User equipment (UE) access and roaming via a non-terrestrial network

Abstract

This disclosure provides systems, methods and apparatuses for managing user equipment (UE) access and roaming via non-terrestrial network (NTN). After a UE (102) registers to a first PLMN (105) via an NTN cell (124), the UE can perform a PLMN search (170) based on frequency information (150, 136) for a second PLMN (107) and one or more PLMN search rules (160). In some aspects, the UE obtains the frequency information (150) via a system information message from the first PLMN or from PLMN access information (130). The one or more PLMN search rules (160) can be based on traditional prioritization of PLMN types. In some aspects, the PLMN search rules are associated with event-triggered PLMN searches.

Description

USER EQUIPMENT (UE) ACCESS AND ROAMING VIA A NON-TERRESTRIALNETWORKCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This International Application claims the benefit of priority of United States Provisional Patent Application No. 63 / 626,794 filed on January 30, 2024, the contents of which are incorporated by reference in their entirety herein.TECHNICAL FIELD

[0002] This disclosure relates generally to wireless communication, and some aspects relate to managing user equipment (UE) access and roaming via a non-terrestrial network (NTN).BACKGROUND

[0003] This background description is provided for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0004] A wireless communication system includes one or more network entities (such as a base station) enabling communication for a mobile communication device (referred to as a user equipment (UE)). Each base station operates one or more cells to provide coverage for the UE. Network selection refers to a procedure by which a user equipment (UE) selects a public-land mobile network (PLMN) and a serving cell for service. A UE with a home PLMN (HPLMN) of a particular wireless carrier may be permitted to roam on other PLMNs (such as one or more visited PLMNs (VPLMNs)) of different wireless carriers. Network selection (which also may be referred to as a PLMN selection) refers to a procedure by which a UE selects a PLMN for registration. The UE performs a PLMN search at various times, such as when the UE first turns on, recovers from an out-of-coverage condition, after a manual user input requesting network selection, as a result of mobility of the UE, or periodically during normal operation. The UE typically performs a PLMN search based on a PLMN prioritization before selecting a serving cell for service. A PLMN selector list includes PLMN identifiers(IDs) and can indicate the priority order of one or more PLMNs above other PLMNs. The UE observes broadcast information from nearby cells to determine the PLMNs operating in an area. Using the PLMN selector list, the UE selects one PLMN (such as the HPLMN) having a higher priority than other PLMNs (such as the VPLMNs). When a UE is currently roaming in a VPLMN or other lower priority PLMN, the UE periodically repeats the PLMN search in an attempt to select a higher priority PLMN.

[0005] Existing wireless communication systems and network selection techniques are based primarily on legacy terrestrial networks. However, the 3rd Generation Partnership Project (3GPP) organization has proposed to extend 5G communications to non-terrestrial networks (NTNs) with 5G new radio (NR) technologies, or with the Long-Term-Evolution (LTE) technologies tailored for the Narrowband Internet-of-Thing (NB-IoT) or the enhanced Machine Type Communication (eMTC) technologies. A non-terrestrial network (NTN) refers to a network, or segment of networks, using radio frequency (RF) resources on board an NTN node. Example NTN nodes include spaceborne vehicles or airborne vehicles. Airborne platforms can include unmanned aircraft systems (UAS), High-Altitude Platform Systems (HAPS), balloons, dirigibles, winged platforms such as airplane or drones, among other examples. Spaceborne platforms can include a Geostationary Earth Orbit (GEO) satellite (sometimes also referred to as a geosynchronous orbit (GSO) satellite), a Low Earth Orbit (LEO) satellite, a Medium Earth Orbit (MEO) satellite, or a Highly Elliptical Orbit (HEO) satellite, among other examples. In some implementations, NTN nodes can form constellations. For simplicity, the discussion below refers to all such apparatuses as satellites. In addition to satellites, an NTN can include the sat-gateways that connect satellites to a public data network, feeder links between sat-gateways and satellites, service links between satellites, and inter-satellite links (ISL) when satellites form constellations.

[0006] A PLMN can be associated with different types of access technology operating in different frequencies. Furthermore, some PLMNs (or portions of a PLMN) can operate on TN cells while other PLMNs (or portions of a PLMN) can operate on NTN cells. Current techniques for network selection are inadequate to manage network selection in view of different access technology types, particularly with regard to NTN access.BRIEF SUMMARY

[0007] The systems, methods, and apparatuses of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0008] One innovative aspect of the subject matter described in this disclosure can be implemented as method for wireless communication by a user equipment (UE). The method includes the UE obtaining public land mobile network (PLMN) access information for a first PLMN and a second PLMN, where the second PLMN has a higher priority than the first. The method includes the UE registering to the first PLMN via a non-terrestrial network (NTN) cell. The method includes the UE receiving system information from the NTN cell of the first PLMN that indicates frequency information for the second PLMN. The method includes the UE performing a PLMN search for the second PLMN based on the frequency and access information.

[0009] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method for wireless communication by a UE. The method includes the UE registering to a first PLMN via an NTN cell, obtaining frequency information regarding a second PLMN that has a higher priority than the first PLMN, and performing a PLMN search based on the frequency information and one or more PLMN search rules.

[0010] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method for wireless communication by a network entity of an NTN in a first PLMN. The method includes the network entity communicating with a UE via an NTN cell. The method includes the network entity transmitting, via the NTN cell, system information that indicates frequency information for a terrestrial network (TN) of a second PLMN.

[0011] Another innovative aspect of the subject matter described in this disclosure can be implemented as an apparatus that includes a communication unit and a processing system configured to control the communication unit to implement any one of the above-referenced methods.

[0012] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Otherfeatures, aspects, and advantages will become apparent from the description, the drawings, and the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Like reference numbers and designations in the various drawings indicate like elements. Note that the relative dimensions of the figures may not be drawn to scale. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0014] FIG. 1 shows an example wireless communication system in which a user equipment (UE) performs a public land mobile network (PLMN) search.

[0015] FIG. 2 shows the example wireless communication system of FIG. 1 in a scenario where the UE might benefit from PLMN access information.

[0016] FIG. 3 shows an example configuration for network selection.

[0017] FIG. 4A shows example PLMN access information.

[0018] FIG. 4B shows an example PLMN search rule, where a PLMN search order is based on access technology.

[0019] FIG. 5 shows an example table based on the example PLMN access information of FIG. 4A populated with example information.

[0020] FIG. 6A shows a communication flow diagram in which a UE performs a PLMN search.

[0021] FIG. 6B shows a communication flow diagram in which a PLMN search is based on PLMN access information and / or PLMN search rules.

[0022] FIG. 6C shows a communication flow diagram in which a PLMN search is based on system information in association with PLMN access information and / or PLMN search rules.

[0023] FIG. 6D shows another communication flow diagram in which a PLMN search is based on system information in association with PLMN access information and / or PLMN search rules.

[0024] FIG. 7A shows a flow chart with example operations of a UE using a PLMN access information.

[0025] FIG. 7B shows a flow chart with example operations of a UE that manages PLMN selection based on a PLMN access information.

[0026] FIG. 7C shows a flow chart with example operations of a UE using system information to distinguish TN and NTN cells.

[0027] FIG. 8 shows a flow chart with example operations of a network entity in an NTN.

[0028] FIG. 9A shows a flow chart with example operations of a UE for performing PLMN searches based on inter-frequency carrier frequency information and a PLMN access information.

[0029] FIG. 9B shows a flow chart with example operations of a UE for performing PLMN searches based on inter-RAT carrier frequency information and a PLMN access information.

[0030] FIG. 9C shows a flow chart with example operations of a UE for performing PLMN searches based on inter-frequency carrier frequency information and a PLMN ID.

[0031] FIG. 9D shows a flow chart with example operations of a UE for performing PLMN searches based on inter-RAT carrier frequency information and a PLMN ID.

[0032] FIG. 10A shows a flow chart with example operations of a UE for performing cell measurements based on PLMN frequency information.

[0033] FIG. 10B shows a flow chart with example operations of a UE for performing cell measurements based on inter-frequency carrier frequency information and a PLMN access information.

[0034] FIG. 10C shows a flow chart with example operations of a UE for performing cell measurements based on inter-RAT carrier frequency information and a PLMN access information.

[0035] FIG. 10D shows a flow chart with example operations of a UE for performing cell measurements based on inter-frequency carrier frequency information and a PLMN ID.

[0036] FIG. 10E shows a flow chart with example operations of a UE for performing cell measurements based on inter-RAT carrier frequency information and a PLMN ID.

[0037] FIG. 11A shows a flow chart with example operations of a UE that receives system information configuring inter-frequency carrier frequency information.

[0038] FIG. 11B shows a flow chart with example operations of a UE that receives system information configuring inter-RAT carrier frequency information.

[0039] FIG. 12 shows another flow chart with example operations of a UE that manages PLMN selection based on a PLMN access information.

[0040] FIG. 13A shows a timing diagram for periodic PLMN searches.

[0041] FIG. 13B shows a timing diagram for event-triggered PLMN searches.

[0042] FIG. 13C shows a timing diagram for a combination of event-triggered and periodic PLMN searches.

[0043] FIG. 13D shows a timing diagram for event-triggered periodic PLMN searches.

[0044] FIG. 14A shows a flow chart with example operations of a UE to enable or disable event- triggered PLMN searches.

[0045] FIG. 14B shows a flow chart with example operations of a UE to enable event- triggered PLMN searches in addition to periodic PLMN searches when the UE is roaming in a satellite PLMN.

[0046] FIG. 15A shows an example wireless communication system implementing an NTN base station (BS) connecting to a satellite via an NTN gateway using a transparent payload implementation.

[0047] FIG. 15B shows an example wireless communication system implementing an NTN BS with feeder links to multiple satellites.

[0048] FIG. 15C shows an example wireless communication system implementing an NTN BS onboard on a satellite using a regenerative payload implementation.

[0049] FIG. 16A shows an example user plane protocol stack in accordance with aspects of this disclosure.

[0050] FIG. 16B shows an example control plane protocol stack in accordance with aspects of this disclosure.

[0051] FIG. 17 shows a block diagram of an example wireless communication system showing hardware features and communication interfaces.DETAILED DESCRIPTION

[0052] The following description is directed to certain implementations for the purpose of describing innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. Some of the examples in this disclosure are based on wireless communication according to the 3rd Generation Partnership Project (3GPP) wireless standards, such as the 4th generation (4G) Long Term Evolution (LTE) and 5th generation (5G) New Radio (NR) standards. However, the described implementations can be implemented in any device, system, or network that is capable of transmitting and receiving radio frequency signals according to any of the wireless communication standards, including any of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 or 802.16 wireless standards, or other known signals that are used to communicate within a wireless, cellular, or internet of things (loT) network, such as a system utilizing 4G, 5G, 6G, WiFi, or future radio technology.

[0053] An operator may operate one or more public land mobile networks (PLMNs). Users having a subscription to a particular operator will have user equipment (UE) configured to register to a home PLMN (HPLMN) or equivalent HPLMN (EHPLMN) of the operator when the UE is in a coverage area of the HPLMN / EHPLMN. Meanwhile, when the UE is out of a coverage area of the HPLMN / EHPLMN, the UE might register to another operator's PLMN under a roaming agreement between the operators. When roaming to another PLMN (referred to as a Visited PLMN, or VPLMN), the UE is configured to periodically search for a higher priority PLMN (such as the HPLMN).

[0054] Operators are increasingly deploying satellite access (via a non-terrestrial network (NTN)) or implementing roaming agreements with other operators for satellite access. Because some NTNs are not confined to geopolitical boundaries, it is common for an NTN to have a PLMN identifier (ID) that differs from the PLMN IDs for terrestrial network (TN)s. In some instances, multiple PLMNs (from same or different operators) can operate within a frequency band using different types of access technology. A satellite operator (with an NTN- specific PLMN) might support roaming agreements from multiple TN operators. The 3 GPP technical specification (TS) 31.102 (version 18.3.0, sections 4.2.5 and 4.2.53) and TS 29.571 (version 18.4.0, section 5.4.3.2) include lists of radio access technology types. In addition to 5GNR and Evolved Universal Terrestrial Radio Access (EUTRA) RAT types associated withTNs, example RAT types include narrowband loT (NB-IoT) and various types of satellite access using 5G NR, EUTRA, and NB-IoT. Traditional techniques for managing network selection are agnostic to whether a particular PLMN is a TN or NTN or whether the PLMN operates a particular RAT type. Typically, a UE might scan all frequencies to identify candidate cells and then obtain PLMN information from the candidate cells. In some implementations, a TN cell broadcasts information about available carrier frequencies (typically for cells in the same PLMN or same operator) to assist the UE with cell selection. However, in the scenario where an NTN cell supports roaming by UEs of different operators, the traditional network selection techniques are inadequate to manage PLMN searching by a UE registered to a VPLMN via an NTN.

[0055] This disclosure provides systems, methods and apparatuses for improving UE PLMN searching when the UE is registered to a first PLMN (e g., roaming to a VPLMN) via an NTN. After the UE registers to a first PLMN via an NTN cell (also referred to as a satellite cell), the UE can perform a PLMN search for a second PLMN based on frequency information for the second PLMN and one or more PLMN search rules. An NTN cell can refer to any apparatus of an NTN that operates a cell, and the term “NTN cell” can be replaced with “NTN node,” “NTN base station,” “satellite,” or NTN (for brevity). This disclosure includes several techniques by which the UE can obtain frequency information regarding the second PLMN, such as via a system information message from the first PLMN, from PLMN access information stored in a memory element (ME) of the UE, or a combination of system information and the PLMN access information.

[0056] In some aspects, the UE performs a PLMN search based on one or more PLMN search rules. In some implementations, the PLMN rules are based on a prioritization of PLMN types. Alternatively, or additionally, the PLMN search rules are based on the PLMN access information, one or more predefined or configured rules, or PLMN search triggering criteria. In some aspects, the UE performs periodic and / or event-triggered PLMN searches. In some implementations, the UE or the network enables or disables the event-triggered PLMN search criteria based on whether the UE is registered to the first PLMN via NTN or TN access, respectively.

[0057] In some aspects, the UE obtains the frequency information regarding the second PLMN from PLMN access information. PLMN access information can also referred to as a“PLMN access configuration.” The PLMN access information includes PLMN IDs associated with PLMNs that the UE can access. In some implementations, the PLMN access information includes PLMN frequency information (such as a frequency range and / or a frequency band number) associated with each PLMN ID. The UE can use the PLMN frequency information to quickly scan for available cells of the second PLMN. In some implementations, the PLMN access information also includes a search order, PLMN search rules, triggering criteria, or other parameters that impact when and how the UE performs a PLMN search that includes the second PLMN. The search order, PLMN search rules, triggering criteria, or other parameters can depend on whether the UE is registered to a PLMN via an NTN and the registered PLMN has a lower priority than the second PLMN (such as a HPLMN).

[0058] In some aspects, the UE obtains the frequency information for the second PLMN by receiving a system information message from the NTN node of the first PLMN. As an example, an NTN of the first PLMN can transmit a system information block (SIB) message that includes the frequency information for the second PLMN. Typically, a radio access network (RAN) node of one TN PLMN does not transmit system information (SI) regarding frequencies of a different TN PLMN. In a traditional deployment, a RAN node of a TN PLMN might provide inter-frequency carrier frequency information or inter-RAT carrier frequency information about other RANs associated with the TN PLMN or the same operator to enable the UE to perform cell reselection. The 3GPP defines some SIB types (such as SIB type 4 (SIB4) or SIB type 5 (SIB5)) for inter-frequency and inter-RAT carrier frequency information for cell reselection. Because an operator of an NTN PLMN might be partnered with several TN operators, and spectral resources are limited, there is a desire to reduce roaming on the NTN PLMN. Thus, in accordance with aspects of this disclosure, an NTN might proactively transmit SI regarding a different operator's TN PLMN. For example, the NTN node can transmit SIB4, SIB5, or other SIB type messages for PLMN search purposes (rather than only for cell reselection purposes). The SIB can include inter-frequency carrier frequency information or inter-RAT carrier frequency information about cells for other PLMNs in the coverage area of the UE. In some implementations, the SIB also includes a PLMN ID associated with the inter-frequency carrier frequency information or inter-RAT carrier frequency information so that the UE can match the frequency information with a PLMN ID having a higher priority in the PLMN access information.

[0059] Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. A UE can quickly identify potential frequencies for other PLMNs within a coverage area using the PLMN access information or frequency information from an NTN node in a VPLMN. In some aspects, the PLMN access information provides additional flexibility to deploy multiple PLMNs within a frequency band or to deploy different RAT types using different frequency ranges within a frequency band. A potential technical advantage of the PLMN search rules or event-triggered PLMN search criteria is that a UE can perform a PLMN search sooner than might otherwise be scheduled for a periodic PLMN search or without the PLMN search rules. In some instances, a UE that is roaming on an NTN can use the techniques of this disclosure to identify and search for a higher priority PLMN (such as through a TN or a different RAT type), thereby reducing congestion in an NTN cell.

[0060] FIG. 1 shows an example wireless communication system 100 in which a UE 102 performs a PLMN search. An NTN extends or augments the service capability of a wireless communication system. An NTN refers to a network, or segment of networks, using radio frequency (RF) resources on board an NTN node (such as a spaceborne vehicle or an airborne vehicle). An NTN node can belong to one of several types based on altitude, orbit, and beam footprint size. For brevity in this disclosure, all types of NTN nodes are referred to as a satellite 104. A satellite 104 can support a transparent or a regenerative (with on board processing) payload, and typically generates several beams for a given service area bounded by the field of view. For a transparent payload implementation, a satellite 104 can apply RF filtering and frequency conversion and amplification, and not change the waveform signal. For a regenerative payload implementation, a satellite 104 can apply RF filtering, frequency conversion and amplification, demodulation and decoding, routing, and coding / modulation. An NTN gateway 117 (sometimes also referred to as a "sat-gateway") connects the satellite 104 to a BS 116A or other data network resources. In some deployments, some operations of the BS 116A can be collocated with the satellite 104 (shown as BS 116B). In this disclosure, the term BS 116 can refer to either or both the BS 116A on the ground (when present) or the BS 116B (when onboard the satellite 104). The NTN gateway 117 provides a ground station that communicatively couples the satellite 104 to the BS 1 16A (when present) or the core network (CN 110) when BS 116A is not present. The BS 106 and the BS 116 are part of oneor more radio access networks (RANs). In the example of FIG. 1 , the satellite 104, the NTN gateway 117, and the BS 116 form part of a first RAN (referred to as NTN 101). The radio access technology for the NTN 101 can be E-UTRA, 5G NR, NB-IoT, among other examples.

[0061] Any number of RANs (such as NTN 101) can be communicatively coupled to a CN 110. The CN 110 can be implemented as an evolved packet core (EPC), a fifth generation (5G) core (5GC), or a sixth generation (6G) core. A PLMN refers to a combination of a core network and a RAN. For example, PLMN 105 includes the CN 110 and the NTN 101. Each PLMN has a different PLMN ID. A PLMN ID includes a mobile country code (MCC) and a mobile network code (MNC).

[0062] In FIG. 1 , the UE 102 is registered to the PLMN 105. The UE 102 establishes a radio connection to the satellite 104 via the NTN cell 124, referred to as a radio resource control (RRC) CONNECTED state. After the UE is RRC CONNECTED, the UE 102 might send a network registration request via the NTN 101 (i.e., the satellite 104 and the BS 116 (such as BS 116A or BS 116B)) to the CN 110. The CN 110 determines whether to accept or reject the network registration based on user subscription information. Depending on where the UE 102 is located or what RAN is being accessed, the CN 110 might determine to accept or reject the network registration request. After registering to the PLMN 105, the UE 102 can release or suspend the radio connection. An RRC IDLE state refers to a state where the radio connection is released. An RRC INACTIVE states refers to a state where the radio connection is suspended.

[0063] FIG. 1 also shows another PLMN 107. The PLMN 105 can be referred to as a first PLMN, and the PLMN 107 can be referred to as a second PLMN. The PLMN 107 includes a RAN 103 and CN 109. RAN 103 includes one or more base stations (such as BS 106). In some implementations, BS 106 is associated with a different RAT (different from the NTN 101). For example, the BS 106 can be a next generation base station (gNB) and can operate the TN cell 126 as a 5G new radio (NR) cell. Alternatively, the BS 106 can be a legacy type of base station (such as ng-eNB or eNB) and operates the TN cell 126 as an evolved universal terrestrial radio access (E-UTRA) cell.

[0064] A UE performs a PLMN selection to select a PLMN for registration. In a conventional network selection mechanism, the UE selects the PLMN and RAN (referred to as network selection or PLMN selection) based on priority after determining which PLMNsare available in an area. After selecting a highest priority PLMN, the UE selects a cell (referred to as cell selection) of the RAN in the selected PLMN. The UE limits cell selection to candidate cells that are in the selected PLMN and RAN. Cell selection or reselection might involve selection of a candidate cell that has the highest signal strength or signal quality that the UE can measure from among the candidate cells in the selected PLMN / RAN. The UE might monitor signal strength and signal quality of multiple frequencies to select the serving cell from among the candidate cells in the selected PLMN. In some implementations, a UE might receive a system information broadcast (SIB) message or other type of message that can be populated with cell selection criteria. The UE might camp on a selected serving cell to register with the PLMN. A UE is said to be camped on a serving cell when the UE has registered with the wireless communication and established a basic RRC relationship with the cell.

[0065] In an example scenario, UE 102 might be a subscriber of a HPLMN that is other than the PLMN 105, such as PLMN 107 or another PLMN (not shown). However, the operator of the HPLMN can have a roaming agreement with the operator of the PLMN 105 to permit the UE 102 to have roaming access to the PLMN 105. When the UE 102 is registered to the PLMN 105, the PLMN 105 can be referred to as a Visited PLMN (VPLMN) or roaming PLMN. It should be apparent that coverage of various networks can change over time due to movement, such as movement of the UE 102 or movement of the NTN 101. For example, the UE 102 might register to PLMN 105 when it is located in a coverage area of the NTN cell 124 and before it moves to a coverage area of the TN cell 126. In some instances, the UE 102 can be in a location that has coverage from both the PLMN 105 and the PLMN 107. When the UE 102 is registered to a VPLMN, the UE 102 is configured to periodically search for a higher priority PLMN (such as a HPLMN). In the example of FIG. 1, the PLMN 107 might have a higher priority PLMN type (such as a HPLMN or EHPLMN) compared to the PLMN 105 (as a VPLMN). FIG. 3 provides a further description of an example search order for PLMNs where a search order is based on PLMN type.

[0066] In accordance with aspects of this disclosure, the UE 102 can perform a periodic or event-triggered PLMN search 170. When the UE 102 is registered to the PLMN 105, the UE 102 can use frequency information about the PLMN 107 to improve the PLMN search 170. In some aspects, the UE 102 obtains the frequency information (referred to as PLMNfrequency information 136) from PLMN access information 130. The PLMN access information 130 can include PLMN ID(s) 132 for one or more PLMNs, such the PLMN ID for the PLMN 107. The PLMN access information 130 can also include the PLMN frequency information 136 for the PLMN 107. In some implementations, the PLMN access information 130 includes one or more PLMN search rules 160 that cause the UE 102 to trigger a PLMN search for the PLMN 107 based on criteria, such as when the UE 102 is registered to an NTN PLMN (such as the PLMN 105).

[0067] In some aspects, the UE 102 receives the frequency information (shown as frequency information 150) from the NTN 101 (such as the satellite 104). For example, the NTN 101 (in PLMN 105) can provide frequency information 150 about TN cells of the RAN 103 (in PLMN 107). In some aspects, the UE 102 can obtain the frequency information based on a combination of the PLMN frequency information 136 in the PLMN access information 130 and the frequency information 150 that it receives from the PLMN 105. For example, the UE 102 can match frequency information 150 in a SIB with the PLMN frequency information 136 to determine that the PLMN 107 is present in the coverage area of the NTN cell 124. Based on a priority or other PLMN search rules 160 in the PLMN access information 130, the UE 102 can perform a PLMN search for the PLMN 107 using the frequency information 150. Alternatively, or additionally, the satellite 104 can transmit the frequency information 150 with associated PLMN IDs such that the UE 102 can determine that the frequency information 150 is related to a PLMN ID 132 for the 107 in the PLMN access information 130. The UE 102 can determine that the PLMN 107 is present in the UE geographic position based on receiving the frequency information 150. When the frequency information 150 (e g., frequency or PLMN ID) matches the PLMN 107 having a higher priority, the UE 102 can trigger a PLMN search for the PLMN 107 using the frequency information 150 or the PLMN frequency information 136.

[0068] This disclosure includes several techniques to modify when and how the UE 102 conducts the PLMN search 170. For example, the PLMN access information 130 can include PLMN search rules 160. Alternatively, or additionally, the UE can obtain the PLMN search rules 160 from a PLMN selector list or 3GPP specification. The PLMN search rules 160 might describe, among other things, a periodicity for the UE 102 to perform the PLMN search 170 using periodic PLMN searches. Alternatively, or additionally, the PLMN search rules160 might cause the UE 102 to perform the PLMN search 170 as an event-triggered PLMN search or as event-triggered periodic PLMN searches. In some aspects, the PLMN search rules 160 can indicate a preferred order for PLMN searching based on RAT type, PLMN type, UE location, or other conditions.

[0069] FIG. 2 shows the example wireless communication system of FIG. 1 in a scenario where the UE 102 might benefit from PLMN access information. In the example of FIG. 2, the UE 102 is registered to the PLMN 105 (which is a VPLMN for the UE 102). For example, at time ti, the UE 102 can be in a coverage area of the NTN cell 124 and not in the coverage area of a higher priority TN cell, such as TN cell 126. Because the UE 102 is registered to a VPLMN, the UE 102 is configured to perform a periodic network search to discover a higher priority PLMN. The 3GPP TS 23.122 (version 18.5.0) provides a description of automatic network selection using a periodic search timer that is based on what type of access technology is being used. For example, the periodicity of the periodic automatic network selection (beginning with a PLMN search) might depend on whether the VPLMN is using a particular RAT type (such as NB-IoT) or a different RAT type (such as 5G NR or E-UTRA).

[0070] In one scenario, if the PLMN 105 (e.g., the NTN cell 124) is associated with an NB- loT access technology, the periodicity of the PLMN search might be in the range from 2 hours to 240 hours. If the periodicity is 2 hours, the UE 102 might discover the TN cell 126 of the PLMN 107 after 1 hour (mean time). If the periodicity is 240 hours, the UE 102 might discover the TN cell 126 of the PLMN 107 after 120 hours (mean time). In other words, the UE 102 might not discover the TN cell 126 until the UE 102 has been within the coverage of the TN cell 126 for a long period of time. A potential technical advantage of this disclosure is that the PLMN search can occur sooner.

[0071] In another scenario, if the PLMN 105 is associated with a different RAT (such as 5G NR), the periodicity of the PLMN search might be in the range from 6 minutes to 8 hours. If the periodicity is the default value (i.e., 60 minutes), the UE 102 might discover the TN cell 126 of the PLMN 107 after 30 minutes (mean time). If the periodicity is 6 minutes, the UE 102 might discover the TN cell 126 of the PLMN 107 after 3 minutes (mean time). However, when the UE 102 is outside the coverage of the TN cell 126, and the UE 102 performs a PLMN search every 6 minutes, this might needlessly increase power consumption and drain battery of the UE 102 faster. A potential technical advantage of this disclosure is that thePLMN search 170 can more efficiently discover the PLMN 107 or reduce the number of PLMN search attempts during these situations.

[0072] Another shortcoming of the current techniques for PLMN search 170 is that, absent the techniques of this disclosure, the UE 102 might consume power searching for large ranges of frequencies. When the UE 102 performs a PLMN search, the UE 102 might not be aware of which frequencies are being used by the PLMN 107 in a particular area. In a traditional TN deployment, a PLMN (e.g., first operator) might provide frequency information for other RANs of that PLMN or the same operator. However, typically, a first operator of a TN PLMN would not provide frequency information for a second TN PLMN. Thus, absent the techniques of this disclosure, when the UE 102 is registered to the PLMN 105, the UE 102 might not be aware of the frequencies associated with RAN 103 which can inhibit or slow the PLMN search 170 process. A potential technical advantage of this disclosure is that the UE 102 can obtain frequency information for the PLMN 107 to improve the PLMN search process.

[0073] The traditional techniques for PLMN search are based on a prioritization of PLMN types (as further described with reference to FIG. 2). The traditional techniques might not distinguish between various NTN and TN access technologies. For example, consider a scenario where the UE 102 has moved to a new location at time t2. At time t2, the UE 102 might be within the coverage area of multiple PLMNs (such as PLMN 107, PLMN 105, and PLMN 208). PLMN 208 might operate a satellite 204 with a different satellite-based access technology than the satellite 104. Depending on the UE 102 (or operator configuration), the UE 102 might be better suited for a particular access technology for any of the PLMNs. In some instances, the UE 102 might prefer to register with a VPLMN via 5G NR access before considering a VPLMN with E-UTRA access. In other instances, the UE 102 might prefer to register with a VPLMN via a TN E-UTRA) access before considering a VPLMN with satellite 5G NR access. The UE 102 might prefer to register to a VPLMN via satellite NB-loT access before considering a VPLMN with satellite 5G NR access. Thus, a potential technical advantage of this disclosure is to enable PLMN search (for network selection) based on a flexible arrangement of PLMN access information and PLMN search rules.

[0074] FIG. 3 shows an example configuration 300 for network selection. The example configuration 300 is based on a traditional network selection procedure that is focused onprioritizing PLMN types. When selecting a PLMN, a UE usually selects a network that has the highest priority PLMN type among available PLMNs. For example, the UE searches for available networks prioritized in the following order (of decreasing priority): HPLMN (or Equivalent HPLMN); user controlled PLMN (UPLMN); operator Controlled PLMN (OPLMN); and other PLMN / access technology combinations. A UE can have various PLMN lists (also referred to as PLMN selector list) to record the various PLMN and access technologies, shown as HPLMN and EHPLMN list 361A, a user controlled PLMN selector list 361B, operator controlled PLMN selector list 361C, and 361D. Each PLMN selector list can be formatted to include some basic information about the PLMNs. FIG. 3 shows an example PLMN selector list 361.

[0075] The PLMN selector list 361 includes an ordered list of PLMNs and access technologies. For example, the PLMN selector list 361 can include entries for a first PLMN, a second PLMN, Nth PLMN, etc., in a prioritized order. Each PLMN is identified by a PLMN ID 322 that is made up from a combination of MCC 323A and MNC 323B. For each PLMN, the PLMN selector list 361 can indicate a PLMN access technology identifier 328. The PLMN access technology identifier 328 is typically a bitmap 329 where various bits can indicate the access technologies supported by the PLMN. For example, each bit can be associated with a different RAT type. Examples of RAT types include: 5G NR, Evolved Universal Terrestrial Radio Access (EUTRA), narrow-band loT (NB-IoT). As satellite networks are deployed, the list of RAT types has expanded to included various types of satellite access types, such as NR (low Earth orbit, LEO) satellite access type, NR (medium Earth orbit, MEO) satellite access type, NR (geosynchronous Earth orbit, GEO) satellite access type, NR (other) satellite access type, wideband (WB) E-UTRAN (LEO) satellite access type, WB-E-UTRAN (MEO) satellite access type, WB-E-UTRAN (GEO) satellite access type, WB-E-UTRAN (other) satellite access type, NB-IoT (LEO) satellite access type, NB-IoT (MEO) satellite access type, NB- loT (GEO) satellite access type, NB-IoT (other) satellite access type, LTE-M (LEO) satellite access type LTE-M (MEO) satellite access type LTE-M (GEO) satellite access type LTE-M (other) satellite access type, among other examples.

[0076] The example configuration 300 illustrates at least two shortcomings. As the number of access technologies increase and new RAT types are being introduced (such as satellitebased access technologies) the PLMN selector list 361 may not indicate the various RATtypes possible due to a limited number of bits available in the bitmap 329. Furthermore, the PLMN selector list 361 might not provide a prioritization of access technologies within the same PLMN if the bitmap 329 is used to indicate all RAT types available for a PLMN ID. In order to distinguish access technologies within the same PLMN, the PLMN selector list 361 would require multiple entries for the same PLMN ID, where each entry has a different bitmap 329. Such an approach might increase the size and complexity of the PLMN selector list 361. Techniques of this disclosure can provide flexibility for a UE manufacturer, network operator, or user to manage access for various PLMN types and access technologies.

[0077] FIG. 4A shows example PLMN access information 430. The PLMN access information 430 can include multiple records or entries (such as entry 431(n)). Each entry 431(n) can indicate a combination of a PLMN ID 322, a RAT type 434, and PLMN frequency information 436. In some implementations, the RAT type 434 can be omitted (such as when that information is available in a PLMN selector list or other configuration). The RAT type 434 can be any one of NR (i.e., terrestrial NR), E-UTRA (i.e., terrestrial E-UTRA), satellite NR, satellite E-UTRA, satellite NB-IoT, or another RAT type. In some implementations, the RAT type 434 can be based on a list of potential RAT types in the 3GPP specification, such as in 3GPP TS 31.102 (version 18.3.0, sections 4.2.5 and 4.2.53) and TS 29.571 (version 18.4.0, section 5.4.3.2). The RAT type 434 can distinguish between NTN and TN based access, such that satellite 5G NR is distinguished from (TN) 5G NR. Furthermore, in some implementations, the RAT type 434 can distinguish different satellite types, such as LEO, MEO, GEO, etc. In some implementations, the RAT type 434 can further distinguish different airborne or spaceborne platforms, such as satellite, UAS, HAPS, among other examples. The RAT type 434 can be based on any combination of access technology, NTN or TN, type.

[0078] The PLMN frequency information 436 can indicate a frequency band 437, a frequency range 438, or both. The frequency band 437 can refer to a predefined frequency band, such as any of the frequency bands defined in 3GPP TS 36.101 (version 18.3.0), TS 36.102 (ver. 18.4.0), TS 38.101-1 (ver. 18.4.0), TS 38.101-2 (ver. 18.4.0), TS 38.101-3 (ver. 18.4.0), TS 38.101-4 (ver. 18.2.0), and / or TS 38.101-5 (ver. 18.4.0). The frequency range 438 can refer to a subset of the frequencies within a frequency band. In some implementations, the frequency range 438 can include frequencies that include portions of adjacent frequency bands. Note that the frequency range 438 indicates a range of frequencieswithin all or part of frequency bands, not to be confused with “Frequency Range (FR1)” or "Frequency Range (FR2)" which are related to large portions of spectrum allocated for wireless communication.

[0079] In some implementations, a search order or prioritization is implicit based on the ordering of the entries 43 l(n). In some implementations, the entry 43 l(n) can include a search order 461 field to explicitly indicate a search order, priority, or other parameters that control a relative order or criterion for searching PLMNs indicated in the PLMN access information 430. In some implementations, a search order can be based on a PLMN selector list (such as described with reference to FIG. 3. Alternatively, or additionally, a search order can be inherent in one or more PLMN search rules.

[0080] FIG. 4B shows an example PLMN search rule 460, where a PLMN search order is based on access technology. For example, the example PLMN search rule 460 might indicate a preference for RAT types in the following order: a first RAT type 462, a second RAT type 464, a third RAT type 466, and then a fourth RAT type 468. The RAT types 462, 464, 466, and 468 can also be specific to NTN or TN access technologies. As an example, for illustrative purposes, the PLMN search rule 460 might cause the UE to search PLMNs using the following order: PLMN(s) with E-UTRA (TN) access, PLMN(s) with 5GNR (TN) access, PLMN(s) with satellite 5G NR access, and then PLMN(s) with satellite E-UTRA access. Other ordering is possible. The example PLMN search rule 460 might be in addition to, or in lieu of, any prioritization based on PLMN type (HPLMN, VPLMNs, etc.)

[0081] FIG. 5 shows an example table based on the example PLMN access information of FIG. 4A populated with example information. In some implementations, the UE can determine whether a PLMN is associated with an NTN or TN based on the frequency band. If the frequency band number is associated with a frequency band for satellite access, the UE can determine the PLMN is associated with an NTN. Otherwise, if the frequency band number indicates the frequency band for a TN, the UE determines the PLMN is associated with a TN. For example, the first row 531 A shows that PLMN ID1 uses frequency band “255”, which is defined for satellite access in a 3GPP specification (e g., 3GPP TS 36. 102 or 38.101-5). The sixth row 53 IF shows the PLMN ID4 is associated with an NTN because the frequency band “256” is defined for satellite access.

[0082] Currently, the 3GPP specifications define frequency bands “255” and “256” for satellite access. However, as more NTNs are deployed and newer types of spaceborne or airborne vehicles are created, it is possible for an NTN to use frequency bands that were previously considered to be for TN access. For example, the second row 53 IB shows a PLMN ID2 using satellite E-UTRA access in frequency band 25. In implementations where a UE relies on the frequency band number to determine whether a PLMN is associated with a NTN or a TN, the use of frequency bands might be limited or the UE might be unable to distinguish NTNs from TNs. For example, consider second row 53 IB, where PLMN ID2 operates a satellite E-UTRA NTN in frequency band “25.” A UE might mistakenly consider PLMN ID2 to be associated with a TN because frequency band “25” is not previously defined for satellite access.

[0083] In some implementations, the PLMN access information 530 explicitly indicates the RAT type. For example, the UE can determine that the PLMN ID1 is associated with an NTN because the first row 531 A indicates the satellite NB-IoT RAT type. In another example, the UE determines that the PLMN ID3 is associated with a TN because none of the entries (third row 531C, fourth row 53 ID, and fifth row 53 IE) for PLMN ID3 indicates a satellite RAT type (e.g., none of the RAT types for the PLMN ID3 has “satellite”). In yet another example, the UE determines a PLMN identified by the PLMN ID4 (sixth row 53 IF) is associated with an NTN because the RAT type is the satellite NR. A potential technical advantage of indicating the RAT type in the PLMN access information 530 is that a UE can easily distinguish whether a PLMN is associated with an NTN or TN based on the indicated access technology type. Another potential technical advantage is that the frequency band number no longer needs to be specific to NTN or TN (thus frequency band “25” can be used for an NTN in the PLMN ID2 of row 53 IB and also used for an NR TN RAN in the PLMN ID3 of row 531E).

[0084] In some implementations, a UE can determine whether a PLMN is an NTN or TN based on a portion of the PLMN ID. Because a PLMN ID includes an MCC, the MCC can be used to determine whether the PLMN includes NTN access. A particular MCC (e.g., “901”) is commonly used to indicate a PLMN that provides services via a satellite. If a PLMN ID includes the particular MCC, the UE can determine that the PLMN identified by that PLMN ID is associated with an NTN. For example, when the PLMN ID2 includes the particularMCC ("901"), the UE can determine that the PLMN ID2 is associated with an NTN. A potential technical advantage is that the RAT type information can be removed from the PLMN access information 530. However, a potential shortcoming is that the particular MCC ("901") can become overused, particularly as more NTNs are deployed. Furthermore, an NTN can remain over the same country (such as a GEO satellite coverage over a large country) where the generic MCC ("901") is less meaningful. More general MCCs could be defined. Alternatively, or additionally, a UE can use the RAT type indicated in the PLMN access information 530 to distinguish NTN or TN so that the PLMN ID can use MCCs other than a general MCC for satellite access.

[0085] In some implementations, when the UE determines to search a PLMN identified by a PLMN ID, the UE determines which RAT and carrier frequencies to search based on the RAT type and the PLMN frequency information (such as the frequency band and / or the frequency range). The frequency range can indicate an uplink (UL) frequency range and a downlink (DL) frequency range. For example, when the UE determines to search PLMN ID1, based on PLMN access information in the first row 531 A, the UE may search one or more carrier frequencies in frequency band 255 and / or the frequency range (i.e., DL: 1525-1559 MHz) using the satellite NB-IoT RAT. In another example, based on the second row 53 IB, when the UE determines to search PLMN ID2, the UE searches one or more carrier frequencies in the frequency range (i.e., DL: 1990-1995 MHz) using the satellite E-UTRA RAT. In yet another example, when the UE determines to search PLMN ID3, based on the third row 531C, the UE searches one or more carrier frequencies in the frequency range (i.e., DL: 869-894 MHz) using the E-UTRA RAT. The use of explicit frequency ranges in the PLMN access information 530 can provide a variety of potential technical advantages, such as the ability for operators to segment a frequency band to different RAT types or the ability so mix NTN and TN within a same frequency band. Furthermore, a UE can limit the number of frequencies based on the indicated frequency range, which provides a potential technical advantage of power saving and faster PLMN search times.

[0086] This disclosure now includes several examples in FIG. 6A through FIG. 14B to illustrate some of options of various aspects of the disclosure. For brevity, the following description will focus on the differences in each figure compared to the general technique described with reference to FIG. 6A and its preceding figures. Where possible, to reduceredundancy, the figures include like reference numbers to represent an event or message already described in a previous figure and the description of that event or message is omitted or summarized in the description of the latter figure.

[0087] FIG. 6A shows a communication flow diagram 600A in which a UE 102 performs a PLMN search. At block 630, the UE 102 obtains PLMN access information (such as the PLMN access information 130, 430, and 530 described with reference to FIG. 1, FIG. 4A, and FIG. 5). In some implementations, a UE obtains the PLMN access information from a Universal Subscriber Identity Module (USIM). The USIM may be a card inserted into the UE 102 or embedded in the UE 102. In other implementations, the UE 102 obtains the PLMN access information from a memory element (ME) of the UE, such as a Non-Volatile Memory (NVM) or memory. For example, the PLMN access information can be stored in the memory element during manufacturing or following an over-the-air (OTA) update, such as from an OTA update server or a device management server. In some implementations, the UE 102 receives a DL message including the PLMN access information a network entity of its HPLMN. In some implementations, the UE 102 obtains the PLMN access information from a leaf node in a management object or other structure for storing configuration data.

[0088] At block 640, the UE 102 registers with a first PLMN, such as the PLMN 105, via an NTN node (represented by the satellite 104 icon). In cases where the NTN is E-UTRA or NB-IoT, the UE 102 performs an attach procedure or a tracking area update procedure with the PLMN 105 via the satellite 104 to register to the PLMN 105. In the attach procedure, the UE 102 transmits an Attach Request message to the PLMN 105, receives an Attach Accept message from the PLMN 105 in response to the Attach Request message, and transmits an Attach Complete message to the PLMN 105 in response to the Attach Accept message. In the Tracking Area Update (TAU) procedure, the UE 102 transmits a TAU Request message to the PLMN 105, receives a TAU Accept message from the PLMN 105 in response to the TAU Request message, and transmits a TAU Complete message to the PLMN 105 in response to the TAU Accept message. In cases where the NTN is a NR, the UE 102 performs a NR registration procedure with the PLMN 105 to register to the PLMN 105. In the registration procedure, the UE 102 transmits a Registration Request message to the PLMN 105, receives a Registration Accept message from the PLMN 105 in response to the Registration Requestmessage, and transmits a Registration Complete message to the PLMN 105 in response to the Registration Accept message.

[0089] In the example scenario in FIG. 6A, the PLMN 105 is a VPLMN. Because the UE 102 is registered to a VPLMN, the UE 102 is configured to perform a PLMN search 670A to discover other suitable PLMNs having a higher priority PLMN type. In the example scenario of FIG. 6A, the PLMN 107 is a higher priority PLMN in comparison to the PLMN 105. In preparation for the PLMN search 670A, the UE 102 can determine PLMN search frequencies for a second PLMN having higher priority (block 665). For example, the identification of the second PLMN as having a higher priority can be based on a PLMN type of the PLMN 107 (e.g., HPLMN or EHPLMN), a PLMN selector list (e.g., indicating PLMN order), PLMN access information (e.g., indicating a search order), or a PLMN search rule, among other examples. The PLMN search frequencies can be based on frequency information from the PLMN search information 630 or from system information 650 received from the PLMN 105. In an example implementation, the PLMN 105 (e.g., satellite 104) transmits system information 650 to indicate frequency information for TN cells of the PLMN 107. FIG. 6B through FIG. 6D provides several examples of how the UE 102 can obtain the frequency information for a PLMN search. The UE 102 can perform the PLMN search 670A based on the frequency information for the PLMN 107. The PLMN search 670A can be a periodic PLMN search and / or an event triggered PLMN search. The example PLMN search 670A can be a periodic PLMN search (as described for FIG. 13 A), an event-triggered PLMN search (as described for FIG. 13B), a combination of a periodic PLMN search and an event-triggered PLMN search (as described for FIG. 13C, or an event triggered periodic PLMN search (as described for FIG. 13D).

[0090] At block 680, based on the PLMN search 670A, the UE 102 discovers a suitable cell of the PLMN 107. At block 690, the UE 102 selects the cell and then registers (block 695) to the PLMN 107 via the selected cell. The operations in block 695 can be similar to those described with reference to block 640, such as an attach procedure, a tracking area update procedure or a registration procedure, to register to the PLMN 107. In some implementations, the UE deregisters (not shown) from the PLMN 105 before registering to the PLMN 107. In other implementations, the UE skips deregistering from the PLMN 105 and registers to the PLMN 107 via the cell directly.

[0091] FIG. 6B shows a communication flow diagram 600B in which a PLMN search is based on PLMN access information and / or PLMN search rules. The events at blocks 630,640, 680, 690, and 695 are the same or similar as the corresponding blocks in FIG. 6A. FIG. 6B differs from FIG. 6A in that FIG. 6B makes use of the PLMN access information 630, while the PLMN access information 630 might not be needed in FIG. 6A because FIG. 6A showed the system information 650 as an alternative or additional option.

[0092] Before or after registering to the PLMN 105, the UE 102 might receive system information 641 from the PLMN 105 via the satellite 104. The system information 641 can include information for intra-frequency cell reselection. In some implementations, the UE 102 might perform measurements or determine to perform measurements on one or more satellite cells on the carrier frequency based on the information in the system information641. Based on the measurements, the UE 102 might perform cell reselection to one of the satellite cell(s) of the satellite 104. In some implementations (such as in a satellite E-UTRA cell), the system information 641 includes a SystemInformationBlockType3 (SIB3) and / or a SystemInformationBlockType4 (SIB4). In some implementations (such as in a satellite NB- loT cell), the system information 641 includes a SystemInformationBlockType3-NB (SIB4- NB) and / or a SystemInformationBlockType4-NB (SIB4-NB). In some implementations (such as a satellite NR cell), the system information 641 includes a SIB2 and / or a SIB3. The intra- frequency information typically includes frequencies for the same RAT type and same network entity (such as the satellite 104). Because the system information 641 does not include frequency information about the PLMN 107, the UE 102 obtains the frequency information regarding PLMN 107 from the PLMN access information 630 - such as the frequency band or frequency range. Thus, at block 670B, the PLMN search is based on the PLMN frequency information in the PLMN access information.

[0093] FIG. 6C shows a communication flow diagram 600C in which a PLMN search is based on system information in association with PLMN access information and / or PLMN search rules. The events at blocks 630, 640, 680, 690, and 695 are the same or similar as the corresponding blocks in FIG. 6A. FIG. 6C differs from FIG. 6A in that FIG. 6C shows the PLMN access information 630 is optional and shows the PLMN search 670C is based on system information 650 indicating the frequency information regarding PLMN 107.

[0094] Two types of system information 650 are shown in FIG. 6C. A first type (referred to as system information 652) includes inter-frequency carrier frequency information. A second type (referred to as system information 654) includes inter-RAT carrier frequency information. Inter-frequency carrier frequency information refers to a list of frequencies that are the same RAT type as the satellite 104 but for a different network entity. Inter-RAT carrier frequency information refers to frequencies for a different RAT type than the satellite 104. The 3GPP defines some standard SIB types that can carry inter-frequency carrier frequency information or inter-RAT carrier frequency information for the purposes of cell reselection. In accordance with aspects of this disclosure, those SIB types (or a new SIB type) can carrier inter-frequency carrier frequency information and / or inter-RAT carrier frequency information for a different PLMN (such as PLMN 107) than the PLMN of network entity transmitting the system information 652 or 654.

[0095] As shown in FIG. 6C, the UE 102 receives system information 652 from the PLMN 105 via the satellite 104. The system information 652 can indicate the inter-frequency carrier frequency information 1, . . . , N, where N is an integer and larger than zero. Each of the interfrequency carrier frequency information fields (1, ... , N) can include a frequency, a channel number, a frequency band, or other information regarding frequencies of cells that are different from the carrier frequency of the satellite 104. In various implementations, the system information 652 can indicate frequencies in the same frequency band or in different frequency bands. In some implementations (such as for a satellite E-UTRA cell), the system information 652 includes a SystemInformationBlockType5 (SIB5) and / or a new system information block (SIB). In other implementations (such as for a satellite NB-IoT cell), the system information 652 includes a SystemInformationBlockType5-NB (SIB5-NB) or a new SIB. In yet other implementations (such as for a satellite NR cell), the system information 652 includes SIB4 or a new SIB.

[0096] Additionally, or alternatively, the UE 102 receives system information 654 from the PLMN 105 via the satellite 104. The system information 654 can indicate inter-RAT carrier frequency information 1, ... , K, where K is an integer and larger than zero. K and N may be the same or different. The inter-RAT carrier frequency information 1 , ..., K can include a frequency, a channel number, a frequency band, or other information regarding frequencies of cells that are a different RAT than the RAT of the satellite 104. In some implementations(such as for a satellite E-UTRA cell), the system information 654 can include a SystemInformationBlockType6 (SIB6). In such cases, the SIB6 can indicate NR carrier frequencies. In some implementations (such as for a satellite NB-IoT cell), the system information 654 can include a SystemInformationBlockType6-NB (SIB6-NB) to indicate NR carrier frequencies and / or E-UTRA carrier frequencies. In some implementations (such as for a satellite NR cell), the system information 654 includes a SIB5 to indicate E-UTRA carrier frequencies.

[0097] Because the UE 102 is registered to the PLMN 105 and the PLMN 105 is a VPLMN, the UE 102 performs a PLMN search 670C (which can be a periodic and / or event-triggered PLMN search). In FIG. 6C, the PLMN search 670C is based on PLMN frequency information from the system information 652 and / or the system information 654. For example, the PLMN search 670C can include a search of the frequencies indicated by the inter-frequency carrier frequency information 1, ..., N and / or the inter-RAT carrier frequency information 1, ..., K. In some implementations, the PLMN search 670C can also be based, at least in part, on the PLMN access information 630. For example, the UE 102 can determine which RAT type to use for which carrier frequencies by identifying that one of the carrier frequencies is in a frequency range for an entry of the PLMN access information 630 that also indicates the RAT type. When the UE 102 performs the PLMN search 670C, the UE 102 can preferentially attempt to search a cell of the PLMN 107 on one or more carrier frequencies configured in the PLMN access information 630 that matches the inter-frequency carrier information and / or the inter-RAT carrier information. In some implementations, the UE 102 skips scanning one or more carrier frequencies that are indicated in the inter-frequency carrier information and / or the inter-RAT carrier information if those carrier frequencies are not configured in the PLMN access information 630. In other implementations, the UE 102 skips scanning one or more carrier frequencies configured in the PLMN access information 630 if those carrier frequencies are not indicated in the inter-frequency carrier information and / or the inter-RAT carrier information. In some implementations, the UE 102 skips scanning one or more carrier frequencies if those frequencies are not configured in the PLMN access information nor the inter-frequency carrier information and / or the inter-RAT carrier information.

[0098] In some examples, the UE 102 can perform the 670C without having obtained the PLMN access information 630. The UE 102 can preferentially attempt to search a cell of thePLMN 107 on one or more carrier frequencies configured in the inter-frequency carrier information and / or the inter-RAT carrier information and supported by the UE 102. In some implementations, the UE 102 skips scanning one or more carrier frequencies configured in the inter-frequency carrier information and / or the inter-RAT carrier information and not supported by the UE 102. In other implementations, the UE 102 skips scanning one or more carrier frequencies supported by the UE 102 and not configured in the inter-frequency carrier information and / or the inter-RAT carrier information. In yet other implementations, the UE 102 skips scanning one or more carrier frequencies neither supported by the UE 102 nor configured in the inter-frequency carrier information and / or the inter-RAT carrier information.

[0099] In some implementations, the PLMN 105 (e g., the satellite 104) transmits (e g., broadcast) other system information (not shown) to assist the UE 102 in determining a TN coverage area. The other system information can be in addition to or as part of the system information 650 shown in FIG. 6C. For example, the other system information can include a SIB type 25 (SIB25) or other SIB that indicates a plurality of TN coverage area information elements. Each of the TN coverage area information elements configures a TN coverage area. For example, each of the TN coverage area information elements includes a reference location information and a distance radius to configure a TN coverage area. The system information 652 or the system information 654 can include an indication of which frequencies are located in one or more of the TN coverage areas. In some implementations, the PLMN 105 associates the TN coverage area information elements with the inter-frequency carrier frequency info 1, ..., N, or the inter-RAT carrier frequency information 1, ..., K, and includes the association information in one or more of the SIBs described for the system information 650. As an example, a SIB for the system information 652 can indicate a TN coverage area for an interfrequency carrier frequency information 1 by referring to an index or identifier of the TN coverage area. Thus, the UE 102 can determine TN coverage areas for the inter-frequency carrier frequency 1 based on the association information. In some implementations, each of the TN coverage area information elements does not include a PLMN ID to indicate a PLMN (e g., a non-satellite PLMN or a TN of the PLMN) in the corresponding TN coverage area. In some implementations, the UE 102 determines that the inter-frequency carrier frequency 1 is operated by the PLMN 107 based on the PLMN access information 630. In such cases,when the UE 102 detects that the UE 102 is within one of the TN coverage areas, the UE 102 may perform a PLMN search to search a TN cell of the PLMN 107 on the in inter-frequency carrier frequency 1. In some implementations, if the UE 102 is in one of the TN coverage areas, the UE 102 performs one or more PLMN searches (e.g., as described in FIG. 13A through FIG. 13D) to search a TN cell of the PLMN 107 on the inter-frequency carrier frequency 1. In some implementations, if the UE 102 is not in any of the TN coverage areas, the UE 102 refrains from performing a PLMN search to search a TN cell of the PLMN 107 on the inter-frequency carrier frequency 1. Although described with reference to the interfrequency carrier frequency information, the TN coverage area information elements can be associated with the inter-RAT carrier frequency information to achieve the same locationbased PLMN search 670C improvements as described with reference to the inter-RAT carrier frequency information.

[0100] FIG. 6D shows another communication flow diagram 600D in which a PLMN search is based on system information 650 in association with PLMN access information and / or PLMN search rules. The events at blocks 630, 640, 680, 690, and 695 are the same or similar as the corresponding blocks in FIG. 6 A. FIG. 6D shows an alternative to the features of FIG. 6C. In FIG. 6D, the system information 650 includes inter-frequency carrier frequency information and / or inter-RAT carrier frequency information that explicitly indicates a corresponding PLMN ID. For example, the system information 653 in FIG. 6D can indicate inter-frequency carrier frequency information similar to the system information 652 described for FIG. 6C, except that the system information 653 further indicates a PLMN ID for each of the inter-frequency carrier frequency information 1, ..., N. Similarly, the system information 655 is similar to the system information 654 of FIG. 6C, except that the system information 655 in FIG. 6D includes a PLMN ID for each of the inter-RAT carrier frequency information 1, ... , K. Examples and implementations for events 652, 654, and 670C can apply to events 653, 655, and 670D, respectively.

[0101] In the system information 653, the PLMN 105 (e.g., the satellite 104) additionally includes 1stPLMN ID, ...., N111PLMN ID indicating to which PLMN the inter-frequency carrier frequency 1 , ... , N belong, respectively. In some implementations, some or all of the 1stPLMN ID, ...., NthPLMN ID can be the same or different. In some implementations, the 1stPLMN ID, . .. ., N111PLMN ID include a PLMN ID identifying the PLMN 107, and at leastone inter-frequency carrier frequency in the inter-frequency carrier frequency 1 , ... , N belongs to the PLMN 107. In the PLMN search 670D, the UE 102 attempts to search a cell of the PLMN 107 on the at least one inter-frequency carrier frequency. The UE 102 skips scanning one or more inter-frequency carrier frequencies configured in the system information 653 for PLMNs other than the PLMN 107 (or that are not included in a PLMN access information or PLMN selector list). In some implementations, if the UE 102 does not support an interfrequency carrier frequency in the at least one inter-frequency carrier frequency, the UE 102 skips scanning the unsupported inter-frequency carrier frequency.

[0102] In the system information 655, the PLMN 105 (e.g., satellite 104) additionally includes (N+l)thPLMN ID, . .. ., (N+K)thPLMN ID to which the inter-RAT carrier frequency 1, ... , K belong respectively. In some implementations, some or all of the (N+l)thPLMN ID, ...., (N+K)thPLMN ID can be the same or different. In some implementations, the (N+l)thPLMN ID, . .. ., (N+K)thPLMN ID include a PLMN ID identifying the PLMN 107, and at least one inter-RAT carrier frequency in the inter-RAT carrier frequency 1, ..., K belong to the PLMN 107. In the PLMN search 670D, the UE 102 attempts to search a cell of the PLMN 107 on the at least one inter-RAT carrier frequency. The UE 102 skips scanning one or more inter-RAT carrier frequencies configured in the system information 655 for PLMNs other than the PLMN 107 and / or the PLMN 105. In some implementations, if the UE 102 does not support an inter-RAT carrier frequency in the at least one inter-RAT carrier frequency, the UE 102 skips scanning the unsupported inter-RAT carrier frequency.

[0103] In some implementations, the UE 102 determines to search or searches the PLMN 107 at event 670D because the UE 102 finds the PLMN ID of the PLMN 107 in the 1stPLMN ID, ...., NhPLMN ID. In some implementations, if the UE 102 does not find the PLMN ID of the PLMN 107 for an inter-frequency carrier frequency in the system information 653 (if received), the UE 102 does not scan or stops scanning any inter-frequency carrier frequency to search the PLMN 107. Alternatively, if the UE 102 does not find the PLMN ID of the PLMN 107 for an inter-frequency carrier frequency in the system information 653 (if received), the UE 102 may scan an inter-frequency carrier frequency based on the PLMN access information as described for FIG. 6A or FIG. 6B. In some implementations, if the UE 102 does not find the PLMN ID of the PLMN 107 for an inter-RAT carrier frequency in the system information 655 (if received), the UE 102 does not scan or stops scanning any inter-RAT carrier frequency to search the PLMN 107. Alternatively, if the UE 102 does not find the PLMN ID of the PLMN 107 for an inter-RAT carrier frequency in the system information 655 (if received), the UE 102 may scan an inter-RAT carrier frequency based on the PLMN access information as described for FIG. 6B.

[0104] FIG. 7A shows a flow chart 700A with example operations of a UE (e.g., UE 102) using a PLMN access information. At block 730, the UE obtains a PLMN access information. At block 740, the UE registers to a first PLMN via an NTN cell. At block 770A, the UE performs one or more PLMN searches to search for a second PLMN based on the PLMN access information. At block 780, the UE discovers a cell (e.g., a TN cell) of the second PLMN in one of the PLMN search(es). At block 790, the UE selects the cell of the second PLMN. At block 795, the UE registers to the second PLMN via the selected cell.

[0105] FIG. 7B shows a flow chart 700B with example operations of a UE that manages PLMN selection based on a PLMN access information. In some implementations, the PLMN access information can be used for an initial network selection to aid the UE to discover a PLMN with which to register after powering on. Furthermore, the PLMN access information can include information (such as PLMN search rules or criteria) that inform the UE if it should register with a particular PLMN. At block 730, the UE obtains a PLMN access information. At block 742, the UE registers to a first PLMN via an NTN cell (e.g., a satellite cell) based on the PLMN access information. At block 744, the UE registers to a second PLMN via a TN cell (e.g., a non-satellite cell) based on the PLMN access information.

[0106] FIG. 7C shows a flow chart 700C with example operations of a UE using system information to distinguish TN and NTN cells. The events at blocks 730, 740, 780, 790, and 795 are the same or similar as the corresponding blocks in FIG. 7A. FIG. 7C differs from FIG. 7A in that FIG. 7C includes blocks 750 and 770B. In block 750, the UE obtains frequency information about TN cells (such as for TN cells of a PLMN that is different from the registered PLMN). Examples of the frequency information in block 750 can include blocks 752 and 754. At block 752, the UE obtains inter-frequency carrier frequency information 1, ..., N, as described with reference to FIG. 6C or FIG. 6D. At block 754, the UE obtains inter-RAT carrier frequency information 1, ..., K, as described with reference to FIG. 6C or FIG. 6D. At block 770B, the UE performs one or more PLMN searches to search a PLMN having a higher search order (than the first PLMN) using PLMN frequencyinformation and RAT types that are based on the PLMN access information, the interfrequency carrier frequency information 1, N and / or the inter-RAT carrier frequency information 1, K.

[0107] FIG. 8 shows a flow chart 800 with example operations of a network entity in an NTN. The operations of flow chart 800 can be implemented by a network entity of an NTN (e.g., the satellite 104, a BS 116, BS 116A, BS 116B, or a distributed unit of BS 116). For ease of terminology, the operations of the flow chart 800 are described as being performed by a network entity (NE). At block 840, the NE communicates with one or more UEs via an NTN cell (e.g., one or more satellite cells). In some implementations, at block 841, the NE transmits (e.g., broadcasts) first system information including information related to one or more satellites via the NTN cell. For example, the first system information includes one of a SIB type 19 (SIB19), a SIB type 31 (SIB31), or a SystemInformationBlockType31-NB (SIB31-NB).

[0108] At block 850, the NE transmits frequency information about a TN of a different PLMN (a PLMN that is different from the PLMN that includes the NE). The operations at block 850 can include any combination of various blocks 852, 854, 853, or 855. The frequency information for blocks 852, 854, 853, or 855 are the same as those described with reference to system information 652, 654, 653, and 655 described with reference to FIG. 6C and FIG. 6D, respectively. At block 852, the NE transmits (e.g., broadcasts) {inter-frequency carrier frequency info 1 },..., {inter-frequency carrier frequency N}, where N is a positive integer. At block 854, the NE transmits {inter-RAT carrier frequency info 1 }, ... , {inter-RAT carrier frequency K}, where K is a positive integer. At block 853, the NE transmits (e.g., broadcasts) {inter-frequency carrier frequency info 1, 1stPLMN ID},..., {inter-frequency carrier frequency N, N* PLMN ID}, where N is a positive integer. At block 855, the NE transmits {inter-RAT carrier frequency info 1, 1stPLMN ID},..., {inter-RAT carrier frequency K. KthPLMN ID}, where K is a positive integer.

[0109] In some implementations, at block 856, the NE can transmit (e g., broadcasts) a SIB including a PLMN ID via the NTN cell. In some implementations, the NE belongs to a first PLMN and the PLMN ID identifies the first PLMN. In some implementations, at block 858, the NE transmits (e.g., broadcasts) a master information block via the NTN cell.

[0110] FIG. 9 A shows a flow chart 900 A with example operations of a UE for performing PLMN searches based on inter-frequency carrier frequency information and a PLMN access information. The events at blocks 730, 740, and 770A are the same or similar as described with reference to FIG. 7A. At block 952, the UE receives inter-frequency carrier frequency information 1, ... , N. N is a positive integer. The inter-frequency carrier frequency information can be similar to the system information 652 described with reference to FIG. 6C.

[0111] At block 931 A, the UE determines whether the PLMN access information indicate that a second PLMN supports at least one of the inter-frequency carrier frequency 1, ..., N. In some implementations, the second PLMN is a HPLMN, an EHPLMN or a higher priority PLMN for the UE 102. If the PLMN access information indicate that the second PLMN support at least one of the inter-frequency carrier frequency 1, ... , N (i.e., “Yes” branch of block 931 A), the flow proceeds to block 970A. At block 970A, the UE performs one or more PLMN searches to search the second PLMN on the at least one inter-frequency carrier frequency. Otherwise, if the PLMN access information indicates that the second PLMN does not support the inter-frequency carrier frequency 1, ..., N (i.e., “No” branch of block 931A), the flow proceeds to either (or both) of block 969A or block 770A. At block 969A, the UE refrains from performing PLMN searches to search the second PLMN on the inter-frequency carrier frequency 1, ..., N.

[0112] FIG. 9B shows a flow chart 900B with example operations of a UE for performing PLMN searches based on inter-RAT carrier frequency information and a PLMN access information. FIG. 9B is similar to FIG. 9A, except that FIG. 9B describes inter-RAT carrier frequency information rather than the inter-frequency carrier frequency information described in FIG. 9A. At block 954, the UE receives inter-RAT carrier frequency information 1, . . ., K. K is a positive integer. The inter-RAT carrier frequency information can be similar to the system information 655 described with reference to FIG. 6C.

[0113] At block 93 IB, the UE determines whether the PLMN access information indicates that a second PLMN supports at least one of the inter-RAT carrier frequency 1, ..., K. In some implementations, the second PLMN is a HPLMN, an EHPLMN or a higher priority PLMN for the UE 102. If the PLMN access information indicates that the second PLMN supports at least one of the inter-RAT carrier frequency 1, ..., K (i.e., “Yes” branch of block93 IB), the flow proceeds to block 970B. At block 970B, the UE performs one or more PLMN searches to search the second PLMN on the at least one inter-RAT carrier frequency. Otherwise, if the PLMN access information indicates that the second PLMN does not support the inter-RAT carrier frequency 1, ..., N (i.e., “No” branch of block 93 IB), the flow proceeds to block 969B and / or block 770A. At block 969B, the UE refrains from performing PLMN searches to search the second PLMN on the inter-RAT carrier frequency 1, ... , K.

[0114] FIG. 9C shows a flow chart 900C with example operations of a UE for performing PLMN searches based on inter-frequency carrier frequency information and a PLMN ID. FIG. 9C is similar to FIG. 9A, except that FIG. 9C describes that system information including the inter-frequency carrier frequency information can include associated PLMN IDs. Additionally, the block 730 is optional in some implementations of FIG. 9C. At block 953, the UE receives inter-RAT carrier frequency information with associated PLMN IDs, shown as {inter-frequency carrier frequency information 1, 1stPLMN ID}, ... , {inter-frequency carrier frequency information N, NthPLMN ID}. N is a positive integer. At block 960, the UE determines whether a PLMN ID of a second PLMN is included in the 1stPLMN ID, ... , NthPLMN ID. In some implementations, the second PLMN is a HPLMN, an EHPLMN or a higher priority PLMN for the UE 102. If the PLMN ID is in the 1stPLMN ID, . .. , N* PLMN ID (i.e., “Yes” branch of block 960), the flow proceeds to block 970C. At block 970C, the UE performs one or more PLMN searches to search the second PLMN on the at least one inter-frequency carrier frequency associated with the PLMN ID. Otherwise, if the PLMN ID is not in the 1stPLMN ID, ..., NthPLMN ID (i.e., “No” branch of block 960), the flow proceeds to block 969A and / or block 770A described in FIG. 9A and FIG. 7A, respectively.

[0115] FIG. 9D shows a flow chart 900D with example operations of a UE for performing PLMN searches based on inter-RAT carrier frequency information and a PLMN ID. FIG. 9D is similar to FIG. 9B, except that FIG. 9D describes that system information including the inter-RAT carrier frequency information can include associated PLMN IDs. Additionally, the block 730 is optional in some implementations of FIG. 9D. At block 955, the UE receives inter-RAT carrier frequency information with associated PLMN IDs, shown as {inter-RAT carrier frequency information 1 , 1stPLMN ID}, . . . , {inter-RAT carrier frequency information K, KthPLMN ID}. K is a positive integer. At block 960, the UE determines whether a PLMN ID of a second PLMN is included in the 1stPLMN ID, ... , KthPLMN ID. In someimplementations, the second PLMN is a HPLMN, an EHPLMN or a higher priority PLMN for the UE 102. If the PLMN ID is in the 1stPLMN ID, KthPLMN ID (i.e., “Yes” branch of block 960), the flow proceeds to block 970D. At block 970D, the UE performs one or more PLMN searches to search the second PLMN on the at least one inter-RAT carrier frequency associated with the PLMN ID. Otherwise, if the PLMN ID is not in the 1stPLMN ID, . . . , KthPLMN ID (i.e., “No” branch of block 960), the flow proceeds to block 969B and / or block 770A described in FIG. 9B and FIG. 7A, respectively.

[0116] FIG. 10A shows a flow chart 1000A with example operations of a UE for performing cell measurements based on inter-frequency carrier frequency information and a PLMN access information. Blocks 730, 740, and 750 are the same or similar to the corresponding blocks described in FIG. 7A and FIG. 7C. After receiving the frequency information about the TN cells of a second PLMN at block 750, the flow chart 1000A proceeds to block 1060. At block 1060, the UE determines whether the second PLMN is a higher priority PLMN for the UE, such as based on the PLMN access information or a PLMN selector list. Alternatively, or additionally, at block 1060, the UE can determine whether the frequency information matches a frequency band or frequency range in the PLMN access information. If the answer to either inquiry (or both inquiries) at block 1060 is YES (i.e., the “Yes” branch of block 1060), the flow chart 1000A proceeds to block 1004A. At block 1004A, the UE performs measurements based on the frequency information. In some implementations, if one or more measurement results obtained from the measurements indicate that a cell is suitable, the UE performs cell selection to the cell. Otherwise, if no cell on the at least one interfrequency carrier frequency is suitable, the UE contentiously selects a serving cell provided by the satellite.

[0117] Otherwise, if the answer to either inquiry (or both inquiries) at block 1060 is NO (i.e., the “No” branch of block 1060), the flow chart 1000A proceeds to block 1006A. At block 1006A, the UE refrains from performing measurements on frequencies included in the frequency information from block 750.

[0118] FIG. 10B shows a flow chart 1000B with example operations of a UE for performing cell measurements based on inter-frequency carrier frequency information and a PLMN access information. FIG. 10B is similar to FIG. 10A except that blocks 750, 1060, 1004A and 1006A are replaced by blocks 952, 931 A, 1004B, and 1006B, respectively. At block931 A, the UE determines whether the PLMN access information indicates that a second PLMN supports a frequency matching the inter-frequency carrier frequency information received at block 952. (See FIG. 9A). If so, then the flow chart 1000B proceeds to block 1004B, where the UE performs measurements on at least one inter-frequency carrier frequency. Otherwise, the flow chart 1000B proceeds to block 1006B, where the UE refrains from performing the measurements on the inter-frequency carrier frequencies indicated in the inter-frequency carrier frequency information.

[0119] FIG. 10C shows a flow chart 1000C with example operations of a UE for performing cell measurements based on inter-RAT carrier frequency information and a PLMN access information. FIG. 10C is similar to FIG. 1 OB except that blocks 952, 931 A, 1004B and 1006B (which refer to inter-RAT carrier frequency information) are replaced by blocks 954, 93 IB, 1004C, and 1006C (which refer to inter-RAT carrier frequency information).

[0120] FIG. 10D shows a flow chart 1000D with example operations of a UE for performing cell measurements based on inter-frequency carrier frequency information and a PLMN ID. FIG. 10D is similar to FIG. 10B except that blocks 952, 931 A, 1004B and 1006B are replaced by blocks 953, 960, 1004D, and 1006D (some of which refer to the inter-frequency carrier frequency information in association with a PLMN ID).

[0121] FIG. 10E shows a flow chart 1000E with example operations of a UE for performing cell measurements based on inter-RAT carrier frequency information and a PLMN ID. FIG. 10E is similar to FIG. 10D except that blocks 953, 1004D, and 1006D (which refer to interfrequency carrier frequency information with associated PLMN IDs) are replaced by blocks 955, 1004E, and 1006C (which refer to inter-RAT carrier frequency information with associated PLMN IDs).

[0122] FIG. 11A shows a flow chart 1100A with example operations of a UE that receives system information configuring inter-frequency carrier frequency information. At block 740, the UE registers to the first PLMN via a satellite. At block 1152, the UE receives system information configuring an inter-frequency carrier frequency. At block 1160A, the UE determines whether the system information configures a PLMN ID associated with the interfrequency carrier frequency. A potential technical advantage of the flow chart 1100A is that in some implementations, the same SIB type can include inter-frequency carrier frequency information for cell reselection purposes and / or for PLMN search purposes. When the systeminformation does not include a PLMN ID associated with the inter-frequency carrier frequency information, the UE might assume that the inter-frequency carrier frequency information is for cell reselection purposes. When the system information indicates a PLMN associated with the inter-frequency carrier frequency information, the UE can consider the inter-frequency carrier frequency information for a PLMN search of a higher priority PLMN.

[0123] From block 1160A, if the system information does not configure a PLMN ID associated with the inter-frequency carrier frequency (i.e., “No” branch of block 1160A), the flow proceeds to block 1182. At block 1182, the UE performs an inter-frequency measurement on the inter-frequency carrier frequency for cell reselection. Otherwise, if the UE determines that the system information configures a PLMN ID associated with the interfrequency carrier frequency (i.e., “Yes” branch of block 1160A), the flow proceeds to block 1170A. At block 1170A, the UE performs one or more PLMN searches to search for a PLMN identified by the PLMN ID on the inter-frequency carrier frequency.

[0124] FIG. 11B shows a flow chart 1100B with example operations of a UE that receives system information configuring inter-RAT carrier frequency information. FIG. 1 IB is similar to FIG. 11A except that blocks 1152, 1160A, 1182 and 1170A (which refer to inter-frequency carrier frequency information) are replaced by blocks 1154, 1160B, 1184 and 1170B (which refer to inter-RAT carrier frequency information).

[0125] FIG. 12 shows another flow chart 1200 with example operations of a UE that manages PLMN selection based on a PLMN access information. At block 730, the UE obtains a PLMN access information. At block 1240, the UE registers to a first PLMN via a first RAT type based on the PLMN access information. At block 1256, the UE receives system information identifying frequencies for a different PLMN or a different RAT type. For example, the system information can be similar to the system information 650, 652, 653, 654, or 655 described in this document. At block 1260, the UE identifies one or more candidate PLMNs based on matching information in the PLMN access information and the system information. At block 1270, the UE performs a PLMN search based on at least a first candidate PLMN of the one or more candidate PLMNs having a higher search order than the first PLMN, where the higher search order is based, at least in part, on the first candidate PLMN having a different RAT type than the first RAT type.

[0126] FIG. 13 A through FIG. 15C provide some examples of implementing one or more PLMN search(es) using periodic PLMN searches and / or event-triggered PLMN searches. In some implementations, the event-triggered PLMN search can be triggered by an NTN-specific triggering condition. In some implementations, the search triggering criteria can be based on parameters that are similar to the cell reselection parameters described in 3GPP TS 36.304 (version 18.0.0, section 5.2.4.7).

[0127] FIG. 13A shows a timing diagram 1300A for periodic PLMN searches. After registering with a VPLMN, a UE performs periodic PLMN searches to search for a higher priority PLMN. In accordance with aspects of this disclosure, when the UE determines that it has registered to a VPLMN via an NTN cell, the UE might perform the periodic PLMN searches (such as PLMN search 1370A, 1370B, and so on) based on a TN search periodicity T 1373. For example, following a start time 1371 for a first PLMN search 1370A, the UE may start a timer set to the duration of the TN search periodicity T 1373. At the expiration 1375 of the timer, the UE performs the next PLMN search 1370B.

[0128] In some implementations, the TN search periodicity T 1373 is a default value preconfigured in the UE. In some implementations, the UE receives a message including the TN search periodicity T from an OTA update server or a device management server. In some implementations, the UE obtains the TN search periodicity T from a USIM, a DL NAS message, or an RRC message. In some implementations, the DL NAS message is an Attach Accept message, a TAU Accept message, a Registration Accept message, or a Configuration Update Command message.

[0129] In some implementations, the UE 102 stops performing a periodic PLMN search to search for the non-satellite PLMN when the UE 102 discovers a suitable TN cell of the nonsatellite PLMN and registers to the non-satellite PLMN via the TN cell. For example, the UE 102 in FIG. 6A through FIG. 6D performs periodic PLMN searches with a TN periodicity T to search for a TN cell of the PLMN 107. The UE 102 stops performing this periodic PLMN search after the UE 102 discovers the suitable TN cell of the PLMN 107 and registers to the PLMN 107 via the TN cell.

[0130] FIG. 13B shows a timing diagram 1300B for event-triggered PLMN searches. FIG. 13B differs from FIG. 13A in that the PLMN searches 1372A and 1372B are triggered by events 1376A and 1376B, respectively, and FIG. 13B does not use a TN search periodicity T.After the UE has registered to the satellite VPLMN, the UE detects a first event 1376A at time ti and performs a PLMN search 1372A to search for the non-satellite PLMN based on the detection of the event 1376A. In this example, the UE might not discover a TN cell of the non-satellite PLMN in the PLMN search 1372 A. Later in time, the UE detects a second event 1376B at time t2 and performs another PLMN search 1372B for a TN cell of the non-satellite PLMN based on the detection of the event 1376B. If the UE discovers a suitable TN cell of the non-satellite PLMN, the UE registers to the non-satellite PLMN via the TN cell.

[0131] In some implementations, the first event 1376A and the second event 1376B can be the same type of event. In some implementations, the first event 1376A and the second event 1376B are based on different event triggering criteria. In some implementations, one of the event(s) is that the UE is within a distance of a reference location (e.g., the UE is within a TN coverage area as described in FIG. 6C). In other implementations, one of the event(s) is that the UE is outside a distance of a reference location (e.g., the UE is going to leave a coverage of a serving satellite cell). For example, the reference location is a Global Navigation Satellite System (GNSS) location. In some implementations, the UE receives information of the reference location and / or information of the distance, e.g., in a SIB, from the satellite VPLMN via a satellite (e.g., the satellite 104) or from a terrestrial cell of a HPLMN, an EHPLMN, or a higher priority PLMN. In some implementations, the SIB is a SIB 19, a SystemInformationBlockType31 or a SystemInformationBlockType31-NB. In other implementations, the SIB is a SIB24 or SIB25. In yet other implementations, the SIB is a new SIB other than the SIBs described above. Other example events might be triggered when the UE is out of coverage from the satellite VPLMN or when the UE is in discontinuous coverage of the satellite VPLMN.

[0132] In some implementations, if the UE discovers a suitable TN cell of the non-satellite PLMN in a PLMN search triggered by detecting an event (e.g., one of the event(s) described above), the UE stops attempting to detect one or more events (e.g., some or all of the event(s) described above). Otherwise, if the UE does not discover a suitable TN cell of the non- satellite PLMN in the PLMN search, the UE continues attempting to detect the event(s).

[0133] FIG. 13C shows a timing diagram 1300C for a combination of event-triggered and periodic PLMN searches. FIG. 13C shows a first PLMN search 1370A occurring at a start time 1371. Based on the timing of the 1370A, the UE might start a timer set to a duration ofthe TN search periodicity T 1373. At time ti (e.g., while the timer for periodic PLMN search is still running), the UE detects an event 1376A associated with triggering an event-triggered PLMN search 1372A. The UE might cancel the timer (shown at arrow 1374) and perform the event-triggered PLMN search 1372A. If the PLMN search 1372 A does not result in a change to a different PLMN, the UE restarts the timer for periodic PLMN searches. The next PLMN search 1370B (following the event-triggered PLMN search 1372A) might occur after a TN search periodicity T. For example, at timer expiration 1375 of the timer, the UE performs the next PLMN search 1370B. As shown in FIG. 13C, the UE can continue performing periodic PLMN searches (e.g., PLMN searches 1370B, 1370C), where the periodicity is interrupted and restarted by an event-triggered PLMN search (e.g., PLMN search 1372B).

[0134] FIG. 13D shows a timing diagram 1300D for event-triggered periodic PLMN searches. In FIG. 13D, when an event is detected (such as at time ti and tz), the UE begins performing periodic PLMN searches for n searches (where n is greater than or equal to one). The value n can be a configurable value. The TN search periodicity T’ might be the same periodicity T described with reference to FIG. 13A or might be a different value. In some implementations, the duration of the TN search periodicity T’ might depend on what event triggered the event-triggered periodic PLMN searches. In the example of FIG. 13D, the UE detects an event at time ti and triggers n=2 periodic PLMN searches 1377A and 1377B. Later, the UE detects an event at time t2 and triggers n=2 periodic PLMN searches 1377C and 1377D.

[0135] FIG. 14A shows a flow chart 1400A with example operations of a UE to enable or disable event-triggered PLMN searches. At block 1440, the UE registers to a first PLMN. At block 1470, in some implementations, the UE performs periodic PLMN searches to search for a second PLMN. At block 1460, the UE determines whether the first PLMN is a satellite PLMN. In some implementations, the inquiry at block 1460 also might depend on whether the first PLMN is a VPLMN. If the first PLMN is a satellite PLMN (i.e., “Yes” branch of block 1460), the flow proceeds to block 1471. At block 1471, the UE enables an event- triggered PLMN search function to search for a second PLMN. For example, the UE might enable monitoring for one or more event-triggering criteria. Otherwise, if the first PLMN is not a satellite PLMN (i.e., “No” branch of block 1460), the flow proceeds to block 1476. At block 1476, the UE disables the event-triggered PLMN search function (e.g., disabling monitoring for the event-triggering criteria).

[0136] FIG. 14B shows a flow chart 1400B with example operations of a UE to enable event-triggered PLMN searches in addition to periodic PLMN searches when the UE is roaming in a satellite PLMN. FIG. 14B includes blocks 1440, 1460, 1470, and 1471 as described with reference to FIG. 14 A. FIG. 14B differs from FIG. 14B in the order and possible combination of the blocks. For example, in FIG. 14B, if the first PLMN is a satellite PLMN (i.e., “Yes” branch of block 1460), the UE enables the event-triggered PLMN search function at block 1471 and also optionally proceeds to block 1470 to perform periodic PLMN searches. Otherwise, if the first PLMN is not a satellite PLMN (i.e., “No” branch of block 1460), the UE might only perform the periodic PLMN searches at block 1470.

[0137] FIG. 15A is a block diagram of an example wireless communication system 1500A implementing a BS 116A (on the ground) connecting to a satellite 104 via an NTN gateway using a transparent payload implementation. The example wireless communication system 1500A uses one type of NTN deployment referred to as transparent payload architecture, which involves an NTN gateway 117 and a “transparent” satellite 104 for extending the range of a Uu interface. The Uu interface refers to the link between the UE 102 and a base station. In some implementations, the satellite 104 implements a frequency conversion and an RF amplifier in both the uplink and downlink directions. With that being said, the satellite 104 function is similar to that of an analogue RF repeater. As a result, the satellite 104 repeats the Uu radio interface from a feeder link (between the NTN gateway 117 and the satellite 104) to the service link (between the satellite 104 and the UE 102) in the downlink direction and vice versa in the uplink direction. The Satellite Radio Interface (SRI) on the feeder link is the Uu interface, and the NTN gateway 117 supports all necessary functions to forward the signal of the Uu interface. The NTN gateway 117 can be placed at the same site as the BS 116A location or can be connected to the BS 116A at a distance via a wired link. It is also possible to connect more than one NTN gateway 117 to a BS 116A. Different transparent satellites may be connected to the same base station on the ground, via the same NTN gateway, or via different NTN gateways.

[0138] FIG. 15B is a block diagram of an example wireless communication system 1500B implementing a BS 1 16A with feeder links to multiple satellites. Two different satellites 104 and 1504 are connected to the same BS 116A via the same NTN gateway 117. The twosatellites 104 and 1504 can each provide different NTN cells on the Earth surface and the different NTN cells can use different Physical Cell IDs (PCIs).

[0139] Although the transparent payload architecture illustrated in FIG. 15A and FIG. 1 B is the current focus of the 3GPP development, the regenerative payload architecture that installs the BS functions on the satellite 104 is also a possible NTN deployment in the future. In such an architecture, the Uu interface exists between the satellite 104 and the UE 102, and some or all of the functions of the BS 116 are on-board the satellite 104 (such as shown in FIG. 15C.

[0140] FIG. 15C illustrates a block diagram of an example wireless communication system 1500C implementing an NTN BS 1 16B onboard on a satellite 104 using a regenerative payload implementation. The BS 116B can perform some or all of the functions of a base station, including those described with reference to BS 116 or BS 116A in this disclosure. The Uu interface is shown between the UE 102 and the BS 116B. The feeder link from the BS 116B to the NTN gateway 117 can be referred to as a Satellite Radio Interface (SRI). The SRI is a transport link between the NTN gateway 1 17 and the satellite 104. The Ng interface from the BS 116B includes a portion over the SRI (shown as Ng over SRI) and a portion on the ground. In some implementations, a first portion of the base station functionality (such as BS 116A) can be implemented on the satellite 104 while a second portion of the base station functionality (shown as BS 116B) can be implemented at a ground entity. For example, in a disaggregated network, BS 116 can be divided into two components: the Distributed Unit (DU) and Centralized Unit (CU). In an example, the BS 116B can operate as a DU that handles baseband processing, including RF signal processing and modulation / demodulation. The BS 116A can be an example CU that manages higher-layer tasks like resource management, scheduling, and network optimization.

[0141] The techniques of this disclosure can apply to the transparent payload architecture as well as the regenerative payload architecture. References to NTN 101 can refer to the BS 116 (which could be implemented as either or both of the BS 116A or BS 116B illustrated in FIG. 1, FIG. 15A, FIG. 15B, or FIG. 15C).

[0142] FIG. 16A shows an example user plane protocol stack in accordance with aspects of this disclosure. FIG. 16A illustrates an example user plane protocol stack 1600A in accordance with aspects of this disclosure. FIG. 16A includes a visual representation of theNTN portion of user plane protocol stack 1600A involving the UE 102, the satellite 104, the NTN gateway 117, the NTN BS 116, and a user plan function (UPF) of a 5G core network. The diagram of the NTN user plane protocol stack is similar to that of the TN, with the addition of two new nodes, the satellite 104 and the NTN gateway 117, being placed in the middle of the NR-Uu interface.

[0143] FIG. 16B shows an example control plane protocol stack in accordance with aspects of this disclosure. As with FIG. 16A, the NTN control plane protocol stack 1600B illustrated in FIG. 16B is also similar to that of a TN, with the addition of the satellite 104 and the NTN gateway 117 being placed in the NR-Uu interface.

[0144] FIG. 17 shows a block diagram of an example wireless communication system 1700 showing hardware features and communication interfaces. The depicted hardware configurations may omit certain components well-understood to be frequently implemented in such electronic devices, such as displays, peripherals, power supplies, and the like. The wireless communication system 1700 includes the same elements as described with reference to FIG. 1, including the UE 102, the BS 106, the BS 116, the satellite 104, and the CN 110. The UE 102 can support at least a 5G NR (or simply, “NR”) or E-UTRA air interface to communicate with the BS 106. The BS 106 connects to the CN 110 via an interface (e.g., SI or NG interface). The BS 106 can connect to other base stations (including the BS 116) via an interface (e.g., X2 or Xn interface) for interconnecting NG RAN nodes.

[0145] The BS 116 (such as either or both of the BS 116A or BS 116B) is equipped with processing hardware 1718 that can include a receiver 1708B configured to receive data in the uplink direction. The processing hardware 1718 can also include a transmitter 1708A configured to transmit data in the downlink direction. The processing hardware further can one or more general-purpose processor(s) 1708C (e.g., CPUs) and a non-transitory computer- readable memory 1708D storing instructions that the one or more general -purpose processors execute. Additionally, or alternatively, the processing hardware 1718 can include specialpurpose processing units. The processor 1708C may include, for example, one or more central processing units, graphics processing units (GPUs), or other application-specific integrated circuits (ASIC), and the like. CRM 1708D may include any suitable memory or storage device such as random-access memory (RAM), static RAM (SRAM), dynamic RAM(DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), or Flash memory usable to store device data of the BS 106.

[0146] The satellite 104 can include processing hardware 1716, such as a transmitter 1706A, a receiver 1706B, a processor 1706C, and CRM 1706D (similar to components 2506, 1708A, 1708B, 1708C and 1708D of the BS 106). The BS 106 can include generally similar components (not shown) as the processing hardware 1718.

[0147] The UE 102 is equipped with processing hardware 1712 that can include one or more general-purpose processors such as CPUs and non-transitory computer-readable memory 1702D storing machine-readable instructions executable on the one or more general-purpose processors, and / or special -purpose processing units. The processing hardware 1712 can also include a transmitter 1702A configured to transmit data in the downlink direction. The processing hardware further can include a receiver 1702B configured to receive data in the uplink direction. The processing hardware 1712, in an example implementation, includes a processor 1702C to process data that the UE 102 will transmit in the uplink direction or process data received by UE 102 in the downlink direction. The processor(s) 1702C may include, for example, one or more central processing units, graphics processing units (GPUs), or other application-specific integrated circuits (ASIC), and the like. To illustrate, the processor(s) 1702C may include an application processor (AP) utilized by the UE 102 to execute an operating system and various user-level software applications, as well as one or more processors utilized by modems or a baseband processor. The computer readable media / memory (CRM) 1702D may include any suitable memory or storage device such as randomaccess memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), Flash memory, solid-state drive (SSD) or other massstorage devices, and the like useable to store one or more sets of executable software instructions and associated data that manipulate the one or more processor(s) 1702C and other components of the processing hardware 1712 to perform the various functions described herein and attributed to the UE 102. The sets of executable software instructions include, for example, an operating system (OS) and various drivers (not shown), and various software applications (not shown), which are executable by processor(s) 1702C to enable user-plane communication, control -plane signaling, and user interaction with the UE 102.

[0148] FIG. 1 through FIG. 17 and the operations described herein are examples meant to aid in understanding example implementations and should not be used to limit the potential implementations or limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some operations differently.

[0149] The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects. While the aspects of the disclosure have been described in terms of various examples, any combination of aspects from any of the examples is also within the scope of the disclosure. The examples in this disclosure are provided for pedagogical purposes. Alternatively, or in addition to the other examples described herein, examples include any combination of the following implementation options (enumerated as clauses for clarity).

[0150] Clause 1. A method for wireless communication by a user equipment (UE) (102), the method including: registering (740) to a first public land mobile network (PLMN) (105) via a non-terrestrial network (NTN) cell; obtaining (730, 750, 952, 953 954, 955) frequency information (130, 150, 630, 650) regarding a second PLMN (107) that has a higher priority than the first PLMN; and performing (770A, 770B, 970A, 970B, 970C, 970D) a PLMN search (170, 670A, 670B, 670C, 670D) based on the frequency information and one or more PLMN search rules.

[0151] Clause 2. The method of clause 1, where the frequency information regarding the second PLMN includes: inter-frequency carrier frequency information, inter-radio access technology (RAT) carrier frequency information, or both inter-frequency carrier frequency information and inter-RAT carrier frequency information.

[0152] Clause 3. The method of clause 1 or 2, where the obtaining the frequency information includes: receiving, from the NTN cell, a system information message that includes the frequency information for the second PLMN.

[0153] Clause 4. The method of clause 3, where the system information message is formatted as at least one of: a previously-defined system information block (SIB) typeassociated with cell reselection or neighbor cell information, where the previously-defined SIB type is modified to carry the frequency information regarding the second PLMN; or a new SIB type formatted to carry the frequency information regarding the second PLMN.

[0154] Clause 5. The method of clause 4, where the previously-defined SIB type is at least one of: a SIB type 4 (SIB4), a SIB type 5 (SIB5), a SIB type 24 (SIB24), or a SIB type 25 (SIB25).

[0155] Clause 6. The method of any one of clauses 1 to 5, where the obtaining the frequency information includes obtaining PLMN access information that includes, for each of a plurality of PLMNs, a combination of: a PLMN ID, and a frequency range.

[0156] Clause 7. The method of clause 6, where the PLMN access information further includes, for each of the plurality of PLMNs, one or more of: a radio access technology (RAT) type, a frequency band number, or a search order parameter.

[0157] Clause 8. The method of clause 6 or 7, where the frequency range is a subset of a full range of frequencies for a frequency band.

[0158] Clause 9. The method of any one of clauses 6 to 8, where the obtaining the frequency information includes: receiving, from the NTN cell, a system information message that includes a PLMN identifier (ID) of the second PLMN; and obtaining the frequency information from the PLMN access information based on the PLMN ID.

[0159] Clause 10. The method of any one of clauses 1 to 4, where the obtaining the frequency information includes: obtaining PLMN access information that includes one or more frequency ranges for each of a plurality of PLMNs; receiving, from the NTN cell, a system information message that includes inter-frequency carrier frequency information or inter-radio access technology (RAT) carrier frequency information, or both; and matching the inter-frequency carrier frequency information, the inter-RAT carrier frequency information, or both, to a first frequency band or a first frequency range for the second PLMN in the PLMN access information.

[0160] Clause 11. The method of any one of clauses 1 to 10, where the one or more PLMN search rules includes at least one of: a PLMN selector list indicating that the second PLMN has the higher priority than the first PLMN; a PLMN search order in the PLMN accessinformation; or a determination that the first PLMN is a Visited PLMN (VPLMN) and that the UE is registered to the VPLMN via the NTN cell.

[0161] Clause 12. The method of any one of clauses 1 to 11, where the one or more PLMN search rules includes a PLMN search rule that a radio access technology (RAT) type of the second PLMN is higher priority compared to a RAT type of the first PLMN.

[0162] Clause 13. The method of any one of clauses 1 to 12, where the performing the PLMN search includes at least one of: performing a periodic PLMN search based on a terrestrial network (TN) search periodicity; performing an event-triggered PLMN search based on at least one search triggering criteria; or performing an event-triggered periodic PLMN search having multiple periodic PLMN searches triggered based on the at least one search triggering criteria.

[0163] Clause 14. The method of clause 13, where the performing the PLMN search includes a combination of the periodic PLMN search and the event-triggered PLMN search, the method further including: performing the event-triggered PLMN search based on the at least one search triggering criteria being satisfied; and resetting a timer for periodic PLMN search based on the performing the event-triggered PLMN search.

[0164] Clause 15. The method of any one of clauses 1 to 14, further including: enabling an event-triggered PLMN search criteria to search for a PLMN based on the first PLMN being a Visited PLMN (VPLMN) and the UE being registered via the NTN cell.

[0165] Clause 16. The method of any one of clauses 1 to 15, further including: discovering one or more cells of the second PLMN based on the PLMN search; selecting a cell from among the one or more cells of the second PLMN; and registering to the second PLMN via the selected cell.

[0166] Clause 17. A method for wireless communication by a network entity of a nonterrestrial network (NTN) (105) in a first public land mobile network (PLMN) (108), the method including: communicating (840) to a UE (102) via an NTN cell; and transmitting (850) frequency information (150, 650) regarding a terrestrial network (TN) in a second PLMN (107).

[0167] Clause 18. The method of clause 17, where the transmitting the frequency information includes at least one of: transmitting (852, 853) inter-frequency carrier frequencyinformation (652, 653), or transmitting (854, 855) inter-radio access technology (RAT) carrier frequency information (654, 655).

[0168] Clause 19. The method of clause 17 or 18, where the transmitting the frequency information includes transmitting a system information message, and where the system information message is formatted as at least one of: a previously-defined system information block (SIB) type associated with cell reselection or neighbor cell information, where the previously-defined SIB type is modified to carry the frequency information regarding the second PLMN; or a new SIB type formatted to carry the frequency information regarding the second PLMN.

[0169] Clause 20. The method of clause 19, where the previously-defined SIB type is at least one of: a SIB type 4 (SIB4), a SIB type 5 (SIB5), a SIB type 24 (SIB24), or a SIB type 25 (SIB25).

[0170] Clause 21. An apparatus, including: a communication unit; and a processing system configured to control the communication unit to implement any one of the methods of any one of clauses 1 to 20.

[0171] Aspects of the subject matter described in this disclosure can be implemented as a computer-readable medium having stored therein instructions which, when executed by a processor, causes the processor to perform any one of the above-mentioned functionalities. Aspects of the subject matter described in this disclosure can be implemented as a system having means for implementing any one of the above-mentioned functionalities. Aspects of the subject matter described in this disclosure can be implemented as an apparatus having one or more processors configured to perform one or more operations from any one of the above- mentioned functionalities.

[0172] The following additional considerations may apply to the foregoing and the following discussions.

[0173] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this specification belongs. The terms “first,” “second,” and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The use of terms “including,” “comprising,” or “having” and variations thereofherein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “connected” and “coupled” are not restricted to physical or mechanical connections or couplings and can include electrical connections or couplings, whether direct or indirect. Furthermore, terms “circuit” and “circuitry” and “control unit” may include either a single component or a plurality of components, which are either active and / or passive and are connected or otherwise coupled together to provide the described function. In addition, the term operationally coupled as used herein includes wired coupling, wireless coupling, electrical coupling, magnetic coupling, radio communication, software based communication, or combinations thereof.

[0174] Some or all of the foregoing or the following implementations can be jointly combined or formed to be a new or another one implementation. The foregoing or the following techniques can be used to solve at least (but not limited to) the issue(s) or scenario(s) mentioned in this disclosure. Any two or more than two of the foregoing or the following paragraphs, (sub)-bullets, points, actions, or claims described in each method / technique / implementation may be combined logically, reasonably, and properly to form a specific method. Any sentence, paragraph, (sub)-bullet, point, action, or claim described in each of the foregoing or the following technique(s) / implementation(s) / concept(s) may be implemented independently and separately to form a specific method. Dependency, such as “based on,” “more specifically,” “where,” or etc., in technique(s) / implementation(s) / concept(s) mentioned in this disclosure is just one possible implementation which would not restrict the specific method.

[0175] Generally speaking, description for one of the above figures can apply to another of the above figures. Examples, implementations and methods described above can be combined, if there is no conflict. An event or block described above can be optional or omitted. For example, an event or block with dashed lines in the figures can be optional. In some implementations, “message” is used and can be replaced by “information element (IE),” and vice versa. In some implementations, “IE” is used and can be replaced by “field,” and vice versa. In some implementations, “configuration” can be replaced by “configurations” or “configuration parameters,” and vice versa. In some implementations, “some” means “one or more.” In some implementations, “at least one” means “one or more.”

[0176] As used herein, the terms “user device”, “user equipment” (for example, UE 102), “wireless communication device”, “mobile communication device”, “communication device”, or “mobile device” refer to any one or all of cellular telephones, smartphones, portable computing devices, personal or mobile multi-media players, laptop computers, tablet computers, smartbooks, Internet-of-Things (loT) devices, palm-top computers, wireless electronic mail receivers, multimedia Internet enabled cellular telephones, wireless gaming controllers, display sub-systems, driver assistance systems, vehicle controllers, vehicle system controllers, vehicle communication system, infotainment systems, vehicle telematics systems or subsystems, vehicle display systems or subsystems, vehicle data controllers, point- of-sale (POS) terminals, health monitoring devices, drones, cameras, media-streaming dongles or another personal media devices, wearable devices such as smartwatches, wireless hotspots, femtocells, broadband routers or other types of routers, and similar electronic devices which include a programmable processor and memory and circuitry configured to perform operations as described herein. Further, the user device in some cases may be embedded in an electronic system such as the head unit of a vehicle or an advanced driver assistance system (ADAS). Still further, the user device can operate as an internet-of-things (loT) device or a mobile-internet device (MID). Depending on the type, the user device can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0177] Certain techniques are described in this disclosure as including logic or a number of components or modules. Modules can be software modules (e.g., code, or machine-readable instructions stored on non-transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module can comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g., as encompassed within a general -purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated andpermanently configured circuitry, or in temporarily configured circuitry (e. , configured by software) may be driven by cost and time considerations.

[0178] When implemented in software, the techniques can be provided as part of the operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general -purpose processors or one or more special-purpose processors.

[0179] As used herein, the terms “component” and “module” are intended to be broadly construed as hardware, firmware, or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, or a combination of hardware and software. As used herein, the phrase “based on” is intended to be broadly construed to mean “based at least in part on.”

[0180] As used herein, a phrase referring to a list of items separated by “or” refers to any combination of those items, including single members. For example, “a, b, or c” is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a and b and c.

[0181] In this disclosure, an expression of “X / Y” may include meaning of any of the following: “X or Y” or “X and Y” or “X and / or Y." An expression of “(A) B” or “B (A)” may include concept of “only B.” An expression of “(A) B” or “B (A)” may include the concept of “A+B” or “B+A.”

[0182] In this disclosure, the term "can" indicates a capability, or alternatively indicates a possible implementation option. The term "may" indicates a permission or a possible implementation option.

[0183] Some aspects are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, or the like.

[0184] The various illustrative components, logic, logical blocks, modules, circuits, operations and algorithm processes described in connection with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware or software, including the structures disclosed in thisspecification and the structural equivalents thereof The interchangeability of hardware, firmware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and processes described above. Whether such functionality is implemented in hardware, firmware or software depends upon the particular application and design constraints imposed on the overall system.

[0185] As described above, some aspects of the subject matter described in this specification can be implemented as software. For example, various functions of components disclosed herein, or various blocks or steps of a method, operation, process or algorithm disclosed herein can be implemented as one or more modules of one or more computer programs. Such computer programs can include non-transitory processor-executable or computer-executable instructions encoded on one or more tangible processor-readable or computer-readable storage media for execution by, or to control the operation of, a data processing apparatus including the components of the devices described herein. By way of example, and not limitation, such storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store program code in the form of instructions or data structures. Combinations of the above should also be included within the scope of storage media.

[0186] Various modifications to the implementations described in this disclosure may be readily apparent to persons having ordinary skill in the art, and the generic principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.

[0187] Additionally, various features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. As such, although features may be described above as acting in particular combinations, and even initially claimed as such, one or more features from aclaimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0188] The drawings may schematically depict one or more example processes in the form of a flowchart or flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In some circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.

Claims

CLAIMSWhat is claimed is:

1. A method for wireless communication by a user equipment (UE) (102), the method comprising: obtaining (630, 730) public land mobile network (PLMN) access information (130, 430, 530) for a first PLMN (105) and a second PLMN (107), the second PLMN having a higher priority than the first PLMN; registering (640, 740, 1240) to the first PLMN via a non-terrestrial network (NTN) cell; receiving (150, 650, 750, 952, 953 954, 955, 1256), from an NTN node of the first PLMN, system information that indicates frequency information (150, 650) for the second PLMN; and performing (170, 670A, 670B, 670C, 670D, 770A, 770B, 970A, 970B, 970C, 970D, 1270) a PLMN search for the second PLMN based on the frequency information and PLMN access information.

2. The method of claim 1, wherein the receiving the system information includes: receiving, from the NTN node, a system information message (641 , 652, 654, 752, 754, 1152, 1154) formatted to carry cell reselection or neighbor cell information of the first PLMN, wherein the system information message carries the frequency information regarding the second PLMN, and wherein the system information message is at least one of: a system information block (SIB) type 4 (SIB4), a SIB type 5 (SIB5), a SIB type 24 (SIB24), or a SIB type 25 (SIB25).

3. The method of claim 1 or 2, wherein the receiving the system information includes: receiving, from the NTN node, a system information message (653, 655, 953, 955) that indicates a PLMN identifier (ID) of the second PLMN; obtaining at least part of the frequency information based on the PLMN ID matching (960, 1160A, 1160B) an entry in the PLMN access information.

4. The method of claim 1, wherein the receiving the system information includes:receiving, from the first PLMN, a system information block (STB) formatted to carry the frequency information and PLMN identifier (ID) for the PLMN search.

5. The method of any one of claims 1 to 4, wherein the frequency information includes: inter-frequency carrier frequency information (652, 653, 752, 952, 953, 1152) for one or more cells of the second PLMN, inter-radio access technology (RAT) carrier frequency information (654, 655, 754, 954, 955, 1154) for one or more cells of the second PLMN, or both the inter-frequency carrier frequency information and the inter-RAT carrier frequency information.

6. The method of claim 5, further comprising: matching (931 A, 93 IB,) the inter-frequency carrier frequency information, the inter- RAT carrier frequency information, or both, to a first frequency band or a first frequency range for the second PLMN in the PLMN access information; and performing the PLMN search for the second PLMN based on the second PLMN having a higher search order in the PLMN access information compared to the first PLMN.

7. The method of any one of claims 1 to 6, wherein the PLMN access information includes, for each of a plurality of PLMNs, any combination of: a PLMN ID (132, 432), a radio access technology (RAT) type (434), PLMN frequency information (136, 436), or a search order parameter (160, 460, 461).

8. The method of any one of claims 1 to 7, wherein the PLMN access information includes, for each of the plurality of PLMNs, one or more of: a frequency band number (437), or a frequency range (438), wherein the frequency range is a subset of a full range of frequencies for a frequency band.

9. The method of any one of claims 1 to 8, wherein the PLMN access information or the system information includes one or more PLMN search rules, the one or more PLMN search rules including at least one of: a PLMN selector list indicating that the second PLMN has the higher priority than the first PLMN; a PLMN search order that prioritizes the second PLMN over the first PLMN; a PLMN search rule that triggers the PLMN search based on the first PLMN being a Visited PLMN (VPLMN) and the UE being registered to the VPLMN via the NTN cell; or a PLMN search rule (460) that a radio access technology (RAT) type of the second PLMN is higher priority compared to a RAT type of the first PLMN.

10. The method of any one of claims 1 to 9, wherein the performing the PLMN search includes at least one of: performing a periodic PLMN search (1370A, 1370B) according to a terrestrial network (TN) search periodicity (1373) based on the UE being camped on the NTN cell; performing an event-triggered PLMN search (1372A, 1372B) based on at least one search triggering criteria (1376A, 1376B) associated with the NTN cell; or performing an event-triggered periodic PLMN search (1377 A, 1377B, 1377C, 1377D) having multiple periodic PLMN searches triggered based on the at least one search triggering criteria.

11. The method of claim 10, wherein the performing the PLMN search includes a combination of the periodic PLMN search and the event-triggered PLMN search, the method further comprising: performing the event-triggered PLMN search (1372A) based on the at least one search triggering criteria (1376A) being satisfied; and resetting (1374) a timer for periodic PLMN search (1370B) based on the performing the event-triggered PLMN search.

12. The method of any one of claims 1 to 11, further comprising: enabling an event-triggered PLMN search criteria for the PLMN search based on the first PLMN being a Visited PLMN (VPLMN) and the UE being registered via the NTN cell.

13. A method for wireless communication by a network entity of a non-terrestrial network (NTN) (101) in a first public land mobile network (PLMN) (105), the method comprising: communicating (640, 840) with a UE (102) via an NTN cell; and transmitting (650, 850), via the NTN cell, system information that indicates frequency information (150, 652, 653, 654, 655, 852, 853, 854, 855) for a terrestrial network (TN) of a second PLMN (107).

14. The method of claim 13, wherein the transmitting the system information includes at least one of: transmitting, from an NTN node of the first PLMN, a system information message formatted to carry cell reselection or neighbor cell information of the first PLMN, wherein the system information message carries the frequency information (653, 655, 853, 855) and a PLMN identifier (ID) of the second PLMN, and wherein the system information message is at least one of: a system information block (SIB) type 4 (SIB4), a SIB type 5 (SIB5), a SIB type 24 (SIB24), or a SIB type 25 (SIB25); or transmitting, from the NTN node, a SIB (856) formatted to carry the frequency information and PLMN ID for one or more PLMNs other than the first PLMN.

15. An apparatus, comprising: a communication unit; and a processing system configured to control the communication unit to implement any one of the methods of any one of claims 1 to 14.

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