WO2014079514A1 - Handling of serving gateway failure - Google Patents

Abstract

There is provided management of serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active. An indication of an SGW failure is acquired by a master ISR associated mobility management node, MMN. The SGW is associated with a number of user equipment, UE, with ISR active. A notification message is provided to a slave ISR associated MMN, that the master ISR associated MMN is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW. SGW relocation and re-establishment of the ISR association is performed such that the PDN connection is relocated to the selected new SGW.

Description

HANDLING OF SERVING GATEWAY FAILURE

TECHNICAL FIELD

Embodiments presented herein relate to managing serving gateway, SGW, failure, and particularly to managing SGW failure when idle mode signalling reduction, ISR, is active.

BACKGROUND

In wireless communication networks, there is always a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the wireless

communication network is deployed.

In a wireless communications network wireless radio terminals communicate via a Radio Access Network (RAN) to one or more core networks. The radio terminals may e.g. be a mobile station (MS) or a user equipment unit (UE) or similar, e.g. such as mobile telephones also known as "cellular" telephones, and laptops with wireless capability, and thus can be, for example, portable, pocket, hand-held, computer-comprised, or car-mounted mobile devices which communicate voice and/or data with radio access network.

A wireless network, illustratively a Long Term Evolution (LTE)

communications network, may comprise groups of mobile telephones or other user equipment (UE) communicating with one or more eNodeBs, which communicate with one or more Serving Gateways (SGWs), which

communicate with a Packet Data Network (PDN) Gateway (PGW), which communicates with fixed networks such as IP Multimedia Subsystem (IMS) access networks or core networks. Additionally, the LTE network includes various network elements such as Mobility Management Entities (MMEs), a Policy and Charging Rules Function (PCRF), a network management system (NMS) and so on.

For example, the General Packet Radio Service (GPRS) is a wireless communication system, which evolved from the GSM. The GSM EDGE Radio Access Network (GERAN) is a radio access network for enabling radio terminals to communicate with one or more core networks. A UE or a MS may interact with GPRS using the GERAN radio access and the UTRAN radio access. The UE-related and/or MS-related control signaling is handled by the Serving GPRS Support Node (SGSN) with support of subscription

information provided by the Home Subscriber Server (HSS).

In a failure scenario where a Serving Gateway (SGW) loses connectivity with other nodes in the network (e.g., due to network disconnection, power failure, or even a triggered behavior based on partial failures), a backup SGW should take over operations. This should be accomplished in an intelligent manner to avoid unreasonable spiking in resource utilization while continuing to meet reasonable user/subscriber expectations.

According to 3GPP TR 23.857 Vi.10.1 (October, 2012), Section 6.5 the Idle Mode Signaling Reduction (ISR) function provides a mechanism to limit signaling during the inter RAT cell reselection for the idle mode UE, which is specified in 3GPP TS 23.401. If the ISR is activated, the MME maintains the SGSN control plane IP address and TEID, the SGSN maintains the MME control plane IP address and TEID, and the SGW maintains control plane IP addresses and TEIDs of the MME and the SGSN. As outlined in 3GPP TR 23.857 Vi.10.1 section 6.5.3.1, the UEs shall connect to another SGW when the old SGW fails. Active UEs will detect the SGW failure, send a Service Request and the MME will select another SGW for the active UEs. For idle UEs, it requires that both ISR associated nodes, i.e., the MME and the SGSN, page the idle UEs. Paging all idle UEs leads to

substantial signaling over the air and as well as Si-MME and Iu/Gb

interfaces, which may lead to eNB/RNC/BSC/MME/SGSN overload. Si- MME is an interface between an eNodeB and the MME serving the eNodeB. Iu is an interface between the RNC and SGSN, whereas Gb is an interface between a BSC and SGSN. Thus, the Iu/Gb interfaces are interfaces between a radio access network (RAN) and a core network, i.e. one or more core network nodes, e.g. such as a SGSN. In addition to that, new S3 signaling are also proposed by solution 1 in 3GPP TR 23.857 Vi.10.1 section 6.5.3.1 to be introduced in order to reduce (or at least try to reduce) the paging, which also brings further signaling impact on the S3 interface and complexities on the implementation of MME/SGSN. The S3 is an interface between an MME and an SGSN. Further, since the UEs are ISR activated and in the idle mode (that is, the UE may camp on either 2G/3G or LTE) this makes paging inefficient.

One issue related to solution 1 in 3GPP TR 23.857 Vi.10.1 section 6.5.3.1 is how to handle the UE in the idle mode. The following short example is included for illustrative purposes. Assume that the failed SGW has 1,000,000 UEs associated therewith before it fails. Thus, 1,000,000 UEs are affected by the SGW failure. Assume further that 50% of the UE are in active mode (for both 2G/3G and LTE). Assume further that the UEs are equally distributed between LTE and 2G/3G (i.e., 50% having LTE radio access and 50% having 2G/3G radio access). For the ISR active case and solution 1 as specified in 3GPP TR 23.857 Vi.10.1 section 6.5.3.1 this would imply the following.

A. Firstly, since the MME would have 25% of 1,000,000 UEs in Active mode, it would need to page the rest (i.e., 750,000) of the UEs. The same applies for the SGSN. This would require 1,500,000 network paging signaling resources. B. Secondly, the Active UEs using one radio access technology appear as Idle for the other radio access technologies. The MME or SGSN therefore needs to inform their ISR associated node that it holds 25% active UEs, in order for the ISR associated node to not page those UEs which are active mode in the other radio access technology scheme. This would additionally require 250,000 x 2 =500, 000 S3 signaling resources.

C. Thirdly, once the UEs which were in idle mode (according to the present example 250,000 UEs for each radio access technology) answer the paging, the MME or SGSN needs to inform the other ISR associated node to stop the paging. This would additionally require 250,000 x 2 =500, 000 S3 signaling resources. Hence, there is still a need for an improved handling of SGW failure. SUMMARY

An object of embodiments herein is to provide improved handling of SGW failure. The inventors of the enclosed embodiments have realized that the S3 signaling resources required for item B above, although aimed for reducing the paging message for those UEs which are in Active mode in the other radio access, may be useless. The reason is that if the paging messages for the Idle UEs are sent immediately after the detection of the SGW failure, those UEs which are in Active mode in the other radio access technology schemes may already been paged. Delaying paging the UEs in Idle mode, waiting for a certain time so as to receive all the S3 signaling (to inform the ISR associated node that each UE is active in the other radio access technology scheme) could remove the need for 500, 000 Paging signaling resources. However, determining how long the MME/SGSN should wait may be a complicated process since MME and SGSN have difference signaling capacity.

The inventors of the enclosed embodiments have further realized that the S3 signaling resources required for item C above need not to be implemented for solution 1 as the MME and the SGSN perform paging independently (perhaps with different paging sequence; e.g. one UE may be scheduled to be paged at the 1000th page message in the MME, but the same UE may be paged already at the 10th page in the SGSN if the UE is camping on LTE side). This would make the transmission from the MME of an ISR deactivation notification to the SGSN useless, since the SGSN would already have performed several paging operations and determined that the UE in question is in the MME. Therefore the S3 signaling resources required for item C above may be of limited use.

The inventors of the enclosed embodiments have therefore concluded that solution 1 in 3GPP TR 23.857 Vi.10.1 section 6.5.3.1 for SGW failure may cause signaling overload on the interface between the RAN and the core network ( such as the Iu and/or Gb interface), as well as on the Si-MME interface and the S3 interface. Such signaling overload may in turn cause further node failure.

A particular object is therefore to provide improved management of SGW failure whilst avoiding signaling overload.

According to a first aspect there is presented a method for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active. The method is performed by a master ISR associated mobility management node, MMN. The method comprises acquiring an indication of an SGW failure, the SGW being associated with a number of user equipment, UE, with ISR active. The method comprises providing a notification message to a slave ISR associated MMN, that the master ISR associated MMN is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW. The method comprises performing SGW relocation and re-establishment of the ISR association such that the PDN connection is relocated to the selected new SGW.

According to a second aspect there is presented a method for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active. The method is performed by a slave ISR associated mobility management node, MMN. The method comprises receiving a notification message. The notification message is based on an indication of an SGW failure, the SGW being associated with a number of user equipment, UE, with ISR active. The notification message notifies that a master ISR associated MMN is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW and re-establish the ISR association such that the PDN connection is relocated to the selected new SGW.

According to a third aspect there is presented a method for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active. The method is performed by a serving gateway, SGW. The method comprises receiving a request message from a master ISR associated mobility

management node, MMN. The request message pertains to a session to be created by the SGW. The session relates to setup of a new communication path to a number of UEs with ISR active and affected by the SGW failure. The request message is based on an indication of an SGW failure of a first SGW having been acquired by the master ISR associated MMN, the first SGW being associated with said number of user equipment. The method comprises creating the session. The method comprises transmitting a response message to the master ISR associated MMN. The response message pertains to the session having been created by the SGW.

Advantageously those UEs in the idle mode will be kept in idle mode with ISR re-established, without involving in a NAS procedure such as Service

Request, TAU/RAU and without requiring an additional paging procedure.

According to a fourth aspect there is presented a master idle mode signalling reduction, ISR, associated mobility management node, MMN, for managing server gateway, SGW, failure when idle mode signalling reduction, ISR, is active. The master ISR associated MMN comprises an input/output, I/O, interface arranged to acquire an indication of an SGW failure. The SGW is associated with a number of user equipment, UE, with ISR active. The I/O interface is further arranged to providing a notification message to a slave ISR associated MMN, that the master ISR associated MMN is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW. The master ISR associated MMN comprises a processing unit arranged to perform SGW relocation and re- establishment of the ISR association such that the PDN connection is relocated to the selected new SGW.

According to an embodiment the master ISR associated MMN is part of a mobile management entity, MME, or a serving GPRS support node, SGSN.

According to a fifth aspect there is presented a slave idle mode signalling reduction, ISR, associated mobility management node, MMN, for managing server gateway, SGW, failure when idle mode signalling reduction, ISR, is active. The slave ISR associated MMN comprises an input/output, I/O, interface arranged to receive a notification message. The notification message is based on an indication of an SGW failure. The SGW is associated with a number of user equipment, UE, with ISR active. The notification message notifies that the master ISR associated MMN is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW and re-establish the ISR association such that the PDN connection is relocated to the selected new SGW. According to an embodiment the slave ISR associated MMN is part of a mobile management entity, MME, or a serving GPRS support node, SGSN.

According to a sixth aspect there is presented a serving gateway, SGW, for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active. The SGW comprises an input/output, I/O, interface arranged to receive a request message from a master ISR associated mobility management node, MMN. The request message pertains to a session to be created by the SGW. The session relates to setup of a new communication path to a number of UEs with ISR active and affected by the SGW failure. The request message is based on an indication of an SGW failure of a first SGW having been acquired by the master ISR associated MMN, the first SGW being associated with said number of user equipment. The SGW comprises a processing unit arranged to create the session. The I/O interface is further arranged to transmit a response message to the master ISR associated MMN, the response message pertaining to the session having been created by the SGW.

According to a seventh aspect there is presented a system for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active. The system comprises a master ISR associated MMN according to the fourth aspect. The system further comprises a slave ISR associated MMN according to the fifth aspect. The system further comprises an SGW

according to the sixth aspect. According to an embodiment, in case the master ISR associated MMN is part of an MME the slave ISR associated MMN is part of an SGSN. According to an embodiment, in case the master ISR associated MMN is part of an SGSN the slave ISR associated MMN is part of an MME. According to an eight aspect there is presented a computer program for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the computer program comprising computer program code which, when run on a master idle mode signalling reduction, ISR, associated mobility management node, MMN, causes the master ISR associated MMN to perform a method according to the first aspect.

According to a ninth aspect there is presented a computer program for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the computer program comprising computer program code which, when run on a slave idle mode signalling reduction, ISR, associated mobility management node, MMN, causes the slave ISR associated MMN to perform a method according to the second aspect.

According to a tenth aspect there is presented a computer program for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the computer program comprising computer program code which, when run on an SGW, causes the SGW to perform a method according to the third aspect.

According to an eleventh aspect there is presented a computer program product comprising a computer program according to at least one of the eighth, ninth or tenth aspect and a computer readable means on which the computer program is stored.

It is to be noted that any feature of the first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth and eleventh aspects may be applied to any other aspect, wherever appropriate. Likewise, any advantage of the first aspect may equally apply to the third, fourth, fifth, sixth, seventh, eight, ninth, tenth and/or eleventh aspect, respectively, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is now described, by way of example, with reference to the accompanying drawings, in which:

Figure l is a schematic illustration of an exemplifying LTE architecture for 3GPP accesses within an Evolved Packet System (EPS),

Figure 2 is a schematic illustration of an exemplifying GPRS architecture based on S4 interface;

Figure 3 is another schematic illustration of an exemplifying LTE

architecture, Figure 4 is another schematic illustration of an exemplifying GPRS

architecture;

Figure 5 is a schematic diagram showing functional modules of a master idle mode signalling reduction, ISR, associated mobility management node, MMN; Figure 6 is a schematic diagram showing functional modules of a slave idle mode signalling reduction, ISR, associated mobility management node, MMN; Figure 7 is a schematic diagram showing functional modules of a serving gateway;

Figure 8 shows one example of a computer program product comprising computer readable means; Figures 9 to 14 are flowcharts of methods according to embodiments; and

Figure 15 is a sequence diagram according to embodiments.

DETAILED DESCRIPTION

The inventive concepts will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of are shown. The inventive concepts may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concepts to those skilled in the art. Like numbers refer to like elements throughout the description.

Figure 1 shows a schematic overview of an exemplifying wireless

communication system 1. The wireless communication system 1 is a so called LTE based system. It should be pointed out that the terms "LTE" and "LTE based" system is here used to comprise both present and future LTE based systems, such as, for example, advanced LTE systems. It should be appreciated that although Figure 1 shows a wireless communication system 1 in the form of a LTE based system, the example embodiments herein may also be utilized in connection with other wireless communication systems comprising nodes and functions that correspond to the nodes and functions of the system in Figure 1.

Figure 2 shows a schematic overview of another exemplifying wireless communication system 2. The wireless communication system 2 is an exemplifying GPRS architecture. Figure 3 shows another schematic illustration of an exemplifying LTE architecture. As can be seen, the wireless communication system 3 comprises a base station in the form of an eNodeB, operatively connected to a Serving Gateway (SGW), in turn operatively connected to a Mobility Management Entity (MME) and a PDN Gateway (PGW), which in turn is operatively connected to a Policy and Charging Rules Function (PCRF).

The eNodeB is a radio access node that interfaces with a radio terminal, which is denoted User Equipment (UE) in LTE. The eNodeBs of the system forms the radio access network E-UTRAN for LTE. The SGW routes and forwards user data packets, whilst also acting as the mobility anchor for the user plane during inter-eNB handovers and as the anchor for mobility between LTE and other 3GPP technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and PDN GW). For idle state UEs, the SGW terminates the DL data path and triggers paging when DL data arrives for the UE. It manages and stores UE contexts, e.g. parameters of the IP bearer service, network internal routing information. It also performs replication of the user traffic in case of lawful interception.

The MME is responsible for idle mode UE tracking and paging procedure including retransmissions. It is involved in the bearer activation/deactivation process and is also responsible for choosing the SGW for a UE at the initial attach and at time of intra- LTE handover involving Core Network (CN) node relocation. It is responsible for authenticating the user (by interacting with the HSS). The Non-Access Stratum (NAS) signaling terminates at the MME and it is also responsible for generation and allocation of temporary identities to UEs. It checks the authorization of the UE to camp on the service provider's Public Land Mobile Network (PLMN) and enforces UE roaming restrictions. The MME is the termination point in the network for

ciphering/integrity protection for NAS signaling and handles the security key management. Lawful interception of signaling is also supported by the MME. The MME also provides the control plane function for mobility between LTE and 2G/3G access networks with the S3 interface terminating at the MME from the SGSN. The MME also terminates the S6a interface towards the home HSS for roaming UEs

The PGW provides connectivity to the UE to external packet data networks 250 by being the point of exit and entry of traffic for the UE. A UE may have simultaneous connectivity with more than one PGW for accessing multiple PDNs. The PGW performs policy enforcement, packet filtering for each user, charging support, lawful Interception and packet screening. Another key role of the PGW is to act as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3 GPP 2 (CDMA lX and EvDO). The PCRF determines policy rules in real-time with respect to the radio terminals of the system. This may e.g. include aggregating information in real-time to and from the core network and operational support systems etc of the system so as to support the creation of rules and/or automatically making policy decisions for user radio terminals currently active in the system based on such rules or similar. The PCRF provides the PGW with such rules and/or policies or similar to be used by the acting PGW as a Policy and Charging Enforcement Function (PCEF).

Figure 4 shows another schematic illustration of an exemplifying GPRS architecture. As can be seen, the wireless communication system 4 comprises a Gateway GPRS Support Node (GGSN) connected to a first Serving GPRS Support Node (SGSN) and a second SGSN. In turn, the first SGSN is connected to a Radio Network Controller (RNC) that is operatively connected to a base station in the form of a NodeB, whereas the second SGSN is operatively connected to a Base Station Controller (BSC) that is connected to a base station in the form of a Base Transceiver Station (BTS).

The GGSN is responsible for the interworking between the GPRS network and external packet data networks 250, like the Internet and X.25 networks. The GGSN is the anchor point that enables the mobility of the user terminal in the GPRS/UMTS networks and it may be seen as the GPRS equivalent to the Home Agent in Mobile IP. It maintains routing necessary to tunnel the Protocol Data Units (PDUs) to the SGSN that services a particular Mobile Station (MS). The GGSN converts the GPRS packets coming from the SGSN into the appropriate packet data protocol (PDP) format (e.g., IP or X.25) and sends them out on the corresponding packet data network. In the other direction, PDP addresses of incoming data packets are converted to the GSM address of the destination user. The readdressed packets are sent to the responsible SGSN. The GGSN is responsible for IP address assignment and is the default router for the connected user equipment (UE). The GGSN also performs authentication and charging functions. Other functions include subscriber screening, IP Pool management and address mapping, QoS and PDP context enforcement.

The SGSN is responsible for the delivery of data packets from and to the radio terminals such as mobile stations within its geographical service area. Its tasks include packet routing and transfer, mobility management

(attach/detach and location management), logical link management, and authentication and charging functions. The location register of the SGSN stores location information (e.g., current cell, current Visitor Location Register (VLR)) and user profiles (e.g., International Mobile Station Identity (IMSI), address(es) used in the packet data network) of all GPRS users registered with this SGSN.

The RNC is a node in the UMTS radio access network (UTRAN) and is responsible for controlling the NodeBs that are operatively connected to it. The RNC carries out radio resource management, some of the mobility management functions and is the point where encryption is done before user data is sent to and from the mobile. The RNC is operatively connected to a Circuit Switched Core Network through Media Gateway (MGW) and to the SGSN in the Packet Switched Core Network.

The BSC is a node in the GSM Radio Access Network (GERAN) and is responsible for controlling the BTSs that are connected to it. The BSC carries out radio resource management and some of the mobility management functions. As can be seen in Figures 3 and 4, there are radio terminals such as UEs and/or MSs that communicate with the eNodeB and/or the RNC via a NodeB and/or the BSC via a BTS using an air interface such as LTE-Uu, Um and Gb interface respectively. This makes it possible for the radio terminals to access resources provided by the core network of the systems respectively. A skilled person having the benefit of this disclosure realizes that vast number of well known radio terminals can be used in the various embodiments of the present disclosure. The radio terminal may e.g. be a cell phone device or similar, e.g. such as a Mobile Station (MS) or a User Equipment (UE) or similar, e.g. defined by the standards provided by the 3GPP. Thus, the radio terminal needs no detailed description as such. However, it should be emphasized that the mobile radio terminals may be embedded (e.g. as a card or a circuit arrangement or similar) in and/ or attached to various other devices, e.g. such as various laptop computers or tablets or similar or other mobile consumer electronics or similar, or vehicles or boats or air planes or other movable devices, e.g. intended for transport purposes. Indeed, the radio terminal may even be embedded in and/or attached to various semi- stationary devices, e.g. domestic appliances or similar, or consumer electronics such as printers or similar having a semi-stationary mobility character.

The embodiments disclosed herein relate to management of serving gateway (SGW) failure with Idle Mode Signaling Reduction (ISR) active. The disclosed embodiments do not require support to PGW triggered SGW restoration, neither do the disclosed embodiments require paging to Idle UEs; the disclosed embodiments are entirely based on network signaling.

Idle Mode Signaling Reduction (ISR) is a mechanism that allows the UE to remain simultaneous registered in an UTRAN/GERAN Routing Area (RA) and an E-UTRAN Tracking Area (TA) list. ISR thus allows the UE to roam between LTE and 2G/3G. ISR allows the UE to make cell reselections between E-UTRAN and UTRAN/GERAN without a need to send any TAU or RAU request, as long as it remains within the registered RA and TA list. ISR aims at reducing the frequency of TAU and RAU procedures caused by UEs reselecting between E-UTRAN and GERAN/UTRAN which are operated together. Consequently, ISR reduces the mobility signaling and improves the battery life of UEs. ISR not only reduces the signaling between UE and network, but also reduces the signaling between E-UTRAN and

UTRAN/GERAN. The HSS needs also to maintain two PS registrations (one from the MME and another from the SGSN). The UE keeps the two registrations in parallel and run periodic timers for both registrations independently. Similarly, the UE keeps the two registrations in parallel and it also ensures that the UE can be paged in both the RA and the TAs it is registered in. ISR support is mandatory for E-UTRAN UEs that support GERAN and/or UTRAN and optional for the network. ISR requires special functionality in both the UE and the network (i.e. in the SGSN, MME, SGW and HSS) to activate ISR for a UE. The network can decide for ISR activation individually for each UE. When ISR is activated this means that the UE is registered with both the

MME and the SGSN. Both the SGSN and the MME have a control connection with the SGW. MME and SGSN are both registered at the HSS. The UE stores parameters from the SGSN (e.g. P-TMSI and RA) and from the MME (e.g. GUTI and TA(s)). The UE further stores session management (bearer) contexts that are common for E-UTRAN and GERAN/UTRAN accesses. In idle state the UE may reselect between E-UTRAN and GERAN/UTRAN (within the registered RA and TAs) without any need to perform TAU or RAU procedures with the network. The SGSN and the MME store each other's address when ISR is activated. ISR is deactivated in the UE when the UE cannot perform periodic updates in time.

In order to obtain management of SGW failure with ISR active, embodiments herein provide a master ISR associated mobility management node, MMN, a method performed in the master ISR associated MMN 5, a computer program comprising code, for example in the form of a computer program product, that when run on a the master ISR associated MMN 5, causes the master ISR associated MMN 5 to perform the method. There is also provided a slave ISR associated mobility management node, MMN, a method performed in the slave ISR associated MMN 9, a computer program comprising code, for example in the form of a computer program product, that when run on the slave ISR associated MMN 9, causes the slave ISR associated MMN 9 to perform the method. There is also provided a serving gateway, SGW, a method performed in the SGW, a computer program comprising code, for example in the form of a computer program product, that when run on the SGW, causes the SGW to perform the method.

According to embodiments the disclosed concepts may be based on adaptations of the above described MME and/or SGSN. These two nodes are core network nodes and may be denoted mobility management nodes,

MMNs. The disclosed concept may, according to embodiments also be based on adaptations of mobility management nodes in the RAN, such as the above described RNC and/or BSC. In general terms the mobility management nodes may be regarded as core network mobility management nodes. Figure 5 schematically illustrates, in terms of a number of functional modules, the components of a master ISR associated MMN 5. A processing unit 6 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate arrays (FPGA) etc., capable of executing software instructions stored in a computer program product 17 (as in Fig 8), e.g. in the form of a memory 8. Thus the processing unit 6 is thereby arranged to execute methods as herein disclosed. The memory 8 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The master ISR associated MMN 5 further comprises an input/output (I/O) interface 7 arranged to receive and to transmit signals to other devices, such as the slave ISR associated MMN 9 and the SGW 13. The processing unit 6 controls the general operation of the master ISR associated MMN 5, e.g. by sending control signals to the I/O interface 7 and receiving reports from the I/O interface 7 of its operation. Other components, as well as the related functionality, of the master ISR associated MMN 5 are omitted in order not to obscure the concepts presented herein. According to one embodiment the master ISR associated MMN 5 is implemented as an independent device. According to an embodiment the master ISR associated MMN 5 is provided as part of a mobile management entity, MME. According to an embodiment the master ISR associated MMN 5 is provided as part of a serving GPRS support node, SGSN. As part of an MME or an SGSN the master ISR associated MMN 5 may thus be readily implemented in any one of the above disclosed wireless communications systems 1, 2, 3 and 4.

Figure 6 schematically illustrates, in terms of a number of functional modules, the components of a slave ISR associated MMN 9. A processing unit 10 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate arrays (FPGA) etc., capable of executing software instructions stored in a computer program product 17 (as in Fig 8), e.g. in the form of a memory 12. Thus the processing unit 10 is thereby arranged to execute methods as herein disclosed. The memory 12 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The slave ISR associated MMN 9 further comprises an input/output (I/O) interface 11 arranged to receive and to transmit signals to other devices, such as the master ISR associated MMN 5 and the SGW 13. The processing unit 10 controls the general operation of the slave ISR associated MMN 9, e.g. by sending control signals to the I/O interface 11 and receiving reports from the I/O interface 11 of its operation. Other

components, as well as the related functionality, of the slave ISR associated MMN 9 are omitted in order not to obscure the concepts presented herein. According to one embodiment the slave ISR associated MMN 9 is

implemented as an independent device. According to an embodiment the slave ISR associated MMN 9 is provided as part of a mobile management entity, MME. According to an embodiment the slave ISR associated MMN 9 is provided as part of a serving GPRS support node, SGSN. As part of an l8

MME or an SGSN the slave ISR associated MMN 9 may thus be readily implemented in any one of the above disclosed wireless communications systems 1, 2, 3 and 4.

Figure 7 schematically illustrates, in terms of a number of functional modules, the components of a serving gateway, SGW, 13. A processing unit 14 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate arrays (FPGA) etc., capable of executing software instructions stored in a computer program product 17 (as in Fig 8), e.g. in the form of a memory 16. Thus the processing unit 14 is thereby arranged to execute methods as herein disclosed. The memory 16 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The SGW 13 further comprises an input/output (I/O) interface 15 arranged to receive and to transmit signals to other devices, such as the master ISR associated MMN 5 and the slave ISR associated MMN 9. The processing unit 14 controls the general operation of the SGW 13, e.g. by sending control signals to the I/O interface 15 and receiving reports from the I/O interface 15 of its operation. Other components, as well as the related functionality, of the SGW 13 are omitted in order not to obscure the concepts presented herein. According to one embodiment the SGW 13 is implemented as an independent device. The SGW 13 may thus be readily implemented in any one of the above disclosed wireless communications systems 1, 2, 3 and 4·

Figures 9 and 10 are flow charts illustrating embodiments of methods performed by the master ISR associated MMN 5 for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active. Figures 11 and 12 are flow charts illustrating embodiments of methods performed by the slave ISR associated MMN 9 for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active. Figures 13 and 14 are flow charts illustrating embodiments of methods performed by the SGW 13 for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active.

The methods are advantageously provided as computer programs 18a, 18b, 18c. Figure 8 shows one example of a computer program product 17 comprising computer readable means 19. On this computer readable means 19, at least one computer program 18a, 18b, 18c can be stored, which computer program 18a, 18b, 18c can cause the processing units 6, 10, 14 and thereto operatively coupled entities and devices, such as the memories 8, 12, 14, and/or the I/O interfaces 7, 11, 15 to execute methods according to embodiments described herein. In the example of Figure 8, the computer program product 17 is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable

programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory. Thus, while the computer programs 18a, 18b, 18c are here schematically shown as a track on the depicted optical disk, the computer programs 18a, 18b, 18c can be stored in any way which is suitable for the computer program product 17.

When ISR is deployed in one PLMN one of the ISR associated nodes, either the MME or the SGSN, is determined to be a so-called master ISR associated mobility management node, MMN and is thereby made responsible for handling SGW failure, the SGW 13 being associated with a UE with ISR active, by managing a SGW relocation procedure. A method for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, as performed by a master ISR associated mobility management node, MMN, therefore comprises, in a step S102, acquiring an indication of an SGW failure. The SGW 13 is associated with a number of user equipment, UE, with ISR active. The indication is acquired by the I/O interface 7 of the master ISR associated MMN 5. According to an embodiment the SGW relocation is performed for those UEs of the number of UEs that are in an idle state. The SGW relocation may be performed also for the Active UEs. But according to an embodiment the herein disclosed SGW relocation is performed only for those UEs of the number of UEs that are in an idle state. The master ISR associated MMN 5 may be pre-configured to manage the SGW relocation procedure. That is, according to an embodiment the master ISR associated MMN 5 is preconfigured to perform the SGW relocation at the SGW failure. Otherwise, if pre-configuration is not used, it may be negotiated during the ISR establishment. That is, according to an embodiment it is in a step Sn8a negotiated during ISR establishment, that the master ISR associated MMN 5 is decided to perform the SGW relocation at the SGW failure. The negotiation may occur during either a context transfer procedure or an inter RAT handover procedure. The negotiation is performed by the processing unit 6 of the master ISR associated MMN 5. When the SGW failure has been detected by the master ISR associated MMN 5, the master ISR associated MMN 5 informs slave ISR associated MMNs 9 that are to restore the UE's PDN connection before the actual SGW relocation procedure is to be started. The master ISR associated MMN 5 selects an available SGW 13 and relocates the PDN connection to this SGW 13. That is, the I/O interface 7 of the master ISR associated MMN 5 is arranged to, in a step S104 provide a notification message to a slave ISR associated MMN 9. The notification message indicates that the master ISR associated MMN 5 is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW 13. The notification message is received by at least one slave ISR associated

MMN 9. The I/O interface 11 of the slave ISR associated MMN 9 is therefore arranged to, in a step S122, receive the notification message.

The notification message allows the slave ISR associated MMN 9 to take a proper action if the UE happens to send uplink NAS message using the other radio access technology scheme other than the radio access technology scheme of the master ISR associated MMN 5.

For example, if the slave ISR associated MMN 9 receives the notification message that the master ISR associated MMN 5 is to relocate the SGW 13 for UEs in Idle, and if at the same time, the slave ISR associated MMN 9 receives an UE uplink NAS message, e.g. a Service Request, TAU/RAU, slave ISR associated MMN 9 may either reject the notification message from the master ISR associated MMN 5, and indicate to the master ISR associated MMN 5 that it shall not continue with the SGW restoration procedure for this UE since the UE may be camping on the radio access technology scheme of the slave ISR associated MMN 9; or accept the notification message, but delay handling UE requests until the SGW 13 has been successfully relocated. This will be further disclosed below.

The processing unit 6 of the master ISR associated MMN 5 is further arranged to, in a step S106, perform the SGW relocation and re- establishment of the ISR association such that the PDN connection is relocated to the selected new SGW 13. The SGW relocation does not require the support of PGW triggered SGW restoration, and it avoids paging signaling. Particular embodiments of the SGW relocation will now be disclosed with reference to the sequence diagram of Figure 15. It is here assumed that the master ISR associated MMN 5 either is pre-configured or has been negotiated (during ISR establishment at context transfer procedure between the MME and SGSN) to perform the SGW restoration procedure. As noted above with reference to step S102 the SGW failure may be detected by the master ISR associated MMN 5 acquiring a message with information indicating SGW failure. The message may be received from the failed SGW 13 itself or by diagnostic activities performed by the processing unit 6 of the master ISR associated MMN 5. The master ISR associated MMN 5 may therefore be arranged to transmit (e.g. periodically or at particular events or the like) status requests to the SGW 13, where a missing reply or a reply with failure information (i.e., information indicating a SGW failure) may indicate a SGW failure.

After detection of the SGW failure, the slave ISR associated MMN 9, optionally, if the master ISR associated MMN 5 was not already informed, may inform the master ISR associated MMN 5 about which UEs are in the Active mode in the 2G/3G radio access technology scheme, so that the master ISR associated MMN 5 need not to perform SGW relocation for those UEs. Note that there is a difference between an UE in Active mode and an UE in ISR active. ISR active is an idle mode for the UE. For an UE in Active mode, at least one of the master 5 or slave 9 ISR associated MMN has access to information regarding which entity the UE is operatively connected (either to the MME or the SGSN). Thereby the master 5 or slave 9 ISR associated MMN can directly perform SGW relocation and deactivate ISR (preferably so as to keep the UE context only in the MME or in the SGSN depending to which of these the UE is operatively connected); for an UE in idle mode, neither the master ISR associated MMN 5 nor the slave ISR associated MMN 9 has access to information regarding to which entity the UE is operatively connected., In such a case it may be preferred that the master ISR associated MMN 5 performs SGW relocation but inform the slave ISR associated MMN 9 to activate the ISR again, i.e. to restore the status as before the SGW failure. The I/O interface 11 of the slave ISR associated MMN 9 may thus be arranged to, in a step Si24a, provide an information message to the master ISR associated MMN 5 about which UEs of the number of UEs are in an active mode in the radio access technology scheme controlled by the slave ISR associated MMN 9. The I/O interface 7 of the master ISR associated MMN 5 may therefore be arranged to, in a step Sio8a, receive the information message. The master ISR associated MMN 5 may then further be arranged to, in a step Sio8b, exclude the UEs that are in the active mode from the SGW relocation process and re-establish the ISR association of the UEs. Further, if in an MO service request procedure, the slave ISR associated MMN 9 did not send an "ISR deactivation Indication" message (as mentioned in 3GPP TR 23.857 V1.10), the master ISR associated MMN 5 does not know for this UE if the SGW relocation procedure has been performed. This UE appears to the master ISR associated MMN 5 as idle mode. The slave ISR associated MMN 9 may use an S3 message to inform the master ISR associated MMN 5 may about which UEs are in the Active mode in the other radio access technology scheme where the slave ISR associated MMN 9 may is connected. Thus, according to an embodiment the information message is an S3 based message. The S3 based message may be an ISR status Notification message.

S3 based messages may allow the master ISR associated MMN 5 to inform the slave ISR associated MMN 9 that the master ISR associated MMN 5 is going to perform the SGW relocation. As noted above this may allow the slave ISR associated MMN 9 to take a proper action. Particularly, the I/O interface 11 of the slave ISR associated MMN 9 may thus be arranged to, in a step Si26a, in response to receiving the notification message, transmit an acceptance message pertaining to the slave ISR associated MMN 9 having accepted the notification. As a consequence thereof the slave ISR associated MMN 9 may buffer any received UE requests and may continue handling UE requests after ISR is re-established or deactivated. The I/O interface 7 of the master ISR associated MMN 5 may thus be arranged to, in a step Snoa, receive the acceptance message pertaining to the slave ISR associated MMN 9 having accepted the notification.

In order to further inform the master ISR associated MMN 5 the acceptance message, according to an embodiment, further comprises information regarding which actions the slave ISR associated MMN 9 will perform. That is, the acceptance message may further comprises information that the slave ISR associated MMN 9 is to buffer any received UE requests and to continue handling UE requests after ISR is re-established or deactivated such that the master MMN can adapt its further actions accordingly.

Alternatively, the I/O interface 11 of the slave ISR associated MMN 9 may be arranged to, in a step Si26b, in response to receiving the notification message, transmit a rejection message pertaining to the slave ISR associated MMN 9 having rejected the notification. As a consequence thereof the slave ISR associated MMN 9 may handle UEs by performing the SGW relocation procedure and request the master ISR associated MMN 5 to delete the UE context locally. The I/O interface 7 of the master ISR associated MMN 5 may thus be arranged to, in a step Snob, receive the rejection message pertaining to the slave ISR associated MMN 9 having rejected the notification. The notification message and/or it response message (acceptance message or rejection message) may be S3 based messages. In order to further inform the master ISR associated MMN 5 the rejection message, according to an embodiment, further comprises information regarding which actions the slave ISR associated MMN 9 will perform. That is, the rejection message may further comprises information that the slave ISR associated MMN 9 is to handle UEs by performing the SGW relocation procedure and request the master ISR associated MMN 5 to delete the UE context locally such that the master MMN can adapt its further actions accordingly.

Next the master ISR associated MMN 5 may select a new SGW 13 as outlined above, e.g. with reference to step S106 in Figures 9-10. The master ISR associated MMN 5 may transmit a Create Session Request message or similar and receive a corresponding Create Session Response or similar. In

particular, the I/O interface 7 of the master ISR associated MMN 5 may be arranged to, in a step Sii2a, transmit a request message to the selected new SGW 13 to restore the PDN connection. The request message may be a create session request message. The request message is based on an indication of an SGW failure of a first SGW 13 having been acquired by the master ISR associated MMN 5. The request message pertains to a session to be created by the selected new SGW 13. As noted above the first SGW 13 is associated with said number of user equipment. The session therefore relates to setup of a new communication path for the number of UEs. The I/O interface 15 of the new selected SGW 13 may therefore be arranged to, in a step S142, receive the request message from the master ISR associated MMN 5. The processing unit 14 of the new selected SGW 13 is arranged to, in a step S144, create the session. The I/O interface 15 of the new selected SGW 13 may thereafter be arranged to, in a step S146, transmit a response message to the master ISR associated MMN 5. The response message pertains to the session having been created by the SGW 13. The I/O interface 7 of the master ISR associated MMN 5 may thereafter be arranged to, in a step Sii2b, receive the response message.

The master ISR associated MMN 5 may then inform the slave ISR associated MMN 9 the selected SGW 13, for example via an S3 message, e.g. an ISR status Notification, to request the slave ISR associated MMN 9 to send a Modify bearer Request message to the selected new SGW 13. In such a Modify Bearer Request message, the slave ISR associated MMN 9 could indicate that ISR is activated. Particularly, the I/O interface 7 of the master ISR associated MMN 5 may be arranged to, in a step Sii4a, transmit a request message pertaining to an identifier of the selected new SGW 13 to the slave ISR associated MMN 9. The request message comprises a request for the slave ISR associated MMN 9 to transmit a Modify bearer Request message to the selected new SGW 13 indicated by the SGW identifier to reestablish ISR for the UEs. The identifier of the selected new SGW 13 may be at least one of an SGW Fully Qualified Domain Name (FQDN) and an SGW Fully Qualified Tunnel End Point Identifier (F-TEID). The I/O interface 11 of the slave ISR associated MMN 9 may therefore be arranged to, in a step

Si28a, receive the request message from the master ISR associated MMN 5. The request message may be an S3 based message. An S3 based message and its response message may thus allow the master ISR associated MMN 5 to inform the slave ISR associated MMN 9 to send a Modify Bearer Request message to the selected SGW 13 to activate ISR or deactivate ISR.

Next, if the slave ISR associated MMN 9 does not receive any UE uplink NAS request, the slave ISR associated MMN 9 may send a Modify Bearer Request message, where ISR is indicated to be activated. The slave ISR associated MMN 9 may then receive a Modify bearer response message from the selected new SGW 13. Particularly, the I/O interface 11 of the slave ISR associated MMN 9 may be arranged to, in a step Si3oa and in a case the slave ISR associated MMN 9 does not receive any UE uplink non-access stratum, NAS, requests, transmit a modify bearer request message to the selected new SGW 13 requesting ISR to be activated or deactivated. The I/O interface 15 of the selected new SGW 13 may be arranged to, in a step Si48a, receive the modify bearer request message from the slave ISR associated MMN 9. The processing unit 14 of the selected new SGW 13 is thereafter arranged to, in a step Si48b, activate or deactivate ISR for the UE. The I/O interface 15 of the selected new SGW 13 may then be arranged to, in a step S148C, transmit a modify bearer response message to the slave ISR associated MMN 9. The response message pertains to the ISR having been activated or deactivated. The I/O interface 11 of the slave ISR associated MMN 9 may therefore be arranged to, in a step Si3ob receive the modify bearer response message from the selected new SGW 13.

The slave ISR associated MMN 9 may then confirm to the master ISR associated MMN 5 that ISR is activated. As noted above the slave ISR associated MMN 9 may decide to deactivate ISR if the slave ISR associated MMN 9 receives an UE uplink NAS request during this procedure.

Particularly, the I/O interface 11 of the slave ISR associated MMN 9 may be arranged to, in a step Si32a, provide the master ISR associated MMN 5 with a confirmation message that ISR is activated. The I/O interface 7 of the master ISR associated MMN 5 may therefore be arranged to, in a step Sn6a, receive the confirmation message from the slave ISR associated MMN 9 that ISR is activated. Similarly, if ISR is deactivated, the I/O interface 11 of the slave ISR associated MMN 9 may be arranged to, in a step Si32b, provide the master ISR associated MMN 5 with an indication message that ISR is deactivated. The I/O interface 7 of the master ISR associated MMN 5 may therefore be arranged to, in a step Sn6b, receive the indication message from the slave ISR associated MMN 9 that ISR is deactivated. The processing unit 6 of the master ISR associated MMN 5 may thereafter be arranged to, in a step Sii6c, delete the UE context locally. The communication systems 1, 2, 3 and 4 may be arranged for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active by comprising a master ISR associated MMN 5, a slave ISR associated MMN 9 and an SGW 13. According to an embodiment, in case the master ISR associated MMN 5 is part of an MME the slave ISR associated MMN 9 is part of an SGSN. According to an embodiment, in case the master ISR associated MMN 5 is part of an SGSN the slave ISR associated MMN 9 is part of an MME. The above disclosed methods are per UE based (according to some embodiments over the S3 interface) and per PDN connection based

(according to some embodiments over S11/S4 interface, between

MME/SGSN and SGW 13). From the above disclosed steps and features it is clear that the SGW relocation procedure does not involve any NAS procedure such as Service Request, TAU/RAU.

The present disclosure has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the present disclosure, as defined by the appended patent claims.

ABBREVATIONS

A number of signaling interfaces and signaling and data transfer interfaces are used in the wireless communication systems 1, 2, 3, 4:

Si-MME: Reference point for the control plane protocol between E-UTRAN and MME.

Si-U: Reference point between E-UTRAN and Serving GW for the per bearer user plane tunnelling and inter eNodeB path switching during handover.

S3: It enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state.

S4: It provides related control and mobility support between GPRS

Core and the 3GPP Anchor function of Serving GW. In addition, if Direct Tunnel is not established, it provides the user plane tunnelling.

S5: It provides user plane tunnelling and tunnel management between

Serving GW and PDN GW. It is used for Serving GW relocation due to UE mobility and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity.

It enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME and HSS.

It provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW.

Inter-PLMN reference point providing user and control plane between the Serving GW in the VPLMN and the PDN GW in the HPLMN. S8 is the inter PLMN variant of S5.

It provides transfer of (QoS) policy and charging control information between the Home PCRF and the Visited PCRF in order to support local breakout function.

Reference point between MMEs for MME relocation and MME to

MME information transfer.

Reference point between MME and Serving GW.

Reference point between UTRAN and Serving GW for user plane tunnelling when Direct Tunnel is established. It is based on the Iu- u/Gn-u reference point using the GTP-U protocol as defined between SGSN and UTRAN or respectively between SGSN and

GGSN. Usage of S12 is an operator configuration option.

It enables UE identity check procedure between MME and EIR.

It is the reference point between the PDN GW and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. This reference point corresponds to Gi for 3GPP accesses.

The Rx reference point resides between the AF and the PCRF in the 3GPP TS 23.203.

Application Function

Access Network

Allocation and Retention Priority AMBR Aggregate Maximum Bit Rate

ANDSF Access Network Discovery and Selection Function

BBERF Bearer Binding and Event Reporting Function

BSC Base Station Controller

BSS Base Station System

BSSGP Base Station System GPRS Protocol

BTS Base Station

CBC Cell Broadcast Centre

CBE Cell Broadcast Entity

CCoA Collocated Care-of-address

CN Core Network

CSG Closed Subscriber Group

CSG ID Closed Subscriber Group Identity

DL TFT DownLink Traffic Flow Template

DSMIPv6 Dual-Stack MIPv6

eAN enhanced AN

ECGI E-UTRAN Cell Global Identifier

ECM EPS Connection Management

ECN Explicit Congestion Notification

eGTP enhanced Gateway Tunnelling Protocol

eNodeB enhanced Node B

EMM EPS Mobility Management

EPC Evolved Packet Core

EPS Evolved Packet System

ePDG Evolved Packet Data Gateway

E-RAB E-UTRAN Radio Access Bearer

E-UTRAN Evolved Universal Terrestrial Radio Access Network

FACoA Foreign Agent Care-of-Address

GBR Guaranteed Bit Rate

GERAN GSM Edge Radio Access Network

GGSN Gateway GPRS Support Node

GPRS General Packet Radio Service

GRE Generic Routing Encapsulation

GSM Global Communications System

GTP GPRS Tunneling Protocoll

GTP-C GTP control

GTP-U GTP user data tunneling

GUMMEI Globally Unique MME Identifier

GUTI Globally Unique Temporary Identity

GW Gateway

H ANDSF Home-ANDSF

HeNB Home eNode B

HeNB GWHome eNode B Gateway

HFN Hyper Frame Number

HO Handover

HRPD High Rate Packet Data

HSS Home Subscriber Server

HSGW HRPD Serving GateWay

IE Information Element IETF Internet Engineering Task Force

IMSI International Mobile Station Identity

IFOM IP Flow Mobility

IP Internet Protocol

IPMS IP Mobility management Selection

ISR Idle mode Signalling Reduction

LB I Linked EPS Bearer Id

L-GW Local GateWay

LIPA Local IP Access

LMA Local Mobility Anchor

LTE Long Term Evolution

MAG Mobile Access Gateway

MAPCON Multi Access PDN Connectivity

MBR Maximum Bit Rate

MIB Minimum Bit Rate

MIPv4 Mobile IP version 4

MIPv6 Mobile IP version 6

MME Mobility Management Entity

MMEC MME Code

MSC Mobile Switching Center

MTC Machine-Type Communications

M-TMSI M-Temporary Mobile Subscriber Identity

OFCS Offline Charging System

OMC-ID Operation and Maintenance Centre Identity

PCC Policy Control and Charging

PCF Packet Control Function

PCEF Policy and Charging Enforcement Function

PCRF Policy and Charging Rules Function

PDN Packet data Network

PDP Packet Data Protocol

PGW PDN Gateway

PDCP Packet Data Convergence Protocol

PLMN Public Land Mobile Network

PMIP Proxy Mobile IP

ΡΜΙΡνό Proxy Mobile IP version 6

PS Packet Switched

PSAP Public Safety Answering Point

PTI Procedure Transaction Id

QCI QoS Class Identifier

QoS Quality of Service

OCS Online Charging Systems

QSUP QoS based on Service information in User Plane protocol

RAN Radio Access Network

RAU Routing Area Update

RFSP RAT/Frequency Selection Priority

RNAP Radio Access Network Application Part

RNC Radio Network Controller

SACC Service Aware Charging and Control

SGSN Serving GPRS Support Node SGW Serving Gateway

SectorlD Sector Address Identifier

S-TMSI S-Temporary Mobile Subscriber Identity

SDF Service Data Flow

SI Service Identification

SIPTO Selected IP Traffic Offload

TAC Tracking Area Code

TAD Traffic Aggregate Description

TAI Tracking Area Identity

TAU Tracking Area Update

TDF Traffic Detection Function

TEID Tunnel End Point Identifier

TI Transaction Identifier

TIN Temporary Identity used in Next update

TDF Traffic Detection Function

UE User Equipment

UDP User Datagram Protocol

UMTS Universal Mobile Telecommunications System

URRP-MME UE Reachability Request Parameter for MME UTRAN UMTS Terrestria Radio Access Network

UL TFT UpLink Traffic Flow Template

ULR- Flags Update Location Request Flags

VLR Visitor Location Register

VANDSF Visited-ANDSF

VS Vendor Specific

Claims

1. A method for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the method being performed by a master ISR associated mobility management node, MMN, (5) and comprising:

acquiring (S102) an indication of an SGW failure, the SGW (13) being associated with a number of user equipment, UE, with ISR active;

providing (S104) a notification message to a slave ISR associated MMN (9), that said master ISR associated MMN (5) is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW (13); and

performing (S106) SGW relocation and re-establishment of the ISR association such that the PDN connection is relocated to the selected new SGW (13).

2. The method according to claim 1, wherein performing SGW relocation and re-establishment of the ISR association is performed for those UEs of the number of UEs that are in an idle state.

3. The method according to claim 1 or 2, wherein performing SGW relocation and re-establishment of the ISR association comprises:

receiving (Sio8a) an information message from the at least one slave ISR associated MMN (9) about which UEs of the number of UEs are in an active mode in the radio access technology scheme controlled by the slave ISR associated MMN (9); and

excluding (Sio8b) said UEs that are in the active mode from the SGW relocation process and re-establish the ISR association of said UEs.

4. The method according to any one of claims 1 to 3, wherein the information message is an S3 based message.

5. The method according to any one of claims 1 to 4, wherein the notification message is an S3 based message.

6. The method according to any one of claims l to 5, further comprising: receiving (Snoa), in response to transmitting the notification message and from the slave ISR associated MMN (9), an acceptance message pertaining to said slave ISR associated MMN (9) having accepted the notification and as a consequence thereof that said slave ISR associated

MMN (9) is to buffer any received UE requests and to continue handling UE requests after ISR is re-established or deactivated.

7. The method according to any one of claims 1 to 5, further comprising: receiving (Snob), in response to transmitting the notification message and from the slave ISR associated MMN (9), a rejection message pertaining to said slave ISR associated MMN (9) having rejected the notification and as a consequence thereof that said slave ISR associated MMN (9) is to handle UEs by performing the SGW relocation procedure and request the master ISR associated MMN (5) to delete the UE context locally.

8. The method according to any one of claims 1 to 7, wherein performing SGW relocation and re-establishment of the ISR association comprises:

transmitting (Sii2a) a request message to the selected new SGW (13) to restore the PDN connection, the request message pertaining to a session to be created by the selected new SGW (13), the session relating to setup of a new communication path to the number of UEs; and

receiving (Sii2b) a response message from the selected new SGW (13), the response message pertaining to the session having been created by the selected new SGW (13).

9. The method according to claim 8, wherein the request message a create session request message.

10. The method according to any one of claims 1 to 9, wherein performing SGW relocation and re-establishment of the ISR association comprises:

transmitting (Sii4a) a request message pertaining to an identifier of the selected new SGW (13) to the slave ISR associated MMN (9), the request message comprising a request for the slave ISR associated MMN (9) to transmit a Modify bearer Request message to the selected new SGW (13) indicated by the SGW identifier to re-establish ISR for the UEs.

11. The method according to claim 10, wherein the request message is an S3 based message.

12. The method according to any one of claims 1 to 11, wherein performing SGW relocation and re-establishment of the ISR association comprises:

receiving (Sn6a) a confirmation message from the slave ISR associated MMN (9) that ISR is activated.

13. The method according to any one of claims 1 to 11, wherein performing SGW relocation and re-establishment of the ISR association comprises:

receiving (Sn6b) an indication message from the slave ISR associated MMN (9) that ISR is deactivated; and

deleting (Sn6c) the UE context locally.

14. The method according to any one of claims 1 to 13, wherein the master ISR associated MMN (5) is preconfigured to perform the SGW relocation at the SGW failure.

15. The method according to any one of claims 1 to 13, further comprising, prior to the step of performing SGW relocation:

negotiating (Sn8a), during ISR establishment, that the master ISR associated MMN (5) is decided to perform the SGW relocation at the SGW failure.

16. A method for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the method being performed by a slave ISR associated mobility management node, MMN, (9) and comprising:

receiving (S122) a notification message, the notification message being based on an indication of an SGW failure, the SGW (13) being associated with a number of user equipment, UE, with ISR active, the notification message notifying that a master ISR associated MMN (5) is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW (13) and re-establish the ISR association such that the PDN connection is relocated to the selected new SGW (13).

17. The method according to claim 16, further comprising:

providing (Si24a) an information message to the master ISR associated MMN (5) about which UEs of the number of UEs are in an active mode for the master ISR associated MMN (5) to exclude said UEs that are in the active mode in the radio access technology scheme controlled by the slave ISR associated MMN (9) from the SGW relocation process and to re-establish the ISR association of said UEs.

18. The method according to claim 17, wherein the information message is an S3 based message.

19. The method according to any one of claims 16 to 18, wherein the notification message is an S3 based message.

20. The method according to any one of claims 16 to 19, further comprising: transmitting (Si26a), in response to receiving the notification message, an acceptance message pertaining to said slave ISR associated MMN (9) having accepted the notification and as a consequence thereof that said slave ISR associated MMN (9) is to buffer any received UE requests and to continue handling UE requests after ISR is re-established or deactivated.

21. The method according to any one of claims 16 to 19, further comprising: transmitting (Si26b), in response to receiving the notification message, a rejection message pertaining to said slave ISR associated MMN (9) having rejected the notification and as a consequence thereof that said slave ISR associated MMN (9) is to handle UEs by performing the SGW relocation procedure and request the master ISR associated MMN (5) to delete the UE context locally.

22. The method according to any one of claims 16 to 21, further comprising: receiving (Si28a) a request message pertaining to an identifier of the selected new SGW (13) from the master ISR associated MMN (5), the request message comprising a request for the slave ISR associated MMN (9) to transmit a modify bearer request message to the selected new SGW (13) indicated by the SGW identifier to re-establish ISR for the UEs.

23. The method according to claim 22, wherein the request message is an S3 based message.

24. The method according to any one of claims 16 to 23, further comprising, in a case the slave ISR associated MMN (9) does not receive any UE uplink non-access stratum, NAS, requests:

transmitting (Si3oa) a modify bearer request message to the selected new SGW 13 requesting ISR to be activated or deactivated; and

receiving (Si3ob) a modify bearer response message from the selected new SGW (13), the response message pertaining to the ISR having been activated or deactivated.

25. The method according to any one of claims 16 to 24, further comprising: providing (Si32a) the master ISR associated MMN (5) with a

confirmation message that ISR is activated.

26. The method according to any one of claims 16 to 24, further comprising: providing (Si32b) the master ISR associated MMN (5) with an information message that ISR is deactivated.

27. A method for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the method being performed by a serving gateway, SGW, (13), and comprising:

receiving (S142) a request message from a master ISR associated mobility management node, MMN, (5) the request message pertaining to a session to be created by the SGW (13), the session relating to setup of a new communication path to a number of UEs with ISR active and affected by the SGW failure, wherein the request message is based on an indication of an SGW failure of a first SGW (13) having been acquired by the master ISR associated MMN (5), the first SGW (13) being associated with said number of user equipment; creating (S144) the session; and

transmitting (S146) a response message to the master ISR associated MMN (5), the response message pertaining to the session having been created by the SGW (13).

28. The method according to claim 27, wherein the request message is one from a create session request message.

29. The method according to claim 27 or 28, further comprising:

receiving (Si48a) a modify bearer request message from a slave ISR associated MMN (9), requesting ISR to be activated or deactivated, the modify bearer request message having been transmitted by the slave ISR associated MMN (9) in a case the slave ISR associated MMN (9) does not receive any UE uplink non-access stratum, NAS, requests;

activating or deactivating (Si48b) the ISR; and

transmitting (S148C) a modify bearer response message to the slave ISR associated MMN (9), the response message pertaining to the ISR having been activated or deactivated.

30. A master idle mode signalling reduction, ISR, associated mobility management node, MMN, (5) for managing server gateway, SGW, failure when idle mode signalling reduction, ISR, is active, comprising:

an input/output, I/O, interface (7) arranged to acquire an indication of an SGW failure, the SGW (13) being associated with a number of user equipment, UE, with ISR active;

the I/O interface (7) further being arranged to providing a notification message to a slave ISR associated MMN (9), that said master ISR associated MMN (5) is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW (13); and

a processing unit (6) arranged to perform SGW relocation and re- establishment of the ISR association such that the PDN connection is relocated to the selected new SGW (13).

31. The master ISR associated MMN (5) according to claim 30, wherein the master ISR associated MMN (5) is part of a mobile management entity, MME, or a serving GPRS support node, SGSN.

32. A slave idle mode signalling reduction, ISR, associated mobility management node, MMN, (9) for managing server gateway, SGW, failure when idle mode signalling reduction, ISR, is active, comprising:

an input/output, I/O, interface (11) arranged to receive a notification message, the notification message being based on an indication of an SGW failure, the SGW (13) being associated with a number of user equipment, UE, with ISR active, the notification message notifying that a master ISR associated MMN (5) is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW (13) and re-establish the ISR association such that the PDN connection is relocated to the selected new SGW (13).

33. The slave ISR associated MMN (9) according to claim 32, wherein the slave ISR associated MMN (9) is part of a mobile management entity, MME, or a serving GPRS support node, SGSN.

34. A serving gateway, SGW, (13) for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, comprising:

an input/output, I/O, interface (15) arranged to receive a request message from a master ISR associated mobility management node, MMN, (5) the request message pertaining to a session to be created by the SGW (13), the session relating to setup of a new communication path to a number of UEs with ISR active and affected by the SGW failure, wherein the request message is based on an indication of an SGW failure of a first SGW (13) having been acquired by the master ISR associated MMN (5), the first SGW (13) being associated with said number of user equipment;

a processing unit (14) arranged to create the session; and

the I/O interface (15) further being arranged to transmit a response message to the master ISR associated MMN (5), the response message pertaining to the session having been created by the SGW (13).

35. A system (1, 2, 3, 4) for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the system (1, 2 3, 4) comprising:

a master idle mode signalling reduction, ISR, associated mobility management node, MMN, (5) according to claim 30;

a slave ISR associated MMN (9) according to claim 32; and

an SGW (13) according to claim 34.

36. The system (1, 2, 3, 4) according to claim 35, wherein in a case the master ISR associated MMN (5) is part of a mobile management entity, MME, the slave ISR associated MMN (9) is part of a serving GPRS support node, SGSN, and wherein in a case the master ISR associated MMN (5) is part of a SGSN, the slave ISR associated MMN (9) is part of an MME.

37. A computer program (18a) for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the computer program (18a) comprising computer program code which, when run on a master idle mode signalling reduction, ISR, associated mobility management node, MMN, (5) causes the master ISR associated MMN (5) to:

acquire an indication of an SGW failure, the SGW (13) being associated with a number of user equipment, UE with ISR active;

providing a notification message to a slave ISR associated MMN (9), that said master ISR associated MMN (5) is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW (13); and

perform SGW relocation and re-establishment of the ISR association such that the PDN connection is relocated to the selected new SGW (13).

38. A computer program (18b) for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the computer program (18b) comprising computer program code which, when run on a slave idle mode signalling reduction, ISR, associated mobility management node, MMN, (9) causes the slave ISR associated MMN (9) to:

receive a notification message, the notification message being based on an indication of an SGW failure, the SGW (13) being associated with a number of user equipment, UE, with ISR active, the notification message notifying that a master ISR associated MMN (5) is to restore a packet data network, PDN, connection of the number of UEs affected by the SGW failure by selecting a new SGW (13) and re-establish the ISR association such that the PDN connection is relocated to the selected new SGW (13).

39. A computer program (18c) for managing serving gateway, SGW, failure when idle mode signalling reduction, ISR, is active, the computer program (18c) comprising computer program code which, when run on a serving gateway, SGW, (13) causes the SGW (13) to:

receive a request message from a master ISR associated mobility management node, MMN, (5) the request message pertaining to a session to be created by the SGW (13), the session relating to setup of a new

communication path to a number of UEs with ISR active and affected by the SGW failure, wherein the request message is based on an indication of an SGW failure of a first SGW (13) having been acquired by the master ISR associated MMN (5), the first SGW (13) being associated with said number of UEs;

create the session; and

transmitting a response message to the master ISR associated MMN (5), the response message pertaining to the session having been created by the SGW (13).

40. A computer program product (17) comprising a computer program (18a, 18b, 18c) according to at least one of claims 37, 38, and 39 and a computer readable means (19) on which the computer program is stored (18a, 18b, 18c).