Patent Description:
Examples of mobile or wireless telecommunication systems may include the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), LTE-Advanced (LTE-A), MulteFire, LTE-A Pro, and/or fifth generation (<NUM>) radio access technology or new radio (NR) access technology. Fifth generation (<NUM>) wireless systems refer to the next generation (NG) of radio systems and network architecture. <NUM> is mostly built on a new radio (NR), but the <NUM> (or NG) network can also build on E-UTRAN radio. It is estimated that NR will provide bitrates on the order of <NUM>-<NUM> Gbit/s or higher, and will support at least enhanced mobile broadband (eMBB) and ultra-reliable low-latency-communication (URLLC) as well as massive machine type communication (mMTC). NR is expected to deliver extreme broadband and ultra-robust, low latency connectivity and massive networking to support the Internet of Things (IoT). With IoT and machine-to-machine (M2M) communication becoming more widespread, there will be a growing need for networks that meet the needs of lower power, low data rate, and long battery life. It is noted that, in <NUM>, the nodes that can provide radio access functionality to a user equipment (i.e., similar to Node B in UTRAN or eNB in LTE) are named gNB when built on NR radio and named NG-eNB when built on E-UTRAN radio. Document <CIT> discusses the transfer of back-haul characteristics such as available bandwidth and reliability from a secondary node to a master node.

SUMMARY The invention is defined by the independent claims. Advantageous embodiments of the invention are given in the dependent claims.

According some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims. The embodiments that do not fall under the scope of the claims are to be interpreted as examples useful for understanding the disclosure.

It will be readily understood that the components of certain example embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. The following is a detailed description of some example embodiments of systems, methods, apparatuses, and computer program products for preventing data outage for user equipment (UE) during Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network (E-UTRAN) New Radio Dual Connectivity (EN-DC).

For example, the usage of the phrases "certain embodiments," "an example embodiment," "some embodiments," or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment. Thus, appearances of the phrases "in certain embodiments," "an example embodiment," "in some embodiments," "in other embodiments," or other similar language, throughout this specification do not necessarily refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments. Additionally, "MeNB" may be interchangeably used as "master node" or "master node/MeNB", or individually used as "MeNB" and "master node". "MeNB" may also have an equivalent meaning as "master node". Further "en-gNB/SgNB" may be interchangeably used as "secondary node/en-gNB/SgNB", or individually used as "secondary node", "en-gNB" or "SgNB". Additionally, "secondary node", "en-gNB", and SgNB may have an equivalent meaning. Furthermore, "S1-U" may be interchangeably used as "S1-U", "NG-U", or "S1-U/NG-U", or individually used as "S1-U", "NG-U", or "S1-U/NG-U". Each of "S1-U" and "NG-U" may also have an equivalent meaning.

In some cases, general packet radio service (GPRS) tunneling protocol for user plane (GTP-U) failure may arise due to switch/router upgradation, or intermediate hardware failure (switch/router) in an IP network, which sometimes need operator intervention to restore it back to stock. <NUM>rd Generation Partnership Project (3GPP) describes GTP-U path failure handling at the access network and core network, respectively. For example, 3GPP describes, for path failure, a node detecting the GTP-U path failure with its peer may notify the upper layer of the path failure so that the user equipment (UE) can be disconnected from the network, and can retry the attach procedure. 3GPP also describes path failure in the serving gateway (SGW) and the mobility management entity (MME). For example, the SGW may detect the GTP-U path failure with its peer and notify the MME. The MME may in turn allocate another SGW for the bearer or release the bearer. Furthermore, the MME may derive the S1-U/NG-U path information (e.g., the eNB fully qualified tunnel endpoint identifier (F-TEID) and the SGW F-TEID) from the UE context, and mark it as failed. In addition, the MME may store such information for a configurable period. The MME may also avoid selecting the SGW with a failed S1-U/NG-U path towards the eNB for subsequent packet data network (PDN) connection establishment procedures and mobility procedures with SGW relocation.

<FIG> illustrates an example of a successful UE data connectivity during an EN-DC procedure, and <FIG> illustrates an example of data outage at the UE due to S1-U/NG-U path failure during an EN-DC procedure. In certain cases, during an EN-DC procedure, the MME may select the SGW based on the path status between the master node/MeNB and the SGW. However, in other cases, the MME may not consider the path status between the secondary node/en-gNB/SgNB and the SGW since the secondary node/en-gNB/SgNB selection logic resides at the master node/MeNB. If in case the GTP-U path status between the secondary node/en-gNB/SgNB and the SGW is not reachable, the UE may still successfully attach to the network, and as a result, no radio link failures are detected. In such a case, the attached UE may experience data outage until the GTP-U path is restored. In addition, the radio resource control (RRC) re-establishment or re-attach procedure may result in data outage if the GTP-U path is not restored as the same entities may be allocated again.

According to the invention, when the GTP-U path failure is identified by the secondary node/en-gNB/SgNB, the status is indicated to the master node/MeNB. Based on the received path status, the master node/MeNB may avoid the selection of such paths (e.g., en-gNB SGW pair) experiencing the path failure for a secondary gNodeB (SgNB) addition procedure. As such, the UE with dual connectivity capability may not have a secondary cell group (SCG) bearer established involving the path having the failure. Accordingly, it may be possible to avoid experiencing data outage due to the broken link.

In certain example embodiments, to indicate the status of the path failure, the secondary node/en-gNB/SgNB may adapt the existing "gNB Status Indication Message" to update the peer master node/MeNB. Alternatively, in other example embodiments, the secondary node/en-gNB/SgNB may introduce a new message to indicate the status to all the master nodes/MeNBs to which it has X2 setup successfully. According to certain example embodiments, by maintaining the status of the paths between the secondary node/en-gNB/SgNB and SGWs, the master node/MeNB can select an alternative secondary node/en-gNB/SgNB that does not have any connectivity issues with the SGW provided by the MME. According to other example embodiments, the master node/MeNB may request for a different SGW from the MME when there are no alternate secondary nodes/en-gNBs/SgNBs available.

<FIG> illustrates an example of a network topology and S1-U/NG-U path status table at the master node/MeNB, according to certain example embodiments. In particular, <FIG> illustrates an example of a network deployment where the eNB, secondary node/en-gNB/SgNB, and SGW are connected via an IP network. According to certain example embodiments, the master node/MeNB may maintain connectivity status information as shown in table <NUM> of <FIG>. Specifically, the table <NUM> includes the S <NUM>-U/NG-U path status for all the peer secondary nodes/en-gNBs/SgNBs of the master node/MeNB.

In certain example embodiments, the master node/MeNB may receive the status of the paths from the secondary node/en-gNB/SgNB peers through various mechanisms. For example, in some example embodiments, the master node/MeNB may receive status of the paths from secondary node/en-gNB/SgNB peers via an adapted gNB status indication message. In other example embodiments, the master node/MeNB may receive status of the paths from secondary node/en-gNB/SgNB peers via a GTP-U status indication message, which may be a unicast message or a broadcast message.

According to certain example embodiments, the master node/MeNB may include S1-U/NG-U path status as an additional criteria while selecting a secondary node/en-gNB/SgNB so that the secondary node/en-gNB/SgNB selected for SCG bearer may not cause data outage at the UE (see <FIG> with secondary node/en-gNB/SgNB selection logic with additional selection criteria). According to other example embodiments, the master node/MeNB may include S1-U/NG-U path status as additional criteria for rejecting an E-UTRAN radio access bearer (eRAB) establishment with a suitable cause for the MME to allocate another available SGW for the S1-U/NG-U bearer establishment to provide NR data throughput. In this example, the rejection logic is illustrated in the example of <FIG> discussed herein.

<FIG> illustrates an example of an secondary node/en-gNB/SgNB selection logic with additional selection criteria, according to certain example embodiments. As illustrated in <FIG>, at <NUM>, the master node/MeNB may trigger a secondary node/en-gNB/SgNB selection for an EN-DC procedure based on, for example, UE measurement information. At <NUM>, the master node/MeNB may retrieve S1-U/NG-U status (i.e., GTP-U path status, whether there is a failure) from the information table <NUM> illustrated in <FIG>. At <NUM>, the master node/MeNB may determine whether the S1-U/NG-U path status of the secondary node/en-gNB/SgNB has been obtained. If the S1-U/NG-U path status has been obtained and is determined as having an "available" status, then, at <NUM>, the master node/MeNB may initiate SgNB addition procedure to establish a connection between the MeNB and secondary node/en-gNB/SgNB. However, if it is determined that the S1-U/NG-U path status has an "unavailable" status, then, at <NUM>, the master node/MeNB may determine whether an alternative secondary node/en-gNB/SgNB is available for the UE. If no, at <NUM>, the master node/MeNB may request the MME to change the SGW or continue with the master cell group (MCG) bearer path. On the other hand, if an alternative secondary node/en-gNB/SgNB is available for the UE, the procedure may return to <NUM> where the master node/MeNB may retrieve the S1-U/NG-U path status of the alternative secondary node/en-gNB/SgNB from the table.

<FIG> illustrates an example gNB status indication procedure, according to certain example embodiments. At <NUM>, the secondary node/en-gNB/SgNB may send a gNB status indication message to the master node/MeNB. According to certain example embodiments, the gNB status indication message may include gNB overload information and/or GTP-U path status information. Further, Table <NUM> lists several examples of the gNB status indication and their contents.

Table <NUM> lists certain examples of the S <NUM>-U/NG-U path information. According to certain example embodiments, this information element (IE) may provide information on the S <NUM>-U/NG-U supervision status. Further, Table <NUM> lists certain examples of the S <NUM>-U/NG-U interface events. According to certain example embodiments, the events upon which S <NUM>-U/NG-U path status may be communicated to the master node/MeNB may include those listed in Table <NUM>. In addition, Table <NUM> lists certain examples of GTP-U status indication information. According to certain example embodiments, the GTP-U status indication information may be sent as a message by the secondary node/en-gNB/SgNB to indicate to the eNB its status of S1-U/NG-U path.

In certain example embodiments, on occurrence of events (see Table <NUM>) over the S1-U/NG-U interface, the secondary node/en-gNB/SgNB may send a gNB status indication message (see Table <NUM>) including optional S1-U/NG-U path status information IE (see Table <NUM>) to indicate the S1-U/NG-U path status. Alternatively, in other example embodiments, the S1-U/NG-U status information may be communicated via a new message GTP-U status indication message (see Table <NUM>).

<FIG> illustrates an example flow diagram of a method, according to certain example embodiments. In an example embodiment, the method of <FIG> may be performed by a network entity, network node, or a group of multiple network elements in a 3GPP system, such as LTE or <NUM>-NR. For instance, in an example embodiment, the method of <FIG> may be performed by a secondary node/en-gNB/SgNB, for instance similar to apparatus <NUM> illustrated in <FIG>.

According to certain example embodiments, the method of <FIG> may include, at <NUM>, identifying a status of a user plane path between a first network node and a gateway node in a communication network. The method may also include, at <NUM>, transmitting, to a second network node, the status of the user plane path. The method may further include, at <NUM>, setting up or disconnecting a connection between the first network node and the second network node during a dual connectivity operation.

According to certain example embodiments, the status of the user plane path may include a failure status or recovered status. According to other example embodiments, the status may be transmitted to the second network node via a network node status indication message, a general packet radio service tunneling protocol for user plane (GTP-U) status indication message, or any other message between the first network node and the second network node. According to further example embodiments, the GTP-U status indication message may be a unicast message or a broadcast message.

In certain example embodiments, the network node status indication message may include GTP-U path status information along with overload information. In other example embodiments, the network node status indication message may include S1 user plane interface path status information to indicate an S1 user plane interface path status. In some example embodiments, the S1 user plane interface path status information may be communicated via a new GTP-U status indication message.

<FIG> illustrates an example flow diagram of another method, according to certain example embodiments. In an example embodiment, the method of <FIG> may be performed by a network entity, network node, or a group of multiple network elements in a 3GPP system, such as LTE or <NUM>-NR. For instance, in an example embodiment, the method of <FIG> may be performed by a master node/MeNB, for instance similar to apparatus <NUM> illustrated in <FIG>.

According to certain example embodiments, the method of <FIG> may include, at <NUM>, triggering a first network node selection in a dual connectivity operation. The method may also include, at <NUM>, retrieving a status of a user plane path of the first network node. The method may further include, at <NUM>, based on the received status, setting up the dual connectivity operation to establish a dual connectivity connection between a second network node and the first network node, or determining whether an alternate network node is available. The method may further include, at <NUM>, based on the received status, triggering release of the dual connectivity operation to the first network node.

According to certain example embodiments, when it is determined that an alternate network node is not available, the method may also include requesting a mobility management entity for a different gateway node, or continuing a connection with a master cell group bearer path. According to other example embodiments, when it is determined that an alternative network node is available, the method may further include retrieving the status of the user plane path of the alternative network node. According to further example embodiments, the status may be retrieved via a network node status indication message, or a general packet radio service tunneling protocol for user plane (GTP-U) status indication message.

In certain example embodiments, the GTP-U status indication message may be a unicast message or a broadcast message. In some example embodiments, the network node status indication message may include GTP-U path status information along with overload information. In other example embodiments, the network node status indication message may include S1 user plane interface path status information to indicate an S1 user plane interface path status. In further example embodiments, the S1 user plane interface path status information is communicated via a new GTP-U status indication message.

<FIG> illustrates an apparatus <NUM> according to certain example embodiments. In certain example embodiments, apparatus <NUM> may be a node or element in a communications network or associated with such a network, such as a UE, mobile equipment (ME), mobile station, mobile device, stationary device, or other device. In other example embodiments, apparatus <NUM> may be an eNB/gNB.

In some example embodiments, apparatus <NUM> may be configured to operate using one or more radio access technologies, such as GSM, LTE, LTE-A, NR, <NUM>, WLAN, WiFi, NB-IoT, Bluetooth, NFC, MulteFire, and/or any other radio access technologies.

While a single processor <NUM> is shown in <FIG>, multiple processors may be utilized according to other example embodiments. For example, it should be understood that, in certain example embodiments, apparatus <NUM> may include two or more processors that may form a multiprocessor system (e.g., in this case processor <NUM> may represent a multiprocessor) that may support multiprocessing. According to certain example embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

Processor <NUM> may perform functions associated with the operation of apparatus <NUM> including, as some examples, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus <NUM>, including processes illustrated in <FIG>.

In certain example embodiments, apparatus <NUM> may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processor <NUM> and/or apparatus <NUM> to perform any of the methods illustrated in <FIG>.

In some example embodiments, apparatus <NUM> may also include or be coupled to one or more antennas <NUM> for receiving a downlink signal and for transmitting via an uplink from apparatus <NUM>.

In other example embodiments, transceiver <NUM> may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some example embodiments, apparatus <NUM> may include an input and/or output device (I/O device). In certain example embodiments, apparatus <NUM> may further include a user interface, such as a graphical user interface or touchscreen.

In certain example embodiments, memory <NUM> stores software modules that provide functionality when executed by processor <NUM>. According to certain example embodiments, apparatus <NUM> may optionally be configured to communicate with apparatus <NUM> via a wireless or wired communications link <NUM> according to any radio access technology, such as NR.

According to certain example embodiments, processor <NUM> and memory <NUM> may be included in or may form a part of processing circuitry or control circuitry. In addition, in some example embodiments, transceiver <NUM> may be included in or may form a part of transceiving circuitry.

<FIG> illustrates an apparatus <NUM> according to certain example embodiments. In certain example embodiments, the apparatus <NUM> may be a node or element in a communications network or associated with such a network, such as a base station, a Node B, an evolved Node B (eNB), <NUM> Node B or access point, next generation Node B (NG-NB or gNB), master node/MeNB, secondary node/en-gNB/SgNB and/or WLAN access point, associated with a radio access network (RAN), such as an LTE network, <NUM> or NR.

For example, processor <NUM> may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. While a single processor <NUM> is shown in <FIG>, multiple processors may be utilized according to other example embodiments. For example, it should be understood that, in certain example embodiments, apparatus <NUM> may include two or more processors that may form a multiprocessor system (e.g., in this case processor <NUM> may represent a multiprocessor) that may support multiprocessing. In certain example embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

According to certain example embodiments, processor <NUM> may perform functions associated with the operation of apparatus <NUM>, which may include, for example, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus <NUM>, including processes illustrated in <FIG>.

In certain example embodiments, apparatus <NUM> may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processor <NUM> and/or apparatus <NUM> to perform the methods illustrated in <FIG>.

In certain example embodiments, apparatus <NUM> may also include or be coupled to one or more antennas <NUM> for transmitting and receiving signals and/or data to and from apparatus <NUM>. Apparatus <NUM> may further include or be coupled to a transceiver <NUM> configured to transmit and receive information. The transceiver <NUM> may include, for example, a plurality of radio interfaces that may be coupled to the antenna(s) <NUM>. The radio interfaces may correspond to a plurality of radio access technologies including one or more of GSM, NB-IoT, LTE, <NUM>, WLAN, Bluetooth, BT-LE, NFC, radio frequency identifier (RFID), ultrawideband (UWB), MulteFire, and the like. The radio interface may include components, such as filters, converters (for example, digital-to-analog converters and the like), mappers, a Fast Fourier Transform (FFT) module, and the like, to generate symbols for a transmission via one or more downlinks and to receive symbols (for example, via an uplink).

In other example embodiments, transceiver <NUM> may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some example embodiments, apparatus <NUM> may include an input and/or output device (I/O device).

In certain example embodiment, memory <NUM> may store software modules that provide functionality when executed by processor <NUM>.

According to some example embodiments, processor <NUM> and memory <NUM> may be included in or may form a part of processing circuitry or control circuitry. In addition, in some example embodiments, transceiver <NUM> may be included in or may form a part of transceiving circuitry.

As used herein, the term "circuitry" may refer to hardware-only circuitry implementations (e.g., analog and/or digital circuitry), combinations of hardware circuits and software, combinations of analog and/or digital hardware circuits with software/firmware, any portions of hardware processor(s) with software (including digital signal processors) that work together to cause an apparatus (e.g., apparatus <NUM> and <NUM>) to perform various functions, and/or hardware circuit(s) and/or processor(s), or portions thereof, that use software for operation but where the software may not be present when it is not needed for operation.

For instance, in certain example embodiments, apparatus <NUM> may be controlled by memory <NUM> and processor <NUM> to identify a status of a user plane path between the apparatus and a gateway node in a communication network. Apparatus <NUM> may also be controlled by memory <NUM> and processor <NUM> to transmit, to a network node, the status of the user plane path. Apparatus <NUM> may further be controlled by memory <NUM> and processor <NUM> to setup or disconnect a connection between the apparatus and the second network node during a dual connectivity operation.

In other example embodiments, apparatus <NUM> may be controlled by memory <NUM> and processor <NUM> to trigger a first network node selection in a dual connectivity operation. Apparatus <NUM> may also be controlled by memory <NUM> and processor <NUM> to retrieve a status of a user plane path of the first network node. Apparatus <NUM> may further be controlled by memory <NUM> and processor <NUM> to, based on the status, setup the dual connectivity operation to establish a dual connectivity connection between a second network node and the first network node, or determine whether an alternate network node is available. Apparatus <NUM> may also be controlled by memory <NUM> and processor <NUM> to, based on the received status, trigger release of the dual connectivity operation to the first network node.

Certain example embodiments may be directed to an apparatus that includes means for identifying a status of a user plane path between a first network node and a gateway node in a communication network. The apparatus may also include means for transmitting, to a second network node, the node of the user plane path. The apparatus may further include means for setting up or disconnecting a connection between the first network node and the second network node during a dual connectivity operation.

Other example embodiments may be directed to an apparatus that includes means for triggering a network node selection in a dual connectivity operation. The apparatus may also include means for retrieving a status of a user plane path of the network node. The apparatus may further include means for, based on the received status, setting up the dual connectivity operation to establish a dual connectivity connection between the network node and the apparatus, or determining whether an alternate network node is available. The apparatus may also include means for, based on the received status, triggering release of the dual connectivity operation to the network node.

Certain example embodiments described herein provide several technical improvements, enhancements, and /or advantages. In some example embodiments, it may be possible for the master node/MeNB to avoid selection of a GTP-U path experiencing path failure for an SgNB addition procedure. As such, the UE with dual connectivity capability may avoid having an SCG bearer established involving the path with the failure. In addition, the UE would be able to avoid experiencing data outage due to the broken link.

A computer program product not according to the invention as defined in the claims and presented for illustration purposes only is provided and may include one or more computer-executable components which, when the program is run, are configured to carry out some example embodiments. The one or more computer-executable components may be at least one software code or portions of it. Modifications and configurations required for implementing functionality of certain example embodiments may be performed as routine(s), which may be implemented as added or updated software routine(s). Software routine(s) may be downloaded into the apparatus.

As an software or a computer program code or portions of it may be in a source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers may include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. The computer readable medium or computer readable storage medium may be a non-transitory medium.

In other example embodiments, the functionality may be performed by hardware or circuitry included in an apparatus (e.g., apparatus <NUM> or apparatus <NUM>), for example through the use of an application specific integrated circuit (ASIC), a programmable gate array (PGA), a field programmable gate array (FPGA), or any other combination of hardware and software. In yet another example embodiment, the functionality may be implemented as a signal, a non-tangible means that can be carried by an electromagnetic signal downloaded from the Internet or other network.

Claim 1:
A method for a secondary network node, comprising:
identifying a status of a user plane path between the secondary network node and a gateway node in a communication network as failed;
transmitting, to a master network node, the failed status of the user plane path when the failed status is identified; and
disconnecting a connection between the secondary network node and the master network node during a dual connectivity operation.