Conditional switching configuration in non-terrestrial networks

Abstract

The present disclosure relates to techniques for configuring condition switching in a non-terrestrial wireless communication system. A wireless device and a cellular base station can establish a wireless link based on a non-terrestrial network. The wireless device can receive conditional handover information from the cellular base station in broadcast system information. The conditional handover information can indicate conditional handover trigger conditions for one or more candidate cells. The wireless device can evaluate the conditional switch trigger condition. The wireless device can perform a handover to a candidate cell upon triggering a conditional handover to the candidate cell.

Description

Technical Field

[0001] The present application relates to wireless communications, and more particularly to systems, apparatuses, and methods for configuring conditional handoffs in non-terrestrial wireless communication systems. Background Art

[0002] The use of wireless communication systems is growing rapidly. In recent years, wireless devices such as smart phones and tablet computers have become increasingly sophisticated. In addition to supporting phone calls, many mobile devices (i.e., user equipment devices or UEs) now also provide access to the Internet, email, text messaging, and navigation using a global positioning system (GPS), and are capable of operating sophisticated applications that utilize these capabilities. In addition, there are many different wireless communication technologies and wireless communication standards. Some examples of wireless communication standards include GSM, UMTS (e.g., associated with WCDMA or TD-SCDMA air interfaces), LTE, Advanced LTE (LTE-A), NR, HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), IEEE 802.11 (WLAN or Wi-Fi), Bluetooth, and the like. TM Etc. The proliferation of wireless communication technologies and standards may cover terrestrial networks as well as non-terrestrial networks (NTNs) such as 3GPP satellite networks.

[0003] The introduction of an ever-increasing number of features and functionalities in wireless communication devices has also created a continuing need for improved wireless communications and improved wireless communication devices. In particular, it is important to ensure the accuracy of signals transmitted and received by user equipment (UE) devices (e.g., by wireless devices such as cellular phones, base stations, and relay stations used in wireless cellular communications). In addition, increasing the functionality of UE devices may put a great strain on the battery life of UE devices. Therefore, it is also very important to reduce the power requirements in UE device design while allowing the UE device to maintain good transmission and reception capabilities to improve communications. Therefore, improvements are desired in this area. Summary of the invention

[0004] Embodiments of apparatus, systems, and methods for configuring conditional handoffs using broadcast system information in a non-terrestrial wireless communication system are presented herein.

[0005] Conditional handover techniques may be used to improve handover robustness in cellular communication systems such as 3GPP 5G NR. Such techniques may include a cellular base station providing a handover command in advance to reduce or avoid the possibility of a traditional handover failure due to a failure to send a measurement result or a failure to send a handover command.

[0006] In a non-terrestrial wireless communication system, a cellular base station may provide multiple cells via a satellite, for example, which may relay communications between the cellular base station and the wireless devices served by the cellular base station. In such a system, it may be beneficial to support techniques for broadcasting conditional handover information to wireless devices, which may, for example, allow those wireless devices to perform conditional handovers (e.g., at least to other cells provided by the same cellular base station) without using dedicated signaling to configure the conditional handovers. For example, such techniques may reduce the signaling burden required to perform handovers, which may be beneficial to network resource usage efficiency and / or reduce wireless device power consumption. Therefore, techniques for broadcasting conditional handover information to wireless devices in a non-terrestrial wireless communication system are described herein.

[0007] In some instances, such as when a quasi-earth fixed satellite cell is scheduled to change service areas, a relatively large number of handoffs may occur from the cell in a relatively short amount of time. Therefore, at least according to some embodiments, in conjunction with techniques for supporting broadcasting conditional handoff information to wireless devices in a non-terrestrial wireless communication system, techniques for mitigating the potential impact of such a scenario are also described herein, such as by broadcasting random access channel configuration information associated with the conditional handoff information, which can help manage the random access channel resources used by the wireless devices in the cell so as to mitigate the possibility of random access channel conflicts and handoff failures.

[0008] It should be noted that the techniques described herein may be implemented in and / or used with a number of different types of devices, including but not limited to base stations, access points, cellular telephones, portable media players, tablet computers, wearable devices, unmanned aerial vehicles, unmanned flight controllers, automobiles and / or motor vehicles, and various other computing devices.

[0009] This summary is intended to provide a brief overview of some of the topics described in this document. Therefore, it should be understood that the above features are only examples and should not be construed as narrowing the scope or essence of the topics described herein in any way. Other features, aspects, and advantages of the topics described herein will become apparent through the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A better understanding of the present subject matter may be obtained when the following detailed description of various embodiments is considered in conjunction with the following drawings, in which:

[0011] Figure 1 illustrates an exemplary (and simplified) wireless communication system according to some embodiments;

[0012] Figure 2illustrates an exemplary base station in communication with an exemplary wireless user equipment (UE) device according to some embodiments;

[0013] Figure 3 illustrates an exemplary block diagram of a UE according to some embodiments;

[0014] Figure 4 illustrates an exemplary block diagram of a base station according to some embodiments;

[0015] Figure 5 is a network infrastructure diagram illustrating aspects of an exemplary 3GPP satellite network deployment according to some embodiments;

[0016] Figure 6 to Figure 7 is a schematic diagram illustrating possible interworking between a 3GPP terrestrial radio access network (RAN) and a satellite radio access network according to some embodiments; and

[0017] Figure 8 is a flow chart illustrating aspects of an exemplary possible method for configuring conditional handover in a non-terrestrial wireless communication system according to some embodiments; and

[0018] FIG. 9A to FIG. 9B Signal flow aspects of an exemplary dedicated signaling scheme for configuring conditional handover for a wireless device in accordance with some embodiments are illustrated.

[0019] Although the features described herein are susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and described in detail herein. However, it should be understood that the drawings and detailed description thereof are not intended to be limited to the specific forms disclosed, but on the contrary, are intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the appended claims. DETAILED DESCRIPTION

[0020] Acronyms

[0021] Various acronyms are used throughout this disclosure. Definitions of the most commonly used acronyms that may appear throughout this disclosure are provided below:

[0022] UE: User Equipment

[0023] RF: Radio Frequency

[0024] BS: Base Station

[0025] GSM: Global System for Mobile Communications

[0026] UMTS: Universal Mobile Telecommunications System

[0027] LTE: Long Term Evolution

[0028] NR: New Radio

[0029] NTN: Non-terrestrial Network

[0030] TX: Send

[0031] RX: Receive

[0032] RAT: Radio Access Technology

[0033] TRP: Transmit Receive Point

[0034] TA: Timing Advance

[0035] DCI: Downlink Control Information

[0036] the term

[0037] The following is a glossary of terms that will appear in this disclosure:

[0038] Memory medium—any of various types of non-transitory memory devices or storage devices. The term "memory medium" is intended to include installation media, such as CD-ROM, floppy disk, or tape devices; computer system memory or random access memory, such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; non-volatile memory, such as flash memory, magnetic media, such as hard disk drives or optical storage devices; registers or other similar types of memory elements, etc. The memory medium may also include other types of non-transitory memory or combinations thereof. In addition, the memory medium may be located in a first computer system executing a program, or may be located in a different second computer system connected to the first computer system via a network such as the Internet. In the latter example, the second computer system may provide program instructions to the first computer system for execution. The term "memory medium" may include two or more memory media, which may reside in different locations in different computer systems connected, for example, via a network. The memory medium may store program instructions (e.g., embodied as a computer program) that may be executed by one or more processors.

[0039] Carrier Media—Memory media as described above, as well as physical transmission media such as a bus, network, and / or other physical transmission media that convey signals such as electrical, electromagnetic, or digital signals.

[0040] Computer system (or computer)—any of various types of computing or processing systems, including a personal computer system (PC), a mainframe computer system, a workstation, a network appliance, an Internet appliance, a personal digital assistant (PDA), a television system, a grid computing system, or other devices or combinations of devices. In general, the term "computer system" may be broadly defined as any device (or combination of devices) that includes at least one processor that executes instructions from a memory medium.

[0041] User Equipment (UE) (or "UE device") - any of various types of computer systems or devices that are mobile or portable and that perform wireless communications. Examples of UE devices include mobile phones or smart phones (e.g., iPhone TM , based on Android TM phones), tablet computers (e.g., iPad TM 、Samsung Galaxy TM ), portable gaming devices (e.g., Nintendo DS TM , PlayStation Portable TM 、Gameboy Advance TM , iPhone TM ), wearable devices (e.g., smart watches, smart glasses), laptops, PDAs, portable Internet devices, music players, data storage devices, other handheld devices, automobiles and / or motor vehicles, unmanned aerial vehicles (UAVs) (e.g., drones), UAV controllers (UACs), etc. In general, the term "UE" or "UE device" can be broadly defined to cover any electronic device, computing device, and / or telecommunication device (or a combination of these devices) that is easily transportable by a user and capable of wireless communication.

[0042] Wireless Device—Any of various types of computer systems or devices that perform wireless communications. A wireless device may be portable (or mobile), or may be stationary or fixed at a location. A UE is an example of a wireless device.

[0043] Communication device - any of various types of computer systems or devices that perform communication, where the communication may be wired or wireless. A communication device may be portable (or mobile), or may be stationary or fixed at a location. A wireless device is an example of a communication device. A UE is another example of a communication device.

[0044] Base Station (BS)—The term "base station" has the full breadth of its ordinary meaning and includes at least a wireless communication station installed at a fixed location and used to communicate as part of a wireless telephone system or radio system.

[0045] Processing element (or processor) - refers to various elements or combinations of elements that are capable of performing functions in a device (e.g., a user equipment device or a cellular network device). Processing elements may include, for example, processors and associated memory, portions or circuits of individual processor cores, entire processor cores, processor arrays, circuits such as ASICs (application specific integrated circuits), programmable hardware elements such as field programmable gate arrays (FPGAs), and any of the above combinations.

[0046] Wi-Fi—The term "Wi-Fi" has the full scope of its ordinary meaning and includes at least a wireless communication network or RAT that is served by wireless LAN (WLAN) access points and provides connectivity to the Internet through these access points. Most modern Wi-Fi networks (or WLAN networks) are based on the IEEE 802.11 standard and are marketed under the name "Wi-Fi". Wi-Fi (WLAN) networks are distinct from cellular networks.

[0047] Automatically—refers to an action or operation being performed by a computer system (e.g., software executed by a computer system) or a device (e.g., a circuit, a programmable hardware element, an ASIC, etc.) without the action or operation being directly specified or performed by a user input. Thus, the term "automatically" is in contrast to an operation being manually performed or specified by a user, where the user provides input to directly perform the operation. An automatic process may be initiated by input provided by a user, but subsequent actions performed "automatically" are not specified by the user, i.e., are not performed "manually," where the user specifies each action to be performed. For example, a user filling out an electronic form by selecting each field and providing input specifying information (e.g., by typing in information, selecting checkboxes, radio selections, etc.) is manually filling out the form, even though the computer system must update the form in response to the user action. The form may be automatically filled out by a computer system, where the computer system (e.g., software executed on the computer system) analyzes the fields of the form and fills out the form without any user input specifying the answers to the fields. As indicated above, a user may invoke automatic filling out of a form, but not participate in the actual filling out of the form (e.g., the user does not manually specify the answers to the fields but rather they are automatically completed). This specification provides various examples of operations that are automatically performed in response to actions that a user has taken.

[0048] Configured to—Various components may be described as being “configured to” perform one or more tasks. In such contexts, “configured to” is a broad statement that generally means “having a structure” that performs one or more tasks during operation. Thus, a component may be configured to perform a task even when the component is not currently performing the task (e.g., a collection of electrical conductors may be configured to electrically connect a module to another module even when the two modules are not connected). In some contexts, “configured to” may be a broad statement that generally means “having a circuit” that performs one or more tasks during operation. Thus, a component may be configured to perform a task even when the component is not currently turned on. Typically, circuits that form a structure corresponding to “configured to” may include hardware circuits.

[0049] For ease of description, various components may be described as performing one or more tasks. Such descriptions should be interpreted as including the phrase "configured to". The description of a component being configured to perform one or more tasks is expressly intended not to invoke the interpretation of 35 U.S.C. § 112, paragraph (s) for that component.

[0050] Figure 1 and Figure 2 -Exemplary Communication System

[0051] Figure 1 An exemplary (and simplified) wireless communication system that can implement various aspects of the present disclosure according to some embodiments is illustrated. Note that Figure 1 The system is only one example of a possible system, and the embodiments may be implemented in any of a variety of systems as desired.

[0052] As shown, the exemplary wireless communication system includes a base station 102, which communicates with one or more (e.g., any number) user equipment 106A, 106B, etc. to 106N through a transmission medium. Each user equipment may be referred to as a "user equipment" (UE) or a UE device in this document. Therefore, the user equipment 106 is referred to as a UE or a UE device.

[0053] The base station 102 may be a base transceiver station (BTS) or a cell site, and may include hardware and / or software that implements wireless communication with UEs 106A to 106N. If the base station 102 is implemented in the context of LTE, it may be referred to as an "eNodeB" or "eNB". If the base station 102 is implemented in the context of 5G NR, it may alternatively be referred to as a "gNodeB" or "gNB". The base station 102 may also be equipped to communicate with a network 100 (e.g., a core network of a cellular service provider, a telecommunications network such as a public switched telephone network (PSTN), and / or the Internet, and various possible networks). Therefore, the base station 102 may facilitate communication between user devices and / or between user devices and the network 100. The communication area (or coverage area) of a base station may be referred to as a "cell". Also as used herein, with respect to a UE, sometimes a base station may be considered to represent a network in consideration of the uplink and downlink communications of the UE. Therefore, a UE communicating with one or more base stations in a network may also be understood as a UE communicating with a network.

[0054] The base station 102 and the user equipment may be configured to communicate over a transmission medium using any of a variety of radio access technologies (RATs), also referred to as wireless communication technologies or telecommunication standards, such as GSM, UMTS (WCDMA), LTE, Advanced LTE (LTE-A), LAA / LTE-U, 5G NR, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), Wi-Fi, etc.

[0055] Base station 102 and other similar base stations operating according to the same or different cellular communication standards may thus be provided as one or more cell networks that may provide continuous or nearly continuous overlapping service to UE 106 and similar devices over a geographic area via one or more cellular communication standards.

[0056] Note that UE 106 is capable of communicating using multiple wireless communication standards. For example, UE 106 may be configured to communicate using either or both of the 3GPP cellular communication standard or the 3GPP2 cellular communication standard. In some embodiments, UE 106 may be configured to perform techniques for configuring conditional handover in a non-terrestrial wireless communication system, such as according to the various methods described herein. UE 106 may also or alternatively be configured to communicate using WLAN, Bluetooth, or a combination thereof. TM, one or more global navigation satellite systems (GNSS, such as GPS or GLONASS), one and / or more mobile television broadcast standards (e.g., ATSC-M / H), etc. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

[0057] Figure 2 An exemplary user equipment 106 (e.g., one of devices 106A to 106N) communicating with a base station 102 according to some embodiments is illustrated. UE 106 may be a device with wireless network connectivity, such as a mobile phone, a handheld device, a wearable device, a computer or tablet computer, an unmanned aerial vehicle (UAV), an unmanned flight controller (UAC), a car, or almost any type of wireless device. UE 106 may include a processor (processing element) configured to execute program instructions stored in a memory. UE 106 may perform any method implementation in the method implementation scheme described herein by executing such stored instructions. Alternatively or in addition, UE 106 may include a programmable hardware element, such as an FPGA (field programmable gate array), an integrated circuit, and / or any of various other possible hardware components configured to perform (e.g., individually or in combination) any method implementation in the method implementation scheme described herein or any part of any method implementation in the method implementation scheme described herein. UE 106 may be configured to communicate using any of a plurality of wireless communication protocols. For example, UE 106 may be configured to communicate using two or more of CDMA2000, LTE, LTE-A, 5G NR, WLAN, or GNSS. Other combinations of wireless communication standards are also possible.

[0058] UE 106 may include one or more antennas for communicating using one or more wireless communication protocols according to one or more RAT standards. In some embodiments, UE 106 may share one or more parts of a receive chain and / or a transmit chain between multiple wireless communication standards. The shared radio component may include a single antenna, or may include multiple antennas (e.g., for a multiple-input, multiple-output or "MIMO" antenna system) for performing wireless communications. Typically, the radio component may include any combination of a baseband processor, an analog RF signal processing circuit (e.g., including filters, mixers, oscillators, amplifiers, etc.), or a digital processing circuit (e.g., for digital modulation and other digital processing). Similarly, the radio component may use the aforementioned hardware to implement one or more receive chains and transmit chains. For example, UE 106 may share one or more parts of a receive chain and / or a transmit chain between multiple wireless communication technologies such as those discussed above.

[0059] In some embodiments, UE 106 may include any number of antennas and may be configured to use the antennas to send and / or receive directional wireless signals (e.g., beams). Similarly, BS 102 may also include any number of antennas and may be configured to use the antennas to send and / or receive directional wireless signals (e.g., beams). In order to receive and / or send such directional signals, the antennas of UE 106 and / or BS 102 may be configured to apply different "weights" to different antennas. The process of applying these different weights may be referred to as "pre-coding".

[0060] In some embodiments, UE 106 may include a separate transmit chain and / or receive chain (e.g., including separate antennas and other radio components) for each wireless communication protocol with which it is configured to communicate. As another possibility, UE 106 may include one or more radio components shared between multiple wireless communication protocols, and one or more radio components used uniquely by a single wireless communication protocol. For example, UE 106 may include shared radio components for communicating using any of LTE or CDMA2000 1xRTT (or LTE or NR, or LTE or GSM), and shared radio components for communicating using Wi-Fi and Bluetooth. TM Each of the independent radio components for communication. Other configurations are also possible.

[0061] Figure 3 - Block diagram of an exemplary UE device

[0062] Figure 3A block diagram of an exemplary UE 106 according to some embodiments is illustrated. As shown, the UE 106 may include a system on chip (SOC) 300, which may include parts for various purposes. For example, as shown, the SOC 300 may include a processor 302 that can execute program instructions for the UE 106, and a display circuit 304 that can perform graphics processing and provide display signals to a display 360. The SOC 300 may also include a sensor circuit 370, which may include a component for sensing or measuring any of various possible characteristics or parameters of the UE 106. For example, the sensor circuit 370 may include a motion sensing circuit that is configured to detect the motion of the UE 106, for example, using a gyroscope, an accelerometer, and / or any of various other motion sensing components. As another possibility, the sensor circuit 370 may include one or more temperature sensing components, which are used, for example, to measure the temperature of each of one or more antenna panels and / or other components of the UE 106. Any of a variety of other possible types of sensor circuits may also or alternatively be included in the UE 106, as desired. The processor 302 may also be coupled to a memory management unit (MMU) 340, which may be configured to receive addresses from the processor 302 and translate those addresses into locations in memory (e.g., memory 306, read-only memory (ROM) 350, NAND flash memory 310) and / or other circuits or devices, such as display circuit 304, radio 330, connector I / F 320, and / or display 360. The MMU 340 may be configured to perform memory protection and page table translation or setup. In some embodiments, the MMU 340 may be included as part of the processor 302.

[0063] As shown, SOC 300 may be coupled to various other circuits of UE 106. For example, UE 106 may include various types of memory (e.g., including NAND flash memory 310), connector interface 320 (e.g., for coupling to a computer system, a docking station, a charging station, etc.), display 360, and wireless communication circuitry 330 (e.g., for LTE, LTE-A, NR, CDMA2000, Bluetooth TM, Wi-Fi, GPS, etc.). The UE device 106 may include or be coupled to at least one antenna (e.g., 335a), and may include multiple antennas (e.g., illustrated by antennas 335a and 335b) for performing wireless communications with base stations and / or other devices. Antennas 335a and 335b are shown by way of example, and the UE device 106 may include fewer or more antennas. In general, one or more antennas are collectively referred to as antennas 335. For example, the UE device 106 may use antenna 335 with the aid of radio circuitry 330 to perform wireless communications. The communication circuit may include multiple receive chains and / or multiple transmit chains for receiving and / or transmitting multiple spatial streams, such as in a multiple-input multiple-output (MIMO) configuration. As mentioned above, in some embodiments, the UE may be configured to perform wireless communications using multiple wireless communication standards.

[0064] UE 106 may include hardware and software components for implementing a method for UE 106 to configure conditional switching in a non-terrestrial wireless communication system, such as described further herein. The processor 302 of UE device 106 may be configured to implement part or all of the methods described herein, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). In other embodiments, the processor 302 may be configured as a programmable hardware element, such as an FPGA (field programmable gate array) or as an ASIC (application-specific integrated circuit). In addition, according to various embodiments disclosed herein, the processor 302 may be coupled to Figure 3 The processor 302 may also implement various other applications and / or end-user applications running on the UE 106.

[0065] In some embodiments, radio 330 may include a separate controller dedicated to controlling communications for each corresponding RAT standard. Figure 3 As shown, the radio component 330 may include a Wi-Fi controller 352, a cellular controller (e.g., an LTE and / or LTE-A controller) 354, and a Bluetooth controller. TM Controller 356, and in at least some embodiments, one or more or all of these controllers may be implemented as respective integrated circuits (referred to as ICs or chips) that communicate with each other and with SOC 300 (and more specifically, with processor 302). For example, Wi-Fi controller 352 may communicate with cellular controller 354 via a cell-ISM link or WCI interface, and / or Bluetooth controller 355 may communicate with cellular controller 354 via a cell-ISM link or WCI interface. TMThe controller 356 may communicate with the cellular controller 354 via a cell-ISM link, etc. Although three separate controllers are illustrated within the radio 330, other embodiments may be implemented in the UE device 106 having fewer or more similar controllers for various different RATs.

[0066] Additionally, embodiments are contemplated in which the controller may implement functionality associated with multiple radio access technologies. For example, according to some embodiments, in addition to hardware and / or software components for performing cellular communications, the cellular controller 354 may also include hardware and / or software components for performing one or more activities associated with Wi-Fi, such as Wi-Fi preamble detection, and / or generation and transmission of Wi-Fi physical layer preamble signals.

[0067] Figure 4 - Block diagram of an exemplary base station

[0068] Figure 4 1 illustrates a block diagram of an exemplary base station 102 according to some embodiments. Note that Figure 4 The base station of is only one example of a possible base station. As shown, the base station 102 may include a processor 404 that may execute program instructions for the base station 102. The processor 404 may also be coupled to a memory management unit (MMU) 440 or other circuit or device, which may be configured to receive addresses from the processor 404 and convert these addresses to locations in memory (e.g., memory 460 and read-only memory (ROM) 450).

[0069] Base station 102 may include at least one network port 470. Network port 470 may be configured to couple to a telephone network and provide access to the telephone network described above. Figure 1 and Figure 2 The network port 470 may be configured to couple to a plurality of devices such as the UE device 106 to the telephone network described in the foregoing. The network port 470 (or an additional network port) may also or alternatively be configured to couple to a cellular network, such as a core network of a cellular service provider. The core network may provide mobility-related services and / or other services to a plurality of devices such as the UE device 106. In some cases, the network port 470 may be coupled to the telephone network via the core network, and / or the core network may provide the telephone network (e.g., in other UE devices served by the cellular service provider).

[0070] In some embodiments, base station 102 may be a next generation base station, such as a 5G New Radio (5G NR) base station, or "gNB". In such embodiments, base station 102 may be connected to a legacy evolved packet core (EPC) network and / or to an NR core (NRC) network. Furthermore, base station 102 may be considered a 5G NR cell and may include one or more transition and reception points (TRPs). Furthermore, a UE capable of operating in accordance with 5G NR may be connected to one or more TRPs within one or more gNBs.

[0071] The base station 102 may include at least one antenna 434 and possibly multiple antennas. One or more antennas 434 may be configured to operate as a wireless transceiver and may be further configured to communicate with the UE device 106 via the radio component 430. The antenna 434 communicates with the radio component 430 via a communication chain 432. The communication chain 432 may be a receive chain, a transmit chain, or both. The radio component 430 may be designed to communicate via various wireless telecommunication standards, including but not limited to 5G NR, 5G NR SAT, LTE, LTE-A, GSM, UMTS, CDMA2000, Wi-Fi, etc.

[0072] Base station 102 may be configured to perform wireless communications using multiple wireless communication standards. In some examples, base station 102 may include multiple radio components that enable base station 102 to communicate according to multiple wireless communication technologies. For example, as one possibility, base station 102 may include an LTE radio component for performing communications according to LTE and a 5GNR radio component for performing communications according to 5G NR. In this case, base station 102 may be able to operate as both an LTE base station and a 5GNR base station. As another possibility, base station 102 may include a multimode radio component capable of performing communications according to any one of multiple wireless communication technologies (e.g., 5G NR and Wi-Fi, 5G NR SAT and Wi-Fi, LTE and Wi-Fi, LTE and UMTS, LTE and CDMA2000, UMTS and GSM, etc.).

[0073] As further described later herein, BS 102 may include hardware and software components for implementing or supporting a specific implementation of the features described herein. The processor 404 of the base station 102 may be configured to implement and / or support a specific implementation of part or all of the methods described herein, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively, the processor 404 may be configured as a programmable hardware element such as an FPGA (field programmable gate array), or as an ASIC (application-specific integrated circuit) or a combination thereof. In the case of certain RATs (e.g., Wi-Fi), the base station 102 may be designed as an access point (AP), in which case the network port 470 may be implemented to provide access to a wide area network and / or one or more local area networks, for example, it may include at least one Ethernet port, and the radio component 430 may be designed to communicate according to the Wi-Fi standard.

[0074] Furthermore, as described herein, processor 404 may include one or more processing elements. Thus, processor 404 may include one or more integrated circuits (ICs) configured to perform the functions of processor 404. Furthermore, each integrated circuit may include circuits (e.g., a first circuit, a second circuit, etc.) configured to perform the functions of one or more processors 404.

[0075] Additionally, as described herein, radio 430 may include one or more processing elements. Thus, radio 430 may include one or more integrated circuits (ICs) configured to perform the functions of radio 430. Additionally, each integrated circuit may include circuits (e.g., a first circuit, a second circuit, etc.) configured to perform the functions of radio 430.

[0076] Figures 5 to 7 ——3GPP Satellite Network Infrastructure

[0077] Figure 5 5 is a network infrastructure diagram showing a 3GPP satellite network deployment according to some embodiments. As shown, a satellite 500 broadcasts a service link to a UE 506, where the UE 506 operates within a cell. The satellite 500 also communicates with a ground gateway 510 via a feeder link, and the gateway 510 is then communicatively coupled to a base station 502 (e.g., a gNB). The base station 502 includes a distributed unit (DU) and a centralized unit (CU). The base station 502 is then coupled to a 5G core network (5GC) 508 with a tracking area code (TAC) via an N2 interface. It should be noted that the satellite 500 may include any of various types of satellites, such as various possibilities such as a geosynchronous equatorial orbit (GEO) satellite, a low earth orbit (LEO) satellite, or a medium earth orbit (MEO) satellite.

[0078] Figure 6 to Figure 7 is a schematic diagram illustrating possible interworking between a 3GPP terrestrial radio access network (RAN) and a satellite radio access network according to some embodiments. Figure 6 In the example, UE 106 performs the following steps: Figure 1 to Figure 2 The gNB shown in FIG. communicates with the 3GPP terrestrial RAN. The 3GPP terrestrial RAN is coupled to the core network via the N2 interface, and the 3GPP satellite RAN is also coupled to the core network via the N2 interface. Figure 7 The UE 106 is shown operating with a cell to obtain 3GPP terrestrial access. The UE 106 also operates in a wider geographic area providing 3GPP satellite access.

[0079] Figure 8 -Configure conditional switching in non-terrestrial networks

[0080] Wireless devices operating in a radio resource control (RRC) connected mode may manage their mobility operations with the cellular network with which they are registered, such as through handover operations. In some cases, such handovers may include a serving base station providing signaling to the wireless device that configures the wireless device (e.g., periodically or in an event-based manner) to perform measurements of neighboring cells, receiving signaling including measurement reports from the wireless device based on those measurements, and providing signaling to the wireless device to configure a handover to another cell if certain handover conditions are met.

[0081] Using such timely signaling between the network and the device to perform handovers can allow for dynamic selection of the best cell to perform the handover when a handover is needed. However, such timely signaling can sometimes result in handover failures, for example, because timely configuration of the handover may typically occur under relatively weak channel / signal conditions. Such scenarios may occur more commonly under fast moving conditions, in high cell density deployments in frequency ranges with high propagation losses utilizing directional transmissions (beamforming), and / or more generally in scenarios where channel quality may degrade relatively quickly, at least according to some embodiments.

[0082] Therefore, in some instances, conditional switching can be used to, for example, reduce the reliance on timely RRC signaling with the source cell at the time of switching, which can make the switching more reliable. Conditional switching may include attempting to pre-deliver a switching command for the cell in advance, for example, when conditions are good (e.g., when the device is stationed and / or has good signal quality), and allowing the device to switch later, for example, using a reduced signaling set. Such techniques can help reduce data loss, data gaps, and data stagnation, and can help reduce the delay of a wireless device switching from one cell to another. However, although the signaling required to perform such conditional switching at the time of switching can be reduced compared to timely switching signaling, if dedicated RRC signaling is used to configure the conditional switching, the total signaling load for performing the switching may be relatively large in both cases.

[0083] A wireless communication system that includes non-terrestrial elements (such as satellites, high altitude platforms, aircraft, etc.) may be referred to herein as a non-terrestrial network or NTN, even if one or more elements of the system are ground-based (as may be common). Such a system (e.g., which may include non-geostationary satellites as relays in wireless links between wireless devices and cellular base stations) may have a greater potential for variation in the relative positioning of elements in the system relative to a fully terrestrial system and / or a system that does not include relay elements. This increased potential mobility of system elements may create an additional need for wireless device handoffs, for example because satellite mobility (e.g., for non-geostationary (NGSO) satellites) may be the reason a handoff is necessary in addition to or as an alternative to wireless device mobility.

[0084] Some NTN systems may include quasi-earth fixed satellites. Such satellites may be able to provide service cells to the service area for a certain period of time by steering their antennas to maintain a relatively fixed or static area (e.g., a shape centered on a reference position), even if the satellite's positioning relative to the earth may be changing. After a certain amount of time (e.g., due to a change in satellite positioning), the antenna may be redirected to a different service area, and the satellite may then provide services to the new cell location in the next period of time. When such a service area is shifted for a cell provided by such a satellite, any wireless device served by the cell may need to find a new service cell. Since the timing for such a shift can be planned in advance, a method for handling such a shift may include configuring conditional switching, wherein the timing of the shift in the service area of ​​the NTN cell is a possible basis for a trigger condition for the conditional switching (e.g., a conditional switching may be triggered in the time period that causes the service area to shift, to potentially avoid interruption of service to wireless devices served by the cell after the service area shifts).

[0085] In at least some instances, when such quasi-earth fixed satellites providing NTN cells displace coverage areas, handovers can potentially be facilitated for a relatively large number of wireless devices served by the NTN cells in a relatively short amount of time. In addition, some or perhaps even most or all of those handovers may include moving to a target NTN cell provided by the same cellular base station, which target NTN cell may have substantially similar configuration settings / parameters. Therefore, it may be possible to support the use of broadcast system information to configure conditional handovers for multiple wireless devices in such NTN cells, for example, rather than using dedicated (e.g., RRC) signaling to configure conditional handovers. This approach may potentially reduce the signaling burden for configuring conditional handovers, which may improve network resource usage efficiency and / or reduce wireless device power consumption in at least some instances.

[0086] Therefore, it may be beneficial to provide a technique for configuring conditional switching using broadcast system information in a non-terrestrial wireless communication system. To illustrate such a possible set of techniques, Figure 8 is a flow chart illustrating a method for configuring conditional handover using broadcast system information in a non-terrestrial wireless communication system according to at least some embodiments.

[0087] Figure 8 Aspects of the method may be performed by a wireless device, for example, in conjunction with one or more cellular base stations (such as UE 106 and BS 102, or UE 106 shown and described with respect to the various figures herein). Figure 5 The present invention may be implemented by using the UE 506, satellite 500 and gNB 502 shown in the figure, or more generally, implemented in combination with any of the computer circuits, systems, devices, elements or components shown in the above figures as needed. For example, the processor (and / or other hardware) of such a device may be configured to cause the device to perform any combination of the illustrated method elements and / or other method elements.

[0088] It is noted that although the present invention is described in a manner involving the use of communication techniques and / or features associated with 3GPP and / or NR specification documents, Figure 8 However, this description is not intended to limit the present disclosure and may be used in any suitable wireless communication system as needed. Figure 8 In various embodiments, some of the elements of the method shown may be performed simultaneously in an order different from that shown, may be replaced by other method elements, or may be omitted. Additional method elements may also be performed as needed. As shown in the figure, Figure 8 The method can be operated as follows.

[0089] In 802, the wireless device may establish a wireless link with a cellular base station. According to some embodiments, the wireless link may include a cellular link according to 5G NR. For example, the wireless device may establish a session with an access and mobility function (AMF) entity of the cellular network through one or more gNBs that provide radio access to the cellular network. As another possibility, the wireless link may include a cellular link according to LTE. For example, the wireless device may establish a session with a mobility management entity of the cellular network through an eNB that provides radio access to the cellular network. According to various embodiments, other types of cellular links are also possible, and the cellular network may also or alternatively operate according to another cellular communication technology (e.g., UMTS, CDMA2000, GSM, etc.).

[0090] According to at least some embodiments, the wireless link may include multiple hops. For example, one or more non-terrestrial network elements (such as satellites) may be used as relay devices to establish a wireless link. In such a scenario, the wireless link between the wireless device and the cellular base station may include a service link (e.g., between the wireless device and the satellite) and a feeder link (e.g., between the satellite and the cellular base station or another network element communicatively coupled to the cellular base station). Thus, the wireless device and the satellite may communicate directly wirelessly via the service link, and the satellite may relay those communications with the cellular base station via the feeder link.

[0091] Establishing a wireless link may include establishing an RRC connection with a serving cellular base station according to at least some embodiments. Establishing a first RRC connection may include configuring various parameters for communication between the wireless device and the cellular base station, establishing environmental information of the wireless device, and / or any of a variety of other possible features, for example, involving establishing an air interface of the wireless device for cellular communication with a cellular network associated with the cellular base station. After establishing the RRC connection, the wireless device may operate in an RRC connected state. In some instances, the RRC connection may also be released (e.g., after a certain period of inactivity relative to data communications), in which case the wireless device may operate in an RRC idle state or an RRC inactive state. In some instances, the wireless device may perform a handover (e.g., when in an RRC connected mode) or a cell reselection (e.g., when in an RRC idle mode or an RRC inactive mode) to a new serving cell, for example, due to wireless device mobility, serving cell mobility, changes in wireless medium conditions, and / or any of a variety of other possible reasons.

[0092] In at least some instances, establishing the wireless link may include the wireless device providing capability information of the wireless device. Such capability information may include information related to any of a plurality of types of wireless device capabilities.

[0093] At 804, the wireless device may receive conditional handover information in broadcast system information. According to at least some embodiments, the broadcast system information may be received from a cellular base station via a satellite providing an NTN cell associated with the cellular base station. The conditional handover information may indicate one or more conditional handover triggering conditions for one or more candidate cells.

[0094] In some instances, the broadcast system information configuring the conditional handover may be provided periodically by the cellular base station, for example as part of its normal system information broadcast operation. In some instances, it is alternatively possible that the broadcast system information configuring the conditional handover may be provided as on-demand system information, which may be sent by the cellular base station in response to a request or query from one or more wireless devices served by the cellular base station. For example, in some instances, the cellular base station may provide an indication that the conditional handover information is available for on-demand broadcast in the broadcast system information that is always provided, but the conditional handover information itself may not be provided in the broadcast system information unless the conditional handover information is requested. At least in some instances, this approach may be beneficial in sparsely populated cells, for which network transmission of conditional handover information may be unnecessary during certain time periods (e.g., when there are few or no wireless devices served by the cell). If a wireless device is served by such a cell, the wireless device may send a request to the cellular base station for the conditional handover information to be broadcast, and the conditional handover information may be received by the wireless device in the broadcast system information, at least in part in response to the request from the wireless device.

[0095] In some embodiments, in such a scenario, the selection of which conditional handover information is broadcast by the cellular base station may be based at least in part on a request from the wireless device. For example, it may be the case that a location-specific preamble configuration is used to request on-demand system information, in which case the cellular base station may be able to map the system information request preamble used by the wireless device to a geographic area (e.g., GNSS coordinates and a corresponding area such as a circle, rectangle, etc.), and may select a candidate cell to broadcast the conditional handover information based at least in part on the location information (e.g., a cell having a service area that overlaps with the location associated with the system information request preamble, or a cell within a specific distance of the location associated with the system information request preamble, as various possibilities).

[0096] At least in some instances, the candidate cell for which the broadcast system information includes the conditional handover information may include one or more other NTN cells associated with the same cellular base station as the NTN cell. Such cells may have substantially similar configurations (e.g., random access channel configurations, radio bearer configurations, mappings of service quality flow indicators (QFI) to data radio bearers (DRBs), etc.), and / or security keys may not change due to handovers to these cells. In some instances, the conditional handover information may include an indication of whether the RRC configuration for conditional handover from the source cell to the target cell is substantially similar (e.g., possibly for each candidate cell for which conditional handover is configured). If the RRC configuration for conditional handover from the source cell to the target cell is the same, it may be the case that the RRC configuration information for the target cell is not provided, for example, because the RRC configuration information for the source cell can be directly reused for the target cell. In some instances, if the RRC configuration for conditional handover from the source cell to the target cell is substantially similar but has some differences, it may be the case that the complete RRC configuration information for the target cell is not provided, but the incremental information indicating the difference between the RRC configurations from the source cell to the target cell is provided in the conditional handover information.

[0097] The conditional handover trigger condition for the candidate cell may include any one of a plurality of possible trigger conditions, which may be configured individually or in a specific combination as an execution condition for conditional handover to a given candidate cell. For example, according to various embodiments, the conditional handover trigger condition for the candidate cell may include any one or all of a time-based trigger condition, a location-based trigger condition, or a radio resource management (RRM) measurement-based trigger condition (e.g., as various possibilities, a reference signal received power (RSRP)-based condition, a reference signal received quality (RSRQ)-based condition, or a signal-to-noise ratio (SNR)-based condition). At least in some instances, the possibility of providing both a time-based trigger condition and a location-based trigger condition may be particularly beneficial for conditional handover from a quasi-geo-fixed NTN source cell to another NTN cell. For example, in such a scenario, the timing of the service area shift may be important for determining the timing of the handover, and at least in some scenarios, if multiple candidate NTN cells have a relatively minimum variance in the RRM measurement, the location of the wireless device may be more important for selecting a good target cell for handover than the RRM measurement.

[0098] The wireless device may evaluate the conditional handover triggering condition to determine whether to trigger a conditional handover for any candidate cell in 806. Evaluating the conditional handover triggering condition may include taking RRM measurements (e.g., based on reference signals transmitted by the serving cell and the target cell, at least as one possibility), maintaining and monitoring system time and / or monitoring wireless device location (e.g., based on global navigation satellite system measurements, at least as one possibility), and comparing the resulting quantities with thresholds specified by the conditional handover triggering condition specified for each configured conditional handover.

[0099] As an example, the execution conditions for conditional switching to a candidate cell may include that all of the time-based trigger conditions, location-based trigger conditions, and RRM measurement-based trigger conditions are satisfied. For example, for a conditional switching to a candidate cell to be triggered, the time may be necessary to be within a certain time window specified by the time-based trigger condition (e.g., between T and T+D, where T is the start time of the trigger condition and D is the duration of the trigger condition), the wireless device may be necessary to be within a certain distance (e.g., a distance threshold specified by the location-based trigger condition) of a reference location (e.g., a reference location associated with the candidate cell), and one or more of the RSRP, RSRQ, and / or SNR of the candidate cell may be necessary to satisfy an RRM-based trigger condition (e.g., better than one or more absolute thresholds and / or better than the corresponding source cell measurement by one or more thresholds specified by the RRM-based trigger condition). In this example, when a combination of trigger conditions configured as execution conditions is met, a conditional switching to the candidate cell is triggered. Thus, according to at least some embodiments, such example execution conditions for conditional switching may trigger transmission of the wireless device to a candidate cell under conditions where the candidate cell can be expected to provide good service to the wireless device and before the current serving cell stops providing service to the wireless device.

[0100] It should be noted that many variations and alternatives of such execution conditions are also possible. As a possible variation, in some instances, the location-based trigger condition may be configured as an additional / separate step to evaluate whether to trigger conditional switching. For example, conditional switching may be configured so that the wireless device checks its location and evaluates the execution condition of the candidate cell only when the location of the wireless device satisfies the location-based trigger condition of the candidate cell (e.g., when the wireless device is within the distance of the reference location of the candidate cell configured by the location-based trigger condition). In other words, in this scenario, at least according to some embodiments, if the wireless device is not within the service area of ​​the candidate cell, the wireless device may not check whether the time or RRM condition for conditional switching to the candidate cell is triggered, but when the wireless device does meet the location-based trigger condition of the candidate cell as well as the time-based trigger condition and the RRM measurement-based trigger condition, the conditional switching may be triggered as in the aforementioned example. Other variations and alternatives are also possible.

[0101] It should be noted that there may be multiple ways to configure the triggering conditions for conditional switching. For example, for a time-based triggering condition for a quasi-terrestrial fixed NTN source cell, an existing parameter indicating when the cell is scheduled to shift the service area may be used as part of the time-based triggering condition. In some instances, the cellular base station may provide an indication of such a "t-Service" parameter for the NTN-based wireless link, which may indicate the time when the cell serving the wireless device stops serving its current service area.

[0102] As one possibility of using such a parameter as part of a time-based trigger condition, the cellular base station may provide an indication of a "D" parameter of the time-based trigger condition, wherein the D parameter indicates a duration for which the time-based trigger condition is triggered. The wireless device may use the t-Service parameter and the D parameter to work backward to determine a "T" parameter of the time-based trigger condition (e.g., such as t-Service-D), which may indicate a start time for which the time-based trigger condition is triggered; thus, in this scenario, the time-based trigger condition may be triggered between time T and time T+D.

[0103] As another possibility of using such a t-Service parameter as part of a time-based trigger condition, the cellular base station may directly provide a "t-Start" parameter for the time-based trigger condition, wherein the t-Start parameter indicates a start time at which the time-based trigger condition is triggered. In this scenario, at least according to some embodiments, the time-based trigger condition may be triggered between the start time (indicated by the t-Start parameter) and the time (indicated by the t-Service parameter) at which the cell serving the wireless device stops serving its current service area.

[0104] It should be noted that in some instances, dedicated (e.g., RRC) signaling can also be used to configure the wireless device with conditional switching information. In order to illustrate this potential coexistence of different ways of signaling conditional switching information, it may be beneficial to provide a framework for determining which conditional switching information to prioritize. For this framework, various options are possible. As a possibility, the situation may be to implicitly prioritize the dedicated conditional switching configuration. Therefore, in this scenario, only when the wireless device is not provided with a dedicated conditional switching configuration, the wireless device can determine to apply the broadcast conditional switching configuration. As another possibility, the situation may be that the dedicated conditional switching configuration can be explicitly prioritized. Therefore, in this scenario, even if a broadcast conditional switching configuration is provided, the wireless device can also determine to apply the dedicated conditional switching configuration based on an explicit indication that the dedicated conditional switching configuration is to be applied. As another possibility, the situation may be that the broadcast conditional switching configuration can be explicitly prioritized. Therefore, in this scenario, the network can broadcast an indication of when the broadcast conditional switching configuration can be used, and even if a dedicated conditional switching configuration is provided, the wireless device can determine to apply the broadcast conditional switching configuration based on an explicit indication that the broadcast conditional switching configuration is to be applied. As yet another possibility, it may be the case that both a dedicated conditional handover configuration and a broadcast conditional handover configuration may be used; for example, for a candidate cell that does not exist in the dedicated conditional handover configuration but exists in the broadcast conditional handover configuration, the broadcast conditional handover configuration may be used, and for a candidate cell that does not exist in the broadcast conditional handover configuration but exists in the dedicated conditional handover configuration, the dedicated conditional handover configuration may be used. In this scenario, for a candidate cell that exists in both the dedicated conditional handover configuration and the broadcast conditional handover configuration, one of the aforementioned frameworks for prioritizing the dedicated conditional handover configuration or the broadcast conditional handover configuration may be used. Note that if the network preference implicitly prioritizes the broadcast conditional handover configuration, then at least according to some embodiments, the network may be able to simply not provide the dedicated conditional handover configuration.

[0105] In 808, the wireless device may perform a handover to the candidate cell when a conditional handover to the candidate cell is triggered. Once a candidate cell for handover has been selected, the cell may also be referred to as a "target cell" for the handover. Performing a handover to the target cell may include performing any of a variety of possible processes to coordinate with the target cell and the source cell to deliver services for the wireless device to the target cell. In some instances, this may include at least performing a random access channel (RACH) process with the target cell.

[0106] If necessary, the conditional handover information received in the broadcast system information may also include RACH configuration information for the conditional handover. Such RACH configuration information may be configured to help facilitate a smoother handover transition from the source cell to the target cell. In some instances, the RACH configuration information may be designed, at least in part, to mitigate the impact of a "RACH storm" scenario that may potentially occur when a quasi-terrestrial fixed NTN cell changes service area, for example, if the change in the service area of ​​the cell will trigger handover of a large number of wireless devices served by the cell. For example, the RACH configuration information may be used to divide the wireless devices served by the source cell into different groups that can use different RACH resources and / or perform handovers at different times, which may potentially reduce the likelihood of RACH failures for wireless devices attempting to perform handovers from the source cell.

[0107] The RACH configuration information may include any of various possible types of information. Some possibilities may include: a set of preambles configured for use with RACH transmissions for conditional handover, a duration for which the wireless device is configured to perform random access after triggering a conditional handover, an indication of which wireless device identification information is used to determine a set of RACH resources that the wireless device may use for RACH transmissions for conditional handover, and / or an indication of RACH opportunities configured for use with RACH transmissions for conditional handover.

[0108] The wireless device identification information used to determine the set of RACH resources that the wireless device can use for RACH transmission for conditional handover may include any of various types of wireless device identification information, such as a cell radio network temporary identifier (C-RNTI), 5G identification information (e.g., 5G shortened temporary mobile subscriber identity or 5G-S-TMSI), or even a random ID generated by the wireless device. RACH resources (e.g., preambles and / or RACH opportunities) may be grouped into different sets, where use of resources in a resource set is limited to wireless devices belonging to the set (e.g., based on their wireless device identification information).

[0109] Thus, at least according to some embodiments, Figure 8The method may be used to provide a framework according to which conditional handoffs may be efficiently and effectively configured in a non-terrestrial wireless communication system, at least in some instances.

[0110] FIG. 9A to FIG. 9B and additional information

[0111] If necessary, FIG. 9A to FIG. 9B and the following additional information illustrate and describe possible Figure 8 However, it should be noted that the exemplary details described in the following section are not intended to limit the present disclosure as a whole: many variations and alternatives to the details provided below are possible and should be considered within the scope of the present disclosure.

[0112] Conditional Handover (CHO) is a feature that can be used to potentially improve the robustness of mobility in cellular communication systems. CHO may include configuring the UE with a handover command and one or more associated conditions to be monitored. When the associated condition becomes true, the UE may be able to execute the stored handover command. This pre-configuration of handover under certain conditions can avoid or reduce the possibility of failure due to failure to receive measurement reports from the UE or handover commands from the network in conventional handover. CHO can be used in terrestrial network deployment scenarios as well as non-terrestrial network deployment scenarios. For NR NTN, conditional trigger conditions related to location and time can be defined. In some embodiments, each execution condition can be configured with up to 2 measurement trigger conditions, and a dedicated RRC configuration can be used to configure the UE to perform CHO. FIG. 9A to FIG. 9B Signal flow aspects of such an exemplary dedicated signaling scheme for configuring conditional handover for a wireless device in accordance with some embodiments are illustrated.

[0113] As shown, in the illustrated scenario, a UE 902 may be attached to a source gNB 904, while a possible target gNB 906 and other possible target gNBs 908 are also deployed in the system. The network may also include an AMF 910 and one or more user plane functions (UPFs) 912. In 914, the UE 902 may exchange user data with the source gNB 904, which may exchange user data with the UPF 912 in 916. In 918, mobility control information may be provided by the AMF 910. In 920, the source gNB 904 may perform measurement control and receive measurement reports from the UE 902. In 922, the source gNB 904 may make a CHO decision, for example, to decide to configure the UE 902 to perform CHO. In 924, the source gNB 904 may provide a handover request to the target gNB 906, and in 926, the source gNB 904 may similarly provide a handover request to other possible target gNBs 908 (e.g., if applicable). In 928 and 930, the target gNB 906 and other possible target gNBs 908 may perform admission control, respectively, and in 932 and 934, the target gNB 906 and other possible target gNBs 908 may provide a handover request confirmation message to the source gNB 904, respectively.

[0114] In 936, the source gNB 904 may provide an RRC reconfiguration message to the UE 902, which may include CHO configuration information. In 938, the UE 902 may provide an RRC reconfiguration complete message to the source gNB 904. In 940, the source gNB 904 may provide an early status transfer to the potential target gNB 908, and in 942, the UPF 912 may transfer user data to the potential target gNB 908 via the source gNB 904. In 944, the UE 902 may evaluate the CHO condition. In 946, the UE may detach from the old cell and may synchronize to the new cell, which in the illustrated example may be the target gNB 906. In 948, the source gNB 904, the UE 902, and the target gNB 906 may perform a CHO handover complete. In 950, the target gNB 906 may indicate to the source gNB 904 that the handover was successful, and in 952, the source gNB 904 may provide a sequence number status transfer to the target gNB 906. In 954, the UPF 912 may transfer user data to the target gNB 906 via the source gNB 904. In 956 and 958, the source gNB 904 may provide a handover cancel indication to the target gNB 906 and any other possible target gNBs 908, respectively, to inform them that the conditional handover configuration is no longer valid. Additional possible subsequent steps that may be used in conjunction with such a CHO operation are illustrated in 3GPP TS 38.300 v.17.0.0 Figure 9.2.3.2.1-1 step 9-12, at least according to some embodiments.

[0115] At least in some instances, NTN cells can be relatively large and can accordingly provide coverage to a potentially large number of UEs. At least in some scenarios, even when the parameters (time and / or location) of the network configuration may be mostly similar or identical for multiple UEs of the NTN cell, the dedicated CHO configuration may also incur a relatively large signaling burden. In addition, satellite mobility may potentially cause a relatively large number of simultaneous (or near-simultaneous) handovers. For example, in some scenarios, a non-geostationary (NGSO) quasi-earth fixed satellite may have a steerable antenna that covers the same area for a certain period of time, and then can change its steering angle to cover a different area for a certain period of time. This transition may interrupt the service link between the satellite (which may also be referred to as the NTN payload in some instances) and the served UE. A large number of UEs forced to perform handovers in a short period of time, such as may occur in this example scenario, may cause an overburdening of the random access channel (RACH) resources used to perform those handovers. At least in some instances, this situation may also be referred to as a "RACH storm" and may result in handover failures of at least some of these UEs.

[0116] Therefore, in at least some embodiments, it may be beneficial to introduce techniques that can reduce the signaling overhead of conditional handovers and / or can help prevent the occurrence of RACH storms. For example, it may be beneficial to provide such techniques for use in NTN cellular systems, where the gNB can be ground-based and potentially multiple different satellites (NTN payloads) can effectively provide cells belonging to the same gNB. Note that satellites may also switch feeder links to associate with different gNBs. Therefore, for a group of satellites belonging to the same gNB, it is possible that when a handover is configured for a UE, the UE RRC configuration in the source cell and the target cell may generally be the same or nearly the same, for example, including RACH configuration, radio bearer configuration, QFI to DRB mapping, etc. Security keys may not change as a result of such a handover.

[0117] In this scenario, CHO configuration information may be broadcast in system information, e.g., instead of or in addition to using dedicated RRC signaling. The broadcast CHO configuration may use similar parameters as in the CHO configuration using dedicated RRC signaling; for example, the gNB may broadcast the MeasConfig and ConditionalReconfiguration IEs corresponding to the candidate cell list along with the associated execution conditions. Conditional triggering conditions based on time and location may be used for the execution conditions. The MeasConfig and ConditionalReconfiguration IEs may be broadcast in an existing system information block (SIB), such as an NTN-specific SIB (e.g., SIB 19) or a new SIB. A new SIB may be used to ensure that the maximum system information size (e.g., 2976 bits as one possibility) is not exceeded. Alternatively, if an existing SIB is used, the SIB may be segmented if necessary.

[0118] To provide at least some configuration flexibility to the network, in some instances the gNB may be able to broadcast an indication of whether the target RRC configuration and the source RRC configuration are substantially similar. In such a scenario, the broadcast CHO configuration may not contain any target RRC reconfiguration information (e.g., if the RRC configurations are the same). As another possibility, incremental signaling may be used to indicate the difference between the source cell RRC configuration and the target cell RRC configuration. In some instances, changes in SIB content related to the CHO configuration do not need to trigger a system information modification notification, e.g., at least for quasi-geo-fixed (NGSO) satellites. For example, due to the amount of time a UE can typically remain connected to such a cell (e.g., several minutes as one possibility), such a notification may be considered unnecessary.

[0119] The network may know the satellite constellation ephemeris. It may be the case that only UEs in a certain geographical location need to be handed over to a specific NTN cell. In some instances, it may be the case that RRM measurements (e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), signal-to-noise ratio (SNR)) do not vary significantly between candidate NTN cells and therefore may not be the most important for identifying the target NTN cell. In NTN deployment scenarios, it may be beneficial to use location and time together as part of a conditional handover trigger. Therefore, at least in some embodiments, it may be beneficial to allow more than 2 trigger conditions for conditional handover.

[0120] For example, in some instances, it may be possible to allow a location-based trigger condition as an additional (third) condition for CHO execution. Thus, both location (e.g., CondEvent D1) and time (CondEvent T1) will be configured together with the RRM measurement (e.g., CondEvent A3, A4, or A5). As another possibility, an additional location-based trigger condition may be configured such that the execution condition for a candidate cell is considered only if the UE is within a certain distance of the reference location of the candidate cell (e.g., CondEvent D2: the distance between the UE and the reference location referenceLocation1 becomes less than a configured threshold Thresh1; where referenceLocation1 represents the reference location of the candidate cell).

[0121] For time-based conditional event triggering, as a possibility, the network can configure the time threshold (T) and duration (D). In this scenario, the event can be considered to be triggered between time T and T+D. Each NTN cell (quasi-geo-fixed case) can also be associated with a parameter "t-Service". This parameter can indicate time information about when a cell provided via the NTN quasi-geo-fixed system will stop serving the area it currently serves. \

[0122] A conditional event may be defined to ensure that CHO is triggered at least D units of time before the UE loses coverage from the serving cell. As an option, the network may configure parameter D for the conditional event. The UE may determine T as T=t-Service–D, and the event may be considered to be triggered between time T and T+D. As another option, the network may configure parameter t-Start for the conditional event, and the event may be considered to be triggered between time t-Start and t-Service. In some instances, the latter option may provide finer granularity (e.g., in some embodiments, the time threshold and t-Service may have units of 10ms, while the duration parameter D may be configured in units of 100ms). The CHO execution condition may be determined by the source gNB.

[0123] In some instances, for example, if a new SIB is used to provide CHO configuration information, the SIB providing the CHO configuration may be an on-demand SIB. This provision may be useful in sparsely populated cells, where the network transmission requirements may be reduced during times when the SIB providing the CHO configuration does not need to be sent. The network may be able to indicate the presence of broadcast CHO in another SIB (e.g., SIB 19 as one possibility), for example as part of SchedulingInfo. The UE may then initiate on-demand delivery of the new SIB.

[0124] In some examples, location specific preamble configurations may be used for on-demand SIB based CHO configuration. The SI request preamble may be mapped to a geographic area with shape specific parameters (e.g., GNSS coordinates and corresponding area (circular, rectangular, etc.)). By mapping the preamble to a geographic area, the network may be able to determine candidate cells to be considered for broadcast CHO, at least according to some embodiments.

[0125] As previously noted herein, such a broadcast CHO configuration may be implemented together with a CHO configuration using dedicated signaling. It may be useful to provide a mechanism for the network to control when the UE applies such a broadcast CHO configuration, and also to manage how the broadcast CHO configuration and the dedicated CHO configuration can coexist. As a first option, the dedicated CHO configuration may be implicitly prioritized. Thus, at least according to some embodiments, the UE may apply the broadcast CHO configuration only if the UE is not provided with a dedicated CHO configuration in such a scenario. As a second option, the dedicated CHO configuration may be explicitly prioritized. Thus, at least according to some embodiments, even if the broadcast CHO configuration is available in such a scenario, the UE may apply the dedicated CHO configuration based on a displayed indication that the dedicated CHO configuration is to be applied. As a third option, the broadcast CHO configuration may be explicitly prioritized. Therefore, at least according to some embodiments, the network may broadcast an indication of when broadcast CHO may be used, and the UE may apply the broadcast CHO configuration even if a dedicated CHO configuration is provided in such a scenario. As yet another possibility, both the dedicated CHO configuration and the broadcast CHO configuration may be used, such that for candidate cells that do not exist in the dedicated CHO configuration but exist in the broadcast CHO configuration, the broadcast CHO configuration may be used, and for candidate cells that do not exist in the broadcast CHO configuration but exist in the dedicated CHO configuration, the dedicated CHO configuration may be used, and for candidate cells that exist in both the broadcast CHO configuration and the dedicated CHO configuration, one of the first option, the second option, or the third option described previously may be used to determine which CHO configuration to use. Note that it may be the case that the option to implicitly prioritize the broadcast CHO configuration may not be needed, because in such a scenario, the network may be able to not provide the dedicated CHO configuration.

[0126] As noted previously herein, having a large number of UEs perform handovers simultaneously may result in RACH storms. This scenario is particularly likely to occur when the UEs follow the same broadcast CHO configuration. Therefore, it may be beneficial to provide techniques for prioritizing and randomizing RACH attempts made by UEs for handovers in order to reduce the likelihood of RACH storms and widespread handover failures. The system information used to broadcast CHO configuration information may also include RACH configuration information that may be used for CHO purposes, which may be used to mitigate the likelihood of the broadcast CHO configuration causing a RACH storm. For example, as one possibility, the RACH configuration may include: a set of preambles to be used for RACH purposes, a duration (“T”) during which the UE is required to perform random access after a CHO execution condition is triggered, and a time duration (“T”) during which the UE is required to perform random access. exec”), an indication of what identity the UE should use (e.g., for randomization purposes), and an indication of which RACH opportunities are available for broadcasting CHO (e.g., as a PRACH configuration index). Variations on this RACH configuration information (such as including additional RACH configuration information or alternative RACH configuration information) are also possible. According to some embodiments, if such RACH configuration is not provided in the system information, the UE may perform RACH in a normal or default manner.

[0127] Therefore, depending on the RACH configuration for broadcast CHO, the UE may be able to randomly select both the RACH preamble and the RACH timing to be used. In some embodiments, it may be assumed that all NTN cells belonging to a certain gNB use the same RACH configuration for broadcast CHO. exec The RACH opportunity is randomly selected from the available RACH opportunities within the RACH resource pool. To manage the possibility of collision, the RACH resources can be grouped into different sets, and only UEs belonging to a set can use RACH resources (preamble and / or RACH opportunity) for the set. Several parameters can be used to classify UEs into different sets; for example, according to various embodiments, C-RNTI, 5G identity (e.g., 5G-S-TMSI) and / or a random ID generated by the UE can be used.

[0128] In the following, further exemplary embodiments are provided.

[0129] A set of embodiments may include a method comprising: by a wireless device: establishing a non-terrestrial network (NTN)-based wireless link with a cellular base station; receiving conditional switching information in broadcast system information, wherein the conditional switching information indicates one or more conditional switching triggering conditions for one or more candidate cells; evaluating the one or more conditional switching triggering conditions to determine whether to trigger a conditional switching for the one or more candidate cells; and performing a switching to the candidate cell when a conditional switching to the candidate cell is triggered.

[0130] According to some embodiments, the conditional handover information includes an indication of whether a radio resource control (RRC) configuration for the conditional handover from the source cell to the target cell is substantially similar.

[0131] According to some embodiments, the conditional handover information also includes incremental information indicating the difference between the RRC configurations used for the conditional handover from the source cell to the target cell.

[0132] According to some embodiments, the one or more conditional handover trigger conditions include one or more of: a time-based trigger condition; a location-based trigger condition; or a radio resource management (RRM) measurement-based trigger condition.

[0133] According to some embodiments, the method also includes: determining a location of the wireless device, wherein the one or more conditional handover triggering conditions are evaluated to determine whether to trigger a conditional handover for the one or more candidate cells based at least in part on the location of the wireless device.

[0134] According to some embodiments, the one or more conditional switching trigger conditions include at least a time-based trigger condition, wherein the method further includes: receiving an indication of a "t-Service" parameter of the NTN-based wireless link, wherein the t-Service parameter indicates the time when the cell serving the wireless device stops serving its current service area; receiving a "D" parameter of the time-based trigger condition, wherein the D parameter indicates the duration for which the time-based trigger condition is triggered; determining a "T" parameter of the time-based trigger condition, wherein the T parameter indicates the start time when the time-based trigger condition is triggered, wherein the T parameter is determined as t-Service–D; wherein the time-based trigger condition is triggered between time T and time T+D.

[0135] According to some embodiments, the one or more conditional switching trigger conditions include at least a time-based trigger condition, wherein the method further includes: receiving an indication of a "t-Service" parameter of the NTN-based wireless link, wherein the t-Service parameter indicates the time when the cell serving the wireless device stops serving its current service area; and receiving a "t-Start" parameter of the time-based trigger condition, wherein the t-Start parameter indicates the start time at which the time-based trigger condition is triggered, wherein the time-based trigger condition is triggered between the start time indicated by the t-Start parameter and the time when the cell serving the wireless device stops serving its current service area indicated by the t-Service parameter.

[0136] According to some embodiments, the method further comprises: receiving an indication in the broadcast system information that the conditional switching information is available for on-demand broadcast; and sending a request to the cellular base station for the conditional switching information to be broadcast.

[0137] According to some embodiments, the method further includes: receiving conditional switching information in dedicated signaling; and determining whether to prioritize the conditional switching information received in the dedicated signaling or to prioritize the conditional switching information received in the broadcast system information.

[0138] According to some embodiments, the conditional switching information received in the broadcast system information also includes random access channel (RACH) configuration information for conditional switching, wherein the RACH configuration information for conditional switching includes one or more of the following: a set of preamble codes configured for use with RACH transmission for conditional switching; a duration for which the wireless device is configured to perform random access after triggering the conditional switching; an indication of which wireless device identification information is used to determine a set of RACH resources that the wireless device can use for RACH transmission for conditional switching; or an indication of a RACH opportunity configured for use with RACH transmission for conditional switching.

[0139] Another set of embodiments may include a wireless device comprising: one or more processors; and a memory having instructions stored thereon, which when executed by the one or more processors perform the steps of any of the methods described in the aforementioned embodiments.

[0140] Yet another set of embodiments may include a computer program product comprising computer instructions that, when executed by one or more processors, perform the steps of any of the methods described in the preceding embodiments.

[0141] Another set of embodiments may include a method comprising: by a cellular base station: establishing a non-terrestrial network (NTN)-based wireless link with a wireless device; and providing conditional switching information in broadcast system information, wherein the conditional switching information indicates one or more conditional switching triggering conditions that trigger switching to one or more candidate cells.

[0142] According to some embodiments, the conditional switching information includes an indication that the radio resource control (RRC) configuration for conditional switching from the source cell to the candidate cell is substantially similar, wherein the conditional switching information also includes incremental information indicating the difference between the RRC configurations for conditional switching from the source cell to the candidate cell.

[0143] According to some embodiments, the one or more conditional handover trigger conditions include: a time-based trigger condition; a location-based trigger condition; and a radio resource management (RRM) measurement-based trigger condition.

[0144] According to some embodiments, the method also includes: providing an indication in the broadcast system information that the conditional switching information can be used for on-demand broadcasting; and receiving a request for the conditional switching information to be broadcast from the wireless device, wherein the conditional switching information is provided in the broadcast system information based at least in part on the request for the conditional switching information to be broadcast.

[0145] According to some embodiments, the request for the conditional handover information to be broadcast indicates location information of the wireless device, wherein a candidate cell is selected for the conditional handover information based at least in part on the location information of the wireless device.

[0146] According to some embodiments, the conditional handover information provided in the broadcast system information also includes random access channel (RACH) configuration information for conditional handover.

[0147] Another set of embodiments may include a cellular base station comprising: one or more processors; and a memory having instructions stored thereon, which, when executed by the one or more processors, perform the steps of any of the methods described in the aforementioned embodiments.

[0148] Yet another set of embodiments may include a computer program product comprising computer instructions that, when executed by one or more processors, perform the steps of any of the methods described in the preceding embodiments.

[0149] Yet another example embodiment may include a method comprising: performing, by a wireless device, any or all of the foregoing examples.

[0150] Another exemplary embodiment may include a device comprising: an antenna; a radio component coupled to the antenna; and a processing element operably coupled to the radio component, wherein the device is configured to implement any or all portions of the foregoing examples.

[0151] Another set of exemplary embodiments may include a non-transitory computer-accessible storage medium including program instructions that, when executed at a device, cause the device to implement any or all portions of any of the foregoing examples.

[0152] Still another set of exemplary embodiments may include a computer program comprising instructions for performing any or all portions of any of the foregoing examples.

[0153] Yet another set of exemplary embodiments may include an apparatus comprising means for performing any or all elements of any of the foregoing examples.

[0154] Another exemplary set of embodiments may include an apparatus comprising a processing element configured to cause a wireless device to perform any or all elements of any of the foregoing examples.

[0155] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of the authorized use should be clearly stated to users.

[0156] By interpreting each message / signal X received by a user equipment (UE) in the downlink as a message / signal X sent by the base station, and interpreting each message / signal Y sent by the UE in the uplink as a message / signal Y received by the base station, any of the methods for operating a UE described herein may become the basis for the corresponding method for operating a base station.

[0157] The embodiments of the present disclosure may be implemented in any of a variety of forms. For example, in some embodiments, the subject matter may be implemented as a computer-implemented method, a computer-readable storage medium, or a computer system. In other embodiments, one or more custom-designed hardware devices such as ASICs may be used to implement the subject matter. In other embodiments, one or more programmable hardware elements such as FPGAs may be used to implement the subject matter.

[0158] In some embodiments, a non-transitory computer-readable storage medium (e.g., a non-transitory storage element) may be configured to store program instructions and / or data, wherein if the program instructions are executed by a computer system, the computer system is caused to perform a method, such as any method implementation of the method embodiments described herein, or any combination of the method implementations described herein, or any subset of any method implementation of the method embodiments described herein, or any combination of such subsets.

[0159] In some embodiments, a device (e.g., a UE) may be configured to include a processor (or a group of processors) and a memory medium (or a memory element), wherein the memory medium stores program instructions, wherein the processor is configured to read and execute these program instructions from the memory medium, wherein these program instructions are executable to implement any method implementation in the various method implementations described herein (or any combination of the method implementations described herein, or any subset of any method implementation in the method implementations described herein, or any combination of such subsets). The device may be implemented in any of various forms.

[0160] Although the above embodiments have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to include all such variations and modifications.

Claims

1. A method, comprising: By wireless device: Establishing a non-terrestrial network (NTN) based wireless link with a cellular base station; receiving conditional handover information in the broadcast system information, wherein the conditional handover information indicates one or more conditional handover triggering conditions for one or more candidate cells; evaluating the one or more conditional handover triggering conditions to determine whether to trigger conditional handover for the one or more candidate cells; as well as When a conditional handover to a candidate cell is triggered, a handover to the candidate cell is performed.

2. The method according to claim 1, The conditional handover information includes an indication of whether a radio resource control (RRC) configuration for conditional handover from a source cell to a target cell is substantially similar.

3. The method according to claim 2, The conditional handover information further includes incremental information indicating a difference between RRC configurations used for conditional handover from the source cell to the target cell.

4. The method according to any one of the preceding claims, wherein the one or more conditional switching trigger conditions include one or more of the following: Time-based trigger conditions; Location-based triggers; or Trigger conditions based on Radio Resource Management (RRM) measurements.

5. The method according to any one of the preceding claims, wherein the method further comprises: determining a location of the wireless device, The one or more conditional handover triggering conditions are evaluated to determine whether to trigger a conditional handover for the one or more candidate cells based at least in part on the location of the wireless device.

6. The method according to any one of the preceding claims, wherein the one or more conditional switching trigger conditions include at least a time-based trigger condition, wherein the method further comprises: receiving an indication of a "t-Service" parameter for the NTN-based radio link, wherein the t-Service parameter indicates a time at which a cell serving the wireless device stops serving its current service area; receiving a "D" parameter of the time-based trigger condition, wherein the D parameter indicates a duration for which the time-based trigger condition is triggered; as well as Determine a "T" parameter of the time-based trigger condition, wherein the T parameter indicates a start time when the time-based trigger condition is triggered, wherein the T parameter is determined as t-Service-D; The time-based trigger condition is triggered between time T and time T+D.

7. The method according to any one of the preceding claims, wherein the one or more conditional switching trigger conditions include at least a time-based trigger condition, wherein the method further comprises: receiving an indication of a "t-Service" parameter for the NTN-based radio link, wherein the t-Service parameter indicates a time at which a cell serving the wireless device stops serving its current service area; as well as receiving a "t-Start" parameter of the time-based trigger condition, wherein the t-Start parameter indicates a start time when the time-based trigger condition is triggered, The time-based trigger condition is triggered between the start time indicated by the t-Start parameter and the time indicated by the t-Service parameter when the cell serving the wireless device stops serving its current service area.

8. The method according to any one of the preceding claims, wherein the method further comprises: receiving, in the broadcast system information, an indication that the conditional switching information can be used for on-demand broadcasting; as well as A request is sent to the cellular base station for the conditional handoff information to be broadcast.

9. The method according to any one of the preceding claims, wherein the method further comprises: receiving conditional switching information in dedicated signaling; as well as A determination is made whether to prioritize the conditional switching information received in dedicated signaling or to prioritize the conditional switching information received in broadcast system information.

10. The method according to any one of the preceding claims, The conditional switching information received in the broadcast system information further includes random access channel (RACH) configuration information for conditional switching, wherein the RACH configuration information for conditional switching includes one or more of the following items: A set of preambles configured for use in RACH transmission for conditional switching; a duration for which the wireless device is configured to perform random access after a trigger condition switch; an indication of which wireless device identification information is used to determine a set of RACH resources that the wireless device can use for conditional handover RACH transmissions; or An indication of the RACH opportunities configured for use with conditionally switched RACH transmissions.

11. A wireless device, comprising: one or more processors; as well as A memory having instructions stored thereon, which when executed by the one or more processors perform the steps of any one of the methods of claims 1 to 10.

12. A computer program product comprising computer instructions which, when executed by one or more processors, perform the steps of any of the methods of claims 1 to 10.

13. A method comprising: By cellular base station: Establishing a non-terrestrial network (NTN) based wireless link with the wireless device; as well as Conditional handover information is provided in the broadcast system information, wherein the conditional handover information indicates one or more conditional handover triggering conditions that trigger handover to one or more candidate cells.

14. The method according to claim 13, wherein the conditional handover information includes an indication that a radio resource control (RRC) configuration for conditional handover from the source cell to the candidate cell is substantially similar, The conditional handover information further includes incremental information indicating a difference between RRC configurations used for conditional handover from the source cell to the candidate cell.

15. The method according to any one of claims 13 to 14, wherein the one or more conditional switching trigger conditions include: Time-based trigger conditions; Location-based triggers; as well as Trigger conditions based on Radio Resource Management (RRM) measurements.

16. The method according to any one of claims 13 to 15, wherein the method further comprises: Providing, in the broadcast system information, an indication that the conditional switching information can be used for on-demand broadcasting; as well as receiving a request from the wireless device for the conditional switching information to be broadcast, Wherein the conditional switching information is provided in the broadcast system information based at least in part on the request for the conditional switching information to be broadcast.

17. The method according to claim 16, wherein the request for the conditional handoff information to be broadcast indicates location information of the wireless device, Wherein a candidate cell is selected for the conditional handover information based at least in part on the location information of the wireless device.

18. The method according to any one of claims 13 to 17, wherein the conditional handover information provided in the broadcast system information further comprises random access channel (RACH) configuration information for conditional handover.

19. A cellular base station, comprising: one or more processors; as well as A memory having instructions stored thereon which, when executed by the one or more processors, perform the steps of any of the methods of claims 13 to 18.

20. A computer program product comprising computer instructions which, when executed by one or more processors, perform the steps of any of the methods according to claims 13 to 18.

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