Apparatus, method, and computer program for UE cell selection control in non-terrestrial networks

Abstract

An apparatus is provided, comprising components for: determining which of at least two lower-level radio units (DU1, DU2) co-located at a first position, wherein each lower-level radio unit is associated with a higher-level radio unit (CU1-CU3), has an optimal path to the associated higher-level radio unit; and causing the transmit power of the determined lower-level radio unit among the at least two lower-level radio units (DU1, DU2) received at a user equipment (UE1, UE2) to be higher than the transmit power of any of the other lower-level radio units among the at least two lower-level radio units received at the user equipment.

Description

Technical Field

[0001] This application relates to a method, apparatus, system, and computer program, and specifically, but not exclusively, to user equipment (UE) cell selection control in a non-terrestrial network (NTN). Background Technology

[0002] A communication system can be viewed as a facility that enables a communication session between two or more entities (such as user terminals, base stations, and / or other nodes) by providing carrier waves between the various entities involved in the communication path. For example, a communication system can be provided via a communication network and one or more compatible communication devices (also referred to as stations or user equipment) and / or application servers. The communication session can include, for example, communication of data carrying communications such as voice, video, email, text messages, multimedia, content data, Time-Sensitive Networking (TSN) streams, and / or data in industrial applications, such as critical system messages between a brake and a controller, critical sensor data (such as measurements, video feeds, etc.) directed to the control system, etc. Non-limiting examples of the services provided include two-way or multi-way calling, data communication or multimedia services, and access to data network systems (such as the Internet).

[0003] In wireless communication systems, at least a portion of a communication session, such as between at least two stations or between at least one station and at least one application server (e.g., for video), occurs on a wireless link. Examples of wireless systems include Public Land Mobile Networks (PLMNs) operating based on 3GPP radio standards such as E-UTRA, New Radio, and satellite-based communication systems, and various wireless local area networks (WLANs) such as wireless local area networks. Wireless systems are typically divided into cells and are therefore often referred to as cellular systems.

[0004] Users can access the communication system through appropriate communication equipment or terminals. The user's communication equipment may be referred to as user equipment (UE) or user gear. The communication equipment is provided with appropriate signal receiving and transmission means for enabling communication, such as access to a communication network or direct communication with other users. The communication equipment can access one or more carriers provided by the network (e.g., a base station in a cell) and transmit and / or receive communication on one or more carriers.

[0005] Communication systems and related equipment typically operate according to a given standard or specification that defines what the various entities associated with the system are allowed to do and how they should be implemented. Communication protocols and / or parameters used for connectivity are also usually defined. One example of a communication system is UTRAN (3G radio). Other examples include the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) based on E-UTRAN radio access technology, and the so-called 5G system (5GS), which includes a 5G or Next Generation Core (NGC) and a 5G access network based on New Radio (NR) radio access technology. 5GS, including NR, is being standardized by the 3rd Generation Partnership Project (3GPP). Summary of the Invention

[0006] In a first aspect, an apparatus is provided, comprising components for: determining which of at least two lower-level radio units, co-located at a first position, wherein each lower-level radio unit is associated with a higher-level radio unit, has an optimal path to the associated higher-level radio unit; and causing the transmission power of the determined lower-level radio unit among the at least two lower-level radio units received at a user equipment to be higher than the transmission power of any of the other lower-level radio units among the at least two lower-level radio units received at the user equipment.

[0007] The component for increasing the transmit power of the determined lower-level radio unit among at least two lower-level radio units received at the user equipment relative to the transmit power of any of the other lower-level radio units among the other lower-level radio units received at the user equipment may include a component for increasing the transmit power of the determined distributed unit relative to the transmit power of any of the other lower-level radio units among the other lower-level radio units.

[0008] The components for ensuring that the transmit power of a determined lower-level radio unit among at least two lower-level radio units received at the user equipment is higher than the transmit power of any of the other lower-level radio units among the lower-level radio units received at the user equipment may include components for providing the user equipment with an indication of the offset of the received transmit power.

[0009] The offset can be a negative offset that can be applied to the transmit power received from any of the other lower-level radio units among at least two lower-level radio units.

[0010] The offset can be a positive offset that can be applied to the power received from at least two lower-level radio units among the identified lower-level radio units.

[0011] The device may include components for providing an indication of offset to user equipment in a broadcast channel or dedicated signaling.

[0012] At least two lower-level radio units can be co-located on the satellite.

[0013] The relative increase in transmission power may be based on at least one of the trajectory of a satellite and the trajectory of a second satellite with additional lower-level radio units, wherein the additional lower-level radio units are potential target serving radio units for user equipment and currently serving higher-level radio units connected to user equipment.

[0014] The determination may be based on at least one of the satellite's trajectory and the trajectory of a second satellite with additional lower-level radio units, wherein the additional lower-level radio units are potential target serving radio units for user equipment and currently serving higher-level radio units connected to the user equipment.

[0015] The relative increase in transmission power can be based on at least one of the location of the user equipment and the transmission power of the signal received from each of the higher-level radio units at at least two lower-level radio units.

[0016] The determination may be based on at least one of the following: the location of the user equipment, the transmission power of the signal received from each of the higher-level radio units at at least two lower-level radio units, the delay at the higher-level radio units, and the capability of each of the higher-level radio units.

[0017] The optimal path can be defined by switching performance.

[0018] Each lower-level radio unit may include a next-generation NodeB distributed unit (gNB-DU).

[0019] Each higher-level radio unit may include a next-generation NodeB centralized unit, gNB-CU.

[0020] Each higher-level radio unit in a higher-level radio unit can be located in a different location.

[0021] In a second aspect, a method is provided, comprising: determining which of at least two lower-level radio units co-located at a first location, wherein each lower-level radio unit is associated with a higher-level radio unit, has an optimal path to the associated higher-level radio unit; and causing the transmission power of the determined lower-level radio unit among the at least two lower-level radio units received at a user equipment to be higher than the transmission power of any of the other lower-level radio units among the at least two lower-level radio units received at the user equipment.

[0022] Making the transmit power of the determined lower-level radio unit among at least two lower-level radio units received at the user equipment higher than the transmit power of any of the other lower-level radio units among the other lower-level radio units received at the user equipment may include increasing the transmit power of the determined distributed unit relative to the transmit power of any of the other lower-level radio units among the other lower-level radio units.

[0023] Making the transmit power of a determined lower-level radio unit among at least two lower-level radio units received at the user equipment higher than the transmit power of any of the other lower-level radio units among the lower-level radio units received at the user equipment may include providing the user equipment with an indication of the offset of the received transmit power.

[0024] The offset can be a negative offset that can be applied to the transmit power received from any of the other lower-level radio units among at least two lower-level radio units.

[0025] The offset can be a positive offset that can be applied to the power received from at least two lower-level radio units among the identified lower-level radio units.

[0026] This method may include providing an offset indication to the user equipment in a broadcast channel or dedicated signaling.

[0027] At least two lower-level radio units can be co-located on the satellite.

[0028] The relative increase in transmission power may be based on at least one of the trajectory of a satellite and the trajectory of a second satellite with additional lower-level radio units, wherein the additional lower-level radio units are potential target serving radio units for user equipment and currently serving higher-level radio units connected to user equipment.

[0029] The determination may be based on at least one of the satellite's trajectory and the trajectory of a second satellite with additional lower-level radio units, wherein the additional lower-level radio units are potential target serving radio units for user equipment and currently serving higher-level radio units connected to the user equipment.

[0030] The relative increase in transmission power can be based on at least one of the location of the user equipment and the transmission power of the signal received from each of the higher-level radio units at at least two lower-level radio units.

[0031] The determination may be based on at least one of the following: the location of the user equipment, the transmission power of the signal received from each of the higher-level radio units at at least two lower-level radio units, the delay at the higher-level radio units, and the capability of each of the higher-level radio units.

[0032] The optimal path can be defined by switching performance.

[0033] Each lower-level radio unit may include a next-generation NodeB distributed unit (gNB-DU).

[0034] Each higher-level radio unit may include a next-generation NodeB centralized unit, gNB-CU.

[0035] Each higher-level radio unit in a higher-level radio unit can be located in a different location.

[0036] In a third aspect, an apparatus is provided, comprising: at least one processor and at least one memory including computer program code, the at least one memory and the computer program code being configured together with the at least one processor to cause the apparatus to at least: determine which of at least two lower-level radio units co-located at a first location, wherein each lower-level radio unit is associated with a higher-level radio unit, has an optimal path to the associated higher-level radio unit; and cause the transmission power of the determined lower-level radio unit among the at least two lower-level radio units received at a user equipment to be higher than the transmission power of any of the other lower-level radio units among the at least two lower-level radio units received at the user equipment.

[0037] The device can be configured to increase the transmission power of the determined distributed unit relative to the transmission power of any of the other lower-level radio units in the lower-level radio units.

[0038] The device can be configured to provide the user equipment with an indication of the offset of the received transmit power.

[0039] The offset can be a negative offset that can be applied to the transmit power received from any of the other lower-level radio units among at least two lower-level radio units.

[0040] The offset can be a positive offset that can be applied to the power received from at least two lower-level radio units among the identified lower-level radio units.

[0041] The device is configured to provide an offset indication to user equipment in a broadcast channel or dedicated signaling.

[0042] At least two lower-level radio units can be co-located on the satellite.

[0043] The relative increase in transmission power may be based on at least one of the trajectory of a satellite and the trajectory of a second satellite with additional lower-level radio units, wherein the additional lower-level radio units are potential target serving radio units for user equipment and currently serving higher-level radio units connected to user equipment.

[0044] The device can be configured to determine, based on at least one of the satellite's trajectory and the trajectory of a second satellite with additional lower-level radio units, which of at least two lower-level radio units co-located at a first position has the optimal path to an associated higher-level radio unit, wherein the additional lower-level radio unit is a potential target serving radio unit for the user equipment and is connected to the user equipment's currently serving higher-level radio unit.

[0045] The relative increase in transmission power can be based on at least one of the location of the user equipment and the transmission power of the signal received from each of the higher-level radio units at at least two lower-level radio units.

[0046] The device can be configured to determine, based on at least one of the following: the location of the user equipment, the transmission power of the signal received from each of the higher-level radio units at at least two lower-level radio units, the delay at the higher-level radio units, and the capabilities of each of the higher-level radio units, which of the at least two lower-level radio units co-located at a first location has the optimal path to the associated higher-level radio unit.

[0047] The optimal path can be defined by switching performance.

[0048] Each lower-level radio unit may include a next-generation NodeB distributed unit (gNB-DU).

[0049] Each higher-level radio unit may include a next-generation NodeB centralized unit, gNB-CU.

[0050] Each higher-level radio unit in a higher-level radio unit can be located in a different location.

[0051] In a fourth aspect, a computer-readable medium is provided, comprising program instructions for causing a device to perform at least the following operations: determining which of at least two lower-level radio units co-located at a first position, wherein each lower-level radio unit is associated with a higher-level radio unit, has an optimal path to the associated higher-level radio unit; and causing the transmission power of the determined lower-level radio unit among the at least two lower-level radio units received at a user equipment to be higher than the transmission power of any of the other lower-level radio units among the at least two lower-level radio units received at the user equipment.

[0052] Making the transmit power of the determined lower-level radio unit among at least two lower-level radio units received at the user equipment higher than the transmit power of any of the other lower-level radio units among the other lower-level radio units received at the user equipment may include increasing the transmit power of the determined distributed unit relative to the transmit power of any of the other lower-level radio units among the other lower-level radio units.

[0053] Making the transmit power of a determined lower-level radio unit among at least two lower-level radio units received at the user equipment higher than the transmit power of any of the other lower-level radio units among the lower-level radio units received at the user equipment may include providing the user equipment with an indication of the offset of the received transmit power.

[0054] The offset can be a negative offset that can be applied to the transmit power received from any of the other lower-level radio units among at least two lower-level radio units.

[0055] The offset can be a positive offset that can be applied to the power received from at least two lower-level radio units among the identified lower-level radio units.

[0056] The device can be triggered to provide an offset indication to the user equipment in a broadcast channel or dedicated signaling.

[0057] At least two lower-level radio units can be co-located on the satellite.

[0058] The relative increase in transmission power may be based on at least one of the trajectory of a satellite and the trajectory of a second satellite with additional lower-level radio units, wherein the additional lower-level radio units are potential target serving radio units for user equipment and currently serving higher-level radio units connected to user equipment.

[0059] The determination may be based on at least one of the satellite's trajectory and the trajectory of a second satellite with additional lower-level radio units, wherein the additional lower-level radio units are potential target serving radio units for user equipment and currently serving higher-level radio units connected to the user equipment.

[0060] The relative increase in transmission power can be based on at least one of the location of the user equipment and the transmission power of the signal received from each of the higher-level radio units at at least two lower-level radio units.

[0061] The determination may be based on at least one of the following: the location of the user equipment, the transmission power of the signal received from each of the higher-level radio units at at least two lower-level radio units, the delay at the higher-level radio units, and the capability of each of the higher-level radio units.

[0062] The optimal path can be defined by switching performance.

[0063] Each lower-level radio unit may include a next-generation NodeB distributed unit (gNB-DU).

[0064] Each higher-level radio unit may include a next-generation NodeB centralized unit, gNB-CU.

[0065] Each higher-level radio unit in a higher-level radio unit can be located in a different location.

[0066] In a fifth aspect, a non-transitory computer-readable medium is provided, the non-transitory computer-readable medium comprising program instructions for causing a device to at least execute the method according to the second aspect.

[0067] Many different embodiments have been described above. It should be understood that other embodiments can be provided by combining any two or more of the above embodiments. Attached Figure Description

[0068] Embodiments will now be described by way of example only with reference to the accompanying drawings, in which:

[0069] Figure 1 A schematic diagram of an example communication system including a base station and multiple communication devices is shown;

[0070] Figure 2 A schematic diagram of an example mobile communication device is shown;

[0071] Figure 3 A schematic diagram of an example control device is shown;

[0072] Figure 4 A schematic diagram of an example dual-DU split architecture is shown;

[0073] Figure 5 It shows Figure 4 The event flow of the example architecture;

[0074] Figure 6 An example signaling flow for intra-CU inter-DU mobility is shown;

[0075] Figure 7 An example signaling flow for inter-gNB handover is shown;

[0076] Figure 8 A flowchart of a method according to an example embodiment is shown;

[0077] Figure 9 A schematic diagram illustrating a power boost according to an example embodiment is shown;

[0078] Figure 10 The relationship between relative power increase and satellite trajectory is shown;

[0079] Figure 11 The relationship between relative power increase and satellite trajectory is shown. Detailed Implementation

[0080] Before explaining the examples in detail, refer to Figures 1 to 3 A brief explanation of some general principles of wireless communication systems and mobile communication devices will help in understanding the underlying technology of the examples.

[0081] In such Figure 1 In the illustrated wireless communication system 100, mobile communication devices or user equipment (UEs) 102, 104, 105 are provided with wireless access via at least one base station (e.g., a next-generation NB, gNB) or similar wireless transmission and / or reception node or point. The base station may be controlled or assisted by at least one suitable controller device to realize its operation and manage the mobile communication devices communicating with the base station. The controller device may be located in the radio access network (e.g., wireless communication system 100) or core network (CN) (not shown) and may be implemented as a central device or its functions may be distributed across several devices. The controller device may be part of the base station and / or provided by a separate entity such as a radio network controller. Figure 1In the diagram, control units 108 and 109 are shown controlling corresponding macro base stations 106 and 107. The base station control units can be interconnected with other control entities. The control units are typically equipped with memory capacity and at least one data processor. Control units and functions can be distributed among multiple control units. In some systems, the control units may be additionally or alternatively located in the radio network controller.

[0082] exist Figure 1 In the diagram, base stations 106 and 107 are shown connected to a wider communication network 113 via gateway 112. Additional gateway functionality may be provided to connect to another network.

[0083] Smaller base stations 116, 118, and 120 may also connect to network 113, for example, via a separate gateway function and / or via the controller of a macro station. Base stations 116, 118, and 120 may be pico or femto-scale base stations, etc. In this example, stations 116 and 118 are connected via gateway 111, while station 120 is connected via controller device 108. In some embodiments, smaller stations may not be provided. Smaller base stations 116, 118, and 120 may be part of a second network (e.g., a WLAN) and may be WLAN access points (APs).

[0084] Communication devices 102, 104, and 105 can access the communication system based on various access technologies, such as Code Division Multiple Access (CDMA) or Wideband CDMA (WCDMA). Other non-limiting examples include Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), and various schemes such as Interleaved Frequency Division Multiple Access (IFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and Space Division Multiple Access (SDMA).

[0085] One example of a wireless communication system is the architecture standardized by the 3rd Generation Partnership Project (3GPP). The latest 3GPP-based development is often referred to as Long Term Evolution (LTE) of Universal Mobile Telecommunications System (UMTS) Radio Access Technology. The various development phases of the 3GPP specification are called releases. The latest development of LTE is often referred to as LTE-Advanced (LTE-A). LTE (LTE-A) employs a radio mobility architecture called Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and a core network called Evolved Packet Core (EPC). Base stations in such systems are called Evolved or Enhanced Node Bs (eNBs) and provide E-UTRAN features such as user plane packet data fusion / radio link control / media access control / physical layer protocols (PDCP / RLC / MAC / PHY) and control plane radio resource control (RRC) protocol termination. Other examples of radio access systems include those provided by base stations based on technologies such as Wireless Local Area Networks (WLANs) and / or WiMax (Microwave Access Global Interoperability). Base stations can provide coverage for an entire cell or similar radio service area. The core network components include the Mobility Management Entity (MME), the Serving Gateway (S-GW), and the Packet Gateway (P-GW).

[0086] An example of a suitable communication system is the 5G or NR concept. The network architecture in NR can be similar to that of advanced LTE. Base stations in an NR system can be called next-generation node Bs (gNBs). Changes in network architecture can depend on the need to support various radio technologies and more granular QoS support, as well as some on-demand requirements for QoS levels, such as those for supporting QoE from the user's perspective. Furthermore, network-aware services and applications, and service and application-aware networks, can bring about changes to the architecture. These relate to information-centric networks (ICNs) and user-centric content delivery networks (UC-CDNs). NR can use multiple-input multiple-output (MIMO) antennas, far more base stations or nodes than LTE (the so-called small cell concept), including macro sites operating in cooperation with smaller base stations, and may also employ various radio technologies to achieve better coverage and higher data rates.

[0087] Future networks can leverage Network Functions Virtualization (NFV), a network architecture concept that proposes virtualizing network node functions as "building blocks" or entities that can be operationally connected or linked together to provide services. Virtualized network functions (VNFs) can include one or more virtual machines running computer program code using standard or general-purpose servers instead of custom hardware. Cloud computing or data storage can also be utilized. In radio communications, this might mean that node operations are performed at least partially in servers, hosts, or nodes operatively coupled to a remote radio head. Node operations may also be distributed across multiple servers, nodes, or hosts. It should also be understood that the workforce allocation between core network operations and base station operations may differ from, or even not exist, in LTE.

[0088] An example 5G core network (CN) includes functional entities. The CN is connected to the UE via the radio access network (RAN). The UPF (User Plane Function), whose role is called PSA (PDU Session Anchor), can be responsible for forwarding frames back and forth between the DN (Data Network) and the tunnel established by 5G and directed towards (multiple) UEs exchanging services with the DN.

[0089] UPF is controlled by SMF (Session Management Function), which receives policies from PCF (Policy Control Function). CN may also include AMF (Access and Mobility Function).

[0090] Now refer to Figure 2 A more detailed description of possible mobile communication devices, Figure 2 A schematic partial cross-sectional view of a communication device 200 is shown. Such a communication device is generally referred to as a user equipment (UE) or terminal. Any device capable of transmitting and receiving radio signals can provide a suitable mobile communication device. Non-limiting examples include mobile stations (MS) or mobile devices (such as mobile phones or so-called "smartphones"), computers provided with wireless interface cards or other wireless interface facilities (e.g., USB dongles), personal data assistants (PDAs) or tablet computers provided with wireless communication capabilities, or any combination thereof. Mobile communication devices can provide, for example, communication for carrying data such as voice, email, text messages, multimedia, etc. Therefore, a variety of services can be supplied and provided to users via their communication devices. Non-limiting examples of these services include two-way or multi-way calling, data communication or multimedia services, or simply access to data communication network systems such as the Internet. Broadcast or multicast data can also be provided to users. Non-limiting examples of content include downloads, television and radio programs, videos, advertisements, various alarms, and other information.

[0091] In industrial applications, communication devices may be modems integrated into industrial actuators (e.g., robotic arms) and / or modems acting as Ethernet hubs, which will serve as connection points for one or more connected Ethernet devices (the connection may be wired or wireless).

[0092] Mobile devices are typically provided with at least one data processing entity 201, at least one memory 202, and other possible components 203 for use in the software and hardware-assisted execution of tasks they are designed to perform, including control of access to and communication with access systems and other communication devices. Data processing, storage, and other related control devices may be provided on a suitable circuit board and / or in a chipset. This feature is indicated by reference numeral 204. Users can control the operation of the mobile device through a suitable user interface such as a keyboard 205, voice commands, a touch-sensitive screen or touchpad, or combinations thereof. A display 208, a speaker, and a microphone may also be provided. Furthermore, mobile communication devices may include suitable connectors (wired or wireless) for connecting to other devices and / or for connecting external accessories (e.g., hands-free devices) to them.

[0093] Mobile device 200 can receive signals via air or radio interface 207 through appropriate means for receiving, and can transmit signals via appropriate means for transmitting radio signals. Figure 2 In this diagram, the transceiver device is schematically designated by box 206. The transceiver device 206 may be provided, for example, by means of radio components and an associated antenna arrangement. The antenna arrangement may be arranged inside or outside the mobile device.

[0094] Figure 3An example embodiment of a control device for a communication system is shown, which is coupled to and / or used to control access system stations (such as RAN nodes, eNBs, or gNBs), relay nodes, or core network nodes (such as MMEs, S-GWs, or P-GWs), or core network functions (such as AMFs / SMFs, servers, or hosts). This method can be embedded in a single control device or span multiple control devices. The control device can be integrated with or external to nodes or modules of the core network or RAN. In some embodiments, the base station includes a separate control device unit or module. In other embodiments, the control device can be other network elements, such as a radio network controller or a spectrum controller. In some embodiments, each base station can have such a control device as well as a control device disposed within the radio network controller. The control device 300 can be arranged to provide control over communications within the service area of ​​the system. The control device 300 includes at least one memory 301, at least one data processing unit 302, 303, and an input / output interface 304. Through this interface, the control device can be coupled to a receiver and transmitter of the base station. The receiver and / or transmitter can be implemented as a radio front-end or a remote radio head-end.

[0095] 3GPP is investigating how to enable non-terrestrial networks (NTNs) using new radio (NR). This work is detailed in research project TR 38.821 (Solutions for NR to support non-terrestrial networks). One area of ​​research is how to provide seamless connectivity for terrestrial UEs, i.e., providing continuous data connectivity without handover (and other) interruptions.

[0096] Currently, various architectural solutions are being investigated for three satellite classes: Geostationary Orbit (GEO), Low Earth Orbit (LEO), and High Altitude Platform Systems (HAPS). One solution is based on the splitting of the NR-enabled gNB Central Unit (gNB-CU, hereinafter also referred to as CU) and gNB Distributed Unit (gNB-DU, hereinafter also referred to as DU), where the CU is a higher-level radio unit (e.g., containing PDCP, RLC, and RRC layers) located on Earth, while the DU is a lower-level radio unit (e.g., containing PHY and MAC layers) located on the satellite. CU-DU splitting is facilitated via F1 interface used for ground station backhaul. A DU can connect to one CU at a time, while one CU can control multiple DUs. 3GPP TS 38.401 describes the CU-DU splitting architecture.

[0097] The following concerns non-terrestrial networks (i.e., LEO and HAPS) that are moving relative to the Earth. Because these satellites are moving, a DU (located on the satellite) needs to disconnect from its current serving CU (on Earth) and connect to the next CU (or at least the next ground station, which can connect to the current CU) at some point. It has been proposed to deploy a dual-DU configuration on the satellite, such that when one DU connects to the CU of the nearest “serving” ground station, the other DU can connect to the next determined “serving” CU / ground station. Dual DUs avoid closing the first F1 interface before establishing a new F1 interface, which reduces associated latency and interruptions in ongoing connections. The dual-DU configuration requires appropriate design to allow each satellite constellation and ground station location to have two simultaneously active feeder links to two different ground stations (within radio range).

[0098] If an NTN UE on Earth is equipped with Dual Connectivity (DC) capability, it can simultaneously connect to two DUs on the same satellite and experience seamless connectivity transitions from one ground station to another. This can be achieved by the UE performing a role swap from PCell to PSCell between the two DUs whenever the DU changes ground stations. NTN UEs with DC capability can also connect to two different satellites to further enhance connectivity. This assumes the latter DC option works similarly to traditional terrestrial 5G NR network deployments. The former DC option falls within the following scope.

[0099] Assuming a dual-DU deployment on a satellite combined with a DC UE, as described above, one issue is how the UE can choose between two DUs when it first powers on, initiates cell reselection, or transitions from RRC_Idle / RRC_Inactive to RRC_Connected. These two DUs are registered to the same PLMN and currently both provide coverage to the UE, but are connected to different CUs.

[0100] Since the two DUs are located on the same satellite and provide coverage to the same area on Earth (same antenna beam size), the propagation loss (path loss + shadowing fading) between the individual DU and the UE is expected to be the same for two DUs operating in the same frequency band (two at the same frequency or two frequencies close to each other). The UE can therefore randomly connect to one of the two DUs and thus also randomly select one of the two CUs.

[0101] The distances of the feeder links between two DUs can differ, and for performance optimization (e.g., latency, reliability), the shorter (optimal) feeder link is preferred. However, in the current setup, the UE will select the DU to the relevant CU and thus the feeder link based on the serving link, which does not show the difference in feeder links.

[0102] For UEs and satellites that have undergone the following steps, Figure 4 and Figure 5 The problem is illustrated in the image.

[0103] Figure 4 Region 401 is shown, in which the passing satellite experiences the shortest distance to the CU and the ground station (CU) of the satellite orbit covers 402.

[0104] Figure 5 It shows Figure 4 The event flow. The best connectivity flow is shown with thinner arrows, while the second-best connectivity flow is shown with thicker arrows.

[0105] Table 1 provides Figure 4 The event flow. The last two columns show the connectivity (CU change event) flow for two categories when the UE selects the best or second-best DU.

[0106] At time t0, a stationary UE appears in the area near CU2. Sat0 is currently the only satellite serving this area, and its two DUs are connected to CU1 and CU2 respectively. This means that the UE needs to select either CU1-DU or CU2-DU as its serving cell. CU2-DU is assumed to be selected because it is the best choice for optimizing feeder link performance and minimizing potential CU handover (see t2).

[0107] At time t1, Sat0 has completely entered the coverage area of ​​CU1 and is no longer connected to CU2, while Sat1 is now connected to both CU2 and CU3.

[0108] At time t2, as Sat0 (connected only to CU1) moves away, the UE is only within the coverage area of ​​Sat1 (connected to CU2). If the UE had already selected CU1-DU as its serving cell at t0, it will now experience a CU change when switching to Sat1.

[0109] At time t3, Sat1 is now in the position that Sat0 was in at t0, so the loop repeats.

[0110]

[0111]

[0112] Table 1

[0113] exist Figure 4 and Figure 5As shown in the example in Table 1, the UE at t0 can benefit from selecting CU2-DU instead of CU1-DU. By doing so, and assuming it remains stationary, it will avoid the later CU change at time t2, as highlighted above, and connect to the optimal feeder link. The challenge is how to ensure that the UE initially connects to the "optimal" CU, regardless of its location, with the aim of minimizing CU change mobility events.

[0114] Avoiding CU changes for each DU can be beneficial to the served UE, as CU changes would require the exchange of multiple messages between the satellite DU and the source and target CUs, resulting in non-zero data interruption latency on the service link to the UE. Since the CU-DU connection remains unchanged, these latency delays are not known from the terrestrial network because the DU cell typically does not move. However, since a connection to the target CU can be established first after the connection to the source CU is terminated (according to the current 5G NR Release 15 specification), and the one-way latency of a 600km altitude LEO satellite is at least 6ms, potential gaps can be estimated based on the process described below.

[0115] Figure 6 and Figure 7 The signaling flow for a two-way handshake is shown. In this case, the minimum gap will be 24ms.

[0116] Figure 6 The diagram illustrates the process of a UE moving from a source DU to a target DU, where both are connected to the same CU (i.e., a DU-to-CU change scenario). The process of a UE moving from one CU to another corresponds to a regular gNB-gNB handover, as shown in Figure 74, but includes F1 communication between the CU-DU pairs in the source and target gNBs. Note the time requirements for path transitions in the UPF.

[0117] Intra-CU mobility between DUs is better than inter-CU mobility because there is less signaling overhead and lower latency in the U plane.

[0118] During the initial access process in NR Release 15, the UE first obtains time-frequency synchronization with the cell through primary and secondary synchronization signals (PSS, SSS). These synchronization signals also enable the UE to determine the physical cell ID. PSS and SSS are synchronization signals and part of the PBCH block (SSB) that are periodically transmitted on each beam in NR. The Physical Broadcast Channel (PBCH) contains the Demodulation Reference Signal (DRMS), the Master Information Block, and System Information Block 1, which together provide the UE with sufficient information to attempt random access.

[0119] Before a UE can initiate a random access procedure, the target cell needs to be determined. In NR Release 15, the network has several mechanisms to prevent a UE from accessing a specific cell. For each access attempt, the UE must select an access identifier, and the network configures the access category (see 3GPP 22.261). The network broadcasts prohibition control information, which defines the combination of identifiers and categories of cells that can be attempted for access. Additionally, the UE needs to determine whether the cell is part of a "Roaming No-Tracking Area" (3GPP 38.300).

[0120] Cell selection is based on measurements of the SSB of each detectable cell in each predefined frequency band. This selection is based on downlink received power (RSRP / RSRQ) among suitable cells. According to 38.213, the UE can assume that the SSS, PBCHDMRS, and PBCH data have the same energy per resource element (EPRE), and that the ratio between PSS EPRE and SSS EPRE is 0 or 3 dB.

[0121] If the cell is suitable (or acceptable, see 3GPP 38.300), the UE can attempt to connect.

[0122] For cell reselection (valid for RRC_Idle and RRC_Inactive), several criteria can be used for network-guided UE selection. For intra-frequency reselection, the UE must prioritize cells based on measured SSB-based measurements (RSRP / RSRQ), while for inter-frequency reselection, frequency can be given priority. Finally, the network can provide blacklists for both intra-frequency and inter-frequency cells (3GPP 38.300).

[0123] The following is an excerpt from TS 38.304 related to cell selection and cell reselection (within frequency) standards:

[0124] 5.2.3.2 Community Selection Criteria

[0125] The selection criterion S for the community is satisfied under the following conditions:

[0126] Srxlev > 0 and Squal > 0

[0127] in

[0128] Srxlev=Q rxlevmead -(Q rxlevmin +Q rxlevminoffset )-P compensation -Qoffset temp

[0129] Squal = Q qualmeas -(Q qualmin +Qqualminoffset -Qoffset temp

[0130] in

[0131]

[0132]

[0133] 5.2.4.6 Criteria for Cell Reselection within and between Frequency Groups of Equal Priority

[0134] Service Community Ranking Criteria R s R of adjacent cells n Defined as:

[0135] R s =Q meas，s +Q hyst -Qoffset temp

[0136] R n =Q meas，n -Qoffset-Qoffset temp

[0137] in

[0138]

[0139]

[0140] The UE shall sort all cells that meet the cell selection criterion S defined in 5.2.3.2.

[0141] It should be obtained by deriving Q meas,n and Q meas,s Furthermore, the R value is calculated using the average RSRP result, and the cells are ranked according to the R criterion specified above.

[0142] Cell range extension (CRE) is a technique commonly used to extend the range of a small cell relative to a macro cell, which requires offsetting a large power imbalance between the two layers (e.g., typically transmitting at 40dBm versus 30dBm). The UE applies an offset (based on the CRE value provided by the network, e.g., 5dB) to the measured RSRP power of the small cell to artificially boost its received power, thus making the small cell's coverage area "breath" and preferentially selected when within its "breathing" area. In this concept, given a pair of small and macro cells, the CRE value is set to a static value, and the CRE offset applies to RRC_Connected UEs and is provided to the UE via RRC signaling; that is, it is ineffective for cell (re)selection in RRC_Inactive / Idle.

[0143] Figure 8 A flowchart according to an example embodiment is shown.

[0144] In the first step S1, the method includes determining which of at least two lower-level radio units co-located at a first position, wherein each lower-level radio unit is associated with a higher-level radio unit, has the optimal path to the associated higher-level radio unit.

[0145] In the second step S2, the method includes making the transmit power of the determined lower-level radio unit among the at least two lower-level radio units received at the user equipment higher than the transmit power of any of the other lower-level radio units among the at least two lower-level radio units received at the user equipment.

[0146] The lower-level radio unit can be a gNB-DU. The higher-level radio unit can be a gNB-CU.

[0147] At least two lower-level radio units can be co-located on the satellite. Each of the higher-level radio units can be located at a different location.

[0148] The optimal path can be defined by switching performance, that is, maximizing the time spent on its corresponding CU, which means minimizing the number of CU switching.

[0149] Determining which of the at least two lower-level radio units has the optimal path to the associated higher-level radio unit can be based on at least one of the following: the location of the user equipment, the transmit power (e.g., optimal receive power) of the signal received from each of the higher-level radio units at the at least two lower-level radio units, the delay at the higher-level radio unit (e.g., minimum delay), and the capability (e.g., minimum capability) of each of the higher-level radio units.

[0150] In an alternative or adjacent location, when at least two lower-level radio units are co-located on a satellite, determining which of the at least two lower-level radio units has the optimal path to the associated higher-level radio unit may be based on at least one of the satellite's trajectory and the trajectory of a second satellite with another lower-level radio unit, wherein the other lower-level radio unit is a potential target serving radio unit for the user equipment and is connected to the user equipment's currently serving higher-level radio unit.

[0151] In other words, DUs can dynamically and relative to each other adjust their downlink transmit power, depending on which is the best choice for the UE, so that a UE in RRC_Inactive / Idle connects to the most suitable CU-DU. The increase or boost in transmit power can be real or virtual.

[0152] Figure 9 The overall concept of downlink transmit power boosting is illustrated schematically. At time 1, stationary UE1 on the Earth's surface receives a DU1-Uu power boost to guide UE1 to DU1 on the satellite (connected to CU1 via a backhaul / feed link). At time 0, stationary UE2 receives a DU2-Uu power boost to guide UE2 to DU2 on the satellite (connected to CU2 via a backhaul / feed link).

[0153] refer to Figure 8 and Figure 9 The described method applies a dynamic downlink transmit power boost (real or virtual) to guide the UE to select the optimal DU from two or more DUs, which have similar radio characteristics (e.g., co-location and operation at similar carrier frequencies). The optimal DU is the DU that connects to the CU that minimizes or avoids subsequent CU changes; that is, it results in the minimum CU change and the shortest feeder link for the fixed UE.

[0154] Without DU power enhancement, the UE may experience CU changes (see...) Figure 4 and Figure 5 And Table 1), which comes at a high cost in terms of more signaling and higher latency (see Table 1). Figure 6 and Figure 7The UE may also experience longer delays on the feeder link.

[0155] Downlink transmit power enhancement can be either a real power enhancement or a virtual enhancement.

[0156] Virtual power boosting can be achieved by the UE based on network signaling offset measurements. This method may include providing the UE with an indication of the offset for the received transmit power.

[0157] In one example implementation, the network (e.g., the DU) instructs the UE to apply a dynamic DU power offset (DUPO) to a measured SSB-based RSRP value to virtually boost the power of the optimal DU relative to another (co-location) DU. This virtual boost requires the UE to prefer the boosted DU over the unboosted DU, for example, for cell (re)selection.

[0158] In the case of virtual boost, in one example implementation, the network pre-provides a UE with virtual power boost capability, and then provides (e.g., via SIB) the parameters (e.g., power offset) to be used in the virtual boost capability through the UE with RRC_Inactive / Idle.

[0159] The offset can be negative or positive. If a DU's power is actually boosted compared to another DU, the UE can select the suboptimal DU during initial cell selection because the RSRP will be the same. Cell reselection is then required to move to the optimal DU, and simultaneously, the UE may have already established a connection with the suboptimal DU (CU), leading to a costly CU change. To ensure this doesn't happen, the unboosted DU needs a "negative offset" for cell selection, which can be achieved by increasing Q. rxlevmin Or Q rxlevminoffset To achieve this.

[0160] For cell reselection, the upgraded DU needs a positive offset relative to the un-upgraded DU (via Q). offset (To ensure that the promoted DU is ranked higher than the unpromoted DU.)

[0161] Offset indication can be provided via dedicated signaling or in the broadcast channel. Offset can also be provided via existing cell (re)selection parameters. Therefore, all UEs within the coverage area of ​​a satellite with dual DUs will use the same boosting and power boosting parameters. Alternatively, in an adjacent or supplementary location, the network can provide offset values ​​at regular intervals in its SIB.

[0162] The method may include increasing the transmission power of the determined lower-level radio unit relative to the transmission power of any other lower-level radio unit.

[0163] In another example implementation, the best DU (from the perspective of the CU feeder link, i.e., the determined lower-level radio unit among at least two lower-level radio units) will dynamically boost the actual transmit power of its broadcast channel (e.g., PSS / SSS / PBCH) relative to another DU (not selected), so that the UE will measure a higher SSB-based RSRP value (downlink receive power level), based on which it will prefer the boosted DU (and, for example, will (re)select the cell or initiate a connection request to it).

[0164] The relative increase in transmission power can be based on at least one of the location of the user equipment and the transmission power of signals received from the associated higher-level radio unit at at least two lower-level radio units.

[0165] For example, when a DU dynamically boosts its real power relative to another DU on the same satellite, the DU will base the downlink power boost level on the received power from its ground station (feeder link). That is, the higher the received power (and similarly, the shorter the distance), the higher the transmit power that guides the UE to connect to it. Virtual power boost can use the same method as feeder link received power to control the power boost level.

[0166] This approach may be beneficial because when the satellite (with dual DUs) is far from the ground station (providing F1 backhaul to the associated CU), the associated CU is unlikely to be the best choice for the UE served by the satellite.

[0167] The solution is as follows Figure 10 As shown, Figure 10 This illustrates the relative power boost of another on-board DU. The satellite paths for the dual DUs are shown as arrow X. Circles indicate the areas where the CU is closest to the satellite. In this example, CU1-DU increases its power relative to the distance (or received power) to the location of CU1 on Earth. The shorter the distance (or received power), the higher the transmit power. As the satellite approaches CU2, the power level of CU1-DU decreases to baseline, while the power of CU2-DU increases. At the boundary between CU2 and CU3, the satellite will apply similar transmit power to both DUs to make it a random choice for the UE.

[0168] Figure 10 The shape of the power boost relative to another DU on the same satellite shown is for illustrative purposes only. The relative power boost can take any form and can be continuous or discrete.

[0169] Alternatively or in an adjacent location, a relative increase in transmit power can be based on at least one of the trajectory of a satellite and the trajectory of a second satellite with additional lower-level radio units, wherein the additional lower-level radio units are potential target serving radio units for the user equipment and currently serving higher-level radio units connected to the user equipment. For example, downlink power enhancement can be based on deterministic satellite trajectories, satellite constellations, and knowledge of the location of fixed ground stations (and CU locations).

[0170] Figure 11 This is an example of how the power boost varies with the satellite trajectory. The paths of the dual-DU satellites in the region where the CU is closest to the satellite are shown by arrows X and Y. Path X is a direct passover, and path Y is a partial passover. The relative power boost of the other airborne DU shown on the y-axis of the graph is a function of the path.

[0171] Changing the downlink transmit power may cause a change in the UE's receive power, leading the UE to select the "best" CU, i.e., the lower-layer radio unit with the best path to the associated higher-layer radio unit. However, the UE can estimate different propagation losses unless notified to the DU that the downlink transmit power has changed. The UE uses propagation loss for uplink transmit power control (UL TPC), where propagation loss is compensated by a specific factor: α (3GPP 38.213). For example, if the downlink transmit power increases by 3dB, the UE will estimate a 3dB decrease in propagation loss and thus reduce the uplink transmit power by 3dB. This may result in a degraded uplink performance.

[0172] In NR, the ServingCellConfigCommon information element (3GPP 38.331) of System Information Block 1 (SIB1) optionally includes ss-PBCH-BlockPower, which defines the downlink transmit power of the SSB. SIB1 transmits periodically in the PDSCH at 160ms intervals, but with variable repetition within this window. To ensure proper UL TPC, ss-PBCH-BlockPower may need to be broadcast more frequently when using downlink transmit power boosting. This depends on the satellite constellation, particularly the number of satellites and their altitude.

[0173] This method can be found in the reference. Figure 3 Implemented in the described control device.

[0174] An apparatus may include components for: determining which of at least two lower-level radio units, co-located at a first position, wherein each lower-level radio unit is associated with a higher-level radio unit, has an optimal path to the associated higher-level radio unit; and causing the transmission power of the determined lower-level radio unit among the at least two lower-level radio units received at the user equipment to be higher than the transmission power of any of the other lower-level radio units among the at least two lower-level radio units received at the user equipment.

[0175] It should be understood that the device may include or be coupled to other units or modules, such as radio components or radio heads, used for transmission and / or reception. Although these devices have been described as a single entity, different modules and memories may be implemented in one or more physical or logical entities.

[0176] Note that while embodiments have been described with respect to non-terrestrial networks (NTNs), similar principles can be applied to other networks and communication systems in which a higher-layer radio unit separates from the lower-layer radio unit architecture. Therefore, although certain example architectures of wireless networks, technologies, and standards have been described above by way of example, these embodiments can be applied to any other suitable form of communication system besides those shown and described herein.

[0177] It should also be noted in this document that although exemplary embodiments have been described above, various changes and modifications can be made to the disclosed solutions without departing from the scope of the invention.

[0178] Generally, various example embodiments can be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. Some aspects of the invention can be implemented in hardware, while others can be implemented in firmware or software that can be executed by a controller, microprocessor, or other computing device, but the invention is not limited thereto. Although various aspects of the invention may be illustrated and described as block diagrams, flowcharts, or using some other graphical representation, it is well understood that, by way of non-limiting example, the blocks, apparatuses, systems, techniques, or methods described herein can be implemented in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0179] Example embodiments of the present invention can be implemented by computer software executable by a mobile device's data processor, such as in a processor entity, or by hardware, or by a combination of software and hardware. The computer software or program (also referred to as a program product, including software routines, applets, and / or macros) can be stored in any device-readable data storage medium, and they include program instructions for performing specific tasks. The computer program product may include one or more computer-executable components that, when the program is run, are configured to perform the embodiment. The one or more computer-executable components may be at least one piece of software code or a portion thereof.

[0180] Additionally, it should be noted that any block in the logical flow diagram can represent a program step, or an interconnected logic circuit, block, and function, or a combination of program steps and logic circuits, blocks, and functions. Software can be stored on physical media such as memory blocks implemented within memory chips or processors, magnetic media such as hard disks or floppy disks, and optical media such as DVDs and their data variants, CDs. Physical media are non-transitory media.

[0181] The memory can be of any type suitable for the local technological environment and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The data processor can be of any type suitable for the local technological environment and, by way of non-limiting example, can include general-purpose computers, special-purpose computers, microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), FPGAs, gate-level circuits, and processors based on multi-core processor architectures.

[0182] The exemplary embodiments of the present invention can be practiced in various components such as integrated circuit modules. The design of integrated circuits is largely a highly automated process. Complex and powerful software tools can be used to transform logic-level designs into semiconductor circuit designs ready to be etched and formed on semiconductor substrates.

[0183] The foregoing description has provided a complete and informative description of exemplary embodiments of the invention by way of non-limiting example. However, various modifications and alterations will become apparent to those skilled in the art when read in conjunction with the accompanying drawings and appended claims, given the foregoing description. Nevertheless, all such and similar modifications taught in this invention will still fall within the scope of the invention as defined in the appended claims. In fact, other embodiments exist that combine one or more embodiments with any other embodiments discussed above.

Claims

1. A communication apparatus comprising components for the following operations: Determine which of at least two distributed units co-located on a satellite, where each distributed unit is associated with a different centralized unit in a centralized unit, has the optimal path to the associated centralized unit, wherein each centralized unit is located at a different location, and wherein the optimal path is defined by handover performance; and The transmission power of the determined distributed unit among the at least two distributed units received at the user equipment is higher than the transmission power of any of the other distributed units among the at least two distributed units received at the user equipment.

2. The apparatus of claim 1, wherein the component for causing the transmission power of the determined distributed unit among the at least two distributed units received at the user equipment to be higher than the transmission power of any of the other distributed units among the distributed units received at the user equipment comprises: A component for increasing the transmission power of a determined distributed unit relative to the transmission power of any other distributed unit in the distributed unit.

3. The apparatus of claim 1 or claim 2, wherein the component for making the transmission power of the determined distributed unit among the at least two distributed units received at the user equipment higher than the transmission power of any of the other distributed units among the distributed units received at the user equipment comprises: A component for providing the user equipment with an indication of the offset of the received transmit power.

4. The apparatus of claim 3, wherein the offset is a negative offset of the transmit power that can be applied to any of the other distributed units among the at least two distributed units.

5. The apparatus of claim 3, wherein the offset is a positive offset applicable to the power received from the determined distributed unit among the at least two distributed units.

6. The apparatus of claim 3, further comprising a component for providing the indication of the offset to the user equipment in a broadcast channel or dedicated signaling.

7. The apparatus of claim 2, wherein the relative increase in transmission power is based on at least one of the following: the trajectory of the satellite and the trajectory of a second satellite having an additional distributed unit, wherein the additional distributed unit is a potential target service radio unit for the user equipment and a current service centralized unit connected to the user equipment.

8. The apparatus of claim 1, wherein the determination is based on at least one of the following: the trajectory of the satellite and the trajectory of a second satellite having an additional distributed unit, wherein the additional distributed unit is a potential target service radio unit for the user equipment and a current service centralized unit connected to the user equipment.

9. The apparatus of claim 2, wherein the relative increase in transmission power is based on at least one of the following: the location of the user equipment and the transmission power of the signal received at the at least two distributed units from each of the centralized units.

10. The apparatus according to any one of claims 1 to 2, wherein the determination is based on at least one of the following: the location of the user equipment, the transmission power of the signal received at the at least two distributed units from each of the centralized units, the delay at the centralized unit, and the capability of each of the centralized units.

11. A method of communication, comprising: Determine which of at least two distributed units co-located on a satellite, each of which is associated with a different centralized unit in a centralized unit, has the optimal path to the associated centralized unit, wherein each centralized unit is located at a different location, and wherein the optimal path is defined by handover performance; as well as The transmission power of the determined distributed unit among the at least two distributed units received at the user equipment is higher than the transmission power of any of the other distributed units among the at least two distributed units received at the user equipment.

12. An apparatus for communication, comprising: At least one processor and at least one memory including computer program code, said at least one memory and said computer program code being configured together with said at least one processor to cause the device to at least: Determine which of at least two distributed units co-located on a satellite, each of which is associated with a different centralized unit in a centralized unit, has the optimal path to the associated centralized unit, wherein each centralized unit is located at a different location, and wherein the optimal path is defined by handover performance; as well as The transmission power of the determined distributed unit among the at least two distributed units received at the user equipment is higher than the transmission power of any of the other distributed units among the at least two distributed units received at the user equipment.

13. A computer-readable medium comprising program instructions for causing a device to perform at least the following operations: Determine which of at least two distributed units co-located on a satellite, where each distributed unit is associated with a different centralized unit in a centralized unit, has the optimal path to the associated centralized unit, wherein each centralized unit is located at a different location, and wherein the optimal path is defined by handover performance; and The transmission power of the determined distributed unit among the at least two distributed units received at the user equipment is higher than the transmission power of any of the other distributed units among the at least two distributed units received at the user equipment.

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