Method and apparatus for mobility in a mobile network

Abstract

A method and apparatus are provided for receiving a broadcast configuration indicating when a change in RAN function termination occurs, e.g., by a timer value. The broadcast configuration may be received from satellites, soft airships, or other mobile transmitters. A dedicated configuration may also be received from the serving cell. The dedicated configuration may include an indication of a preamble, a transient configuration, and layer 2 behavior. If a WTRU detects a change in RAN function termination, the WTRU may suspend any uplink data transmission, apply a transient configuration, and transmit the preamble to a target cell. The WTRU may synchronize with the target cell and apply the layer 2 behavior.

Description

[0001] This divisional application is a divisional application with application date of October 30, 2019, application number 201980083446.6, and invention name “Method and device for mobility in mobile networks”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims protection of the rights and interests of U.S. Provisional Application No. 62 / 840,973, filed on April 30, 2019, U.S. Provisional Application No. 62 / 824,102, filed on March 26, 2019, and U.S. Provisional Application No. 62 / 752,722, filed on October 30, 2018, the contents of each of the above applications are incorporated herein by reference.

[0004] summary

[0005] A method and apparatus for receiving a broadcast configuration that indicates when a change in radio access network (RAN) function termination occurs, for example by providing a timer value. The broadcast configuration may be received from a satellite, blimp, or other mobile transmitter. A dedicated configuration may also be received from a serving cell. The dedicated configuration may include a preamble, a transient configuration, and an indication of layer 2 behavior. If a wireless transmit / receive unit (WTRU) detects a change in RAN function termination, the WTRU may suspend any uplink data transmission, apply the transient configuration, and transmit the preamble to a target cell. The WTRU may synchronize with the target cell and apply the layer 2 behavior. Background Art

[0006] Next generation air interfaces, such as advanced long term evolution (LTE) Pro and new radio (NR), can support a wide range of use cases with different service requirements. Examples of such use cases may include low overhead low data rate power efficient services for massive machine type communications (mMTC), ultra-reliable low latency (URLLC) services, and high data rate mobile broadband services (eMBB). Such use cases may be supported for wireless transmit / receive units (WTRUs) with different capabilities, such as low power low bandwidth WTRUs, WTRUs capable of operating over very wide bandwidths (e.g., 80 MHz bandwidth), and WTRUs supporting high frequencies greater than 6 GHz in various mobility scenarios. Such mobility scenarios include fixed, stationary, and high-speed train mobility scenarios. Such use cases may employ an architecture that is flexible enough to accommodate various deployment scenarios, such as standalone, non-standalone with help from different air interfaces, centralized, virtualized, and distributed over ideal or non-ideal backhaul scenarios.

[0007] As described herein, a network may refer to one or more next generation Node Bs (gNode Bs or gNBs), which may be associated with one or more transmit / receive points (TRPs) or other nodes in a radio access network (RAN). An example network is a non-terrestrial network (NTN), which may facilitate the development of 5G services in unserved areas (such as isolated remote areas, rural areas, and ships in the ocean). These example services may be provided to WTRUs that may not be covered by terrestrial 5G networks. In some cases, the NTN may be used to upgrade the performance of terrestrial networks in underserved areas in a cost-effective manner. The NTN may also be used to enhance 5G service reliability, ensure service availability, and provide scalability for 5G deployments (e.g., when a gNB or gateway is within range of the WTRU). Summary of the invention

[0008] A method and apparatus are provided for receiving a broadcast configuration indicating when a change in RAN function termination occurs (e.g., via a timer value). The broadcast configuration may be received from a satellite, blimp, or other mobile transmitter. A dedicated configuration may also be received from a serving cell. The dedicated configuration may include a preamble, a transient configuration, and an indication of a layer 2 behavior. If a WTRU detects a change in RAN function termination, the WTRU may suspend any uplink data transmission, apply the transient configuration, and transmit the preamble to a target cell. The WTRU may synchronize with the target cell and apply the layer 2 behavior. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention may be understood in more detail from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0010] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented;

[0011] Figure 1B is a diagram showing that according to an embodiment, Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) used in the communication system shown;

[0012] Figure 1C is a diagram showing that according to an embodiment, Figure 1A A system diagram of an example radio access network (RAN) and an example core network (CN) used within a communication system as shown in FIG.

[0013] Figure 1D is a diagram showing that according to an embodiment, Figure 1A A system diagram of another example RAN and another example CN used within the communication system shown in;

[0014] Figure 2 is a network diagram illustrating different types of architectures that may be used for a non-terrestrial network (NTN) based on the division of RAN functionality between ground units and satellites;

[0015] Figure 3 is a diagram illustrating different example implementations for satellites having different spot beams, synchronization signal blocks (SSBs), and physical layer cell identity (PCI) relationships;

[0016] Figure 4 is a diagram showing an example of feeder link switching for a non-geostationary (non-GEO) satellite;

[0017] Figure 5 is a network diagram of an example of non-transparent satellite mobility;

[0018] Figure 6 is a network diagram of an example of cell-transparent satellite mobility;

[0019] Figure 7 is a network diagram illustrating location-based measurement object selection;

[0020] Figure 8 is a network diagram illustrating a transient configuration associated with a mobility event;

[0021] Fig. 9 is a diagram showing an example of an approximate WTRU position derived from implicit measurements and offsets; and

[0022] Fig.10 is a flow chart illustrating an example method performed by a WTRU during a handover. DETAILED DESCRIPTION

[0023] Figure 1A 1 is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content by sharing system resources including wireless bandwidth. For example, the communication system 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0024] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104, a CN 106, a public switched telephone network (PSTN) 108, the Internet 110 and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network components. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to transmit and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or MiFi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0025] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B (eNB), a Home Node B, a Home eNode B, a gNB, an NR Node B, a site controller, an access point (AP), a wireless router, and the like. While each of the base stations 114a, 114b is depicted as a single component, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network components.

[0026] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network components (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, etc. The base station 114a and / or the base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Therefore, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology, and may use multiple transceivers for each sector of the cell. For example, beamforming may be used to send and / or receive signals in a desired spatial direction.

[0027] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d via an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0028] More specifically, as described above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 116. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0029] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0030] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0031] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may together implement LTE radio access and NR radio access, for example using dual connectivity (DC) principles. Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations, such as eNBs and gNBs.

[0032] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement wireless technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, International Standard 2000 (IS-2000), International Standard 95 (IS-95), International Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE), GSM EDGE (GERAN), etc.

[0033] Figure 1AThe base station 114b in the example may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a residence, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement radio technologies such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement radio technologies such as IEEE 802.15 to establish a wireless personal area network (WPAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. Figure 1A As shown, the base station 114b may be directly connected to the Internet 110. Therefore, the base station 114b may not need to access the Internet 110 via the CN 106.

[0034] The RAN 104 may be in communication with the CN 106, which may be any type of network that provides voice, data, applications, and / or voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions (e.g., user authentication). Although Figure 1A Although not shown, it will be appreciated that the RAN 104 and / or CN 106 may be in direct or indirect communication with other RANs that employ the same RAT or a different RAT as the RAN 104. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also be in communication with another RAN (not shown) employing GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0035] The CN 106 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may use the same RAT as the RAN 104 or a different RAT.

[0036] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114A, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0037] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keyboard 126, a display / touchpad 128, non-removable memory 130, a removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0038] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0039] The transmit / receive component 122 may be configured to transmit or receive signals to or from a base station (e.g., base station 114a) via an air interface 116. For example, in one embodiment, the transmit / receive component 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive component 122 may be a transmitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive component 122 may be configured to transmit and / or receive both RF and optical signals. It should be understood that the transmit / receive component 122 may be configured to transmit and / or receive any combination of wireless signals.

[0040] Although the transmit / receive element 122 is Figure 1B Although depicted as a single component in the embodiment, the WTRU 102 may include any number of transmit / receive components 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive components 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0041] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As described above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs (e.g., NR and IEEE 802.11).

[0042] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keyboard 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0043] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0044] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more neighboring base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0045] The processor 118 may also be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functions, and / or wired or wireless connections. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth® module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripherals 138 may include one or more sensors. The sensor may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0046] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., signals associated with specific subframes for downlink (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit 139 that reduces and / or substantially eliminates self-interference by means of hardware (e.g., chokes) or by signal processing by a processor (e.g., a separate processor (not shown) or by the processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio that transmits and receives some or all signals (e.g., signals associated with specific subframes for UL (e.g., for transmission) or downlink (e.g., for reception)).

[0047] Figure 1C 1 is a system diagram showing the RAN 104 and the CN 106 in accordance with an embodiment. As described above, the RAN 104 may employ an E-UTRA radio technology and communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0048] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. Each of the eNode-Bs 160a, 160b, 160c may include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0049] Each of the eNodeBs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. Figure 1C As shown in FIG. , the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0050] Figure 1C The CN 106 shown in FIG. 1 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing components is depicted as part of the CN 106, it will be understood that any of these components may be owned and / or operated by an entity other than a CN operator.

[0051] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, carrier activation / deactivation, selecting a particular SGW during an initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other wireless technologies, such as GSM and / or WCDMA.

[0052] The SGW 164 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-eNode-B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the contexts of the WTRUs 102a, 102b, 102c, and the like.

[0053] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0054] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0055] Although the WTRU Figures 1A-1D Although described as a wireless terminal, it is contemplated that in certain representative embodiments such a terminal may use (eg, temporarily or permanently) a wired communications interface with a communications network.

[0056] In a representative embodiment, other network 112 may be a WLAN.

[0057] A WLAN in an infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STAs) associated with the AP. The AP may access or dock to a distribution system (DS) or send services into and / or out of another type of wired / wireless network carrying the BSS. Services initiated from outside the BSS and destined for the STA may be reached through the AP and may be delivered to the STA. Services initiated from the STA and destined for a destination outside the BSS may be sent to the AP to be delivered to the corresponding destination. Services between STAs within the BSS may be sent through the AP, for example, where the source STA may send services to the AP, and the AP may deliver services to the destination STA. Services between STAs within the BSS may be considered and / or referred to as point-to-point services. The point-to-point services may be sent between the source STA and the destination STA (e.g., directly between the source STA and the destination STA) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs (eg, all STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0058] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP can transmit beacons on a fixed channel, such as a primary channel. The primary channel can be a fixed width (e.g., a 20MHz wide bandwidth) or a width dynamically set via signaling. The primary channel can be a working channel of the BSS and can be used by the STA to establish a connection with the AP. In certain representative embodiments, such as in an 802.11 system, carrier sensing multiple access (CSMA / CA) with collision avoidance can be implemented. For CSMA / CA, STAs including the AP (e.g., each STA) can sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a specific STA, the specific STA can back off. One STA (e.g., only one station) can transmit at any given time in a given BSS.

[0059] High throughput (HT) STAs may communicate using 40 MHz wide channels, for example, by combining a primary 20 MHz channel with adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0060] Very High Throughput (VHT) STA can support channels with a width of 20MHz, 40MHz, 80MHz and / or 160MHz. 40MHz and / or 80 MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80 MHz channels, which can be referred to as an 80+80 configuration. For the 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be subjected to inverse fast Fourier transform (IFFT) processing and time domain processing, respectively. The stream can be mapped onto two 80 MHz channels, and the data can be transmitted by the transmitting STA. At the receiver of the receiving STA, the operation of the above 80+80 configuration can be opposite, and the combined data can be sent to the medium access control (MAC).

[0061] The operating mode below 1 GHz is supported by 802.11af and 802.11ah. The channel operating bandwidth and carrier are reduced in 802.11af and 802.11ah relative to the channel operating bandwidth and carrier used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support metering type control / machine type communication, such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, for example, limited capabilities including support for certain and / or limited bandwidths (e.g., only support for certain and / or limited bandwidths). MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0062] A WLAN system that can support multiple channels and channel bandwidths (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah) includes a channel that can be designated as a primary channel. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by the STA among all STAs operating in the BSS, and the STA supports the minimum bandwidth operating mode. In the example of 802.11ah, for a STA (e.g., an MTC-type device) that supports (e.g., only supports) a 1 MHz mode, the primary channel may be 1 MHz wide, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, because a STA (which only supports a 1 MHz operating mode) transmits to the AP, even if most of the bands in the band remain idle and available, the overall available band may be considered busy.

[0063] In the United States, the available frequency band that 802.11ah can use is from 902 MHz to 928 MHz. In South Korea, the available frequency band is from 917.5 MHz to 923.5 MHz. In Japan, the available frequency band is from 916.5 MHz to 927.5 MHz. Depending on the country code, the total bandwidth available for 802.11ah is 6 MHz to 26 MHz.

[0064] Figure 1D 1 is a system diagram showing the RAN 104 and the CN 106 according to an embodiment. As described above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using NR radio technology. The RAN 104 may also communicate with the CN 106.

[0065] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with the embodiment. Each of the gNBs 180a, 180b, 180c may include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation techniques. For example, the gNB 180a may transmit multiple component carriers (not shown) to the WTRU 102a. A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) techniques. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and gNB 180b (and / or gNB 180c).

[0066] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with a scalable parameter configuration (numerology) reduction. For example, the OFDM symbol spacing and / or the OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or subframes or transmission time intervals (TTIs) having various or scalable reduced lengths (e.g., containing different numbers of OFDM symbols and / or continuously varying absolute time lengths).

[0067] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without also accessing other RANs (e.g., the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchors. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNBs 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more of the gNBs 180a, 180b, 180c and one or more of the eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-B 160a, 160b, 160c may serve as mobility anchor points for the WTRUs 102a, 102b, 102c and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0068] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support network slicing, dual connectivity, interworking between NR and E-UTRA, route user plane data to a user plane function (UPF) 184a, 184b, route control plane information to an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0069] Figure 1DThe CN 106 shown in FIG. 1 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although each of the foregoing components is depicted as part of the CN 106, it will be understood that any of these components may be owned and / or operated by an entity other than a CN operator.

[0070] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of NAS signaling, mobility management, and the like. The AMF 182a, 182b may use network slicing to customize the CN support of the WTRU 102a, 102b, 102c according to the type of services used by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and / or types of content. The AMF 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) employing other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0071] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0072] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

[0073] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) or may communicate with an IP gateway that acts as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In an embodiment, the WTRUs 102a, 102b, 102c may be connected to a local DN 185a, 185b via an N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the data network (DN) 185a, 185b, and through the UPF 184a, 184b.

[0074] Given that Figures 1A-1D and Figures 1A-1D In accordance with the corresponding description of the present invention, one or more or all of the functions described herein with respect to one or more of the following items may be performed by one or more simulation devices (not shown): WTRU 102a-d, base station 114a-b, eNodeB 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-ab, UPF184 ab, SMF 183a-b, DN185 ab and / or any other device (one or more) described herein. The simulation device may be one or more devices configured to simulate one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0075] The simulation device can be designed to implement one or more tests of other devices in a laboratory environment and / or an operator network environment. For example, one or more simulation devices can perform one or more or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. One or more simulation devices can perform one or more or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device can be directly coupled to another device for testing purposes and / or perform tests using over-the-air wireless communications.

[0076] One or more simulation devices may perform one or more functions (including all functions) without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device may be used in a test scenario in a test lab and / or a non-deployed (e.g., testing) wired and / or wireless communication network to enable testing of one or more components. The one or more simulation devices may be test devices. The simulation device may transmit and / or receive data using direct RF coupling and / or wireless communication with the aid of RF circuits (e.g., which may include one or more antennas).

[0077] For air interfaces (such as the next generation air interfaces described above), beamforming can be used to compensate for increased path loss at higher frequencies (e.g., frequencies greater than 6 GHz). A larger number of antenna elements can be used to achieve higher beamforming gain. Analog and / or hybrid beamforming can be used to reduce implementation cost by reducing the number of RF chains, and beams multiplexed in time can be used.

[0078] Satellites may operate in a bent-pipe fashion and may employ a bent-pipe architecture. In this way, the satellite may act as a radio relay station and may not be configured to process higher network layers. Instead, the satellite may relay the signal back to Earth, i.e., send the same signal back only with amplification and / or a change in frequency or frequency band. Alternatively, the satellite may incorporate higher-layer onboard processing and may perform demodulation, decoding, re-encoding, and modulation prior to transmission.

[0079] Figure 22 is a network diagram illustrating three configuration partitioning architectures 200, 230, 260 that may be used for NTN. The three configuration partitioning architectures 200, 230, 260 are distinguished based on the partitioning of RAN functions between ground units and satellites. Partition architecture 1 200 illustrates a next generation (NG) RAN architecture in NTN with a bent pipe payload. In this example, a WTRU 202, a network node 204, or a satellite 206 may communicate with an NTN NG radio access network 210 via an NR-Uu interface 208. The NTN NG radio access network 210 may include a radio frequency bent pipe type satellite 212 and a blimp 214. The NR-Uu 216 may couple the radio frequency bent pipe type satellite 212 and the blimp 214 to an NTN remote radio unit 218 and a gNB 220. The gNB may be coupled to a 5G CN via an N1 / 2 / 3 interface 222. The 5G CN 224 may interface with a data network 228 via an N6 interface 226.

[0080] Partition 2 230 illustrates an NG RAN architecture in an NTN with a gNB distributed unit (DU) handling payload. In partition 2 230 and partition 3 260, a satellite radio interface (SRI) may be employed between satellite units and ground-based units. In the partition 2 230 example, a WTRU 232, a network node 234, or a satellite 236 may communicate with an NTN NG radio access network 240 via an NR-Uu interface 238. The NTN NG radio access network 240 may include a gNB DU 242 and a blimp 244. An F1 interface on an SRI 246 may couple the gNB DU 242 and the blimp 244 to an NTN remote radio unit 248 and a gNB centralized unit (CU) 250. The F1 interface may be used as a functional partitioning interface, for example, to provide a partitioned interface between the CU and DU of an eNB. The gNB CU 250 may be coupled to a 5G CN 254 ​​via an N1 / 2 / 3 interface 252. The 5G CN 254 ​​may interface with (eg, provide access to) the data network 258 via the N6 interface 256 .

[0081] Partition 3 260 illustrates an NG RAN architecture with gNB processing payload in NTN. In this example, an NTN NG radio access network 270 in the NTN includes a gNB configured to process payload. In the example of partition 3 260, a WTRU 262, a network node 264, or a satellite 266 may communicate with the NTN NG radio access network 270 via an NR-Uu interface 268. The NTN NG radio access network 270 may include a gNB 272 and a blimp 274. The N1 / 2 / 3 on the SRI 276 may couple the gNB 272 and the blimp 274 to an NTN remote radio unit 278. The NTN remote radio unit 278 may couple with a 5G CN 282 via an N1 / 2 / 3 interface 280. The 5G CN 282 may interface with a data network 286 via an N6 interface 284.

[0082] A satellite may generate several beams, called spot beams, to cover its service area defined by its field of view, called a coverage area. Different implementations may be used based on the relationship between the spot beams, synchronization signal blocks (SSBs), and physical layer cell identities (PCIs) of one or more satellites.

[0083] Figure 3 300 ; PCI 3, SSB 3 322 ; and PCI 3, SSB 2 324 .

[0084] In option b 330, satellite 332 may use multiple PCIs, and each of the spot beams may correspond to a different PCI. The spot beams may be represented as: PCI 1 SSB 1 334; PCI 2 336; PCI 3 338; PCI 4 340; PCI 5 342; PCI 6 344; PCI 7 346; PCI 8 348; PCI 9 350; PCI 10 352; PCI 11 354; PCI 12 356.

[0085] In option c 360, each of the two satellites 362, 372 may use a single PCI, and each spot beam may correspond to a different SSB. For example, satellite 362 may use PCI 1. Thus, satellite 362 may have spot beams represented as: PCI 1, SSB 1 364; PCI 1, SSB 2 366; PCI 1, SSB 3 368; PCI 1, SSB L 370. Another satellite 372 may use PCI 2 (which may be different from PCI 1). This satellite 372 may have spot beams represented as: PCI 2, SSB 1 374; PCI 2, SSB 2 376; PCI 2, SSB 3 378; PCI 2, SSB L 380.

[0086] Figure 4 Schematic diagram of an example of feeder link switching for a non-GEO satellite 404. In a non-GEO constellation, feeder link switching may provide service continuity when a gateway (GW) is no longer the best candidate to serve a given satellite due to the movement of the satellite relative to the earth. If the satellite has a regenerative configuration (e.g., where the gNB is located in the satellite), the change of GW may occur without the WTRU's knowledge. Otherwise, for satellites with a transparent configuration (e.g., where the gNB is located in the GW), all WTRUs currently served by the satellite may have to re-establish connectivity to the target GW to account for the implicit change of the gNB.

[0087] exist Figure 4 In the example shown, at a first time point T1 400, a satellite 404 may be in a first position relative to the earth 406. In the first position, at time point T1 400, the satellite 404 may be in communication range with a gateway (e.g., GW1 410) via a wireless link 408. This may be due to the satellite being within a transition threshold 412. GW1 410 may communicate with gNB 414 via another wired or wireless link 416. Alternatively, GW1 416 may be collocated with gNB1 414. The satellite 404 may be out of range of GW2 418, so the link 420 may not convey satellite 404 control or data to or from gNB2 422.

[0088] At another time point T2 402, satellite 404 may move to a second position relative to earth 406. At the second position, the satellite may not be within communication range with GW1 414 via wireless link. This may be due to exceeding transition threshold 412. When transition threshold 412 is exceeded, satellite 404 may establish communication with GW2 via wireless link 424. GW2 may communicate with gNB2 422 via link 420.

[0089] Some entities that perform one or more radio access functions, including eNBs and gNBs, may not be stationary. Examples of such entities may include non-terrestrial deployments such as satellites, high altitude pseudo-satellites (HAPS), aerial platforms, and aerial base stations such as drones or other unmanned aerial vehicles. For example, low earth orbit satellites and medium earth orbit satellites may move rapidly relative to a given WTRU location. As an example, in a two-hour orbit, a low earth satellite may observe a stationary WTRU from horizon to horizon for approximately 20 minutes. Such rapid movement may cause problems for mobility procedures for mobile and stationary WTRUs. Mobile WTRUs may include non-land-based WTRUs, such as water-based WTRUs including boats, ships, or other vessels. The embodiments described herein may address such issues.

[0090] Although non-terrestrial deployments are provided here as specific examples, the embodiments described here are by no means limited to such scenarios, and may also be applicable to terrestrial deployments (e.g., non-stationary relay nodes, and other wireless technologies such as WiFi and LTE). The term satellite here may be understood to generally refer to any non-stationary entity that performs one or more RAN functions.

[0091] As a satellite moves, the geographic location served by the satellite may change. Therefore, a constellation of satellites may be deployed to provide continuous coverage. For example, when a satellite leaves a coverage area, a different satellite within the constellation may be responsible for providing continuous coverage of the location that the previous satellite just left. Since a stationary WTRU may typically only be in a spot beam for a few minutes with a non-geostationary (non-GEO) satellite, situations may occur where a WTRU in the coverage area needs to frequently switch or be switched to a different satellite (referred to herein as "satellite switching"). In some cases or during some time periods, satellites may overlap in coverage.

[0092] For terrestrial mobility in Release 15, when a GW changes, the satellite may suddenly need to reconfigure itself to serve the new GW (including transmission of new SSBs). The WTRU may not be aware that this change may have occurred because measurements of the target cell may not be available to the WTRU unless the satellite starts broadcasting the SSBs associated with the target GW in advance. The sudden change or reconfiguration may cause the WTRU to lose its connection, thus triggering a re-establishment to the reconfigured satellite.

[0093] From a system perspective, every time the WTRU changes GW for the transparent non-GEO satellite(s), reestablishing the connection with the gNB may be costly in terms of service continuity. More specifically, considering that the two GWs may be geographically far apart and the propagation delay may be several orders of magnitude higher than that of the terrestrial network, the cumulative delay incurred in reestablishing the connection may result in severe service disruption.

[0094] In an embodiment, physical layer transmission aspects such as PCI may be satellite specific. In other words, one or more cells may move with the satellite. In such an embodiment, a change in the satellite over the coverage area may result in a change in the PCI. From the WTRU's perspective, a change in the satellite may be viewed as a handover event. Such an embodiment may be referred to herein as having non-transparent satellite mobility.

[0095] Figure 5 is a network diagram for an example of non-transparent satellite mobility. Figure 5 In the example shown, at time T1 500, satellite 2 506 illuminates two cells (cell 2 510A and cell 3 512A) with its own PCI 21 and PCI 22, respectively. Satellite 1 504 illuminates cell 1 508A with PCI 11. At T1, satellite 1 504 and satellite 2 506 are moving 504A, 506A. At time T2 502, satellite 2 506 moves away 506B from cell 2 510B. Satellite 1 504 may also move 504B to replace it and thus may provide coverage to cell 2 510B. In this example, satellite 2 506 may use PCI 12 to provide coverage to cell 2 510B. The WTRU in cell 2 510B may be configured to treat this as a satellite mobility event at time T2 502. Satellite 1 504 may still illuminate cell 1 508B with PCI 11. Satellite 2 506 may illuminate cell 2 512B with only PCI 22. Such examples may be extended to the case where satellites use multiple spot beams to cover cells, or each satellite may only cover one cell at a given time.

[0096] In other embodiments, physical layer transmission aspects such as PCI may be specific to the coverage area. In other words, the satellite may adjust its transmissions based on the coverage area. In such embodiments, a change in the satellite over the coverage area may not result in a change in the PCI. From the WTRU's perspective, the change in the satellite may be handled as an intra-cell handover. Such embodiments may be referred to as cell-transparent satellite mobility.

[0097] Figure 6 is a network diagram of an example of cell transparent satellite mobility from time T1 600 to T2 602. Figure 6In the example shown, at time T1 600, satellite 2 606 illuminates 2 cells (cell 2 610A and cell 3 612A) with PCI 2 and PCI 3 respectively, while satellite 1 604 illuminates cell 1 608A with PCI 1. At time T1 600, satellite 1 604 and satellite 2 are moving 604A, 606A. At time T2, satellite 2 606 moves 606B away from cell 2 610B, and satellite 1 604 may move 604B to take its place and provide coverage to cell 2 610B. In this example, satellite 2 606 may use PCI 2 to provide coverage to cell 2 610B. The WTRU in cell 2 610B may be configured to treat this as a satellite mobility event at time T2 602, such as a triggered intra-cell handover event. Cell 1 608B may remain illuminated by satellite 1 604 at time T2 602. Satellite 2 may illuminate cell 3 612B only at time T2 602. In some embodiments, the WTRU may be configured to assume system frame number (SFN) continuity after a satellite mobility event. This example may be extended to the case where a satellite uses multiple spot beams to cover a cell or each satellite may only cover one cell at a given time.

[0098] In non-GEO NTN deployments, the paths of the satellites may be known in advance and the timing between satellites may be precisely coordinated. This information may be used to implement low overhead mobility procedures. In an embodiment, the WTRU may be configured to perform actions corresponding to the mobility procedures at a certain time instance (e.g., at a frame, subframe, or timeslot boundary). The WTRU may be configured to have a time instance after which the WTRU may not assume that the current serving gNB (e.g., satellite) is available for communication. Time-based triggers may also be beneficial to indicate a time after which the WTRU may assume that the incoming satellite has received the WTRU context and is ready to serve the WTRU. For example, the serving satellite may ensure that the necessary WTRU context is available at the target satellite before the time instance associated with satellite mobility.

[0099] Due to excessive propagation delays associated with NTN deployments, measurement reports may be delayed and / or handover commands may be lost, resulting in handover failures. In an embodiment, the WTRU may receive a radio resource control (RRC) reconfiguration with a trigger condition associated with a future time instance or an offset thereof. The time instance may correspond to the time at which the change of satellite occurs. The time instance may be indicated using one or more of the methods described below. The WTRU may apply the stored reconfiguration at the time instance configured in the serving cell.

[0100] The WTRU may be configured to send measurement reports at a time instance in a serving cell or configured by a serving cell. In an embodiment, the measurement information may be broadcast or unicast by a satellite or base station. In an embodiment, the WTRU may be configured with a measurement configuration having a report configuration associated with an offset of a time instance. The time instance may be indicated using one or more of the embodiments described below. For example, the time instance may correspond to the time when the satellite leaves the coverage area, and the offset may be configured based on propagation delay so that the mobility process may be performed before the new satellite arrives. In an embodiment, the offset may be broadcast in system information. In another embodiment, the offset may be configured to be specific to the WTRU. In one embodiment, this is useful for triggering a mobility event to the WTRU before the serving satellite moves out of the coverage area when a better terrestrial gNB is nearby. In some embodiments, the WTRU may be configured to perform neighbor measurements without DRX cycle restrictions and / or relaxations during a satellite switching event.

[0101] Due to transparent satellite mobility, in some embodiments, the WTRU may trigger a procedure (e.g., a connection request procedure), but before the request is processed or a response is received, the serving satellite may leave and a new satellite may take over the request. This may cause unnecessary delays, control plane latency, and service interruptions. To avoid this, the WTRU may be prohibited from attempting new RRC procedures during an upcoming satellite mobility. For example, the WTRU may be configured to suspend one or more procedures at or after a time instance configured in the serving cell. In an embodiment, the WTRU may be configured to suspend a signaling radio bearer (SRB) from the offset to a time instance associated with the satellite change. For example, any of the methods described below may be used to indicate the time instance. The WTRU may also be configured to resume the SRB upon receiving a transmission from a new satellite. In an embodiment, the WTRU may be configured to determine whether one or more protocol layers need to be rebuilt from a stored reconfiguration during a satellite mobility event. If there is an upcoming satellite mobility event, the WTRU may suspend signaling at those protocol layers. The WTRU may resume signaling at those protocol layers upon successful reestablishment of the protocol layers.

[0102] In an embodiment, the WTRU may be configured to delay, suppress or refrain from performing at least certain UL transmissions (e.g., those associated with a MAC process) when a satellite handover event is imminent. For example, the WTRU may stop processing UL transmissions (e.g., data transmissions, control transmissions, HARQ transmissions, etc.) associated with uplink resources for new transmissions. Additionally or alternatively, the WTRU may stop grant processing and / or perform initial transmissions for HARQ processes. Additionally or alternatively, the WTRU may continue to perform data processing associated with SRBs, but not for DRBs. If a satellite handover event is scheduled at time T+x, the WTRU may be configured to delay, cancel or suspend a random access procedure (the random access procedure including a preamble transmission and / or retransmission triggered at time T), where the value of x may be preconfigured. The value of x may be a function of the time it takes to complete a random access procedure (e.g., a 2-step random access procedure or a 4-step random access procedure). Additionally or alternatively, the value of x may be a function of the time it takes to complete another procedure. Additionally or alternatively, the value of x may be a function of the round trip time (RTT) of transmissions between the WTRU and the network. The RTT may be a multiple of the estimated and / or observed RTT. Additionally or alternatively, x may correspond to the observed HARQ RTT, for example, the time from receiving the first grant for a new transmission until the WTRU determines that the HARQ process has successfully completed. In another example, if a satellite handover event is scheduled at time T+x, the WTRU may be configured to suspend scheduling request transmissions or retransmissions at time T. Similarly, other MAC control transmissions may be suspended when a satellite handover event is imminent. Whether the WTRU performs any of the above functions may be a configuration aspect of the WTRU.

[0103] The WTRU may be configured to receive an indication of a time instance associated with satellite mobility. Such a time instance may be signaled using one or more mechanisms including, for example, via a signaling parameter including: a time indication using Coordinated Universal Time (UTC), a time indication using a counter, or a preconfigured hyperframe number (HFN) value.

[0104] With respect to time indication using Coordinated Universal Time (UTC), the WTRU may receive a time instance indication as a UTC value. The UTC value may correspond to the number of seconds that have passed since a fixed point in the past. For example, the WTRU may receive a current UTC broadcasted in a system information message. For example, the WTRU may receive a UTC associated with a satellite mobility event (e.g., when satellite mobility is triggered) in a broadcast message. The WTRU may be configured to perform a reconfiguration when the current UTC becomes equal to the UTC associated with the satellite mobility event. In some embodiments, the WTRU may be configured with a UTC associated with a satellite mobility event in dedicated RRC signaling, which may be signaling as part of a conditional reconfiguration.

[0105] With respect to time indication using a counter, the WTRU may be configured to implicitly receive an indication of a time instance via the state of the counter. For example, the WTRU may receive a counter value indicating the number of time units remaining until a satellite mobility event. The time unit may be expressed in terms of a SFN, a modification period, a subframe, a time slot, and / or a multiple of ms starting from a boundary of a message carrying the counter value. The time unit may be expressed in terms of an offset, such as a number of subframes starting from 0. The counter may be carried in a broadcast message, such as a master information block (MIB) or a system information block (SIB) message. The WTRU may be configured to perform a reconfiguration associated with satellite mobility when the count value reaches zero.

[0106] Regarding the use of preconfigured HFN values, the WTRU may be configured to determine a time indication based on the HFN value configured for the satellite mobility event. For example, the preconfigured HFN value may be broadcast in system information (e.g., in the MIB or SIB). When the system HFN reaches a value associated with a satellite mobility event, the WTRU may be configured to perform a reconfiguration associated with satellite mobility.

[0107] In an NTN deployment, the flight path of the satellite can be deterministic. Therefore, the coverage provided by the satellite on the earth can also be deterministic. The WTRU can be configured to have an association between a geographic location and one or more satellites that can provide services at that location. When the WTRU moves to an area served by a satellite different from the current satellite, it can be configured to perform one or more actions associated with mobility. In the embodiments described below, the location of the WTRU can be represented by one or a combination of global navigation satellite system (GNSS) / global positioning system (GPS) coordinates, a function of the spot beam serving the WTRU, and the visibility of multiple satellites. The satellite can provide GPS information in broadcast signaling or out-of-band (e.g., cellular out-of-band signaling).

[0108] In an embodiment, the WTRU may be configured to apply the stored reconfiguration based on its location. The location may be expressed based on the GNSS / GPS location and / or the spot beam currently serving the WTRU. For example, the location of a geosynchronous satellite may be fixed relative to a location on the earth. The WTRU may be configured to apply the stored reconfiguration when it enters a coverage area associated with a different satellite. If the time taken for convergence of cell measurements is slower than obtaining location information, a method that relies on location information rather than cell measurement may be beneficial. In addition, in NTN deployments, unnecessary measurement overhead may be reduced because the location and / or coverage of different satellites may be known in advance.

[0109] Since the satellite coverage area may be quite large, it may become cumbersome to configure ground neighbors for measurements. In an embodiment, the WTRU may be configured to apply measurement configurations based on its location in the satellite coverage area. For example, the WTRU may be configured to have multiple measurement object lists. The WTRU may select and apply a measurement object list for measurement based on the WTRU location. The WTRU location may be represented as a function of GNSS / GPS coordinates or based on the spot beam currently serving the WTRU.

[0110] In one embodiment, the WTRU may be configured to apply RRC reconfiguration at a time greater than or equal to a preconfigured time instance. In another embodiment, the WTRU may be configured to apply RRC reconfiguration based on its position relative to the satellite position (e.g., based on ephemeris data). The WTRU may rely on a neural network to determine whether to apply RRC reconfiguration. The WTRU may determine its position based on one or more of GNSS / GPS data, positioning methods, and / or RAN-based positioning methods. In another embodiment, the WTRU may apply RRC reconfiguration when a combination of time- and location-based conditions (in one embodiment, also with a cell quality metric above a threshold) is met. In one embodiment, RRC reconfiguration may initiate a UL timing alignment procedure. In another embodiment, RRC reconfiguration may reestablish RLC and / or PDCP. Additionally or alternatively, RRC reconfiguration may reset the MAC layer. Additionally or alternatively, RRC reconfiguration may result in a security context update, for example, deriving and using new access layer security keys.

[0111] Figure 7 FIG. 7 is a network diagram 700 illustrating location-based measurement object selection. Figure 7In the example shown, the WTRU 718 may be configured to have N measurement object lists, and in an embodiment the WTRU 718 may be configured to determine one measurement object list from the plurality of lists based on the WTRU location, where the WTRU location may be associated with the spot beams 704-708 illuminated by the satellite 702. For example, when served by spot beam 1 704, the WTRU 718 may select and apply neighbor list 1 712 for measurement. Neighbor list 1 712 may indicate gNBs 712A-712D. The WTRU 718 may further be implicitly configured to reconfigure the measurement object list when moving to a different spot beam. For example, when the WTRU 718 moves to a location illuminated by spot beam 2 706, the WTRU may apply neighbor list 2 714. Neighbor list 2 714 may indicate gNBs 714A-714D. When the WTRU 718 moves to spot beam N 708, the WTRU may apply neighbor list N 716. Neighbor list N 716 may indicate gNBs 716A-716C.

[0112] In other embodiments, the WTRU may be configured to trigger the start of neighbor measurements based on the WTRU location. For example, the WTRU may be configured to start one or more neighbor measurements when the WTRU enters a spot beam at the edge of a satellite coverage area. The WTRU may be configured to perform measurements based on the next spot beam entered from the previous spot beam. In this way, the directional movement of the WTRU may trigger the measurement to be performed.

[0113] In an embodiment, a WTRU may be configured to monitor a downlink (DL) signal addressed to more than one WTRU. The DL signal may indicate a mobility event. Such a multicast DL signal may avoid the need to transmit WTRU-specific signaling (e.g., RRC reconfiguration) to a large number of WTRUs via a satellite link with large propagation delays. In an embodiment, a WTRU may be configured to monitor such a DL multicast signal at all times. In other embodiments, a WTRU may be configured to monitor the multicast DL signal only during time intervals of planned satellite mobility.

[0114] In an embodiment, the WTRU may be configured to monitor physical downlink control channel (PDCCH) commands addressed to a predefined radio network identifier (RNTI). In one example, the RNTI may be associated with a group of WTRUs that may be located within a spot beam. In another example, the RNTI may be cell-specific and applicable to all WTRUs in the cell. For example, the RNTI may be predefined for a mobility event, for example, using one of the values ​​from 0xFFF0-0 xFFFD. When a PDCCH command is received with a predefined RNTI, the WTRU may determine that a satellite mobility event has occurred. In some embodiments, the WTRU may be configured to apply a stored reconfiguration when a PDCCH command associated with a mobility event is received. The RNTI may be associated with a specific configuration. For example, the WTRU may use an RNTI value to determine what configuration to apply to a mobility event. The WTRU may be configured to have multiple RNTIs for a given cell ID and / or satellite.

[0115] In an embodiment, the WTRU may determine an upcoming satellite mobility event based on an indication received in a paging message. In some embodiments, such a paging message may indicate the type of satellite mobility, for example, whether the satellite mobility is a non-transparent satellite mobility type or a cell-transparent satellite mobility type. In other embodiments, the WTRU may be configured to determine an upcoming satellite mobility event based on an indication provided in a short DCI message addressed to the P-RNTI. For example, one or more bits may be reserved in a short message on the PDCCH to indicate the occurrence and type of a satellite mobility event.

[0116] In an embodiment, the WTRU may be configured to trigger a mobility procedure (e.g., reconfiguration with synchronization procedure) upon receipt of a specific system information message. For example, the WTRU may be configured to trigger a mobility procedure upon receipt of an indication of the presence or transmission of special system information or its update. Such system information may be specific to a group mobility event, may include parameters to be applied at a feeder link switching event, may include a transient configuration, may include parameters to be applied when switching to a target cell, and / or may include a minimum configuration required to synchronize with the target cell. Upon successful synchronization with the target cell, the WTRU may also be configured with a dedicated RRC configuration. The WTRU may be configured to acquire such system information once it is transmitted or updated. The WTRU may be configured to apply the system information at a time configured by the system information. For example, such a time may correspond to the timing of a satellite switch and / or a feeder link switch. In some embodiments, such system information may be associated with an RNTI (e.g., a reserved RNTI) that is different from the SI-RNTI.

[0117] In an embodiment, the WTRU may be configured to perform different actions based on whether the physical cell changes due to satellite mobility. For example, the WTRU may be configured to perform a first set of actions when satellite mobility occurs with a change in the physical cell ID (e.g., non-transparent satellite mobility). For example, the first set of actions may correspond to a traditional handover or an RRC reconfiguration with synchronization. In addition or alternatively, the WTRU may be configured to perform a second set of actions when the physical cell ID does not change due to satellite mobility including cell transparent satellite mobility. For example, the second set of actions may correspond to the WTRU maintaining a master cell group configuration, RNTI, radio bearer configuration, measurement configuration, or received SIB. The second set of actions may also include the WTRU synchronizing with the physical cell ID, for example, after reaching a time instance that triggers a mobility event, after reaching a location that triggers a mobility event, and / or after indicating that the WTRU has received a DL signal of a mobility event.

[0118] In an embodiment, the WTRU may be configured to request an updated timing advance after a transparent satellite mobility event. This may be necessary because the timing and / or channel conditions of different satellite transmissions may be different due to, for example, different orbital characteristics (e.g., altitude, elevation, or angle). For example, the WTRU may be configured to trigger a preamble transmission when a satellite mobility event is detected. In order to avoid conflicts caused by multiple WTRUs attempting preamble transmissions at the same time, DL initiated preamble transmissions may be configured. For example, the WTRU may be configured to monitor possible PDCCH commands addressed to its RNTI to perform preamble transmissions. The command may explicitly indicate to the WTRU that a mobility event has occurred. If no PDCCH command is received within a preconfigured time period, the WTRU may trigger a contention-based preamble transmission or a dedicated preamble transmission if the command provides for a preamble transmission.

[0119] In some cases, such as when satellites are changed and data / WTRU context may need to be forwarded between satellites, the WTRU may be required to perform additional actions (including PDCP data recovery, PDCP re-establishment, RLC re-establishment, security re-establishment, triggering of a new BSR, and MAC reset). The PDCCH command may explicitly indicate to the WTRU that these actions need to occur, or the WTRU may determine this based on its location. Alternatively, the WTRU may wait for a RA msg2 response to trigger these actions and / or be explicitly commanded to perform these actions after a msg2 response.

[0120] In an embodiment, RRC reconfiguration as a function of time instance and / or location may be modeled as a conditional reconfiguration. A trigger condition may be associated with a time instance and / or location, thereby triggering the reconfiguration. Alternatively, the WTRU may be configured to apply the reconfiguration based on a broadcast indication at a preconfigured time instance, where the time instance may correspond to a change in the termination point of at least one RAN function (e.g., a satellite handover event). Similarly, the WTRU may be configured to apply the broadcast configuration at a preconfigured location, where the location may correspond to a change in the termination point of at least one RAN function.

[0121] The WTRU may be pre-configured with Layer 2 (L2) behavior based on time and / or location triggers. For example, the WTRU may determine the degree of L2 and / or Layer 3 (L3) context persistence based on a broadcast indication. Additionally or alternatively, the WTRU may determine the degree of L2 / L3 context persistence based on a broadcast indication. In a bent pipe architecture, the WTRU may be configured to perform layer (L) resynchronization while maintaining radio bearers. In a regenerative architecture, the WTRU may indicate via a broadcast configuration whether the MAC layer needs to be reset or whether the RLC and / or PDCP layer needs to be rebuilt.

[0122] Figure 8 is a network diagram showing an application of a transient configuration associated with a mobility event. Figure 8 In the example shown, the WTRU may be configured to apply a configuration for a specified duration (i.e., a transient configuration), where the configuration performs one or more of the following operations: provides more opportunities for DL ​​synchronization measurements; provides more opportunities for UL synchronization, for example, via random access channel (RACH) opportunities, providing a denser RACH configuration; provides a mechanism for the WTRU to determine the start of DL signal availability for measurement; and provides a mechanism for the WTRU to determine the start of UL resource availability for preamble transmission. Such a transient configuration is feasible at least because, in the period immediately following the satellite mobility event, the UL and / or DL ​​resources of the cell are not occupied due to a lack of data transmission.

[0123] Figure 8The illustrated embodiment is shown at two times T1 800 and T2 802. At time T1, satellite 1 804 moves 804A, along with satellite 2 806 moving in the same direction of movement 806A. Satellite 2 serves the WTRU in spot beam 808A. At time T2, satellite 1 804 and satellite 2 806 may move 804B, 806B such that spot beam 808B becomes served by satellite 1 804. In the event of a spot beam change, the WTRU being served may be configured to perform an action, such as performing a RACH transmission. If each WTRU performs a RACH at the same time opportunity, a resource conflict may occur. Therefore, the WTRU may instead apply a transient configuration, which may, for example, facilitate RACH or provide an improved RACH mechanism.

[0124] In an embodiment, a WTRU may be configured with a first set of resources and a second set of resources for synchronization, measurement, probing, and random access purposes, wherein the first and second sets of resources may be valid only during different pre-scheduled time periods. This approach has the benefit of allowing provision of additional or more frequency resources only during one or more time periods when such resources are known to be needed. For example, the one or more time periods may occur at or near the time of a mobility event due to a satellite handover. The one or more time periods may be predictable in advance based on the satellite ephemeris and the approximate location of the WTRU.

[0125] In an embodiment, the first resource set and the second resource set may be applied to include at least one of: a measurement configuration or elements thereof (e.g., SSB and SSB measurement timing configuration elements, CSI-RS, and measurement objects for NR); one or more RACH configurations, including configured RACH resources; a radio link monitoring configuration; SRS; one or more PDCCH configurations; and one or more DRX configurations.

[0126] In an embodiment, the WTRU may determine whether to apply the first set of resources or the second set of resources. For example, the WTRU may be provided with a set of start time, end time, or start time and duration for the applicability of the configuration. The start and / or end time may be expressed in absolute time units or in a combination of HFN and SFN. The set of start and / or end times may be obtained from the application of the formula. The duration may be expressed in terms of the number of subframes. Alternatively, the WTRU may use the reception of downlink control signaling (e.g., PDCCH received from a common search space using a specific RNT1). The RNT1 value or through the DCI field may indicate the first set of resources of the second set of resources.

[0127] In an embodiment, the WTRU may be configured to have one or more special RACH opportunities in addition to regular RACH opportunities. Alternatively, the WTRU may be configured with two sets of special RACH opportunities, or with a special or dedicated RACH configuration that may be applied in place of the special RACH opportunities. The special RACH configuration may increase the opportunities for preamble transmission and may provide increased RACH capacity to address the needs of a potentially large number of WTRUs performing mobility events. This approach may be beneficial because different time and frequency domain RACH resources may provide better isolation and may not suffer from the high cross-correlation issues associated with using different root sequences to increase RACH capacity. This embodiment may be used when the satellite and / or WTRU are aware of satellite mobility and can recognize that a handover is about to occur. The resources dedicated to the RACH configuration may be resources that would otherwise be used for other data and control resources.

[0128] In an embodiment, the WTRU may be configured with dedicated RACH resources having regular RACH occasions and special RACH occasions. For example, the WTRU may receive a RACH-configuration-specific (RACH-config) and a RACH-configuration-specific special configuration. In another example, the WTRU may receive a RACH-configuration-specific configuration, which may include a RACH-ConfigGeneric configuration and a RACH-ConfigGenericSpecial configuration. The WTRU may be configured to apply a special configuration in addition to or as an alternative to the regular RACH configuration. In another example, the special RACH configuration may be part of the common RACH configuration.

[0129] In an embodiment, the WTRU may be configured to apply a special RACH configuration during the execution of a mobility event. The mobility event may be triggered based on network signaling or a location and / or time based trigger. In a further embodiment, the WTRU may be configured to apply a special RACH configuration for a specific target cell, for example, to an incoming satellite or aircraft, and may exclude RACH configurations to certain other target cells, for example, to terrestrial cells. The WTRU may be configured to release a special RACH configuration and / or apply a regular RACH configuration based on a preconfigured trigger. Such triggers may include, but are not limited to, successful completion of a RACH procedure; expiration of a timer (e.g., T304, or a specific timer associated with a special RACH timing configuration) when the current SFN exceeds the absolute SGN, at an absolute time point (e.g., UTC), or based on explicit signaling from the network.

[0130] In an embodiment, the special RACH opportunity may be implemented by using one or a combination of the following: increasing the number of RACH opportunities multiplexed in the frequency domain starting from the base RACH opportunity number, for example, by configuring a higher value for msg1-FDM, etc.; increasing the number of RACH opportunities multiplexed in the time domain, for example, by configuring the value of the PRACH-configuration index so that it results in an increased RACH opportunity compared to the adjusted or base configuration, including but not limited to increasing the number of radio frames containing RACH opportunities (appropriate values ​​of x, y in the equation x = y in the SFN pattern, for example, x = 1 and y = 0 or the like); increasing the number of subframes containing RACH opportunities; increasing the number of RACH slots within a subframe and increasing the number of time domain RACH opportunities within a RACH slot.

[0131] The WTRU may be explicitly or implicitly configured with resources within a special RACH opportunity or an extended RACH opportunity that includes special and regular RACH opportunities. In an embodiment, the WTRU may be configured to determine its RACH opportunity in an extended set of RACH resources through a distribution mechanism. For example, the WTRU may be configured with a mapping rule between its cell RNTI (C-RNTI) and one or more RACH opportunities. In other embodiments, the WTRU may determine its RACH opportunity and / or preamble based on one or more parameters associated with its dedicated configuration. For example, the WTRU may determine the RACH opportunity and / or preamble based on its demodulation reference signal (DMRS) configuration. For example, the WTRU may determine its RACH opportunity and / or preamble based on its physical uplink control channel (PUCCH) configuration and / or physical uplink shared channel (PUSCH) configuration. For example, the WTRU may determine its RACH opportunity and / or preamble based on its SRS configuration and / or beam failure recovery configuration. In an embodiment, the RACH opportunity and / or preamble may be associated with a specific beam or DL ​​reference signal. In an embodiment, the WTRU may be configured to use beam failure recovery resources to obtain timing advance after a mobility event. The WTRU may use such resources to indicate the execution of a mobility event.

[0132] In an embodiment, the WTRU may be configured to apply a transient configuration broadcast in the system information. In one embodiment, the WTRU may not have a dedicated handover command. In a further embodiment, the WTRU may perform a handover without dedicated RACH resources and C-RNTI. The WTRU may determine its RACH timing using a rule or formula that maps a WTRU identity or parameters associated with a WTRU-specific configuration, time domain distribution mechanism (e.g., SFN, subframe, time slot number) to a RACH timing. The WTRU may be configured to perform contention-based random access (CBRA) and may obtain its C-RNTI from the target cell at the time of handover.

[0133] The WTRU may be configured with multiple RACH configurations and the WTRU may select a subset of RACH configurations based on potential timing advances. The WTRU may determine the potential timing advances based on, for example, WTRU location information or satellite ephemeris information.

[0134] The WTRU may be configured with a prioritization function associated with a special RACH configuration. Such prioritization function may include, for example, the configuration of a power ramping step size or a scaling factor for a backoff indicator. In an embodiment, the WTRU may be configured to apply a more aggressive power ramp as part of a transient configuration to speed up the RACH process after a mobility event. In other embodiments, the WTRU may be configured to apply a smaller backoff as part of a transient configuration to speed up the RACH process after a mobility event.

[0135] In an embodiment, the special RACH configuration may additionally include a response window configuration to accommodate an increased number of RAR responses.

[0136] In an embodiment, the WTRU may be configured to apply a transient configuration or part thereof based on a preconfigured event. For example, the WTRU may apply a transient configuration at a specific time instance. The time instance may be indicated by any of the above methods. The WTRU may be configured with a start time for a measurement object. For example, the WTRU may start measurements associated with the measurement object at the start time. The start time may correspond to the time when an incoming satellite transmission or other transmission is expected. For example, the WTRU may apply a transient configuration associated with UL resources at a specific time instance. The specific time instance may be associated with a special RACH configuration. The WTRU may apply or assume that the special RACH configuration is applicable only after the time instance indicated in the configuration. This may correspond to the time when the incoming satellite is ready to receive the UL transmission.

[0137] In an embodiment, the WTRU may be configured with ephemeris data associated with a measurement object. For example, when the satellite position is within a preconfigured threshold, the WTRU may start measurements associated with the measurement object based on the ephemeris data information associated with the measurement object. This may correspond to the location and / or time at which the incoming satellite transmission is expected to be received. For example, the WTRU may apply a transient configuration associated with UL resources based on the location and / or ephemeris information. The WTRU may be configured with ephemeris information associated with a special RACH configuration. The WTRU may apply or assume that the special RACH configuration is applicable only when the satellite position is within a preconfigured threshold. This may correspond to the location at which the incoming satellite can start receiving UL transmissions. The preconfigured threshold may be provided to the WTRU by one or more ground base stations, by a satellite, a blimp, or via other means.

[0138] In an embodiment, the WTRU may apply the transient configuration upon receiving a paging for a system information update. Such a system information update may indicate that a special version of the system information is to be applied. For example, a predefined or reserved value tag may indicate that a transient configuration should be applied. The WTRU may receive a system information update indication in a paging message indicating that a transient configuration is available or should be applied. The WTRU may then retrieve system information including the transient configuration. Alternatively, the WTRU may determine that a transient configuration should be applied based on an indication that may implicitly indicate a change in a cell and / or satellite. For example, by changing cells, the WTRU may detect that the system information includes a transient configuration. Some cells may broadcast transient configurations, while other cells may not. Some WTRUs may be able to support transient configurations, while other WTRUs may not. Capability information may be reported to the cell.

[0139] In an embodiment, the time at which the beam will be steered or the WTRU will be covered by an incoming satellite may be known a priori since the movement of the satellite is determined. The orbital characteristics of the satellite constellation may result in frequent changes of satellites, for example, a low altitude LEO constellation. To avoid frequency reconfiguration signaling, the WTRU may be configured to apply a transient configuration on a periodic basis. The periodicity may be expressed in terms of time. Additionally or alternatively, the periodicity may be expressed as a function of the SFN mode x, where x may be preconfigured. Additionally or alternatively, the periodic configuration may also include subframe and / or timeslot offsets. In other embodiments, the location of the transmitter may not be known in advance, for example, a blimp or other aircraft may require a broadcast transmission of location information, or the WTRU may determine the location by other means.

[0140] In an embodiment, the WTRU may be configured to set various transmission parameters for initial transmission at the activation time of a mobility procedure that may involve a change of satellite in a low earth orbit satellite (LEOS) and / or medium earth orbit satellite (MEOS) scenario and / or a change of serving gateway during a feeder link handover. Such parameters may enable access without a RACH procedure or, alternatively, use of a shorter preamble for the RACH procedure. The parameters may include at least one of a timing advance, an offset in receive time, a Doppler shift, and a transmit power offset.

[0141] In an embodiment, the WTRU may determine an activation time, which may be expressed in absolute time units or in a combination of HFN and SFN. Additionally or alternatively, the WTRU may determine information for determining changes in transmission parameters at the activation time. For example, the WTRU may determine an explicit indication of a change in timing advance, Doppler shift, or transmission power. This functionality is easily applicable in cases where the gateway changes but the satellite itself does not change. This functionality may also be used in cases where the network approximately knows the location of the WTRU. To support this functionality, the WTRU may report its location to the network periodically or when the location has changed by more than a certain distance since the last report. In another example, the WTRU may use ephemeris data to determine geographic information for the source and target satellites at the activation time. This information may be used in conjunction with the WTRU location to accurately determine the required parameters (e.g., timing advance offset). In another example, the WTRU may determine resources for downlink measurements (e.g., downlink reference signals corresponding to the source and target satellites). Such reference signals may be designed so that different scrambling sequences are applied at different time instances where reference signals may exist. This enables detection of delay differences greater than the periodicity of each reference signal. The WTRU can infer the difference in transmission delay between satellites (assuming clock synchronization between satellites) by comparing the reception times of two reference signals detected using a specific scrambling sequence. The WTRU can also estimate the transmission power adjustment based on the difference in received power between the reference signals.

[0142] The WTRU may apply frequency compensation prior to feeder link switching to compensate for the difference in Doppler shift between the link from the SGW to the serving satellite and the link from the serving satellite to the target gateway (TGW). This may occur in a bent pipe configuration where no modulation and / or compensation is performed on the satellite. In one embodiment, the WTRU may detect the frequency difference implicitly via measurements of the replayed signal directed from the TGW to the serving satellite. In another embodiment, the WTRU may pre-calculate the expected offset via satellite ephemeris data and data about the TGW location.

[0143] The WTRU may perform measurements on signals directly relayed via the serving satellite before feeder link switching. In embodiments where the PCI / SSB combination per spot beam is common between the SGW and TGW, the measurement objects may be separated to enable the WTRU to perform measurements on both channels. This separation may be naturally offset via the difference in propagation delay between the SGW and TGW. In another embodiment, the TGW may transmit synchronously with the SGW and transmit the measurement objects to the SGW with a specific offset.

[0144] The WTRU may be provided with configuration information indicating when DL transmissions from a non-serving gateway are expected. In one embodiment, the WTRU may be pre-configured with a mapping between DL transmissions and associated gateways. For example, such an association may be part of a measurement configuration. In addition, the transmission period associated with the non-serving gateway may be configured to occur in a measurement gap with respect to the SGW. In one embodiment, the WTRU may be configured to receive DL transmissions from the non-serving gateway in a BWP that is different from the active BWP associated with the SGW. In another embodiment, the WTRU may first perform a HO based on timing and location, and the measurement may occur after the feeder link switch.

[0145] In one embodiment, if the measurement is above a certain threshold, the satellite may start the RA procedure before the gateway switch. Additionally or alternatively, the WTRU may allow the RACH to move to the next gateway before the gateway switch. The WTRU may transmit the measurement results to the network before the feeder link switch using one or more routes. Before the feeder link switch, the WTRU may transmit to both the serving and target gateways to avoid data loss in preparation for the feeder link switch.

[0146] In an embodiment, when satellite handover affects only lower layer functionality (eg, in case of CU-DU partitioning under bent pipe and MAC 230 configuration), the WTRU may be configured to perform link reconfiguration instead of rebuilding L2 and / or L3.

[0147] In an embodiment, the WTRU may be configured to monitor beam failure in the source cell when it is configured with one or more candidate beam lists for the source cell, the target cell, or both the source cell and the target cell. For example, the WTRU may be configured with a candidate beam list in the target cell or a mix of beams in the source and target cells. The RRC reconfiguration with the candidate beam list in the target cell may be transmitted early enough to accommodate propagation delays and allow the WTRU to detect the signal of the target cell. When the wireless transmit / receive unit detects a beam failure in the source cell, it starts monitoring the candidate beams in the source cell and the target cell or either of the two according to the configuration of the candidate beam list. In another example, the WTRU is configured to have two candidate beam lists: one for the source cell and one for the target cell, which are considered valid based on a time indication or WTRU location. For example, when the WTRU is less than x meters from the border of the source cell, it considers the candidate beam list of the target cell to be activated. Additionally or alternatively, the WTRU considers the candidate beam list in the target cell to be valid when the current time instance is less than y ms from the cell change execution time. In addition, once the WTRU is configured with one or more candidate beam lists in the target cell, the WTRU is configured with a dedicated UL / DL BWP in the target cell and the associated CORESETS for PDCCH monitoring. The WTRU then assumes that the PDCCH in the target cell for beam failure recovery request response is quasi collocated (QCL) with the reference signal (RS) of the target cell.

[0148] In an embodiment, for the beam indication of the PDCCH, the WTRU is configured with N states for each CORESET in the target cell in addition to the M states configured by RRC for each CORESET in the serving cell. Using MAC signaling, the network can dynamically indicate that a specific transmission configuration indicator (TCI) state in the target cell is valid at the time of the satellite change. The RRC configuration for the N states in the target cell can be received immediately when the connection with the current source cell is established, or by RRC reconfiguration before the satellite change.

[0149] For beam indication of PDSCH, if the scheduling offset is greater than N symbols, the WTRU may receive the TCI state of the PDSCH transmission in the target cell in the DCI for scheduling allocation. To this end, the WTRU is configured for the TCI state of the source cell and the target cell. If the scheduling offset is less than or equal to N symbols, the WTRU assumes that the TCI state of the PDCCH in the target cell indicated by the MAC signaling is valid for the PDSCH in the target cell. The value of N may be a function of at least one of the time instance and the WTRU location. For example, when the WTRU is close to a cell border or when the satellite / cell change execution time is close, a larger value may be used to provide the WTRU with sufficient time to decode the TCI information within the DCI and adjust the receiver beam towards the target cell before the PDSCH is to be received.

[0150] Non-terrestrial networks may require WTRUs that can support both GNSS and non-GNSS capabilities. Given the importance of WTRU location information in non-terrestrial and / or mobile networks (e.g., for mobility, tracking area management, and paging), non-GNSS devices may provide some form of location information in one or more ways, including, for example, observations of terrestrial cells, calculations based on implicit information, and / or calculations based on spatial information from serving and / or neighbor cells.

[0151] Regarding observation of terrestrial cells, the WTRU may detect signals originating from one or more terrestrial cells. This information can provide an estimate of the WTRU's location based on the geographic location of the terrestrial cells and the boundary coverage of the cell or cells.

[0152] Regarding calculations based on implicit information, the WTRU may calculate the position of the WTRU using implicit information broadcast from one or more visible satellites. Such information may include, for example, Doppler shift offset, timing advance, satellite ephemeris, and / or time. For example, if the WTRU detects ephemeris data for one or more satellites, the approximate distance to the satellite may be estimated via the timing advance and may be refined by taking into account the Doppler shift, which may indicate to the WTRU whether the satellite is moving towards the WTRU or receding from the WTRU. The estimate may be refined by a combination of such information from multiple satellites.

[0153] Fig. 9900 is a diagram showing an example of an approximate WTRU location 908 derived from implicit measurements and offsets. In example 900, a satellite 902 is moving in a direction 902B. A WTRU 904 may determine an approximate WTRU location 908 based on a Doppler shift 906 and / or a timing advance 910. The WTRU may store or receive a table reflecting Doppler shift to location. The location of the WTRU may be used to determine if a RAN function termination is imminent. For example, if the WTRU has a table of cells, locations, satellite timing, and / or other spatial information, the WTRU may determine the location using Fig.10 process.

[0154] With respect to spatial information of or from serving and / or neighboring cells, the WTRU may estimate its rough position based on the serving beam received from the serving cell, for example by determining the PCI or SSB of the cell and comparing it to a table. In an embodiment, the WTRU may estimate its position based on the TCI state. In an embodiment, the WTRU may estimate its position based on SS block and / or CSI-RS measurements. This mechanism may be extended to include beam measurements (e.g., SS block and / or CSI-RS measurements) from neighboring cells.

[0155] Fig.10 1000 is a flow chart illustrating an example method performed by a WTRU during a handover. Fig.10 In the example shown, the WTRU may receive a broadcast configuration 1002 from a serving cell. The serving cell may be a satellite, blimp, or other mobile object. Alternatively, the serving cell may be a cell of a stationary object (e.g., a base station or a stationary satellite). The broadcast configuration may be broadcast in system information with a dedicated or non-dedicated broadcast period. The broadcast configuration may be requested by an interested WTRU or by another WTRU. The WTRU may determine when a change in RAN termination may occur or may occur based on the broadcast configuration 1004. The determination may be based on a timer, location information, neighbor information, etc. The WTRU may receive a dedicated configuration 1006 from the serving cell or another cell, the dedicated configuration including a preamble, a transient configuration, and an indication of Layer 2 behavior. The WTRU may monitor for changes in RAN function termination 1008. If a change in RAN function termination is detected 1010, the WTRU may suspend any pending or scheduled uplink data or control transmissions 1012. The WTRU may apply the transient configuration 1014 and may transmit the preamble to the target cell 1016. The WTRU may then synchronize 1018 with the target cell and apply L2 behavior 1020. If a change in RAN function termination is not detected, the WTRU may continue to monitor 1008 until power is turned off or until another state change occurs.

[0156] There may be devices in the network that remain stationary, such as remote Internet of Things (IoT) sensors including pipelines and / or one or more devices that remain within a geographically defined location. Such devices can implement preconfiguration because it can be assumed that the location of the device is more or less fixed at a given time. When preconfiguration is used, the device can have a preconfigured location, which can be stored in memory. The preconfigured location information can be precise, or it can be a rough estimate based on a certain geo-fence location (e.g., the center of the geo-fence boundary).

[0157] Due to the deterministic movement of satellites, it may be known which satellites will cover a particular location at a given time. If the WTRU is stationary or nearly stationary, it may be estimated which satellites are available and which is the best candidate to serve the device at a given time of day. Such information may be pre-configured in the device based on, for example, historical information, and / or may be updated on a semi-periodic basis, daily, hourly, etc.

[0158] Although the features and elements are described above in specific combinations, it will be understood by those skilled in the art that each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein can be implemented in a computer program, software, or firmware that is incorporated into a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via a wired or wireless connection) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor associated with the software can be used to implement a radio frequency transceiver used in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method performed by a wireless transmit / receive unit (WTRU), the method comprising: receiving radio resource control (RRC) reconfiguration information, the RRC reconfiguration information indicating a triggering condition for triggering an RRC reconfiguration at a time instance, wherein the RRC reconfiguration information indicates the time instance as a time offset, and wherein the time offset corresponds to a time period elapsed from a fixed time instance; and When the trigger condition is met, the RRC reconfiguration is performed.

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