WO2011096781A2

WO2011096781A2 - Method for handling mobility of a wireless terminal

Info

Publication number: WO2011096781A2
Application number: PCT/KR2011/000828
Authority: WO
Inventors: Saso Stojanovski; Arnaud Vedrine
Original assignee: Lg Electronics Inc.
Priority date: 2010-02-08
Filing date: 2011-02-08
Publication date: 2011-08-11
Also published as: WO2011096781A3

Abstract

The method deals with mobility of a wireless terminal for communication through a base station, a local gateway and a local area network, the local gateway having an interface with a serving node of a packet core network. In the local gateway, a request to create a session for the wireless terminal is received from the serving node, the request containing an IP address of the wireless terminal in the local area network. The IP address of the wireless terminal as received in the request is advertized on the local area network in association with a medium access control address of the local gateway.

Description

METHOD FOR HANDLING MOBILITY OF A WIRELESS TERMINAL

The present invention relates to telecommunications and more particularly to methods for providing communication of a wireless terminal through a base station, a local gateway and a local area network (LAN).

It is applicable to mobile communications networks as developed in the framework to the 3^rd Generation Partnership Project (3GPP). In particular, 3GPP has a work item referred to as Local IP Access (LIPA) whose purpose is to provide access to home or enterprise IP networks via femtocells. LIPA is generally described in the technical report 3GPP TR 23.829, “LIPA and SIPTO”, version 0.4.0, published in January 2010. The femtocells are served by base stations interfaced with a cellular network infrastructure. The base stations are referred to as HNB ("home node B") in the context of universal mobile telecommunication system (UMTS) networks and as HeNB ("home evolved node B") in the context of evolved packet system (EPS) networks.

Figure 1 illustrates an architecture for Local IP Access to a home or enterprise IP network that is considered in the above-mentioned technical report 3GPP TR 23.829. In figure 1 and the following figures of the present document, reference is made to EPS networks for the cellular part of the architecture. It will be apparent that the discussed features are also usable in UMTS and other systems.

The HeNB 10 is coupled with a local gateway (L-GW) 11 via an unspecified interface which may be proprietary to the manufacturer of equipment including the HeNB 10 and the L-GW 11. Both the HeNB 10 and the L-GW 11 are connected to a LAN 12 forming a home or enterprise network operating with the IP protocol and, for example, with an IEEE 802 standard for the lower layers. A wireless terminal 13 (called user equipment, or UE, in the 3GPP jargon) within range of the HeNB 10 can communicate through the cellular network infrastructure or over the LAN through the local gateway 11.

The LAN 12 is connected to the Internet through an IP backhaul network 14 of an Internet service provider. A home router 15 having a network address translation (NAT) function is used for connection of the LAN 12 to the IP backhaul 14.

The cellular network infrastructure has a core network 16 referred to as EPC ("evolved packet core") in the context of EPS. The EPC has a number of nodes including:

- one or more MME nodes 18 ("mobility management equipment") communicating with base stations (eNB) of the cellular network including HeNBs serving femtocells. The standardized interface between the MME and the eNB is called S1-mme;

- one or more PGW nodes 20 ("PDN gateway"), each PGW connecting the EPC to a packet data network (PDN); and

- one or more SGW nodes 19 ("serving gateway") for the user plane packet traffic. The SGW is interfaced with the PGW 20 through an interface called S5, with the eNB through an interface called S1-U, and with the MME through a control interface called S11. The interfaces S11 with the PGW 20 and S1-U with the HeNB 10 are shown in dashed lines in figure 1 since they are only used for traffic to or from a remote PGW i.e. for non-local traffic.

Communication between the EPC 16 and the IP backhaul 14 is provided through a security gateway (SeGW) 21. The SeGW 21 provides secured tunnels 22 with respective HeNBs 10 connected via the IP backhaul 14. Such a tunnel 22, typically an IPsec tunnel, carries the S1-U and S1-mme interfaces for the user plane and the control plane through the IP backhaul 14 and the LAN 12 to which the respective HeNB is connected.

In the context of LIPA, the L-GW 11 collocated with a HeNB 10 has a subset of packet data network gateway functionalities and can thus be seen as a PDN gateway by the EPC 16. In particular, the L-GW 11 has an S5 interface with the SGW 19. This S5 interface between the L-GW 11 and the SGW 19 is carried by the IPsec tunnel 22 between the SeGW 21 and the local equipment comprising the HeNB 10 and the L-GW 11. As long as the UE 13 remains under coverage of the same original HeNB, all traffic to/from the home or enterprise network is routed directly between the HeNB and the collocated L-GW.

For a given LAN 12, a plurality of HNB/HeNB can be deployed to enlarge wireless coverage. Mobility within the home or enterprise network then becomes an issue. When handing over from one HNB/HeNB to another, it is desirable that all local traffic (i.e. traffic generated in and destined to the home or enterprise network) should be kept inside the local network. Solutions based on "tromboning", i.e. directing incoming or outgoing user packets via the HeNB of a target cell after handover, its IPsec tunnel, the SGW in the EPC, the IPsec tunnel of the HeNB of the source cell with which communication was taking place prior to handover and the L-GW coupled with the latter HeNB, are feasible but do not satisfy this purpose. It results in inefficient use of network resources. Tromboning is not a good solution in the case of an enterprise network in which the fact that subsequent to handover, the user data are forwarded on a path that is outside of the local network may not be acceptable.

Another option for providing mobility within the LAN 12 is to export the SGW function into the customer premises, to be coupled with the L-GW 11. Such an option requires carrier-grade equipment within customer premises, which makes it economically unattractive. It is also problematic for roaming users. In addition, the SGW function should be relocated in the EPC if the UE has no PDN connection to the LAN 12, which may imply frequent SGW relocations.

The requirement to keep local traffic inside the local network can also be approached by defining a stand-alone L-GW function inside the home or corporate network, and a direct interface between HeNB and L-GW (see 3GPP S2-100405, “Extension to Variant 1 of Solution 1 addressing inter-H(e)NB mobility”, January 18-22, 2010, Shenzhen, China). However, this straightforward approach requires specification of a completely new interface whose termination points are located outside of the operator’s network. It also requires a solution for L-GW selection considering that in the stand-alone case, the HeNBs may not know the IP address of the S5 termination at the L-GW and, therefore, cannot assist the MME in L-GW selection. In addition, it may require definition of some new concepts, such as “L-GW Hosting party” (similar to the “HeNB Hosting party”), with its set of credentials for authentication and security purposes.

There is thus a need for a solution to femto mobility in the LIPA context, which keeps the LAN traffic within the LAN while avoiding the definition of a stand-alone L-GW and of a direct HeNB-to-L-GW interface.

A method is proposed for providing communication of a wireless terminal through a base station, a local gateway having an interface with a serving node of a packet core network and a local area network. The method comprises, in the local gateway:

- receiving from the serving node a request to create a session for the wireless terminal, the request containing an IP address of the wireless terminal in the local area network; and

- advertizing the IP address of the wireless terminal on the local area network, in association with a medium access control (MAC) address of the local gateway.

In an embodiment, the request to create a session for the wireless terminal contains a packet data network context including said IP address of the wireless terminal. It may also contain an indication that the IP address of the wireless terminal is to be advertized on the local area network.

The base station typically has an interface with a mobility management node of the packet core network. The method can then include, in the mobility management node:

- receiving from the base station a control plane message related to the wireless terminal; and

- the wireless terminal being previously associated with another base station, transmitting to the serving node the request to create a session containing the IP address of the wireless terminal, thereby causing the serving node to relay the request to the local gateway.

Different types of control plane messages can trigger transmission of the request to create a session in such context. In particular, it can be a handover request acknowledgement message. Alternatively, it can be a message conveying a non-access stratum service request message or a tracking area update request message from the wireless terminal.

In the mobility management node, the method may further comprise transmitting to the serving node a request to delete a previous session with a source gateway coupled with the other base station, through which the wireless terminal was communicating using said IP address. After receiving the request to delete a previous session, the source gateway may forward any packets buffered for the IP address to the advertized MAC address of the local gateway on the local area network.

Alternatively, the forwarding of any packets buffered for the IP address to the advertized MAC address of the local gateway on the local area network may take place in the source gateway after receiving the advertisement of the IP address of the wireless terminal in association with said MAC address.

Another aspect of the invention relates to a gateway suitable for implementing embodiments of the above-mentioned method in a home or enterprise network. This gateway comprises a first interface with a base station, a second interface with a local area network, the gateway having a medium access control address in the local area network, and a third interface with a serving node of a packet core network. The third interface is arranged for receiving from the serving node a request to create a session for the wireless terminal, the request containing an IP address of the wireless terminal in the local area network. The second interface is arranged for advertizing the IP address of the wireless terminal on the local area network, in association with the medium access control address of the gateway.

Still another aspect of the invention relates to a mobility management node for handling mobility of a wireless terminal for communication of the wireless terminal through a target base station, a target local gateway and a local area network in accordance with embodiments of the above-mentioned method. The mobility management node comprises a first interface with the target base station, and a second interface with a serving node of a packet core network, the serving node having an interface with the target local gateway. The first interface is arranged for receiving from the target base station a control plane message related to the wireless terminal. The wireless terminal being previously associated with a source base station coupled with a source local gateway, the second interface is arranged for transmitting to the serving node a request to create a session for communication of the wireless terminal over the local area network through the target base station and the target local gateway. This request to create a session contains an IP address used by the wireless terminal when communicating through the source base station and the source local gateway.

Other features and advantages of the method and devices disclosed herein will become apparent from the following description of non-limiting embodiments, with reference to the appended drawings.

Figure 1, discussed above, is a diagram showing entities involved in an implementation of LIPA in an EPS system.

Figures 2 and 3 are diagrams similar to figure 1 showing a plurality of HeNBs and L-GWs in the LAN, before and after a handover within the local network.

Figure 4 is a diagram showing a call flow usable in a handover procedure in an embodiment of the method disclosed herein.

Figure 5 is a diagram showing a call flow usable in a service request procedure following a change of serving femtocell in another embodiment of the method.

Figures 6 and 7 are block diagrams of customer equipment including a base station and a local gateway and of mobility management equipment of a core network, usable in embodiments of the method.

The architecture shown in figure 2 and 3 is very similar to that of figure 1. A first HeNB 10A is collocated with a first L-GW 11A, while a second HeNB 10B is collocated with a second L-GW 11B. Figures 2 and 3 show the

IPsec tunnels

22A, 22B established between the security gateway 21 and, respectively, the equipment comprising the collocated HeNB 10A and L-GW 11A and the equipment comprising the collocated HeNB 10B and L-GW 11B. Each of these

tunnels

22A, 22B carries the S1-U interface (if any) between the HeNB and the SGW 19, the S5 interface between the L-GW and the SGW 19, and the S1-mme the interface between the HeNB and the MME 18.

In the scenario depicted in figure 2, the UE 13 is in the femtocell served by the HeNB 10A and communicates, through the HeNB 10A and the associated L-GW 11A, with a local server 30 for example (it could also be communication with other terminals within the LAN 12, communication on the Internet provided by the IP backhaul 14, etc.). The UE 13 is moving towards the femtocell served by the HeNB 10B.

In the situation shown in figure 3, the UE 13 has moved to the femto cell served by the HeNB 10B and has lost the radio link with the source HeNB 10A. A handover took place to transfer the communication from the HeNB 10A to the HeNB 10B. As shown in figure 3, the L-GW has been relocated along with the HeNB providing the wireless link.

Such relocation can be performed using a call flow as shown in figure 4. Figure 4 shows downlink (DL) user plane data from the local server 30 reaching the UE 13 through the source L-GW 11A and the source HeNB 10A. In step A1 shown in figure 4, a decision is made in the source HeNB 10A that a handover is needed. A Handover Required message is then sent in step A2 to the MME 18 via the S1-mme interface through the IPsec tunnel 22A. The usual handover procedure is then performed. The MME 18 sends a Handover Request message (A3) to the target HeNB 10B. If the target HeNB 10B has resources to communicate with the UE 13, it returns a Handover Request Acknowledgment message (A4) the MME 18.

Upon receipt of the Handover Request Acknowledgment message instep A4, the MME 18 launches two actions shown in

boxes

40, 50 in figure 4.

The first action 40 consists in deleting the session that the source L-GW 11A had with the UE 13. To do this, the MME 18 sends to the SGW 19, through the S11 interface, a Delete Session Request to the source L-GW 11A (A5). The Delete Session Request is relayed by the SGW 19 to the source L-GW 11A in step A6 over the S5 interface through the IPsec tunnel 22A. In response, the source L-GW 11A deletes the existing session with the UE 13 and returns a Delete Session Response message to the SGW 19 (A7). The Delete Session Response is forwarded by the SGW 19 to the MME 18 (A8).

To carry out the action 50, the MME 18 prepares a Create Session Request message and sends it to the SGW 19 over the S11 interface (A9). The Create Session Request contains a PDN context which includes the IP address of the UE 13 on the LAN 12. The Create Session Request message 10 is relayed by the SGW 19 to the target L-GW 11B over the S5 interface through the IPsec tunnel 22B. In response, the target L-GW 11B advertizes on the LAN 12 the IP address of the UE 13 as received in the Create Session Request message, in association with the MAC address of the target L-GW 11B on the LAN 12.

The advertizing of the UE's IP address in association with the target L-GW's MAC address is performed in step A10a using ARP announcement (a.k.a. "gratuitous ARP") if the LAN 12 uses IPv4. The IPv4 Address Resolution Protocol (ARP) is described in the Request For Comments (RFC) 4389 published in April 2006 by the Internet Engineering Task Force (IETF). If IPv6 is used in the LAN 12, the advertizing of the UE's IP address in association with the target L-GW's MAC address is performed via unsolicited neighbor advertisement as described in RFC 4861 published in September 2007 by the IETF. The advertizing consists in announcing to all stations connected to the LAN 12 that traffic intended for the station having the advertized IP address should be directed to the associated MAC address.

After the advertizing step A10a, the target L-GW 11B returns the Create Session Response message over the S5 interface to the SGW 19 (A11). The Create Session Response message is relayed (A12) by the SGW 19 to the MME 18 to complete the action 50.

The two

actions

40, 50 can be carried out in the order shown in figure 4, in the reverse order, or in parallel. After their completion, a Handover Command message is sent by the MME to the source HeNB 10A (A13), which relays it to the UE 13 (A14). At this point, in accordance with the usual handover procedure, the UE 13 synchronizes to the new cell served by the target HeNB 10B and detaches from the old cell served by the source HeNB 10A. The Handover Confirm message can then be sent by the UE 13 to the target HeNB 10B (A15). From this moment, uplink and downlink user plane data can be exchanged by the UE through the target HeNB 10B and the associated L-GW 11B, as shown by the dashed lines in the lower part of figure 4. The last messages A16-A20 shown in figure 4 are for completing the handover procedure. After confirmation of the handover from the UE, the target HeNB 10B sends a Handover Notify message to the MME 18 (A16) which can then send the Modify Bearer Request message to the SGW 19 (A17). The SGW 19 returns the Modify Bearer Response message (A18). Finally, the MME 18 sends a UE Context Release Command message (A19) to the source HeNB 10A which returns the UE Context Release Complete message (A20).

In the action 40, as part of the handover procedure, the MME 18 deletes the PDN connection or session in the source L-GW 11A. In the action 50, as part of the handover procedure, the MME 18 re-creates the PDN connection or session in the target L-GW 11B. This can be done if the PDN context information required for recreation of the same PDN session with the target L-GW 11B, in particular the IP address assigned to the UE 13 in the LAN 12, was previously stored in the MME 18. The IP address of the UE may be known by the MME from the UE Requested PDN Connectivity procedure carried out when the UE first established its PDN connection with the local network. Alternatively, a procedure can be used to inform the MME 18 of the relevant IP address, for example a Bearer Modification procedure as specified in sections 5.4.3 of the technical specification 3GPP TS 23.401, version 9.3.0, published in December 2009 by the 3GPP. Such a procedure can be used, in particular, to update the MME 18 whenever the UE's IP address is changed using DHCP (Dynamic Host Configuration Protocol).

The advertisement of the IP address of the UE 13 in association with the MAC address of the target L-GW 11B can be performed spontaneously by the target L-GW 11B upon receipt of the Create Session Request message containing a UE's IP address. Alternatively, the Create Session Request message from the MME/SGW may include an indication or command to perform IP address advertisement for the indicated IP address. In this case, the advertisement is performed by the target L-GW 11B only when the indication is provided.

The call flow of figure 4 shows how mobility can be handled within the LAN 12 when the UE is in active mode. The method is also applicable to idle mode mobility which can be handled by modifying the service request procedure as illustrated in figure 5. It is assumed here that the source and target

HeNBs

10A, 10B belong to the same tracking area. If this is not the case, then idle mode mobility is handled via a similar modification of the tracking area update procedure.

The service request procedure shown in figure 5 can be triggered:

- either when the UE 13 has new uplink data to transmit through the LAN 12 after it moved and changed cells in idle mode. It then selects the target HeNB 10B and transmits non-access stratum (NAS) signaling containing a Service Request message;

- or as a response to paging, i.e. downlink packets were arriving for the UE which triggered a paging procedure in all cells belonging to the same tracking area. When the UE 13 receives the paging message, it returns NAS signaling containing a Service Request message to its new cell site, i.e. to the target HeNB 10B.

In response to the NAS Service Request message from the UE 13 (B1), the target HeNB 10B conveys the request to the MME 18 via the S1-mme interface through the IPsec tunnel 22B (B2). After receipt of this NAS Service Request message, the MME 50 performs

actions

50, 40 similar to those described above with reference to figure 4. Before that, the MME 18 may trigger the authentication and security procedures (B3) between the UE 13 and the Home Subscriber Server (HSS) 25 belonging to the operator's core network. Once the UE is authenticated, the MME 18 launches the action 50 as described above by sending the Create Session Request message to the SGW 19 (B4) which forwards it to the target L-GW 11B (B5). Upon receipt of that Create Session Request, the target L-GW 11B returns a Create Session Response message (B6) and advertizes the UE's IP address in association with its own MAC address on the LAN 12. The action 50 is completed by the SGW 19 returning the Create Session Request message to the MME 18 (B7).

The delete action 40 is also similar to that described with reference to figure 4. The MME 18 sends a Delete Session Request message (B11) to the SGW 19 which forwards it to the source L-GW 11A over the S5 interface (B12). The L-GW 11A deletes its PDN context with the UE and returns a Delete Session Response message (B13) to the SGW 19. The Delete Session Response message is relayed to the MME 18 over the S11 interface (B14).

In parallel, the MME 18 carries on with the service request procedure by sending an Initial Context Setup Request message (B8) over the S1-mme interface to the target HeNB 10B. In response, the target HeNB 10B establishes a radio bearer with the UE 13 (B9). At this point, the UE 13 can start transmitting uplink data to the LAN 12 through the target HeNB 10 B and the target L-GW 11B, and receiving downlink data in the other direction. An Initial Context Setup Complete message is returned by the target HeNB 10B to the MME 18 to complete the service request procedure (B10).

In the scenario of figure 5, it can happen, particularly when the service request procedure is launched after paging, that the source L-GW 10A has some buffered IP packets intended for the UE 13, which packets could not be sent due to loss of the radio link between the source HeNB 10A and the UE 13. The source L-GW 11A is configured to forward these buffered packets in step B13a shown in figure 5, i.e. in response to reception of the Delete Session Request message from the SGW 19. These packets are forwarded over the LAN 12 using the MAC address of the target L-GW 11B which was broadcasted with the advertizing message in step B6a. Alternatively, the source L-GW 11A may forward the buffered packets in response to reception of the advertizing message from the target L-GW 11B in step B6a.

The idle mode mobility call flow illustrated in figure 5 is easily adapted in the case of the tracking area update procedure. In this case, the NAS signaling to which the MME responds by calling the create session request procedure does not correspond to a Service Request message, but to a Tracking Area Update Request message.

A block diagram of customer equipment 60 including a base station (HeNB) 10 and a collocated gateway (L-GW) 11B is shown in figure 6. The HeNB 10 may be of a standard type, with an internal interface with the L-GW 11. The L-GW 11 has a controller 65 and three interfaces:

- a first interface 61 with the HeNB 10;

- a second interface 62 with the LAN 12, for example using Ethernet technology; and

- a third interface 63 with the EPC (SGW 19).

These components 60-63 are shown as separate units in figure 6. It will be appreciated, however, that part of their functions, in particular those related to signaling as illustrated in figures 4-5, can be implemented using software run by a common processing unit.

The interface 63 handles the PGW endpoint of the S5 control plane, in particular reception of the Create Session Request and Delete Session Request messages and transmission of the Create Session Response and Delete Session Response messages to the SGW 19. When a Create Session Request contains an IP address of a UE (and possibly an indication that this IP address is to be advertized on the LAN 12), the interface 63 provides the IP address to the controller 65 which then controls the LAN interface 62 to cause it to broadcast an advertizing message on the LAN 12 using proxy ARP (IPv4) or proxy neighbor discovery (IPv6). The advertizing message associates the IP address as received with the MAC address of the L-GW 11B which is stored in the interface 62. As discussed with reference to figure 5, the LAN interface 62 may further have a buffer for containing downlink packets from the LAN 12 which could not be delivered to a UE. Such packets are eventually delivered, via the LAN interface 62 instead of the HeNB interface 61, after receipt of an advertizing message from another L-GW concerning the UE's IP address or in response to a command from the controller 65 after receipt of a Delete Session Request message on the interface 63.

A block diagram of an MME is shown in figure 7. It has a controller 70 and a number of network interfaces including a first interface 71 with eNBs and a second interface 72 with the SGW 19. In the context of LIPA, the first interface 71 provides communication with HeNBs, including the target HeNB 10B, as an S1-mme endpoint. The second interface 72 supports the logical S-11 interface with the serving gateway 19.

In the mobility management call flow illustrated in figures 4 and 5, the first interface 71 of the MME 18 receives a control plane message from the target HeNB 10B, namely a Handover Request Acknowledgment message of the S1-AP protocol (S1 Application Part) in the handover procedure (A4) and NAS signaling conveying either a Service Request message from the UE in the service request procedure (B2) or a Tracking Area Update Request message from the UE in the tracking area update procedure.

The control plane message is reported to the controller 70 which checks a user context for the UE 13 in a context database 73 provided in the MME 18. If the controller 70 detects that the control plane message comes from a HeNB which is not the one with which the UE was previously communicating, it controls the second interface 72 to generate the Create Session Request message of the GTP C protocol (GPRS Tunnelling Protocol for the control plane). The controller 70 puts in this Create Session Request message (A9 or B4) the current PDN context for the UE 13, including its current IP address in the LAN 12, retrieved from the user context database 73. It may also insert an indication for the target L-GW that the UE's IP address should be advertised on the LAN 12 together with its own MAC address. The Create Session Request message is sent by the second interface 72 to the SGW 19 which relays it to the target LGW 11 B through the S5 interface which also supports GTP C.

The above-described LIPA architecture handling inter-HeNB mobility via L-GW relocation using IP address advertisement on the LAN 12 provides substantial benefits. In particular, it keeps the local traffic inside the LAN 12 while avoiding the complexity associated with the definition of a standardized HeNB-to-L-GW interface. It is noted that the solution is well-suited to roaming users, for whom the serving gateway need not be located in the home network. In the 3GPP context, the solution is suitable both for EPS and UMTS types of network.

While a detailed description of exemplary embodiments of the invention has been given above, various alternatives, modifications, and equivalents will be apparent to those skilled in the art. Therefore the above description should not be taken as limiting the scope of the invention which is defined by the appended claims.

Claims

A method for providing communication of a wireless terminal through a base station, a local gateway and a local area network, wherein the local gateway has an interface with a serving node of a packet core network, the method comprising, in the local gateway:

- receiving from the serving node a request to create a session for the wireless terminal, the request containing an IP address of the wireless terminal in the local area network; and

- advertizing the IP address of the wireless terminal on the local area network, in association with a medium access control address of the local gateway.
The method of claim 1, wherein the request to create a session for the wireless terminal contains a packet data network context including said IP address of the wireless terminal.
The method of claim 1, wherein the request to create a session for the wireless terminal contains an indication that the IP address of the wireless terminal is to be advertized on the local area network.
The method of claim 1, wherein the base station has an interface with a mobility management node of the packet core network, the method further comprising, in the mobility management node:

- receiving from the base station a control plane message related to the wireless terminal; and

- the wireless terminal being previously associated with another base station, transmitting to the serving node the request to create a session containing the IP address of the wireless terminal, thereby causing the serving node to relay said request to the local gateway.
The method of claim 4, wherein said control plane message is a handover request acknowledgement message.
The method of claim 4, wherein said control plane message conveys a non-access stratum service request message or a tracking area update request message from the wireless terminal.
The method of claim 4, further comprising, in the mobility management node:

- transmitting to the serving node a request to delete a previous session with a source gateway coupled with said other base station, through which the wireless terminal was communicating using said IP address.
The method of claim 7, further comprising, in said source gateway:

- after receiving the request to delete a previous session, forwarding any packets buffered for said IP address to said medium access control address on the local area network.
The method of claim 1, further comprising, in a source gateway connected to the local area network and through which the wireless terminal was previously communicating:

- after receiving the advertisement of the IP address of the wireless terminal in association with said medium access control address, forwarding any packets buffered for said IP address to said medium access control address on the local area network.
A gateway, comprising:

- a first interface with a base station;

- a second interface with a local area network, the gateway having a medium access control address in the local area network; and

- a third interface with a serving node of a packet core network,

wherein the third interface is arranged for receiving from the serving node a request to create a session for the wireless terminal, the request containing an IP address of the wireless terminal in the local area network,

and wherein the second interface is arranged for advertizing the IP address of the wireless terminal on the local area network, in association with the medium access control address of said gateway.
The gateway of claim 10, wherein the request to create a session for the wireless terminal contains a packet data network context including said IP address of the wireless terminal.
The gateway of claim 10, wherein the request to create a session for the wireless terminal contains an indication that the IP address of the wireless terminal is to be advertized on the local area network.
A mobility management node for handling mobility of a wireless terminal for communication of the wireless terminal through a target base station, a target local gateway and a local area network, the mobility management node comprising:

- a first interface with the target base station; and

- a second interface with a serving node of a packet core network, the serving node having an interface with the target local gateway,

wherein the first interface is arranged for receiving from the target base station a control plane message related to the wireless terminal,

wherein, the wireless terminal being previously associated with a source base station coupled with a source local gateway, the second interface is arranged for transmitting to the serving node a request to create a session for communication of the wireless terminal over the local area network through the target base station and the target local gateway,

and wherein said request to create a session contains an IP address used by the wireless terminal when communicating through the source base station and the source local gateway.
The mobility management node of claim 13, wherein the request to create a session for the wireless terminal contains a packet data network context including said IP address of the wireless terminal.
The mobility management node of claim 13, wherein the request to create a session for the wireless terminal contains an indication that the IP address of the wireless terminal is to be advertized on the local area network.
The mobility management node of claim 13, wherein the control plane message from the target base station is a handover request acknowledgement message.
The mobility management node of claim 13, wherein the control plane message from the target base station conveys a non-access stratum service request or tracking area update message from the wireless terminal.
The mobility management node of claim 13, wherein the second interface is arranged for transmitting to the serving node a request to delete a previous session with the source local gateway.