Method and apparatus for recovering from roaming-related failures - Patents.com

Abstract

A method and system for recovering from a SOR failure is provided, the method being performed by a terminal in a wireless communication system, the method including the steps of detecting a SOR failure in a manual mode during or after registration with a first visitor-public land mobile network (VPLMN), switching from the manual mode to an automatic mode based on a determination that a SOR failure has occurred, and performing a public land mobile network (PLMN) selection procedure to obtain service in a second VPLMN having a higher priority than the first VPLMN.

Description

[Technical field]

[0001] This invention is a 5th generation (5G:5 th The present invention relates to a 5G (5G) wireless communication network, and more particularly to a method and system for enabling recovery from steering of roaming (SOR) related failures in a 5G wireless communication network. [Background technology]

[0002] 4G(4 thSince the commercialization of the 5G generation communication system, efforts have been made to develop an improved 5G communication system or pre-5G communication system to meet the increasing demand for wireless data traffic. For this reason, the 5G communication system or pre-5G communication system is called a beyond 4G network communication system or a post-LTE (long term evolution) system. In order to achieve high data transmission rates, the 5G communication system is being considered to be implemented in the mmWave band (e.g., 60 GHz band). In order to mitigate the propagation loss of radio waves in the mmWave band and extend the transmission distance, the following technologies are being discussed in the 5G communication system: beamforming, massive multiple-input multiple-output (MIMO), full dimensional multiple-output (FD-MIMO), array antenna, analog beamforming, and large scale antenna. In addition, in order to improve the system network, technologies such as advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device to device communication (D2D), wireless backhauls, moving networks, cooperative communication, coordinated multi-points (CoMP), and interference cancellation have been developed in the 5G communication system.

[0003] In addition, advanced coding modulation (ACM) schemes such as hybrid frequency shift keying (FSK), Feher's quadrature amplitude modulation (FQAM), and sliding window superposition coding (SWSC), as well as advanced access technologies such as filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA), are being developed for 5G systems.

[0004] Meanwhile, the Internet is evolving into an Internet of Things (IoT) network that exchanges and processes information between distributed components such as things in a human-centered connected network where people generate and consume information. IoE (Internet of Everything) technology, which combines big data processing technology through connection with cloud servers with IoT technology, has also been proposed. In order to realize the IoT, technological elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, technologies such as sensor networks for connecting things, M2M (machine to machine) communication, and MTC (machine type communication) are being researched. In the IoT environment, intelligent IT (internet technology) services that collect and analyze data generated by connected things and create new value in human life can be provided. The IoT will be applied to areas such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services through the fusion and integration of existing IT (information technology) and various industries.

[0005] As a result, various attempts are being made to apply the 5G communication system to IoT networks. For example, technologies such as sensor networks, machine to machine (M2M) and MTC are being implemented using techniques such as beam poking, MIMO and array antennas. The application of cloud radio access network (cloud RAN) as the big data processing technology mentioned above can also be said to be an example of the fusion of 5G technology and IoT technology.

[0006] As described above, with the development of wireless communication systems, various services can be provided, and therefore a method for easily providing such services is required.

[0007] The preceding information is presented as background information solely to aid in the understanding of the present disclosure. No determination or assertion has been made as to the applicability of any of the preceding as prior art to the present disclosure. Summary of the Invention [Problem to be solved by the invention]

[0008] As an example, a method may be provided for a terminal in a wireless communication system, the method including detecting a steering of roaming (SOR) failure in a manual mode during or after registration with a first visitor-public land mobile network (VPLMN), switching the manual mode to an automatic mode based on a determination that the SOR failure has occurred, and performing a public land mobile network (PLMN) selection procedure to obtain service in a second VPLMN having a higher priority than the first VPLMN. [Brief description of the drawings]

[0009] Embodiments of the present disclosure are illustrated in the accompanying drawings, in which like reference characters indicate corresponding parts in the various views throughout. Embodiments of the present disclosure will be better understood from the following description with reference to the drawings.

[0010] [Figure 1] 1 is a flowchart illustrating the problem of ignoring Steering of Roaming (SOR) related failures encountered by a User Equipment (UE) while operating in a manual mode, and thereby not taking any recovery action when the UE switches to an automatic mode of operation. [Figure 2A]FIG. 1 is a diagram illustrating an example scenario in which a UE configured to recover from a SOR-related failure by receiving SOR information from either a first VPLMN or a second VPLMN, according to an embodiment disclosed in the present disclosure, is camped on a first VPLMN (visitor-public land mobile network). [Figure 2B] 1 is a diagram for illustrating various units of a UE configured to recover from a SOR-related failure by receiving SOR information according to an embodiment as disclosed in the present disclosure. [Diagram 3] 1 is a flowchart illustrating a procedure for recovering from a SOR failure, i.e., triggering a PLMN search to detect a high priority second VPLMN and successfully register with the second VPLMN, to receive SOR information from a second VPLMN according to an embodiment as disclosed in the present disclosure. [Figure 4A] 11 is a flowchart illustrating another procedure for recovering from a SOR-related failure, i.e., triggering a PLMN search to detect a second VPLMN and successfully register with the second VPLMN to receive SOR information from the second VPLMN, according to an embodiment as disclosed in the present disclosure. [Figure 4B] 11 is a flowchart illustrating another procedure for recovering from a SOR-related failure, i.e., triggering a PLMN search to detect a second VPLMN and successfully register with the second VPLMN to receive SOR information from the second VPLMN, according to an embodiment as disclosed in the present disclosure. [Figure 5A] 11 is a flowchart illustrating yet another procedure for recovering from a SOR failure, namely, triggering initial registration with a first VPLMN to receive SOR information from the first VPLMN, according to an embodiment as disclosed in the present disclosure. [Figure 5B]11 is a flowchart illustrating yet another procedure for recovering from a SOR failure, namely, triggering initial registration with a first VPLMN to receive SOR information from the first VPLMN, according to an embodiment as disclosed in the present disclosure. [Figure 6] FIG. 2 is a block diagram of an entity according to an embodiment of the present disclosure. [Figure 7] FIG. 1 is a block diagram of a user equipment (UE) according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In one embodiment, a method for handling steering of roaming (SOR) failure by a user equipment (UE) in a fifth generation (5G) wireless network is provided, the method including detecting, by the user equipment (UE), a SOR failure from a first visitor-public land mobile network (VPLMN), where the UE is registered in the first VPLMN and the UE is operating in a manual mode, storing the detected SOR failure by the UE while operating in the manual mode in the first VPLMN, and resolving the SOR failure by the UE upon switching from the manual mode to an automatic mode while the UE is registered in the first VPLMN in which the SOR failure was detected.

[0012] In one embodiment, the SOR failure is also detected by the UE upon occurrence of at least one event. The at least one event may include non-reception of SOR information in the initial registration accept message and a security check performed on the received SOR information is not successful. As an example, the UE is also configured to receive SOR information in the initial registration accept message. As an example, the security check is not successful due to tampering of the received SOR information.

[0013] In one embodiment, the SOR failure is resolved by the UE by triggering a public land mobile network (PLMN) search upon switching to the automatic mode, where the PLMN search is performed after the UE moves to one of an idle state and a radio resource control (RRC) inactive state, as the UE attempts to acquire service from a high priority VPLMN, and the first VPLMN is also considered a low priority VPLMN during the PLMN search.

[0014] In one embodiment, the PLMN search may be triggered if there are no urgent protocol data unit (PDU) sessions active in the UE.

[0015] In one embodiment, in a user equipment (UE) for handling a steering of roaming (SOR) failure in a fifth generation (5G) wireless network, the UE is configured to detect a SOR failure from a first visitor-public land mobile network (VPLM), the UE being registered in the first VPLMN, the UE detecting the SOR failure while operating in a manual mode, storing the SOR failure detected while operating in the manual mode in the first VPLMN, and resolving the SOR failure upon switching from the manual mode to an automatic mode while the UE is registered in the first VPLMN in which the SOR failure was detected.

[0016] In one embodiment, a SOR failure is detected by the UE upon the occurrence of at least one event, the at least one event including non-receipt of SOR information in the initial registration accept message and a security check performed on the received SOR information being unsuccessful, wherein the UE is configured to receive SOR information in the initial registration accept message and the security check is unsuccessful due to tampering with the received SOR information.

[0017] In one embodiment, the SOR failure is resolved by the UE by triggering a public land mobile network (PLMN) search upon switching to the automatic mode, where the PLMN search is performed after the UE moves to one of an idle state and a radio resource control (RRC) inactive state, as the UE attempts to acquire service from a high priority VPLMN, and the first VPLMN is also considered a low priority VPLMN during the PLMN search.

[0018] In one embodiment, the PLMN search may be triggered if there are no urgent protocol data unit (PDU) sessions active at the UE.

[0019] In one embodiment, a method is provided in a wireless communication system, performed by a terminal (UE), the method including detecting a steering of roaming (SOR) failure during or after registering with a first VPLMN, where the UE may be operating in a manual mode, and based on a determination that a SOR failure has occurred, switching from the manual mode to an automatic mode, and performing a PLMN selection procedure to obtain service on a second VPLMN having a higher priority than the first VPLMN.

[0020] In one embodiment, if the first VPLMN is the PLMN in which the SOR failure occurred, the first VPLMN is also considered to be the lowest priority while performing the PLMN selection procedure.

[0021] In one embodiment, the UE may still be registered in the first VPLMN in which the SOR failure occurs when switching from manual mode to automatic mode.

[0022] In one embodiment, if the UE has an emergency PDU session established, the PLMN selection procedure may be performed after the emergency PDU session is released.

[0023] In one embodiment, a method performed by a terminal (UE) in a wireless communication system includes receiving a registration accept message from a first VPLMN while registering with the first VPLMN, the registration accept message including SOR information, and a SOR failure is also detected based on the registration accept message.

[0024] In one embodiment, it may be determined that a SOR failure occurs if the SOR information is missing in the registration accept message or if a security check of the SOR information fails during registration with the first VPLMN.

[0025] In one embodiment, the method performed by a terminal (UE) in a wireless communication system may further include operating in an idle mode or an RRC inactive mode before performing the PLMN selection procedure.

[0026] These and other aspects of the embodiments of the present disclosure will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating the present embodiments and many specific details thereof, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments of the present disclosure without departing from the spirit thereof, and the embodiments of the present disclosure include all such modifications.

[0027] Before proceeding with the detailed description below, it will be beneficial to provide definitions of certain words and phrases used throughout this patent document, as follows: the terms "comprise" and "including" and their derivatives refer to an open-ended inclusion; the term "or" is inclusive and means "and / or"; the terms "related to" and "associated with" as well as their derivatives refer to such terms as "comprise", "comprised in", "interconnected with", "including", "contained in", "connected to", "coupled to", "capable of communicating with", "cooperating with", "intervening through", "juxtaposing", "in proximity to", "bound to", "having", "having the nature of", and the term "controller" refers to any device, system or portion thereof that controls at least one operation, whether such device is embodied in hardware, firmware or software, or a subcombination of at least two of the same. It should be noted that the functionality associated with any particular control unit may be local or remote, centralized or distributed.

[0028] Moreover, various functions described below may be embodied or supported by one or more computer programs, each of which is formed from computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, procedures, functions, objects, classes, instances, associated data, or portions thereof suitable for embodiment in suitable computer-readable program code. The term "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The term "computer-readable medium" includes any type of medium that can be accessed by a computer, such as read only memory (ROM), random access memory (RAM), hard disk drive, compact disc (CD), digital versatile disc (DVD), or any other type of memory. A "non-transitory" computer-readable medium excludes wired, wireless, optical, or other communication links that transmit transient electrical or other signals. Non-transitory computer readable media include media on which data may be permanently stored, media on which data may be saved and later overwritten, such as rewritable optical disks or erasable memory devices.

[0029] Definitions of certain words and phrases are provided throughout this patent document and those of ordinary skill in the art should understand that in many, if not most, instances such definitions apply to prior and future uses of the words and phrases so defined.

[0030] 1-7 discussed below and in this patent document, the various embodiments used to explain the principles of the present disclosure are merely illustrative and are not to be construed in a manner limiting the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present disclosure may be embodied in any suitably arranged system or device.

[0031] The embodiments of the present disclosure and their various features and advantageous details will be more fully described with reference to the non-limiting embodiments illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as not to unnecessarily obscure the embodiments of the present disclosure. The examples used in the present disclosure are merely intended to facilitate understanding of how the embodiments of the present disclosure can be implemented and further enable those skilled in the art to implement the embodiments of the present disclosure. Therefore, the examples should not be construed as limiting the scope of the embodiments of the present disclosure.

[0032] The main objective of the embodiments in the present disclosure is to provide a mechanism that enables a User Equipment (UE) operating in a manual mode and camping on a visitor-public land mobile network (VPLMN) to recover from a Steering of Roaming (SOR) related failure, and to disclose a method and system whereby a recovery mechanism can be triggered by the UE when the UE is switched from manual mode to automatic mode while remaining camped on the VPLMN where a SOR failure is detected.

[0033] Another objective of the embodiments in the present disclosure is to track SOR related failures experienced by a UE when the UE is operating in manual mode.

[0034] Another objective of embodiments of the present disclosure is to initiate recovery procedures to overcome SOR related failures when the UE switches to automatic mode while the UE does not receive authentic SOR information while operating in manual mode, while remaining camped on the VPLMN where the SOR failure was detected.

[0035] Another objective of the embodiments of the present disclosure is to trigger an initial registration with a VPLMN when a UE switches from a manual mode to an automatic mode to recover from a SOR related failure, and if the initial registration is successful and the UE receives true SOR information during registration, the UE can recover from the SOR related failure.

[0036] Another objective of an embodiment of the present disclosure is to detect at least one other VPLMN and trigger a PLMN search procedure to register on the VPLMN in order to recover from the SOR related failure when the UE switches from manual mode to automatic mode while maintaining camping on the VPLMN in which the SOR failure is detected, and during the PLMN search, consider the VPLMN in which the SOR related procedure occurred as the least desirable VPLMN, and if the registration is successful and the UE receives true SOR information during registration, the UE can recover from the SOR related failure.

[0037] Another objective of embodiments in the present disclosure is to periodically trigger a PLMN search procedure to recover from the SOR related failure when a UE operating in automatic mode (the UE experienced a SOR related failure while operating in manual mode) is unable to register in another VPLMN and has to camp on the VPLMN in which it experienced the SOR related failure.

[0038] Accordingly, embodiments of the present disclosure provide a method and system for recovering from a Steering of Roaming (SOR) related failure. The embodiment includes detecting an SOR related failure when a user equipment (UE) is operating in a manual mode. The embodiment includes tracking the occurrence of an SOR related failure detected by the UE operating in the manual mode. The embodiment includes storing an identity of a VPLMN for which an SOR related failure is detected by the UE.

[0039] In one embodiment, the UE may use a flag to track the occurrence of a SOR related failure. The status of the flag may indicate whether a UE operating in manual mode is experiencing a SOR related failure when the UE is camping on the first VPLMN. If the UE experiences a SOR failure, the UE may set a flag. The flag may be reset when the SOR failure is resolved.

[0040] In one embodiment, the UE can track the occurrence of SOR related failures using a list that includes VPLMNs for which the UE experienced SOR related failures when the UE was operating in manual mode. In one embodiment, the existing list of "SOR-Aborted Registration PLMNs" can be reused to identify VPLMNs for which the UE experienced SOR related failures when the UE was operating in manual mode. The list can be cleared once the SOR failures are resolved.

[0041] One embodiment includes resolving the SOR failure by receiving accurate SOR information. The SOR information may be received by registering with a VPLMN. When the UE switches from manual mode to automatic mode, the UE may trigger an initial registration to a first VPLMN. If the UE receives the SOR information and the SOR information is decoded without any failure from the first VPLMN (where the first VPLMN is the PLMN where the UE was registered in manual mode and where the SOR failure was encountered), the initial registration is considered successful and the SOR failure is resolved. In another embodiment, instead of using the initial registration procedure to refresh the SOR information, the UE may attempt a PLMN search and may attempt to find a second VPLMN, i.e., a high priority VPLMN. During the search, the UE camps on the first VPLMN where the SOR failure was detected. After the UE detects the second VPLMN, the UE may register with the second VPLMN. A PLMN search may be triggered when the UE switches to automatic mode. Since the registration is successful, if the UE receives SOR information from the second VPLMN and the received SOR information is decoded without any failure, the SOR failure is considered to be resolved.

[0042] One embodiment includes checking whether SOR information has been received after registration in the first VPLMN and / or the second VPLMN. If no SOR information has been received after registration, the flag may remain set and / or the list may continue to be filled with entries for PLMNs for which SOR failures occurred. If SOR information is received after a new registration and security checks performed on the received SOR information are successful, the flag may be reset and / or the first VPLMN may be removed from the list. If the UE registers in the second VPLMN and does not receive SOR information or security checks performed on the SOR information fail, the second VPLMN may be deprioritized. The UE may then initiate a PLMN search to find other allowed PLMNs that are available. The sequence of attempting searches for allowed PLMNs continues and based on the result of receiving / decoding the SOR information, the same set of actions previously defined for the first VPLMN and the second VPLMN may be performed for the other PLMNs. If no allowed PLMN other than the PLMN where the SOR failure occurred is found, the UE registers to the first VPLMN or any other PLMN where the SOR failure occurred, and periodically triggers a PLMN search to detect a high priority VPLMN and register to the VPLMN to receive SOR information.

[0043] One embodiment includes initializing a back-off timer to control how often a PLMN search is triggered, and the UE can prevent procedures that may initiate a PLMN search to recover from a SOR failure prior to expiration of the back-off timer.

[0044] DETAILED DESCRIPTION OF THE DRAWINGS

[0004] Embodiments of the present disclosure provide a method and system for recovering from a Steering of Roaming (SOR) related failure, including enabling a User Equipment (UE) camping on a VPLMN to recover from a SOR related failure encountered by the UE while operating in a manual or automatic mode. Referring now to the drawings, and more particularly to Figures 1 through 7, in which like reference characters indicate corresponding features consistently throughout, a preferred embodiment is shown.

[0045] The roaming steering (SOR) feature is used by network operators to ensure that a home-public land mobile network (HPLMN) can steer a subscriber to the most desirable VPLMN for a given location. Roaming steering (SOR) is accomplished by providing a list of desirable VPLMNs for that location, i.e., SOR information, to a user equipment (UE) (i.e., a device used by a user), and having the UE camp on one of the desirable VPLMNs. However, the HPLMN must route the SOR information to the UE via the VPLMN in which the UE is currently registered or has been registered.

[0046] However, there may be SOR failure scenarios, i.e., the VPLMN (on which the UE is currently camped) does not provide the UE with a list of preferred VPLMNs, the VPLMN (on which the UE is currently camped) provides the UE with a list of preferred VPLMNs with incorrect content, etc., which occur to ensure that the UE remains camped on that VPLMN. Camping on the least desirable / undesired PLMNs also leads to revenue loss for the HPLMN due to higher operational costs for the HPLMN, and subscriber loss due to higher service costs.

[0047] To eliminate SOR failure scenarios, further requirements for detecting and recovering from SOR failure scenarios have been proposed by the 3rd Generation Partnership Project (3GPP) for 5th Generation (5G) communications. rd This requirement was formalized in the VPLMN (VLAN Generation Partnership Project) standard, Technical Standard (TS) 23.122, Release 15. Some of the defined requirements mandate that the SOR related information is received by the UE during initial registration to the VPLMN and that the integrity of the SOR related information is protected so that only the HPLMN-unified data management (HPLMN-UDM) and the UE can encode / decode the SOR related information. It allows the UE to detect any tampering / removal of the SOR information by the VPLMN nodes in any non-access stratum (NAS) messages to the UE. If the UE detects the absence or tampering of the SOR related information, the UE can activate recovery mechanisms, which were defined to allow the UE to trigger a search for the availability of any other PLMNs.

[0048] The recovery mechanism defined to recover from SOR failure scenarios is not triggered if the UE encounters a SOR failure when operating in manual mode, mainly because manual mode is selected by the user and the user is responsible for selecting the PLMN (operator) to receive the service. Therefore, the UE will continue to maintain registration with the VPLMN even if a SOR failure is detected. Therefore, even if the UE is switched from manual mode to automatic mode, the UE will continue to camp on the same PLMN where it encountered the SOR failure.

[0049] 1 is a flow chart (100) illustrating the problem caused by a UE ignoring a SOR failure in a manual mode of operation. In step 101, a UE attempts to register with a VPLMN while operating in a manual mode. The UE's user services identity module (USIM) is configured to mandatory receive SOR information from the VPLMN during registration with the VPLMN. Once the VPLMN accepts the UE's registration request, in step 102, the UE detects that a SOR failure scenario has occurred when a determination is made that SOR information is missing or that the SOR information received from the VPLMN has been tampered with.

[0050] The UE may perform a security check on the received SOR information to determine whether the integrity of the SOR information has been compromised. If the security check fails, the UE may infer that the integrity of the SOR information has been compromised. Non-receipt of the SOR information and detection of unauthorized modification of the SOR information constitute the occurrence of a SOR failure scenario. Since the UE is operating in manual mode, the occurrence of a SOR failure scenario in step 103 is ignored because in manual mode the user selected the currently selected PLMN and therefore continues to camp on the PLMN where the SOR failure occurred.

[0051] Thus, when the UE switches to automatic mode, the UE does not trigger a recovery scan to detect other VPLMNs to recover from the SOR failure it experienced while operating in manual mode. In step 104, the UE continues to camp on the same VPLMN in which it experienced a SOR failure, despite the possible availability of one or more desirable VPLMNs (of HPLMNs) in the area.

[0052] FIG. 2A illustrates an example scenario in which a UE is camped on a first VPLMN and configured to recover from a SOR related failure by receiving SOR information from either the first VPLMN or a second VPLMN, according to an embodiment as disclosed in the present disclosure. As illustrated in FIG. 2A, a UE camped on a first VPLMN detects a SOR related failure while operating in a manual mode. When the UE switches to an automatic mode, the UE can track the SOR related failure and can initiate a recovery procedure to resolve the SOR related failure. After switching from a manual mode while the UE remains attached to the first VPLMN, the UE can initiate a recovery procedure when the UE begins to operate in an automatic mode. If the UE can receive true SOR information from the first VPLMN while the UE operates in a manual mode, no recovery procedure is initiated. The restoration procedure allows the UE to receive SOR information from a second VPLMN (higher priority VPLMN) if the UE can successfully detect and register with the second VPLMN. If the UE cannot receive SOR information from the first VPLMN or the security check performed on the SOR information received from the first VPLMN fails, the UE triggers a PLMN search to detect the second VPLMN.

[0053] In one embodiment, the restoration procedure includes triggering an initial registration to a first VPLMN in which the UE experienced a SOR-related failure when the UE was operating in a manual mode. The initial registration is triggered when the UE switches from a manual mode to an automatic mode. If the initial registration is successful, the SOR-related failure is considered resolved because the initial registration is considered successful only if the UE receives true SOR information during initial registration to the first VPLMN.

[0054] In one embodiment, the restoration procedure includes triggering a PLMN search procedure when the UE switches from manual mode to automatic mode. During the PLMN search, the first VPLMN on which the UE is currently camped is considered the least desirable PLMN. The PLMN search is initiated after the UE 200 moves to one of an idle state and a radio resource control (RRC) inactive state. If the UE can detect a second VPLMN during the PLMN search and receives true SOR information during registration with the second VPLMN, the SOR related failure may be considered resolved.

[0055] The registration procedure in this embodiment is referred to as an initial registration procedure or a mobile registration procedure.

[0056] In one embodiment, the recovery procedure includes periodically triggering a PLMN search to recover from the SOR related failure. The periodic triggering continues if the UE operating in automatic mode is unable to register to the second VPLMN and / or the UE is unable to receive true SOR information from the second VPLMN during registration to the second VPLMN. In this scenario, the UE will camp and remain registered on any PLMN in which it experienced a SOR failure (the first VPLMN or the second VPLMN in the current case) and periodically attempt SOR information recovery. This embodiment includes initializing a back-off timer to control how often to trigger a PLMN search.

[0057] FIG. 2B illustrates various units of a UE 200 configured to recover from a SOR-related failure by receiving SOR information according to an embodiment as disclosed in the present disclosure. As illustrated in FIG. 2B, the UE 200 includes a processor 201, a communication interface 202, a memory 203, and a display 204. The UE 200 can camp on a first VPLMN. A User Service Identity Module (USIM) of the UE 200 is configured to obligatorily receive SOR information from the first VPLMN during initial registration to the first VPLMN. The SOR information allows the UE 200 to camp on a VPLMN invited by the HPLMN.

[0058] If the UE 200 operating in manual / automatic mode encounters a SOR failure, the processor 201 can trigger a recovery mechanism to resolve the SOR failure. The integrity of the received SOR information is also considered corrupted or identified as tampered with if a security check performed on the received SOR information fails. If the security check passes, the received SOR information is also considered as true SOR information. If the processor 201 determines that the received SOR information is true based on the security check, the SOR failure is considered to be resolved.

[0059] If UE 200 encounters a SOR failure, if UE 200 is operating in manual mode, a recovery mechanism may be triggered when UE 200 switches from manual mode to automatic mode. If the SOR failure is resolved while UE 200 is still operating in manual mode, processor 201 may not trigger a recovery mechanism to resolve the SOR related failure. If processor 201 can determine that a SOR failure occurred when UE 200 was operating in manual mode, a recovery mechanism may be triggered by processor 201 after UE 200 switches to automatic mode while UE 200 maintains camping on the first VPLMN.

[0060] When the UE 200 is operating in the manual mode, the processor 201 is also configured to track any occurrence of SOR failure. In one embodiment, the processor 201 may use a flag to track the occurrence of SOR failure. The processor 201 may set the SOR failure flag to "1" or "true" or reset the SOR failure flag to "0" or "false". If the UE 200 faces a SOR failure, the processor 201 may set the flag. The processor 201 may reset the flag when the SOR failure is resolved. The processor 201 may check the status (set / reset) of the flag when the UE 200 switches to the automatic mode. If the flag is set, the processor 201 may determine that a SOR failure occurred when the UE 200 was operating in the manual mode. If the flag is reset, the processor 201 may determine that a SOR failure did not occur when the UE 200 was operating in the manual mode.

[0061] In one embodiment, the processor 201 can track occurrences of SOR failures when the UE 200 is operating in manual mode by maintaining a list of VPLMNs for which the UE 200 has experienced SOR failures in the memory 203. In one embodiment, the processor 201 can track occurrences of SOR failures using a list of "PLMNs whose registration was aborted by SOR."

[0062] In one example, if UE 200 encounters a SOR failure while operating in manual mode when camping on a first VPLMN, processor 201 populates the list with the first VPLMN on which UE 200 is camped. At any time, UE 200 operating in manual mode may receive SOR information from the first VPLMN, and if the received SOR information is successfully decoded, processor 201 may reset a flag and / or remove the first VPLMN from the list. If UE receives an indication from the first VPLMN that no SOR information is provided, processor 201 may reset a flag and / or remove the first VPLMN from the list.

[0063] The embodiments in this disclosure are described with only one VPLMN loaded into the list, however, it will be apparent to one skilled in the art that there may be more than one VPLMN loaded into the list.

[0064] This is because, when the UE 200 is operating in manual mode, the processor 201 can trigger a PLMN search, although there may be a scenario (i.e., the user selects a different PLMN). If the UE 200 can successfully register with another VPLMN while operating in manual mode during registration in which SOR information is received, and the SOR failure is also considered to be resolved if the SOR information is successfully decoded. The UE 200 can only successfully decode the SOR information if it is true. If a security check performed on the received SOR information is successful, the SOR information is determined to be true. This is because, according to the 3GPP standard, the UE 200 is configured to obligatorily receive SOR information from the VPLMN during initial registration to the VPLMN. If the UE 200 receives the SOR information during registration, the processor 201 can reset a flag and / or remove a list used to store VPLMNs for which SOR failures have been previously encountered.

[0065] It is considered that a SOR failure occurred when UE 200 camped on the first VPLMN was operating in manual mode. When facing a SOR failure, UE 200 sets a flag and / or populates the first VPLMN on the list. When UE 200 was operating in manual mode, the SOR failure is not resolved. When UE 200 switches to automatic mode, processor 201 can determine that the flag is set and / or the first VPLMN is populated on the list and infer that a SOR failure occurred when UE 200 was operating in manual mode.

[0066] In one embodiment, the UE 200 initiates a first recovery procedure in order to receive unreceived or incorrectly altered SOR information (that was detected by the processor 201 when the UE 200 was operating in manual mode). The recovery procedure allows the processor 201 to trigger an initial registration to the first VPLMN. If the initial registration to the first VPLMN is found to be successful and the SOR information is successfully received and decoded without any errors, the SOR failure is also considered resolved. The consideration may be applicable if the USIM in the UE 200 is configured to mandatory receive SOR information from the first VPLMN during the initial registration of the UE 200 to the first VPLMN.

[0067] The initial registration is also considered successful only if the UE 200 receives SOR information from the first VPLMN during initial registration and the processor 201 determines that the integrity of the SOR information is not corrupted, after which the processor 201 may reset the flag and / or remove the first VPLMN from the list.

[0068] On the other hand, if the UE 200 does not receive SOR information from the first VPLMN during initial registration or the processor 201 determines that the integrity of the SOR information received from the first VPLMN has been corrupted, the SOR failure is also considered to be persistent. The flag remains set and / or the list continues to be populated with the first VPLMN. The processor 201 may periodically trigger a PLMN search to detect high priority VPLMNs and attempt to register with the detected VPLMNs.

[0069] If the USIM is not configured to mandatory receive SOR information from the first VPLMN during initial registration and no SOR information is received during initial registration, the flag is not reset by the processor 201 and / or the first VPLMN is continuously filled in the list. The UE 200 may periodically trigger a PLMN search to detect high priority VPLMNs and attempt to register on the detected VPLMNs.

[0070] In another embodiment, the UE 200 can initiate a second recovery mechanism, which allows the processor 201 of the UE 200 to trigger a PLMN search. The PLMN search is triggered while the UE 200 remains camped on the first VPLMN. The PLMN search is triggered after the UE 200 moves to an idle state and / or is in an RRC inactive state. During the PLMN search, the first VPLMN on which the UE 200 is currently camped is considered the least desirable VPLMN. In general, when the UE 200 maintains a list of VPLMNs on which SOR failures have occurred, all VPLMNs in the list are considered to be of the lowest priority. This embodiment includes selecting a configuration to prioritize VPLMNs in the list of VPLMNs on which SOR failures have been encountered. The SOR failure may also be considered resolved if the UE 200 successfully detects the second VPLMN and successfully completes initial registration with the second VPLMN.

[0071] The USIM is configured to receive SOR information from the second VPLMN during initial registration to the second VPLMN. Thus, the registration of the UE 200 to the second VPLMN is also considered successful if the UE 200 can receive SOR information from the second VPLMN. A successful registration to the second VPLMN may indicate that the UE 200 did not encounter any SOR related failure, i.e., the second VPLMN has provided SOR information to the UE 200. The processor 201 may then reset the flag and / or remove the first VPLMN from the list. If the UE 200 receives SOR information from the core network via a NAS message, the processor 201 may further reset the flag and / or remove the first VPLMN from the list. In one embodiment, all VPLMNs in the list may be cleared instead of being removed from a single VPLMN.

[0072] On the other hand, if the UE 200 does not receive SOR information from the second VPLMN or the processor 201 determines that the integrity of the SOR information received from the second VPLMN has been tampered with, the SOR failure is also considered to be persistent. Due to the lack of integrity, the SOR information received from the second VPLMN is not authenticated. The UE 200 will try to find a different VPLMN in which the SOR failure is not faced. The flag will remain set and / or the list will be filled continuously for both the first VPLMN and the second VPLMN. If no other PLMN is found, the UE will register on any VPLMN in which the SOR failure was faced, i.e., on the first VPLMN or the second VPLMN. The processor 201 may periodically trigger a PLMN search to find a high priority VPLMN other than the VPLMN in which the SOR failure was faced and register on that VPLMN. The UE 200 aims to receive the SOR information during initial registration or via any other NAS message.

[0073] If the UE 200 is working in automatic mode and the SOR failure is not resolved (flag is set and / or the first VPLMN is filled in the list), the processor 201 of the UE 200 can periodically trigger a PLMN search. At the current moment, the UE 200 is considered to be camping on the first VPLMN, because previous attempts to receive SOR information by registering in other VPLMNs have not been successful. The PLMN search is periodically triggered to obtain service from a higher priority VPLMN, as identified by the HPLMN. The first VPLMN, the second VPLMN, and other VPLMNs filled in the list (if SOR failure was faced in manual mode) are considered to be the lowest priority (or least desirable) during the PLMN search and during the selection procedure.

[0074] In one embodiment, if the UE 200 experiences a SOR failure, the UE 200 may periodically trigger a PLMN search even if the UE 200 is currently registered on a most preferred OPLMN (operator PLMN) according to the existing OPLMN list.

[0075] In one embodiment, the processor 201 of the UE 200 may initialize a first timer that may expire after a predefined time interval (as long as the UE 200 remains camped on the VPLMN where the SOR failure occurred). Once the first timer expires, the processor 201 may trigger a PLMN search. During the PLMN search, the VPLMNs filled in the list (where the SOR failure was encountered) are considered to be low-priority VPLMNs. If an allowed VPLMN (other than the one in the SOR failure list) is detected during the PLMN search, the UE 200 may attempt to register with the detected VPLMN. During the registration procedure, if the processor 201 determines that no SOR information is received or the received SOR information is tampered with, the registration is considered unsuccessful and the processor 201 may start the first timer anew. If the SOR information received from the first VPLMN is not tampered with, i.e., true, the SOR failure is considered to be resolved. Also, after expiration of the first timer, the processor 201 may trigger a further PLMN search.

[0076] In one embodiment, the second timer is also initialized by the existing 3GPP standard that determines the periodicity of the PLMN search. The second timer may be initialized if the first VPLMN on which the UE 200 is camped is not a high priority VPLMN in the location. In one embodiment, even if the existing conditions in the 3GPP standard do not result in the start of the second timer, the SOR failure is also considered as a trigger to force start the second timer. When the second timer expires, the PLMN search may be triggered. During the PLMN search, the VPLMNs in the list are considered as low priority VPLMNs. If the first VPLMN is one of the least desirable VPLMNs based on the information specified by the HPLMN, the second timer may be force-triggered by the processor 201. If the SOR failure continues to persist, the second timer may also be force-triggered periodically by the processor 201. The SOR failure persists if the UE 200 is unable to register with a VPLMN that provides SOR information during initial registration to the UE 200. The processor 201 may trigger a PLMN search after expiration of the second timer.

[0077] The processor 201 may periodically trigger a PLMN search with a periodicity of a time interval ranging from the start to the expiration of the first or second timer until the UE 200 can recover from the SOR failure. The UE 200 may recover from the SOR failure by receiving accurate SOR information from a VPLMN detected during the PLMN search, the SOR information being received during registration with the detected VPLMN. Once the SOR failure is resolved, neither the first nor the second timer is triggered by the processor 201.

[0078] While the UE 200 is in the process of being camped and registered on the first VPLMN (when the UE 200 faces a SOR failure), possibly in the same area, the processor 201 may trigger a PLMN search due to the occurrence of another procedure that recovers from the SOR related failure and thus causes the processor 201 to trigger a PLMN search prior to the expiration of the first or second timer. In such a scenario, the processor 201 may avoid triggering frequent PLMN searches. In one embodiment, the processor 201 may initialize a back-off timer that expires after a predefined time interval.

[0079] The processor 201 may configure the back-off timer to ensure that a PLMN search is triggered after expiration of the back-off timer, regardless of whether there is a trigger to initiate a PLMN search due to expiration of the first timer or the second timer, or any other existing triggers for initiating a PLMN search. The back-off timer may be started after a PLMN search is performed (due to detection of absence of SOR information or failure of security check on SOR information) and UE 200 that is unable to successfully register in a VPLMN further registers in a first VPLMN (typically the VPLMN where SOR failure was first encountered and has not yet been resolved).

[0080] The processor 201 may prevent a procedure of triggering a PLMN search to resolve a SOR failure prior to the back-off timer expiry, but may stop the back-off timer if the processor 201 detects a change in the location of the UE 200, a change in network coverage conditions, availability of a new network, etc.

[0081] 2B illustrates exemplary units of UE 200, it should be understood that other embodiments are not limited thereto. In other embodiments, UE 200 may include fewer or more units. Furthermore, the labels or names of the units of UE 200 are used for illustrative purposes only and do not limit the scope of the present disclosure. One or more units may be combined together to perform the same or substantially similar functions of UE 200.

[0082] 3 is a flow chart illustrating a method for recovering from a SOR failure, i.e., triggering a PLMN search (300) to detect a high priority second VPLMN and successfully register with the second VPLMN to receive SOR information from the second VPLMN, according to an embodiment as disclosed in the present disclosure. In step 301, the method includes registering with a first VPLMN while operating in a manual mode. If the first VPLMN accepts the UE 200's registration request, the UE 200 camps on the first VPLMN. In step 302, the method includes detecting an SOR failure occurrence. It may occur during the registration procedure with the first VPLMN or after the UE 200 has registered with the first VPLMN.

[0083] Examples of SOR failures are determining that SOR information is missing in the initial registration accept message (even though UE 200 is configured to receive SOR information in the initial registration accept message), that the SOR information received from the first VPLMN has been tampered with, etc. If the SOR information received from the first VPLMN has not been tampered with, i.e., if the received SOR information is true, the SOR failure is considered resolved.

[0084] In step 303, the method includes tracking (storing) the occurrence of SOR failure. In one embodiment, UE 200 operating in manual mode may use a flag to track the occurrence of SOR failure. The SOR failure flag may be set to "1" or may also be reset to "0". UE 200 may set the flag when it encounters a SOR failure. UE 200 may reset the reset flag to "0" when the SOR failure is resolved. If UE 200 detects a SOR failure, the flag is set.

[0085] In one embodiment, a UE 200 operating in manual mode can track (store) occurrences of SOR failures by maintaining a list of VPLMNs encountered by the UE 200. If the UE 200 detects a SOR failure, the first VPLMN is populated onto the list. In one embodiment, a list of "PLMNs whose registration was aborted by SOR" can be used to track occurrences of SOR failures.

[0086] If the embodiment triggers a PLMN search, there may be the possibility to resolve the SOR failure by other procedures while the UE 200 is operating in manual mode. If the UE 200 can detect a high priority VPLMN during the PLMN search and successfully registers with the high priority VPLMN, the SOR information is received while operating in manual mode.

[0087] In step 304, the UE 200 is switched out of the manual mode and begins operating in the automatic mode. In step 305, the method includes determining that a SOR failure occurred on the first VPLMN when the UE 200 is operating in the manual mode and the SOR failure has not yet been resolved. This embodiment includes determining that a SOR failure occurred by checking a flag and / or a list status (set / reset). This embodiment includes determining that a flag is set and / or the first VPLMN is populated on the list. In step 306, the UE 200 continues to remain camped on the first VPLMN.

[0088] In step 307, the method includes determining whether UE 200 is operating in an idle state and an RRC inactive state. If it is determined that the UE is operating in an idle state and the RRC is inactive, the method includes determining whether UE 200 has an established emergency protocol data unit (PDU) session in step 308. If it is determined that UE 200 is not operating in an idle state and the RRC is active, UE 200 continues to camp on the first VPLMN seeing (step 306).

[0089] If it is determined in step 308 that the UE 200 has established an emergency PDU session, the method includes determining whether the emergency PDU session has been released in step 309. If the PDU session is active, the UE 200 needs to wait and continue to check whether the PDU session has been released (step 309). If it is determined in step 309 that the PDU session has been released, the method includes determining whether the UE 200 is operating in an idle state and an RRC inactive state (step 307).

[0090] If the UE 200 has not established an emergency PDU session, as determined in step 308, or if there is no active emergency PDU session, the method includes assuming that the first VPLMN is the lowest priority during the PLMN search and triggering a PLMN search to find a second VPLMN, which is a higher priority VPLMN, in step 310. The UE 200 must wait until the UE 200 is operating in an idle state and RRC is in an inactive state, and any emergency PDU session, if established, must be released in order to trigger the PLMN search procedure.

[0091] The PLMN search aims to detect and register with the second VPLMN without any SOR failure. If UE 200 can successfully register with the second VPLMN and there is no SOR failure, the SOR failure is considered to be resolved. If UE 200 receives SOR information from the second VPLMN during registration and the security check performed on the received VPLMN is successful, the registration is considered to be successful.

[0092] The various actions in flowchart 300 may be performed in the order presented, in a different order, or simultaneously. Further, in some embodiments, some actions listed in FIG.

[0093] 4A and 4B illustrate a flow chart of a method (400) depicting another procedure for recovering from a SOR failure, i.e., a procedure for detecting a second VPLMN and triggering a PLMN search to successfully register with the second VPLMN in order to receive SOR information from the second VPLMN, according to an embodiment as disclosed in the present disclosure. In step 401, the UE 200 attempts to register with a first VPLMN while operating in a manual mode. If the first VPLMN accepts the UE 200's registration request, the UE 200 camps on the first VPLMN. In step 402, the embodiment includes detecting an occurrence of a SOR failure. Examples of the SOR failure include determining that SOR information is missing, that the SOR information received from the first VPLMN has been tampered with, etc. If the SOR information received from the first VPLMN has not been tampered with, i.e., true, the SOR failure is considered resolved.

[0094] In step 403, the present embodiment includes tracking the occurrence of SOR failure. In one embodiment, UE 200 operating in manual mode may use a flag to track the occurrence of SOR failure. The SOR failure flag may be set to "1" or reset to "0". UE 200 may set the flag when it experiences a SOR failure. UE 200 may reset the reset flag to "0" when the SOR failure is resolved. If UE 200 detects a SOR failure, the flag is set.

[0095] In one embodiment, a UE 200 operating in manual mode can track occurrences of SOR failures by maintaining a list of VPLMNs encountered by the UE 200. If the UE 200 detects a SOR failure, the first VPLMN is populated onto the list. In one embodiment, a list of "PLMNs with SOR aborted registration" can be used to track occurrences of SOR failures.

[0096] If the embodiment triggers a PLMN search, there may be a possibility to resolve the SOR failure by other procedures while the UE 200 is operating in manual mode. If the UE 200 can detect other VPLMNs during the search and successfully registers with the detected VPLMNs, the SOR information is received while operating in manual mode, because the 3GPP standard configures the UE 200 to mandatory receive SOR information from the VPLMN during registration to the VPLMN if the registration is deemed successful. When receiving SOR information from the detected VPLMN, the embodiment includes performing a security check on the received SOR information. If the security check is passed, the embodiment includes resetting a flag and / or removing the first VPLMN from the list.

[0097] If UE 200 receives an indication from the first VPLMN that no SOR information is provided, the embodiment may reset the flag and / or remove the first VPLMN from the list. If UE 200 is unable to receive SOR information, the flag remains set and / or the first VPLMN remains populated in the list as long as UE 200 is operating in manual mode.

[0098] In step 404, the UE 200 is switched out of the manual mode and begins to operate in the automatic mode. In step 405, the embodiment includes determining whether a SOR failure that occurred when the UE 200 was operating in the manual mode has been resolved. The embodiment includes checking the status (set / reset) of the list and / or flag to determine whether such an outstanding SOR failure exists. If the flag is reset and / or the UE 200 determines in step 406 that the first VPLMN is not populated on the list, the embodiment determines that there is no outstanding SOR failure. As a result, no recovery mechanism is triggered. The embodiment may trigger a PLMN selection according to normal PLMN selection priority. If the flag is set and / or the first VPLMN is determined to be populated on the list, the embodiment includes determining in step 407 that a SOR failure occurred when the UE 200 was operating in the manual mode that needs to be resolved. An outstanding SOR failure may indicate that the UE 200 needs to receive SOR information.

[0099] If there is a detected pending failure (at step 407), the embodiment includes triggering a recovery mechanism. At step 408, the embodiment includes triggering a PLMN search while the UE 200 is camping on the first VPLMN. The PLMN search may be triggered immediately after the UE 200 detects that a flag is set and / or the first VPLMN is loaded on the list. In one embodiment, the PLMN search may be triggered after the UE 200 moves to one of an idle state or an RRC inactive state. The triggering may be postponed until the UE 200 moves to an idle mode or if there is an active data session. During the PLMN search, the first VPLMN is considered the least desirable VPLMN (since the first VPLMN is loaded on the list). The goal of the PLMN search is to find a second VPLMN that is also a high priority VPLMN, the priority of which is higher than the priority of the first VPLMN, and to attempt to register in the second VPLMN.

[0100] This embodiment includes determining whether UE 200 can successfully register with the second VPLMN in step 409. If UE 200 receives SOR information from the second VPLMN while registered and the security check performed on the received VPLMN is successful, the registration is deemed successful. If it is determined that registration with the second VPLMN is successful, the SOR failure is deemed resolved in step 410.

[0101] If it is determined that registration with the second VPLMN is not successful, the SOR failure is deemed to persist in step 411. If the UE 200 does not receive SOR information from the second VPLMN during registration or the integrity of the SOR information received from the second VPLMN is corrupted, registration with the second VPLMN is deemed to be unsuccessful. The flag remains set and / or the list is populated with the second VPLMN, where the first VPLMN was previously included. This embodiment includes attempting to register with either the first or second VPLMN until the UE is able to resolve the SOR failure by successfully receiving and decoding SOR information from the VPLMN.

[0102] This embodiment includes periodically triggering a PLMN search to find other high priority VPLMNs, as identified by the HPLMN, and registering with the detected VPLMNs. The UE 200 maintains camping on either the first VPLMN or the second VPLMN. The first VPLMN and the second VPLMN are considered to be of lowest priority during the PLMN search and selection procedure.

[0103] In step 412, the present embodiment includes determining whether a timer (which may be a first timer or a second timer) is started. The timer may be initialized by the 3GPP standard to manage PLMN scan triggering. The present embodiment may trigger a PLMN search when the timer expires. The timer may also be configured to expire after a predefined time interval.

[0104] If it is determined that the timer has been initialized, the embodiment includes determining whether the timer has expired in step 413. If it is determined that the timer has expired, the embodiment includes triggering a PLMN search in step 414. During the PLMN search, the first and second VPLMNs populated in the list are considered low priority VPLMNs. The PLMN search aims to detect a high priority VPLMN and to register on the high priority VPLMN. The embodiment includes detecting the high priority VPLMN and attempting to register on the high priority VPLMN. In step 415, the embodiment includes determining whether the UE 200 can successfully register on the detected VPLMN. If it is determined that registration on the detected high priority VPLMN has been successful and SOR information has been received without any decoding failure, the SOR failure is considered resolved (step 410). The UE 200 may recover from a SOR failure by receiving accurate SOR information from the detected VPLMN if the registration is successful.

[0105] If it is determined that the registration was not successful, the SOR failure is considered to persist (step 411). Either the SOR information was not received or the integrity of the received SOR information was corrupted by a detected high priority VPLMN. The embodiment includes starting a new timer (step 412 "YES"). After expiration of the timer (step 413), the embodiment includes triggering a further PLMN search (step 414).

[0106] If it is determined (at step 412) that the timer has not started, the embodiment includes forcing the timer to start at step 416. The embodiment then includes triggering a PLMN search (step 414) after expiration of the timer (step 413).

[0107] This embodiment triggers PLMN searches periodically and continuously, with a periodicity of a time interval spanning from the start to the expiration of a timer. The UE 200 can recover from a SOR failure (step 410) by receiving accurate SOR information from a high priority VPLMN (step 414) that is detected during the PLMN search, which SOR information is received while registering to the detected VPLMN (step 415 “Yes”).

[0108] This embodiment avoids triggering frequent PLMN searches by initializing a back-off timer that expires after a predefined time period. This embodiment can prevent other procedures from triggering a PLMN search to resolve a SOR failure prior to the expiration of the back-off timer, or from triggering a PLMN search after the timer expires. This embodiment configures a back-off timer to ensure that a PLMN search is triggered after the timer expires while the UE 200 is camping on either the first VPLMN or the second VPLMN. The back-off timer is started after a PLMN search is performed (step 414), and a UE 200 that is unable to successfully register in a VPLMN will further register in the first VPLMN or the second VPLMN if a SOR failure is first encountered (step 411).

[0109] The various actions in flowchart 400 may be performed in the order presented, in a different order, or simultaneously. Further, in some embodiments, some actions listed in FIG.

[0110] 5A and 5B are a flow chart (500) illustrating yet another procedure for recovering from a SOR failure, i.e., triggering an initial registration to a first VPLMN to receive SOR information from the first VPLMN, according to an embodiment as disclosed in the present disclosure. In step 501, UE 200 attempts to register to the first VPLMN while operating in manual mode. If the first VPLMN accepts UE 200's registration request, UE 200 camps on the first VPLMN.

[0111] In step 502, the present embodiment includes detecting the occurrence of a SOR failure. Examples of SOR failures include determining that SOR information is missing, that the SOR information received from the first VPLMN has been tampered with, etc. The present embodiment considers the failure to receive SOR information from the first VPLMN during registration with the first VPLMN as a SOR failure. The present embodiment considers the failure to preserve the integrity of the received SOR information as a SOR failure. The present embodiment includes performing a security check to determine whether the integrity of the received SOR information has been corrupted. If the security check fails, it may be determined that the received SOR information has been tampered with by the first VPLMN. If the security check passes, the received SOR information may also be considered true SOR information. If the true SOR information is received, the SOR failure is considered resolved.

[0112] In step 503, the present embodiment includes tracking the occurrence of SOR failure. In one embodiment, UE 200 operating in manual mode can use a flag to track the occurrence of SOR failure. The SOR failure flag can be set to "1" or reset to "0". UE 200 can set the flag when it experiences a SOR failure. UE 200 can reset the flag when the SOR failure is resolved. The flag is set if UE 200 detects a SOR failure.

[0113] In one embodiment, a UE 200 operating in manual mode can track occurrences of SOR failures by maintaining a list of VPLMNs encountered by the UE 200. If the UE 200 detects a SOR failure, the first VPLMN is populated onto the list. In one embodiment, a list of "PLMNs whose registration was aborted by SOR" can be utilized to track occurrences of SOR failures.

[0114] If the embodiment triggers a PLMN search, there may be a possibility to resolve the SOR failure by other procedures while the UE 200 is operating in manual mode. If the UE 200 can detect other VPLMNs during the search and successfully registers with the detected VPLMN, the SOR information is received while operating in manual mode, because the 3GPP standard configures the UE 200 to mandatory receive SOR information from the VPLMN during registration to the VPLMN if the registration is considered successful. When receiving the SOR information from the detected VPLMN, the embodiment includes performing a security check on the received SOR information. If the security check is passed, the embodiment includes resetting a flag and / or removing the first VPLMN from the list. The SOR failure is considered resolved.

[0115] If UE 200 receives an indication from the first VPLMN that no SOR information is provided, the embodiment may reset the flag and / or remove the first VPLMN from the list. If UE 200 is unable to receive SOR information, the flag remains set and / or the first VPLMN remains populated on the list as long as UE 200 is operating in manual mode.

[0116] In step 504, the UE 200 is switched out of the manual mode and starts operating in the automatic mode. In step 505, the embodiment includes determining whether a SOR failure that occurred when the UE 200 was operating in the manual mode has been resolved. The embodiment includes checking the status (set / reset) of the list and / or flag to determine whether such an outstanding SOR failure exists. If the flag is reset and / or the UE 200 determines in step 506 that the first VPLMN is not populated on the list, the embodiment determines that there is no outstanding SOR failure. As a result, no recovery mechanism is triggered. The embodiment may trigger a PLMN selection according to normal PLMN selection priority. If the flag is set and / or the first VPLMN is determined to be populated on the list, the embodiment includes determining in step 507 that a SOR failure occurred when the UE 200 was operating in the manual mode that needs to be resolved. An outstanding SOR failure may indicate that the UE 200 needs to receive SOR information.

[0117] If there is a detected pending failure (at step 507), the embodiment includes triggering a recovery mechanism. At step 508, the embodiment includes triggering initial registration to the first VPLMN. The embodiment includes determining, at step 509, whether the initial registration is deemed successful. If the UE 200 receives SOR information from the first VPLMN during initial registration, and the received SOR information is successfully decoded, the initial registration is deemed successful. If it is determined that the initial registration to the first VPLMN is successful, then at step 510, the SOR failure is deemed resolved. The embodiment may then reset a flag and / or remove the first VPLMN from the list.

[0118] If it is determined that the initial registration with the first VPLMN was not successful, then the SOR failure is deemed to persist in step 511. An unsuccessful registration indicates that the UE 200 did not receive SOR information from the first VPLMN during initial registration or that the integrity of the SOR information received from the first VPLMN was corrupted. The flag will remain set and / or the list will continue to be populated with the first VPLMN.

[0119] This embodiment includes periodically triggering a PLMN search to detect high priority VPLMNs as specified by the HPLMN and registering to the detected VPLMNs. The UE 200 remains camped on the first VPLMN because previous attempts to receive SOR information by registering to other VPLMNs have not been successful. The first VPLMN populated in the list is deemed to have become the lowest priority (or least desirable) during the PLMN search and selection procedure (if SOR failure was encountered when the UE 200 operated in manual mode).

[0120] In step 512, the present embodiment includes determining whether a timer (which may be a first timer or a second timer) is started. The timer may be initialized by the 3GPP standard to manage PLMN scan triggering. The present embodiment may trigger a PLMN search when the timer expires. The timer may also be configured to expire after a predefined time interval.

[0121] If it is determined that the timer has been initialized, the embodiment includes determining whether the timer has expired in step 513. If it is determined that the timer has expired, the embodiment includes triggering a PLMN search in step 514. During the PLMN search, the first VPLMN and the VPLMNs that are populated in the list are considered low priority VPLMNs. The PLMN search aims to detect a high priority VPLMN and to register with the high priority VPLMN. The embodiment includes detecting the high priority VPLMN and attempting to register with the high priority VPLMN. In step 515, the embodiment includes determining whether the UE 200 can successfully register with the detected VPLMN. If the registration is determined to be successful, the SOR failure is considered resolved (step 510). The UE 200 can recover from the SOR failure by receiving accurate SOR information from the detected VPLMN if the registration is successful.

[0122] If it is determined that the registration was not successful, the SOR failure is considered to persist (step 511). Either no SOR information was received or the received SOR information was tampered with. The embodiment includes starting a new timer (step 512 "YES"). After expiration of the timer (step 513), the embodiment includes triggering a further PLMN search (step 514).

[0123] If it is determined (at step 512) that the timer has not started, the embodiment includes forcing the timer to start at step 516. Thereafter, the embodiment includes triggering a PLMN search (step 514) after expiration of the timer (step 513).

[0124] This embodiment continues to trigger PLMN searches periodically, with a periodicity of a time interval spanning from the start to the expiration of a timer. The UE 200 can recover from a SOR failure (step 510) by receiving accurate SOR information from a high priority VPLMN (step 514) that is detected during the PLMN search, which SOR information is received while registering with the detected VPLMN (step 515 “Yes”).

[0125] The embodiment of the present disclosure avoids triggering frequent PLMN searches by initializing a back-off timer that expires after a predefined time interval. This embodiment can prevent other procedures from triggering a PLMN search to resolve a SOR failure prior to the expiration of the back-off timer, or from triggering a PLMN search after the timer expires. This embodiment configures the back-off timer to ensure that a PLMN search is triggered after the timer expires while the UE 200 is camping on the first VPLMN. The back-off timer is started after the PLMN search is performed (step 514), and the UE 200 that cannot successfully register in the VPLMN will still register in the first VPLMN (if a SOR failure is encountered initially).

[0126] The various actions in flowchart 500 may be performed in the order presented, in a different order, or simultaneously. Further, in some embodiments, some actions listed in FIG.

[0127] The embodiments disclosed herein may also be embodied through at least one software program executing on at least one hardware device to perform network management functions and control the network element. The network element illustrated in FIG. 2B includes at least one of a hardware device and a combination of a hardware device and a software module.

[0128] The disclosed embodiments of the present disclosure describe a method and system for recovering from a SOR-related failure by receiving SOR information. Thus, the scope of protection extends to such a program, and it is understood that, in addition to computer readable means having a message, such computer readable storage means includes program code means for implementing one or more steps of the method when the program is executed on a server, a mobile device, or any suitable programmable device. The method may also be implemented in the preferred embodiment through or with a software program written in, for example, very high speed integrated circuit hardware description language (VHDL), other programming languages, or embodied by one or more VHDL or software modules running on at least one hardware device. The hardware device may also be any kind of portable device that can be programmed. For example, the device may further include hardware means such as, for example, an ASIC, or a combination of hardware and software means, for example, an ASIC and an FPGA, or at least one microprocessor and at least one memory in which the software modules are located. The method embodiments described in this disclosure may be implemented partly in hardware and partly in software, or alternatively, the disclosure may be implemented on different hardware devices, for example using multiple CPUs.

[0129] FIG. 6 illustrates a block diagram of an entity according to an embodiment of the present disclosure.

[0130] The entity 600 may correspond to a network function of a core network. For example, the entity 600 may be an access and mobility management function (AMF). The entity 600 may also correspond to a node of a network, a PLMN, a VPLMN or a HPLMN. The entity 600 may also be a base station. However, the entity 600 is not limited to the above examples.

[0131] 6, entity 600 may include a processor 610, a transceiver 620, and a memory 630. However, none of the illustrated components are required. Entity 600 may be implemented with more or fewer components than those illustrated in FIG 6. Furthermore, processor 610, transceiver 620, and memory 630 may be implemented as a single chip in other embodiments.

[0132] The aforementioned components will now be described in further detail.

[0133] The processor 610 may include one or more processors or other processing devices that control the proposed functions, processes and / or methods. The operations of the entity 600 are also embodied by the processor 610.

[0134] The transceiver 620 may include an RF transmitter that upconverts and amplifies a signal to be transmitted, and an RF receiver that downconverts the frequency of a received signal, although in other embodiments the transceiver 620 may be embodied with more or fewer components than those illustrated.

[0135] The transceiver 620 is coupled to the processor 610 and / or can transmit and / or receive signals. The signals may include control information and data. The transceiver 620 can also receive signals over a wireless channel and output signals to the processor 610. The transceiver 620 can transmit signals output from the processor 610 over a wireless channel.

[0136] The memory 630 may store control information or data included in signals acquired by the entity 600. The memory 630 may be coupled to the processor 610 and may store at least one instruction, protocol or parameter for the proposed functions, processes and / or methods. The memory 630 may include a read-only memory (ROM) and / or a random access memory (RAM) and / or a hard disk and / or a CD-ROM and / or a DVD and / or other storage device.

[0137] In an exemplary embodiment, entity 600 may transmit a registration accept message to the UE.

[0138] FIG. 7 illustrates a terminal (UE) according to an embodiment of the present disclosure.

[0139] Referring to Figure 7, a terminal 700 (or user equipment) may include a processor 710, a transceiver 720, and a memory 730. However, none of the illustrated components are required. The terminal 700 may be implemented with more or fewer components than those illustrated in Figure 7. Furthermore, the processor 710, the transceiver 720, and the memory 730 may be implemented as a single chip in other embodiments.

[0140] The aforementioned components will now be described in further detail.

[0141] The processor 710 may include one or more processors or other processing devices that control the functions, processes and / or methods described herein. The operations of the terminal 700 may also be implemented by the processor 710.

[0142] The transceiver 720 may include an RF transmitter that upconverts and amplifies a signal to be transmitted, and an RF receiver that downconverts the frequency of a received signal, although in other embodiments the transceiver 720 may be embodied with more or fewer components than those illustrated.

[0143] The transceiver 720 is coupled to the processor 710 and / or can transmit and / or receive signals. The signals may include control information and data. The transceiver 720 can also receive signals over a wireless channel and output signals to the processor 710. The transceiver 720 can transmit signals output from the processor 710 over a wireless channel.

[0144] The memory 730 may store control information or data included in signals acquired by the terminal 700. The memory 730 may be coupled to the processor 710 and may store at least one instruction, protocol or parameter for the proposed functions, processes and / or methods. The memory 730 may include a ROM and / or a RAM and / or a hard disk and / or a CD-ROM and / or a DVD and / or other storage device.

[0145] In an example embodiment, processor 710 is also configured to detect a steering of roaming (SOR) failure during or after registration in a first VPLMN, where the terminal may operate in a manual mode, and processor 710 is also configured to transition from the manual mode to an automatic mode and perform a PLMN selection procedure to obtain service in a second VPLMN having a higher priority than the first VPLMN based on a determination that a SOR failure has occurred.

[0146] In one embodiment, if the first VPLMN is the PLMN in which the SOR failure occurred, the first VPLMN is also considered to have the lowest priority when performing the PLMN selection procedure.

[0147] In the exemplary embodiment, terminal 700 is also still registered with the first VPLMN in which the SOR failure occurred when it transitions from manual mode to automatic mode.

[0148] In one embodiment, if the terminal 700 has an established emergency PDU session, the PLMN selection procedure may be performed after the emergency PDU session is released.

[0149] In an exemplary embodiment, processor 710 is also configured to receive, during registration with the first VPLMN, a registration accept message from the first VPLMN, the registration accept message including the SOR information.

[0150] In an exemplary embodiment, SOR failure is also detected based on the registration acceptance message.

[0151] In one embodiment, if the SOR information is missing in the registration accept message, or if a security check of the SOR information fails during registration to the first VPLMN, it may be determined that a SOR failure occurs.

[0152] In an exemplary embodiment, the processor 710 is also configured to operate in an idle mode or an RRC inactive mode prior to performing the PLMN selection procedure.

[0153] The foregoing description of the specific embodiments fully illustrates the general nature of the embodiments herein that others may easily modify and / or adapt such specific embodiments for various applications by applying current knowledge without departing from the general concept, and therefore such adaptations and modifications must and are intended to be understood as being within the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Thus, although the embodiments herein have been described in terms of preferred embodiments, those skilled in the relevant art will recognize that the embodiments herein can be modified and implemented within the scope of the embodiments as described herein.

[0154] Although the present disclosure has been described with various embodiments, various changes and modifications may be suggested to those skilled in the art. The present disclosure is intended to cover such changes and modifications that fall within the scope of the appended claims. [Explanation of symbols]

[0155] 200 user equipment 201 Processor 202 Communication Interface 203 Memory 204 Display 610 Processor 620 Transceiver 630 Memory 710 Processor 720 Transceiver 730 Memory

Claims

1. A method performed by a terminal in a wireless communication system, comprising: detecting a steering of roaming (SOR) failure in a manual mode during or after registering with a first visitor-public land mobile network (VPLMN); converting the manual mode to an automatic mode; if the SOR failure is detected in the manual mode and the manual mode is converted to the automatic mode, waiting until the terminal moves to an idle state or a radio resource control (RRC) inactive state; performing, in the automatic mode, a public land mobile network (PLMN) selection procedure to obtain service in a second VPLMN having a higher priority than the first VPLMN.

2. 2. The method of claim 1, wherein if the first VPLMN is determined to be the PLMN in which the SOR failure occurred, the first VPLMN is considered as the lowest priority while performing the PLMN selection procedure.

3. The method of claim 1 , wherein the terminal is registered with the first VPLMN in which a SOR failure occurs when the terminal switches from the manual mode to the automatic mode.

4. The method of claim 1, wherein if the terminal has an established emergency protocol data unit (PDU) session, the PLMN selection procedure is performed after the emergency PDU session is released.

5. During registration with the first VPLMN, the method further includes receiving a registration accept message from the first VPLMN, the registration accept message including SOR information; The method of claim 1 , wherein the SOR failure is detected based on the registration acceptance message.

6. 6. The method of claim 5, further comprising determining that the SOR failure occurs if the SOR information is missing in the registration accept message or if a security check of the SOR information fails during registration with the first VPLMN.

7. In a terminal operating in a wireless communication system, A transceiver; at least one processor coupled to the transceiver; The at least one processor Detecting a steering of roaming (SOR) failure in a manual mode during or after registration with a first visitor-public land mobile network (VPLMN); Converting the manual mode to an automatic mode; If the SOR failure is detected in the manual mode and the manual mode is converted to the automatic mode, waiting until the terminal moves to an idle state or a radio resource control (RRC) inactive state; The terminal performs a public land mobile network (PLMN) selection procedure to obtain service from a second PLMN having a higher priority than the first VPLMN in the automatic mode.

8. The terminal of claim 7, wherein if the first PLMN is determined to be the PLMN in which the SOR failure occurred, the first VPLMN is considered as the lowest priority while performing the PLMN selection procedure.

9. The terminal of claim 7, wherein the terminal is registered with the first VPLMN in which a SOR failure occurs when the manual mode is converted to the automatic mode.

10. The terminal of claim 7, wherein if the terminal has an established emergency protocol data unit (PDU) session, the PLMN selection procedure is performed after the emergency PDU session is released.

11. The terminal of claim 7 , wherein the at least one processor receives a registration accept message including SOR information from the first VPLMN during registration with the first PLMN, and the SOR failure is detected based on the registration accept message.

12. 12. The terminal of claim 11, wherein the at least one processor determines that the SOR failure occurs if the SOR information is missing in the registration accept message or if a security check of the SOR information fails during registration with the first VPLMN.

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