Network node, user equipment and methods in a wireless communications network

A method performed by a network node for restoring a Short Message Service (SMS) service in a connection between User Equipment (UE) and a communications network is provided. The UE is attached to the communications network with Evolved Packet System (EPS) attach and SMS only, via a radio network node, a Visitor Location Register (VLR) Mobile Switching Centre (MSC), and the network node. When receiving information that indicates a restart of the VLR MSC in the connection, network node sends (202) to the radio network node, an indication to trigger the UE to send a Tracking Area Update (TAU) request with SMS only. The network node receives (203) the TAU request with SMS only, triggered by the UE according to the indication sent to the radio network node. The network node then restores (204) the SMS service based on information in the TAU request with SMS only, received from the UE.

PRIORITY

This nonprovisional application is a U.S. National Stage Filing under 35 U.S.C. § 371 of International Patent Application Serial No. PCT/CN2019/072346 filed Jan. 18, 2019 and entitled “NETWORK NODE, USER EQUIPMENT AND METHODS IN A WIRELESS COMMUNICATIONS NETWORK” which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

Embodiments herein relate to a network node, a User Equipment (UE) and methods therein. In some aspects, they relate to restoring a Short Message Service (SMS) service in a connection between the UE and a communications network.

BACKGROUND

In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or User Equipments (UE), communicate via a Local Area Network such as a Wi-Fi network or a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio network node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in 5G. A service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio network node.

Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network also referred to as 5G New Radio (NR). The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs used in 3G networks. In general, in E-UTRAN/LTE the functions of a 3G RNC are distributed between the radio network nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio network nodes, this interface being denoted the X2 interface.

Attach. A UE needs to register in the network to access services. This registration is described as Network Attachment, which is referred to as attach.

Detach. The Detach procedure allows:The UE to inform the network that it does not access the network any longer, orThe network to inform the UE that the access to the network is closed by the network side.

A UE may attach to both EPS services and non-EPS services.

EPS services means services provided by Packet Switched (PS) domain.

Non-EPS services means services provided by Circuit Switched (CS) domain. Such services are for example CS voice and SMS. In general, attach to non-EPS services may be needed so that these services can be provided to a UE that is operating in LTE network, e.g. incoming/Mobile-terminated CS voice call or SMS.

An attach type indicates the purpose of an attach. There are different types of attach that may be determined. The attach type is determined by a kind of mutual agreement between a UE and the network. It means that UE indicates to the network, the attach type it want to get and the network determines based on this an attach type that is available, and informs it to UE in a following procedure:

For EPS attach, indicate an attach for EPS services only. This is also referred to as EPS only.

For Combined EPS/IMSI attach indicate an attach for both EPS and non-EPS services. IMSI is the abbreviation for International Mobile Subscriber Identity.

A Packet Data Network (PDN) connectivity procedure is used by a UE to request a setup of a default EPS bearer to a PDN e.g. for EPS services.

A UE attached for EPS services may operate in one of the following operation modes:

PS mode of operation, wherein the UE registers only to EPS services, CS/PS mode 1 of operation, voice centric, wherein the UE is CS fallback capable and configured to use CS fallback, and non-EPS services are preferred. The UE registers to both EPS and non-EPS services. A further mode is CS/PS mode 2 of operation data centric, wherein the UE is CS fallback capable and configured to use CS fallback, and EPS services are preferred. The UE registers to both EPS and non-EPS services.

An SMS with combined attach means an EPS/IMSI attach. This is a combined attach procedure, wherein an EPS attach is combined with an IMSI attach. This SMS with combined attach, may be used by a UE in CS/PS mode 1 or CS/PS mode 2 of operation to attach for both EPS services and SMS only.

This combined attach procedure may also used by a UE in CS/PS mode 1 or CS/PS mode 2 of operation to attach for EPS services if it is already IMSI attached for non-EPS services.

When a UE initiates a combined attach procedure, the UE shall indicate “combined EPS/IMSI attach” in the EPS attach type Information Element (IE) sent to the network. This is to inform the network of witch attach type the UE want to get.

Therefore, a UE who is capable to make SMS with combined attach, should also support IMSI detach procedure, which e.g. means Detach with type “IMSI Detach”. Detach when used herein means that the UE will not have non-EPS services. Detach procedure when used herein means a detach procedure with a detach type that indicates that it is for non-EPS services.

More and more N B-IoT devices are deployed in live network for Machine to Machine (M2M) services. M2M refers to direct communication between devices using any communications channel, including wired and wireless. M2M communication may e.g. include industrial instrumentation, enabling a sensor or meter to communicate the data it records such as e.g. temperature, inventory level, etc. to application software that can use it, e.g. for adjusting an industrial process based on temperature or placing orders to replenish inventory.

Based on 3GPP, N B-IoT devices support SMS without combined attach and attach without PDN connectivity.

SMS without combined attach, means that a UE does EPS attach instead of combined attach, to a communications network for EPS services and “SMS only”, if the UE supports NB-S1 mode only. Here it is realised that such kind of NB-IoT devices, who doesn't support IMSI detach, comparing with UEs who can do combined attach. This means that there is no way for an MME to trigger an IMSI detach procedure to such NB-S1 mode devices, to indicate that it will no longer have non-EPS services, e.g. SMS any more.

Attach without PDN connectivity, means that If this is supported, the UE does not need to establish a PDN connection as part of the Attach procedure. The UE and MME may at any time release all the PDN connections and remain EPS attached. Thus, a UE can be registered in an LTE network without any default PDN connection.

It means that an N B-IoT device can register to the network, even without any PDN connection, but only having SMS service over a reference point between the MME and MSC server. This reference point is referred to as SGs reference point. This means that sometimes SMS may be used to trigger PDN a connection setup. All in all, SMS service is important for NB-IoT devices.

The SGs reference point is used for mobility management and paging procedures between the EPS and a CS domain, and is based on the Gs interface procedures. The SGs reference point is also used for the delivery of both mobile originating SMS and mobile terminating SMS. Additional procedures for alignment with the Gs reference point are not precluded.

The Gs interface is the interface between the Mobile Switching Center (MSC)/Visitor Location Register (VLR) and the Serving GPRS Support Node (SGSN), where GPRS is the abbreviation for General Packet Radio Services. An association may be set up between the MSC/VLR and SGSN databases. The association is set up for further communication between SGSN and MSC, which means for a specified UE, the SGSN will communicate with the MSC via the corresponding association with the MSC. MSC/VLR when used herein means MSC and/or VLR. Through the Gs interface, location information of UEs that are attached to the GPRS and non-GPRS services can be coordinated between the SGSN and the MSC/VLR. In addition, the Gs interface may be used to complete some CS procedures through the SGSN.

Thus, the SGs is the interface that connects MME and MSC server and/or VLR. This interface connects databases between the MME and the VLR. The SGs interface is different from other interfaces in that there exists an SGs association between VLR and MME per UE.

A VLR failure is an abnormal situation in VLR, e.g. VLR restart which may be caused by for example software error in VLR which leads to a VLR restart.

Currently once a VLR failure happens the VLR will inform the MME about this, e.g. in a message comprising an indication to reset the SGs AP, sent from the VLR to the MME, such as e.g. a SGsAP-RESET-INDICATION message, wherein the SGsAP when used herein means SGs Application Part (AP) in 3GPP TS29.118.

The MME will then set the “VLR-Reliable” Mobility Management (MM) context variable to “false” in order to mark that remote VLR restarts, so the SGs association with the VLR for the impacted UE should be re-established. The IMSI detach procedures for deleting the SGs association would be applied. An IMSI is used to identify a UE of a cellular network and is a unique identification associated with all cellular networks. It may be stored as a 64 bit field and is sent by the UE to the network. The IMSI detach procedure is to detach the UE for non-EPS services only.

Tracking Area Update (TAU). An LTE network, e.g. the MME, has to have updated location information about UEs in idle state to find out in which Tracking Area (TA) a particular UE is located. For this, the UE notifies the MME of its current location by sending a TAU message, e.g. a TAU Request message every time it moves between TAs.

Within a combined tracking area updating procedure messages such as TRACKING AREA UPDATE ACCEPT and TRACKING AREA UPDATE COMPLETE carry information for both the tracking area updating and the location area updating.

Periodic tracking area updating is used by the UE to periodically notify the network about the availability of the UE to the network. A periodic Tracking Area Update (pTAU) procedure may be performed by a UE upon expiration of the TAU timer. A UE in Idle state reports its current location to the MME by sending a TAU Request message when the TAU timer expires.

Meanwhile the IMSI detach procedure is going on, the MME may according to 3GPP TS29.118 chapter 5.7.3:If a combined tracking area update request is received, immediately perform the location update for non-EPS services procedure towards the VLR; orif a periodic tracking area update request is received, dependent on network configuration and operator policy,perform a network initiated detach with detach, type “IMSI detach” immediately after the completion of the periodic TAU procedure; orimmediately perform a location update for non-EPS services procedure towards the VLR.

SUMMARY

As a part of developing embodiments herein a problem will first be identified and discussed.

For UEs being NB-IoT devices, registration into the communications network via EPS attach with SMS only indication, IMSI detach is not supported for these devices since the combined attach would not happen during the attach/TAU procedure. An attach/TAU procedure when used herein means the procedure of registering the UE into EPS network. Then once there is any VLR failure in network, the MME is unable to delete SGs association via IMSI detach unless the MME initiates the EPS detach to the UE, which will interrupt other ongoing PS services if any and it is quite battery consuming. SGs association means a logical connection between the MME and the MSCVLR for a specific UE.

Moreover, most N B-IoT devices may be stationary and provided with a very long periodic TAU timer, so SGs association re-establishment only upon TAU or pTAU as in the current solution means a big impact since all Mobile Terminating (MT) SMS cannot be sent to the UE, unless SGs association is re-established once TAU or pTAU is received from UE.

The MME thus always has to wait for a UE initiated TAU procedure, which may need quite longtime delay.

An object of embodiments herein is to improve the performance of a communications network using SMS service in connections between UEs and a communications network.

According to an aspect of embodiments herein, the object is achieved by method performed by a network node for restoring a Short Message Service, SMS, service in a connection between a User Equipment, UE, and a communications network. The UE is attached to the communications network with Evolved Packet System, EPS, attach and SMS only, via a radio network node a Visitor Location Register, VLR, Mobile Switching Centre, MSC, and the network node. When receiving information that indicates a restart of the VLR MSC in the connection, network node sends to the radio network node, an indication to trigger the UE to send a Tracking Area Update, TAU, request with SMS only. The network node receives the TAU request with SMS only, triggered by the UE according to the indication sent to the radio network node. The network node then restores the SMS service based on information in the TAU request with SMS only, received from the UE.

According to a another aspect of embodiments herein, the object is achieved by a method performed by a User Equipment, UE, for assisting a network node in restoring a Short Message Service, SMS, service in a connection between the UE and a communications network. The UE is attached to the communications network with Evolved Packet System, EPS, attach and SMS only, via a radio network node, a Visitor Location Register, VLR, Mobile Switching Centre, MSC, and a network node. When a restart of the VLR MSC in the connection is required, The UE receives an indication from the radio network node. The indication indicates to the UE, to send a Tracking Area Update, TAU, request with SMS only. The UE then assists the network node130by sending to the network node, a TAU request with SMS only according to the received indication. This enables the network node to restore the SMS service based on information in the TAU request with SMS only.

According to an aspect of embodiments herein, the object is achieved by a network node configured to restore a Short Message Service, SMS, service in a connection between a User Equipment, UE, and a communications network. The UE is adapted to be attached to the communications network with Evolved Packet System, EPS, attach and SMS only, via a radio network node, a Visitor Location Register, VLR, Mobile Switching Centre, MSC, and the network node. The network node is configured to:When receiving information indicating a restart of the VLR MSC in the connection, send to the radio network node, an indication to trigger the UE to send a Tracking Area Update, TAU, request with SMS only,receive the TAU request with SMS only, adapted to be triggered by the UE according to the indication sent to the radio network node, andrestore the SMS service based on information in the TAU request with SMS only, adapted to be received from the UE.

According to a another aspect of embodiments herein, the object is achieved by a User Equipment, UE, configured to assist a network node in restoring a Short Message Service, SMS, service in a connection between the UE and a communications network. The UE is adapted to be attached to the communications network with Evolved Packet System, EPS, attach and SMS only, via a radio network node, a Visitor Location Register, VLR, Mobile Switching Centre, MSC, and a network node. The UE is configured to:When a restart of the VLR MSC in the connection is required, receive from the radio network node, an indication to the UE, to send a Tracking Area Update, TAU, request with SMS only, andassist the network node by sending to the network node a TAU request with SMS only according to the received indication, enabling the network node to restore the SMS service based on information in the TAU request with SMS only.

Since the TAU procedure is initiated by the network node by sending an indication to the UE, to send a TAU request with SMS only, the network node do not need to wait for a UE initiated TAU procedure, which may need quite longtime delay, and the restoration of the SMS service can be performed much faster. This results in an improved performance of a communications network using SMS service in connections between UEs and a communications network.

DETAILED DESCRIPTION

Embodiments provide SMS service restoration for UEs such as NB-IoT devices upon a restart of a VLR MSC, by providing a network triggered TAU procedure so that the network node does not need to wait for a UE initiated TAU procedure which causes unwanted delay. Some example embodiments herein introduce new cause code in a UE Context Release Command to trigger the UE to perform TAU with SMS only.

According to an example, a network node such as an MME may connect the UE, e.g. page UE if the UE is in idle state such as EPS Connection Management (ECM)_Idle state (ECM_IDLE). The network node will then release an S1 connection between a base station and the EPC by using a new cause code in an UE Context Release Command message to let the base station trigger the UE to start a TAU request. Then the network node can re-establish an SGs association once a TAU is received from the UE, thereby restore SMS services.

An advantage of example embodiments herein is that they provide a network node triggered such as MME triggered TAU procedure for quick synchronization between a network and UEs such as IoT devices. This may be for some IoT related configuration, such as e.g. active timer for a Power Saving Mode (PSM) device, extended Discontinuous Reception (eDRX) cycle, Paging Time window for eDRX. This prevents a network node such as an MME the need to wait for a UE initiated TAU procedure, which may need quite longtime delay.

Embodiments herein relate to wireless communication networks in general.FIG.2is a schematic overview depicting a wireless communications network100. The wireless communications network100comprises one or more RANs and one or more CNs. The wireless communications network100may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, 5G, New Radio (NR), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments herein relate to recent technology trends that are of particular interest in a 5G context, however, embodiments are also applicable in further development of the existing wireless communication systems such as e.g. WCDMA and LTE.

In the wireless communication network100, wireless devices e.g. one or more UEs120also referred to as a device, an IoT device, a mobile station, a non-access point (non-AP) STA, a STA, a user equipment and/or a wireless terminals, communicate via one or more Access Networks (AN), e.g. RAN, to one or more core networks (CN). It should be understood by the skilled in the art that “wireless device” is a non-limiting term which means any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station communicating within a cell.

The wireless communications network100comprises a radio network node110providing radio coverage in one or more cells, such as a cell11, which may also be referred to as a beam or a beam group of beams. The radio network node110may be a NG-RAN node, transmission and reception point e.g. a base station, a radio access network node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), agNB, a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of communicating with a wireless device within the service area served by the network node110depending e.g. on the first radio access technology and terminology used. The radio network node110may be referred to as a serving radio network node and communicates with the UE120with Downlink (DL) transmissions to the UE120and Uplink (UL) transmissions from the UE120.

A number of network nodes operate in the CN such as a EPC. E.g. the network node130which may be an MME, also referred to as MME130. An MME is a main signaling node in the EPC. It is responsible for initiating paging and authentication of a UE. It also keeps location information at the Tracking Area level for each UE and is involved in choosing the right gateway during the initial registration process. MME connects to radio network nodes through the S1-MME interface and connects to gateways such as the Serving Gateway (SGW)150through the S11 interface. Multiple MMEs may be grouped together in a pool to meet increasing signaling load in the network.

A further network node operating in the CN is an MSC VLR140. The MSC VLR140is an MSC that is associated to a VLR. The MSC and the VLR in the MSC VLR140are often co-existing, but not always. An MSC is responsible for routing data packets in a wireless communications network. A VLR is a database in a wireless communications network associated to an MSC. The VLR associated with the MSC will have subscriber's data stored in it.

A further network node operating in the CN may be the SGW150. A function of an SGW is routing and forwarding of user data packets related to the UE120to and from a network such as the communications network102, which e.g. may be the internet or a local area network or any network.

Methods herein may be performed by the network node130. As an alternative, a Distributed Node (DN) and functionality, e.g. comprised in a cloud160as shown inFIG.1, may be used for performing or partly performing the methods herein.

The above described problem is addressed in a number of embodiments, some of which may be seen as alternatives, while some may be used in combination.

FIG.2shows example embodiments of a method performed by the network node130for restoring an SMS service in a connection between the UE120and the communications network102, and will now be described with reference to a flowchart depicted inFIG.2.

In an example scenario in the connection used for an ongoing SMS service, the UE120is attached to the communications network102with EPS attach and SMS only, via the radio network node110, the VLR MSC140and the network node130.

As mentioned above, the network node130may be an MME and the UE120may be an IoT device.

The method comprises the following actions, which actions may be taken in any suitable order.

The network node130receives information that indicates a restart of the VLR MSC140in the connection. This may e.g. be a VLR failure. A restart of the VLR MSC140means that both the MSC and the VLR in the VLR MSC140is restarted, or only the MSC but not the VLR in the VLR MSC140is restarted, or not the MSC but the VLR in the VLR MSC140is restarted.

This means that the ongoing SMS service needs to be restored, since the communication between the VLR MSC140and the network node130MME is based on the related SGs association, so once the MSC VLR140restart happens, then it will lose all related context for this UE120, which means that the MSC VLR140is no longer able to handle any further SMS service for the UE120at all.

When the network node130receives the information indicating a restart of the VLR MSC140in the connection, it sends an indication to the radio network node110. This indication is to trigger the UE120to send a TAU request with SMS only. The TAU request with SMS only will e.g. be triggered to be sent from the UE120to the network node130. This is performed to be able to restore the ongoing SMS service for the reason of the restart of the VLR MSC140in the connection.

The sending of the indication to the radio network node110, to trigger the UE120to send a TAU request with SMS only, may be performed by sending the indication in a UE Context Release Command message to the radio network node110.

According to some example embodiments herein, a new cause code in a UE Context Release Command is introduced to trigger the UE to perform TAU with SMS only. Thus, the indication in the UE Context Release Command message to the radio network node110may be represented by a cause code.

The network node130receives the TAU request with SMS only, triggered by the UE120according to the indication sent to the radio network node110.

The network node130then restores the SMS service based on information in the TAU request with SMS only, received from the UE120. If the association has to be established due to “VLR-Reliable” Mobility Management (MM) context variable is “false” or if the mapped LA from TA, included in the TAU request sent from UE, is changed, the new MME will send a Location Update Request to the MSC/VLR.

The restoring of the SMS service may be performed by re-establishing SGs association to the VLR MSC140based on the TAU request with SMS only, received from the UE120. This is since once TAU is received; the network node130MME can re-establish the SGs association as the “VLR-Reliable” Mobility Management (MM) context variable to “false”.

FIG.3shows example embodiments of a method performed by the UE120for assisting the network node130in restoring a SMS service in a connection between the UE120and the communications network100, and will now be described with reference to the flowchart depicted inFIG.3. In the example scenario as also mentioned above, in the connection used for the ongoing SMS service, the UE120is attached to the communications network102with EPS attach and SMS only, via the radio network node110, the VLR MSC140and the network node130.

As mentioned above, the network node130may be an MME and the UE120may be an IoT device.

The method comprises the following actions, which actions may be taken in any suitable order.

When a restart of the VLR MSC140in the connection is required, the UE120receives an indication from the radio network node110. The indication indicates to the UE120, to send a TAU request with SMS only. The network node130has sent the indication to the radio network node110and the radio network node110has then sent to the UE120, the indication to send the TAU request with SMS only. This may e.g. be sent in an RRCConnectionRelease with a new cause code, which is to let the radio network node110notify UE120to do a TAU.

The UE120then assists the network node130by sending to the network node130, a TAU request with SMS only according to the received indication. This enables the network node130to restore the SMS service based on information in the TAU request with SMS only. This is performed as described above.

FIG.4is a sequence diagram depicting an example of MME triggered TAU for SMS over SGs restoration. In this example the network node is represented by an MME and is referred to as the MME130.400. The UE120attaches to the communications network102with EPS attach and only.401. By some reason, a restart of the MSC VLR140occurs.402. The MME140is informed about the restart of the MSC VLR140, e.g. in a SGsAP-RESET-INDICATION message from the MSC VLR140to the MME130. The restart of the MSC VLR140means that SGsAP need to be reset and the SMS service need to be restored since after such a restart, the MSC VLR140had lost all related SGs association with the MME130, so there is no way to handle any services over SGs anymore. This action is related to Action201above.403. The MME130replies to the MSC VLR140that the information is understood e.g. in a SGsAP-RESET-ACK message. The MME130will now take actions to reestablish the SGsAP and restore the SMS service.404. The MME130marks VLR-Reliable in Mobility Management (MM) context to false for all impacted UE's including the UE120, which is used for the MME130to decide whether to re-establish the SGs association, once any uplink signaling from the UE120is received later. An MM context e.g. comprises security related information as well as other parameters such as IMSI.405. If the MSC VLR140supports restoration of data in VLR, and there is MT SMS coming, then MSC VLR140may send an SGsAP-PAGING-REQUEST message to the network node110. This is to inform the MME130that there is MT SMS for the related UE120, so the MME130will anyway try to page the UE120if it is ECM_IDLE.It should be noted that the MME130may also decide to trigger TAU, for all impacted UEs such as NB-IoT devices to restore SMS over SGs, one by one. If the UE120is idle, then MME130will send Paging first.406. The UE120then sends a Service Request message to the MME130. This is taken as a paging response by the UE120, when it received Paging from the radio network node110.407. When the service request from the UE120is received by the MME130, the MME130sends a UE Context Release Command message to the radio network node110comprising an indication to trigger the UE120to send a TAU request with SMS only.Upon receiving this indication, the radio network node110may e.g. send a special cause code in RRCConnectionRelease message to the UE120which is to notify UE120to do a TAU.The indication may be represented by the special cause code e.g. referred to as SMS restoration TAU required, e.g. in a RRCConnectionRelease message. As an alternative, the cause code may be adjusted and/or extended as configuration update TAU required” for future usage, since “VLR reliable” is “false” in the MME130. This action is related to Action202above.408. The radio network node110responds with a UE Context Release Complete message to the MME130. This is performed upon reception of the UE CONTEXT RELEASE COMMAND message, the radio network node110shall release all related signalling and user data transport resources and reply with the UE CONTEXT RELEASE COMPLETE message.409. Based on the RRCConnectionRelease with a specified cause code from the radio network node110, the UE120is triggered to send to the MME130a TAU request with SMS only message. This action is related to Action203above.410. The MME130then restores the SMS service based on information in the TAU request with SMS only, received from the UE120by sending a SGsAP-LOCATION-UPDATE-REQUEST message to the MSC VLR140to reestablish SGs association. Reestablish SGs association is performed by the Location Update procedure from the MME130to MSC VLR140is to re-establish the SGs association. This action is related to Action204above.411. The MME130receives a SGsAP-LOCATION-UPDATE-ACCEPT message from the MSC VLR140when the SGs association is reestablished. This means that the SMS service has been restored. This is since once SGs association is established, then SMS over SGs can be served.412. When the SGs association is reestablished and the SGsAP-LOCATION-UPDATE-ACCEPT message has been received from the MSC VLR140, the UE120is informed by sending a TAU Accept with SMS only message to the UE120.

Now the SMS service has been restored and Mobile Originated (MO) i.e. originated from by UE120, and Mobile Terminated (MT) i.e. terminated at the UE120, SMS works well again.

In some legacy embodiments, the network node may release the UE context to the base station with a cause code e.g. referred to as “load balancing TAU required” to trigger the UE120to send a TAU request. The radio network node110would then select another network node such as another network node such as MME in a pool to serve the UE120, while in this case, the network node110should trigger a release of the Radio Resource Control (RRC) resource for the UE120. The UE would then send the TAU request successively. Then the new selected network node starts to establish a new SGs association for the UE. The new network node may e.g. be randomly selected, which means the same network node130such as MME130or another new network node such as new MME in the same pool may be selected. So with the new cause code also referred to as specified cause code, the only impact is on base station and the network node such as the MME, but it would not impact the UE side.

To perform the method actions above, the network node130is configured to restore an SMS service in a connection between a UE120and the communications network102. The network node130may comprise an arrangement depicted inFIGS.5aand5b. As mentioned above, the UE120is adapted to be attached to the communications network102with EPS attach and SMS only, via a radio network node110, the VLR140and the network node130.

In some embodiments, any one or more out of: The network node130is adapted to be an MME, and the UE120is adapted to be an IoT device.

The network node130may comprise an input and output interface500configured to communicate with network nodes such as the network node110and the UE120. The input and output interface may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).

The network node130may further be configured to, e.g. by means of a receiving unit510in the network node130, receive information indicating a restart of the VLR MSC140in the connection.

The network node130may further be configured to, e.g. by means of the receiving unit510in the network node130, receive the TAU request with SMS only, adapted to be triggered by the UE120according to the indication sent to the radio network node110.

The network node130may further be configured to, e.g. by means of a sending unit520in the network node130, when receiving information indicating a restart of the VLR MSC140in the connection, send to the radio network node110, an indication to trigger the UE120to send a TAU request with SMS only.

In some embodiments, the network node130is further configured to e.g. by means of a sending unit520in the network node130, send to the radio network node110, the indication to trigger the UE120to send a TAU request with SMS only, by sending the indication in a UE Context Release Command message to the radio network node110.

In some embodiments, the indication in the UE Context Release Command message to the radio network node110is adapted to be represented by a cause code.

The network node130may further be configured to, e.g. by means of a restoring unit530in the network node130, restore the SMS service based on information in the TAU request with SMS only, adapted to be received from the UE120.

In some embodiments, the network node130is further configured to, e.g. by means of the restoring unit530in the network node130, restore the SMS service by re-establishing SGs association to the VLR MSC140based on the TAU request with SMS only, adapted to be received from the UE120.

The embodiments herein may be implemented through a processor or one or more processors, such as the processor540of a processing circuitry in the the network node130depicted inFIG.5a, together with respective computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the network node130. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the network node130.

The network node130may further comprise a memory550comprising one or more memory units. The memory550comprises instructions executable by the processor in network node130. The memory550is arranged to be used to store e.g. information, indications, cause codes, data, configurations, and applications to perform the methods herein when being executed in the network node130.

In some embodiments, a computer program560comprises instructions, which when executed by the respective at least one processor540, cause the at least one processor540of the network node130to perform the actions above.

In some embodiments, a carrier570comprises the respective computer program560, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

To perform the method actions above, the UE120is configured to assist the network node130in restoring an SMS service in a connection between the UE120and the communications network102. The UE120may comprise an arrangement depicted inFIGS.6aand6b. As mentioned above, the UE120is adapted to be attached to the communications network102with EPS attach and SMS only, via the radio network node110, a VLR MSC140and the network node130.

In some embodiments, any one or more out of: The network node130is adapted to be a MME, and the UE120is adapted to be an IoT device.

The UE120may comprise an input and output interface600configured to communicate with network nodes such as the network node110and the network node130. The input and output interface may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).

The UE120is configured to, e.g. by means of a receiving unit610in the UE120, when a restart of the VLR MSC140in the connection is required, receive from the radio network node110, an indication to the UE120, to send a TAU request with SMS only.

The UE120is further configured to, e.g. by means of a assisting unit620in the UE120, assist the network node130by sending to the network node130a TAU request with SMS only according to the received indication, enabling the network node130to restore the SMS service based on information in the TAU request with SMS only.

The embodiments herein may be implemented through a respective processor or one or more processors, such as the processor630of a processing circuitry in the UE120depicted inFIG.6a, together with respective computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the UE120. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the UE120.

The UE120may further comprise a memory640comprising one or more memory units. The memory1050comprises instructions executable by the processor in UE120. The memory640is arranged to be used to store e.g. information, indications, cause codes, data, configurations, and applications to perform the methods herein when being executed in the UE120.

In some embodiments, a computer program650comprises instructions, which when executed by the respective at least one processor630, cause the at least one processor of the UE120to perform the actions above.

In some embodiments, a respective carrier660comprises the respective computer program650, wherein the carrier660is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

The communication system3300further includes the UE3330already referred to. Its hardware3335may include a radio interface3337configured to set up and maintain a wireless connection3370with a base station serving a coverage area in which the UE3330is currently located. The hardware3335of the UE3330further includes processing circuitry3338, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE3330further comprises software3331, which is stored in or accessible by the UE3330and executable by the processing circuitry3338. The software3331includes a client application3332. The client application3332may be operable to provide a service to a human or non-human user via the UE3330, with the support of the host computer3310. In the host computer3310, an executing host application3312may communicate with the executing client application3332via the OTT connection3350terminating at the UE3330and the host computer3310. In providing the service to the user, the client application3332may receive request data from the host application3312and provide user data in response to the request data. The OTT connection3350may transfer both the request data and the user data. The client application3332may interact with the user to generate the user data that it provides. It is noted that the host computer3310, base station3320and UE3330illustrated inFIG.8may be identical to the host computer3230, one of the base stations3212a,3212b,3212cand one of the UEs3291,3292ofFIG.7, respectively. This is to say, the inner workings of these entities may be as shown inFIG.8and independently, the surrounding network topology may be that ofFIG.7.

The wireless connection3370between the UE3330and the base station3320is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE3330using the OTT connection3350, in which the wireless connection3370forms the last segment. More precisely, the teachings of these embodiments may improve the [select the applicable RAN effect: data rate, latency, power consumption] and thereby provide benefits such as [select the applicable corresponding effect on the OTT service: reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime].

The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used.