Restoring service in a radio access technology (RAT) for a multi-mode user equipment (UE)

Abstract

The present disclosure relates to resuming services in a radio access technology (RAT) for a multi-mode user equipment (UE). Some aspects of the present disclosure relate to apparatus and methods for implementing techniques to support resuming services in a radio access technology (RAT) for a multi-mode user equipment (UE). The UE may be registered to communicate in a first RAT, and the UE is in an idle mode, and the UE is in a disabled mode with respect to communications in a second RAT. Cell selection for the second RAT may be performed. A registration process may then be performed with a wireless communication system to communicate in the second RAT. Thus, the UE may receive wireless services from the wireless communication system via a base station associated with the second RAT.

Description

Technical Field

[0001] The described aspects generally relate to resuming service in a radio access technology (RAT) for a multi-mode user equipment (UE) supporting multiple RATs. Background Art

[0002] Radio access technology (RAT) is the underlying physical connection method for radio based wireless communication networks. Multimode user equipment (UE) can support multiple RATs in one device, such as Bluetooth, Wi-Fi, Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS) or Long Term Evolution (LTE). In addition, the 3rd Generation Partnership Project (3GPP) has developed a new RAT called the fifth generation (5G) new air interface (NR) RAT. Multimode UEs supporting multiple RATs can provide users with flexibility and convenience. However, it is desirable to improve the operational efficiency of multimode UEs. Summary of the invention

[0003] Some aspects of the present disclosure relate to devices and methods for implementing mechanisms to support the resumption of services in a radio access technology (RAT) for a multi-mode user equipment (UE). A multi-mode UE may communicate wirelessly in at least a first RAT and a second RAT, such as a RAT different from a fifth generation (5G) new air interface (NR) RAT and an NR RAT. NR RAT can provide more services to users, but NR networks may not be available at all times and in all circumstances. Sometimes, a UE may communicate in a first RAT while communications are disabled in a second RAT. A timer may be configured to calculate the amount of time that the UE is in a disabled mode relative to communications in a second RAT. Once the timer has expired, the UE may resume services in the second RAT. Embodiments of the present invention provide a mechanism for the UE to resume services in a second RAT when the timer expires.

[0004] Some aspects of the present disclosure relate to a multi-mode UE. The UE may include one or more transceivers and a processor communicatively coupled to the one or more transceivers. The one or more transceivers may enable the UE to communicate wirelessly in a first RAT and a second RAT. In some embodiments, the UE communicates in a first RAT of a public land mobile network (PLMN) and communicates in a second RAT of the same PLMN. In some other embodiments, the UE communicates in a first RAT of a first PLMN and communicates in a second RAT of a second PLMN different from the first PLMN. In some examples, the first PLMN has a first priority, and the second PLMN has a second priority equal to or higher than the first priority. In addition, a protocol stack may be operated on the UE by a processor. The protocol stack may include a non-access stratum (NAS) layer and an access stratum (AS) layer, and the AS layer includes multiple sublayers, such as a radio resource control (RRC) layer.

[0005] According to some aspects, a processor of the UE may be configured to determine, through a NAS layer of the protocol stack, that the UE is registered for communication in a first RAT and that the UE is in an idle mode. The processor may be further configured to determine, through the NAS layer, that a timer has expired, wherein the timer is configured to calculate the amount of time the UE is in a disabled mode relative to communication in a second RAT. In addition, in response to a determination that the UE is in an idle mode in the first RAT and that the timer has expired, the processor may be configured to send a request to an RRC layer of the protocol stack through the NAS layer to perform cell selection for the second RAT. The processor may then be configured to receive, through the NAS layer and from the RRC layer, an indication that the cell selection has been successfully performed to communicate in the second RAT. The RRC layer sends the indication after listening to system information from a base station associated with the second RAT and selecting a base station for wireless communication in the second RAT. In some examples, selecting a base station for wireless communication in the second RAT may include selecting a base station by using a previously stored frequency list or by performing a band search of multiple frequency bands.

[0006] In addition, the processor may be configured to perform a registration procedure with a wireless communication system including a base station to communicate in a second RAT through the NAS layer and in response to receiving an indication that cell selection has been successfully performed. After performing the registration procedure, the processor may be configured to receive wireless services from the wireless communication system through the base station associated with the second RAT. Therefore, the UE has resumed service in the second RAT.

[0007] In addition, when the UE is in a mode other than the idle mode, the processor of the UE may be configured to perform wireless communication in the first RAT so that normal service of the UE in the first RAT will not be interrupted. In addition, when the NAS layer does not receive an indication from the RRC layer that cell selection has been successfully performed to communicate in the second RAT, the processor may be configured to continue registration to communicate in the first RAT.

[0008] According to some aspects, the first RAT may include a Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), or a Global System for Mobile Communications (GSM) Edge Radio Access Network (GERAN), while the second RAT may include an NR Next Generation Radio Access Network (NG-RAN). In some examples, the first RAT may be a lower priority RAT than the second RAT. In some examples, one or more transceivers may be configured to enable the UE to communicate wirelessly in a Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN). The processor may be further configured to select an LTE base station for wireless communication in an LTE E-UTRAN, communicate with the LTE base station in the LTE E-UTRAN, and select an NR base station for wireless communication in the NG-RAN after communicating with the LTE base station. The timer may be configured to calculate the amount of time that the UE is in a disabled mode relative to communication in the NG-RAN or LTE E-UTRAN.

[0009] Some aspects of the present disclosure relate to a method performed by a UE. The method includes determining that a UE is registered to communicate in a first RAT and that the UE is in an idle mode. The method also includes determining that a timer has expired, wherein the timer is configured to calculate an amount of time that the UE is in an disabled mode relative to communications in a second RAT, the second RAT being different from the first RAT. In addition, in response to a determination that the UE is in an idle mode in the first RAT and that the timer has expired, the method includes performing cell selection for the second RAT. Performing cell selection may include listening to system information from a base station associated with the second RAT, and selecting the base station for wireless communication in the second RAT. In response to successfully performing cell selection for the second RAT, the method includes performing a registration process with a wireless communication system to communicate in the second RAT. After performing the registration process, the method includes receiving wireless service from the wireless communication system via a base station associated with the second RAT.

[0010] Some aspects of the present disclosure relate to a non-transitory computer-readable medium storing instructions. When executed by a processor of a UE, the instructions stored in the non-transitory computer-readable medium cause the UE to perform various operations. These operations include determining that the UE is registered to communicate in a first RAT and that the UE is in an idle mode. These operations also include determining that a timer has expired, wherein the timer is configured to calculate the amount of time that the UE is in a disabled mode relative to communications in a second RAT, the second RAT being different from the first RAT. In addition, in response to a determination that the UE is in an idle mode in the first RAT and the timer has expired, the operations include performing cell selection for the second RAT. In response to successfully performing cell selection for the second RAT, the operations include performing a registration process with a wireless communication system to communicate in the second RAT. After performing the registration process, the operations include receiving wireless services from the wireless communication system via a base station associated with the second RAT.

[0011] The present invention is provided for the purpose of illustrating some aspects only, so as to provide an understanding of the subject matter described herein. Therefore, the above-mentioned features are only examples and should not be understood as narrowing the scope or essence of the subject matter in the present disclosure. Other features, aspects and advantages of the present disclosure will become apparent from the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and enable those skilled in the relevant art to make and use the present disclosure.

[0013] Figure 1 A wireless system including a multi-mode user equipment (UE) configured to resume service in one of a plurality of radio access technologies (RATs) is shown in accordance with some aspects of the present disclosure.

[0014] FIG. 2A to FIG. 2B A block diagram of a UE for performing the functions described herein is shown according to some aspects of the present disclosure.

[0015] Figure 3 An example method performed by a multi-mode UE to resume service in one of a plurality of RATs in accordance with some aspects of the present disclosure is shown.

[0016] Figures 4 to 6 An example sequence diagram illustrating operations performed by a multi-mode UE to resume service in one of multiple RATs is shown in accordance with some aspects of the present disclosure.

[0017] Figure 7is an exemplary computer system for implementing some aspects or portions of the disclosure provided herein.

[0018] The present disclosure is described with reference to the accompanying drawings. In the drawings, generally, the same reference numerals represent identical or functionally similar elements. Also, generally, the leftmost digit of a reference numeral identifies the drawing in which the reference numeral first appears. DETAILED DESCRIPTION

[0019] A multi-mode user equipment (UE) may support multiple radio access technologies (RATs) such as Bluetooth, Wi-Fi, Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), or Fifth Generation (5G) New Radio (NR) for wireless communications. NR technology may provide users with services and applications with improved user experience. However, sometimes, the NR network may not be available, and the UE may temporarily disable the NR RAT, which may be referred to as N1 mode disabling. For example, when the maximum registration attempts have been reached, when Internet Protocol (IP) Multimedia Subsystem (IMS) voice coverage NR is not available in the registration area, or when the UE registration is rejected due to network congestion or other abnormal rejection reasons, the UE may temporarily disable the NR RAT. When a RAT may be disabled, some more examples and details may be found in some standard documents such as 3GPP 24.501, section 4.9.2, section 5.5.1.3.7, or other similar references known to those of ordinary skill in the art. In some examples, the UE may also disable the LTERAT instead of disabling the NR RAT.

[0020] According to some aspects, when the NR RAT is disabled for various reasons, the UE may start a timer specific to the specific implementation to calculate the amount of time the UE is in a disabled mode of the NR RAT. When the NR RAT is disabled, the UE is in a disabled mode. In some examples, the timer may have a default value of 720 seconds. The timer may also have other values. At the same time, the UE may attempt to select and register on a different RAT (such as LTE, UMTS, or GSM). When the timer expires, the UE may restart the NR RAT. When the UE restarts the NR RAT when the timer expires, the UE may perform an NR cell reselection procedure to enable the NR RAT and obtain service. Such a procedure may be referred to as resuming service in the NR RAT. In some other examples, the UE may use NR cell reselection to reside and register on the NR-RAT.

[0021] According to some aspects, if the UE is registered to the LTE RAT when the NR RAT is restarted, the UE may perform cell reselection based on the reselection configuration defined by the LTE network to resume service in the NR RAT. However, if the UE is registered to the GSM RAT or UMTS RAT when the NR RAT is restarted, the UE cannot perform direct cell reselection to move from the GSM RAT or UMTS RAT to the NR RAT because the 3GPP specifications have not yet defined such direct interworking between GSM / UMTS and NR RAT. Some current systems may return to NR RAT service by reselecting to the LTE RAT and then reselecting from the LTE RAT to the NR RAT. If the LTE cell is not available at this time or the LTE RAT is disabled, NR reselection will not be triggered. The UE may remain on the GSM / UMTS RAT for a longer period of time in an area with good NR coverage, which may result in a degraded user experience and customer dissatisfaction.

[0022] The embodiments herein show a solution to improve NR RAT service recovery via a UE active attempt to trigger background NR cell selection or public land mobile network (PLMN) selection when some conditions are met, such as when the N1 mode restart timer has expired, when the N1 mode is restarted, and when the UE is registered on a GSM RAT or UMTS RAT. When restarting the N1 mode, if the UE is registered on a GSM RAT or UMTS RAT on a PLMN in which the N1 mode capability for 3GPP access is disabled, the UE may trigger background cell selection on an NR RAT on the same PLMN. If the UE is registered on a GSM RAT or UMTS RAT on a PLMN that is different from the PLMN in which the N1 mode capability for 3GPP access is disabled, the UE may trigger background PLMN selection to resume service on the NR RAT. The term background NR cell selection or background PLMN selection refers to the condition under which the UE performs NR cell selection or PLMN selection when in idle mode in the currently registered RAT, such as a GSM RAT or UMTS RAT. When the UE is not performing active data transmission or signaling, the idle mode may refer to some other mode so that the service for active applications will not be interrupted. If the UE is in connected mode, the UE waits to return to idle mode when no active data transmission occurs.

[0023] Therefore, the embodiments of the present invention can recover or acquire NR RAT services from the GSM / UMTS registration state regardless of the availability of LTE cells or even when the LTE RAT is disabled. The embodiments of the present invention can recover NR RAT services without going through a two-step reselection and registration process from UMTS / GSM RAT to LTE RAT, and further from LTE RAT to NR RAT. Therefore, the embodiments of the present invention can avoid additional signaling for the two-step reselection and registration process. NR cell selection can be performed in the background to avoid any service interruption on GSM / UMTS RAT services. Therefore, the user experience of staying on GSM / UMTS RAT will not be affected. The UE may not remain on the GSM / UMTS RAT in the NR coverage area, which helps to improve the user experience because many NR-based applications cannot be supported on the lower bandwidth of GSM / UMTS RAT.

[0024] Figure 1 A wireless system 100 including a multi-mode UE (e.g., UE 101) configured to resume service in one of a plurality of RATs according to some aspects of the present disclosure is shown. The wireless system 100 is provided for illustration purposes only and is not limiting of the disclosed aspects. The wireless system 100 may include, but is not limited to, UE 101, base stations 111, 113, 115, 117, and 119, a public land mobile network (PLMN) 103, PLMN 105, and various core networks (such as core network 102, core network 104, core network 106, core network 108, and core network 110, all communicatively coupled to core network 120).

[0025] According to some aspects, base station 111, base station 112, base station 113, base station 115, base station 117, and base station 119 may be fixed stations or mobile stations. Base station 111, base station 112, base station 113, base station 115, base station 117, and base station 119 may also be referred to by other names, such as base transceiver system (BTS), access point (AP), transmission / reception point (TRP), evolved node B (eNB), next generation node B (gNB), 5G node B (NB), or some other equivalent terms. In some examples, base station 111, base station 112, base station 113, base station 115, base station 117, and base station 119 may be interconnected to each other and / or to other base stations or network nodes in the network via various types of backhaul interfaces (such as direct physical connections, virtual networks, etc.) (not shown).

[0026] According to some aspects, UE 101 may be a multi-mode UE supporting multiple RATs. UE 101 may be stationary or mobile. UE 101 may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop, a desktop computer, a cordless phone, a wireless local loop station, a wireless sensor, a tablet, a camera, a video surveillance camera, a gaming device, a netbook, an ultrabook, a medical device or equipment, a biometric sensor or device, a wearable device (a smart watch, smart clothing, smart glasses, a smart wristband, smart jewelry such as a smart ring or a smart bracelet), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicle component, a smart meter, an industrial manufacturing equipment, a global positioning system device, an Internet of Things (IoT) device, a machine type communication (MTC) device, an evolved or enhanced machine type communication (eMTC) device, or any other suitable device configured to communicate via a wireless medium. For example, MTC and eMTC devices may include robots, drones, location tags, etc.

[0027] According to some aspects, base station 111 may be a UMTS base station, and UE 101 may communicate wirelessly with base station 111 in RAN1 in a first RAT, which may be a UMTS terrestrial radio access network (UTRAN). Base station 111 and core network 102 may form a UMTS wireless communication system. In addition, base station 113 may be an NR base station, and UE 101 may communicate wirelessly with base station 113 in RAN2 in a second RAT, which may be a next generation radio access network (NG-RAN). Base station 113 and core network 104 may form an NR wireless communication system. In addition, base station 111 and GERAN, base station 113 and NG-RAN are managed by the same PLMN 103. PLMN 103 may have priority 107. Base station 112 may be a GSM base station, and UE 101 may communicate wirelessly with base station 112 in RAN6 in a RAT, which may be a GSM edge radio access network (GERAN). Base station 112 and core network 114 may form a GSM wireless communication system.

[0028] According to some aspects, base station 115 may be a UMTS base station, and UE 101 may communicate wirelessly with base station 115 in RAN3 in a RAT, which may be a UMTS terrestrial radio access network (UTRAN). Base station 115 and core network 106 may form a UMTS wireless communication system. In addition, base station 117 may be an LTE base station, and UE 101 may communicate wirelessly with base station 117 in RAN4 in a RAT, which may be an LTE evolved UTRAN (E-UTRAN). Base station 117 and core network 108 may form an LTE wireless communication system. In addition, base station 119 may be an NR base station, and UE 101 may communicate wirelessly with base station 119 in RAN5 in a RAT, which may be an NG-RAN. Base station 119 and core network 110 may form an NR wireless communication system. In addition, base station 115 and UTRAN, base station 117 and E-UTRAN, and base station 119 and NG-RAN are managed by PLMN 105. PLMN 105 may have priority 109.

[0029] According to some aspects, UE 101 may include timer 131, and UE 101 may be in state or mode 133. For example, mode 133 may be an enabled mode, a disabled mode, an idle mode, or some other mode. Timer 131 may be used to calculate the amount of time that UE 101 has been in a mode (such as a disabled mode) with respect to communications in the RAT.

[0030] FIG. 2A to FIG. 2B A block diagram of a UE 101 for performing the functions described herein is shown according to some aspects of the present disclosure.

[0031] Figure 2A A block diagram of a UE 101 is shown with an antenna panel 217, which includes one or more antenna elements, such as an antenna element 219 coupled to a transceiver 203 and controlled by a processor 201. In detail, the transceiver 203 may include a radio frequency (RF) circuit 216, a baseband transmit circuit 212, and a baseband receive circuit 214. The RF circuit 216 may include a plurality of parallel RF chains for performing one or more of a transmit or receive function, each RF chain connected to one or more antenna elements in the antenna panel. In addition, the processor 201 may be communicatively coupled to a memory device 211, which is further coupled to the transceiver 203. There may be multiple transceivers, not shown, that may be similar to the transceiver 203.

[0032] In some examples, UE 101 uses RF circuit 216 to transmit and receive signals or data. Memory device 211 can store mode 133 and exemplary protocol stack 213. For example, processor 201 can store mode 133 and operate protocol stack 213. Details of protocol stack 213 are described in Figure 2B . The memory device 211 may include instructions that, when executed by the processor 201, perform functions to restore service in one of the multiple RAT technologies. Alternatively, the processor 201 may be "hard-coded" to perform the functions described herein.

[0033] Figure 2B More details of the protocol stack 213 are shown. The protocol stack 213 may include a transport (TCP) layer 223, an IP layer 225, a non-access stratum (NAS) layer 227, an access stratum (AS) layer 229, and a channel 220. The AS layer 229 may include multiple sublayers, such as an RRC layer 231, a packet data convergence protocol (PDCP) layer 233, a radio link control (RLC) layer 235, a medium access control (MAC) layer 237, and a physical (PHY) layer 239.

[0034] In some examples, one or more transceivers (e.g., transceiver 203) may enable UE 101 to communicate wirelessly in a first RAT and a second RAT (such as a GSM RAT, a UMTS RAT, an LTE RAT, or an NR RAT). Processor 201 may be configured to implement timer 131 and perform various operations related to resuming services in one of the multiple RATs. For example, processor 201 may determine, via NAS layer 227, that timer 131 has expired, wherein timer 131 is configured to calculate the amount of time that UE 101 has been in a disabled mode with respect to communications in a second RAT. In addition, in response to a determination that UE 101 is in an idle mode in the first RAT and timer 131 has expired, processor 201 may send a request to RRC layer 231 via NAS layer 227 to perform cell selection for the second RAT. Processor 201 may then receive, via NAS layer 227 and from RRC layer 231, an indication that the cell selection has been successfully performed to communicate in the second RAT. The RRC layer 231 may send the indication after listening to system information from a base station associated with the second RAT and selecting a base station for wireless communication in the second RAT. In some examples, selecting a base station for wireless communication in the second RAT may include selecting a base station by using a previously stored frequency list or by performing a band search of multiple frequency bands.

[0035] In addition, the processor 201 may perform a registration procedure with the wireless communication system including the base station to communicate in the second RAT through the NAS layer 227 and in response to receiving an indication that the cell selection has been successfully performed. After performing the registration procedure, the processor 201 may receive wireless services from the wireless communication system through the base station associated with the second RAT.

[0036] In addition, when the UE is in a mode other than the idle mode, the processor 201 may perform wireless communication in the first RAT so that normal service of the UE 201 in the first RAT will not be interrupted. In addition, when the NAS layer 227 does not receive an indication from the RRC layer 231 that cell selection has been successfully performed to communicate in the second RAT, the processor 201 may continue to be registered to communicate in the first RAT.

[0037] According to some aspects, the first RAT may include UTRAN or GERAN, while the second RAT may include NG-RAN. In some examples, transceiver 203 may enable UE 101 to communicate wirelessly in LTE E-UTRAN. Processor 201 may select an LTE base station for wireless communication in LTE E-UTRAN, communicate with the LTE base station in LTE E-UTRAN, and select an NR base station for wireless communication in NG-RAN after communicating with the LTE base station. Timer 131 may calculate an amount of time that the UE has been in disabled mode with respect to communication in NG-RAN or LTE E-UTRAN.

[0038] Figure 3 An exemplary method 300 performed by a multi-mode UE to restore services in one of multiple RATs according to some aspects of the present disclosure is shown. The method 300 may be performed by the UE 101, such as Figure 1 and FIG. 2A to FIG. 2B For example, the functions of method 300 may be executed by processor 201 or caused by processor 201.

[0039] At 302, UE 101 may determine to register UE 101 to communicate in a first RAT, and UE 101 is in idle mode. For example, UE 101 may determine to register UE 101 to communicate in a first RAT, which is a GSM RAT in GERAN RAN1 including base station 111, such as Figure 1UE 101 is in idle mode. UE 101 is a multi-mode UE that can communicate in a first RAT and a second RAT, the first RAT being a GSM RAT in a GERAN RAN1 and the second RAT being an NR RAT in a NG-RAN RAN2. For various reasons, UE 101 may be disabled to communicate in the second RAT in RAN2.

[0040] At 304, UE 101 may determine that a timer has expired, wherein the timer is configured to calculate an amount of time that UE 101 has been in a disabled mode with respect to communications in a second RAT that is different from the first RAT. For example, UE 101 may determine that timer 131 has expired, wherein timer 131 may calculate an amount of time that UE 101 has been in a disabled mode with respect to communications in an NR RAT in RAN2. In addition, UE 101 may determine that the second RAT in RAN2 has been enabled after expiration of timer 131.

[0041] At 306, in response to the determination that the UE is in idle mode in the first RAT and the timer has expired, UE 101 may perform cell selection for the second RAT. For example, when it is determined that UE 101 is in idle mode in the GSM RAT and timer 131 has expired, UE 101 may perform cell selection for the NR RAT to resume service in the NR RAT in RAN2. In some examples, the cell selection may be performed by listening to system information from base station 113 and selecting base station 113 for wireless communication in the NR RAT.

[0042] In response to successfully performing cell selection for the second RAT, UE 101 may perform a registration procedure with the wireless communication system to communicate in the second RAT at 308. For example, in response to successfully performing cell selection for the NR RAT by selecting base station 113 as a serving base station, UE 101 may perform a registration procedure with the wireless communication system including base station 113 to communicate in the NR RAT.

[0043] At 309, after performing the registration process, UE 101 can receive wireless services from the wireless communication system through the base station associated with the second RAT. For example, after performing the registration process, UE 101 can receive wireless services from the wireless communication system through the base station 113 in the NR RAT.

[0044] Figures 4 to 6 An example sequence diagram illustrating operations performed by a multi-mode UE to resume service in one of multiple RATs is shown in accordance with some aspects of the present disclosure. Figures 4 to 6 The sequence diagram shown could be Figure 3An example of method 300 is shown.

[0045] like Figure 4 As shown, sequence diagram 400 illustrates operations performed by UE 101 to resume services in one of a plurality of RATs. Operations are performed between UE 101, 3G system 402, and 5G system 404. 3G system 402 may be an example of UMTS RAN1 including base station 111 and core network 102. 5G system 404 may be an example of NR RAN2 including base station 113 and core network 104. Both 3G system 402 and 5G system 404 may be coupled to the same PLMN, such as PLMN 103.

[0046] At 401, the UE 101 may disable N1 mode communications in the NR RAT and the 5G system 404. At 403, the UE 101 may start a timer 131 to calculate the amount of time that the UE 101 has been in a disabled mode with respect to communications in the NR RAT. In an embodiment, the timer 131 may be started simultaneously or nearly simultaneously with the disabling of N1 mode communications in the NR RAT and the 5G system 404. At 405, the UE 101 may select a base station 111 and register with the 3G system 402 in the UMTS RAT. At 407, the NAS layer 227 of the UE 101 may determine that the timer 131 has expired. At 409, the NAS layer 227 of the UE 101 may determine to restart the N1 mode to communicate with the 5G system 404 in the NR RAT. The NAS layer 227 may further detect that the UE 101 is in an idle mode in the UMTS RAT. The operations performed at 401 to 409 are examples of the operations performed at 302 and 304 as described for method 300 .

[0047] At 411, in response to a determination that the UE 101 is in idle mode in the UMTS RAT and the timer 131 has expired, the NAS layer 227 may send a request to the RRC layer 231 to perform cell selection for the NR RAT. At 412, the RRC layer 231 may listen to system information from a base station of the NR RAT (e.g., the base station 113), and select the base station 113 for wireless communication in the NR RAT and the 5G system 404. The operations performed at 411 and 412 are examples of the operations performed at 306 as described for the method 300. In addition, in an embodiment, when the UE 101 is in idle mode in the UMTS RAT during an idle discontinuous reception (DRX) duration, the operations at 411 and 412 are performed, so that the service in the UMTS RAT is not interrupted, and the operations at 411 and 412 are performed in the background of the UMTS RAT. For example, paging and other activities of the UMTS RAT are not interfered. Alternatively, when the UE 101 is in a mode other than the idle mode, the UE 101 may continue to perform wireless communications in the UMTS RAT and the 3G system 402 .

[0048] At 414, the NAS layer 227 may receive an indication from the RRC layer 231 that cell selection has been successfully performed to communicate in the NR RAT. At 416, the NAS layer 227 may perform a registration procedure with the 5G system 404 to communicate in the NR RAT. The operations performed at 414 and 416 are examples of the operations performed at 308 as described by the method 300. Alternatively, when cell selection has not been successfully performed to communicate in the NR RAT, the UE 101 may remain registered with the 3G system 402 on the UMTS RAT.

[0049] At 418, assuming successful registration with the 5G system 404, the NAS layer 227 can receive wireless services from the 5G system 404 through the base station 113 in the NR RAT. The operations performed at 418 are examples of the operations performed at 309 as described in method 300. Since the UE 101 can receive wireless services from the 5G system 404 through the base station 113 in the NR RAT, services in the NRRAT on the UE 101 have been resumed.

[0050] According to some aspects, the operations shown in sequence diagram 400 are for example only and are not limiting. For example, in some examples, 3G system 402 may be replaced by a 2G GSM system. In addition, in addition to 3G system 402 and 5G system 404, there may be more systems, such as an LTE system included in wireless system 100.

[0051] According to some aspects, the operations shown in sequence diagram 400 may be applicable to various situations. For example, in one case, UE 101 may disable N1 mode in NR RAT on Home PLMN and camp on LTE RAT, but the TAU or ATTACH process on LTE RAT is unsuccessful. In other similar cases, when the voice-centric device cannot find voice service on LTE, the UE will disable LTE RAT (E-UTRA capability). Similarly, on NR RAT, when the voice-centric device cannot find voice service on NR RAT, the UE will disable NR RAT. Then, UE 101 may camp on GSM RAT or UMTS RAT of Home PLMN. When the N1 mode disable timer expires, since UE-UTRA capability is disabled, UE 101 restarts N1 mode and the UE remains camped on GSM RAT or UMTS RAT even when NR RAT is enabled. In another case, UE 101 may disable N1 mode in NR RAT on Home PLMN, and Home PLMN does not have LTE RAT deployed at that location. Therefore, UE 101 camps on the GSM RAT or UMTS RAT of the Home PLMN. When the N1 mode disable timer expires, since the LTE RAT is not deployed, UE 101 restarts the N1 mode and remains camped on the GSM RAT or UMTS RAT even when the NR RAT is enabled. The described situation is an example of the operations performed at 401, 403, and 405.

[0052] like Figure 5 As shown, sequence diagram 500 illustrates operations performed by UE 101 to resume service in one of a plurality of RATs. Operations are performed between UE 101, 3G system 502, 5G system 504, and 3G system 508. 3G system 502 may be an example of UMTS RAN1 including base station 111 and core network 102. 5G system 504 may be an example of NR RAN2 including base station 113 and core network 104. Both 3G system 502 and 5G system 504 may be coupled to the same PLMN, such as PLMN 103. In addition, 3G system 508 may be an example of UMTS RAN3 including base station 115 coupled to PLMN 105 and core network 106. Some operations illustrated in sequence diagram 500 may be similar to Figure 4 The operation shown.

[0053] At 501, UE 101 may disable N1 mode communications in NR RAT and 5G system 504. At 503, UE 101 may start timer 131 to calculate the amount of time that UE 101 has been in a disabled mode with respect to communications in NR RAT. In an embodiment, timer 131 may be started simultaneously or nearly simultaneously with the disabling of N1 mode communications in NR RAT of 5G system 504.

[0054] At 525, UE 101 may first select base station 111 and register with 3G system 502 in the UMTS RAT. However, the operation at 525 may not be successful. Then, at 526, UE 101 may select base station 115, register with 3G system 508 in the UMTS RAT in RAN3, and camp on 3G system 508. 3G system 508 belongs to PLMN 105, which is different from PLMN 103 coupled to 5G system 404. In some examples, PLMN 103 may have a priority equal to or higher than PLMN 105.

[0055] At 507, the NAS layer 227 of the UE 101 may determine that the timer 131 has expired. At 509, the NAS layer 227 of the UE 101 may determine to restart the N1 mode to communicate with the 5G system 504 in the NR RAT. The NAS layer 227 may further detect that the UE 101 is in an idle mode in the UMTS RAT.

[0056] At 511, in response to a determination that the UE 101 is in an idle mode in the UMTS RAT and the timer 131 has expired, the NAS layer 227 may send a request to the RRC layer 231 to perform cell selection for the NR RAT. At 512, the RRC layer 231 may listen to system information from a base station (e.g., the base station 113) of the NR RAT, and select the base station 113 for wireless communication in the NR RAT and the 5G system 504. The RRC layer 231 may select the base station 113 by listening to a plurality of base stations managed by the PLMN 103, and select the base station 113 based on some predetermined criteria on the PLMN 103 using an earlier stored frequency list or by performing a frequency band search. Alternatively, when the UE 101 is in a mode other than the idle mode, the UE 101 may continue to perform wireless communication in the UMTS RAT and the 3G system 508.

[0057] At 514, the NAS layer 227 may receive an indication from the RRC layer 231 that cell selection has been successfully performed to communicate in the NR RAT. At 516, the NAS layer 227 may perform a registration procedure with the 5G system 504 to communicate in the NR RAT. Alternatively, when cell selection has not been successfully performed to communicate in the NR RAT, the UE 101 may remain registered with the 3G system 508 on the UMTS RAT. At 518, assuming successful registration with the 5G system 504, the NAS layer 227 may receive wireless services from the 5G system 504 through the base station 113 in the NR RAT. Since the UE 101 can receive wireless services from the 5G system 504 through the base station 113 in the NR RAT, the services in the NR RAT on the UE 101 have been resumed.

[0058] According to some aspects, the operations shown in sequence diagram 500 are for example only and are not limiting. For example, in some examples, 3G system 502 may be a GSM (2G) system instead of a UMTS (3G) system. In addition, in addition to 3G system 502 and 5G system 504, there may be more systems, such as an LTE system included in wireless system 100.

[0059] According to some aspects, the operations shown in sequence diagram 500 may be applicable to various situations. For example, in one situation, UE 101 may disable N1 mode in NR RAT on VPLMN-1 (e.g., PLMN 103) (roaming situation). Then, UE 101 may find a base station managed by a different VPLMN-2 (e.g., PLMN 105) and camp on the base station on LTE RAT, and the TAU procedure on LTE RAT is successful. When the N1 mode disable timer of PLMN 103 expires, the UE continues to remain camped on PLMN 105 even when the UE can find service (NR RAT) on PLMN 103. If VPLMN-1 (e.g., PLMN 103) has a higher priority than VPLMN-2 (e.g., PLMN 105), UE 101 will wait for the high priority PLMN (HPPLMN) search timer to camp on VPLMN-1, where the UE 101 will camp on VPLMN-1 based on the SIM EF-EF HPPLMNThe duration of the higher priority PLMN search timer read, the HPPLMN search timer may be about at least 6 minutes or longer (typically about 30 minutes or longer, calculated in multiples of 6 minutes). Another case may be similar to the above case, except that UE 101 camps on a UMTS RAT or a GSM RAT on VPLMN-2 instead of an LTE RAT. Another case may be similar to the above case, except that no priority relationship is defined between VPLMN-1 and VPLMN-2. Therefore, the UE may not start the HPPLMN retrieval timer. The operations shown in sequence diagram 500 may be applicable to other cases, such as cases similar to the above case, except that UE 101 camps on an LTE RAT on VPLMN-1 and the LTE RAT is disabled by UE 101 instead of disabling the NR RAT.

[0060] like Figure 6 As shown, sequence diagram 600 illustrates operations performed by UE 101 to resume service in one of a plurality of RATs. Operations are performed between UE 101, 3G system 602, 5G system 604, and LTE system 606. 3G system 602 may be an example of UMTS RAN 3 including base station 115 and core network 106. 5G system 604 may be an example of NR RAN 5 including base station 119 and core network 110. LTE system 606 may be an example of LTE RAN 4 including base station 117 and core network 108. 3G system 602, 5G system 604, and LTE system 606 may be coupled to the same PLMN, such as PLMN 105. Some operations illustrated in sequence diagram 600 may be similar to Figures 4 to 5 The operation shown.

[0061] At 601, UE 101 may disable LTE E-UTRA communications in the LTE RAT with the LTE system 606. For example, UE 101 may temporarily disable the LTE RAT when maximum connection attempts have been reached, when IMS voice coverage LTE is not available in the registration area, or when UE registration is rejected due to network congestion, load resulting in temporary failure, or other abnormal rejection reasons.

[0062] At 603, UE 101 may start timer 131 to calculate the amount of time that UE 101 has been in disabled mode with respect to communication in LTE RAT. In an embodiment, timer 131 may be started simultaneously or nearly simultaneously with the disablement of communication in LTE RAT associated with LTE system 606. When timer 131 expires, UE 101 may restart LTE RAT. During the time when LTE RAT is disabled, at 605, UE 101 may select base station 115 and register with 3G system 602 in UMTS RAT. In addition, during the time when LTE RAT is disabled, if NR cell is available, UE 101 cannot perform direct cell reselection to move from GSM / UMTS RAT to NR RAT, because current 3GPP specifications have not yet defined such direct intercommunication between GSM / UMTS and NR RAT. The only way to return to NR RAT service defined in the current system is to reselect to LTE RAT and then reselect from LTE RAT to NR RAT. Since LTE RAT is disabled, NR reselection will not be triggered. Even when NR services are available in the coverage area, the UE 101 may remain camped on the GSM / UMTS RAT for a long period of time, resulting in a degraded user experience and customer dissatisfaction.

[0063] According to some aspects, the operations shown in sequence diagram 600 may be applicable to various situations. For example, in one situation, UE 101 may disable LTE RAT and E-UTRA capabilities on the Home PLMN. UE 101 cannot camp on an NR cell, but is registered on the UMTS RAT or GSM RAT of the Home PLMN. Under mobility conditions, UE 101 remains camped on the UMTS / GSM RAT even when an NR cell becomes available (because the E-UTRA capability is disabled). In another situation, UE 101 may disable LTE RAT and E-UTRA capabilities on the Home PLMN, UE 101 cannot camp on any NR / UMTS / GSM cell on the Home PLMN, and UE 101 camps and registers on the UMTS RAT or GSM RAT of the VPLMN. Under mobility conditions, UE 101 remains camped on the UMTS / GSM RAT on the VPLMN (because the E-UTRA capability is disabled) even when an NR cell becomes available on the HPLMN.

[0064] The embodiments herein illustrate operations to recover NR RAT services via a UE active attempt to trigger background NR cell selection or PLMN selection when LTE RAT and E-UTRA capabilities are disabled. When E-UTRA capabilities are disabled and the UE is registered in idle mode on a GSM / UMTS RAT, if the UE is registered on a GSM / UMTS RAT on a PLMN where the E-UTRA capabilities for 3GPP access are disabled, the UE may trigger background cell selection on the NR RAT on that PLMN. If the UE is registered on GSM / UMTS on a different PLMN than the one where the E-UTRA capabilities for 3GPP access are disabled, the UE may trigger background PLMN selection to obtain services on the NR RAT. Details of some of the operations are shown below.

[0065] At 609, NAS layer 227 of UE 101 may determine that UE 101 is in idle mode in UMTS RAT. The operation at 609 may be performed after LTE RAT has been disabled and does not need to wait until timer 131 expires. Therefore, the operation at 609 is different from Figures 4 to 5 The operation described.

[0066] At 611, in response to a determination that UE 101 is in an idle mode in the UMTS RAT, NAS layer 227 may send a request to RRC layer 231 to perform cell selection for the NR RAT. At 612, RRC layer 231 may listen to system information from a base station of the NR RAT (e.g., base station 119), and select base station 119 for wireless communication in the NR RAT and the 5G system 604. Alternatively, when UE 101 is in a mode other than the idle mode, UE 101 may continue to perform wireless communication in the UMTS RAT and the 3G system 602.

[0067] At 614, the NAS layer 227 may receive an indication from the RRC layer 231 that cell selection has been successfully performed to communicate in the NR RAT. At 616, the NAS layer 227 may perform a registration procedure with the 5G system 604 to communicate in the NR RAT. Alternatively, when cell selection has not been successfully performed to communicate in the NR RAT, the UE 101 may remain registered with the 3G system 602 on the UMTS RAT. At 618, the NAS layer 227 may receive wireless services from the 5G system 604 through the base station 119 in the NR RAT. Since the UE 101 can receive wireless services from the 5G system 604 through the base station 119 in the NR RAT, services in the NR RAT on the UE 101 have been resumed.

[0068] According to some aspects, the operations shown in sequence diagram 600 are for example only and are not limiting.For example, in some examples, 3G system 602 may be replaced by a 2G GSM system.

[0069] Figures 4 to 6 The operation of resuming service for NR RAT when N1 mode is disabled or LTE RAT is disabled is shown. The embodiments herein show the operation of resuming NR RAT service via UE active attempt to trigger background NR cell selection or PLMN selection when E-UTRA capability is disabled. Similar operations may be performed when the packet switching (PS) domain is disabled.

[0070] The UE may disable the PS domain in certain circumstances, such as when registration is rejected. In such circumstances, the UE may disable the PS domain because camping for normal services is not allowed, but may camp on a circuit switching (CS) domain RAT, such as a GSM RAT and UMTS RAT used only for CS services. Before the T3245 timer runs, the UE is only allowed to access "limited services" on the PS RAT. When the timer T3245 expires, the UE may consider the PS domain valid and may camp on the NR / LTE RAT. When the PS domain is disabled, the UE can only register on the UMTS / GSM RAT on the same or any PLMN to receive CS domain services for voice calls only. After the T3245 timer expires and the PS domain is restarted, if the NR cell is available, the UE cannot perform direct cell reselection to move from the GSM / UMTS RAT to the NR RAT. In good NR coverage, the UE may remain camped on the GSM / UMTS RAT for a longer period of time, resulting in a degraded user experience and customer dissatisfaction. If an LTE RAT exists in this location, the UE will have to first register with LTE and then reselect to the NR RAT, causing the UE to take more time to resume NR service.

[0071] If the UE is camped in service on UMTS RAT or GSM RAT or foreground NR cell selection, if the UE is camped in "limited service" or PLMN selection, the embodiments of this document may perform operations for NR RAT service recovery in the case where the UE actively attempts to trigger background NR cell selection. When the T3245 timer expires, the UE may trigger background NR cell selection or foreground NR cell selection, and the PS domain is considered "valid" for PS services again. The foreground search can be performed without the UE needing to listen to the paging channel and is applicable to the case where the UE is camped in "limited service" or "no service".

[0072] For example, one or more computer systems such as Figure 7The computer system 700 shown is used to implement various aspects. The computer system 700 can be any computer capable of performing the functions described herein, such as Figure 1 and FIG. 2A to FIG. 2B UE 101, base station 111, base station 113, base station 115, base station 117 and base station 119 are shown. Computer system 700 includes one or more processors (also called central processing units or CPUs), such as processor 704. Processor 704 is connected to communication infrastructure 706 (e.g., a bus). Computer system 700 also includes user input / output devices 703, such as monitors, keyboards, pointing devices, etc., that communicate with communication infrastructure 706 through user input / output interface 702. Computer system 700 also includes main memory or primary storage 708, such as random access memory (RAM). Main memory 708 may include one or more levels of cache. Main memory 708 has control logic components (e.g., computer software) and / or data stored therein.

[0073] The computer system 700 may also include one or more secondary storage devices or memories 710. The secondary storage 710 may include, for example, a hard disk drive 712 and / or a removable storage device or drive 714. The removable storage drive 714 may be a floppy disk drive, a tape drive, an optical drive, an optical storage device, a tape backup device, and / or any other storage device / drive.

[0074] The removable storage drive 714 may interact with a removable storage unit 718. The removable storage unit 718 includes a computer usable or readable storage device having computer software (control logic) and / or data stored thereon. The removable storage unit 718 may be a floppy disk, a magnetic tape, a compact disk, a DVD, an optical storage disk, and / or any other computer data storage device. The removable storage drive 714 reads from and / or writes to the removable storage unit 718 in a well-known manner.

[0075] According to some aspects, the secondary memory 710 may include other devices, tools, or other methods for allowing the computer system 700 to access computer programs and / or other instructions and / or data. Such devices, tools, or other methods may include, for example, a removable storage unit 722 and an interface 720. Examples of removable storage units 722 and interfaces 720 may include a program cartridge and cartridge interface (such as found in video game devices), a removable memory chip (such as an EPROM or PROM) and an associated socket, a memory stick and USB port, a memory card and an associated memory card slot, and / or any other removable storage unit and associated interface.

[0076] In some examples, the main memory 708, the removable storage unit 718, and the removable storage unit 722 may store instructions that, when executed by the processor 704, cause the processor 704 to perform operations for a UE or a base station (e.g., Figure 1 and FIG. 2A to FIG. 2B 101, base station 111, base station 113, base station 115, base station 117, and base station 119). In some examples, the operations include Figures 3 to 6 Those operations illustrated and described in .

[0077] The computer system 700 may also include a communication or network interface 724. The communication interface 724 enables the computer system 700 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referenced by reference numeral 728). For example, the communication interface 724 may allow the computer system 700 to communicate with the remote device 728 via a communication path 726, which may be wired and / or wireless and may include any combination of a LAN, a WAN, the Internet, etc. Control logic components and / or data may be transmitted to and from the computer system 700 via the communication path 726. The operation of the communication interface 724 may be performed by a wireless controller and / or a cellular controller. The cellular controller may be a separate controller to manage communications according to different wireless communication technologies. The operations in the foregoing aspects may be implemented in various configurations and architectures. Thus, some or all of the operations in the foregoing aspects may be performed in hardware, software, or in both hardware and software. In some aspects, a tangible, non-transitory apparatus or article of manufacture includes a tangible, non-transitory computer usable or readable medium having stored thereon control logic components (software), also referred to herein as computer program products or program storage devices. This includes, but is not limited to, computer system 700, main memory 708, auxiliary memory 710, and removable storage units 718 and 722, and tangible articles of manufacture embodying any combination of the foregoing. Such control logic components, when executed by one or more data processing devices (such as computer system 700), cause such data processing devices to operate as described herein.

[0078] Based on the teachings contained in this disclosure, it will be apparent to those skilled in the relevant art how to use the Figure 7 The various aspects of the present disclosure may be made and used with data processing devices, computer systems, and / or computer architectures other than those shown. In particular, the various aspects may operate with software, hardware, and / or operating system implementations other than those described herein.

[0079] It should be understood that the Detailed Description section, rather than the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary aspects of the present disclosure as contemplated by the inventors, and thus are not intended to limit the present disclosure or the appended claims in any way.

[0080] Although the present disclosure has been described herein with reference to exemplary aspects of exemplary fields and applications, it should be understood that the present disclosure is not limited thereto. Other aspects and modifications are possible and are within the scope and essence of the present disclosure. For example, and without limiting the generality of this paragraph, the various aspects are not limited to the software, hardware, firmware and / or entities shown in the figures and / or described herein. In addition, the various aspects (whether or not explicitly described herein) have significant practicality for fields and applications outside the examples described herein.

[0081] Various aspects have been described herein with the aid of functional building blocks that illustrate the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries may be defined as long as the specified functions and relationships (or their equivalents) are properly performed. In addition, alternative aspects may perform functional blocks, steps, operations, methods, etc., in an order different from that described herein.

[0082] References herein to "one embodiment," "an embodiment," "an exemplary embodiment," or similar phrases indicate that the described embodiment may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is within the knowledge of those skilled in the relevant art to incorporate such feature, structure, or characteristic into other aspects, whether or not explicitly mentioned or described herein.

[0083] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary aspects, but should be defined only in accordance with the following claims and their equivalents.

[0084] The present disclosure envisions that entities responsible for collecting, analyzing, disclosing, transmitting, storing or otherwise using such personal information data will comply with established privacy policies and / or privacy practices. Specifically, such entities should implement and adhere to privacy policies and practices that are recognized as meeting or exceeding industry or government requirements for maintaining the privacy and security of personal information data. Such policies should be easily accessible to users and should be updated as the collection and / or use of data changes. Personal information from users should be collected for the legitimate and reasonable purposes of the entity and not shared or sold outside of these legitimate uses. In addition, such collection / sharing should only be done after receiving the user's informed consent. In addition, such entities should consider taking any necessary steps to defend and safeguard access to such personal information data and ensure that others who have access to personal information data comply with their privacy policies and processes. In addition, such entities may subject themselves to third-party assessments to demonstrate their compliance with widely accepted privacy policies and practices. In addition, policies and practices should be adjusted to specific types of personal information data collected and / or accessed, and to applicable laws and standards that include specific considerations of jurisdiction. For example, in the United States, the collection or access of certain health data may be governed by federal and / or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA), while health data in other countries may be subject to other regulations and policies and should be handled accordingly. Therefore, different privacy practices should be maintained in each country for different types of personal data.

Claims

1. A multi-mode user equipment UE, the multi-mode user equipment comprising: one or more transceivers configured to enable the UE to communicate wirelessly in a first radio access technology (RAT) and a second RAT; and a processor communicatively coupled to the one or more transceivers, and the processor is configured to: Determining, by a non-access stratum (NAS) layer of a protocol stack operating on the UE, that the UE is registered for communication in the first RAT, and that the UE is in an idle mode with respect to communication in the first RAT; determining, by the NAS layer, that a timer has expired, wherein the timer is configured to calculate an amount of time the UE has been in a disabled mode with respect to communications in the second RAT; sending, in response to the determination that the UE is in the idle mode with respect to communication in the first RAT and the timer has expired, a request to a radio resource control (RRC) layer of the protocol stack by the NAS layer to perform cell selection for the second RAT; receiving, by the NAS layer and from the RRC layer, an indication that the cell selection has been successfully performed for communication in the second RAT; performing, by the NAS layer and in response to receiving the indication that the cell selection has been successfully performed, a registration procedure with a wireless communication system to communicate in the second RAT; as well as After performing the registration process, wireless service is received from the wireless communication system through a base station associated with the second RAT.

2. The UE according to claim 1, wherein the processor is further configured to: listening, through the RRC layer, to system information from the base station associated with the second RAT; selecting, by the RRC layer, the base station for wireless communication in the second RAT; and The indication that the cell selection has been successfully performed for communication in the second RAT is sent to the NAS layer by the RRC layer.

3. The UE of claim 1, wherein to select the base station for wireless communication in the second RAT, the processor is configured to select the base station by using a previously stored frequency list or by performing a band search of a plurality of frequency bands.

4. The UE of claim 1 , wherein the UE communicates with a public land mobile network (PLMN) in the first RAT, and the processor is configured to perform the registration procedure with the wireless communication system to communicate with the same PLMN in the second RAT.

5. The UE of claim 1, wherein the UE communicates with a first public land mobile network (PLMN) in the first RAT, and the UE has been in the disabled mode to communicate with a second PLMN different from the first PLMN in the second RAT.

6. The UE of claim 1 , wherein the UE communicates with a first public land mobile network (PLMN) in the first RAT, and the processor is configured to perform the registration procedure with the wireless communication system to communicate with a second PLMN different from the first PLMN in the second RAT. 7 . The UE of claim 6 , wherein the first PLMN has a first priority, and the second PLMN has a second priority equal to or higher than the first priority.

8. The UE according to claim 1, wherein the processor is further configured to: In response to a determination that the UE is in a mode other than the idle mode, wireless communication in the first RAT is performed.

9. The UE according to claim 1, wherein the processor is further configured to: In response to the NAS layer not receiving the indication from the RRC layer that the cell selection has been successfully performed to communicate in the second RAT, continuing to register to communicate in the first RAT.

10. The UE according to claim 1, wherein the first RAT comprises a Universal Mobile Telecommunications System UMTS Terrestrial Radio Access Network UTRAN, or a Global System for Mobile Communications GSM Edge Radio Access Network GERAN, and the second RAT comprises a New Radio NR Next Generation Radio Access Network NG-RAN.

11. The UE of claim 10, wherein the processor is configured to perform the registration procedure with the wireless communication system to communicate in the second RAT without having an available Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN) for the UE, or with disabled E-UTRAN.

12. A method for user equipment UE, the method comprising: determining to register the UE for communication in a first radio access technology, RAT, and the UE is in an idle mode with respect to communication in the first RAT; determining that a timer has expired, wherein the timer is configured to calculate an amount of time the UE has been in a disabled mode with respect to communications in a second RAT, wherein the second RAT is different from the first RAT; responsive to the determination that the UE is in the idle mode in the first RAT and the timer has expired, performing cell selection for the second RAT; in response to successfully performing the cell selection for the second RAT, performing a registration procedure with a wireless communication system associated with the second RAT; as well as After performing the registration process, wireless service is received from the wireless communication system through a base station associated with the second RAT.

13. The method of claim 12, wherein performing the cell selection comprises: System information is listened to from the base station associated with the second RAT, and the base station is selected for wireless communication in the second RAT.

14. The method of claim 12, wherein the UE communicates with a public land mobile network (PLMN) in the first RAT, and performing the registration procedure comprises: The registration procedure is performed with the wireless communication system to communicate with the same PLMN in the second RAT.

15. The method of claim 12, wherein the UE is communicating with a first Public Land Mobile Network (PLMN) in the first RAT, and the UE has been in the disabled mode to communicate with a second PLMN different from the first PLMN in the second RAT.

16. The method of claim 12, wherein the UE communicates with a first public land mobile network (PLMN) in the first RAT, and performing the registration procedure with the wireless communication system comprises: The registration procedure is performed with the wireless communication system to communicate with a second PLMN different from the first PLMN in the second RAT.

17. The method of claim 12, wherein the first RAT comprises a Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN) or a Global System for Mobile Communications (GSM) Edge Radio Access Network (GERAN), and the second RAT comprises a New Radio (NR) Next Generation Radio Access Network (NG-RAN).

18. The method of claim 17, wherein performing the registration procedure with the wireless communication system to communicate in the second RAT comprises: The registration procedure is performed without having Long Term Evolution (LTE) Evolved-UTRAN, ie, E-UTRAN, available for the UE, or with E-UTRAN disabled.

19. A non-transitory computer-readable medium storing instructions, wherein when the instructions are executed by a processor of a user equipment (UE), the UE performs operations, the operations comprising: determining that the UE is registered for communication in a first radio access technology, RAT, and that the UE is in an idle mode with respect to communication in the first RAT; determining that a timer has expired, wherein the timer is configured to calculate an amount of time the UE has been in a disabled mode with respect to communications in a second RAT, wherein the second RAT is different from the first RAT; responsive to the determination that the UE is in the idle mode in the first RAT and the timer has expired, performing cell selection for the second RAT; performing a registration procedure with a wireless communication system to communicate in the second RAT in response to the cell selection for the second RAT; as well as After performing the registration process, wireless service is received from the wireless communication system through a base station associated with the second RAT.

20. The non-transitory computer readable medium of claim 19, the operations further comprising: performing wireless communication in the first RAT in response to a determination that the UE is in a mode other than the idle mode; as well as In response to the cell selection for the second RAT being unsuccessful, continuing to register to communicate in the first RAT.

Images