Energy efficient frequency measurement in NTN cells

Abstract

To perform inter-frequency measurements, a UE in an NTN cell receives one or more pairs of (i) a TN frequency and (ii) a bitmap indication that identifies one or more of a plurality of segments of the NTN cell associated with the TN frequency. The UE searches for a TN cell on the TN frequency only when the current location of the UE is within the one or more of the plurality of segments according to the bitmap indication.

Description

[0001] This document relates generally to wireless communications and, more particularly, to energy and / or bandwidth saving techniques that may be used by a user equipment (UE) operating in an idle or inactive state in a non-terrestrial (NTN) cell when performing inter-frequency measurements. Background Art

[0002] This Background section is provided for the purpose of generally presenting the context for the technology described in the following sections. No admission is made, either expressly or by implication, that the work of the presently named inventors, to the extent that it is described in this Background section, and any aspects of the specification that otherwise may not have been admitted as prior art at the time of filing, are prior art.

[0003] The goals behind developing fifth-generation (5G) technology include providing a unified framework for communication types such as enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC).

[0004] 5G technology primarily relies on legacy terrestrial networks. However, the Third Generation Partnership Project (3GPP) organization has proposed extending 5G communications to non-terrestrial networks (NTNs) using 5G New Radio (NR) technology or Long Term Evolution (LTE) technology tailored for narrowband Internet of Things (NB-IoT) or enhanced machine-type communications (eMTC) scenarios. In an NTN, RF transceivers are mounted on satellites, unmanned aerial systems (UAS) (also known as drones, balloons, airplanes), or another suitable device. For simplicity, the following discussion will refer to all such equipment as satellites. In addition to satellites, an NTN may include one or more satellite gateways (referred to as "sat gateways" or "NTN gateways") that connect the NTN to a public data network, feeder links between the sat gateways and satellites, service links between satellites, and inter-satellite links (ISLs) when satellites form a constellation.

[0005] Satellites can be classified into one of several types based on altitude, orbit, and beam footprint size. These types include low earth orbit (LEO) satellites, medium earth orbit (MEO) satellites, geostationary earth orbit (GEO) satellites, UAS platforms (including high altitude platform stations (HAPS)), and highly elliptical orbit (HEO) satellites. GEO satellites are also known as geosynchronous orbit (GSO) satellites, and LEO / MEO satellites are also known as non-GSO (NGSO) satellites.

[0006] GSO satellites communicate with one or several sat-gateways deployed over the satellite's target coverage area (e.g., a region or even a continent). Non-GSO satellites temporarily communicate with one or several serving sat-gateways. NTN is designed to ensure service and feeder link continuity between consecutive serving sat-gateways, while having sufficient overlap time to continue mobility anchoring and handover.

[0007] Satellites can generate several beams for a given service area, defined by a field of view. The beam's coverage area depends on the onboard antenna configuration and elevation angle and is typically elliptical. Satellites can support either transparent or regenerative (with onboard processing) payload options. For transparent payloads, the satellite can apply RF filtering, frequency conversion, and amplification without altering the waveform signal. For regenerative payloads, the satellite can apply RF filtering, frequency conversion, amplification, demodulation and decoding, routing, and coding / modulation. This regenerative approach effectively implements most of the functionality of a base station (e.g., a gNB in ​​a 5G system).

[0008] NB-IoT and eMTC technologies are expected to be particularly suitable for IoT devices operating in remote areas with limited or no terrestrial connectivity. Such IoT devices can be used in a variety of industries, including, for example, transportation (maritime, road, rail, aviation) and logistics; solar energy, oil and gas extraction; utilities; agriculture; environmental monitoring; and mining. However, to ensure the required IoT connectivity, the deployment of these technologies requires satellite connectivity to provide coverage beyond terrestrial deployments. Satellite NB-IoT or eMTC is defined in a complementary manner to terrestrial deployments.

[0009] The UE may receive better service in a TN cell than in an NTN cell. When camped in an NTN cell, the UE measures the signals in the TN cell to determine whether cell reselection is available. More specifically, the UE camped on the cell operates in an idle or inactive state associated with the radio resource control (RRC) sublayer of the radio protocol stack and monitors only the control information in the cell. The UE has no active radio connection with the base station in the idle state (RRC_IDLE), and the radio connection in the inactive state (RRC_INACTIVE) is at least temporarily suspended. Since the idle or inactive UE has no active radio connection with the base station, the UE relies on the control information in the NTN cell to determine the frequency of the TN cell that the UE can consider for cell reselection.

[0010] Therefore, the base station associated with the NTN cell transmits a system information block (SIB), which includes a list of cell identifiers and carrier information for the corresponding TN cell. However, an NTN cell typically covers a larger geographical area than any single TN cell. Therefore, a UE may retrieve information from the SIB related to cells that the UE cannot detect at its current geographical location. Specifically, the UE may attempt measurements at frequencies included in the SIB but fail to detect the corresponding signal due to the distance to the terrestrial base station. As a result, the UE unnecessarily consumes power.

[0011] The base station may include detailed geographic information for TN cells in the SIB. Using the detailed geographic information for a particular TN cell, the UE can determine whether it is close enough to the corresponding terrestrial base station to attempt a measurement. However, this approach requires significant signaling overhead because the non-terrestrial base station must send a large amount of additional information in the system information block. Summary of the Invention

[0012] A UE method for performing inter-frequency measurements according to an embodiment overcomes the problems described in the background section. The UE method (i.e., performed by a UE) includes: receiving, in an NTN cell, (i) a TN frequency and (ii) an indication of one or more of a plurality of sectors of the NTN cell associated with the TN frequency; and searching for a TN cell on the TN frequency only when the UE's current location is within the one or more of the plurality of sectors.

[0013] According to another embodiment, a method for configuring inter-frequency measurements at a UE operating in an NTN cell, performed by a base station associated with an NTN cell, includes: sending a TN frequency in the NTN cell; and indicating in the NTN cell which one or more of a plurality of segments of the NTN cell the TN frequency is associated with, to facilitate searching for TN cells on the TN frequency at the UE.

[0014] Another example embodiment of these techniques is another UE method for performing inter-frequency measurements. The method, performed by the UE, includes: receiving a frequency in an NTN cell, on which the UE is to search for cells; searching for a TN cell on the frequency for a first time period; and, in response to detecting the TN cell on the frequency, measuring a signal in the TN cell for a second time period.

[0015] Yet another example embodiment of the techniques is an apparatus comprising a transceiver and a processing component configured to implement any of the methods described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a block diagram of an example wireless communication system in which a user device of the present disclosure may implement the inter-frequency measurement technique;

[0017] Figure 2 is a block diagram of the example protocol stack, Figure 1 The UE communicates with the base station according to the example protocol stack;

[0018] Figure 3A is a block diagram of an example NTN node with a transparent payload implementation;

[0019] Figure 3B is a block diagram of an example NTN implementation in which a base station is connected to multiple satellites via the same sat gateway;

[0020] Figure 4A Shown with Figure 3A A sample user plane protocol library for use with the architecture;

[0021] Figure 4B Shown with Figure 3A A sample control plane protocol library for use with the architecture;

[0022] Figure 5 is a diagram showing how the network may configure a UE to search for a TN cell on a TN frequency when the UE is in idle or inactive state and camped on an NTN cell;

[0023] Figure 6A is a diagram showing how a base station may be in an NTN cell and uses a bitmap to indicate coarse TN cell coverage;

[0024] Figure 6B Shown with Figure 6A A similar scenario, where the NTN cell is logically divided into a larger number of segments;

[0025] Figure 7 is a messaging diagram for an example scenario in which a UE performs search and measurement on TN frequencies in response to determining proximity to a TN cell using a bitmap in an NTN cell;

[0026] Figure 8 is a messaging diagram for an example scenario in which a UE abandons search and measurement on TN frequencies in response to determining, in an NTN cell, using a bitmap, that it is not close to a TN cell;

[0027] Figure 9 Shown with Figure 7 Similar scenario, but here the UE also modifies the time period used for searching on the TN frequency;

[0028] Figure 10 Shown with Figure 7 Similar scenario, but here the UE also obtains detailed coverage information of the TN cell using the RRC recovery procedure;

[0029] Figure 11 Shown with Figure 7 Similar scenario, but here the UE also obtains detailed coverage information of the TN cell using message exchanges over the active radio connection;

[0030] Figure 12 Shown with Figure 7 Similar scenario, but here the UE also obtains detailed coverage information of the TN cell using the on-demand SI acquisition procedure;

[0031] Figure 13 is a flow chart of an example method in a UE for determining whether to use a TN carrier frequency based on coarse TN coverage information in an NTN cell;

[0032] Figure 14 is a flow chart of an example method in a UE for determining whether to use a TN carrier frequency based on coarse TN coverage information in an NTN cell and applying modified measurement requirements;

[0033] Figure 15 Shown with Figure 14 A similar approach, but where the UE uses the RRC recovery procedure to request detailed coverage information for a sector of the NTN cell;

[0034] Figure 16 Shown with Figure 14 A similar approach, but where the UE requests detailed coverage information for a sector of an NTN cell using messaging over an active radio connection;

[0035] Figure 17 Shown with Figure 14 A similar approach, but where the UE uses the on-demand SI acquisition procedure to request detailed coverage information for a sector of the NTN cell;

[0036] Figure 18 is a flow chart of an example method implemented in a base station for determining coarse TN coverage information and broadcasting the coarse TN coverage in a system information block;

[0037] Figure 19 is a flow chart of an example method implemented in a base station for delivering detailed TN coverage information to a UE using an RRC recovery procedure;

[0038] Figure 20 is a flow chart of an example method implemented by a base station for delivering detailed TN coverage information to a UE in a DL DCCH message;

[0039] Figure 21 is a flow chart of an example method implemented by a base station for delivering detailed TN coverage information to a UE in an on-demand system information transmission;

[0040] Figure 22 is a flow chart of an example method implemented in a UE for determining a periodicity with which the UE is to search for a TN cell on a TN frequency or perform measurements on a TN cell;

[0041] Figure 23 is a flow chart of an example method implemented in a UE for determining a periodicity with which the UE is to search for cells on a frequency based on whether the frequency is a TN frequency or an NTN frequency;

[0042] Figure 24 is a flow chart of an example method implemented in a UE for determining whether the UE should search for TN cells based on TN cell location information; and

[0043] Figure 25 is a flow chart of an example method implemented in a UE for determining whether the UE should search for cells on a TN frequency based on location information associated with the TN frequency. DETAILED DESCRIPTION

[0044] To reduce the overhead associated with sending detailed coverage information for a TN cell (such as the centroid or coverage radius of the TN cell), the base station sends a compact indication of the segment or portion of the NTN cell in the NTN cell in which the TN cell operates. For example, the base station and the UE may share a configuration according to which the TN cell consists of exactly N segments, which may be circular segments of equal size, and according to which the base station and the UE can unambiguously identify these segments. When the base station sends system information indicating the TN frequencies on which the UE can search for TN cells within the NTN cell, the base station attaches this compact indication to each TN frequency. The UE then uses the TN frequency for search and / or measurement only when the UE is located within the corresponding segment (or the UE is sufficiently close to the segment).

[0045] First reference Figure 1 The example wireless communication system 100 includes a UE 102, a TN base station (BS) 104, a TN base station 106, an NTN base station 105 associated with a satellite (refer to Figure 3A and Figure 3B 10) and a core network (CN) 110. Base stations 104, 105, and 106 operate in a RAN 105 connected to the CN 110 and other base station components. For example, the CN 110 may be implemented as an evolved packet core (EPC) 111 and / or a fifth generation (5G) core (5GC) 160. The CN 110 may also be implemented as a sixth generation (6G) core and future evolutions.

[0046] Base station 104 covers TN cell 124, and base station 106 covers TN cell 126. Base station 105 covers NTN cell 125, which is significantly larger than TN cells 124 and 126. TN cells 124 and 126 may be disposed entirely or partially within NTN 125, such that a UE 102 operating in a connected state may perform a handover from NTN base station 105 to TN base station 102 or 104, or a UE 102 operating in an idle or inactive state may reselect from NTN cell 125 to TN cell 124 or 126.

[0047] If base station 104 is a gNB, cell 124 is an NR cell. If base station 104 is an ng-eNB or eNB, cell 124 is an Evolved Universal Terrestrial Radio Access (E-UTRA) cell. Similarly, if base station 106 is a gNB, cell 126 is an NR cell, and if base station 106 is an ng-eNB or eNB, cell 126 is an E-UTRA cell. Cells 124 and 126 may be in the same radio access network notification area (RNA) or in different RNAs. In general, RAN 105 may include any number of terrestrial base stations and non-terrestrial base stations, and each of the base stations may cover one, two, three, or any other suitable number of cells. UE 102 may support at least 5G NR (or simply "NR") or E-UTRA air interface to communicate with base stations 104 and 106. Each of base stations 104, 106 is connected to CN 110 via an interface (e.g., S1 or NG interface). The base stations 104 and 106 may also be interconnected via an interface for interconnecting NG RAN nodes (e.g., an X2 or Xn interface).

[0048] Among other components, EPC 111 may include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. SGW 112 is generally configured to deliver user plane packets associated with audio calls, video calls, internet traffic, and the like, while MME 114 is configured to manage authentication, registration, paging, and other related functions. PGW 116 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). 5GC 160 includes a user plane function (UPF) 162, an access and mobility management function (AMF) 164, and / or a session management function (SMF) 166. Generally speaking, UPF 162 is configured to deliver user plane packets associated with audio calls, video calls, internet traffic, and the like, AMF 164 is configured to manage authentication, registration, paging, and other related functions, and SMF 166 is configured to manage PDU sessions.

[0049] To exchange messages or information directly, base stations 104, 105, and 106 may support an X2 or Xn interface. In general, CN 110 may be connected to any suitable number of terrestrial base stations and non-terrestrial base stations that support NR cells and / or EUTRA cells.

[0050] As discussed in detail below, the UE 102 and / or RAN 105 can utilize the techniques of the present disclosure when the radio connection between the UE 102 and the RAN 105 is suspended, for example, when the UE 102 is operating in an inactive or idle state of a protocol for controlling radio resources between the UE 102 and the RAN 105. For clarity, the examples below refer to the RRC_INACTIVE or RRC_IDLE states of the RRC protocol. The UE 102 can further utilize the techniques of the present disclosure when the radio connection between the UE 102 and the RAN 105 is disconnected and operating in PSM where no radio resource control (RRC) protocol relationship exists between the UE and the network.

[0051] The base station 104 is equipped with a transceiver and processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and non-transitory computer-readable memory storing instructions executed by the one or more general-purpose processors. Additionally or alternatively, the processing hardware 130 may include a dedicated processing unit. In an example implementation, the processing hardware 130 includes a processor 132 to process data to be transmitted by the base station 104 in the downlink direction, or to process data received by the base station 104 in the uplink direction. The processing hardware 130 may also include a transmitter 136 configured to transmit data in the downlink direction. The processing hardware may further include a receiver 134 configured to receive data in the uplink direction. The base station 106 may include substantially similar components. Specifically, components 140, 142, 144, and 146 of the base station 106 may be similar to components 130, 132, 134, and 136, respectively.

[0052] The UE 102 is equipped with a transceiver and processing hardware 150, which may include one or more general-purpose processors such as a CPU and non-transitory computer-readable memory storing machine-readable instructions that can be executed on the one or more general-purpose processors, and / or a dedicated processing unit. In an example implementation, the processing hardware 150 includes a processor 152 to process data to be transmitted by the UE 102 in the uplink direction, or to process data received by the UE 102 in the downlink direction. The processing hardware 150 may also include a transmitter 156 configured to transmit data in the downlink direction. The processing hardware may also include a receiver 154 configured to receive data in the uplink direction.

[0053] like Figure 2 As shown, various functions may be distributed between the RAN 105 and the 5GC 160, and further distributed between different components of the 5GC 160, such as the AMF 164 and the SMF 166.

[0054] Specifically, base station 202 (e.g., base station 104 or 106) can host the following main functions: radio resource management, such as radio bearer control, radio admission control, connection mobility control, dynamic allocation of resources to UEs in both uplink and downlink (scheduling); IP header compression, encryption and integrity protection of data; selection of AMF upon UE attachment when the route to the AMF cannot be determined based on information provided by the UE; routing of user plane data to UPF; routing of control plane information to AMF; connection establishment and release; scheduling and transmission of paging messages; scheduling and transmission of system broadcast information (originating from AMF or OAM); measurement and measurement report configuration for mobility and scheduling; transport level packet marking in uplink; session management; support for network slicing; QoS flow management and mapping to data radio bearers; support for UE in RRC_INACTIVE state; distribution of NAS messages; radio access network sharing; dual connectivity; and interworking between NR and E-UTRA.

[0055] The AMF 204 may host the following functions: NAS signaling termination; NAS signaling security; AS security control; CN inter-node signaling for mobility between 3GPP access networks; idle mode UE reachability (including control and execution of paging retransmissions); registration area management; support for intra-system and inter-system mobility; access authentication; access authorization, including roaming rights check; mobility management control (subscription and policy); support for network slicing; and SMF selection.

[0056] The UPF 206 may host the following functions: anchor support for intra-RAT / inter-RAT mobility (where applicable); session point for interconnection of external PDUs to data networks; packet routing and forwarding; packet inspection and user plane portion of policy rule enforcement; traffic usage reporting; uplink classification to support routing of traffic flows to data networks; branching point to support multi-homed PDU sessions; QoS handling for the user plane, e.g., packet filtering, gating, UL / DL rate enforcement; uplink traffic validation (SDF to QoS flow mapping); and downlink packet buffering and downlink data notification triggering.

[0057] Finally, the SMF 208 may provide session management; UE IP address allocation and management; selection and control of UP functions; configuration of traffic steering at the User Plane Function (UPF) to route traffic to the correct destination; control of policy enforcement and QoS; and downlink data notification.

[0058] Figure 3A A certain type of NTN deployment, referred to as a transparent payload architecture, is shown involving a satellite gateway 302 and a "transparent" satellite 304 for extending the range of the Uu interface. This NTN deployment can be incorporated into a base station 105 or a base station 104 or 106 as an extension of the base station. Figure 1 A's RAN 105. Satellite 304 implements frequency conversion and radio frequency (RF) amplification in both the uplink and downlink directions. The satellite functions similarly to an analog RF repeater. Thus, satellite 304 relays the Uu radio interface from the feeder link (between the NTN gateway and the satellite) to the serving link (between the satellite and the UE) in the downlink direction, and vice versa in the uplink direction. The satellite radio interface (SRI) on the feeder link is Uu, and the NTN gateway 302 supports all necessary functions for forwarding signals of the Uu interface. The NTN gateway 302 operates at the same site (location) as the base station (e.g., eNB, gNB) 104, or is connected to the base station 104 at a distance via a wired link. More than one NTN gateway can also be connected to a base station. Different transparent satellites can be connected to the same base station on the ground via the same NTN gateway or via different NTN gateways.

[0059] Figure 3B An implementation is shown where two different satellites (304 and 306) are connected to the same base station 104 via the same NTN gateway 302 and the two satellites (304 and 306) cover the Earth's surface using two different physical cell IDs (PCIs).

[0060] Next, Figure 4A The NTN user plane protocol stack involving UE 102, satellite 304, NTN gateway 302, base station 104 and EPC S-GW 112 (or 5GC SMF 166) is shown. The NTN user plane protocol stack is similar to the protocol stack of the terrestrial network (TN), except that Figure 4A The configuration of shows two additional nodes operating in the middle of the Uu interface - Satellite 304 and NTN Gateway 302. Similarly, Figure 4B The NTN control plane protocol stack shown in is also roughly similar to Figure 2 The protocol stack of the terrestrial network counterpart shown in B.

[0061] Overall reference Figures 1 to 4B , NTN supports at least three types of service links NTN described in terms of satellite mobility patterns: (i) Geofixed: configured by beams that always continuously cover the same geographical area (e.g., the case of GEO / GSO satellites); (ii) Quasi-Geofixed: configured by beams that cover one geographical area for a limited period of time and a different geographical area during another period of time (e.g., the case of LEO / MEO satellites capable of using steerable beams); and (iii) Geomobile: configured by beams whose coverage area slides above the surface of the Earth (e.g., the case of LEO / MEO satellites using fixed or non-steerable beams).

[0062] Using LEO / MEO satellites, base stations can provide quasi-Earth-fixed cell coverage or Earth-mobile cell coverage. Using GEO satellites, base stations can provide Earth-fixed cell coverage.

[0063] although Figure 3A and Figure 3B The transparent payload architecture shown in [1] is currently the focus of 3GPP development, but a regenerative payload architecture, which places some base station functionality on the satellite, is also a possible future NTN deployment. In this architecture, the Uu exists only between the satellite and the UE. In general, the techniques of this disclosure can be applied to both transparent and regenerative payload architectures.

[0064] Figure 5 An example scenario 500 is shown in which, when a UE is in an idle or inactive state and camped on an NTN cell, the network (e.g., RAN 105 and / or CN 110) configures the UE to measure TN frequencies associated with a TN cell. In this example, multiple TN cells exist within NTN cell 125, with the TN cells operating on carrier frequency b and NTN cell 125 operating on carrier frequency a. The base station of NTN cell 125 broadcasts information related to inter-frequency measurements in SIB4. This information contains the information required for the UE to perform inter-frequency measurements on carrier frequency b, including the Absolute Radio Frequency Channel Number (ARFCN) value of carrier frequency b, the SSB Measurement Timing Configuration (SMTC), the cell reselection priority of carrier frequency b, and a neighbor cell list that lists the physical cell identities of neighboring TN cells using carrier frequency b. Assuming that the cell reselection priority of carrier frequency b is higher than the cell reselection priority of the serving frequency (i.e., carrier frequency a), in some implementations, the UE in the idle / inactive state performs measurements on carrier frequency b.

[0065] To allow the UE to forgo measurements on carrier frequency b when the UE is not near any TN cell and thus save power and time, the base station of the NTN cell 125 may provide TN coverage information in system information (SI). In one implementation, the base station provides TN coverage information for each TN cell in the neighbor cell list in SIB4 (e.g., Figure 5 TN AreaInfo in . In another implementation, the base station provides TN coverage information in a separate list and may not be TN cell specific. A UE camping on an NTN cell 125 first processes SIB4 and determines whether carrier frequency b is a TN frequency or an NTN frequency based on the ARFCN value. If the carrier frequency is a TN frequency, the UE may need to obtain TN coverage information for carrier frequency b from the neighbor cell list or from a separate TN coverage information list (e.g. Figure 5 The UE may then determine whether (and how) to perform measurements on carrier frequency b based on whether the UE is within or near any TN cell coverage. The UE may also determine whether (and how) to perform measurements on a specific TN cell listed in the neighbor cell list based on whether the UE is within or near the TN cell coverage.

[0066] However, if Figure 5 As shown, the base station of the NTN cell 125 must broadcast coverage information of each TN cell within the NTN cell coverage (20 TN cells in this example), which may cause the SIB4 to exceed the size limit when there are many TN cells within the NTN cell coverage.

[0067] To reduce the signaling overhead caused by the detailed cell coverage information discussed above, the base station 105 or another suitable base station provides coarse or more abstract TN coverage information in the NTN cell, rather than detailed TN coverage information. The coarse TN coverage information indicates a coarser level of TN coverage, but requires much less bandwidth to convey or otherwise provide the coarse TN coverage information in the NTN cell in a system information block. The coarse TN coverage information can indicate the segments into which the base station and the UE can logically divide the NTN cell. For example, the base station 105 and the UE 102 can have a common understanding that the substantially circular coverage area of ​​the NTN cell 125 includes N equally sized circular sectors, where the left boundary of sector #0 is aligned with the true north direction, and subsequent sectors form a sequence in a clockwise direction.

[0068] Using the rough TN coverage information, the UE can reduce its power consumption in some cases. In some implementations, the UE can obtain detailed TN coverage information from the base station, such as reference Figures 10 to 12 discussed.

[0069] like Figure 6A As shown, each TN carrier frequency (e.g., carrier frequency j) listed in SIB4 is configured to include a 4-bit TNAreaBimap associated with that carrier frequency. The 4-bit TNAreaBitmap indicates to the base station and the UE whether any TN cells are deployed in the four equal-sized areas into which the NTN cell is divided using a reference position, which the base station can provide in SIB19. These four areas are labeled as areas I, II, III, and IV and are mapped to bits 1, 2, 3, and 4 in the TNAreaBitmap, respectively. Figure 6A In the example shown, since two TN cells are deployed in region I and one TN cell is deployed in region III, the values ​​within the TNAreaBitmap are {1, 0, 1, 0}. For those NTN frequency configurations listed in SIB4 (e.g., carrier frequency k), they do not need to include a TNAreaBitmap. The UE can determine whether the carrier frequency listed in SIB4 is a TN frequency or an NTN frequency based on: (1) the ARFCN value, or (2) whether the same carrier frequency can also be found in the neighboring cell configuration in SIB19. If the UE determines that the carrier frequency listed in SIB4 is a TN frequency, the UE can expect to receive a TNAreaBitmap associated with the carrier frequency in SIB4. When the UE cannot find a TNAreaBitmap in the configuration of a TN frequency in SIB4, the UE may not be allowed to modify (or relax) the measurement on the TN frequency, that is, the UE must comply with the default measurement requirements when performing measurements on the TN frequency.

[0070] In another implementation, the reference location of the NTN cell 124 is Figure 6B The NTN cells in the data center are divided into eight equal-sized regions instead of four. Therefore, the length of TNAreaBitmap becomes 8 bits, where each bit indicates whether any TN cells are deployed in the corresponding region. In this example, since TN cells are deployed in regions I, II, V, and VI, the values ​​in TNAreaBitmap are {1,1,0,0,1,1,0,0}. In other implementations, the NTN cells can be divided into any number of equal-sized regions based on the reference location. In such implementations, the length of TNAreaBitmap can be equal to the number of regions that divide the NTN cells.

[0071] Next, refer to Figures 7 to 12 Several example scenarios are discussed in which the UE and / or RAN implement the disclosed techniques for supporting NTN to TN mobility in idle or inactive state with enhanced UE power saving. Figures 7 to 12Similar events are labeled with similar reference numerals, and differences are discussed below where appropriate. For example, event 708 is similar to event 808, and event 742 is similar to event 942. To simplify the following description, the term "idle state" is used and can refer to either the RRC_IDLE or RRC_INACTIVE state, and the term "connected state" is used and can refer to the RRC_CONNECTED state.

[0072] Figure 7 is an example messaging diagram 700 illustrating how a UE in idle state may trigger measurements on a TN cell operating on a TN carrier frequency in an NTN. Figure 7 , UE 102 initially camps on an NTN cell 124 managed by BS 104 via satellite 304, where NTN cell 124 covers another TN cell 127 within its coverage. While remaining 702 in an idle state, UE 102 receives 704 a first system information message in NTN cell 124, the first system information message including a reference location and a list of {TN frequency, TNAreaBitmap} pairs, which may be conveyed in a frequency configuration list in SIB4.

[0073] In response to the first system information message, UE 102 applies the following actions / steps for each TN frequency listed in the first system information message.

[0074] UE 102 divides 706 the NTN cell 124 into regions / areas based on the reference location, e.g., four regions / areas of equal size. The manner in which UE 102 divides the NTN serving cell into the regions of equal size can be a fixed rule defined in a specification. For example, UE 102 always divides the NTN serving cell into four regions separated by latitude and longitude lines that intersect at the serving cell's reference location. The manner in which UE 102 divides the NTN serving cell can be dynamically based on the length of the TNAreaBitmap associated with the TN frequency. For example, if the length of the TNAreaBitmap associated with the TN frequency is equal to n bits, then UE 102 can divide the NTN serving cell into n regions of equal size.

[0075] Thereafter, the UE 102 determines which region (the aforementioned divided regions) it is in by comparing its GNSS coordinates with the latitude and longitude of the reference position, and then determines 708 that the region it falls into is represented by the value '1' in the TNAreaBitmap (i.e., there is a TN cell). Since the region in which the UE 102 falls has TN cells deployed, the UE 102 searches 742 for TN cells on the TN frequency and may then detect the TN cell 127. Once the UE 102 detects the TN cell 127, the UE 102 needs to perform 744 necessary and routine measurements on the TN cell 127 for the cell reselection evaluation process. At a later time, if the TN cell 127 meets the cell reselection criteria, the UE 102 may need to reselect and camp 746 on the TN cell 127. Events 742, 744, and optionally 746 are described in detail in detail in the text. Figure 7 It is generally referred to as the process for making measurements on TN frequencies / cells and evaluating the cell reselection criteria.

[0076] Figure 8 is an example messaging diagram 800 illustrating how a UE in an idle state may determine in an NTN not to measure a carrier frequency or a TN cell when the UE is not in proximity to the TN cell operating in the TN carrier frequency. Figure 8 The message diagram in Figure 7 The message diagrams in are similar, with the differences discussed below. Figure 8 In FIG, after dividing 706 the NTN cells 124 into regions / areas, the UE 102 determines 808 that the region it falls into is represented by a value of '0' in the TNAreaBitmap (ie, no TN cells are nearby). In response to this determination, the UE 102 determines 848 not to measure on TN frequencies.

[0077] Figure 9 is an example messaging diagram 900 illustrating how a UE in idle state may trigger relaxed measurements on a TN carrier frequency or on a TN cell in an NTN when the UE may be close to the TN cell operating in the carrier frequency. Figure 9 The message diagram in Figure 7 The message diagrams in are similar, with the differences discussed below. Figure 9 , after determining 708 that the area it falls into is represented by a value of '1' in TNAreaBitmap (i.e., there are TN cells), the UE 102 determines 912 that it complies with relaxed measurement requirements, wherein the relaxed measurement requirements allow the UE 102 to measure at longer intervals. For example, conventional NR measurement requirements include three parameters that the UE needs to meet in measuring inter-frequency cells: T detect,NR_Inter 、T measure,NR_Inter and T evaluation,NR_Inter . T detect,NR_Inter 、Tmeasure,NR_Inter and T Evaluation,NR_Inter The definition of can be found in 3GPP TS38.133 (v17.7.0). On the other hand, the relaxed NR measurement requirements include three additional parameters that the UE needs to meet in measuring inter-frequency cells: TR detect,NR_Inter , TR measure,NR_Inter and TR evaluation,NR_Inter , where TR detect,NR_Inter = T detect,NR_Inter * C, TR measure,NR_Inter = T measure,NR_Inter * C, and TR evaluation,NR_Inter = T evaluation,NR_Inter * C. C is a constant (integer or non-integer) value greater than one.

[0078] Thereafter, the UE 102 searches 942 for TN cells on the TN frequency based on the relaxed measurement requirements and may then detect the TN cell 127. Once the UE 102 detects the TN cell 127, the UE 102 determines 914 that the conventional (i.e., non-relaxed) measurement requirements are adhered to and then performs 744 necessary and conventional measurements for the cell reselection evaluation procedure on the TN cell 127. At a later time, if the TN cell 127 meets the cell reselection criteria, the UE 102 may need to reselect and camp 746 on the TN cell 127.

[0079] Figure 10 is an example messaging diagram 1000 illustrating how a UE in idle state may use an RRC recovery procedure to obtain detailed TN coverage information when the UE may be close to a TN cell operating in a TN carrier frequency. Figure 10 The message diagram in Figure 7 The message diagrams in are similar, with the differences discussed below. Figure 10 , after determining 708 that the region it falls into is indicated by the value '1' in TNAreaBitmap (i.e., there is a TN cell), the UE 102 performs (1022) a 2-step or 4-step random access (RA) procedure to obtain an UL grant (in the case of a 4-step RA) or PUSCH resources (in the case of a 2-step RA), and then sends 1024 an RRC recovery request message (e.g., an RRCResumeRequest or RRCResumeRequest1 message) along with a UL MAC CE that contains a bit string of the same size as the TNAreaBitmap and indicates which region the UE 102 is in.

[0080] In response to the RRC resume request message and the UL MAC CE, BS 104 sends an RRC release message that includes detailed coverage information for the TN cells in the area. The detailed coverage information may include a reference location (e.g., cell center coordinates) and a cell radius / cell diameter / distance threshold for each TN cell. After receiving the RRC release message, UE 102 remains in the idle state and then determines 1030 whether UE 102 is within coverage of at least one TN cell based on the UE location and the detailed TN coverage information. Since, in this example, UE 102 is within cell coverage of TN cell 127, the determination in event 1030 is positive; therefore, UE 102 performs 740 a process for taking measurements on TN frequencies / cells and evaluating cell reselection criteria.

[0081] Figure 11 is an example messaging diagram 1100 illustrating how a UE in idle state may resume its RRC connection and obtain detailed TN coverage information when the UE may be close to a TN cell operating in a TN carrier frequency. Figure 11 The message diagram in Figure 7 The message diagrams in are similar, with the differences discussed below. Figure 11 , after determining 708 that the area it falls into is represented by the value '1' in TNAreaBitmap (i.e., there is a TN cell), in one implementation, the UE 102 performs 1150 an RRC connection recovery procedure with the BS 104 via the NTN cell 124 and thus transitions 1152 to the connected state; in another implementation, the UE performs an RRC connection establishment procedure and a security command procedure with the BS 104 via the NTN cell 124 and then transitions to the connected state.

[0082] After transitioning to the connected state, UE 102 sends 1154 a UL DCCH (Dedicated Control Channel) message containing a bit string the same size as TNAreaBitmap and indicating which region UE 102 is in. Note that UE 102 may attempt to obtain an UL grant (e.g., perform an SR or BSR) before sending the UL DCCH message. In response to the UL DCCH message, BS 104 sends 1156 a DL DCCH message including detailed coverage information for the TN cells in the region. The detailed coverage information may include a reference location (e.g., cell center coordinates) and a cell radius / cell diameter / distance threshold for each TN cell. At a later time, after the RRC inactivity timer expires (i.e., no traffic occurs between UE 102 and BS 104 for a period of time), the BS sends 1158 an RRC release message to UE 102.

[0083] After receiving the RRC release message, UE 102 transitions 1160 to an idle state and then determines 1030 whether UE 102 is within coverage of at least one TN cell based on the UE location and detailed TN coverage information. Since, in this example, UE 102 is within cell coverage of TN cell 127, the determination in event 1030 is positive; therefore, UE 102 performs 740 a process for taking measurements on TN frequencies / cells and evaluating cell reselection criteria.

[0084] Figure 12 is an example messaging diagram 1200 illustrating how a UE in idle state may use an on-demand SI acquisition procedure to acquire detailed TN coverage information when the UE may be close to a TN cell operating in a TN carrier frequency. Figure 12 The message diagram in Figure 7 The message diagrams in are similar, with the differences discussed below. Figure 12 In the example, after determining 708 that the area it falls into is indicated by a value of '1' in the TNAreaBitmap (i.e., a TN cell is present), UE 102 performs (1228) a 2-step or 4-step random access (RA) procedure to initiate an on-demand SI acquisition procedure. UE 102 may transmit a dedicated preamble or an RRC system information request message after obtaining UL grant / PUSCH resources through the RA procedure to indicate a desired SI message. In this example, the desired SI message is an SI message that includes detailed coverage information of TN cells within a specific area or the entire coverage of NTN cell 124. After receiving the desired SI message, UE 102 determines 1030 whether UE 102 is within the coverage of at least one TN cell based on the UE location and the detailed TN coverage information. Since, in this example, UE 102 is within the cell coverage of TN cell 127, the determination in event 1030 is positive; therefore, UE 102 performs 740 a process for performing measurements on TN frequencies / cells and evaluating cell reselection criteria.

[0085] Figure 131300 is a flow chart of an example method 1300 that can be implemented by a UE in an idle state (e.g., UE 102 in the present disclosure) for determining whether to perform measurements on a TN carrier frequency in an NTN based on coarse TN coverage information. Initially, at block 1304, the UE receives system information from a base station via a satellite payload. The system information includes a reference location of a serving cell and a list of the following pairs: {TN frequency, TNAreaBitmap}. The flow then proceeds to block 1305, where the UE selects a TN frequency from the listed TN frequencies. Thereafter, at block 1306, the UE divides the serving cell into regions based on the reference location of the serving cell and, optionally, the length of the TNAreaBitmap associated with the selected TN frequency.

[0086] Flow then proceeds to decision block 1308 where the UE determines whether the UE is within one of the regions having a value of '1' in the TNAreaBitmap associated with the chosen TN frequency.

[0087] If the determination at block 1308 is 'yes' (i.e., the UE is within one of the regions having a value of '1' in the TNAreaBitmap), then the flow proceeds to block 1342, where the UE searches for cells on the TN frequency that the UE has selected. If the UE detects any TN cells operating on the TN frequency, the UE may perform 1344 measurements on the detected TN cells for the cell reselection evaluation procedure. Thereafter, the flow proceeds to decision block 1309. Note that if, after performing 1344 the necessary measurements on the detected TN cells, the UE finds any TN cell among the detected TN cells that meets the cell reselection criteria, then the UE may camp on one of the TN cells that meets the cell reselection criteria, which ends the entire process.

[0088] On the other hand, if the determination at box 1308 is ‘No’ (i.e., the UE is not within one of the areas having a value of ‘1’ in TNAreaBitmap), the process proceeds to box 1348 where the UE determines not to search for cells on the selected TN frequency, and then the process proceeds to decision box 1309.

[0089] In decision block 1309, the UE checks whether there are any TN frequencies still listed in SIB4 that have not been selected by the UE. If there is still at least one TN frequency that has not been selected by the UE (i.e., the yes branch after decision block 1309), the process loops back to block 1305. Otherwise (the no branch after decision block 1309), the process proceeds to block 1398, which marks the end of the entire process.

[0090] Figure 14is a flow chart of an example method 1400 that may be implemented by a UE in an idle state (eg, UE 102 in the present disclosure) for determining whether to perform relaxed measurements on a TN carrier frequency in an NTN based on coarse TN coverage information. Figure 14 The flowchart in Figure 13 The flowcharts in are similar, and the differences are discussed below. Figure 14 If the determination at block 1308 is 'yes' (i.e., the UE is within one of the regions having a value of '1' in TNAreaBitmap), the flow proceeds to block 1412, where the UE determines that the relaxed measurement requirements are adhered to when measuring any TN frequency / cell. Then, at block 1442, the UE searches for cells on the TN frequency selected by the UE at block 1305 based on the relaxed measurement requirements.

[0091] Thereafter, the flow proceeds to another decision block 1443, where the UE determines whether it has detected any TN cells when searching for cells on the TN frequencies at block 1442. If the UE detects at least one TN cell (i.e., the yes branch following decision block 1443), then at block 1414, the UE determines that conventional measurement requirements are adhered to when measuring any TN frequencies / cells, and then performs the necessary measurements on the detected TN cells for the cell reselection evaluation procedure at block 1344. However, if the UE does not detect any TN cells (i.e., the no branch following decision block 1443), the flow skips blocks 1414 and 1344 and proceeds directly to the final decision block 1309, where the UE checks whether there are any TN frequencies still listed in SIB4 that have not yet been selected by the UE.

[0092] Figure 15 is a flow chart of an example method 1500 that may be implemented by a UE in an idle state (eg, UE 102 in the present disclosure) for determining whether to acquire detailed TN coverage information using an RRC recovery procedure. Figure 15 The flowchart in Figure 13 The flowcharts in are similar, and the differences are discussed below. Figure 15If the determination at block 1308 is 'yes' (i.e., the UE is within one of the regions having a value of '1' in the TNAreaBitmap), the flow proceeds to block 1522, where the UE initiates a random access procedure by transmitting a random access preamble to the BS. Then, at block 1524, the UE sends an RRC resume request message plus a UL MAC CE to the base station using the random access procedure initiated at block 1522, the UL MAC CE indicating the region within which the UE is located. Thereafter, at block 1526, the UE receives an RRC release message from the base station, the RRC release message including detailed TN coverage information for the indicated region. The detailed TN coverage information may include a reference location (e.g., cell center coordinates) and a cell radius / cell diameter / distance threshold for each TN cell.

[0093] Thereafter, the flow proceeds to another decision block 1530, where the UE determines whether the UE is within any TN coverage based on the UE location information and the detailed TN coverage information obtained at block 1526. If it is within any TN coverage (i.e., the yes branch after decision block 1530), then at block 1342, the UE searches for cells on the TN frequency that the UE has selected, and at block 1344, necessary measurements may be performed on the detected TN cells for the cell reselection evaluation procedure. However, if the UE is not within any TN coverage (i.e., the no branch after decision block 1530), the flow skips blocks 1342 and 1344 and proceeds directly to the final decision block 1309, where the UE checks whether there are any TN frequencies that are still listed in SIB4 and not currently selected by the UE.

[0094] Figure 16 is a flow chart of an example method 1600 that may be implemented by a UE in an idle state (eg, UE 102 in the present disclosure) for determining whether to resume its RRC connection and obtain detailed TN coverage information. Figure 16 The flowchart in Figure 15 The flowcharts in are similar, and the differences are discussed below. Figure 16, if the determination at box 1308 is 'yes' (i.e., the UE is within one of the areas having a value of '1' in TNAreaBitmap), the process proceeds to box 1650, where the UE initiates an RRC connection recovery procedure by transmitting an RRC recovery request message to the BS. After receiving the RRC recovery message from the BS and transitioning to the connected state, at box 1654, the UE sends a UL DCCH message to the BS, which indicates the area within which the UE is within. Thereafter, at box 1656, the UE receives a DL DCCH message from the BS, which includes detailed TN coverage information for the indicated area. The detailed TN coverage information may include a reference location (e.g., cell center coordinates) and a cell radius / cell diameter / distance threshold for each TN cell. At a later time, at box 1658, the UE receives an RRC release message from the BS, which transitions the UE to the idle state again. The rest of the process is the same as Figure 15 The rest of the same.

[0095] Figure 17 is a flow chart of an example method 1700 that may be implemented by a UE in an idle state (eg, UE 102 in the present disclosure) for determining whether to acquire detailed TN coverage information using an on-demand SI acquisition procedure. Figure 17 The flowchart in Figure 15 The flowcharts in are similar, and the differences are discussed below. Figure 17 , if the determination at box 1308 is 'yes' (i.e., the UE is within one of the areas having a value of '1' in TNAreaBitmap), the process proceeds to box 1522, where the UE initiates a random access procedure by transmitting a random access preamble to the BS. Then, at box 1728, the UE sends an SI request message to the BS using the random access procedure initiated at box 1522, which is used to request detailed TN coverage information of the area within which the UE is located or of interest. Thereafter, at box 1729, the UE receives an SI message from the BS, which includes at least detailed TN coverage information of the indicated area. The SI message received at box 1729 may also include detailed TN coverage information of other areas that the UE is not within or of which it is not interested. The detailed TN coverage information may include a reference location (e.g., cell center coordinates) and a cell radius / cell diameter / distance threshold for each TN cell. The remainder of the process is the same as Figure 15 The rest of the same.

[0096] Figure 1818 is a flow chart of an example method 1800 that can be implemented by a base station (e.g., BS 104 in the present disclosure) for determining coarse TN coverage information and broadcasting the coarse TN coverage information in system information. Initially, at block 1801, the base station divides a serving cell into regions based on a reference location and, optionally, the length of a TNAreaBitmap. The number of divided regions can be a fixed number predefined in the specification, or a dynamic number aligned with the length of the TNAreaBitmap. In one implementation, the base station divides the serving cell into regions whose edges intersect at the reference location.

[0097] At block 1803, the BS determines the value of each bit in the associated TNAreaBitmap for each TN frequency based on whether there are any TN cells in the corresponding area that the BS has divided at block 1801. After the BS has determined the TNAreaBitmap value for each TN frequency, at block 1804, the BS broadcasts a message including system information, a reference location of the system information serving cell, and a list of the following pairs: {TN frequency, TNAreaBitmap}.

[0098] Figure 19 1 is a flow chart of an example method 1900 that can be implemented by a BS (e.g., BS 104 in the present disclosure) for delivering detailed TN coverage information to a UE during an RRC recovery process. Method 1900 can be performed by the BS after method 1800. After performing method 1800, at block 1924, the BS receives an RRC recovery request message plus an UL MAC CE from the UE, the UL MAC CE indicating the area within which the UE is located. In response to the RRC recovery request message and the UL MAC CE, at block 1926, the BS sends an RRC release message to the UE, the RRC release message including detailed coverage information of the TN cells in the indicated area. The detailed coverage information may include a reference location (e.g., cell center coordinates) and a cell radius / cell diameter / distance threshold for each TN cell.

[0099] Figure 202 is a flow chart of an example method 2000 that can be implemented by a BS (e.g., BS 104 in the present disclosure) for delivering detailed TN coverage information to a UE in a DL DCCH message. Method 2000 can be performed by the BS after method 1800. After performing method 1800, at block 2054, the BS receives a UL DCCH message from the UE, the UL DCCH message indicating the area within which the UE is located. In response to the UL DCCH message, at block 2056, the BS sends a DL DCCH message to the UE, the DL DCCH message including detailed coverage information of the TN cells in the indicated area. The detailed coverage information can include a reference location (e.g., cell center coordinates) and a cell radius / cell diameter / distance threshold for each TN cell.

[0100] Figure 21 21 is a flowchart of an example method 2100 for broadcasting detailed TN coverage information in on-demand system information that can be implemented by a BS (e.g., BS 104 in the present disclosure). Method 2100 can be performed by the BS after method 1800. After performing method 1800, at box 2128, the BS receives an SI request message from the UE, which SI request message queries detailed TN coverage information for a specific area or queries detailed TN coverage information without indicating a specific area. In response to the SI request message, at box 2129, the BS broadcasts system information to the UE, the system information including at least detailed TN coverage information of the area queried by the UE. At box 2129, the BS may broadcast system information including detailed TN coverage information for each TN cell within the NTN cell. The detailed coverage information may include a reference location (e.g., cell center coordinates) and a cell radius / cell diameter / distance threshold for each TN cell.

[0101] Figure 22 An example method 2200 is shown that may be implemented by a UE (e.g., UE 102) for communicating with a RAN (e.g., RAN 105, base station 104, base station 106, or DU 174).

[0102] Method 2200 begins at block 2202, where a UE receives system information including at least one TN frequency from a base station via a satellite over an NTN frequency (e.g., event 704). At block 2204, the UE selects one of the at least one TN frequency. At block 2206, the UE searches for a TN cell on the selected TN frequency once per a first time period. At block 2208, the UE determines whether the UE has found a TN cell on the selected TN frequency. If the UE determines that the UE has found a TN cell on the selected carrier frequency, the process proceeds to block 2210. At block 2210, the UE measures the TN cell N times per a second time period, where N > 0. At block 2212, the UE performs a cell reselection evaluation based on the measurement results of the TN cell. At block 2214, the UE determines whether the TN cell is eligible for cell reselection. If the UE determines that the TN cell is eligible for cell reselection at block 2214, the process proceeds to block 2216, where the UE reselects the eligible TN cell for cell reselection. Otherwise, if at block 2214 the UE determines that the TN cell is not eligible for cell reselection, the process proceeds to block 2218. At block 2218, the UE determines whether there are any remaining TN frequencies among the at least one TN frequency that have not been selected by the UE. If at block 2218 the UE determines that there are any TN frequencies that have not been selected by the UE, the process proceeds to block 2220. At block 2220, the UE selects the TN frequency and the process proceeds to block 2206. Otherwise, if at block 2218 the UE determines that there are no TN frequencies that have not been selected by the UE, the process proceeds to block 2222, where the process ends. If at block 2208 the UE determines that the UE has not found a TN cell, the process proceeds to block 2218.

[0103] In some implementations, the first time period and the second time period are different. For example, the first time period is longer than the second time period. In other implementations, the first time period and the second time period are the same. In such cases, N can be greater than one.

[0104] Figure 23 An example method 2300 is shown that may be implemented by a UE (e.g., UE 102) for communicating with a RAN (e.g., RAN 105, base station 104, base station 106, or DU 174).

[0105] Method 2300 begins at block 2302, where the UE receives system information including a carrier frequency from a base station via a satellite on an NTN frequency (e.g., event 704). At block 2304, the UE determines whether the frequency is a TN frequency. If, at block 2304, the UE determines that the carrier frequency is a TN frequency, the process proceeds to block 2306. At block 2306, the UE searches for a TN cell on the TN frequency once per a first time period. Otherwise, if, at block 2304, the UE determines that the carrier frequency is an NTN frequency, the process proceeds to block 2308. At block 2308, the UE searches for an NTN cell on the NTN frequency once per a second time period.

[0106] In some implementations, the first time period and the second time period are different. For example, the first time period is longer than the second time period. In other implementations, the first time period and the second time period are the same. In such cases, N can be greater than one.

[0107] Figure 24 An example method 2400 is shown that may be implemented by a UE (e.g., UE 102) for communicating with a RAN (e.g., RAN 105, base station 104, base station 106, or DU 174).

[0108] Method 2400 begins at block 2402, where the UE obtains location information for one or more TN cells. At block 2404, the UE camps on an NTN cell of a BS. At block 2406, the UE determines, based on the location information, whether the UE is near or within coverage of a TN cell. If, at block 2406, the UE determines, based on the location information, that the UE is near or within coverage of a TN cell, the process proceeds to block 2408. At block 2408, the UE searches for the TN cell. The UE may search for the TN cell while camped on an NTN cell. Otherwise, if, at block 2406, the UE determines, based on the location information, that the UE is not near and / or not within coverage of a TN cell, the process proceeds to block 2410. At block 2410, the UE refrains from searching for TN cells. The UE may refrain from searching for TN cells while camped on an NTN cell.

[0109] In some implementations, when operating in a connected state (e.g., RRC_CONNECTED state), the UE receives location information of a TN cell from the core network via the RAN (e.g., a TN cell or an NTN cell (e.g., the NTN cell in block 2404 or another NTN cell)). The UE may receive one or more dedicated messages including the location information from the core network via the RAN. In other implementations, the UE receives the location information of the TN cell from the RAN. In one implementation, the UE receives the location information of the TN cell from the RAN via system information (e.g., event 704). In another implementation, when operating in a connected state, the UE receives the location information of the TN cell via one or more dedicated messages from the RAN. In some implementations, the location information includes GNSS coordinates. In such cases, each of the GNSS coordinates is associated with a specific TN cell.

[0110] In other implementations, while camped on one or more TN cells, the UE may obtain its GNSS coordinates using a GNSS receiver. For example, while camped on a TN cell, the UE may use its GNSS receiver to receive GNSS signals, derive GNSS coordinates, associate the GNSS coordinates with the TN cell, and store the GNSS coordinates and the cell ID of the TN cell in a memory. The cell ID may be a physical cell identifier.

[0111] Figure 25 An example method 2500 is shown that may be implemented by a UE (e.g., UE 102) for communicating with a RAN (e.g., RAN 105, base station 104, base station 106, or DU 174).

[0112] Method 2500 begins at block 2502, where the UE obtains location information, including one or more locations associated with one or more TN frequencies. At block 2504, the UE camps on an NTN cell of a base station. At block 2506, the UE determines whether the UE is near a location or within a location in the one or more locations. If, at block 2506, the UE determines that the UE is near a location or within a location in the one or more locations, the process proceeds to block 2508. At block 2508, the UE searches for TN cells on the TN frequency(ies) associated with the location. The UE may search for TN cells on the TN frequency(ies) while camped on the NTN cell. Otherwise, if, based on the location information, at block 2506, the UE determines that the UE is not near a location and / or is not within a location, the process proceeds to block 2510. At block 2510, the UE refrains from searching for TN cells. The UE may refrain from searching for TN cells while camped on an NTN cell.

[0113] In some implementations, while operating in a connected state (e.g., RRC_CONNECTED state), the UE receives location information from the core network via the RAN (e.g., a TN cell or an NTN cell (e.g., the NTN cell in block 2504 or another NTN cell)). The UE may receive one or more dedicated messages including the location information from the core network via the RAN. In other implementations, the UE receives the location information from the RAN. In one implementation, the UE receives the location information from the RAN via system information (e.g., event 704). In another implementation, while operating in a connected state, the UE receives the location information via one or more dedicated messages from the RAN. In some implementations, the location information includes GNSS coordinates. In such cases, each of the GNSS coordinates is associated with a specific TN frequency.

[0114] In other implementations, the UE may obtain GNSS coordinates by using a GNSS receiver while camping on one or more TN cells of the one or more frequencies. For example, when the UE is camped on a TN cell, the UE uses its GNSS receiver to receive GNSS signals, derives GNSS coordinates, associates the GNSS coordinates with a TN frequency of the TN cell, and stores the GNSS coordinates and an ID of the TN frequency in a memory. The ID may be an absolute radio frequency channel number (ARFCN).

[0115] The following description can be applied to the above description.

[0116] In general, the description of one figure in the above figures may apply to another figure in the above figures. If there is no conflict, the examples, implementations and methods described above may be combined. The events or boxes described above may be optional or may be omitted. For example, the events or boxes with dotted lines in the figures may be optional. In some implementations, "message" is used and "information element (IE)" can be used to replace "message", and vice versa. In some implementations, "IE" is used and "field" can be used to replace "IE", and vice versa. In some implementations, "configuration" or "configuration parameter" can be used to replace "configuration", and vice versa. In some implementations, "some" means "one or more". In some implementations, "at least one" means "one or more".

[0117] The user device (e.g., UE 102) in which the technology of the present disclosure may be implemented may be any suitable device capable of wireless communication, such as a smartphone, tablet computer, laptop computer, mobile game console, point of sale (POS) terminal, health monitoring device, drone, camera, media streaming dongle or another personal media device, wearable device such as a smart watch, wireless hotspot, femtocell (femtocell) or broadband router. Further, in some cases, the user device may be embedded in an electronic system such as a head unit of a vehicle or an advanced driver assistance system (ADAS). Further, the user device may operate as an Internet of Things (IoT) device or a mobile internet device (MID). Depending on the type, the user device may include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0118] Certain embodiments are described in this disclosure as including logic or multiple components or modules. A module can be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit that is capable of performing certain operations and can be configured or arranged in a certain manner. A hardware module can include dedicated circuitry or logic that is permanently configured (e.g., as a dedicated processor, such as a field programmable gate array (FPGA) or application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.) to perform certain operations. A hardware module can also include programmable logic or circuitry (e.g., as contained 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 a dedicated and permanently configured circuitry or in a temporarily configured circuitry (e.g., configured by software) can be driven by cost and time considerations.

[0119] When implemented in software, the techniques may be provided as part of an operating system, as a library used by multiple applications, as a specific software application, etc. The software may be executed by one or more general-purpose processors or one or more special-purpose processors.

[0120] Upon reading this disclosure, those skilled in the art will appreciate additional and alternative structural and functional designs for handling mobility between base stations using the principles disclosed herein. Thus, while specific embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the precise configurations and components disclosed herein. Various modifications, changes, and variations that will be apparent to those skilled in the art may be made to the arrangement, operation, and details of the methods and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.

Claims

1. A method for performing inter-frequency measurement, the method being implemented in a user equipment (UE) and comprising: receiving, via a non-terrestrial network (NTN) cell, one or more pairs of: (i) a terrestrial network (TN) frequency and (ii) a bitmap indication identifying one or more of a plurality of sectors of the NTN cell associated with the TN frequency; as well as Searching for a TN cell on the TN frequency only when the current location of the UE is within the one or more sectors of the plurality of sectors associated with the TN frequency according to the bitmap indication.

2. The method of claim 1, wherein: The bitmap indication includes N bits, each of the N bits corresponding to a respective one of the plurality of sectors of the NTN cell.

3. The method of claim 2, further comprising: The plurality of zones are determined by dividing the NTN cell into N sectors around a reference location of the NTN cell.

4. The method according to any one of claims 1 to 3, wherein the one or more pairs are received in a system information block (SIB).

5. The method of any one of claims 1 to 4, wherein searching for the TN cell on the TN frequency comprises performing longer inter-frequency measurements.

6. The method of claim 5, wherein the longer inter-frequency measurements have an increased duration for at least one of: (i) Tdetect,NR_Inter, (ii) Tmeasure,NR_Inter, or (iii) Tevaluate,NR_Inter, The above is specified in the 3GPP technical specifications for inter-frequency measurements for next-generation radio NR cells.

7. The method according to any one of claims 1 to 6, further comprising: sending an indication of the current location of the UE to a base station associated with the NTN cell, and receiving coverage information of the TN cell from the base station, The searching for the TN cell includes using the coverage information.

8. The method of claim 7, wherein: The sending of the indication comprises sending one of: (i) a request to resume a radio connection with the base station, (ii) an uplink UL dedicated control channel DCCH message, and (iii) an on-demand system information SI request, and The receiving the coverage information includes receiving one of: (i) a command to release the radio connection, (ii) a downlink (DL) DCCH message, and (iii) an SI message, respectively.

9. The method according to any one of claims 7 or 8, wherein the coverage information of the TN cell comprises one of the following: a reference position of the TN cell or a radius of the TN cell.

10. A method implemented in a base station associated with a non-terrestrial network (NTN) cell, for configuring inter-frequency measurements at a UE, the UE operating in the NTN cell, the method comprising: One or more pairs of: (i) a terrestrial network (TN) frequency and (ii) a bitmap indication identifying one or more of a plurality of segments of the NTN cell associated with the TN frequency are sent in the NTN cell to facilitate searching for TN cells on the TN frequency at the UE.

11. The method of claim 10, wherein the bitmap indication comprises N bits, each of the N bits corresponding to a respective one of the plurality of sectors of the NTN cell, the plurality of sectors being defined by dividing the NTN cell into N sectors around a reference position of the NTN cell.

12. The method according to any one of claims 10 or 11, wherein the one or more pairs are sent in a system information block (SIB).

13. The method of any one of claims 10 to 12, further comprising: receiving from the UE an indication of the current location of the UE, and Sending coverage information of a specific TN cell within one of the multiple sectors of the NTN cell where the UE is currently located according to the indication.

14. The method of claim 13, wherein: The receiving of the indication comprises receiving one of: (i) a request to resume a radio connection with the base station, (ii) an uplink UL dedicated control channel DCCH message, and (iii) an on-demand system information SI request, and The sending of the coverage information includes sending (i) a command to release the radio connection, (ii) a downlink (DL) DCCH message, and (iii) an SI message, respectively.

15. A method for performing inter-frequency measurement, the method being implemented in a user equipment (UE) and comprising: Receiving frequencies via non-terrestrial network NTN cells; Searching for cells on the frequency in a first time period; as well as In response to detecting a TN cell on the frequency, signals in the TN cell are measured for a second time period, wherein the first time period is longer than the second time period.

16. The method of claim 15, further comprising: In response to determining that the frequency is a TN frequency, the first time period for the search is selected.

17. The method of claim 16, wherein the determination is based on a system information block 19 (SIB19) transmission in the NTN cell, or based on an absolute radio frequency channel number (ARFCN) in SIB4.

18. An apparatus comprising: transceiver; and A processing component configured to perform the method of any one of claims 1 to 17 using the transceiver.

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