stations, mobility management nodes and/or nodes in the core network).

Figure 7 shows a control node 40 that can be used in the example embodiments described. The control node 40 can be a node that controls the operations of one or more RAN nodes 10, 14. For example, the control node 40 can be a WLAN Access Controller (AC) that controls the operation of one or more WLAN APs 14, 15 and that communicates with a node in the 3GPP RAN, such as an eNB 10, 1 1 , for example via a TA interface, or the control node 40 can be any other type of WLAN node in which the WT is implemented and that communicates with a node in the 3GPP RAN. Alternatively the control node 40 can be a core network node, such as an MME 6 or SGW 8. The control node 40 comprises a processing unit 42 that controls the operation of the control node 40. The processing unit 42 is connected to inter-node interface circuitry 44 for allowing the control node 40 to exchange information with RAN nodes 10, 11 with which it is associated (e.g. via a TA interface). The control node 40 also comprises a memory unit 46 that is connected to the processing unit 42 and that stores computer program code and other information and data required for the operation of the control node 40. It will be appreciated that only the components of the terminal device 12, RAN node 10, 14 and control node 40 required to explain the embodiments presented herein are illustrated in Figures 5, 6 and 7.

As noted above, when there is mobility for any of the RAN nodes involved in a tight aggregation situation (i.e. a situation where traffic is aggregated over carriers through two networks operating according to different RATs), it is desired to recreate the tight aggregation association between the target RAN node and other RAN node. For example, referring to the example in Figures 4(a) and 4(b), when UE 12 is handed over from eNB1 10 to eNB2 1 1 , the tight aggregation association between eNB1 10 and AP1 14 needs to be established between eNB2 1 1 and AP1 14. If this is not performed in a controlled way and integrated with the mobility signalling in the different mobility scenarios, service interruption for the UE 12 may take place (for example in the form of packet losses). The techniques presented herein provide solutions to this problem.

In particular, various different solutions are described that provide seamless service continuity in a tightly integrated/aggregated pair of networks operating according to different RATs (e.g. WLAN and a 3GPP network that supports aggregation). The main principle is that information related to tight aggregation is signalled between nodes on or during handover from a source node to a target node, with this information allowing tight aggregation to be established or re-established with the target node and the node in the other network (that does not change in the mobility event and which the tight aggregation is established with prior to the mobility event). The methods proposed herein not only allow tight aggregation to continue working during or after mobility but also enable the fast re-establishment of the tight aggregation in relation to different types of mobility events. This will result in the reduction of service interruption/degradation time for the end users (by e.g. minimizing packet losses).

The following description of the solutions provided herein is divided into four sections. The first section relates to the mobility from eNB1 10 to eNB2 11 shown in Figure 4(b). The second section relates to the mobility from AP1 14 to AP2 15 shown in Figure 4(c). The third section relates to the mobility of both eNB1 10 to eNB 1 1 and AP1 14 to AP2 at generally the same time, or simultaneously. Finally, the fourth section relates to additional solutions for scenarios where the interface between an eNB and AP is via a Wi-Fi Access Controller (AC) node. As noted above, although the solutions are described with reference to LTE and WLAN, the solutions are applicable to tight aggregation in networks operating according to other RATs.

LTE-side mobility

As shown in Figure 4(b), the UE 12 is handed over on the LTE-side from eNB1 10 to eNB2 1 1 so that the tight aggregated bearer is from UE 12 to eNB2 1 1 and from the UE 12 through AP1 14 and from eNB2 to SGW 8.

Figure 8 illustrates the signalling between various nodes in the LTE network 2 and WLAN 3 before, during and after the handover. The initial situation in which the UE 12 is connected to both eNB1 10 and AP1 14 and tight aggregation has been activated for at least one bearer for the UE 12 is shown in box 801. Thus, the UE 12 has control plane signalling 802, 803 with MME 6 via eNB1 10. The UE 12 has a user plane connection with eNB1 10 (signal 804) and a user plane connection with AP1 14 (signal 805) and from AP1 14 to eNB1 (signal 806), with at least one user plane bearer for the UE 12 being tightly aggregated. There is also user plane bearer signalling from eNB1 10 to SGW 8 (signal 807).

The eNB1 10 determines that a handover to eNB2 1 1 should be performed (box 808). Part of the handover process that includes signalling for establishing tight aggregation (TA) after the handover is shown in box 809. Embodiments of this signalling are shown in Figure 9. Apart from the signalling shown in Figure 9, the rest of the X2 handover from eNB1 10 to eNB2 1 1 is conventional (indicated by box 810).

After the handover (which is generally shown in box 811), the UE 12 is connected to both eNB2 11 and AP1 14 and tight aggregation is still activated for at least one bearer for the UE 12. That is the UE 12 has control plane signalling 812, 813 with MME 6 via eNB2 1 1. The UE 12 has a user plane connection with eNB2 11 (signal 814) and a user plane connection with AP1 14 (signal 815) and from AP1 14 to eNB2 (signal 816), with at least one user plane bearer for the UE 12 being tightly aggregated. There is also user plane bearer signalling from eNB2 1 1 to SGW 8 (signal 817). Although an X2-based handover from eNB1 to eNB2 is shown in Figure 8, it will be appreciated that the handover can be either S1- or X2-based. The existing mechanisms in both of these handover variants handle the following:

a) The moving of the signalling/control plane connection/bearer from eNB1 to eNB2 (both between MME and eNB2 and between eNB2 and the UE).

b) The moving of the S1-U tunnel from SGW i.e. so that it gets routed from eNB1 to eNB2.

c) The moving of the LTE part of the tightly aggregated bearer from eNB1 to eNB2 (although the existing mechanisms do not cover the reestablishment of the tight aggregation once the bearer is moved).

Figure 9(a) illustrates a first embodiment of the signalling in box 809 of Figure 8 for establishing tight aggregation after the handover to eNB2. The signalling shown in Figure 9(a) provides for the moving of the WLAN-part of the tight aggregated bearer, and involves ensuring that the existing TA link between eNB1 and AP1 can be established between eNB2 and AP1 as part of the handover. Since eNB1 is controlling the handover (i.e. it is the existing serving/source node for UE 12) it knows the target node for the handover, eNB2, and is also aware of the tight aggregation of the at least one bearer. Thus, eNB1 sends TA information about the WLAN AP involved in TA (i.e. AP1) to eNB2 as part of the handover preparation (signal 901). In some embodiments the TA information can be sent with an X2AP Handover Request signal. eNB2 uses the received information to communicate with AP1 and establish the tight aggregation bearers (signal 902). eNB2 can then send a signal 903 to eNB1 to acknowledge receipt of the TA information and Handover Request signal. As described below, the main purpose of the TA information in signal 902 (which can be in the form of an Information Element, IE, is to enable eNB2 to contact AP1 during the X2 handover preparation to re-establish tight aggregation. As noted above, after signal 903, the rest of the X2 handover continues normally (box 810 in Figure 8) and after the handover, tight aggregation continues between eNB2 and AP1.

The TA information IE may contain any one or more of the following pieces of information:

a Transport network address for the AP1. This may consist of an IP-address and additional information like TCP or user datagram protocol (UDP) port numbers.

b Indication of which bearers of the total bearer configuration were activated for tight aggregation before the handover.

c Any additional information needed to establish the interface between eNB2 and AP1. For example, if eNB1 and AP1 have agreed on any specific "tunnel identifiers" for the TA-interface. The identity of the UE (on the 3GPP and/or WLAN side, or a common identity for both) can also be included.

d In addition, the IE may contain also a security key agreed between eNB1 and AP1. The purpose of this part of the information is to ensure that AP1 can verify that the eNB2 asking to reassociate tight aggregation is a real node that the eNB1 has contacted eNB2 via X2 handover. This is an example of the type of information that can be sent AP1 by eNB2 in signal 902.

A separate TA 'All Information' IE could also be included for information that contains all the information above. Another alternative is to distribute the above information in different lEs. For example, bearer-specific information (e.g. which bearer is to be aggregated or not) can be included in the Έ-RABs To Be Setup List' IE of the X2AP Handover Request Message (e.g. by setting a Boolean "aggregated" flag for each bearer), while the information related to the AP can be put in a separate IE.

Figure 9(b) illustrates an alternative embodiment of the signalling in box 810 of Figure 8. In this embodiment, eNB1 sends TA information about eNB2 to AP1 (signal 911). AP1 uses the received TA information to communicate with eNB2 (signal 912) to establish the tight aggregation bearers.

Figure 9(c) illustrates another alternative embodiment of the signalling in box 810 of Figure 8. In this embodiment, eNB1 sends TA information to both AP1 and eNB2. That is eNB1 sends information about AP1 to eNB2 (signal 921) and information about eNB2 to AP1 (signal 922). eNB2 and AP1 then communicate with each to establish the TA bearers (signal 923). In one example (which also applies to the embodiments in Figures 9(a) and (b) above), the tight aggregation bearer is first established between eNB2 and AP1 when both nodes have sent an indication that it is time to activate these bearers. This embodiment has an advantage over the embodiment shown in Figure 9(a) in that it enables faster switching (establishment) of the aggregated bearer. In particular, by sending information to AP1 about eNB2 and information to eNB2 about AP1 at the same time (or generally the same time), the path switch in both UL and DL directions can happen more quickly as AP1 could start forwarding UL data to eNB2 and eNB2 will be expecting to receive data from AP1 following receipt of the information about AP1 by eNB2. Thus, in this embodiment, eNB1 can act as a 'mediator' for the path switch, and signals 922 and 923 can be performed in parallel. Regarding the handling of UL packets from the UE 12, two alternatives can be envisioned:

1. After the establishment of the link between eNB2 and AP1 (signal 903, 912, 923), AP1 will start forwarding any uplink packet received from the concerned UE to eNB2 instead of eNB1.

2. Even after the establishment of the link between eNB2 and AP1 , AP1 can continue forwarding UL data to eNB1 , until the X2 handover is done. After the X2 handover is done, the source eNB1 can send an "UL path switch" command to the AP1 , and from there on AP1 can send the UL packets of the concerned UE to eNB2. WLAN-side mobility As shown in Figure 4(c), the UE 12 is handed over (or moves) on the WLAN-side from AP1 14 to AP2 15 so that the tight aggregated bearer is from UE 12 to eNB1 10 and from the UE 12 through AP2 15 and from eNB1 to SGW 8. Figure 10 illustrates the signalling between various nodes in the LTE network 2 and WLAN 3 before, during and after the handover. The initial situation in which the UE 12 is connected to both eNB1 10 and AP1 14 and tight aggregation has been activated for at least one bearer for the UE 12 is shown in box 1001. Thus, the UE 12 has control plane signalling 1002, 1003 with MME 6 via eNB1 10. The UE 12 has a user plane connection with eNB1 10 (signal 1004) and a user plane connection with AP1 14 (signal 1005) and from AP1 14 to eNB1 (signal 1006), with at least one user plane bearer for the UE 12 being tightly aggregated. There is also user plane bearer signalling from eNB1 10 to SGW 8 (signal 1007). Box 1008 concerns the signalling between the nodes required for initiating and completing the handover, including the establishment of the TA bearer with AP2. Embodiments of this signalling are shown in Figures 1 1 (a)-(g).

After the handover (which is generally shown in box 1009), the UE 12 is connected to both eNB1 10 and AP2 15 and tight aggregation is still activated for at least one bearer for the UE 12. That is the UE 12 has control plane signalling 1010, 101 1 with MME 6 via eNB2 1 1. The UE 12 has a user plane connection with eNB1 10 (signal 1012) and a user plane connection with AP2 15 (signal 1013) and from AP2 15 to eNB1 (signal 1014), with at least one user plane bearer for the UE 12 being tightly aggregated. There is also user plane bearer signalling from eNB1 10 to SGW 8 (signal 1015).

In this mobility scenario, eNB1 and all connections/bearers it has towards the UE and the core network remain unchanged, and the only change that needs to take place is the moving of the tightly aggregated bearers from eNB1 ->AP1 ->UE to eNB1 ^AP2^UE in the downlink (DL) and UE^AP1 ^eNB1 to UE^AP2^eNB1 in the uplink (UL). Several alternative embodiments for moving the TA bearer during WLAN mobility are shown in Figures 1 1 (a)-(g).

In some embodiments (those shown in Figures 1 1 (a)-(d)), the WLAN-side mobility is controlled by the UE 12. That is, the UE 12 decides when to move to a new AP, and is the entity that knows when the WLAN-side mobility happens. In a first embodiment, as shown in Figure 11 (a), the UE decides that it should move from AP1 to AP2 (box 1 101) and sends a signal to eNB1 that indicates the move to AP2 and TA information about AP2 (signal 1 102). In some embodiments this signal can be a RRC: WLAN Mobility Indication signal. eNB1 then contacts AP2 to establish TA (signal 1 103) and reconfigure the TA bearer(s) from AP1 to AP2.

An additional solution to avoid downlink packet losses (i.e. packets that were aggregated by eNB1 over AP1 but not yet acknowledged to the eNB1 e.g. on PDCP- level) can be implemented by eNB1. In particular, eNB1 can use signal 1102 as a trigger to resend these packets either over LTE or over WLAN. The resending over LTE can occur after signal 1 102 is received, whereas the resending over WLAN (via AP2) can only take place after TA has been established (signal 1 103). The UE may apply similar actions for the uplink, for example by resending not-yet-acknowledged packets sent over AP1 over LTE when moving to AP2 (or over WLAN AP2 after tight aggregation is established over AP2).

In a second embodiment, as shown in Figure 1 1 (b), the UE decides that it should move from AP1 to AP2 (box 1 11 1) and sends a signal to AP2 that indicates TA information about eNB1 (signal 1 112). AP2 then contacts eNB1 to inform eNB1 that the TA bearer(s) should be moved from AP1 to AP2 (signal 11 13).

In third and fourth embodiments, as shown in Figures 1 1 (c) and (d) respectively, the UE decides that it should move from AP1 to AP2 (box 1121 and box 1 131) and sends a signal to AP1 about the move to AP2 (signal 1122 and signal 1 132). AP1 then either sends the TA information to AP2 (signal 1 123 in Figure 11 (c)) so that AP2 can contact eNB1 to establish TA (signal 1 124), or sends the TA information to eNB1 (signal 1 133 in Figure 1 1 (d) so that eNB1 can contact AP2 to establish TA (signal 1134). In some embodiments (that are shown in Figure 1 1 (e)), the WLAN-side mobility is controlled by the LTE network (e.g. eNB1). In this case the UE could send WLAN measurement reports to eNB1 (signal 1 141) to enable eNB1 to take a decision on whether to move AP. Having made the decision to move (box 1 142), eNB1 can move the tightly aggregated bearer(s) from AP1 to AP2 by contacting AP2 (signal 1143). In other embodiments (shown in Figures 11 (f) and (g)), it is AP1 that controls the UE mobility. Thus, AP1 decides that the UE is to move to AP2 (box 1151 in Figure 11 (f) and box 1 161 in Figure 11 (g)) and AP1 either notifies eNB1 that the UE will be moving to AP2 by sending TA information to eNB1 (signal 1 152), so that eNB1 can reconfigure the tightly aggregated bearer(s) from AP1 to AP2 (signal 1153) or AP1 sends TA information about eNB1 to AP2 (signal 1 162) so that AP2 can contact eNB1 to move the TA bearer(s) to AP2 (signal 1163).

In some embodiments (not shown in Figure 1 1), it is possible that no explicit notification from one node to another is provided. In this case, the UE can complete the move to AP2, and then AP2 can recognize that a certain portion of the UE traffic that was moved from AP1 is tightly aggregated traffic. In this case, AP2 can either poll AP1 in order to receive more information with regard to which eNB the aggregation should be established with, or AP2 can establish the aggregation with an eNB used as a default option.

Dual mobility

In this scenario there is mobility on both the LTE and WLAN sides (possibly simultaneously). There are two main cases where this can happen, namely where an eNB and AP co-located or combined, and where the eNB and AP are standalone.

In the first case, where the eNB and AP are co-located/combined, and it is preferred that mobility takes place on both sides (i.e. LTE and WLAN) simultaneously. This preference is to avoid complex tight aggregation scenarios in which the LTE part is from another co-located/combined eNB/AP than the WLAN part. Typically in this scenario the eNB/LTE-side is controlling mobility on both sides. A solution to establish TA after the mobility is similar to the solution shown in Figure 9(a), i.e. the source eNB/AP forwards TA information to the target eNB/AP and then the target eNB/AP may utilize this information to configure tight aggregation to the internal AP part. The solutions in Figures 9(b) and (c) are also possible.

Alternatively in the case where WLAN mobility is AP/network controlled the source eNB can perform the LTE-side handover as shown in Figures 9(a)-(c). In addition, the source eNB can send a signal to the source AP (for example a handover notification message) and include information about the target AP in this signal. This solution is based on the source eNB knowing the target AP combined with the target eNB. Then the source AP can trigger a WLAN handover to the target AP. Finally, the target eNB and target AP can reconfigure the tight aggregation.

In the second case, where the eNB and AP are not co-located or combined, the solutions may become more complex since the APs and eNBs are standalone. As LTE-side mobility is controlled by eNB and WLAN-side mobility is (in some cases) controlled by the UE, there is no common node/function that is able to coordinate the mobility decisions and these can happen independently of each other. Therefore it is possible that LTE and WLAN side mobility can happen simultaneously.

In this case the eNB and AP may be configured to use one of the solutions shown in Figures 9(a)-(c) and Figures 1 1 (a)-(g) respectively for establishing TA after a mobility event, and in the case of dual mobility, the outcome depends on when and to which eNB the UE indication about WLAN mobility (signal 1102 in Figure 11 (a)) is sent (i.e. the outgoing eNB - eNB1 , or the target eNB - eNB2).

If the UE indication is sent to eNB1 after the X2AP Handover Request message (signal 901) is sent to eNB2, then additional solutions are needed. One such solution is that eNB1 simply forwards the UE indication about WLAN mobility to eNB2. Another solution is that eNB1 rejects the WLAN mobility indication from the UE, for example by indicating that LTE handover is in progress and that the indication should be sent to the target eNB. Yet another alternative is to inform the UE when a LTE-side handover is being initiated (e.g. just before the X2 handover request command (signal 901) is sent), so that the UE will postpone changing the WLAN AP before the LTE side handover is completed. Effectively this final alternative avoids dual (i.e. simultaneous) mobility occurring.

Alternatively, if the UE indication is sent to eNB2 after the LTE handover is completed, then no additional actions are needed.

Alternative solutions when a W-Fi Access Controller (AC) is present

The solutions and embodiments described in the preceding sections are based on there being a direct interface between eNBs and APs (e.g. the TA interface shown in Figure 3). Generally the principles of the solutions described above can be applied to scenarios in which there is a Wi-Fi Access Controller (AC) 40 or other type of control node 40 in which the WT is implemented between the eNB and AP, i.e. the interface is eNB^^AC^^AP instead of directly eNB^— >AP. It will be noted that in these embodiments, the UE 12 may have a user plane connection and/or a control plane connection through the AC 40/other type of control node 40 before and after the handover. The different solutions described above can be applied or modified as follows:

LTE-side mobility - In this case the tight aggregation is initially between UE<--»AP1 <--»AC<"»eNB1 and after the handover from eNB1 to eNB2, tight aggregation is between UE — >AP1 — >AC — >eNB2. Therefore the only update needed after the LTE-side handover is to update the interface above AC 40 towards eNB2. Thus, when eNB1 decides to perform a handover to eNB2, eNB1 includes information about AC in the TA information IE that is sent to eNB2 (signal 901), and eNB2 uses the received information to re-establish tight aggregation towards the AC. Alternatively, when eNB1 decides to perform a handover to eNB2, eNB1 can include information about eNB2 in a TA information IE that is sent to AP1 (i.e. similar to signal 911 in Figure 9(b)) and AP1 can forward the information to AC. In another alternative, eNB1 can include information about eNB2 in a TA information IE that is sent directly to the AC. In both cases, the AC can use the received information to re-establish TA towards eNB2.

WLAN-side mobility - There are different solutions depending on whether the target AP is controlled by the same AC as the source AP.

In the case where the same AC is controlling both the target and source APs, tight aggregation is initially between UE — >AP1 — >AC — >eNB1 and after the mobility from AP1 to AP2, tight aggregation is between UE^^AP2^^AC^^eNB1. Therefore the only update needed is to update the interface below AC towards AP2. This updating can be carried in similar ways to the solutions shown in Figures 1 1 (a)- (e), with the following modifications.

For the solution shown in Figure 1 1 (a), the UE can inform eNB1 about AP2 (e.g. signal 1 102), eNB1 can further inform the AC about AP2, and AC can then reconfigure the tightly aggregated bearer(s) from AP1 to AP2. For the solution shown in Figure 1 1 (b), the UE can inform AP2 about AC and then AP2 would contact AC to inform AC that the tightly aggregated bearer(s) should be moved from AP1 to AP2. For the solution in Figure 11 (c), it is possible for the UE to inform AP1 about the move to AP2, and then either AP1 informs AP2 about AC, or AP1 informs AC about AP2.

For the solution in Figure 1 1 (e) where eNB1 controls the mobility within the WLAN, the UE could send WLAN measurement reports to eNB1 (signal 1141) and then eNB1 would control the move from AP1 to AP2 (decision 1 142). In that case eNB1 can be configured to trigger AC to move the tightly aggregated bearer(s) from AP1 to AP2 as part of the decision to control WLAN mobility.

In the case where the mobility is AP/network controlled, the signalling relating to Wi-Fi handover/mobility can also be used to reconfigure the tightly aggregated bearer(s) from AP1 to AP2. Thus TA information can be included in the Wi-Fi handover/mobility signalling to enable this reconfiguration to be carried out.

In the case where different ACs are controlling the target and source APs, tight aggregation is initially between UE — >AP1 — >AC1 — >eNB1 and after the mobility from AP1 to AP2, tight aggregation is between UE^^AP2^^AC2^^eNB1. Therefore it is necessary to update both the interface below AC2 towards AP2 and the interface from AC2 towards eNB1. This updating can be carried in similar ways to the solutions shown in Figures 1 1 (a)-(e), with the following modifications.

For the solution in Figure 1 1 (a), the UE can inform eNB1 about AP2 (signal 1 102), and then eNB1 needs to first move the tightly aggregated bearer(s) from AC1 to AC2 and then inform AC2 about AP2 so that AC2 can reconfigure the tightly aggregated bearer(s) towards AP2.

For the solution in Figure 1 1 (b), the UE can inform AP2 about eNB1 (signal 11 12), AP2 can inform AC2 about eNB1 , and then AC2 would inform eNB1 that the tightly aggregated bearer(s) should be moved from AC1 to AC2. In addition, AC2 can then reconfigure the tightly aggregated bearer(s) towards AP2. For the solution in Figure 11 (c), the UE can inform AP1 and/or AC1 about the move to AP2 and/or AC2, and then either AC1 can inform AC2 about eNB1 , or AC1 can inform eNB1 about AC2. In addition, AC2 can then reconfigure the tightly aggregated bearer(s) towards AP2.

For the solution in Figure 1 1 (e), eNB1 is controlling the mobility within the WLAN. The UE can send WLAN measurement reports to eNB1 (signal 1141) and then eNB1 would control the move from AP1 to AP2 (decision box 1 141). eNB1 would also be able to move the tightly aggregated bearer(s) from AC1 to AC2 as part of the decision to control WLAN mobility. In addition, AC2 can then reconfigure the tightly aggregated bearer(s) towards AP2.

For the solution in Figure 1 1 (f) where the WLAN mobility is AP/network-controlled, the signalling relating to Wi-Fi handover/mobility is used to reconfigure the tightly aggregated bearer(s) from AP1/AC1 to AP2/AC2. Thus TA information can be included in the Wi-Fi handover/mobility signalling to enable this reconfiguring to be carried out.

Dual mobility - In the case of dual mobility on both LTE and WLAN, the solutions described in the preceding sections for LTE-side and WLAN-side mobility can be applied.

Thus, the methods and techniques described herein provide for traffic aggregation across networks operating according to different RATs to continue seamlessly even after a change of one or two of the nodes involved in the aggregation (e.g. an eNB and/or WLAN AP in the case of LTE and Wi-Fi).

Modifications and other variants of the described embodiment(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the embodiment(s) is/are not to be limited to the specific examples disclosed and that modifications and other variants are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method of operating a source node in a first network that is operating according to a first radio access technology, RAT, wherein a terminal device has one or more tight aggregation bearers through the source node and a first node in a second network that is operating according to a second RAT, the method comprising:

on or during handover of the terminal device from the source node to a target node in the first network, sending information to the first node or a control node in the second network for the first node for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

2. A method as defined in claim 1 , wherein the information comprises information that identifies any one or more of: the terminal device, the source node, the target node, the first node, and the control node.

3. A method as defined in claim 1 or 2, wherein the information comprises any one or more of:

information that identifies a bearer or bearers for which tight aggregation is activated,

information required to establish and/or use an interface between the target node and the first node in the second network, and

a security key used by the source node and the first node in the second network.

4. A method as defined in claim 1 , 2 or 3, wherein the information is provided in one or more information elements, lEs.

5. A method as defined in any of claims 1-4, wherein the method further comprises the step of:

initiating the handover of the terminal device from the source node to the target node.

6. A method as defined in any of claims 1-5, wherein the method further comprises the step of:

on or during the handover of the terminal device from the source node to the target node, sending information to the target node for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

7. A method as defined in any of claims 1-6, wherein the step of sending information is performed on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network.

8. A source node for use in a first network that is operating according to a first radio access technology, RAT, wherein a terminal device has one or more tight aggregation bearers through the source node and a first node in a second network that is operating according to a second RAT, the source node being adapted to:

send information to the first node or a control node in the second network for the first node for use in enabling the tight aggregation to be established through a target node in the first network and the first node following a handover of the terminal device from the source node to the target node, the information being sent on or during handover of the terminal device from the source node to the target node in the first network.

9. A source node as defined in claim 8, wherein the information comprises information that identifies any one or more of: the terminal device, the source node, the target node, the first node, and the control node.

10. A source node as defined in claim 8 or 9, wherein the information comprises any one or more of:

1 1. A source node as defined in claim 8, 9 or 10, wherein the information is provided in one or more information elements, lEs.

12. A source node as defined in any of claims 8-1 1 , wherein the source node is further adapted to: initiate the handover of the terminal device from the source node to the target node.

13. A source node as defined in any of claims 8-12, wherein the source node is further adapted to:

send information to the target node on or during the handover of the terminal device from the source node to the target node for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

14. A source node as defined in any of claims 8-13, wherein the source node is adapted to send information on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network.

15. A method of operating a target node in a first network that is operating according to a first radio access technology, RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in the first network and a first node in a second network that is operating according to a second RAT, the method comprising: on or during handover of the terminal device from the source node to the target node, receiving information from the first node or a control node in the second network for the first node for use in enabling the tight aggregation to be established through the target node and the first node following the handover; and

establishing the tight aggregation for the terminal device with the first node following a handover of the terminal device from the source node to the target node.

16. A method as claimed in claim 15, wherein the information comprises information that identifies any one or more of: the terminal device, the source node, the target node, the first node and the control node.

17. A method as claimed in claim 15 or 16, wherein the information comprises any one or more of:

18. A method as claimed in claim 15, 16 or 17, wherein the information is provided in one or more information elements, lEs.

19. A method as claimed in any of claims 15-18, wherein the step of establishing the tight aggregation comprises sending a signal to the first node or the control node for the first node to establish the tight aggregation with the first node.

20. A method as claimed in any of claims 15-18, wherein the step of establishing the tight aggregation comprises receiving a signal from the first node or the control node for the first node to establish the tight aggregation with the first node.

21. A method as claimed in any of claims 15-20, wherein the method further comprises the step of:

on or during the handover of the terminal device from the source node to the target node, receiving information from the source node for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

22. A method as claimed in any of claims 15-21 , wherein the step of receiving and/or the step of establishing is performed on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network.

23. A target node for use in a first network that is operating according to a first radio access technology, RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in the first network and a first node in a second network that is operating according to a second RAT, the target node being adapted to:

receive information from the first node or a control node in the second network for the first node for use in enabling the tight aggregation to be established through the target node and the first node following a handover of the terminal device from the source node to the target node, the information being received on or during handover of the terminal device from the source node to the target node; and

establish the tight aggregation for the terminal device with the first node following a handover of the terminal device from the source node to the target node.

24. A target node as claimed in claim 23, wherein the information comprises information that identifies any one or more of: the terminal device, the source node, the target node, the first node and the control node.

25. A target node as claimed in claim 23 or 24, wherein the information comprises any one or more of:

26. A target node as claimed in claim 23, 24 or 25, wherein the information is provided in one or more information elements, lEs.

27. A target node as claimed in any of claims 23-26, wherein the target node is configured to establish the tight aggregation by sending a signal to the first node or the control node for the first node to establish the tight aggregation with the first node.

28. A target node as claimed in any of claims 23-27, wherein the target node is configured to establish the tight aggregation by receiving a signal from the first node or the control node for the first node to establish the tight aggregation with the first node.

29. A target node as claimed in any of claims 23-28, wherein the target node is further configured to:

receive information from the source node on or during the handover of the terminal device from the source node to the target node for use in enabling the tight aggregation to be established through the target node and the first node following the handover.

30. A target node as claimed in any of claims 23-29, wherein the target node is configured to receive and/or establish on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network.

31. A method of operating a first node in a second network that is operating according to a second radio access technology, RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network operating according to a first RAT and the first node, the method comprising:

on or during handover of the terminal device from the source node to a target node in the first network, receiving information from the source node for use in enabling the tight aggregation to be established through the target node and the first node following the handover; and

establishing the tight aggregation for the terminal device with the target node following a handover of the terminal device from the source node to the target node.

32. A method as claimed in claim 31 , wherein the information comprises information that identifies any one or more of: the terminal device, the source node and the target node.

33. A method as claimed in claim 31 or 32, wherein the information comprises any one or more of:

34. A method as claimed in claim 31 , 32 or 33, wherein the information is provided in one or more information elements, lEs.

35. A method as claimed in any of claims 31-34, wherein the step of establishing the tight aggregation comprises sending a signal to the target node to establish the tight aggregation with the target node.

36. A method as claimed in claim 31-34, wherein the step of establishing the tight aggregation comprises receiving a signal from the target node to establish the tight aggregation with the target node.

37. A first node for use in a second network that is operating according to a second radio access technology, RAT, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network operating according to a first RAT and the first node, the first node being adapted to:

receive information from the source node for use in enabling the tight aggregation to be established through a target node in the first network and the first node following a handover of the terminal device from the source node to the target node, the information being received on or during handover of the terminal device from the source node to the target node; and

establish the tight aggregation for the terminal device with the target node following a handover of the terminal device from the source node to the target node.

38. A first node as claimed in claim 37, wherein the information comprises information that identifies any one or more of: the terminal device, the source node and the target node.

39. A first node as claimed in claim 37 or 38, wherein the information comprises any one or more of:

40. A first node as claimed in claim 37, 38 or 39, wherein the information is provided in one or more information elements, lEs.

41. A first node as claimed in any of claims 37-40, wherein the first node is adapted to establish the tight aggregation by sending a signal to the target node to establish the tight aggregation with the target node.

42. A first node as claimed in claim 37-40, wherein the first node is adapted to establish the tight aggregation by receiving a signal from the target node to establish the tight aggregation with the target node.

43. A method of operating a control node in a second network, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network that is operating according to a first radio access technology, RAT, and a first node in the second network that is operating according to a second RAT, wherein the control node is a control node for the first node in the second network, the method comprising:

establishing the tight aggregation for the terminal device with the target node and the first node following the handover.

44. A method as claimed in claim 43, wherein the information comprises information that identifies any one or more of: the terminal device, the source node, the target node and the control node.

45. A method as claimed in claim 43 or 44, wherein the information comprises any one or more of:

46. A method as claimed in claim 43, 44 or 45, wherein the information is provided in one or more information elements, lEs.

47. A method as claimed in any of claims 43-46, wherein the step of establishing the tight aggregation comprises sending a signal to the target node to establish the tight aggregation between the first node and the target node.

48. A method as claimed in any of claims 43-46, wherein the step of establishing the tight aggregation comprises receiving a signal from the target node.

49. A method as claimed in any of claims 43-48, wherein the steps of the method are performed on or during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network, wherein the control node is a control node for the second node.

50. A control node for use in a network, wherein a terminal device has one or more tight aggregation bearers through a source node in a first network that is operating according to a first radio access technology, RAT and a first node in a second network that is operating according to a second RAT, wherein the control node is a control node for the first node in the second network, the control node being adapted to:

establish the tight aggregation for the terminal device with the target node and the first node following a handover of the terminal device from the source node to the target node.

51. A control node as claimed in claim 50, wherein the information comprises information that identifies any one or more of: the terminal device, the source node, the target node and the control node.

52. A control node as claimed in claim 50 or 51 , wherein the information comprises any one or more of:

53. A control node as claimed in claim 50, 51 or 52, wherein the information is provided in one or more information elements, lEs.

54. A control node as claimed in any of claims 50-53, wherein the control node is adapted to establish the tight aggregation by sending a signal to the target node to establish the tight aggregation between the first node and the target node.

55. A control node as claimed in any of claims 50-53, wherein the control node is adapted to establish the tight aggregation by receiving a signal from the target node.

56. A control node as claimed in any of claims 50-55, wherein the control node is adapted to receive and/or establish during handover of the terminal device from the source node to the target node in the first network and handover of the terminal device from the first node to a second node in the second network, wherein the control node is a control node for the second node.

57. A computer program product comprising a computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform the method of any of claims 1-7, 15-22, 31-36 or 43- 49.