Non-terrestrial network (NTN) cell measurement

Abstract

This disclosure provides systems, methods and apparatuses for a user equipment (UE) (102) to measure a non-terrestrial network (NTN) cell (196) while camping on a terrestrial network (TN) cell (184) of a terrestrial network (TN) base station (BS) (106). The TN BS provides system information (120) to the UE to inform the UE regarding NTN cell configurations, frequencies, movement, and / or timing, among other examples. In some implementations, the BS can also provide a configuration of NTN-specific triggering conditions (130) for triggering a cell measurement of an NTN cell. The UE triggers (140) the cell measurement during a cell reselection evaluation if the NTN-specific triggering condition is satisfied. Example NTN-specific triggering conditions include the UE being near the edge of a TN coverage area (180) or the TN BS (106) having a signal quality or signal strength below a threshold of the NTN-specific triggering condition, among other examples.

Description

Docket No.14730662200PCT NON-TERRESTRIAL NETWORK (NTN) CELL MEASUREMENT RELATED APPLICATION

[0001] This application claims the priority benefit of U.S. Provisional Patent Application Serial No.63 / 584,810, filed September 22, 2023, and U.S. Provisional Patent Application Serial No. 63 / 586,491, filed September 29, 2023, both entitled “NON-TERRESTRIAL NETWORK (NTN) CELL MEASUREMENT,” the contents of which are hereby incorporated by reference herein. TECHNICAL FIELD

[0002] This disclosure relates generally to wireless communication and some aspects relate to enabling a user equipment (UE) camping on a terrestrial network (TN) cell to acquire information and criteria for performing a cell reselection evaluation of a non- terrestrial network (NTN) cell. DESCRIPTION OF RELATED TECHNOLOGY

[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. The UE can be configured to select a serving cell based on measurements of signal strength and / or signal quality of available cells. When the UE transitions to an idle or inactive mode, the serving cell becomes a camped cell and the UE is said to be camping on the camped cell. The UE can occasionally perform a cell reselection evaluation based on the signal strength or quality of the camped cell and one or more neighbor cells. For example, a UE can monitor a synchronization signal in cells other than the camped cell. A base station transmits a synchronization signal, such as a Synchronization Signal (SS) and Physical Broadcast Channel (PBCH) Block (SSB), to support cell measurement as well as synchronization. Each cell can have a particularDocket No.14730662200PCT configuration of SSB periodicity, carrier frequency, and / or subframe timing. As part of the cell reselection evaluation (also called “cell reselection”), the UE measures the SSBs of one or more neighbor cells and determines whether to camp on one of the neighbor cells instead of the current camped cell.

[0005] Recent developments in wireless communication technology include the use of non-terrestrial network (NTN) nodes. An NTN refers to a network, or segment of networks, using radio frequency (RF) resources on board a satellite or UAS platform. For example, an NTN node may include a spaceborne vehicle (such as a satellite) or an airborne vehicle (such as an uncrewed aircraft system (UAS)). For simplicity, the discussion below refers to all such apparatus as satellites. The NTN coverage of a satellite can be referred to as an NTN cell to distinguish the NTN cell from cells of a terrestrial network (TN), which can be referred to as a TN cell.

[0006] An NTN-capable UE may initially select a TN cell and register with the network. Thus, the UE is said to camp on the TN cell (as a camped cell). After camping on the TN cell, the UE might move or experience channel conditions that affect its measurements of a neighbor cell or its camped cell. Current procedures for cell reselection evaluation may not provide sufficient information for the UE to measure synchronization signals from an NTN cell or may not distinguish between TN cells and NTN cells. Furthermore, there is a desire to prioritize utilization of TN cells over NTN cells for energy efficiency and bandwidth. Thus, the UE might only need to perform cell measurements of NTN cells in particular scenarios, such as when the TN coverage is poor or when the UE is near the edge of a TN coverage area. 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 a method for wireless communication by a user equipment (UE). The method includes the UE camping on a terrestrial network (TN) cell of a TN base station (BS). The method includes the UE receiving, from the TN BS, non-terrestrial network (NTN)-specific system information about an NTN cell of a satellite, where the NTN- specific system information includes one or more NTN neighbor cell configurationDocket No.14730662200PCT information elements and NTN assistance information. The method includes the UE triggering, as part of a cell reselection evaluation, a cell measurement of a synchronization signal of the NTN cell based, at least in part, on the NTN-specific system information, where the synchronization signal includes a Synchronization Signal (SS) and Physical Broadcast Channel (PBCH) Block (SSB). The method includes the UE obtaining the cell measurement based on an SSB Measurement Timing Configuration (SMTC) for the SSB, where the SMTC is based, at least in part, on the one or more NTN neighbor cell configuration information elements and the NTN assistance information.

[0009] In some implementations, the method includes the UE triggering the cell measurement of the NTN cell based, at least in part, on an NTN-specific triggering condition being satisfied. In some implementations, the NTN-specific triggering condition is based on a location of the UE relative to an edge of a TN coverage area. Alternatively, or additionally, the NTN-specific triggering condition can be based on a threshold measurements of the current camped TN cell such as a reference signal received power (RSRP) threshold and / or a reference signal received quality (RSRQ) threshold for triggering a cell measurement of an NTN cell for cell reselection evaluation. Other example NTN-specific triggering conditions are described in this document. In some implementations, the TN BS uses one or more system information broadcast (SIB) messages to configure the NTN-specific triggering condition.

[0010] Another innovative aspect of the subject matter described in this disclosure can be implemented as a method for wireless communication by a base station (BS) operating a TN cell. The method includes the BS transmitting NTN-specific system information about an NTN cell of a satellite, where the NTN-specific system information includes one or more NTN neighbor cell configuration information elements and NTN assistance information to enable a UE to obtain an cell measurement of the NTN cell as part of a cell reselection evaluation. The method includes the BS transmitting a configuration of an NTN-specific triggering condition to cause the UE to trigger the cell measurement based on the NTN-specific triggering condition being satisfied.

[0011] Another innovative aspect of the subject matter described in this disclosure can be implemented as an apparatus or system. In some implementations, an apparatus includes a communication unit and a processing system. The processing system is configured to control the communication unit to implement any one of the methodsDocket No.14730662200PCT described in this document. Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

[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. Other features, 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 is an example wireless communication system including terrestrial network (TN) coverage and non-terrestrial network (NTN) coverage and showing a user equipment (UE) camping on a TN cell of a TN base station (BS) near the edge of a TN coverage area.

[0015] FIG. 2 is a flow chart showing example operations in accordance with various aspects of this disclosure.

[0016] FIG. 3A is a block diagram of an example wireless communication system implementing an NTN BS and a satellite using a transparent payload implementation.

[0017] FIG. 3B is a block diagram of an example wireless communication system implementing an NTN BS with feeder links to multiple satellites.

[0018] FIG. 4A shows a UE in the idle / inactive state near the center of a TN cell and moving towards the edge of TN coverage.

[0019] FIG.4B shows the UE of FIG.4A near the edge of the TN coverage.

[0020] FIG. 5 shows example Synchronization Signal (SS) and Physical Broadcast Channel (PBCH) Blocks (SSBs) and the need to adjust an SSB-based Measurement Timing Configuration (SMTC) to account for signal propagation delays for NTN cells.

[0021] FIG.6 shows example system information that a TN BS can broadcast to assist a UE with NTN cell measurement.Docket No.14730662200PCT

[0022] FIG. 7 shows example NTN-specific triggering conditions in accordance with various aspects of this disclosure.

[0023] FIG. 8 is a messaging diagram showing an idle UE camping on a TN cell performing NTN cell measurement in accordance with aspects of this disclosure.

[0024] FIG. 9 is a messaging diagram showing an example in which a UE adjusts an SMTC based on linkage information and an NTN neighbor cell configuration.

[0025] FIG. 10 is a messaging diagram showing an example in which a TN BS can provide adjusted SMTCs, where the TN BS has taken into account the NTN propagation delay.

[0026] FIG.11 is a messaging diagram showing an example in which a UE can determine which SMTCs to adjust based on linkage information to match an SMTC to an NTN neighbor cell configuration.

[0027] FIG. 12 is a messaging diagram showing an example in which an NTN-specific triggering condition is based on one or more thresholds configured for triggering an NTN cell measurement.

[0028] FIG. 13 is a messaging diagram showing an example in which an NTN-specific triggering condition is based on TN coverage information indicating a boundary of a TN coverage area.

[0029] FIG. 14 is a messaging diagram showing an example in which an NTN-specific triggering condition is satisfied when other measured cells fail to satisfy a cell reselection criteria.

[0030] FIG. 15 is a messaging diagram showing an example in which an NTN-specific triggering condition is satisfied based on the UE receiving system information about an NTN cell and the UE initiates a cell reselection evaluation.

[0031] FIG.16 is a flow diagram showing example operations of a UE to measure NTN cells based on the inter / intra-frequency configurations and one or more corresponding NTN neighbor cell configurations.

[0032] FIG.17 is a flow diagram showing example operations of a UE to measure NTN cells based on an SMTC for an NTN cell, where the SMTC is provided by a TN BS.

[0033] FIG.18 is a flow diagram showing example operations of a UE to measure NTN cells based on SMTCs and linkage information provided by a TN BS.Docket No.14730662200PCT

[0034] FIG.19 is a flow diagram showing example operations of a UE to measure NTN cells based on a signal condition of the serving TN cell.

[0035] FIG.20 is a flow diagram showing example operations of a UE to measure NTN cells based on TN coverage information.

[0036] FIG.21 is a flow diagram showing example operations of a UE to measure NTN cells based on signal conditions of the serving and neighbor TN cells.

[0037] FIG.22A is a flow diagram showing example operations of a UE to measure NTN cells based on whether the system information used to measure intra-frequency NTN cells is available.

[0038] FIG.22B is a flow diagram showing example operations of a UE to measure NTN cells based on whether the system information used to measure inter-frequency NTN cells is available.

[0039] FIG. 23 is a block diagram of example distributed or disaggregated implementation of an example base station using a centralized unit (CU) and a distributed unit (DU).

[0040] FIG. 24A is a block diagram of an example protocol stack according to which a UE communicates with base stations.

[0041] FIG.24B is a block diagram of an example protocol stack according to which the UE communicates with a CU and a DU.

[0042] FIG. 25A illustrates an example user plane protocol stack in accordance with aspects of this disclosure.

[0043] FIG. 25B illustrates an example control plane protocol stack in accordance with aspects of this disclosure.

[0044] FIG. 26 is a block diagram of an example wireless communication system showing hardware features and communication interfaces. DETAILED DESCRIPTION

[0045] 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) wirelessDocket No.14730662200PCT 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 (IOT) network, such as a system utilizing 4G, 5G, WiFi or future radio technology.

[0046] This disclosure provides systems, methods and apparatuses for a user equipment (UE) to measure a non-terrestrial network (NTN) cell while camping on a terrestrial network (TN) cell of a terrestrial base station (BS). The BS of the TN can provide system information to the UE to inform the UE regarding NTN cell configurations, frequencies, movement, and / or timing, among other examples. In some implementations, the BS can also provide a configuration of NTN-specific triggering conditions (which may be referred to as triggering conditions in this document) for NTN cell measurement. NTN cell measurement refers to a cell measurement of an NTN cell (as opposed to a cell measurement of any cell that may include TN or NTN cells). NTN-specific triggering conditions can limit processor overhead and energy consumption by preventing the UE from triggering an NTN cell measurement until the triggering condition is satisfied. When a triggering condition is satisfied, the UE can measure the NTN cell as part of a cell reselection evaluation and determine whether to camp on the NTN cell based on a result of the NTN cell measurement.

[0047] This disclosure includes several examples of signaling and types of information that the BS can provide. For example, the BS can provide NTN-specific system information (such as an NTN neighbor cell configuration) via a system information broadcast (SIB) message or radio resource control (RRC) message. In some implementations, the BS provides NTN timing information such as timing of synchronization signals or ephemeris information about the satellite providing an NTN cell. In some implementations, the BS provides NTN-specific thresholds specifically for triggering NTN cell measurement, such that, when the UE triggers a cell reselection evaluation based on a non-NTN-specific threshold and the camped TN cell signal strength or signal quality is below the NTN-specific threshold, the UE triggers cell measurements of NTN cells to consider them in the cell reselection evaluation. In some implementations,Docket No.14730662200PCT the BS provides TN coverage information (such as geographic information, coverage area boundaries, cell radius, or other information to enable the UE to determine when the UE is approaching the edge of a TN coverage area) which may be incorporated into the trigger for an NTN cell measurement. In some implementations, one BS (which is at the edge of a TN coverage area) may provide the system information for NTN cell measurement while another BS (which is not at the edge of the TN coverage area) does not provide information for NTN cell measurement. Thus, the presence of the system information for NTN cell measurement can inform the UE that it is at an edge cell of the TN coverage area.

[0048] This disclosure includes several example triggering conditions, such as based on UE location, TN signal quality, and / or thresholds, among other examples. In some implementations, a triggering condition is satisfied when the UE determines that it is located at edge of TN coverage area based on the UE's geographic position relative to a boundary of the TN coverage area or relative to a center of an edge cell of the TN coverage area. In some implementations, the UE can determine that the triggering condition is satisfied based on a TN cell signal strength or signal quality being below both an NTN- specific threshold and a general threshold for initiating a cell reselection evaluation. Alternatively, or additionally, the UE can determine that the triggering condition is satisfied and trigger a cell measurement of an NTN cell after determining that no other cells (excluding the NTN cell) satisfy a cell reselection criteria.

[0049] During neighbor cell measurement for a cell reselection evaluation, the UE measures a synchronization signal, such as the Synchronization Signal (SS) and Physical Broadcast Channel (PBCH) Block (SSB). Although the examples in this disclosure are based on the SSB, other types of synchronization signals or reference signals can be used for cell measurement. Typically, the BS provides an SSB-based Measurement Timing Configuration (SMTC) to the UE to enable the UE to determine timing for the SSB, such as the SSB periodicity setting and the burst duration. Some system information messages are capable of providing information about a carrier frequency and a corresponding SMTC. However, absent the techniques of this disclosure, a UE may be unable to determine which SMTCs are associated with TN cells and which are associated with NTN cells. Because NTN cells are operated by satellites and often larger distances from the UE, the propagation delay for SSBs from NTN cells can be greater than the propagation delay for SSBs from TN cells. Therefore, it is desirable to adjust SMTCs for NTN cells so that the UE can properly receive the SSBs at the correct timing.Docket No.14730662200PCT

[0050] In some implementations, the system information message (or a new system message) can include linkage information to assist the UE in determining that an SMTC is for a particular NTN cell. For example, the linkage information can be a Physical Cell Identity (PCI), a carrier frequency, or an NTN cell index value that matches a corresponding PCI, carrier frequency, or NTN cell index for the NTN cell in a message that contains an NTN neighbor cell configuration. In some implementations, after the UE determines that an SMTC is associated with an NTN cell, the UE adjusts the SMTC to account for propagation delay or an NTN-specific timing offset. The adjusted SMTC can be based on the NTN neighbor cell configuration. For example, the NTN neighbor cell configuration can indicate measurement timing information, ephemeris information, an epoch time, tracking area (TA) parameters, and / or a Kmacvalue indicating a scheduling offset for downlink and uplink frame timing. The UE might use these parameters to adjust the SMTC. In some implementations, the UE can determine its geographic position and adjust the SMTC for an NTN cell based on its geographic position and ephemeris information about the satellite operating the NTN cell. In some implementations, the UE adjusts the SMTC associated with the NTN cell based on movement of the satellite, position information, relative distance between the UE and the satellite, among other examples.

[0051] Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Generally speaking, the techniques of this disclosure enable an NTN-and-TN-capable UE to measure NTN cells while camping on a TN cell. The various implementations of NTN-specific triggering conditions can reduce energy consumption by prioritizing the TN cells when the UE is within a TN coverage area and / or the TN cells are providing satisfactory signal strength and quality. Conversely, the UE can perform cell measurement of NTN cells when the UE is near a boundary of the TN coverage area or when the signal strength or quality of TN cells are below configured thresholds. In some implementations, the TN BS can configure the NTN-specific triggering conditions to limit the occurrence of NTN cell measurements, thereby reducing UE power consumption and providing prioritization to TN cells when they are available.

[0052] FIG.1 is an example wireless communication system 100 including TN coverage and NTN coverage and showing a UE 102 camping on a TN cell 184 of a TN BS 106 near the edge of a TN coverage area 180. Several base stations (shown as TN BS 106, 106',Docket No.14730662200PCT and 106'') operate TN cells. For example, TN BS 106 operates a first cell 184 and BS 106' operates a different cell 186. Collectively, the coverage area served by the cells of TN BS 106, 106', and 106'' can be referred to as a TN coverage area 180. To extend or augment service, the example wireless communication system 100 includes a non-terrestrial network (NTN). The NTN includes a satellite 108, an NTN gateway 198, and an NTN BS 109. In some deployments, some operations of the NTN BS 109 can be collocated with the satellite 108. The NTN gateway 198 provides a ground station that communicatively couples the satellite 108 to the NTN BS 109. The TN BS 106, 106', and 106'' and the NTN BS 109 are part of one or more radio access networks, collectively referred to as RAN 101. The RAN 101 (such as the TN BS 106, 106', and 106'' and the NTN BS 109) are communicatively coupled to a core network 199. The CN 199 can be implemented as an evolved packet core (EPC), a fifth generation (5G) core (5GC), or a sixth generation (6G) core.

[0053] In some implementations, the TN BS 106, 106', and 106'' implement different radio technologies. For example, the 106 can be a next generation base station (gNB) and can operate the cell 184 as a new radio (NR) cell. The BS 106' can be a legacy type of base station (such as ng-eNB or eNB) and operates the cell 186 as an evolved universal terrestrial radio access (E-UTRA) cell. The cells 184 and 186 can be in the same Radio Access Network Notification Areas (RNA) or different RNAs. The RAN 101 can include any number of base stations, and each of the base stations can cover one, two, three, or any other suitable number of cells. The UE 102 can support at least a 5G NR (or simply, “NR”) or E-UTRA air interface to communicate with the base stations 106, 106', or 106''. Similarly, the satellite 108 can operate the NTN cell 196 as a NR cell or other radio access technology.

[0054] The UE 102 can operate in different connectivity states such as connected, idle, or inactive states. A radio resource control (RRC) connected state (referred to as RRC_CONNECTED) refers to a state in which the UE 102 has an active radio connection with any of the base stations 106, 106', 106'', or 109. An idle state (referred to as RRC_IDLE) refers to a state in which the UE 102 does not have an active radio connection and is not configured with an RRC connection. An inactive state (referred to as RRC_INACTIVE) means that the UE 102 does not have an active radio connection but is configured with the RRC connection in a suspended state. As discussed in detail below, the UE 102 and / or the RAN 101 may utilize the techniques of this disclosure when the UEDocket No.14730662200PCT 102 is in an idle or inactive state. The UE 102 is said to be camped on a TN cell in the idle / inactive state. For clarity, the examples below refer to the RRC_INACTIVE or RRC_IDLE state of the RRC protocol. To simplify the following description, the term “idle state” is used and can represent the RRC_IDLE or the RRC_INACTIVE state, and the term “connected state” is used and can represent the RRC_CONNECTED state.

[0055] One objective of the 5G technology (and beyond) is to provide a unified framework for such types of communication as enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine type communication (mMTC). The 5G technology relies primarily on legacy terrestrial networks. However, the 3GPP organization has proposed to extend 5G communications (and beyond) to non-terrestrial networks (NTNs). An NTN refers to a network, or segment of networks, using radio frequency (RF) resources on board an NTN node (such as satellite or an airborne platform). NTN nodes extend coverage of a terrestrial cellular network. In some implementations, an NTN node implements 5G NR technologies or Long-Term- Evolution (LTE) technologies tailored for the Narrowband Internet-of-Thing (NB-IoT) or the enhanced Machine Type Communication (eMTC) scenarios. Example NTN nodes include spaceborne vehicles (such as a satellite) or airborne vehicle (such as an unmanned aircraft system (UAS) or High-Altitude Platform Systems (HAPS)). Airborne platforms can include 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. 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 108. An NTN gateway 198 (sometimes also referred to as a "sat-gateway") connects the satellite 108 to NTN BS 109 or other data network resources.

[0056] A satellite 108 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. The footprints of the beams typically have an elliptic shape and depend on the on-board antenna configuration and the elevation angle. For a transparent payload implementation, a satellite can apply RF filtering and frequency conversion and amplification, and not change the waveform signal. For a regenerativeDocket No.14730662200PCT payload implementation, a satellite 108 can apply RF filtering, frequency conversion and amplification, demodulation and decoding, routing, and coding / modulation. This approach is effectively equivalent to implementing most of the functions of an NTN BS 109, e.g., a gNB.

[0057] The 3GPP specifications provide a cell reselection evaluation procedure that the UE 102 can follow to reselect a better performing cell. For example, while the UE 102 is camped on the cell 184 of the TN BS 106. The UE 102 can initiate a cell reselection evaluation to measure synchronization signals (such as the SSB) of other cells. The TN BS 106 provides system information (such as via a system information broadcast (SIB) message) to inform the UE 102 about the carrier frequencies and timing information for SSBs of neighbor cells. The TN BS 106 can transmit SMTCs about various SSBs of neighbor cells. If the TN BS 106 only includes SMTCs for TN neighbor cells (such as cell 186), the UE 102 may not be able to measure the SSBs from the NTN and the UE 102 may not find a suitable cell. For example, the UE 102 may be located at an edge of the TN coverage area 180 and may receive poor signal quality from the TN cells. If the TN BS 106 does not inform the UE 102 about potential NTN cells (such as the NTN cell 196), the UE 102 will not measure NTN cells from the NTN coverage 190. If the UE 102 moves out of the TN coverage area 180, the UE 102 may be out of network coverage and would need to search for a cell from scratch. This could take more time than necessary and / or disrupt service continuity. Thus, one solution to enable the UE 102 to measure the SSBs from NTN cells (such as the SSB 162 from the satellite 108) is for the TN BS 106 to indicate the carrier frequency and timing information of the SSB 162.

[0058] To assist the UE 102 to discover the NTN cell 196, the TN BS 106 can transmit system information 120 about an NTN neighbor cell configuration. The system information 120 can also be referred to as NTN-specific system information. The NTN neighbor cell configuration informs the UE 102 about NTN cells, such as the NTN cell 196 from the satellite 108. Under current 3GPP specifications, when the TN BS 106 transmits SMTCs for SSBs, the SMTCs of TN cells are not distinguished from those for the NTN cells. This can create some additional problems as described further with reference to FIG. 5 because the SSBs from TN cells and NTN cells have different propagation delays. Thus, one aim of this disclosure is to enable a UE 102 to identify and adjust SMTCs for NTN cells.Docket No.14730662200PCT

[0059] In addition to timing considerations, there is a desire to limit when or where the UE 102 conducts measurements of NTN cells. Measuring NTN cells can cause additional power consumption and delay which should be avoided when the UE 102 is not at the edge of the TN coverage area 180. Conversely, when the UE 102 is near an edge of the TN coverage area 180, the UE 102 should perform cell measurements of NTN cells so that the UE 102 can avoid a complete loss of service if the UE 102 leaves the TN coverage area 180. The UE 102 can implement an NTN-specific triggering condition to determine when it should trigger a cell measurement of an NTN cell. When the NTN-specific triggering condition is satisfied, the UE 102 can trigger a cell measurement of the NTN cell (referred to as NTN cell measurement), such as by measuring the signal strength or quality of the SSB 162 for the NTN cell 196.

[0060] As described further, the NTN-specific triggering condition can be based on location of the UE 102 (such as within a threshold distance of a boundary of the TN coverage area 180 or a threshold distance from a center of a cell center location. Alternatively, or additionally, the NTN-specific triggering condition can include thresholds for the TN cells that enable the UE 102 to determine that it is near the edge of the TN coverage area 180. In some implementations, the TN BS 106 can transmit a configuration of NTN-specific triggering condition(s) 130.

[0061] FIG.2 is a flow chart showing example operations 200 in accordance with various aspects of this disclosure. For example, the operations 200 of FIG.2 can be performed by a UE (such as the UE 102 described with reference to any of figures in this disclosure). Although FIG. 2 depicts a particular sequence of operations, the sequence may be altered without departing from the scope of the present disclosure. For example, some of the operations depicted may be performed in parallel or in a different sequence.

[0062] In block 202, the UE camps on a TN cell of a TN BS (such as TN BS 106). For example, the UE may be in an idle state or an inactive state. In block 210, the UE optionally receives, from the TN BS, system information including carrier frequencies and SMTCs of candidate cells for a cell reselection evaluation. For example, the UE can receive a system information broadcast message (such as SIB4 or SIB2) from the TN BS.

[0063] At block 220, the UE receives, from the BS, system information (e.g., NTN- specific system information) about an NTN cell (such as the NTN cell 196) of a satellite 108. For example, the system information can be formatted as a SIB or RRC message. The system information can include one or more NTN neighbor cell configurationDocket No.14730662200PCT information elements (IEs). Each NTN neighbor cell configuration IE can be specific to each NTN cell or group of NTN cells. The system information in block 220 is related to NTN cells and the system information may be included in a SIB19 (or new SIB type).

[0064] In block 230, the UE optionally receives, from the BS, a configuration of NTN- specific triggering condition(s). In block 240, the UE triggers a cell measurement of an NTN cell based on an NTN-specific triggering condition. The NTN-specific triggering condition can be based on the configuration received in block 230 or an NTN-specific triggering condition programmed at the UE.

[0065] In block 250, the UE optionally adjusts the SMTC for the NTN cell. For example, the UE can determine which SMTCs from the SIB4 or SIB2 messages are related to NTN cells based on linkage information. Linkage information can be any information from the SIB4 or SIB2 that matches corresponding information from the system information received in block 220. After determining which SMTCs are related to NTN cells, the UE can adjust those SMTCs to account for propagation delay or other NTN-specific timing considerations.

[0066] In block 260, the UE obtains the cell measurement of the SSB from the NTN cell. In block 270, the UE performs the cell reselection evaluation based on the cell measurement from the NTN cell. As an example, the cell reselection evaluation may be similar to the process described in 3GPP TS 38.304 section 5.2.4. In a cell reselection evaluation, the UE generally searches for a cell providing the highest priority and / or highest signal metric from among measured cells. By using the NTN-specific triggering condition described in this disclosure, the UE can refrain from measuring NTN cells until the NTN-specific triggering condition is satisfied. Thus, one potential technical advantage of this disclosure is that a UE can prioritize TN cells over NTN-cells when the TN coverage is adequate to satisfy cell reselection criteria.

[0067] FIG.3A is a block diagram of an example wireless communication system 300A implementing an NTN BS 109 and a satellite 108 using a transparent payload implementation. The example wireless communication system 300A uses one type of NTN deployment referred to as transparent payload architecture, which involves an NTN gateway 198 and a “transparent” satellite 108 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 108 implements a frequency conversion and an RF amplifier in both the uplink and downlink directions. With that being said, the satellite 108 functionDocket No.14730662200PCT is similar to that of an analogue RF repeater. As a result, the satellite 108 repeats the Uu radio interface from a feeder link (between the NTN gateway 198 and the satellite 108) to the service link (between the satellite 108 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 198 supports all necessary functions to forward the signal of the Uu interface. The NTN gateway 198 can be placed at the same site as the NTN BS 109 location, or can be connected to the NTN BS 109 at a distance via a wired link. It is also possible to connect more than one NTN gateway 198 to an NTN BS 109. Different transparent satellites may be connected to the same base station on the ground, via the same NTN gateway, or via different NTN gateways.

[0068] FIG.3B is a block diagram of an example wireless communication system 300B implementing an NTN BS 109 with feeder links to multiple satellites. Two different satellites 108 and 308 are connected to the same NTN BS 109 via the same NTN gateway 198. The two satellites 108 and 308 can each provide different NTN cells on the Earth surface and the different NTN cells can use different Physical Cell IDs (PCIs).

[0069] In terms of the satellite moving pattern, there are at least three types of service links that are supported in NTN. In a first type (referred to as “Earth-fixed”), the service link is provisioned by beam(s) continuously covering the same geographical areas all the time (e.g., the case of GEO / GSO satellites). In a second type (referred to as “quasi-Earth- fixed”), the service link is provisioned by beam(s) covering one geographic area for a limited period and a different geographic area during another period (e.g., the case of LEO / MEO satellites capable of using steerable beams). In a third type (referred to as “Earth-moving”), the service link is provisioned by beam(s) whose coverage area slides over the Earth surface (e.g., the case of LEO / MEO satellites using fixed or non-steerable beams). With LEO / MEO satellites, the NTN BS 109 can provide either quasi-Earth-fixed cell coverage or Earth-moving cell coverage. With GEO satellites, the NTN BS 109 can provide Earth fixed cell coverage.

[0070] Although the transparent payload architecture illustrated in FIG.3A and FIG.3B is the current focus of the 3GPP development, the regenerative payload architecture that installs the BS functions on the satellite 108 is also a possible NTN deployment in the future. In such an architecture, the Uu interface exists between the satellite 108 and the UE 102, and some or all of the functions of the NTN BS 109 are on-board the satelliteDocket No.14730662200PCT 108. The techniques of this disclosure can apply to the transparent payload architecture as well as the regenerative payload architecture.

[0071] FIG. 4A shows a UE in the idle / inactive state near the center of a TN cell and moving towards the edge of TN coverage. Shown at time T1, the UE 102 is at the center of a TN cell (i.e., cell i) and is moving toward the edge of cell i. At a certain point of time (such as when the signal metric of the cell i falls below a threshold), the UE 102 initiates a cell reselection evaluation. During the cell reselection evaluation, the UE measures signal metrics of the neighboring cells (such as cell j) and uses the measurement results to evaluate the cell reselection criteria. The cell reselection criteria can include one or more criterion, such as priority level, minimum signal strength, performance, or other criterion. The cell reselection criteria can be configured by the network, such as via a SIB or RRC message from a base station.

[0072] FIG. 4B shows the UE of FIG. 4A near the edge of the TN coverage. In a first scenario in FIG.4B, consider that the TN BS has not informed the UE 102 about the NTN cell (e.g., cell k). As the UE 102 moves toward the edge of the TN coverage (e.g., the right side of cell i), the UE 102 would not be able to detect any TN cell (such as cell j) because the UE 102 is at an edge of the TN coverage area. As a result, the UE 102 can become completely out of network coverage when it leaves cell i. The UE enters the ‘any cell selection’ state (a state defined in 3GPP TS 38.304). In the ‘any cell selection’ state, the UE 102 performs the cell selection by scanning all the RF channels, which takes significant time.

[0073] In a second scenario of FIG. 4B, the TN cell provides information related to the nearby NTN cells (e.g., cell k). For example, the BS operating cell i can provide system information including the measurement configurations for the neighboring NTN cells. It is desirable for the UE 102 to use an NTN-specific triggering condition for initiating the NTN cell measurement of cell k because initiating the NTN cell measurement consumes additional UE power. For the NTN cell measurement, the UE calculates the extra propagation delay caused by a potentially long distance between the UE 102 and the satellite 108. For instance, if UE 102 in FIG. 4A is moving from the cell center of cell i towards cell j (instead of towards cell k), it is desirable for UE 102 to refrain from triggering the NTN cell measurement of cell k. Even if the TN cell i has provided the measurement configuration for cell k, the UE 102 can implement an NTN-specific triggering condition to determine whether it should expend the extra power and timeDocket No.14730662200PCT associated with measuring the NTN cell k. As long as a UE is not at the edge of the TN coverage, the UE can prioritize searching for and camping on a TN cell because the TN cell is usually more capable of providing higher data throughput and lower access latency (compared to the NTN cell).

[0074] FIG. 5 shows example SSBs 500 and the need to adjust an SMTC to account for signal propagation delays for NTN cells. A UE 102 operating in a certain cell must be able to detect reference signals from the neighboring cells and measure the strength of the reference signals to be able to switch to a qualified neighboring cell when needed (i.e., when the serving cell is no longer able to serve the UE due to poor signal reachability), or in order to add a new Carrier Component (CC). The reference signal a base station can use for this purpose with the NR radio interface is the Synchronization Signal (SS) and physical broadcast channel (PBCH) block, abbreviated as SSB. Unlike the LTE radio interface in which a base station transmits SS every 5 ms, 5G NR allows each base station to transmit the SSB burst with different time patterns, with the longest periodicity of up to 160 ms. This allows the network to configure the SSB transmission in a more dynamic manner dependent on the actual usage and channel condition. This approach helps to avoid unnecessary measurements and reduce the power consumption of a UE 102. However, this flexibility comes at the cost of the additional signaling required to inform the UE 102 when to perform measurement on a measurement target. Without the additional signaling, the UE would need to assume the worst-case scenario (in the implementation above, the 5 ms periodicity) to determine when to measure the target. The additional signaling in 5G NR is known as “SSB based measurement timing configuration (SMTC),” which contains a periodicity setting ranging from 5 ms to 160 ms and a duration setting ranging from 1 ms to 5 ms.

[0075] The network does not need to align the SMTC periodicity setting with the actual SSB burst periodicity. For instance, the SMTC periodicity can be set to a value larger than the SSB burst periodicity to further reduce the power consumption of the UE 102. In addition to the periodicity and duration settings, the SMTC also indicates a timing offset to inform the UE 102 of the exact subframe where the UE 102 should start monitoring the SSB burst, which occurs repeatedly according to the periodicity setting. A base station can signal the periodicity and the timing offset settings together, in one measurement object, as a single parameter periodicityAndOffset.Docket No.14730662200PCT

[0076] There can be a relatively small timing difference between the timing of the Primary Cell (PCell) and the timing of the measurement target, in part due to the propagation delay difference. A terrestrial network can ignore this small timing difference, as the propagation delay difference is small and hence requires no adjustment in the timing offset setting. Accordingly, 3GPP TS 38.331 (version l6.6.0) currently specifies only one timing offset for the measurement object configuration. For an NTN, however, the propagation delay between a satellite and the UE 102 UE could be longer (e.g., up to 25.77 ms), and the variance for different satellites 108 and 308 can be significant (e.g., between 8 ms and 25.77 ms).

[0077] A UE 102 and / or a base station 106 can use an individual timing offset setting associated with each respective measurement target configured in a measurement object. This approach can result in multiple timing offsets settings or even multiple SMTCs configured in one measurement object. Although a measurement object can support two SMTCs, these SMTCs currently must share the same timing offset setting and hence cannot address the propagation delay issue in an NTN discussed above.

[0078] Now referring to FIG. 5, the TN BS 106 currently is serving the UE 102 and has configured the UE 102 with a measurement object to perform the measurement on SSBs from NTN neighbor cells (from satellites 108 and 308). The distance between the UE 102 and the TN BS 106 is DTN, the distance between the UE 102 and the satellite 108 is DA, and the distance between the UE 102 and the satellite 308 is DB, where in this example DB> DA> DTN. The propagation delay between the UE 102 and the TN BS 106 is ΔtTN, the propagation delay between the UE 102 and the satellite 108 is ΔtA, and the propagation delay between the UE 102 and the satellite 308 is ΔtB, where ΔtTNexceeds ΔtA by a small amount over the duration of one subframe and ΔtBexceeds ΔtA. For the purposes of this discussion, one can further assume that the satellite 108 and the satellite 308 both emit an SSB burst at subframe 2 and subframe 7 for one subframe duration. If the TN BS 106 configures the UE 102 with an SMTC in which the periodicity equals 5 subframes, the offset equals 2 and the duration equals 1 subframe. However, the existing techniques do not account for the propagation delay difference between an NTN cell and a TN cell. So, the UE 102 cannot measure the SSB from the satellite 308 because the actual SSB burst arrives at the UE 102 during subframe 3 and subframe 8. In some implementations, the TN BS 106 can account for the difference between propagation delays when configuring the offset in the SMTC. Alternatively, the UE 102 can adjust the SMTCs for SSBs fromDocket No.14730662200PCT NTN cells using a calculated timing offset. To determine the propagation delay difference accurately, the TN BS 106 or the UE 102 might use the geolocation of the UE 102 (e.g., a set of Global Positioning Service (GPS) coordinates or other suitable coordinates) and the ephemeris information for the satellite. The SMTC could be valid only for a short period of time due to fast movement of the satellite. To compensate for the rapid offset change due to the fast satellite movement, the network could provide the up-to-date SMTC configuration to UE 102 very frequently or the UE 102 can calculate the offset when it triggers the NTN cell measurement. To prevent unnecessary power consumption calculating the timing offset, the UE 102 would determine which SMTCs are associated with NTN cells and adjust those SMTCs after an NTN-specific triggering condition for initiating the NTN cell measurement is satisfied.

[0079] As described further in this disclosure, the UE 102 must determine which SMTCs are associated with NTN cells and which are associated with TN cells. Current techniques for communicating the SMTCs do not distinguish SSBs are for TN cells or NTN cells. In accordance with aspects of this disclosure, the TN BS 106 can include SMTCs for NTN cells in an NTN neighbor cell configuration IE of the SIB19. Alternatively, or additionally, the TN BS 106 can include linkage information (such as a PCI or NTN cell index value) with SMTCs in the SIB4 or SIB2 so that the UE 102 can identify those SMTCs that match linkage information in the SIB19. Alternatively, the UE 102 can try to find a linkage based on matching carrier frequencies in the SMTC from SIB4 and the NTN neighbor cell configuration IE in the SIB19. In some implementations, the TN BS 106 can provide the linkage information or NTN-specific offsets in a new SIB message, the SIB19, or an RRC message.

[0080] FIG. 6 shows example system information 600 that a TN BS can broadcast to assist a UE with NTN cell measurement. A first type of system information 600 can be referred to as cell reselection evaluation information 610. For example, the cell reselection evaluation information 610 can be included in a SIB4 or SIB2 message. The cell reselection evaluation information 610 can include a list of carrier frequencies and SMTC(s) associated with each frequency 612. The cell reselection evaluation information 610 (or a different SIB or RRC message) can include general thresholds (not shown) that inform the UE to perform a cell reselection evaluation. For example, the general thresholds may be legacy thresholds that are not specific to TN or NTN cell measurements. In some implementations, the cell reselection evaluation information 610 can also includeDocket No.14730662200PCT linkage information (to map SMTCs in TN system information message to an NTN cell based on NTN PCI, NTN cell index, or NTN carrier frequency) 614.

[0081] A second type of system information can be referred to as NTN-specific system information 620. In this disclosure, the terms “system information about an NTN cell” (or similar phrases) and “NTN-specific system information” can be used interchangeably. In some implementations, the NTN-specific system information 620 can be included in a SIB19 message. The NTN-specific system information 620 can include an NTN neighbor cell configuration 622 (such as in an NTN neighbor cell configuration IE) and NTN assistance information 623 (such as NTN timing information 624). In some implementations, the NTN assistance information 623 includes an adjusted SMTC or timing offset for NTN cell 625 that the network has calculated to account for propagation delay.

[0082] A third type of system information can be referred to as a configuration of an NTN-specific triggering condition 630. The configuration of NTN-specific triggering condition 630 can include an NTN-specific measurement threshold(s) to trigger NTN cell measurement 632, TN coverage information 638, and / or other NTN-specific triggering conditions 639.

[0083] The NTN-specific measurement thresholds 632 may be different from the general thresholds included in the cell reselection evaluation information 610, that generally initiate cell reselection evaluation. Because the general thresholds are not specific to TN or NTN cells, they do not distinguish whether to include NTN cell measurements (or not) when performing the cell reselection evaluation. In some implementations, the NTN- specific measurement thresholds 632 are more restrictive than the general thresholds. For example, the general thresholds can cause the UE to initiate the cell reselection evaluation when the signal metric of the camped cell goes below the general thresholds. However, the UE will include only TN cells when the signal metric is below the general threshold but not below the NTN-specific measurement threshold 632. When the signal metric of the camped cell is below the NTN-specific measurement threshold 632, the UE will measure and consider NTN cells as part of the cell reselection evaluation.

[0084] The TN coverage information 638 can include location data, such as cell location, distance, coverage radius, or geographic map information to indicate a boundary of the TN coverage area, among other examples. In some implementations, the TN coverage information 638 can include a distance threshold as part of the NTN-specific triggeringDocket No.14730662200PCT condition. Alternatively, or additionally, the distance threshold can be preconfigured or a standard value in the UE. When a UE determines its location is less than the threshold distance from the boundary of the TN coverage area, the NTN-specific triggering condition is satisfied and the UE can include NTN cells in its cell reselection evaluation. In some implementations, when a UE determines its location is greater than the threshold distance from the center of the TN coverage area, the NTN-specific triggering condition is satisfied and the UE includes NTN cells in its cell reselection evaluation.

[0085] FIG. 7 shows example NTN-specific triggering conditions 740 in accordance with various aspects of this disclosure. While several example NTN-specific triggering conditions 740 are briefly described with reference to FIG. 7, additional details of each NTN-specific triggering condition and further examples are described with reference to FIG. 8 through FIG. 22B. Furthermore, the example NTN-specific triggering conditions 740 can be used individually or in any combination of NTN-specific triggering criteria. In some implementations, a UE monitors two or more NTN-specific triggering conditions such that the UE triggers NTN cell measurement after any single NTN-specific triggering condition is satisfied or when multiple NTN-specific triggering conditions are satisfied.

[0086] In the first example 742, the NTN cells are measured and considered for the cell reselection evaluation when a TN cell signal strength or signal quality (of the TN cell that the UE is currently camping on (i.e., the serving cell)) is below an NTN-specific measurement threshold. For example, the NTN-specific measurement threshold can be lower than a general (non-NTN-specific) measurement threshold associated with initiating a cell reselection evaluation.

[0087] In a second example 746, the NTN cells are measured and included in a cell reselection evaluation only after the UE determines that no measured cell satisfies the cell reselection criteria. In some implementations, the UE determines which SMTCs are only associated with NTN cells (such as using linkage information) and refrains from measuring the SSBs for those SMTCs until after it has determined that no cell from the other SMTCs satisfy the cell reselection criteria. In some implementations, the UE initially attempts to measure the SSBs from all SMTCs (which may be for TN or NTN cells) but because the UE does not adjust the SMTCs for NTN cells until the NTN-specific triggering condition those cell measurements may not satisfy the cell reselection criteria. After determining that no measured cell satisfies the cell reselection criteria, the NTN-specific triggering condition 746 is satisfied. After triggering the NTN cell measurement, the UE adjustsDocket No.14730662200PCT those SMTCs that are linked to NTN cells and is then able to obtain the cell measurements for the NTN cells.

[0088] In a third example 747, the NTN-specific triggering condition is satisfied when the UE determines that the general cell reselection criteria is satisfied and TN BS has provided NTN neighbor cell configuration (e.g., NTN-specific triggering condition is implicitly satisfied by the availability of NTN cell information). In a fourth example 748, the NTN-specific triggering condition is satisfied when the UE determined that it is located at an edge of TN coverage area based on its position location (such as within a threshold distance of a boundary of the TN coverage area or more than a threshold distance from a center of the TN cell at the edge of the TN coverage area). The above examples are provided for pedagogical purposes and other NTN-specific triggering conditions 749 are possible.

[0089] FIG. 8 through FIG. 22B describe several detailed examples to show how the system information and NTN-specific triggering conditions of FIG. 6 and FIG. 7 can be implemented. The detailed examples are intended to aid the reader of this disclosure to obtain an understanding of how NTN-specific aspects of cell reselection evaluation differ from a traditional approach where TN cells and NTN cells are not distinguished.

[0090] An example aspect includes a method for a UE to determine how to measure NTN cells while camping on a TN cell. The UE receives, from a BS, a SIB4 including a list of carrier frequencies and the measurement timing information (SMTCs) associated to each of the carrier frequencies, where the carrier frequency or the measurement timing information can optionally be associated with an NTN cell index value pointing to an entry of an NTN cell configuration list. The UE can receive, from the BS, a SIB2 including the measurement timing information, where each measurement timing information can be associated with an NTN cell index pointing to an entry of an NTN cell configuration list. The UE receives, from the BS, via the system information or via a RRC message, a list of NTN cell configurations, where each NTN cell configuration in the list may include the ephemeris information, an epoch time, the common TA parameters and a Kmacvalue. The UE adjusts the timing offset of a measurement timing information based on the UE geographic position and the associated NTN cell configuration, where the UE identifies the associated NTN cell configuration based on linkage information.

[0091] Another example aspect includes a method for a UE to determine whether to conduct the intra / inter-frequency measurement on NTN cells. Intra-frequency cellDocket No.14730662200PCT reselection refers to a process of selecting a new cell within the same frequency band as the current cell. Inter-frequency cell reselection refers to a process of selecting a new cell in a different frequency band than the current cell. The UE receives, from a BS, via the system information or via an RRC message, an NTN-specific triggering condition for triggering the intra-frequency or inter-frequency measurement of NTN cells. For example, the NTN-specific triggering condition can include NTN-specific measurement thresholds. The UE determines whether the reference signal strength or the reference signal quality of the camped TN cell is below the NTN-specific measurement threshold. If so, the UE conducts the intra-frequency measurement on the intra-frequency NTN cells if the reference signal strength or the reference signal quality of the camped TN cell is below the NTN-specific measurement threshold for triggering the intra-frequency measurement. The UE conducts the inter-frequency measurement on the inter-frequency NTN cells if the reference signal strength or the reference signal quality of the camped TN cell is below the NTN-specific measurement threshold for triggering the inter-frequency measurement.

[0092] FIG. 8 is a messaging diagram 800 showing an idle UE camping on a TN cell performing an NTN cell measurement in accordance with aspects of this disclosure. In FIG.8, UE 102 initially connects to the TN cell 184 managed by the TN BS 106 and then transitions to the idle state 202. While remaining in the idle state 202, the UE 102 optionally receives system information 210 including the carrier frequencies and the SMTCs associated to each carrier frequency. The system information 210 may be included in a system information message (e.g., SIB4). The UE 102 can also receive a system information message (e.g., SIB2) including one or more multiple SMTCs associated to the serving carrier frequency.

[0093] The UE 102 receives system information 220 about NTN cells. In the example of FIG. 8, the system information 220 about NTN cells includes information about NTN cell 196 operated by the satellite 108. The system information 220 can include carrier frequencies, PCI, ephemeris information, or other information about the NTN cell 196 or the satellite 108.

[0094] In some implementations, the UE 102 receives a configuration of NTN-specific triggering condition(s) 230, where the NTN-specific triggering condition must be satisfied before the UE 102 includes the NTN cell in the cell reselection evaluation. In some implementations, the UE 102 may receive NTN-specific triggering conditions via an RRCDocket No.14730662200PCT message, at an earlier timing while being in the connected state (not shown). After receiving the NTN-specific triggering conditions, the UE 102 can evaluate the conditions and determine whether to trigger the measurement of NTN neighbor cells during as part of a cell reselection evaluation. When the NTN-specific triggering condition is satisfied and the UE initiates a cell reselection evaluation, the UE can trigger a cell measurement of the NTN cell 196 so that the result of the NTN cell measurement can be included the cell reselection evaluation. The phrases “triggering an NTN cell measurement” or “triggering a cell measurement of an NTN cell” (or similar verbiage) means that the UE 102 determines that it will measure a signal metric of the SSB from the NTN cell. At block 260, the UE obtains the cell measurement of the SSB 162 from the NTN cell 196.

[0095] In some implementations, after triggering the cell measurement (block 240) the UE 102 needs to determine how to conduct the measurement on NTN cells based on the timing information provided in SMTCs (210) and the NTN neighbor cell configurations (220). The UE 102 may adjust (250) the SMTC (from system information 210) for NTN cell 196 as described further below with reference to FIG.9.

[0096] The UE 102 obtains (260) the cell measurement (e.g., RSRP, RSRQ, or SINR values) of the SSB 162 from the NTN cell 196. Based on the obtained measurement results and the cell reselection criteria, the UE 102 performs (270) a cell reselection evaluation. In the example of FIG. 8, the UE 102 determines that the NTN cell 196 satisfies the cell reselection criteria. Following the determination, the UE 102 performs (875) a procedure for reselecting the NTN cell 196 and camps on it. The procedure for reselecting and camping on a cell is well-known and documented. In the event that the NTN cell 196 is in a different tracking area (TA) than the TN cell 184, the UE 102 may sent a TA update via the NTN cell 196 to the network to inform the network that it is no longer camped on the cell 184 (of one TA) and is now camped on the NTN cell 196 (of another TA).

[0097] Having described the concepts in FIG. 2 and FIG. 8 with consistent numbering, it should be apparent that the features of FIG.8 provide additional detail with reference to FIG.2. For FIG.9 through FIG.15, the features that have the same numbering as FIG. 2 and FIG. 8 have the same or essentially similar meaning as described with reference to FIG. 2 and FIG.8. Additionally, where ones and tens digits of the reference numbers are consistent among the various figures, those features have similar operations. For brevity, this disclosure will describe the differences in each of the Figs.9 through 15 compared to the example in FIG. 8.Docket No.14730662200PCT

[0098] FIG.9 is a messaging diagram 900 showing an example in which a UE 102 adjusts an SMTC based on linkage information and an NTN neighbor cell configuration. In FIG. 9, the system information (described as system information 210 in FIG.8) includes a first system information message (e.g., SIB4) 912A and a second system information message (e.g., SIB2) 912B. The first system information message 912A includes cell reselection information for inter-frequency cell reselection. The second system information message 912B includes the carrier frequencies and the SMTC(s) associated to each carrier frequency, including inter-frequency, intra-frequency, and inter-RAT frequencies for cell reseletion. Thus, the combination of the system information messages 912A and 912B can provide the UE 102 with several candidate carrier frequencies and SMTCs that the UE 102 might consider during cell reselection evaluation depending on intra-frequency or inter-frequency cell reselection criteria. Absent the techniques of this disclosure (such as described in FIG. 11), the system information messages 912A and 912B might not explicitly indicate which carrier frequencies and SMTCs are related to NTN cells versus TN cells.

[0099] The system information message (e.g., SIB19) 920 includes NTN neighbor cell information. The system information message (e.g., SIB19) 920 can include a separate NTN neighbor cell configuration IE (i.e., NTN-NeighCellConfig) per NTN neighbor cell, where the NTN neighbor cell configuration IE contains the carrier frequency and the Physical Cell Identity (PCI) used by the NTN neighbor cell. The system information message 920 also contains the satellite-related information of the NTN neighbor cell (e.g., ntn-Config) including the ephemeris information, the common TA parameters, the Kmacvalue (the same Kmacas in 3GPP TS 38.300 (ver.17.5.0), section 16.14.2.1), and the epoch time. In some implementations, if the UE 102 receives a system information message 920 that includes only the NTN neighbor cell configurations without including the NTN serving cell configuration (e.g., SIB19 including only NTN-NeighCellConfigs), the UE 102 determines that the serving cell is a TN cell and the serving TN cell is providing the information for measuring the NTN cells. In the example of FIG. 9, one of the NTN neighbor cell configuration IEs includes information about NTN cell 196 operated by the satellite 108.

[0100] In some implementations, after triggering the cell measurement (block 240) the UE 102 adjusts (250) the SMTC (from message 912A or 912B) that is related to the SSB from NTN cell 196. At 952, the UE 102 first determines the linkages between the SMTCsDocket No.14730662200PCT received in the event 912A or 912B and the neighbor cell configuration IEs received in the event 920. That is, the UE 102 first checks if an SMTC listed in SIB2 or SIB4 includes a PCI that also appears in the NTN neighbor cell configuration IE in SIB19. If the PCI from the SIB2 or SIB4 matches the PCI in the NTN neighbor cell configuration IE, the UE 102 “links” the SMTC to the NTN neighbor cell configuration. The term “link” or “linkages” refers to a relationship by which the UE can associate data from two different messages. Although a matching PCI is one type of linkage information, other types of linkage information can be present. For example, the UE 102 can link the SMTC to a neighbor cell configuration based on a determination that the carrier frequency associated to that SMTC also appears in the neighbor cell configuration in SIB19. Additionally, or alternatively, (as described with reference to FIG.11, the SIB4 or SIB2 can include linkage information (such as an NTN cell index value) with one or more of the SMTCs, where the linkage information refers to an NTN cell value in the NTN neighbor cell configuration.

[0101] After the linkages between the SMTCs and NTN neighbor cell configurations are determined, the UE 102 adjusts 954 the timing offsets of the SMTC(s) based on the UE's position and NTN assistance information (e.g., ntn-Config) for NTN neighbor cell configurations linked to the SMTC(s). In the event 954, the UE 102 does not adjust the SMTC(s) that are not linked to any NTN neighbor cell configurations. Thus, the operation of block 954 is specific to those SMTC(s) that are for NTN cells. To adjust the SMTCs for NTN cells, the UE 102 shifts / delays the timing offset of an SMTC by the amount of the extra propagation delay caused by the service-link and part of the feeder-link, where the service-link is the link between the satellite payload and the UE and the feeder-link is the link between the base station on the ground and the satellite payload. The UE 102 can calculate the distance and hence the theoretical propagation delay of the service-link based on the satellite ephemeris information, the epoch time, and the UE geographic position (such as obtained by the UE using Global Positioning System (GPS), global navigation satellite system (GNSS) or similar technologies). The UE 102 can obtain the propagation delay of a portion of the feeder-link (i.e., between the uplink time synchronization reference point and the satellite payload) by acquiring the common TA parameters in the system information 920.

[0102] After adjusting the SMTC for the NTN cell 196, the UE 102 can properly receive and measure the SSB 162. At block 260, the UE 102 obtains the cell measurement as described previously.Docket No.14730662200PCT

[0103] FIG.10 is a messaging diagram 1000 showing an example in which a TN BS can provide adjusted SMTCs, where the TN BS has taken into account the NTN propagation delay. In FIG.10, the UE 102 may or may not receive the frequency information and the SMTC(s) from SIB2 / SIB4. Focusing on the system information about NTN cells, FIG.10 differs from FIG. 9 by replacing the system information message 920 (as in FIG. 9) with a different example of system information 1020 in FIG. 10. In FIG. 10, the network has calculated adjusted SMTCs or timing offsets for the NTN cell 196. The system information 1020 includes a list of NTN cells and also the timing information used to measure the NTN cells, where the timing information can be the SMTCs for the NTN cells that have taken into account the extra propagation delay caused by the service-link and feeder-link of an NTN system.

[0104] After triggering the cell measurement of the NTN cell (240), the UE 102 in FIG. 10 may not further adjust the SMTC(s) because the SMTC(s) received in the system information 1020 have already been adjusted by the network based on the actual propagation delay in an NTN system. The UE 102 can proceed with the cell measurement (1065) using the timing information (i.e., SMTCs) received in the system information 1020.

[0105] FIG. 11 is a messaging diagram 1100 showing an example in which a UE can determine which SMTCs to adjust based on linkage information to match an SMTC to an NTN neighbor cell configuration. FIG. 11 differs from FIG. 9 because the system information 1114A and 1114B (similar to system information 912A and 912B, respectively) also includes linkage information to explicitly indicate which SMTCs in the SIB4 and SIB2 are related to NTN cells. For example, the system information 1114A (e.g., SIB4) includes the carrier frequencies and the SMTCs associated to each carrier frequency, where each carrier frequency or SMTC can also include linkage information. In the example of FIG. 11, the linkage information is an NTN cell index (referred to as “index”) indicates a corresponding NTN cell configuration in the system information 1120 (e.g., SIB19). The system information 1120 includes a list of NTN cell configurations including at least one NTN neighbor cell configuration for the NTN cell 196. The NTN cell index in SIB4 or SIB2 (1114A or 1114B) can refer to which NTN cell configuration the UE should link the carrier frequency or SMTC. If it is the carrier frequency associated with an NTN cell index, all the SMTCs associated to the carrier frequency refer to the same NTN cell configuration indicated by the NTN cell index value. If a carrier frequencyDocket No.14730662200PCT or a SMTC in SIB4 or SIB2 is not associated with an NTN cell index value, that carrier frequency / SMTC should be considered as the carrier frequency / SMTC used by TN cells.

[0106] The system information message 1112 includes a list of NTN cell configurations, where each NTN cell configuration contains the satellite-related information of a particular NTN cell including the ephemeris information, the common TA parameters, the Kmacvalue, and the epoch time. The first NTN cell configuration in the list is indexed with the number ‘1’ (or ‘0’), and the k-th NTN cell configuration in the list is indexed with the number k (or k - 1). The index numbers UE 102 received in the system information 1114A or 1114B are referring to the indices in the list of NTN cell configurations in the system information 1120.

[0107] After triggering the cell measurement of the NTN cell (block 240), the UE 102 adjusts (1154) the timing offset of each SMTC associated to an index number, based on corresponding NTN cell configuration. The UE 102 does not adjust the SMTCs that are not associated with an index number.

[0108] FIG. 12 is a messaging diagram 1200 showing an example in which an NTN- specific triggering condition is based on one or more thresholds configured for triggering an NTN cell measurement. The one or more thresholds configured for triggering an NTN cell measurement can be referred to as NTN-specific measurement thresholds. In FIG.12, the UE 102 receives the NTN-specific triggering condition in a system information message 1232 (such as a SIB19 or a new type of SIB). The system information message 1232 includes RSRP and RSRQ thresholds for triggering the intra-frequency and / or inter- frequency measurement on NTN cells. These RSRP / RSRQ thresholds can be denoted as SIntraSearchP_NTN(the RSRP threshold for triggering the intra-frequency NTN measurement), SIntraSearchQ_NTN(the RSRQ threshold for triggering the intra-frequency NTN measurement), SnonIntraSearchP_NTN(the RSRP threshold for triggering the inter-frequency NTN measurement), and SnonIntraSearchQ_NTN(the RSRQ threshold for triggering the inter- frequency NTN measurement). The RSRP / RSRQ thresholds in the system information 1232 can be different than the general thresholds for triggering a cell reselection evaluation, and can be referred as NTN-specific measurement thresholds that the UE 102 must satisfy before including the NTN cells in the cell reselection evaluation.

[0109] After receiving the RSRP / RSRQ thresholds 1232, the UE 102 evaluates the cell selection receive level (“Srxlev") and cell selection quality (“Squal"), where the Srxlev and Squal are described in 3GPP TS 38.304 (ver.17.5.0) and shown in Table 1.Docket No.14730662200PCT Srxlev = Qrxlevmeas– (Qrxlevmin+ Qrxlevminoffset) – Pcompensation- QoffsettempSqual = Qqualmeas– (Qqualmin+ Qqualminoffset) - QoffsettempSrxlev Cell selection RX level value (dB) Squal Cell selection quality value (dB)Qoffsettempoffset temporarily applied to a cell as specified in TS 38.331(dB)QrxlevmeasMeasured cell RX level value (RSRP) QqualmeasMeasured cell quality value (RSRQ) Minimum required RX level in the cell (dBm). If the UE supports SUL frequency for this cell, Qrxlevminis obtained from q-RxLevMinSUL, if present, in SIB1, SIB2 and SIB4, additionally, if QrxlevminoffsetcellSULis present in SIB3 and SIB4 for the concerned cell, this cell specific offset is added to the Qrxlevmincorresponding Qrxlevmin to achieve the required minimum RX level in the concerned cell; else Qrxlevminis obtained from q-RxLevMin in SIB1, SIB2 and SIB4, additionally, if Qrxlevminoffsetcellis present in SIB3 and SIB4 for the concerned cell, this cell specific offset is added to the corresponding Qrxlevmin to achieve the required minimum RX level in the concerned cell. Minimum required quality level in the cell (dB). Additionally, Q if Qqualminoffsetcellqualminis signalled for the concerned cell, this cell specific offset is added to achieve the required minimum quality level in the concerned cell. offset to the signalled Qrxlevmintaken into account in the Srxlev Qrxlevminoffset evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN, as specified in TS 23.122. offset to the signalled Qqualmintaken into account in the Squal Qqualminoffset evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN, as specified in TS 23.122. For FR1, if the UE supports the additionalPmax in the NR-NS- PmaxList, if present, in SIB1, SIB2 and SIB4: max(PEMAX1–PPowerClass, 0) – (min(PEMAX2, PPowerClass) – P min(PEMAX1, PPowerClasscompensation)) (dB); else: max(PEMAX1–PPowerClass, 0) (dB) For FR2, Pcompensationis set to 0.Docket No.14730662200PCT For IAB-MT, Pcompensationis set to 0. Maximum TX power level of a UE may use when transmitting on the uplink in the cell (dBm) defined as PEMAXin TS 38.101. If UE supports SUL frequency for this cell, PEMAX1and PEMAX2PEMAX1, PEMAX2are obtained from the p-Max for SUL in SIB1 and NR-NS- PmaxList for SUL respectively in SIB1, SIB2 and SIB4 as specified in TS 38.331, else PEMAX1and PEMAX2are obtained from the p-Max and NR-NS-PmaxList respectively in SIB1, SIB2 and SIB4 for normal UL as specified in TS 38.331. PPowerClassMaximum RF output power of the UE (dBm) according to theUE power class as defined in TS 38.101-1.Table 1. If both “Srxlev > SIntraSearchP_NTN” and “Squal > SIntraSearchQ_NTN” are true, the UE 102 needs not to trigger the intra-frequency measurement on NTN cells. Otherwise, the UE 102 triggers (block 1242) the intra-frequency measurement on NTN cells. Similarly, the UE 102 also evaluates if both “Srxlev > SnonIntraSearchP_NTN” and “Squal > SnonIntraSearchQ_NTN” are true. If both conditions are true, the UE 102 needs not to trigger the inter-frequency measurement on NTN cells. Otherwise, the UE 102 triggers (block 1242) the inter-frequency measurement on NTN cells. In some implementations, the network configures the values of SIntraSearchP_NTN,SIntraSearchQ_NTN,SnonIntraSearchP_NTN,and SnonIntraSearchQ_NTNsuch that SIntraSearchP_NTNis always smaller than SIntraSearchP(the legacy threshold defined in 3GPP TS 38.304 (v17.5.0), section 5.2.4.7.0), SIntraSearchQ_NTNis always smaller than SIntraSearchQ(the legacy threshold defined in 3GPP TS 38.304 (v17.5.0), section 5.2.4.7.0), SnonIntraSearchP_NTNis always smaller than SnonIntraSearchP(the legacy threshold defined in 3GPP TS 38.304 (v17.5.0), section 5.2.4.7.0), and SnonIntraSearchQ_NTNis always smaller than SnonIntraSearchQ(the legacy threshold defined in 3GPP TS 38.304 (v17.5.0), section 5.2.4.7.0).

[0110] In FIG. 12, the UE 102 determines 1242 to trigger a cell measurement for intra- frequency and inter-frequency measurement on NTN cell and proceeds with operations in blocks 250, 260, 270, and 875 as described with reference to FIG. 2 and FIG. 8. In some implementations of block 250, the UE 102 can perform the operations of blocks 952 and 954 (determining linkage and adjusting SMTCs for NTN cells) as described with reference to FIG.9.Docket No.14730662200PCT

[0111] FIG. 13 is a messaging diagram 1300 showing an example in which an NTN- specific triggering condition is based on TN coverage information indicating a boundary of a TN coverage area. The operations of FIG. 13 are similar to the features described with reference to FIG. 8. However, FIG. 13 differs from FIG. 8 in that the TN BS 106 provides system information 1338 that includes TN coverage information. The TN coverage information may include a list of TN areas, where each TN area may contain a TN reference location and a coverage radius / distance threshold, and may also contain a TN area identity. The UE 102 determines whether the NTN-specific triggering condition is satisfied based on whether the UE is within the radius (or distance) of any of the TN areas listed in the TN coverage information. The UE 102 triggers (1348) the NTN cell measurement, if the UE 102 is not within the radius (or distance) of any of the TN coverage areas. The UE 102 determines if it is within the radius / distance of a TN coverage area by examining whether the distance between the UE geographic position and the reference location of the TN coverage area is larger than the radius or distance threshold associated to the TN coverage area. Alternatively, the TN coverage information can indicate a boundary of the TN coverage area and the UE 102 can trigger (1348) the NTN cell measurement when the UE 102 is within a threshold distance of the boundary. Both of the above-mentioned examples are techniques for the UE to determine whether it is approaching the geographic edge of a TN coverage area.

[0112] FIG. 14 is a messaging diagram 1400 showing an example in which an NTN- specific triggering condition is satisfied when other measured cells fail to satisfy a cell reselection criteria. For example, the UE mayThe message diagram in FIG. 14 is similar to that in FIG. 8, with the differences discussed below. In FIG. 14, after receiving the system information 220 including the information used to measure NTN cells, the UE 102 further receives a system information message 1416 including RSRP thresholds for triggering NTN cell measurement. A first RSRP threshold (denoted as Qthres_s) is for the for the serving (camped) cell and a second RSRP threshold is for the best neighbor cell (denoted as Qthres_n). The UE 102 determines whether to trigger (1446) the measurement of NTN cells based on the comparison between the RSRP of the serving cell 184 and Qthres_s, and also based on the comparison between the RSRP of the strongest neighbor cell and Qthres_n. For example, the UE 102 will trigger the measurement on NTN cells if Qmeas,s<= Qthres_sand Qmeas,n<= Qthres_n, where Qmeas,sis RSRP measurement quantity of the serving cell, and Qmeas,nis RSRP measurement quantity of the strongest neighbor cell. InDocket No.14730662200PCT another example, the UE 102 will trigger the measurement on NTN cells, if Rs<= Qthres_sand Rn<= Qthres_n, where Rsis the cell-ranking criterion for serving cell and Rnis the cell- ranking criterion for the strongest / best neighbor cell. The following are the definitions of Rsand Rn, captured from 3GPP TS 38.304 (v17.5.0) and shown in Table 2. Rs= Qmeas,s+ Qhyst- QoffsettempRn= Qmeas,n- Qoffset - QoffsettempQmeasRSRP measurement quantity used in cell reselections. For intra-frequency: Equals to Qoffsets,n, if Qoffsets,nis valid, Qoffset otherwise this equals to zero. For inter-frequency: Equals to Qoffsets,nplus Qoffsetfrequency, if Qoffsets,nis valid, otherwise this equals to Qoffsetfrequency. Qoffsettempoffset temporarily applied to a cell as specified in TS 38.331. Table 2.

[0113] In some implementations, the UE 102 performs a first instance of a cell reselection evaluation using cell measurements that do not include some NTN cells. For example, the UE 102 can identify which SMTCs are linked to NTN cells (such as using linkage information or any of the techniques described with reference to FIG. 2, FIG. 5, FIG. 6, FIG.7, FIG.9, or FIG.11). In the first instance of the cell reselection evaluation, the UE can exclude those SMTCs that have been linked to NTN cells. If no cell satisfies the cell reselection criteria during the first instance of the cell reselection evaluation, the UE 102 can consider the NTN-specific triggering condition satisfied and trigger cell measurements of NTN cells (including any adjustments to the SMTCs for the NTN cells) for a second instance of the cell reselection evaluation.

[0114] In some implementations, the UE 102 performs the first instance of the cell reselection evaluation by attempting to measure the SSBs using SMTCs that it has received in system information messages (e.g., SIB2 and SIB4) without identifying which SMTCs are associated with NTN cells. In the first instance, because the UE 102 has not triggered NTN cell measurement, the UE 102 does not adjust the SMTCs for NTN cells. Therefore, the UE 102 is not expected to successfully measure the SSBs for the NTN cells. If, for the first instance of the cell reselection evaluation, the UE 102 determines that the RSRP of the camped TN cell (Qmeas,s) and the RSRP of the strongest measured neighbor cell (Qmeas,n) are both below the corresponding thresholds (Qthres_s and Qthres_n, respectively), the UE 102 can consider the NTN-specific triggering condition satisfied andDocket No.14730662200PCT trigger the NTN cell measurement. The UE 102 can identify SMTCs that are linked to NTN cells and adjust those SMTCs before performing a second instance of the cell reselection evaluation.

[0115] It is possible that an SMTC can be applicable to both TN and NTN cells. In such situations, the UE 102 performs the first instance of the cell reselection evaluation based on the SMTC without adjusting the SMTC so that the cell measurement is based on the SSB from the TN cell. If no cell satisfies the cell reselection criteria during the first instance, then the NTN-specific triggering condition is satisfied and the UE 102 triggers a cell measurement for the NTN cell as part of a second instance of the cell reselection evaluation. In the second instance of the cell reselection evaluation, the UE 102 adjusts the SMTC for the NTN cell so that the UE 102 can successfully obtain a cell measurement of the SSB of the NTN cell.

[0116] FIG. 15 is a messaging diagram 1500 showing an example in which an NTN- specific triggering condition is satisfied based on the UE receiving system information about an NTN cell and the UE initiates a cell reselection evaluation. In FIG. 15, after receiving the system information 220 including the information used to measure NTN cells, the UE 102 determines whether to trigger the NTN cell measurements based on the legacy criteria / rules for initiating intra-frequency and / or inter-frequency measurement (i.e., the measurement rules for cell re-selection defined in 3GPP TS 38.304 (v17.5.0), section 5.2.4.2). For clarity, FIG.15 shows the TN cell reselection triggering criteria 1517 as a separate message, but it can also be included in any of the system information messages (e.g., SIB4, SIB2) described previously. The UE 102 will trigger (1547) the intra-frequency measurement on NTN cells, if the camped cell 184 does not fulfil Srxlev > SIntraSearchPand Squal > SIntraSearchQ. Similarly, the UE 102 will trigger (1547) the inter- frequency measurement on NTN cells if the camped cell 184 does not fulfil Srxlev > SnonIntraSearchPand Squal > SnonIntraSearchQ.

[0117] Having described the message flow diagrams of FIG. 8 to FIG. 15 to illustrate several example implementations, the operations of those figures can be described as flow diagrams FIG. 16 to FIG. 22B. The example operations of FIG. 16 to FIG. 22B can be implemented by a UE (e.g., UE 102 in this disclosure) camping on a TN cell (e.g., cell 184) and operating in the idle state. Note that the sequence of the example operations of FIG. 16 to FIG. 22B (particularly the order of various system information messages) can occur in a different order than illustrated in the figures.Docket No.14730662200PCT

[0118] FIG. 16 is a flow diagram showing example operations 1600 of a UE 102 to measure NTN cells based on the inter / intra-frequency configurations and one or more corresponding NTN neighbor cell configurations. In FIG.16, the UE 102 determines how to measure NTN cells based on cell reselection triggering criteria (i.e., the inter / intra- frequency configurations) and the NTN neighbor cell configurations. Initially, at block 1612A, the UE receives, from a BS, a SIB4 including a list of carrier frequencies and the SMTC(s) associated to each carrier frequency, where each SMTC may contain a list of PCIs. The UE also receives, at block 1612B, from the BS, a SIB2 including SMTC(s), where each SMTC may contain a list of PCIs. The UE also receives, at block 1620, from the BS, via the system information or via a RRC message, an NTN neighbor cell configuration (e.g., an NTN-NeighCellConfig IE) per NTN neighboring cell, where the NTN neighbor cell configuration may include a carrier frequency, a PCI, the ephemeris information, an epoch time, the common TA parameters and a Kmacvalue.

[0119] The flow then proceeds to block 1652, where the UE determine which SMTC(s) provided in 1612A and 1612B is applicable to the NTN measurement, where the determination is either based on the mapping between the PCIs received in 1620 and the PCIs received in 1612A or 1612B, or based on the mapping between the carrier frequencies received in 1620 and the frequencies received in 1612A.

[0120] FIG.17 is a flow diagram showing example operations 1700 of a UE to measure NTN cells based on an SMTC for an NTN cell, where the SMTC is provided by a TN BS. The flow diagram in FIG. 17 is similar to that in FIG. 2, with the differences discussed below. At block 1612A, the UE receives, from a BS, a SIB4 including a list of carrier frequencies and the SMTC(s) associated to each carrier frequency, where each SMTC may contain a list of PCIs. The UE also receives, at block 1612B, from the BS, a SIB2 including SMTC(s), where each SMTC may contain a list of PCIs. The UE also receives, at block 1725, from the BS, via the system information or via an RRC message (e.g., an RRC Release message), a list of NTN cells (PCIs) and the information used to measure each of the NTN cells, where the information used to measure an NTN cell includes a carrier frequency and a SMTC, and may also include the ephemeris information, an epoch time, the common TA parameters, and a Kmacvalue. In one implementation, if the information used to measure an NTN cell includes only an SMTC and a carrier frequency, the UE conducts the measurement on the carrier frequency and / or the associated PCI based on the timing information provided in the SMTC. In another implementation, if the informationDocket No.14730662200PCT used to measure an NTN cell further includes the ephemeris information, an epoch time, the common TA parameters, and a Kmacvalue, the UE first adjusts / shift the timing offset of the SMTC based on the actual propagation delay caused by the service-link and part of the feeder-link, and then conducts the measurement on the carrier frequency and / or the associated PCI based on the adjusted timing offset and the periodicity of the SMTC.

[0121] FIG.18 is a flow diagram showing example operations 1800 of a UE to measure NTN cells based on SMTCs and linkage information provided by a TN BS. The flow diagram in FIG. 18 is similar to that in FIG. 2, with the differences discussed below. At block 1814A, the UE receives, from a BS, a SIB4 including a list of carrier frequencies and the SMTC(s) associated to each of the carrier frequencies, where the carrier frequency or the SMTC can be associated with an index pointing to an entry of an NTN cell configuration list. The UE also receives, at block 1814B, from the BS, a SIB2 including SMTC(s), where each SMTC can be associated with an index pointing to an entry of an NTN cell configuration list. The UE also receives, at block 1820, from the BS, via the system information or via a RRC message, a list of NTN cell configurations, where each NTN cell configuration in the list may include the ephemeris information, an epoch time, the common TA parameters and a Kmacvalue.

[0122] FIG.19 is a flow diagram showing example operations 1900 of a UE to measure NTN cells based on a signal condition of the serving TN cell. The flow diagram in FIG. 19 is similar to that in FIG.2, with the differences discussed below. At block 220, the UE receives from a BS, the system information about NTN cells. The UE receives, at block 1932, from the BS, via the system information or via an RRC message, the S thresholds for triggering the intra-frequency measurement on NTN cells (i.e., SIntraSearchP_NTNand SIntraSearchQ_NTN--in FIG. 12) and / or the S thresholds for triggering the inter-frequency measurement on NTN cells (i.e., SnonIntraSearchP_NTNand SnonIntraSearchQ_NTN--in FIG.12). At decision block 1941, the UE determines if any of the following conditions is fulfilled: Srxlev <= SIntraSearchP_NTN, Squal <= SIntraSearchQ_NTN, SrxlevSqualIf any of the above conditions is fulfilled, the flow proceeds to the block 1960, where the UE conducts the intra-frequency measurement or inter-frequency measurement (depending on which condition is fulfilled in block 1941). If one of the S thresholds forDocket No.14730662200PCT triggering the intra-frequency measurement is fulfilled, the UE conducts the intra- frequency measurement based on the SMTCs of the intra-frequency NTN cells. If one of the S thresholds for triggering the inter-frequency measurement is fulfilled, the UE conducts the inter-frequency measurement based on the SMTCs of the inter-frequency NTN cells.

[0123] Before proceeding to the block 1960, the UE may need adjust the SMTC for the NTN cell at block 1950, depending on whether the information obtained at block 220 contains the ephemeris information, the common TA parameters, the Kmacvalues, and the epoch time. At block 1950, the UE adjust the SMTCs for the intra-frequency NTN cells, based on the UE geographic position, the ephemeris information, the common TA parameters, the Kmacvalues, and the epoch time of the NTN cells. On the other hand, if the determination at the decision block 1941 is negative, the flow loops back to the decision block 1941.

[0124] FIG.20 is a flow diagram showing example operations 2000 of a UE to measure NTN cells based on TN coverage information. The flow diagram in FIG. 20 is similar to that in FIG. 2, with the differences discussed below. After receiving the system information about NTN cells (i.e., after block 220), the UE receives, at block 2038, from the BS, via the system information or via an RRC message, the TN coverage information containing a list of TN coverage areas, where each TN coverage area in the list includes a reference location and a distance threshold / coverage radius, and may include a TN area identity. At decision block 2047, where the UE determines if the UE is closed to the edge of the TN coverage (i.e., if the UE is not within the distance threshold / coverage radius of any TN coverage area). If the UE is close to the edge of the TN coverage, at block 2048, the UE triggers an NTN cell measurement. Otherwise, the flow loops back to the decision block 2047.

[0125] FIG.21 is a flow diagram showing example operations 2100 of a UE to measure NTN cells based on signal conditions of the serving and neighbor TN cells. The flow diagram in FIG. 21 is similar to that in FIG. 2, with the differences discussed below. At block 220, the UE receives the system information about NTN cells. At block 2116, the UE receives NTN-specific measurement thresholds as an NTN-specific triggering condition to determine whether to trigger the cell measurement on NTN cells / frequencies (i.e., Qthres_sand Qthres_n --in FIG. 14). The UE receives the system information in block 2116 from the TN BS, via the system information or an RRC message.Docket No.14730662200PCT

[0126] At decision block 2145, the UE determines if both of the following conditions are fulfilled: the RSRP (or the Rsas in TS 38.304) of serving cell <= Qthres_s, or the RSRP (or the Rnas in TS 38.304) of the strongest neighboring cell <= Qthres_n.

[0127] If both of the above conditions are fulfilled, the flow proceeds to the block 2146, where the UE triggers the cell measurements of NTN cells as part of a cell reselection evaluation. At block 2160, the UE conducts the intra / inter-frequency measurement based on the SMTCs of the intra / inter-frequency NTN cells. Before proceeding to the block 2160, the UE may adjust the SMTCs (block 250), depending on whether the information obtained at block 220 contains the ephemeris information, the common TA parameters, the Kmacvalues, and the epoch time. At block 250, the UE adjusts the SMTCs for the intra / inter-frequency NTN cells, based on the UE geographic position, the ephemeris information, the common TA parameters, the Kmacvalues, and the epoch time of the NTN cells. On the other hand, if the determination at the decision block 2145 is negative, the flow loops back to the decision block 2145.

[0128] FIG.22A is a flow diagram showing example operations of a UE to measure NTN cells based on whether the system information used to measure intra-frequency NTN cells is available. The flow diagram in FIG.22A is similar to that in FIG.2, with the differences discussed below. In FIG.22A, the UE determines whether to conduct the intra-frequency measurement on NTN cells based on whether the information about intra-frequency NTN cells is available. In some implementations, the reception of the information about NTN cells (block 220) may be omitted. Therefore, regardless of whether the UE has received the information for measuring NTN cells (block 220), the flow proceeds to block 2271A, where the UE receives cell reselection criteria for initiating an intra-frequency cell reselection. At decision block 2237A, the UE determines if either of the following conditions is fulfilled: SrxlevSqual

[0129] If neither of the above conditions is fulfilled, the flow loops back to the decision block 2237A. Otherwise, the flow proceeds to another decision block 2246A, where the UE determines if the information required to measure an intra-frequency NTN cell / frequency is available to the UE. If the determination at the decision block 2246A is negative (meaning the information is unavailable), the flow loops back to the decisionDocket No.14730662200PCT block 2237A. Otherwise, the flow proceeds to the block 2247A where the UE triggers an NTN cell measurement for intra-frequency cell reselection. In block 2260A, the UE conducts the intra-frequency measurement based on the SMTCs of the intra-frequency NTN cells. Before proceeding to the block 2260A, the UE may adjust the SMTC(s) for the infra-frequency cells at block 250, depending on whether the system information (block 220) contains the ephemeris information, the common TA parameters, the Kmacvalues, and the epoch time. At block 250, the UE adjust the SMTCs for the intra-frequency NTN cells, based on the UE geographic position, the ephemeris information, the common TA parameters, the Kmacvalues, and the epoch time of the NTN cells.

[0130] FIG.22B is a flow diagram showing example operations of a UE to measure NTN cells based on whether the system information used to measure inter-frequency NTN cells is available. The flow diagram in FIG.22B is similar to that in FIG. 22B, except that the blocks 2217B, 2237B, 2246B, 2247B, and 2260B refer to inter-frequency cell reselection. In block 2271B, the UE receives cell reselection criteria for initiating an inter-frequency cell reselection. At decision block 2237B, the UE determines if either of the following conditions is fulfilled: Srxlev <= SnonIntraSearchP, or Squal

[0131] If neither of the above conditions is fulfilled, the flow loops back to the decision block 2237B. Otherwise, the flow proceeds to another decision block 2246B, where the UE determines if the information required to measure an inter-frequency NTN cell / frequency is available to the UE. If the determination at the decision block 2246B is negative, the flow loops back to the decision block 2237B again. Otherwise, the flow proceeds to the block 2247B, where the UE triggers a cell measurement of the NTN cell for inter-frequency cell reselection. At block 2260B, the UE conducts the inter-frequency measurement based on the SMTCs of the inter-frequency NTN cells.

[0132] FIG. 23 is a block diagram of example distributed or disaggregated implementation of an example base station 2306 (such as TN BS 106) using a centralized unit (CU) and a distributed unit (DU). In this implementation, the BS 2306 includes a CU 2306A and one or more distributed units (DUs) 2306B. The CU 2306A includes processing hardware, such as one or more general-purpose processors (e.g., CPUs) and a computer- readable memory storing machine-readable instructions executable on the general-purpose processor(s), and / or special-purpose processing units. For example, the CU 2306A canDocket No.14730662200PCT include a PDCP controller, an RRC controller and / or a RRC inactive controller. In some implementations, the CU 2306A can include a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures. In further implementations, the CU 2306A does not include an RLC controller.

[0133] Each of the DUs 2306B also includes processing hardware that can include one or more general-purpose processors (e.g., CPUs) and computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. For example, the processing hardware can include a MAC controller configured to manage or control one or more MAC operations or procedures (e.g., a random access procedure), and / or an RLC controller configured to manage or control one or more RLC operations or procedures. The process hardware can also include a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0134] In some embodiments, a RAN (such as RAN 101 of FIG. 1) supports Integrated Access and Backhaul (IAB) functionality. In some implementations, the DU 2306B operates as an IAB-node, and the CU 2306A operates as an IAB-donor. In some embodiments, the RAN 101 supports Non-Terrestrial Network (NTN) functionality.

[0135] In some implementations, the CU 2306A can include a logical node CU control plane (CU-CP 2307A) that hosts the control plane part of the PDCP protocol of the CU 2306A. The CU 2306A can also include logical node(s) referred to as a CU user plane (CU-UP 2307B) that hosts the user plane part of the PDCP protocol and / or Service Data Adaptation Protocol (SDAP) protocol of the CU 2306A. The CU-CP 2307A can transmit control information (e.g., RRC messages, F1 application protocol messages), and the CU- UP 2307B can transmit the data packets (e.g., SDAP PDUs or Internet Protocol packets).

[0136] The CU-CP 2307A can be connected to multiple CU-UP 2307B through the E1 interface. The CU-CP 2307A selects the appropriate CU-UP 2307B for the requested services for the UE 102. In some implementations, a single CU-UP 2307B can connect to multiple CU-CP 2307A through the E1 interface. The CU-CP 2307A can connect to one or more DU(s) 2306B through an F1-C interface. The CU-UP 2307B can connect to one or more DU(s) 2306B through the F1-U interface under the control of the same CU-CP 2307A. In some implementations, one DU 2306B can connect to multiple CU-UP 2307B under the control of the same CU-CP 2307A. In such implementations, the connectivityDocket No.14730662200PCT between a CU-UP 2307B and a DU 2306B is established by the CU-CP 2307A using Bearer Context Management functions.

[0137] The CU-CP(s) 2307A generates the carrier frequency configurations (such as frequency and timing information) in the system information messages (such as SIB2 or SIB4) and provides the system information messages to the DU(s) 2306B. The DU(s) 2306B passes these SIBs to lower layers (such as a physical layer (PHY), baseband unit (BBU) or remote radio head (RRH)) for a broadcast transmission. Similarly, the CU-CP(s) 2307A generates the NTN neighbor cell configuration (in SIB19) and, in some instances, the configuration of NTN-specific triggering conditions and provides that information to the DU(s) 2306B for transmission.

[0138] FIG. 24A is a block diagram of an example protocol stack 2400A according to which a UE (such as UE 102) communicates with a base station (such as TN BS 106). In the example protocol stack 2400A, a physical layer (PHY) 2404A of EUTRA provides transport channels to the EUTRA MAC sublayer 2404B, which in turn provides logical channels to the EUTRA RLC sublayer 2404C. The EUTRA RLC sublayer 2404C in turn provides RLC channels to an EUTRA PDCP sublayer 2405 and, in some cases, to an NR PDCP sublayer 2407A. Similarly, the NR PHY 2403A provides transport channels to the NR MAC sublayer 2403B, which in turn provides logical channels to the NR RLC sublayer 2403C. The NR RLC sublayer 2403C in turn provides data transfer services to the NR PDCP sublayer 2407A. The NR PDCP sublayer 2407A0 in turn can provide data transfer services to Service Data Adaptation Protocol (SDAP) 2499 or a radio resource control (RRC) sublayer (not shown in FIG.24A). The UE 102, in some implementations, supports both the EUTRA and the NR stack as shown in FIG. 24A, to support handover between EUTRA and NR base stations and / or to support DC over EUTRA and NR interfaces. Further, as illustrated in FIG.24A, the UE 102 can support layering of NR PDCP sublayer 2407A over EUTRA RLC sublayer 2404C, and SDAP sublayer 2499 over the NR PDCP sublayer 2407A.

[0139] The EUTRA PDCP sublayer 2405 and the NR PDCP sublayer 2407A receive packets (e.g., from an Internet Protocol (IP) layer, layered directly or indirectly over the PDCP layer 2405 or 2407A) that can be referred to as service data units (SDUs), and output packets (e.g., to the RLC layer 2404C or 2403C) that can be referred to as protocol data units (PDUs). Except where the difference between SDUs and PDUs is relevant, this disclosure for simplicity refers to both SDUs and PDUs as “packets.”Docket No.14730662200PCT

[0140] On a control plane, the EUTRA PDCP sublayer 2405 and the NR PDCP sublayer 2407A can provide signaling radio bearers (SRBs) or RRC sublayer (not shown in FIG. 24A) to exchange RRC messages or non-access-stratum (NAS) messages, for example. On a user plane, the EUTRA PDCP sublayer 2405 and the NR PDCP sublayer 2407A can provide Data Radio Bearers (DRBs) to support data exchange. Data exchanged on the NR PDCP sublayer 2407A can be SDAP PDUs, Internet Protocol (IP) packets or Ethernet packets.

[0141] FIG. 24B is a block diagram of an example protocol stack 2400B according to which the UE (e.g., UE 102) communicates with a CU (e.g., CU 2306A) and a DU (e.g., DU(s) 2306B). The radio example protocol stack 2400A is functionally split as shown by the example protocol stack 2400B in FIG.24B. The CU at any of the BS 106 can hold all the control and upper layer functionalities (e.g., RRC 2407C, SDAP sublayer 2499, NR PDCP NR PDCP sublayer 2407A), while the lower layer operations (e.g., NR RLC NR RLC sublayer 2403C, NR MAC NR MAC sublayer 2403B, and NR PHY 2403A) are delegated to the DU. To support connection to a 5GC, NR PDCP NR PDCP sublayer 2407A provides SRBs to RRC 2407C, and NR PDCP NR PDCP sublayer 2407A provides DRBs to SDAP sublayer 2499 and SRBs to RRC 2407C.

[0142] The RRC layer 2407C generates the system information messages (such as any of the system information messages described in this disclosure) and provides the system information messages to the MAC 2403B, which coordinates with the PHY 2403A to broadcast the system information messages via a broadcast channel (BCCH).

[0143] FIG. 25A illustrates an example user plane protocol stack 2600A in accordance with aspects of this disclosure. FIG. 25A includes a visual representation of the NTN portion of user plane protocol stack 2600A involving the UE 102, the satellite 108, the NTN gateway 198, the NTN BS 109, and the 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 108 and the NTN gateway 198, being placed in the middle of the NR-Uu interface.

[0144] FIG. 25B illustrates an example control plane protocol stack in accordance with aspects of this disclosure. As with FIG.25A, the NTN control plane protocol stack 2600B illustrated in FIG.25B is also similar to that of a TN, with the addition of the satellite 108 and the NTN gateway 198 being placed in the NR-Uu interface.Docket No.14730662200PCT

[0145] FIG. 26 is a block diagram of an example wireless communication system 2500 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 2500 includes the same elements as described with reference to FIG. 1, including the UE 102, the TN BS 106, the NTN BS 109, the satellite 108, and the core network 199. The UE 102 can support at least a 5G NR (or simply, “NR”) or E-UTRA air interface to communicate with the TN BS 106. The TN BS 106 connects to the core network 199 via an interface (e.g., S1 or NG interface). The TN BS 106 can connect to other base stations (including the NTN BS 109) via an interface (e.g., X2 or Xn interface) for interconnecting NG RAN nodes.

[0146] The core network 199 can be an Evolved Packet Core (EPC) and / or a 5G core (5GC). Among other components, the EPC can include a Serving Gateway (SGW), a Mobility Management Entity (MME), and a Packet Data Network Gateway (PGW). The SGW in general is configured to transfer user-plane packets related to audio calls, video calls, Internet traffic, etc., and the MME is configured to manage authentication, registration, paging, and other related functions. The PGW provides connectivity from the UE to one or more external packet data networks, e.g., an Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network. The 5GC includes a User Plane Function (UPF) and an Access and Mobility Management Function (AMF), and / or Session Management Function (SMF). Generally speaking, the UPF is configured to transfer user-plane packets related to audio calls, video calls, Internet traffic, etc., the AMF is configured to manage authentication, registration, paging, and other related functions, and the SMF is configured to manage PDU sessions.

[0147] The base station 106 is equipped with processing hardware 2506 that can include a receiver 2507B configured to receive data in the uplink direction. The processing hardware 2506 can also include a transmitter 2507A configured to transmit data in the downlink direction. The processing hardware further can one or more general-purpose processor(s) 2507C (e.g., CPUs) and a non-transitory computer-readable memory 2507D storing instructions that the one or more general-purpose processors execute. Additionally, or alternatively, the processing hardware 2506 can include special-purpose processing units. The processor 2507C may include, for example, one or more central processing units, graphics processing units (GPUs), or other application-specificDocket No.14730662200PCT integrated circuits (ASIC), and the like. CRM 2507D 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 TN BS 106.

[0148] The satellite 108 can include processing hardware 2508, such as a transmitter 2509A, a receiver 2509B, a processor 2509C, and CRM 2509D (similar to components 2506, 2507A, 2507B, 2507C and 2507D of the TN BS 106). The NTN BS 109 can include generally similar components (not shown) as the processing hardware 2506.

[0149] The UE 102 is equipped with processing hardware 2502 that can include one or more general-purpose processors such as CPUs and non-transitory computer-readable memory 2503D storing machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. The processing hardware 2502 can also include a transmitter 2503A configured to transmit data in the downlink direction. The processing hardware further can include a receiver 2503B configured to receive data in the uplink direction. The processing hardware 2502 in an example implementation includes a processor 2503C 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) 2503C 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) 2503C 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) 2503D 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), Flash memory, solid-state drive (SSD) or other mass-storage 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) 2503C and other components of the processing hardware 2502 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) 2503C to enable user-plane communication, control-plane signaling, and user interaction with the UE 102.Docket No.14730662200PCT

[0150] FIG. 1 through FIG. 26 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.

[0151] 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. Alternatively, or in addition to the other examples described herein, examples include any combination of the following implementation options (enumerated as clauses for clarity).

[0152] Clause 1. A method for wireless communication by a user equipment (UE) (102), including: camping (202) on a terrestrial network (TN) cell (184) of a TN base station (BS) (106); receiving (120, 220), from the TN BS (106), system information about a non- terrestrial network (NTN) cell (196) of a satellite (108); and triggering (140, 240), as part of a cell reselection evaluation, an cell measurement of a synchronization signal of the NTN cell (196) based, at least in part, on the system information about the NTN cell (196) and an NTN-specific triggering condition being satisfied.

[0153] Clause 2. The method of clause 1, further including: receiving (130, 230) a configuration of the NTN-specific triggering condition from the TN BS via a system information broadcast (SIB) or radio resource control (RRC) message.

[0154] Clause 3. The method of clause 1 or 2, receiving (130, 230, 632, 1232, 1932) a configuration of the NTN-specific triggering condition from the TN BS, the configuration including at least one of: a reference signal received power (RSRP) threshold for triggering the intra-frequency NTN measurement (SIntraSearchP_NTN), a reference signal received quality (RSRQ) threshold for triggering the intra-frequency NTN measurement (SIntraSearchQ_NTN), an RSRP threshold for triggering the inter-frequency NTN measurement (SnonIntraSearchP_NTN), or an RSRQ threshold for triggering the inter-frequency NTN measurement (SnonIntraSearchQ_NTN); and triggering (140, 240, 1242, 1942) the cellDocket No.14730662200PCT measurement based on at least one of: a received signal strength (Srxlev) of the TN cell being below the SIntraSearchP_NTNor the (SnonIntraSearchP_NTN, or a received signal quality (Squal) of the TN cell being below the SIntraSearchQ_NTNor the SnonIntraSearchQ_NTN.

[0155] Clause 4. The method of any one of clauses 1 to 3, further including: receiving (130, 230, 638, 1338, 2038) a configuration of the NTN-specific triggering condition from the TN BS, the configuration including TN coverage information indicating a boundary of a TN coverage area; determining a position of the UE (102) relative to the boundary; and triggering (140, 240, 1348, 2048) the cell measurement based on the position of the UE being within a threshold distance of the boundary.

[0156] Clause 5. The method of any one of clauses 1 to 4, further including: performing a first instance of the cell reselection evaluation based on cell measurements of Synchronization Signal (SS) and Physical Broadcast Channel (PBCH) Block (SSBs) of cells using SSB Measurement Timing Configurations (SMTCs) for the SSBs without regard to which SMTCs are linked to NTN cells; considering the NTN-specific triggering condition satisfied when no measured cell satisfies a cell reselection criteria for the cell reselection evaluation; and triggering, for a second instance of the cell reselection evaluation, the cell measurement of an SSB of the NTN cell (196) using at least one SMTC that is adjusted to account for a propagation delay for the NTN cell.

[0157] Clause 6. The method of any one of clauses 1 to 5, further including: receiving (1416, 2116), from the TN BS, one or more reference signal received power (RSRP) thresholds for the cell reselection evaluation, where the one or more RSRP thresholds include an RSRP threshold for the current serving cell (Qthres_s) and an RSRP threshold for the strongest neighbor cell (Qthres_n); and considering the NTN-specific triggering condition satisfied and triggering (1446, 2146) the cell measurement based on both a first RSRP measurement of a current serving cell (Qmeas,s) being below the Qthres_s, and a second RSRP measurement of a strongest measured neighbor cell (Qmeas,n) being below the Qthres_n.

[0158] Clause 7. The method of any one of clauses 1 to 6, further including: receiving (1517, 2217A, 2217B), from the TN BS, cell reselection criteria for initiating an intra- frequency or inter-frequency cell reselection; initiating the cell reselection evaluation based on the cell reselection criteria; considering the NTN-specific triggering condition satisfied based on the initiating the cell reselection evaluation and the receiving the systemDocket No.14730662200PCT information about the NTN cell; and triggering (1547, 2247A, 2247B) the cell measurement for intra-frequency or inter-frequency cell reselection.

[0159] Clause 8. The method of any one of clauses 1 to 7, where the synchronization signal of the NTN cell includes a Synchronization Signal (SS) and Physical Broadcast Channel (PBCH) Block (SSB), the method further including: determining an SSB Measurement Timing Configuration (SMTC) for the NTN cell (196) based, at least in part, on the system information; obtaining (260) the cell measurement of the SSB from the NTN cell (196) based on the SMTC; and performing (270) a cell reselection evaluation based on the cell measurement.

[0160] Clause 9. The method of any one of clauses 1 to 7, where the synchronization signal of the NTN cell includes a Synchronization Signal (SS) and Physical Broadcast Channel (PBCH) Block (SSB), the method further including: receiving, from the TN BS, a first system information message indicating at least one carrier frequency and at least a first SSB Measurement Timing Configuration (SMTC) associated with the at least one carrier frequency; receiving, from the TN BS, a second system information message including the system information about the NTN cell (196) in an NTN neighbor cell configuration information element (IE); and obtaining linkage information from the first system information message or a third system information message, where the linkage information is associated with the first SMTC and includes at least one of a Physical Cell Identity (PCI), a carrier frequency, or an NTN cell index value; and determining (952, 1652) that the first SMTC is associated with the NTN cell (196) based on the linkage information matching a corresponding PCI, carrier frequency or NTN cell index in the NTN neighbor cell configuration IE.

[0161] Clause 10. The method of clause 9, further including: adjusting (250, 954, 1154, 1950) the first SMTC for the NTN cell (196) based on an adjusted SMTC or timing offset for the NTN cell (196) in the NTN neighbor cell configuration IE or based on a propagation delay calculated for the satellite operating the NTN cell.

[0162] Clause 11. The method of clause 9 or 10, where the NTN neighbor cell configuration IE includes measurement timing information, ephemeris information, an epoch time, tracking area (TA) parameters, and a Kmacvalue indicating a scheduling offset for downlink and uplink frame timing, the method further including: adjusting (954) a timing offset of the first SMTC based on the UE geographic position in relation to theDocket No.14730662200PCT ephemeris information, the epoch time, the TA parameters, the Kmacvalue, or any combination thereof.

[0163] Clause 12. The method of any one of clauses 1 to 11, further including: performing (270) the cell reselection evaluation using the cell measurement; and camping (875) on the NTN cell based on a result of the cell reselection evaluation.

[0164] Clause 13. The method of any one of clauses 1 to 12, further including: refraining from the triggering of the cell measurement until the NTN-specific triggering condition is satisfied.

[0165] Clause 14. A method for wireless communication by a BS operating a TN cell, including: transmitting system information about an NTN cell of a satellite to enable a UE to obtain an cell measurement of the NTN cell as part of a cell reselection evaluation; and transmitting a configuration of an NTN-specific triggering condition to cause the UE to trigger the cell measurement based on the NTN-specific triggering condition being satisfied.

[0166] Clause 15. The method of clause 14, where the configuration includes at least one of: one or more NTN-specific thresholds for triggering the cell measurement that are different from, or in addition to, a cell reselection criteria for the cell reselection evaluation; or TN coverage information indicating a boundary of a TN coverage area.

[0167] Clause 16. The method of clause 15, where the one or more thresholds for triggering the cell measurement include at least one of: a reference signal received power (RSRP) threshold for triggering the intra-frequency NTN measurement (SIntraSearchP_NTN), a reference signal received quality (RSRQ) threshold for triggering the intra-frequency NTN measurement (SIntraSearchQ_NTN), a RSRP threshold for triggering the inter-frequency NTN measurement (SnonIntraSearchP_NTN), or a RSRQ threshold for triggering the inter- frequency NTN measurement (SnonIntraSearchQ_NTN).

[0168] Clause 17. The method of any one of clauses 14 to 16, where the configuration includes: one or more reference signal received power (RSRP) thresholds for the cell reselection evaluation, where the one or more RSRP thresholds include an RSRP threshold for the current serving cell (Qthres_s) and an RSRP threshold for the strongest measured neighbor cell (Qthres_n), where the NTN-specific triggering condition is satisfied when no cell satisfies a cell reselection criteria in a first instance of the cell reselection evaluation and RSRP measurements of cells measured in the first instance are below the one or more RSRP thresholds.Docket No.14730662200PCT

[0169] Clause 18. An apparatus, including: a communication unit; and a processing system configured to control the communication unit to implement any of clauses 1 to 17.

[0170] The following description may be applied to the description above. 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.”

[0171] 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 (IoT) 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 (IoT) 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.Docket No.14730662200PCT

[0172] Certain embodiments 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 and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0173] 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.

[0174] 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.”

[0175] As used herein, a phrase referring to “at least one of” or “one or more of” a list of items refers to any combination of those items, including single members. For example, “at least one of: 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.

[0176] 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.”Docket No.14730662200PCT

[0177] 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.

[0178] 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.

[0179] 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 this specification 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.

[0180] 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.

[0181] 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 scopeDocket No.14730662200PCT 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.

[0182] 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 a claimed 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.

[0183] 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.

[0184] 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.

Claims

Docket No.14730662200PCT CLAIMS What is claimed is:

1. A method for wireless communication by a user equipment (UE) (102), comprising: camping (202) on a terrestrial network (TN) cell (184) of a TN base station (BS) (106); receiving (120, 220), from the TN BS (106), non-terrestrial network (NTN)- specific system information about an NTN cell (196) of a satellite (108), wherein the NTN- specific system information includes one or more NTN neighbor cell configuration information elements and NTN assistance information; triggering (140, 240), as part of a cell reselection evaluation, a cell measurement of a synchronization signal of the NTN cell based, at least in part, on the NTN-specific system information, wherein the synchronization signal includes a Synchronization Signal (SS) and Physical Broadcast Channel (PBCH) Block (SSB); and obtaining (260) the cell measurement based on an SSB Measurement Timing Configuration (SMTC) for the SSB, wherein the SMTC is based, at least in part, on the one or more NTN neighbor cell configuration information elements and the NTN assistance information.

2. The method of claim 1, further comprising: adjusting (250, 954, 1154, 1950) the SMTC based on at least one of: a network-adjusted SMTC in the system information, a timing offset for the NTN cell (196) in the NTN assistance information, a UE geographic position relative to ephemeris information in the NTN assistance information; or a propagation delay calculated for the satellite operating the NTN cell.

3. The method of claim 1 or 2, further comprising: matching the one or more NTN neighbor cell configuration information elements and the NTN assistance information to the NTN cell based on linkage information; and adjusting, by the UE, the SMTC of the NTN cell based on an NTN neighbor cell configuration in the one or more NTN neighbor cell configuration information elements and one or more parameters in the NTN assistance information.Docket No.14730662200PCT 4. The method of any one of claims 1 to 3, further comprising: determining a UE geographic position of the UE; and adjusting (954) a timing offset of the SMTC based on the UE geographic position and the NTN assistance information, wherein the NTN assistance information includes at least one of measurement timing information, ephemeris information, an epoch time, tracking area (TA) parameters, a Kmacvalue indicating a scheduling offset for downlink and uplink frame timing, or any combination thereof.

5. The method of any one of claims 1 to 4, further comprising: receiving (130, 230, 632, 1232, 1932), from the TN BS, a configuration of an NTN- specific triggering condition based on a signal metric of the TN cell or a boundary of a TN coverage area of the TN cell; triggering (140, 240), as part of the cell reselection evaluation, the cell measurement of the synchronization signal of the NTN cell when the NTN-specific triggering condition is satisfied; and refraining from the triggering of the cell measurement when the NTN-specific triggering condition is not satisfied.

6. The method of claim 5, wherein the NTN-specific triggering condition includes one or more NTN-specific thresholds for triggering the cell measurement that are different from, or in addition to, a cell reselection criteria for the cell reselection evaluation.

7. The method of claim 5 or 6, wherein the NTN-specific triggering condition is based on at least one of: a reference signal received power (RSRP) threshold for triggering the intra- frequency NTN measurement (SIntraSearchP_NTN), a reference signal received quality (RSRQ) threshold for triggering the intra-frequency NTN measurement (SIntraSearchQ_NTN), an RSRP threshold for triggering the inter-frequency NTN measurement (SnonIntraSearchP_NTN), or an RSRQ threshold for triggering the inter-frequency NTN measurementtriggering (140, 240, 1242, 1942) the cell measurement based on at least one of:Docket No.14730662200PCT a received signal strength (Srxlev) of the TN cell being below the SIntraSearchP_NTNor the (SnonIntraSearchP_NTN, or a received signal quality (Squal) of the TN cell being below the SIntraSearchQ_NTNor the SnonIntraSearchQ_NTN.

8. The method of any one of claims 5 to 7, further comprising: performing a first instance of the cell reselection evaluation based on cell measurements of one or more SSBs of cells using SMTCs for the SSBs without regard to which SMTCs are linked to NTN cells; considering the NTN-specific triggering condition satisfied when no measured cell satisfies a cell reselection criteria for the cell reselection evaluation; and performing a second instance of the cell reselection evaluation based on cell measurements of one or more SSBs of NTN cells using SMTCs that are adjusted for the NTN cells.

9. The method of any one of claims 1 to 8, further comprising: receiving (1416, 2116), from the TN BS, one or more reference signal received power (RSRP) thresholds for the cell reselection evaluation, wherein the one or more RSRP thresholds include an RSRP threshold for the current serving cell (Qthres_s) and an RSRP threshold for the strongest neighbor cell (Qthres_n); and triggering (1446, 2146) the cell measurement of the synchronization signal of the NTN cell based on both a first RSRP measurement of a current serving cell (Qmeas,s) being below the Qthres_s, and a second RSRP measurement of a strongest measured neighbor cell (Qmeas,n) being below the Qthres_n.

10. The method of any one of claims 1 to 9, further comprising: receiving the NTN-specific system information via a system information broadcast (SIB) type 19 (SIB19) or radio resource control (RRC) message.Docket No.14730662200PCT 11. The method of any one of claims 1 to 10, further comprising: receiving, from the TN BS, a first system information message indicating at least one carrier frequency and at least a first SSB Measurement Timing Configuration (SMTC) associated with the at least one carrier frequency; receiving, from the TN BS, a second system information message including NTN- specific system information in an NTN neighbor cell configuration information element (IE); obtaining linkage information from the first system information message or a third system information message, wherein the linkage information is associated with the first SMTC and includes at least one of a Physical Cell Identity (PCI), a carrier frequency, or an NTN cell index value; and determining (952, 1652) that the first SMTC is associated with the NTN cell (196) based on the linkage information matching a corresponding PCI, carrier frequency, or NTN cell index in the NTN neighbor cell configuration IE.

12. A method for wireless communication by a base station (BS) operating a terrestrial network (TN) cell, comprising: transmitting non-terrestrial network (NTN)-specific system information about an NTN cell (196) of a satellite (108), wherein the NTN-specific system information includes one or more NTN neighbor cell configuration information elements and NTN assistance information to enable a user equipment (UE) to obtain a cell measurement of the NTN cell as part of a cell reselection evaluation; and transmitting a configuration of an NTN-specific triggering condition to cause the UE to trigger the cell measurement based on the NTN-specific triggering condition being satisfied.

13. The method of claim 12, wherein the NTN-specific triggering condition includes at least one of: a reference signal received power (RSRP) threshold for triggering the intra- frequency NTN measurement (SIntraSearchP_NTN), a reference signal received quality (RSRQ) threshold for triggering the intra-frequency NTN measurement (SIntraSearchQ_NTN), a RSRP threshold for triggering the inter-frequency NTN measurement (SnonIntraSearchP_NTN),Docket No.14730662200PCT a RSRQ threshold for triggering the inter-frequency NTN measurement (SnonIntraSearchQ_NTN), or one or more RSRP thresholds for the cell reselection evaluation, wherein the one or more RSRP thresholds include an RSRP threshold for the current serving cell (Qthres_s) and an RSRP threshold for the strongest measured neighbor cell (Qthres_n), wherein the NTN-specific triggering condition is satisfied when no cell satisfies a cell reselection criteria in a first instance of the cell reselection evaluation and RSRP measurements of cells measured in the first instance are below the one or more RSRP thresholds.

14. The method of claim 12 or 13, wherein the NTN assistance information includes at least one of a network-adjusted SMTC, measurement timing information including a timing offset for the NTN cell, ephemeris information, an epoch time, tracking area (TA) parameters, a Kmacvalue indicating a scheduling offset for downlink and uplink frame timing, a propagation delay calculated for the satellite operating the NTN cell, or any combination thereof.

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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