Patent Description:
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 <NUM>. 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 (<NUM>) 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 (<NUM>) network also referred to as <NUM> 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 <NUM> networks. In general, in E-UTRAN/LTE the functions of a <NUM> 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.

Multi-antenna techniques may significantly increase the data rates and reliability of a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO.

<CIT> relates to cellular communication systems, and more particularly to restoration of user equipment control in the presence of communication link failure between a network node that provides control of packet switched connections and a network node that provides control of circuit switched connections.

3GPP TS <NUM> V15. <NUM> discloses procedures to be followed in case of VLR failure.

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

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 <NUM> 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 <NUM> 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 <NUM> or CS/PS mode <NUM> 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 <NUM> or CS/PS mode <NUM> 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 NB-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, NB-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-loT 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 NB-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-loT 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.

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 <NUM> 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. <NUM> chapter <NUM>.

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

For UEs being NB-loT 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 NB-loT 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, a message comprising an indication to trigger the UE to send a Tracking Area Update, TAU, request with SMS only, wherein the message comprises a cause code representing the indication.

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 a message comprising an indication from the radio network node. The indication indicates to the UE, to send a Tracking Area Update, TAU, request with SMS only, wherein the message comprises a cause code representing the indication. The UE then assists the network node <NUM> by 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:.

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:.

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.

Embodiments provide SMS service restoration for UEs such as NB-loT 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 loT devices. This may be for some loT 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> is a schematic overview depicting a wireless communications network <NUM>. The wireless communications network <NUM> comprises one or more RANs and one or more CNs. The wireless communications network <NUM> may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, <NUM>, 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 <NUM> 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 network <NUM>, wireless devices e.g. one or more UEs <NUM> also 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 network <NUM> comprises a radio network node <NUM> providing radio coverage in one or more cells, such as a cell <NUM>, which may also be referred to as a beam or a beam group of beams. The radio network node <NUM> may 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 node <NUM> depending e.g. on the first radio access technology and terminology used. The radio network node <NUM> may be referred to as a serving radio network node and communicates with the UE <NUM> with Downlink (DL) transmissions to the UE <NUM> and Uplink (UL) transmissions from the UE <NUM>.

A number of network nodes operate in the CN such as a EPC. the network node <NUM> which may be an MME, also referred to as MME <NUM>. 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) <NUM> through 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 VLR <NUM>. The MSC VLR <NUM> is an MSC that is associated to a VLR. The MSC and the VLR in the MSC VLR <NUM> are 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 SGW <NUM>. A function of an SGW is routing and forwarding of user data packets related to the UE <NUM> to and from a network such as the communications network <NUM>, which e.g. may be the internet or a local area network or any network.

Methods herein may be performed by the network node <NUM>. As an alternative, a Distributed Node (DN) and functionality, e.g. comprised in a cloud <NUM> as shown in <FIG>, 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> shows example embodiments of a method performed by the network node <NUM> for restoring an SMS service in a connection between the UE <NUM> and the communications network <NUM>, and will now be described with reference to a flowchart depicted in <FIG>.

In an example scenario in the connection used for an ongoing SMS service, the UE <NUM> is attached to the communications network <NUM> with EPS attach and SMS only, via the radio network node <NUM>, the VLR MSC <NUM> and the network node <NUM>.

As mentioned above, the network node <NUM> may be an MME and the UE <NUM> may be an loT device.

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

The network node <NUM> receives information that indicates a restart of the VLR MSC <NUM> in the connection. This may e.g. be a VLR failure. A restart of the VLR MSC <NUM> means that both the MSC and the VLR in the VLR MSC <NUM> is restarted, or only the MSC but not the VLR in the VLR MSC <NUM> is restarted, or not the MSC but the VLR in the VLR MSC <NUM> is restarted.

This means that the ongoing SMS service needs to be restored, since the communication between the VLR MSC <NUM> and the network node <NUM> MME is based on the related SGs association, so once the MSC VLR <NUM> restart happens, then it will lose all related context for this UE <NUM>, which means that the MSC VLR <NUM> is no longer able to handle any further SMS service for the UE <NUM> at all.

When the network node <NUM> receives the information indicating a restart of the VLR MSC <NUM> in the connection, it sends an indication to the radio network node <NUM>. This indication is to trigger the UE <NUM> to send a TAU request with SMS only. The TAU request with SMS only will e.g. be triggered to be sent from the UE <NUM> to the network node <NUM>. This is performed to be able to restore the ongoing SMS service for the reason of the restart of the VLR MSC <NUM> in the connection.

The sending of the indication to the radio network node <NUM>, to trigger the UE <NUM> to 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 node <NUM>.

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 node <NUM> may be represented by a cause code.

The network node <NUM> receives the TAU request with SMS only, triggered by the UE <NUM> according to the indication sent to the radio network node <NUM>.

The network node <NUM> then restores the SMS service based on information in the TAU request with SMS only, received from the UE <NUM>. 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 MSC <NUM> based on the TAU request with SMS only, received from the UE <NUM>. This is since once TAU is received; the network node <NUM> MME can re-establish the SGs association as the "VLR-Reliable" Mobility Management (MM) context variable to "false".

<FIG> shows example embodiments of a method performed by the UE <NUM> for assisting the network node <NUM> in restoring a SMS service in a connection between the UE <NUM> and the communications network <NUM>, and will now be described with reference to the flowchart depicted in <FIG>. In the example scenario as also mentioned above, in the connection used for the ongoing SMS service, the UE <NUM> is attached to the communications network <NUM> with EPS attach and SMS only, via the radio network node <NUM>, the VLR MSC <NUM> and the network node <NUM>.

As mentioned above, the network node <NUM> may be an MME and the UE <NUM> may be an IoT device.

When a restart of the VLR MSC <NUM> in the connection is required, the UE <NUM> receives an indication from the radio network node <NUM>. The indication indicates to the UE <NUM>, to send a TAU request with SMS only. The network node <NUM> has sent the indication to the radio network node <NUM> and the radio network node <NUM> has then sent to the UE <NUM>, 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 node <NUM> notify UE <NUM> to do a TAU.

The UE <NUM> then assists the network node <NUM> by sending to the network node <NUM>, a TAU request with SMS only according to the received indication. This enables the network node <NUM> to restore the SMS service based on information in the TAU request with SMS only. This is performed as described above.

<FIG> is 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 MME <NUM>.

Now the SMS service has been restored and Mobile Originated (MO) i.e. originated from by UE <NUM>, and Mobile Terminated (MT) i.e. terminated at the UE <NUM>, 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 UE <NUM> to send a TAU request. The radio network node <NUM> would then select another network node such as another network node such as MME in a pool to serve the UE <NUM>, while in this case, the network node <NUM> should trigger a release of the Radio Resource Control (RRC) resource for the UE <NUM>. 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 node <NUM> such as MME <NUM> or 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 node <NUM> is configured to restore an SMS service in a connection between a UE <NUM> and the communications network <NUM>. The network node <NUM> may comprise an arrangement depicted in <FIG>. As mentioned above, the UE <NUM> is adapted to be attached to the communications network <NUM> with EPS attach and SMS only, via a radio network node <NUM>, the VLR <NUM> and the network node <NUM>.

In some embodiments, any one or more out of: The network node <NUM> is adapted to be an MME, and the UE <NUM> is adapted to be an IoT device.

The network node <NUM> may comprise an input and output interface <NUM> configured to communicate with network nodes such as the network node <NUM> and the UE <NUM>. The input and output interface may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).

The network node <NUM> may further be configured to, e.g. by means of a receiving unit <NUM> in the network node <NUM>, receive information indicating a restart of the VLR MSC <NUM> in the connection.

The network node <NUM> may further be configured to, e.g. by means of the receiving unit <NUM> in the network node <NUM>, receive the TAU request with SMS only, adapted to be triggered by the UE <NUM> according to the indication sent to the radio network node <NUM>.

The network node <NUM> may further be configured to, e.g. by means of a sending unit <NUM> in the network node <NUM>, when receiving information indicating a restart of the VLR MSC <NUM> in the connection, send to the radio network node <NUM>, an indication to trigger the UE <NUM> to send a TAU request with SMS only.

In some embodiments, the network node <NUM> is further configured to e.g. by means of a sending unit <NUM> in the network node <NUM>, send to the radio network node <NUM>, the indication to trigger the UE <NUM> to send a TAU request with SMS only, by sending the indication in a UE Context Release Command message to the radio network node <NUM>.

In some embodiments, the indication in the UE Context Release Command message to the radio network node <NUM> is adapted to be represented by a cause code.

The network node <NUM> may further be configured to, e.g. by means of a restoring unit <NUM> in the network node <NUM>, restore the SMS service based on information in the TAU request with SMS only, adapted to be received from the UE <NUM>.

In some embodiments, the network node <NUM> is further configured to, e.g. by means of the restoring unit <NUM> in the network node <NUM>, restore the SMS service by re-establishing SGs association to the VLR MSC <NUM> based on the TAU request with SMS only, adapted to be received from the UE <NUM>.

The embodiments herein may be implemented through a processor or one or more processors, such as the processor <NUM> of a processing circuitry in the the network node <NUM> depicted in <FIG>, 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 node <NUM>. 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 node <NUM>.

The network node <NUM> may further comprise a memory <NUM> comprising one or more memory units. The memory <NUM> comprises instructions executable by the processor in network node <NUM>. The memory <NUM> is 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 node <NUM>.

In some embodiments, a computer program <NUM> comprises instructions, which when executed by the respective at least one processor <NUM>, cause the at least one processor <NUM> of the network node <NUM> to perform the actions above.

In some embodiments, a carrier <NUM> comprises the respective computer program <NUM>, 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.

Those skilled in the art will appreciate that the units in the network node <NUM> described above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the network node <NUM>, that when executed by the respective one or more processors such as the processor described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).

To perform the method actions above, the UE <NUM> is configured to assist the network node <NUM> in restoring an SMS service in a connection between the UE <NUM> and the communications network <NUM>. The UE <NUM> may comprise an arrangement depicted in <FIG>. As mentioned above, the UE <NUM> is adapted to be attached to the communications network <NUM> with EPS attach and SMS only, via the radio network node <NUM>, a VLR MSC <NUM> and the network node <NUM>.

In some embodiments, any one or more out of: The network node <NUM> is adapted to be a MME, and the UE <NUM> is adapted to be an IoT device.

The UE <NUM> may comprise an input and output interface <NUM> configured to communicate with network nodes such as the network node <NUM> and the network node <NUM>. The input and output interface may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).

The UE <NUM> is configured to, e.g. by means of a receiving unit <NUM> in the UE <NUM>, when a restart of the VLR MSC <NUM> in the connection is required, receive from the radio network node <NUM>, an indication to the UE <NUM>, to send a TAU request with SMS only.

The UE <NUM> is further configured to, e.g. by means of a assisting unit <NUM> in the UE <NUM>, assist the network node <NUM> by sending to the network node <NUM> a TAU request with SMS only according to the received indication, enabling the network node <NUM> to 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 processor <NUM> of a processing circuitry in the UE <NUM> depicted in <FIG>, 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 UE <NUM>. 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 UE <NUM>.

The UE <NUM> may further comprise a memory <NUM> comprising one or more memory units. The memory <NUM> comprises instructions executable by the processor in UE <NUM>. The memory <NUM> is 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 UE <NUM>.

In some embodiments, a computer program <NUM> comprises instructions, which when executed by the respective at least one processor <NUM>, cause the at least one processor of the UE <NUM> to perform the actions above.

In some embodiments, a respective carrier <NUM> comprises the respective computer program <NUM>, wherein the carrier <NUM> 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.

Those skilled in the art will appreciate that the units in the UE <NUM> described above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the UE <NUM>, that when executed by the respective one or more processors such as the processors described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).

With reference to <FIG>, in accordance with an embodiment, a communication system includes a telecommunication network <NUM>, such as a 3GPP-type cellular network, which comprises an access network <NUM>, such as a radio access network, and a core network <NUM>. The access network <NUM> comprises a plurality of base stations 3212a, 3212b, 3212c, such as AP STAs NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 3213a, 3213b, 3213c. Each base station 3212a, 3212b, 3212c is connectable to the core network <NUM> over a wired or wireless connection <NUM>. A first user equipment (UE) such as a Non-AP STA <NUM> located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE <NUM> such as a Non-AP STA in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a.

The wireless connection <NUM> between the UE <NUM> and the base station <NUM> is 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 UE <NUM> using the OTT connection <NUM>, in which the wireless connection <NUM> forms 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 communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to <FIG> and <FIG>.

The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to <FIG> and <FIG>.

The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to <FIG> and <FIG>.

The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to <FIG> and <FIG>.

When using the word "comprise" or "comprising" it shall be interpreted as non-limiting, i.e. meaning "consist at least of".

Claim 1:
A method performed by a network node (<NUM>) for restoring a Short Message Service, SMS, service in a connection between a User Equipment, UE, (<NUM>) and a communications network (<NUM>), which UE (<NUM>) is attached to the communications network (<NUM>) with Evolved Packet System, EPS, attach and SMS only, via a radio network node (<NUM>), a Visitor Location Register, VLR, Mobile Switching Centre, MSC, (<NUM>) and the network node (<NUM>), the method comprising:
when receiving (<NUM>, <NUM>) information indicating a restart of the VLR MSC (<NUM>) in the connection, sending (<NUM>, <NUM>) to the radio network node (<NUM>), a message comprising an indication to trigger the UE (<NUM>) to send a Tracking Area Update, TAU, request with SMS only, wherein the message comprises a cause code representing the indication,
receiving (<NUM>, <NUM>) the TAU request with SMS only, triggered by the UE (<NUM>) according to the indication sent to the radio network node (<NUM>), and
restoring (<NUM>, <NUM>) the SMS service based on information in the TAU request with SMS only, received from the UE (<NUM>).