Access control for a user equipment in a non-terrestrial network

Abstract

A connection method implemented in a user equipment (UE) includes receiving information related to applying one or more access control parameters for accessing a target cell of a non-terrestrial network (NTN) (1302); performing, in the target cell, access control in accordance with the one or more access control parameters (1350); and transmitting an uplink message in the target cell in accordance with the access control (1370).

Description

ACCESS CONTROL FOR A USER EQUIPMENT IN A NON-TERRESTRIAL NETWORKREFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of the filing date of provisional U.S. Patent Application No. 63 / 616,655 entitled “Access Control for a User Equipment in a NonTerrestrial Network,” filed on December 31, 2023. The entire content of the provisional application is hereby expressly incorporated herein by reference.FIELD OF THE DISCLOSURE

[0002] This disclosure relates generally to wireless communication systems such as 3GPP communication systems and, more particularly, to accessing a cell in a non-terrestrial network (NTN).BACKGROUND

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

[0004] Generally speaking, a base station operating a cellular radio access network (RAN) communicates with a user equipment (UE) using a certain radio access technology (RAT) and multiple layers of a protocol stack. For example, the physical layer (PHY) of a RAT provides transport channels to the Medium Access Control (MAC) sublayer, which in turn provides logical channels to the Radio Link Control (RLC) sublayer, and the RLC sublayer in turn provides data transfer services to the Packet Data Convergence Protocol (PDCP) sublayer. The Radio Resource Control (RRC) sublayer is disposed above the PDCP sublayer.

[0005] The RRC sublayer specifies the RRC IDLE state, in which a UE does not have an active radio connection with a base station and does not store a UE access stratum (AS) context; the RRC CONNECTED state, in which the UE has an active radio connection with the basestation; and the RRC INACTIVE to allow a UE to more quickly transition back to the RRC_CONNECTED state due to Radio Access Network (RAN)-level base station coordination and RAN-paging procedures. Depending on different implementations or scenarios, the base station can configure Small Data Transmission (SDT) for the UE operating in the RRC INACTIVE to transmit one or more small packets.

[0006] The 5G technology relies primarily on legacy terrestrial networks. However, the 3rd Generation Partnership Project (3GPP) organization has proposed to extend 5G communications to non-terrestrial networks (NTNs) with 5G new radio (NR) technologies, or with the Long- Term -Evolution (LTE) technologies tailored for the Narrowband Internet-of-Thing (NB-IoT) or the enhanced Machine Type Communication (eMTC) scenarios. In an NTN, an RF transceiver is mounted on a satellite or an uncrewed aircraft system (UAS) or a crewed aircraft such as for example a drone, balloon, plane, or another suitable apparatus. For simplicity, the discussion below refers to all such apparatus as satellites. In addition to satellites, an NTN can include the sat-gateways that connect the Non-Terrestrial Network to a public data network, feeder links between sat-gateways and satellites, service links between satellites, and inter-satellite links (ISL) when satellites form constellations.

[0007] A satellite can belong to one of several types based on altitude, orbit, and beam footprint size. The types include Low-Earth Orbit (LEO) satellite, Medium-Earth Orbit (LEO) satellite, Geostationary Earth Orbit (GEO) satellite, UAS platform (including High Altitude Platform Station, HAPS), and High Elliptical Orbit (HEO) satellite. GEO satellites are also known as the Geosynchronous Orbit (GSO) satellites, and LEO / MEO satellites are also known as the non-GSO (NGSO) satellites.

[0008] A GSO satellite can communicate with one or several sat-gateways deployed over a satellite targeted coverage area (e.g. a region or even a continent). A non-GSO satellite at different times can communicate with one or several serving sat-gateways. An NTN is designed to ensure service and feeder link continuity between successive serving sat-gateways, with sufficient time duration to proceed with mobility anchoring and hand-over.

[0009] A satellite 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 regenerative payload implementation, a satellite 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 a base station, e.g., a gNB or an eNB.

[0010] NB-IoT and eMTC technologies are expected to be particularly suitable for loT devices operating in remote areas with limited or no terrestrial connectivity. Such loT devices can be used in a variety of industries including for example transportation (maritime, road, rail, air) and logistics; solar, oil, and gas harvesting; utilities; farming; environmental monitoring; and mining. However, to ensure the required loT connectivity, deployment of these technologies often use satellite connectivity to provide coverage beyond terrestrial deployments. Satellite NB-IoT or eMTC is defined in a complementary manner to terrestrial deployments.

[0011] One of the challenges for an NTN network with discontinuous coverage is reducing the impact of a large number of UEs initiating signalling with a target RAT substantially at the same time. As discussed in more detail below with reference to Figs. 5A-C, a large number of UEs can enter the area of NTN coverage of a certain satellite and attempt to access the network at the same time, generating an excessive amount of signalling that can cause the service to be degraded both for the UEs entering the area and those already operating in the area. Moreover, a similar problem can occur when a larger number of UEs leaves an area of NTN coverage and attempts to access the same cell of a terrestrial network.

[0012] Although certain access control mechanisms for moderating access attempts to a base station are available, none can properly address the scenarios discussed above. For example, EAB (Extended Access Barring) for MTC UEs and AB (Access Barring) mechanism for NB-IoT UEs are available for Evolved Packet System (EPS) networks, and a unified access control (UAC) mechanism is available for 5G system (5GS) networks. These mechanisms are noteffective when the network decides to elevating the level of access control to bar more UEs from access attempts, because the UEs entering the coverage can disperse in time but the UEs already receiving service in the satellite cell also encounter a higher probability of access attempt failure, which degrades service quality. Also, some UEs require access to the network only for sending a small amount of data. This data may be important for and generally is not burdensome for the network, and yet these UEs may fail to gain access to the network due to the elevated access control level.SUMMARY

[0013] An example embodiment of the techniques of this disclosure is a connection method implemented in a user equipment (UE). The method comprises receiving information related to applying one or more access control parameters for accessing a target cell of a non-terrestrial network (NTN); performing, in the target cell, access control in accordance with the one or more access control parameters; and transmitting an uplink message in the target cell in accordance with the access control. The use of "target cell" in this patent application encompasses cell reselection.

[0014] Another example embodiment of these techniques is a UE including a transceiver and configured to implement the method above.

[0015] Another example embodiment of these techniques is a method implemented in a core network (CN), the method for controlling access of a user equipment to a radio access network (RAN) and comprising: determining how the UE is to perform access control for accessing a cell of a non-terrestrial network (NTN); and providing, to the UE, information related to applying one or more access control parameters for accessing the cell of the NTN, based on the determining.

[0016] Another example embodiment of these techniques is a node in a core network (CN) configured to implement the method above.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Fig. 1 A is a block diagram of an example wireless communication system in which a user device and a base station of this disclosure can implement the access control techniques of this disclosure;

[0018] Fig. IB is a block diagram of an example base station in which a centralized unit (CU) and a distributed unit (DU) that can operate in the system of Fig. 1A;

[0019] Fig. 2A is a block diagram of an example protocol stack according to which the UE of Fig. 1A communicates with base stations;

[0020] Fig. 2B is a block diagram of an example protocol stack according to which the UE of Fig. 1 A communicates with a CU and a DU;

[0021] Fig. 3A is a block diagram of an example NTN node with transparent payload implementation;

[0022] Fig. 3B is a block diagram of an example NTN node with transparent payload implementation, in which a base station connects to multiple satellites via the same sat-gateway;

[0023] Fig. 4A illustrates an exemplary user plane protocol stack for use with the architecture of Fig. 3 A;

[0024] Fig. 4B illustrates an exemplary control plane protocol stack for use with the architecture of Fig. 3 A;

[0025] Fig. 5A illustrates an example scenario in which a UE has satellite coverage during certain time periods separated by intervals of non-coverage;

[0026] Fig. 5B illustrates an example scenario in which multiple UEs leave the area of coverage of an NTN cell and enter the area of coverage of a new NTN cell at the same time;

[0027] Fig. 5C illustrates an example scenario in which multiple UEs leave the area of coverage of an NTN cell and enter the area of coverage of a new terrestrial cell at the same time;

[0028] Fig. 6 illustrates an example scenario in which a UE receives, prior to leaving the area of NTN coverage, one or more access control parameters for accessing a target NTN cell;

[0029] Fig. 7 illustrates an example scenario in which a UE receives, prior to leaving the area of NTN coverage, an indication that the UE should override the access control parameters the target NTN cell broadcasts;

[0030] Fig. 8 illustrates an example scenario in which a UE determines which access control parameters it should be used based on access identity;

[0031] Fig. 9A is a flow diagram of an example method for selecting access control parameter(s) for NTN access based on a cell identifier, which can be implemented in the UE of Fig- 1A;

[0032] Fig. 9B is a flow diagram of an example method for overriding access control parameter(s) for NTN access, which can be implemented in the UE of Fig. 1A;

[0033] Fig. 10 is a flow diagram of an example method for configuring a UE with access control parameter(s) for NTN access, which can be implemented in the CN of Fig. 1 A;

[0034] Fig. 11 is a flow diagram of an example method for configuring a UE with an override indication for access control to an NTN cell, which can be implemented in the CN of Fig. 1A;

[0035] Fig. 12 is a flow diagram of an example method for selecting access control parameters in view of access identity, which can be implemented in the UE of Fig. 1A;

[0036] Fig. 13 is a flow diagram of an example connection method, which can be implemented in the UE of Fig. 1A; and

[0037] Fig. 14 is a flow diagram of an example configuration method, which can be implemented in the CN of Fig. 1A.DETAILED DESCRIPTION OF THE DRAWINGS

[0038] Generally speaking, a user equipment (UE) can use the techniques of this disclosure for managing access control for an NTN cell, and a core network can use these techniques for configuring a UE for access control, when the UE accesses an NTN cell. More generally, a UE and / or a CN can apply these techniques for controlling access to a cell in situations where a large number of UEs may attempt access at the same time, e.g., when entering an area of coverage ofan NTN cell or when entering an area of coverage of a terrestrial cell after leaving the area of coverage of an NTN.

[0039] Referring first to Fig. 1A, an example wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. The base stations 104 and 106 can operate in a RAN 105 connected to the core network (CN) 110. The CN 110 can be implemented as an evolved packet core (EPC) 111 or a fifth generation (5G) core (5GC) 160, for example. The CN 110 can also be implemented as a sixth generation (6G) core in another example.

[0040] The base station 104 covers a cell 124, and the base station 106 covers a cell 126. If the base station 104 is a gNB, the cell 124 is an NR cell. If the base station 104 is an ng-eNB or eNB, the cell 124 is an evolved universal terrestrial radio access (E-UTRA) cell. Similarly, if the base station 106 is a gNB, the cell 126 is an NR cell, and if the base station 106 is an ng-eNB or eNB, the cell 126 is an E-UTRA cell. The cells 124 and 126 can be in the same Radio Access Network Notification Areas (RNA) or different RNAs. In general, the RAN 105 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 104 and 106. Each of the base stations 104, 106 can connect to the CN 110 via an interface (e.g., SI or NG interface). The base stations 104 and 106 also can be interconnected via an interface (e.g., X2 or Xn interface) for interconnecting NG RAN nodes.

[0041] Among other components, the EPC 111 can include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. The SGW 112 in general is configured to transfer user-plane packets related to audio calls, video calls, Internet traffic, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The 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. The 5GC 160 includes a User Plane Function (UPF) 162 and an Access and Mobility Management Function (AMF) 164, and / or Session Management Function (SMF) 166. Generally speaking, the UPF 162 is configured to transfer user-planepackets related to audio calls, video calls, Internet traffic, etc., the AMF 164 is configured to manage authentication, registration, paging, and other related functions, and the SMF 166 is configured to manage PDU sessions.

[0042] As illustrated in Fig. 1A, the base station 104 supports a cell 124, and the base station 106 supports a cell 126. The cells 124 and 126 can partially overlap, so that the UE 102 can select, reselect, or hand over from one of the cells 124 and 126 to the other. To directly exchange messages or information, the base station 104 and base station 106 can support an X2 or Xn interface. In general, the CN 110 can connect to any suitable number of base stations supporting NR cells and / or EUTRA cells.

[0043] As discussed in detail below, the UE 102 and / or the RAN 105 may utilize the techniques of this disclosure when the radio connection between the UE 102 and the RAN 105 is suspended, e.g., when the UE 102 operates in an inactive or idle state of the 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 state of the RRC protocol.

[0044] The base station 104 is equipped with processing hardware 130 that can include one or more general -purpose processors (e.g., CPUs) and a non-transitory computer-readable memory storing instructions that the one or more general-purpose processors execute. Additionally or alternatively, the processing hardware 130 can include special -purpose processing units. The processing hardware 130 in an example implementation includes a processor 132 to process data that the base station 104 will transmit in the downlink direction, or process data received by the base station 104 in the uplink direction. The processing hardware 130 can also include a transmitter 136 configured to transmit data in the downlink direction. The processing hardware further can include a receiver 134 configured to receive data in the uplink direction. The processing hardware further can include an RRC controller 138 to implement procedures and messaging at the RRC sublayer of the protocol communication stack. The base station 106 can include generally similar components. In particular, components 140, 142, 144,146, and 148 of the base station 106 can be similar to the components 130, 132, 134, 136, and 138 respectively.

[0045] The UE 102 is equipped with processing hardware 150 that can include one or more general -purpose processors such as CPUs and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. The processing hardware 150 in an example implementation includes a processor 152 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 processing hardware 150 can also include a transmitter 156 configured to transmit data in the downlink direction. The processing hardware further can include a receiver 154 configured to receive data in the uplink direction. The processing hardware further can include an RRC controller 158 to implement procedures and messaging at the RRC sublayer of the protocol communication stack.

[0046] Fig. IB depicts an example distributed or disaggregated implementation of any one or more of the base stations 104, 106. In this implementation, the base station 104, 106 includes a central unit (CU) 172 and one or more distributed units (DUs) 174. The CU 172 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 172 can include a PDCP controller, an RRC controller and / or an RRC inactive controller. In some implementations, the CU 172 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 172 does not include an RLC controller.

[0047] Each of the DUs 174 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 specialpurpose 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.

[0048] In some embodiments, the RAN 105 supports Integrated Access and Backhaul (IAB) functionality. In some implementations, the DU 174 operates as an lAB-node, and the CU 172 operates as an lAB-donor. In some embodiments, the RAN 105 supports Non-Terrestrial Network (NTN) functionality.

[0049] In some implementations, the CU 172 can include a logical node CU-CP 172A that hosts the control plane part of the PDCP protocol of the CU 172. The CU 172 can also include logical node(s) CU-UP 172B that hosts the user plane part of the PDCP protocol and / or Service Data Adaptation Protocol (SDAP) protocol of the CU 172. The CU-CP 172A can transmit control information (e.g., RRC messages, Fl application protocol messages), and the CU-UP 172B can transmit the data packets (e.g., SDAP PDUs or Internet Protocol packets).

[0050] The CU-CP 172A can be connected to multiple CU-UP 172B through the El interface. The CU-CP 172A selects the appropriate CU-UP 172B for the requested services for the UE 102. In some implementations, a single CU-UP 172B can connect to multiple CU-CP 172A through the El interface. The CU-CP 172A can connect to one or more DU 174s through an Fl-C interface. The CU-UP 172B can connect to one or more DU 174 through the Fl-U interface under the control of the same CU-CP 172A. In some implementations, one DU 174 can connect to multiple CU-UP 172B under the control of the same CU-CP 172A. In such implementations, the connectivity between a CU-UP 172B and a DU 174 is established by the CU-CP 172A using Bearer Context Management functions.

[0051] Fig. 2A illustrates, in a simplified manner, an example protocol stack 200 according to which the UE 102 can communicate with an eNB / ng-eNB or a gNB (e g., one or more of the base stations 104, 106).

[0052] In the example stack 200, a physical layer (PHY) 202A of EUTRA provides transport channels to the EUTRA MAC sublayer 204A, which in turn provides logical channels to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A in turn provides RLC channels to an EUTRA PDCP sublayer 208 and, in some cases, to an NR PDCP sublayer 210. Similarly, the NR PHY 202B provides transport channels to the NR MAC sublayer 204B, which in turn provides logical channels to the NR RLC sublayer 206B. The NR RLC sublayer 206B in turnprovides data transfer services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 in turn can provide data transfer services to Service Data Adaptation Protocol (SDAP) 212 or a radio resource control (RRC) sublayer (not shown in Fig. 2A). The UE 102, in some implementations, supports both the EUTRA and the NR stack as shown in Fig. 2A, to support handover between EUTRA and NR base stations and / or to support DC over EUTRA and NR interfaces. Further, as illustrated in Fig. 2A, the UE 102 can support layering of NR PDCP 210 over EUTRA RLC 206A, and SDAP sublayer 212 over the NR PDCP sublayer 210.

[0053] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets (e.g., from an Internet Protocol (IP) layer, layered directly or indirectly over the PDCP layer 208 or 210) that can be referred to as service data units (SDUs), and output packets (e.g., to the RLC layer 206A or 206B) 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.”

[0054] On a control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 can provide signaling radio bearers (SRBs) or RRC sublayer (not shown in Fig. 2A) to exchange RRC messages or non-access-stratum (NAS) messages, for example. On a user plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 can provide Data Radio Bearers (DRBs) to support data exchange. Data exchanged on the NR PDCP sublayer 210 can be SDAP PDUs, Internet Protocol (IP) packets or Ethernet packets.

[0055] Fig. 2B illustrates, in a simplified manner, an example protocol stack 250, which the UE 102 can communicate with a DU (e g., DU 174) and a CU (e.g., CU 172). The radio protocol stack 200 is functionally split as shown by the radio protocol stack 250 in Fig. 2B. The CU at any of the base stations 104 or 106 can hold all the control and upper layer functionalities (e.g., RRC 214, SDAP 212, NR PDCP 210), while the lower layer operations (e.g., NR RLC 206B, NR MAC 204B, and NR PHY 202B) are delegated to the DU. To support connection to a 5GC, NR PDCP 210 provides SRBs to RRC 214, and NR PDCP 210 provides DRBs to SDAP 212 and SRBs to RRC 214.

[0056] Fig. 3A illustrates a certain type of NTN deployment referred to as transparent payload architecture, which involves a satellite gateway 302 and a “transparent” satellite 304 for extending the range of the Uu interface. The satellite 304 implements a frequency conversion and a Radio Frequency (RF) amplifier in both the uplink and downlink directions. The satellite function is similar to that of an analogue RF repeater. As a result, the satellite 304 repeats the Uu radio interface from the feeder link (between the NTN gateway and the satellite) to the service 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 the Uu, and the NTN gateway 302 supports all necessary functions to forward the signal of the Uu interface. The NTN gateway 302 can be placed at the same site as the base station (e.g., eNB, gNB) 104 location, or be connected to the base station 104 at a distance via a wired link. It is also possible to connect more than one NTN gateway to a base station. Different transparent satellites may be connected to the same base station on the ground, via the same NTN gateway, or via different NTN gateways. Fig. 3B illustrates the case where two different satellites (304 and 306) are connected to the same base station 104 via the same NTN gateway 302, and these two satellites (304 and 306) are covering the Earth surface using two different Physical Cell IDs (PCIs).

[0057] The NTN user plane protocol stack involving the UE 102, satellite 304, NTN gateway 302, the BS 104 and the S-GW 114 is illustrated in Fig. 4A. The diagram of the NTN user plane protocol stack is similar to that of the terrestrial network (TN), with the addition of two new nodes, the satellite 304 and the NTN gateway 302, being placed in the middle of the Uu interface. Similarly, the NTN control plane protocol stack illustrated in Fig. 4B is also similar to that of the terrestrial network.

[0058] In terms of the satellite moving pattern, there are three types of service links that are supported in NTN:• Earth-fixed: provisioned by beam(s) continuously covering the same geographical areas all the time (e.g., the case of GEO / GSO satellites)• Quasi -Earth-fixed: 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)• Earth-moving: 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).

[0059] With LEO / MEO satellites, the eNB can provide either quasi-Earth-fixed cell coverage or Earth-moving cell coverage. With GEO satellites, the eNB can provide Earth fixed cell coverage.

[0060] Although the transparent payload architecture illustrated in Figs. 3A / 3B is the current focus of the 3GPP development, the regenerative payload architecture that installs the eNB functions on the satellite is also a possible NTN deployment in the future. In such an architecture, the Uu only exists between the satellite and the UE. In general, the techniques of this disclosure can apply to the transparent payload architecture as well as the regenerative payload architecture.

[0061] Fig. 5 A illustrates an example scenario 500 in which the UE 102 located in the concerned geographical area may experience a situation of discontinuous coverage, due to e.g. a sparse satellites constellation deployment. In the scenario, the UE 102 is served by the LEO satellite 304 from tl to t2, and served by another LEO satellite 306 from t3 to t4. In the period between t2 to t3, the UE 102 is not served by any satellite or any terrestrial base station and therefore is out of coverage. Typically, when a UE loses coverage by a serving cell, the UE starts searching for other cells and then camps on a suitable cell. However, in the example illustrated in Fig. 5, even if the UE 102 starts searching for other cells immediately after t2, the UE 102 cannot find a cell. The cell search lasts for a long time as the time period between t2 to t3 can vary from tens of minutes to hours. Therefore the cell search causes extra, unnecessary power consumption in the UE 102. To reduce power consumption at the UE in particular NTN scenarios such as the one depicted in Fig. 5, the UE may not be required to perform the cell search and can deactivate the Access Stratum (AS) functions during the period when the UE is not within the area of coverage of a satellite. In some implementations, the UE has knowledge of when the UE will be outside the area of coverage, and when the UE will be within an area of coverage again, in order to activate its cell search or AS functions again before the UE falls into the coverage of another NTN cell. For example, the ephemeris information broadcasted in the system information provides the constellation and trajectory / movement information of theserving and the neighboring satellites, which helps UE to predict / estimate when it will be within and when it will be outside the NTN coverage. In addition to the ephemeris information, the UE may use other information to estimate / predict coverage of a NTN cell more precisely.

[0062] In some scenarios, the UE 102 in a connected state (e.g., RRC CONNECTED state) communicates with a RAN via the satellite 304 and detects radio link failure on the service link with the satellite 304 because the UE 102 is out of coverage of the satellite 304, e.g., in the period between t2 to t3. In response to the radio link failure, the UE 102 initiates a RRC connection reestablishment procedure, e.g., in accordance with 3GPP specification 38.331.

[0063] As illustrated in Fig. 5B, an example scenario 500B can be a problem due to a signaling overload caused by multiple UEs in the NTN with discontinuous coverage. Multiple UEs including the UE 102A and the UE 102B are registered to a PLMN using NTN radio access technology with discontinuous coverage. At tl, the UE 102A and UE 102B are in the coverage are of the satellite 304. These UEs then move out of the area of NTN coverage associated with the satellite 304. At t2, both UEs are back within an area of NTN coverage of the satellite 306, and both attempt to access the network via the satellite 306. If the number of such UEs is large, an excessive large number of access attempts are initiated for the satellite 306, which may degrade the service quality for the satellite 306. This problem can apply not only to those UEs that attempt access but also for the UEs already receiving service from the satellite 306. In an extreme case, the satellite 306 suffers from the signaling overload and breaks down.

[0064] Referring to Fig. 5C, this scenario is similar to the scenario 500B, but here h multiple UEs enter a TN (terrestrial network) cell of the base station 104 or 106 rather than a new NTN cell of the satellite 306. For example, multiple UEs located in the area of coverage of the satellite 304 can lose coverage due to the trajectory of the satellite. When the satellite 304 moves out of the area while the multiple UEs are stationary in the area, those UEs may search for available cell substantially at the same time. When a TN cell coverage is available, these UEs attempt to access the network via the TN cell. If the number of the UEs is large, a large number of access attempts are initiated for a base station 104 or 106, which degrades the service quality for the base station 104 or 106, both for the UEs attempting access and for the UEs alreadyreceiving service from the base station 104 or 106. Similar to the satellites of Fig. 5B, the base station 104 or 106 may suffer from a signaling overload and potentially even break down.

[0065] Next, several example scenarios that involve several components of Fig. 1 A and relate to detecting out of coverage in an inactive or connected state are discussed next with reference to Figs. 6-7. Generally speaking, similar events in Figs. 6-7 are labeled with the similar reference numbers (e.g., event 602 in Fig. 6 is similar to event 702 in Figs. 7), with differences discussed below where appropriate. With the exception of the differences shown in the figures and discussed below, any of the alternative implementations discussed with respect to a particular event (e.g., for messaging and processing) may apply to events labeled with similar reference numbers in other figures and also to both integrated and distributed base stations.

[0066] In the discussion of Figs. 6-14 below, the term "target cell" generally refers to a cell in which a UE attempts to register or in which the UE is likely to attempt to register in the future, and some cases encompasses cell reselection.

[0067] Referring first to Fig. 6, the base station 104 of the RAN 105 includes a satellite 304 and a satellite 306. In example scenario 600, the UE 102 initially operates 602 in the area of coverage of the satellite 304. The UE 102 operates 604 in a connected state (e.g., ECM- CONNECTED or EMM-CONNECTED for EPS implementations, or 5GCM-CONNECTED or 5GMM-CONNECTED for 5GS implementations) and is registered to a PLMN with a node of the CN 110. The node can be the MME 114 or the AMF 164 (see Fig. 1A), for example. For simplicity, the techniques below are discussed with reference to the CN 110 rather than a particular node of the CN 110.

[0068] Due to the mobility of the satellite 304, the UE 102, or both, the CN 110 detects 610 that the UE 102 is about to leave the area of coverage of the satellite 304. In some implementations, the CN 110 also receives information related to the actual or potential overload status of each the base station 104, 106.

[0069] The CN 110 can determine 612 one or more access control parameters for the UE 102 to apply upon entering the area of coverage of a neighboring cell of satellite 304. The CN 110 can make this determination using one or more of such factors as actual or potential overloadinformation for the base station 104, the number of UEs the satellite 304 currently serves, the number of UEs the neighboring cell of the satellite 306 currently serves, and the estimation of mobility of the UE 102. For example, if the CN 110 estimates that the UE 102 is moving out of the areas of coverage of the satellite 304 and is moving into the area of coverage of the satellite 306, and determines that the satellite 306 currently is serving a large number of UEs (e.g., JES >7UES, where AUES is the number of UEs and TUES is a pre-defined threshold), the CN 110 can select 612 more “strict” access control parameters for the UE 102, even though the UE 102 has not yet reached the target NTN.

[0070] As used in this disclosure, the term “strict” value refers to a value that yields a higher probability of barring the UE 102 from accessing the cell after performing the access control check. For example, if the access control mechanism the UE 102 applies is unified access control (UAC) for the 5GS, a strict value corresponds to a higher barring factor probability and / or a longer barring time value. As another example, if the access control mechanism the UE 102 applies is Extended Access Barring (EAB) for EPS, a strict value corresponds to the barring bitmap for the corresponding EAB category barring more access classes.

[0071] In some implementations, the one or more access control parameters the CN 110 determines 612 contain specific parameters for the corresponding access control mechanism. For example, if the access control mechanism is UAC, the specific parameters are the barring factor and the barring time for each of the access categories corresponding to the specific access identity.

[0072] In some implementations, the CN 110 and the UE 102 use access identity dedicated specifically to using NTN (e.g., satellite) access. The CN 110 can use this access identity to indicate UAC parameters for the UEs accessing the network via NTN cells. As a more specific example, the access identity for NTN can augment the listing of access identities in 3GPP TS 22.261, as Access Identity Number 4, in Table 1 below:Table 1

[0073] When the CN 110 and the UE 102 use the access identity for NTN, the NAS layer in the UE 102 can indicate this access identity along with the access category when the UE 102 attempts to access the network in the idle state, when the UE camps on a cell of an NTN.

[0074] In another implementation, an entity other than the CN 110 determines 610 that the UE leaves 610 NTN coverage 610, and then determines 612 the access control parameters. This entity can be for example an Operations And Maintenance (0AM) function or another third- party function.

[0075] The CN 110 can transmit 620 a DL (downlink) NAS message including the one or more access control parameters, based on the determining 612 of the access control parameters. Depending on the implementation and / or scenario, the DL NAS message 620 is an ATTACH ACCEPT message, a TRACKING AREA UPDATE ACCEPT message, a SERVICE ACCEPT message, a GUTI REALLOCATION COMMAND message, a REGISTRATION ACCEPT message, or a CONFIGURATION UPDATE COMMAND message.

[0076] In some implementations, the access control parameters include specific values for corresponding access control mechanism the CN 110 determined 612, with the relevant access control mechanism type information. The access control parameters optionally include the cell identifier(s) of a cell of the satellite to which the access control parameters are applied, and an indication of whether the UE 102 is to apply the corresponding value one time or continuously.

[0077] For example, if the one or more access control parameters include a certain cell identifier, or the CN 110 otherwise associates the access control parameter(s) with the certain cell identifier, the UE 102 applies the access control parameter(s) instead of the value the target NTN cell broadcasts only when the certain cell identifier matches the identifier of the satellite cell. In another implementation, the CN 110 provides access control param eter(s) to the UE 102 for any cell that is an NTN cell (or, more specifically, a satellite cell), without restricting the cell to any specific cell identifier. If the CN 110 omits the cell identifier(s), the UE 102 applies the received value in any NTN cell the UE enters after it leaves the area of coverage of the satellite 304. The CN 110 in some implementations includes an additional indication that the provided value is for application in any cell that is an NTN cell, e.g., a cell with the RAT type corresponding to satellite access.

[0078] As another example, when the CN 110 includes an indication that the UE 102 should apply the access control parameter(s) continuously (e.g., by including a certain flag or setting a certain indicator to “1”), the UE 102 applies the access control param eter(s) rather than the parameters included in the broadcast in the next NTN cell. When CN 110 omits the flag or sets the indicator to “0” for example, the UE 102 applies the received access control param eter(s) only in the first access attempt after the UE 102 enters a new area of NTN coverage. To continue with this example, when the CN 110 omits this indication when providing 620 theaccess control param eter(s), and the UE 102 leaves 630 the area of coverage of the satellite 304 and enters the area of coverage of the satellite 306, the UE 102 applies the received 620 access control parameter(s) when performing an access control check during the first attempt to access the target cell of the satellite 306. Regardless of whether the access control check is successful, the UE 102 no longer applies the received 620 access control parameter(s), starting with the second access attempt, and instead uses the parameters which the satellite 306 broadcasts 640 in the target cell via an RRC broadcast message or another suitable .

[0079] In some implementations, the CN 110 provides the access control parameter(s) as a separate information element in a DL NAS message, which can be dedicated to conveying access control param eter(s). In other implementations, the CN 110 includes the access control parameter(s) as part of the information for discontinuous coverage or satellite communications in a DL NAS message, e.g., using an IE dedicated to conveying discontinuous coverage information.

[0080] With continued reference to Fig. 6, the UE 102 in other implementations can obtain 625 pre-configured access control parameter(s) without receiving 620 the access control parameter(s) from the CN 110. The UE 102 can select 625 these pre-configured access control parameter(s) in response to determining that the access type is a satellite access. In some implementations, the pre-configured value resides in a USIM file. In other implementations, the UE 102 receives the pre-configured value via NAS MO. In still other implementations, the UE 102 stores the-configured value in an non-volatile memory (NVM) of the UE 102.

[0081] If the UE 102 both receives access 620 access control parameter(s) and retrieves 625 pre-configured access control parameter(s) from a local memory, the UE 102 can prioritize these sets relative to each other in any desired manner, to the extent that these parameters are different. Thus, in some implementation, the UE 102 applies the received 620 access control param eter(s), and in other implementations the UE 102 applies the retrieved 625 access control parameter(s).

[0082] After the UE 102 leaves 630 the areas of coverage of the satellite 304 and enters 632 the idle state, the UE 102 enters another area of NTN coverage of the same constellation, e.g. the area of an NTN cell of the satellite 306. The UE 102 receives 640 information related to the newcell via an RRC Broadcast message, which can vary according to the access control mechanism the UE 102 uses. For example, if the UE 102 is an NB-IoT UE, the corresponding broadcast message can be SystemInformationBlockTypel4-NB. If the UE 102 is a “normal” (regular) 5G UE, the corresponding broadcast message can be SystemInformationBlockType25.

[0083] If the UE 102 attempts to access the network via the cell of the satellite 306, the UE102 first determines 650 which access control parameters the UE 102 should use for the access control check. If the UE 102 received access control parameters in the DL NAS message 620 from the CN node 110, the UE 102 checks 650 whether the cell identity in the received information matches the current cell identifier, i.e., the cell identifier of the cell of the satellite 306. If the UE 102 did not receive 620 the matching cell identifier as a part of the DL NAS message, the UE 102 applies 652 the parameters the UE 102 received 640 in the RRC broadcast message. However, if the UE received 620 the matching cell identifier as a part of the DL NAS message, the UE 102 applies 652 the parameters the UE 102 received 620 in the DL NAS message.

[0084] If the CN 110 also indicated that the UE 102 should apply the access control parameters from the DL NAs message continuously (e.g., by including a certain flag or setting the appropriate indicator to “1” as discussed above), the UE 102 continues to apply the access control parameters received 620 in the DL NAS message 620 instead of broadcasted parameters included 640 in RRC broadcast, as long as the UE 102 remains in the area of coverage of the satellite 306. On the other hand, if the CN 110 omitted this indication (e.g., by omitting the certain flag or setting the appropriate indicator to “0” as discussed above), the UE 102 applies 652 the access control parameters in the DL NAS message instead of the broadcasted parameters only during the first attempt, after the UE 102 enters the area of coverage of the satellite 306. The UE 102 in this case may set a flag internally to manage the application of the received access control parameters, or the UE 102 may remove the received parameters after the first access attempt.

[0085] In other implementations, when the UE 102 stores pre-configured access control parameters for application in NTN cells, the UE 102 omits the cell identifier checking 650 andapplies the pre-configured parameters upon determining that the cell of the satellite 306 is an NTN cell.

[0086] In some implementations, the NAS layer of the UE 102 rather than the RRC layer of the UE 102 performs 652 the access control check using the received 620 access control parameters. In this case, the initial NAS message can bypass the access control check at the RRC layer in order to avoid double barring. In other implementations, the NAS layer provides the received access control parameters to the RRC layer, and the RRC layer then performs 652 the access control check using the existing mechanisms. For example, if the UE 102 is a 5G UE that implements UAC as an access control mechanism, the NAS layer provides the received UAC parameters to the RRC layer upon receiving 620 the DL NAS message. Subsequently, when the UE 102 enters the area of coverage of the satellite 306, the NAS layer provides access identity and access category of the access attempt to the RRC layer, and the RRC layer notifies the NAS layer of the result of performing 652 the access control check.

[0087] If the UE 102 passes the access control check, i.e., determines that the UE 102 is not barred from an attempt to register, the UE 102 transmits 670 UL NAS message and, in the scenario 600, successfully transitions 672 to a connected state.

[0088] At a later time, or if the UE 102 fails to pass the access control check (i.e., determines that the UE 102 is barred from attempting registration), the UE 102 operates 680 in an idle state and, at least in some cases, again attempts to access the network via the satellite 306. Depending on whether the CN 110 indicated 620 that the access control parameter(s) in the DL NAS message are for continuous application, the UE 102 applies the parameter(s) in the DL NAS message, to perform 690 a DL NAS-based access control check procedure, or in the RRC broadcast message, to perform 692 a broadcast-based access control check procedure.

[0089] Now referring to Fig. 7, an example scenario 700 is generally similar to the scenario 600 of Fig. 6, with the differences discussed below. Events that are similar in these figures are labeled with reference numbers that have the same lower-order digits (e.g., event 702 is similar to event 602, and event 730 is similar to event 630), and are not discussed in detail. However, the discussion of events with reference to Fig. 6 applies to the similar events below.

[0090] Generally speaking, here the CN 110 and / or a pre-stored indication allows the UE 102 to override access control settings entirely and attempt accessing an NTN cell regardless of access control check. This implementation can be particularly useful when, for example, the UE 102 is an loT or MTC device that reports critical data such as seismic readings or an emergency communication from a ship.

[0091] The CN 110 determines 714 that access control for the satellite cells with a severe overload status or with a high number of the UEs should be more strict. For example, if the overload level is high (e.g., exceeds a predefined threshold) in a specific satellite cell, e.g. the cell of the satellite 306, the CN 110 can configure the access control parameter(s) so as to prevent more UEs from attempting access. More particularly, the CN 110 can configure a higher barring rate and a longer barring time. The CN 110 can determine 714 whether the UE 102 needs to override the current access control mechanism and / or parameters in view of the type of the UE 102, the overload status of the base station, and the number of UEs receiving service in the neighboring satellite cells. For example, if the UE 102 is an NB-IoT UE that needs to transmit or receive a small amount data only once per a relatively period of time, the CN 110 can determine that the UE 102 should override its access control setting if the UE 102 currently is barred from access.

[0092] In some scenarios, the CN 110 allows 714 the UE 102 to override the access control based on the type of the UE 102, e.g., an loT UE, an MTC UE, a high-priority UE. In other implementations, the CN 110 allows 714 the UE 102 to override the access control based on the subscription or the operator’s policy.

[0093] After the determination 714, the CN node 110 transmits 722 a DL NAS message including an indication that the UE 102 must, or (in another implementation) is allowed to, override access control. Similar to the DL NAS message of the event 620, the DL NAS message of the event 722 can be an ATTACH ACCEPT message, a TRACKING AREA UPDATE ACCEPT message, a SERVICE ACCEPT message, a GUTI REALLOCATION COMMAND message, a REGISTRATION ACCEPT message, or a CONFIGURATION UPDATE COMMAND message.

[0094] In other implementations, the UE 102 is pre-configured 726 for overriding access control. Generally similar to one of the alternative implementations discussed in connection with the event 625 above, the UE 102 can a pre-configured indication that the UE 102 must, or is allowed to, override access control settings of a broadcast message when accessing an NTN cell in a file in USIM, store the indication in the local memory, or obtain the override indication in a NAS MO.

[0095] After receiving 742 information related to the new cell via an RRC Broadcast message, the UE 102 performs 753 access control check at the RRC layer. The UE 102 can use the known access control techniques, for example. If the UE 102 passes the access control check, the UE 102 transmits 770 UL NAS message and transitions 772 to the connected state. If the UE 102 fails to pass 753 the access control check, the UE 102 determines 755 whether the UE 102 previously received or retrieved from a local memory an indication for overriding access control. If the UE 102 received or retrieved this indication, the UE 102 can again attempt to access the network, bypassing 755 access control. In other implementations, the UE 102 can omit the checking 753 and proceed directly to overriding 755 access control. The UE 102 then transmits 770 UL NAS message and transitions to a connected state 772.

[0096] Referring to Fig. 8, an example scenario 800 is generally similar to the scenario 600 of Fig. 6, with the differences discussed below. Events that are similar in these figures are labeled with reference numbers that have the same lower-order digits (e g., event 802 is similar to event 602, and event 830 is similar to event 630), and are not discussed in detail. However, the discussion of events with reference to Fig. 6 applies to the similar events below.

[0097] In this scenario, the UE 102 initially operates 802 in an area of coverage of the satellite 304. Due to the mobility of the satellite 304, the mobility of the UE 102, or both, the UE 102 leaves 830 the NTN coverage of the satellite 304 and enters 832 the idle state.

[0098] At a later time, the UE 102 enters another area of NTN coverage of the same constellation, e.g. the area of coverage of an NTN cell of the satellite 306. The UE 102 receives information 842A related to the new NTN cell in an RRC Broadcast message, which can include an SystemlnformationBlockType 14-NB message or a SystemInformationBlockType25 similar tothe event 742. The BS 104 can broadcast 842A, in the RRC Broadcast message, both access barring information for UEs entering the area of coverage and access barring information for UEs remaining in the area of coverage.

[0099] Similar to the scenario 600, a certain access identity related to NTN access can augment the listing of access identities in 3GPP TS 22.261, as Access Identity Number 4 illustrated in Table 2 below. Here, however, this access identity relates more specifically for access control parameters for UEs re-gaining coverage in a certain NTN cell, or for UEs entering a new area of satellite NTN , rather than UEs remaining in the area of NTN coverage.Table 2

[0100] Access identity #4 in Table 2 applies only when the UE 102 enters a new area of NTN coverage, i.e., for the first access attempt in the current area of NTN coverage. In some implementations, the area of NTN coverage is an NTN cell, such as a satellite cell, that is distinguishable by its cell identifier. In other implementations, the area of NTN coverage is a tracking area that a satellite covers. For the second or further attempts within the same area of NTN coverage, the UE 102 uses access identities other than access identity #4 in the example above, e.g., access identity #0.

[0101] If the UE 102 attempts to access the network via the cell of the satellite 306, the UE 102 can perform 856A an access control check at the RRC layer using the existing access control mechanisms, for example. If the area of NTN coverage is different from the previous attempt, the UE 102 determines to use the access identity defined specifically for UEs entering a new area of NTN coverage, for this access attempt. The UE 102 applies 856A the corresponding access barring parameters for this access identity, which the UE 102 can receive 842A in the RRC broadcast message or, in another implementation (see FIG. 6 element 625), retrieve from the USIM or another type of storage local to the UE 102.

[0102] Further, the UE 102 can set 857, to a certain value, an internal flag for checking applicability of the access identity defined specifically to UEs entering a new area of NTN coverage, such as access identity #4 in Table 2 above. In this manner, the UE 102 can maintain an indication that the first access attempt within the satellite area has occurred. Another value of the internal flag can indicate that the first access attempt in the new area of NTN coverage has not yet happened, when the UE 102 leaves the current area of NTN coverage or when the UE 102 enters a new area of NTN coverage. In some implementations, the UE 102 determines to enter a new area of NTN coverage by comparing the cell identifier associated with this access attempt to the cell identifier associated with the previous attempt. In other implementations, the UE 102 determines to enter a new area of NTN coverage by comparing the tracking area identifier (TAI) associated with this access attempt with the TAI associated with the previous attempt.

[0103] At a later time, the UE 102 enters 840 idle mode and attempts to access the CN 110 via the same satellite 306. Because the UE 102 in this case remains in the same satellite area, the UE 102 determines to use access identity other than the access identity defined for UEs entering a new area of NTN coverage. The UE 102 retrieves access control parameters corresponding to this access identity from the received 842B RRC broadcast message (or a local storage) and applies 858 the access control parameters, such as the barring factor.

[0104] Due to the mobility of the satellite 306, the mobility of the UE 102, or both, the UE 102 leaves 833 the area of NTN coverage of the satellite 306 and again enters 843 the idle state. At a later time, the UE 102 enters another area of NTN coverage of the same constellation, e g.,the NTN cell of the satellite 304. The UE 102 receives 845 an RRC Broadcast message. When the UE 102 determines that the area of NTN coverage associated with this access attempt is different from the area of NTN coverage associated with the previous attempt, the UE 102 determines that it should again use the access identity defined for UEs entering a new area of NTN coverage (e.g., access identity #4 in Table 2), and performs 856B an access control check using the corresponding access control parameter(s).

[0105] Next, several example methods that can be implemented in a UE (e.g., the UE 102) or a CN (e.g., the CN 110) are discussed with reference to Figs. 9-14. Each of these methods can be implemented using processing hardware such as one or more processors configured to execute instructions stored on a non-transitory computer-readable medium such as computer memory, for example.

[0106] Referring first to Fig. 9A, a method 900A begins at an optional block 920, where a UE receives a message from the network including one or more access control parameters (see, e.g., event 620). The message can be a DL NAS message or another suitable message, and the UE can receive this message in a currently serving NTN cell for example. These access control parameters can apply specifically to the UE accessing an NTN cell. To associate these access control parameters with NTN access, the CN can include an identifier of a cell in which the UE should apply these parameters.

[0107] At optional block 925, the UE accesses pre-configured access control parameters for NTN access (see, e.g., event 625). As discussed above with reference to Table 1, the UE can store access identity specifically defined for UEs using satellite access technology. The UE can use this access identity to identify relevant access control parameters. Depending on the implementation or scenario, the UE can retrieve these parameters from a USIM or the local memory, for example. The UE generally implements either block 920 or block 925 to perform the method 900A, but it is also possible for the method 900A to include both block 920 and block 925, in which case the UE selects one of these sets of parameters.

[0108] Next, at block 940, the UE receives a broadcast message such as a SIB in an NTN cell in which the UE can seek service (see., e.g., 640). The broadcast message can include a cell identifier and access control parameters for the cell.

[0109] At block 927, the UE determines whether the UE retrieved pre-configured access control parameters at block 925 and, if so, the flow proceeds to block 952. At block 952, the UE applies the retrieved pre-configured access control parameters in the NTN cell (see, e.g., event 652).

[0110] Otherwise, at block 951, the UE determines whether the access control parameters received via the NAS message received at block 920 included a cell identifier. The flow proceeds to block 952, where the UE applies the received access control parameters regardless of the area of the NTN coverage, if there is no cell identifier provided with the access control parameters in the NAS message. If the access control parameters received via NAS included a cell identifier, the flow proceeds to block 950, where the UE compares the cell identifier to the cell identifier of the NTN cell (see, e.g., event 650). The flow proceeds to block 952 in case of a match, and to block 992 in case of a mismatch, where the UE applies the access control parameters included in the broadcast message.[0U1] Now referring to Fig. 9B, at block 922 of a method 900B, the UE receives a NAS message including an indication that the UE should override access control for an NTN cell (see, e.g., event 722). At block 926, the UE configures the override of access control for a particular NTN cell or for all NTN cell, depending on the implementation. The UE can determine whether a cell is an NTN cell based on the reported RAT type, for example. Depending on the implementation or scenario, the UE can be pre-configured to override access control for an NTN cell, for example in a USIM or the local memory. The UE generally implements either block 922 or block 926 to perform the method 900B, but it is also possible for the method 900B to include both block 922 and block 926, in which case the UE selects one of these sets of parameters.

[0112] Next, at block 942, the UE receives a broadcast message in an NTN cell (see., e.g., 742), and the broadcast message can include access control parameters for the NTN cell. Atblock 953, the UE applies the access control parameters in the broadcast message (see., e.g., 753).

[0113] At block 960, the UE determines whether the access control check allows the UE to immediate transmit an uplink message in the cell and, if so, the flow proceeds to block 970 (see, e.g., event 770). Otherwise, if at block 962 the UE determines that overriding the access control is allowed, the UE overrides (bypasses) the access control check at block 955 (see, e.g., event 755) and proceeds to block 970. If the UE determines that overriding the access control is not allowed, the UE proceeds to block 971 and refrains from attempting access to wait out the barring interval per the result of executing block 953.

[0114] Next, Fig. 10 illustrates a flow diagram of an example method 1000 in a CN for configuring a UE with access control parameter(s) for NTN access. At block 1002, the CN communicates with a UE in a connected state of the (see, e.g., event 602). At optional block 1010, the CN determines that the UE is leaving the area of NTN coverage (see, e.g., event 610). Next, at block 1012, the CN determines access control parameters for the UE (see, e.g., event 612). The CN transmits these parameters to the UE at block 1020 (see, e.g., event 6020).

[0115] Now referring to Fig. 11, an example method 1100 in a CN for configuring a UE with access control param eter(s) for NTN access begins at block 1102, in which the CN communicates with a UE in a connected state of the (see, e.g., event 702). At optional block 1110, the CN determines that the UE is leaving the area of NTN coverage (see, e.g., event 710). Next, at block 1114, the CN determines that the CN can override access control at the UE (see, e g., event 714).

[0116] At block 1115, the CN determines whether override access control at an NTN cell for the UE and, if so, proceeds to block 1122. At block 1122, the CN transmits a NAS message to the UE and includes an override indication for access control (see, e.g., event 722). Otherwise, the flow proceeds to block 1123, so to allow the UE to apply the default access control technique at the NTN cell.

[0117] Fig. 12 is a flow diagram of an example method 1200 for selecting access control parameters in view of access identity, which can be implemented in the UE 102. The method1200 begins at block 1242, where the UE receives RRC broadcast information in an NTN cell (see, e.g., event 842A). If, at block 1244, the UE determines that the RRC broadcast incudes access barring information for multiple access identities, the flow proceeds to block 1259. Otherwise, the flow proceeds to block 1258.

[0118] At block 1256, the UE applies the access control parameter defined for UEs entering a new area of NTN coverage (see, e.g., Table 2 above and event 858). At block 1259, the UE determines whether the satellite area is the same as in the previous access attempt and, if so, proceeds to block 1258. At block 1258, the UE applies the access barring information corresponds to access identity that is not defined for UEs entering a new area of NTN coverage (see, e.g., event 859). Thus, the UE can apply this access identity when the broadcast does not specify a separate access identity for entering a new area of NTN coverage, or when the UE has “exhausted” the access identity defined for new areas of NTN coverage, and now can be considered to remain in the same area of NTN coverage.

[0119] Next, Fig. 13 illustrates an example connection method 1300, which can be implemented in the UE 102 or another suitable UE. At block 1302, the UE receives information from a CN related to applying one or more access control parameters for accessing a target cell of an NTN (see, e.g., events 620, 625, 722, 726, 842A, 842B). At block 1350, the UE performs access control in accordance with the one or more access control parameters (see, e.g., events 652, 755, 856A, 856B, 858). At block 1370, the UE transmits an uplink message in the target cell in accordance with the access control (see, e.g., events 670, 770, 830, 846).

[0120] Finally, Fig. 14 illustrates an example connection method 1400, which can be implemented in the CN 110 or another suitable CN. At block 1402, the CN determines how a UE should perform access control for access a cell of an NTN (see, e.g., events 612, 714 ). At block 1420, the CN provides, to the UE, information related to applying one or more access control parameters at the UE (see, e.g., events 620, 722).

[0121] The following list of examples reflects a variety of the embodiments explicitly contemplated by the present disclosure.

[0122] Example 1. A connection method implemented in a user equipment (UE), comprising: receiving, from a core network, information related to applying one or more access control parameters for accessing a target cell; performing, in the target cell, access control in accordance with the information; and transmitting an uplink message in the target cell in accordance with the access control.

[0123] Example 2. The method of example 1, wherein: the information includes the one or more access control parameters; the performing of the access control includes performing an access control check using the one or more access control parameters.

[0124] Example s. The method of example 2, further comprising: receiving, in the target cell via a system information broadcast, default one or more access control parameters distinct from the received one or more access control parameters; and selecting, based on the information, the received one or more access control parameters for the access control check, based on the information.

[0125] Example 4. The method of example 2 or 3, wherein the one or more access control parameters include one or more of: an access barring factor, or access barring time.

[0126] Example 5. The method of example 1, wherein the information includes: an indication to override one or more default access control parameters.

[0127] Example 6. The method of example 5, wherein: the performing of the access control includes bypassing at least one instance of an access control check prior to the transmitting of the uplink message.

[0128] Example 7. The method of example 6, further comprising: receiving, in the target cell via a system information broadcast, default one or more access control parameters for the access control check.

[0129] Example 8. The method of example 7, further comprising: performing the access control check in accordance with the default one or more access control parameters; and determining, based on the performing the access control check, that the UE is temporarily barred from accessing the target cell; wherein the bypassing includes: overriding thedetermining that the UE is temporarily barred and immediately proceeding to the transmitting of the uplink message.

[0130] Example 9. The method of any of the preceding examples, wherein: the receiving of the information is from via a radio access network (RAT) with which the NTN is associated.

[0131] Example 10. The method of example 9, wherein: the receiving is via a currently serving cell distinct from the target cell.

[0132] Example 11. The method of example 10, wherein: the currently serving cell is associated with a first satellite, and the target cell is associated with a second satellite.

[0133] Example 12. The method of any of the preceding examples, wherein the one or more access control parameters are included in a downlink (DL) non-access stratum (NAS) message addressed to the UE.

[0134] Example 13. The method of example 12, wherein the DL NAS message is one of: (i) an ATTACH ACCEPT message, (ii) a TRACKING AREA UPDATE ACCEPT message, (iii) a SERVICE ACCEPT message, (iv) a GUTI REALLOCATION COMMAND message, (v) a REGISTRATION ACCEPT message, or (vi) a CONFIGURATION UPDATE COMMAND message.

[0135] Example 14. The method of example 12 or 13, wherein: the one or more access control parameters are included in an information (IE) element dedicated to conveying access control parameters for NTN access.

[0136] Example 15. The method of any of examples 1-8, wherein: the receiving of the information is via a provisioning, by the core network, of a Universal Subscriber Identity Module (USIM) file of the UE.

[0137] Example 16. The method of any of the preceding examples, wherein: the information is related to a first cell identifier; and the performing of the access control in accordance with the information is in response to determining that the first cell identifier matches a cell identifier of the target cell.

[0138] Example 17. The method of any of examples 1-15, wherein: the information is related to multiple NTN cells; and the performing of the access control in accordance with the information is in response to determining that the target cell is an NTN cell.

[0139] Example 18. The method of example 17, wherein: the determining that the target cell is the NTN cell is based on a radio access technology (RAT) type of the target cell.

[0140] Example 19. The method of example 18, wherein the RAT type is Narrowband Internet-of-Thing (NB-IoT).

[0141] Example 20. The method of example 18, wherein the RAT type is enhanced Machine Type Communication (eMTC).

[0142] Example 21. The method of any of examples 1-15, further comprising: determining that the information is for an access identity (Al) applicable only for NTN use; wherein the performing of the access control in accordance with the information is in response to determining that the Al currently applies to the.

[0143] Example 22. The method of example 21, wherein: the receiving of the information includes receiving the Al.

[0144] Example 23. The method of any of examples 1-15, wherein: the performing of the access control in accordance with the information is in response to determining that the UE has not attempted to access the target cell subsequent to leaving an area of coverage of another cell.

[0145] Example 24. The method of example 23, wherein the one or more access control parameters are associated with an Al applicable only for attempting to access an NTN cell in a first instance.

[0146] Example 25. The method of any of examples 1-15, further comprising: receiving, in the target cell, (i) a first set of one or more access control parameters and (ii) a second set of one or more access control parameters; and selecting the first set of one or more access control parameters in response to determining that the UE has not has not attempted to access the target cell subsequent to leaving an area of coverage of another cell.

[0147] Example 26. The method of any of the preceding examples, further comprising: receiving an indication of whether the information related to applying the one or more access control parameters is applicable in a single instance of attempting to access the target cell or multiple instances of the attempting to access the target cell.

[0148] Example 27. The method of any of examples 1-25, wherein: the performing of the access control is implemented in a radio resource control (RRC) layer

[0149] Example 28. A method implemented in a core network of a cellular communication system , the method for controlling network access of a user equipment and comprising: determining how the UE is to perform access control for accessing a target cell; and providing, to the UE via a non-access stratum (NAS) message, information related to applying one or more access control parameters for accessing the target cell, based on the determining.

[0150] Example 29. The method of example 28, wherein the target cell is a non-terrestrial network (NTN) cell.

[0151] Example 30. The method of example 28 or 29, wherein: the information includes the one or more access control parameters.

[0152] Example 31. The method of any of examples 28-30, wherein the one or more access control parameters include one or more of: an access barring factor, or access barring time.

[0153] Example 32. The method of any of examples 28-31, wherein: the information includes a cell identifier of the target cell.

[0154] Example 33. The method of example 28, wherein: the information includes an indication to override one or more default access control parameters for accessing the target cell.

[0155] Example 34. The method of any of examples 28-33, wherein: the providing is via a cell distinct from the target cell.

[0156] Example 35. The method of example 28, wherein the providing of the information includes: transmitting, via a current cell, the one or more access control parameters.

[0157] Example 36. The method of example 35, further comprising: transmitting, via the target cell, (i) a first access identity (Al) corresponding to the one or more access control parameters, and (ii) a second Al corresponding to one or more default access control parameters.

[0158] Example 37. The method of example 36, wherein the information indicates an Al.

[0159] Example 38. The method of example 37, wherein the Al is applicable only for NTN.

[0160] Example 39. The method of example 37, wherein the Al applicable only for attempting to access an NTN cell in a first instance.

[0161] Example 40. The method of any of examples 28-39, wherein the determining of how the UE is to perform the access control is based on: estimating an overload of a base station operating the target cell.

[0162] Example 41. The method of example 40, further comprising: receiving a current load information from the base station.

[0163] Example 42. The method of any of examples 28-41, wherein the determining of how the UE is to perform the access control is based on: determining mobility of the UE.

[0164] Example 43. The method of any of examples 28-42, wherein the determining of how the UE is to perform the access control is based on: determining a number of UEs currently accessing, and / or operating in, the target cell.

[0165] Example 44. The method of any of examples 28-43, wherein the determining of how the UE is to perform the access control is based on: determining a type of the UE.

[0166] Example 45. The method of example 44, wherein the type of the UE is Machine Type Communication (MTC).

[0167] Example 46. The method of example 44, wherein the type of the UE is Intemet-of- Things (loT).

[0168] Example 47. The method of any of examples 28-34, wherein the providing of the information includes: transmitting a downlink (DL) non-access stratum (NAS) message addressed to the UE.

[0169] Example 48. The method of example 47, wherein the DL NAS message is one of (i) an ATTACH ACCEPT message, (ii) a TRACKING AREA UPDATE ACCEPT message, (iii) a SERVICE ACCEPT message, (iv) a GUTI REALLOCATION COMMAND message, (v) a REGISTRATION ACCEPT message, or (vi) a CONFIGURATION UPDATE COMMAND message.

[0170] Example 49. The method of example 47 or 48, wherein: the one or more access control parameters are included in an IE dedicated to conveying access control parameters for NTN access.

[0171] Example 50. The method of any of examples 28-34, wherein the providing of the information includes: provisioning the UE via a USIM.

[0172] Example 51. A device comprising processing hardware and configured to implement a method of any of the preceding examples.

[0173] The following description may be applied to the description above.

[0174] 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.

[0175] A user device in which the techniques of this disclosure can be implemented (e.g., the UE 102) can be any suitable device capable of wireless communications such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, a media-streaming dongle or another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. 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). Stillfurther, the user device can operate as an intemet-of-things (loT) device or a mobile-internet device (MID). Depending on the type, the user device can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0176] Certain embodiments are described in this disclosure as including logic or a number of components or modules. Modules may 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 appli cation -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.

[0177] The term “or” as used herein is to be interpreted as an inclusive or meaning any one or any combination, unless expressly indicated otherwise, mutually exclusive, or indicated otherwise by context. Therefore, herein, the expression “A or B” means “A, B, or both A and B.”

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

Claims

What is claimed is:

1. A connection method implemented in a user equipment (UE), comprising: receiving, from a core network, access control information including (i) one or more access control parameters for accessing a target cell or (ii) an indication to override one or more default access control parameters to allow an access attempt for the target cell; performing, in the target cell, access control in accordance with the access control information; and transmitting an uplink message in the target cell in accordance with the access control.

2. The method of claim 1, further comprising: receiving, in the target cell, the default one or more access control parameters; and overriding the default one or more access control parameters according to the received indication to override the one or more default.

3. The method of claim 2, wherein the overriding includes: bypassing at least one instance of an access control check prior to the transmitting of the uplink message.

4. The method of claim 1, further comprising: receiving, in the target cell, the default one or more access control parameters; and selecting the received one or more access control parameters, different from the default one or more access control parameters, for the access control check.

5. The method of any of claims 2-4, wherein the default one or more access control parameters are received via a system information broadcast.

6. The method of any of the preceding claims, wherein:the receiving of the access control information is from via a radio access network (RAT) associated with a non-terrestrial network (NTN).

7. The method of any of the preceding claims, wherein the one or more access control parameters include one or more of an access barring factor, or access barring time.

8. The method of any of the preceding claims, wherein the one or more access control parameters are included in a downlink (DL) non-access stratum (NAS) message addressed to the UE.

9. The method of any of the preceding claims, further comprising: receiving a cell identifier corresponding to the access control information; and the performing of the access control in accordance with the access control information is in response to determining that the received first cell identifier matches a cell identifier of the target cell.

10. A method implemented in a core network of a cellular communication system, the method for controlling network access of a user equipment and comprising: determining how the UE is to perform access control for accessing a target cell of a nonterrestrial network (NTN); and providing, to the UE, access control information including (i) one or more access control parameters for accessing the target cell or (ii) an indication to override one or more default access control parameters to allow an access attempt for the target cell.

11. The method of claim 10, wherein the determining of how the UE is to perform the access control is based on: estimating an overload of a base station operating the target cell.

12. The method of claim 11, further comprising: receiving a current load information from the base station.

13. The method of any of claims 10-12, wherein the determining of how the UE is to perform the access control is based on: determining a number of UEs currently accessing, and / or operating in, the target cell.

14. The method of any of claims 10-13, wherein the determining of how the UE is to perform the access control is based on: determining a type of the UE.

15. A device comprising processing hardware and configured to implement a method of any of the preceding claims.

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