EP4710456A1 - Method for ntn-tn mobility enhancements - Google Patents

Abstract

Method for NTN-TN mobility enhancements characterized by that a UE receives up-to-date, accurate TN coverage information from the network through UE specific signaling, before it moves to RRC idle mode or RRC inactive state.

Description

TITLE

Method for NTN-TN mobility enhancements

TECHNNICAL FIELD

The present disclosure is generally related to mobile communications and, more particularly, to User Equipment (UE) mobility between a Non-Terrestrial Network (NTN) and a Terrestrial Network (TN).

BACKGROUND

Limited or insufficient mobile network coverage in remote areas is still a key challenge across many regions of the world. The 3rd Generation Partnership Project (3GPP) has specified solutions for mobile communications based on Non-Terrestrial Networks (NTNs), which provide increased coverage as well as service availability. Further, NTNs can complement Terrestrial Networks (TNs) and form an integrated mobile communications system.

However, there are several challenges to be addressed when serving mobile UEs with such an integrated NTN-TN mobile communications system. For example, NTNs may serve geographical areas where TNs of different Mobile Network Operators (MNOs) are deployed and coverage areas of TNs partly overlap with NTN coverage areas. Further, NTNs may consist of spaceborne elements, such as LEO satellites, which operate in Non-Geosynchronous Satellite Orbits (NGSOs) and where the LEO satellite movements result in moving coverage areas. Thus, UEs on ground that try to select and connect to a mobile network may observe so-called “earth-moving” radio cells, which are operated by LEO satellites.

In 5G NR Radio Resource Control (RRC) protocol specification TS 38.331 the scheme according to Fig. 1 is explained. In both RRC idle mode state (RRCJDLE - meaning no RRC connection) and inactive state (RRCJNACTIVE - meaning suspended RRC connection), a UE performs measurements of neighboring cells and can perform cell re-selection. In RRC connected state (RRC_CONNECTED), the UE mobility is controlled by the network and handovers can be initiated. In the RRC idle mode state, UE paging is initiated by the core network (CN). In RRCJNACTIVE, UE paging is initiated by the New Generation Radio Access Network (NG-RAN). To page a UE, it's location must be known. In the RRC idle mode state, this is achieved by the Tracking Area (TA) procedure. In the RRC inactive state, this is the RAN-based Notification Area (RNA) procedure and the UE may initiate RNA updates.

The communication protocol used to manage the notification area updates for UEs, namely UE RNAU, is described in TS 38.304. The UE performs a RAN-based notification area update (RNAU) periodically or when the UE selects a cell that does not belong to the configured RNA. If the UE finds a more suitable cell, according to the cell reselection criteria, it reselects onto that cell and camps on it. If the new cell does not belong to at least one tracking area to which the UE is registered, location registration is performed. In the RRC inactive state, if the new cell does not belong to the configured RNA, an RNA update procedure is performed.

Further, the network communicates with the UE via Non-Access-Stratum (NAS) protocol, which is described in TS 24.301 , to manage UE mobility, including tracking area updates. Thus, NAS signaling can also be used to provide TN coverage information.

The procedure concerning UE’s release preference and preferred RRC state is described in TS 38.331. The UE sets the contents of the UE assistance information message as to include an information of release preference and to set a preferred RRC state to the desired RRC state on transmission of the UE assistance information message. Some information elements are added to the UE assistance information, for example to convey the capabilities supported by the UE for the power saving preferences (IE PowSav-Parameters), to set miscellaneous other configurations (IE OtherConfig) or to inform the ground base station (gNB) about the UE's preference to leave the RRC connected state releasePreferenceConfig

The procedure concerning UE Assistance Information is described in TS 38.331 and is illustrated in fig. 2. The purpose of this procedure is for the UE to inform the network on various internal status, including its preference on the RRC state. However, for NTN-TN cell reselection, TN coverage indications via broadcast are baseline. For signaling the TN coverage, the corresponding geographical area information is provided by broadcast signaling by the network via a list of (possibly overlapping) areas, where each area is defined using reference location coordinates and a radius (where the area is meant to describe a group of cells, not just a single one). Conclusion hereout is that TN coverage indications describe a group of potentially overlapping cell areas. Further, there may be TN cells and/or frequencies that are owned and operated by different MNOs or service providers, which the UE is not supposed to use, e.g., since its subscription is constraint to certain service providers. Typically, each service provider uses and broadcast a unique Public Land Mobile Network Identifier (PLMN ID), which enables the UE to determine whether it can connect to a certain network or not. Such a scenario is illustrated in Fig. 3.

The associated problem is that UEs under NTN coverage waste energy when trying to detect or measure TN cells or frequencies, which are not present in certain geographical areas. This is due to fact that cell reselection priority for TN cells and/or frequencies is typically higher than those of NTN cells and/or frequencies. Further, TN cells under the coverage of one NTN cell can potentially belong to service providers to which the UE is not subscribed and, thus, not authorized to connect to. As a result, the UE’s power consumption significantly increases. Furthermore, a base station (gNB) may not know the UE’s movement direction and speed when UE is in the RRC idle mode or RRC inactive state. As a result, it could be difficult for the base station to configure and provide accurate and up-to-date TN coverage data. For example, the base station (gNB) functionality may reside in the NTN ground infrastructure (e.g., ground-based satellite gateway) or onboard a satellite.

This application solves the problem by that the UE receives accurate and Public Land Mobile Network (PLMN) specific TN coverage information from the network through UE specific signaling (e.g., RRC release message), before it moves to RRC idle mode or inactive state. Further, the UE provides specific movement data, so that network further enhances TN coverage data signaling. The advantages of employing this invention are that it enhances network signaling, reduces UE power consumption, improves mobility support and cell reselection accuracy.

BIEF DESCRIPTION OF THE FIGURES

Fig. 1 depicts UE RRC states related protocol, according to current standard specifications,

Fig. 2 depicts UE assistance information procedure, according to current standard specifications,

Fig. 3 depicts a NTN scenario, where a plurality of UEs are under NTN coverage, Fig. 4 depicts a flowchart diagram of the method, according to invention, Fig. 5 depicts UE side flowchart diagram of one embodiment of the method, Fig. 6 depicts the gNB side flowchart diagram of one embodiment of the method.

DETAILED DESCRIPTION

The detailed description set forth below, with reference to annexed drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In particular, although terminology from 3GPP 5G NR may be used in this disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the invention.

Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

In some embodiments, a more general term “network node” may be used and may correspond to any type of radio network node or any network node, which communicates with a UE (directly or via another node) and/or with another network node. Examples of network nodes are NodeB, MeNB, ENB, a network node belonging to MCG or SCG, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNodeB, gNodeB, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS), core network node (e.g. Mobile Switching Center (MSC), Mobility Management Entity (MME) etc.), Operations & Maintenance (O&M), Operations Support System (OSS), Self- Optimized Network (SON), positioning node (e.g. Evolved- Serving Mobile Location Centre (E-SMLC)), Minimization of Drive Tests (MDT), test equipment (physical node or software), etc.

In some embodiments, the non-limiting term user equipment (UE) or wireless device may be used and may refer to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile communication system. Examples of UE are target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, PDA, PAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, UE category Ml, UE category M2, ProSe UE, V2V UE, V2X UE, etc.

Additionally, terminologies such as base station/gNodeB and UE should be considered non-limiting and do in particular not imply a certain hierarchical relation between the two; in general, “gNodeB” could be considered as device 1 and “UE” could be considered as device 2 and these two devices communicate with each other over some radio channel. In the following the transmitter or receiver could be either gNodeB (gNB), or UE.

As will be appreciated by one skilled in the art, aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Accordingly, embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects.

For example, the disclosed embodiments may be implemented as a hardware circuit comprising custom very-large-scale integration (“VLSI”) circuits or gate arrays, off- the-shelf semiconductors such as logic chips, transistors, or other discrete components. The disclosed embodiments may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like. As another example, the disclosed embodiments may include one or more physical or logical blocks of executable code which may, for instance, be organized as an object, procedure, or function.

Furthermore, embodiments may take the form of a program product embodied in one or more computer readable storage devices storing machine readable code, computer readable code, and/or program code, referred hereafter as code. The storage devices may be tangible, non- transitory, and/or non-transmission. The storage devices may not embody signals. In a certain embodiment, the storage devices only employ signals for accessing code.

Any combination of one or more computer readable medium may be utilized. The computer readable medium may be a computer readable storage medium. The computer readable storage medium may be a storage device storing the code. The storage device may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

More specific examples (a non-exhaustive list) of the storage device would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (“RAM”), a read-only memory (“ROM”), an erasable programmable read-only memory (“EPROM” or Flash memory), a portable compact disc read-only memory (“CD-ROM”), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

Code for carrying out operations for embodiments may be any number of lines and may be written in any combination of one or more programming languages including an object- oriented programming language such as Python, Ruby, Java, Smalltalk, C++, or the like, and conventional procedural programming languages, such as the “C” programming language, or the like, and/or machine languages such as assembly languages. The code may execute entirely on the user’s computer, partly on the user’s computer, as a stand-alone software package, partly on the user’s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user’s computer through any type of network, including a local area network (“LAN”), wireless LAN (“WLAN”), or a wide area network (“WAN”), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider (“ISP”)). Furthermore, the described features, structures, or characteristics of the embodiments may be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of an embodiment. Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments” unless expressly specified otherwise. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise.

Aspects of the embodiments are described below with reference to schematic flowchart diagrams and/or schematic block diagrams of methods, apparatuses, systems, and program products according to embodiments. It will be understood that each block of the schematic flowchart diagrams and/or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and/or schematic block diagrams, can be implemented by code. This code may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart diagrams and/or block diagrams.

The code may also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function/act specified in the flowchart diagrams and/or block diagrams.

The code may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices to produce a computer implemented process such that the code which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart diagrams and/or block diagrams.

The flowchart diagrams and/or block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatuses, systems, methods, and program products according to various embodiments. In this regard, each block in the flowchart diagrams and/or block diagrams may represent a module, segment, or portion of code, which includes one or more executable instructions of the code for implementing the specified logical function(s).

It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated figures.

Although various arrow types and line types may be employed in the flowchart and/or block diagrams, they are understood not to limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted embodiment. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and code.

The description of elements in each figure may refer to elements of proceeding figures. Like numbers refer to like elements in all figures, including alternate embodiments of like elements.

Fig. 1 depicts current standard UE RRC states related protocol. Fig. 2 depicts current standard UE assistance information procedure. Fig. 3 depicts an NTN scenario, where a plurality of UEs are under NTN coverage.

Fig. 4 depicts a flowchart diagram of the method, according to invention. Before moving to RRC idle mode or RRC inactive state, a UE receives up-to-date, accurate TN coverage information from network through UE specific signaling.

Fig. 5 depicts the UE side flowchart of one embodiment of the method. In case the UE moves to RRC inactive state, it receives updated, accurate TN coverage data through a dedicated signaling message. Further, it is checked, if a RA-SDT and/or CG-SDT procedure is triggered. If yes, UE provides UEAssistancelnformation regarding specific movement and direction. Furthermore, it is checked, if RNAU is triggered. If yes, UE receives updated, accurate TN coverage data. Then the UE side method terminates.

In essence, UE receives more accurate and PLMN-specific TN coverage information from the network through UE specific signaling (e.g., RRC release message), before it moves to RRC idle mode or RRC inactive state. For example, if UE is in RRC connected state and its releasePreference is “inactive”, then the network initiates move to inactive state via RRC release message with suspendConfig, e.g., if there is no downlink DL data for UE for a certain time period.

In the RRC release message, the network provides more accurate TN coverage data including PLMN area details corresponding to the UE’s subscription. The UE subscription or contract are taken into account and only TN coverage data corresponding to PLMN IDs, which the UE can actually use, are provided.

In the inactive state, the UE performs cell re-selection and can relax measurements for TN cells/frequencies/PLMNs according to received TN coverage data received via broadcast as well as RRC signaling.

RRC inactive UE has a better knowledge about its specific movement and direction. Hence, UE sends such information to the network via UE assistance information, for example.

If UE is in RRC connected state and its releasePreference is “inactive”, then the network initiates move to inactive state via RRC release message with suspendConfig, e.g., if there is no downlink DL data for UE for a certain time period.

In the inactive state, the UE performs cell re-selection (based on System Information message, e.g., SIB2/3/4/5). If a new selected cell does not belong to the configured RNA, an RNA update procedure (including UE’s resume ID) is performed.

The RNA update procedure (RRC connection resume request) will trigger the network to provide more accurate TN coverage data including PLMN area details corresponding to the UE’s subscription. The network can decide to move the UE to connected state, inactive state, or idle state mode.

The network responds with an RRC connection resume/release message (with more accurate TN coverage data including PLMN area details corresponding to the UE’s subscription). The UE performs cell re-selection and can relax measurements for TN cells, frequencies or PLMNs according to the TN coverage data received via broadcast of system information message as well as UE-specific RRC signaling.

RRC inactive UE provides such information during RA-SDT and/or CG-SDT procedure. RA-SDT procedure stands for Random Access based Small Data Transmission, meaning data transmission using shared radio resources of the random access procedure. CG-SDT procedure stands for Configured Grant based Small Data Transmission, meaning data transmission using preconfigured radio resources.

Network configures accurate TN coverage based on the UE assistance information (where data may only be valid for current RA-SDT/CG-SDT procedure). Whenever UE triggers a new RA-SDT and/or CG-SDT procedure, UE provides updated UE assistance information (if any changes are determined).

RRC inactive UE performs RNAU, if it moves to a cell that is not part of the currently assigned RNA. RNAU stands for RAN-based Notification Area Update procedure.

The UE receives the updated TN coverage information from the network during the RNA update procedure (e.g., RNA update procedure response message).

UE in RRC idle mode performs Tracking Area Update TAU when UE enters in tracking area, which is not included within the list of tracking areas with which the UE has registered. The UE receives the updated, accurate TN coverage information from the network during the TAU update procedure (e.g., TAU update procedure response message).

Fig. 6 depicts the gNB side flowchart of the method embodiment. gNB determines, if it is the case to move the UE to RRC inactive or idle state. Here, the gNB considers UE assistance information (including releasePreferenceConfig), which the UE provided earlier, e.g., when network connection was established, for determining the UE’s preferred release state. If this is the case, the gNB provides updated, accurate TN coverage data in RRC release message. If the UE triggers a RA-SDT and/or CG- SDT procedure, the gNB receives UE assistance information, including movement and direction-related information, based on which the gNB provides updated, accurate TN coverage data accordingly. Then, it is checked, if gNB receives RNAU. If yes, it provides updated, accurate TN coverage data in the response of RNAU, and after that the flow terminates. RA-SDT and/or CG-SDT procedures may not necessarily be followed by RNAll or TAU procedures. Those procedures may also be triggered independently, e.g., due to UE mobility.

The benefits of this application are an enhanced network signaling. Coarse TN coverage data via broadcast is complemented by accurate TN coverage data via dedicated RRC signaling, which help to reduce UE power consumption and improve mobility support in idle and inactive states.

Abbreviations

CG-SDT Configured Grant based Small Data Transmission

CN Core Network PLMN Public Land Mobile Network

RA - SDT Random Access based Small Data Transmission

RNAU RAN-based Notification Area Update

RRC INACTIVE Radio Resource Control inactive state

RRCJDLE Radio Resource Control idle mode state TAU Tracking Area Update

UE User Equipment

Claims

1. Method for NTN-TN mobility enhancements characterized by that a UE receives up-to-date, accurate TN coverage information from a network through UE specific signaling, before it moves to RRC idle mode or RRC inactive state.

2. Method according to claim 1 , characterized by that a UE receives PLMN-specific TN coverage information.

3. Method according to claims 1 or 2, characterized by that the UE sends the movement- and direction-related information to the network.

4. Method according to claims 1 to 3, characterized by that RRC inactive UE provides movement- and direction-related information during RA-SDT and/or CG- SDT procedure.

5. Method according to claims 1 to 4, characterized by that the network configures updated, accurate TN coverage based on the UE’s movement- and direction- related information.

6. Method according to claim 1 to 5, characterized by that, whenever the UE triggers a new RA-SDT and/or CG-SDT procedure, the UE provides updated UE assistance information, such as movement and direction data, if any changes are determined.

7. Method according to claim 1 , characterized by that the UE receives the updated TN coverage information from the network during the RAN-based Notification Area Update (RNAU) procedure.

8. Method according to claim 1 , characterized by that the UE receives the updated, accurate TN coverage information from the network during the Tracking Area Update (TAU) procedure.

9. Apparatus for NTN-TN mobility enhancements, the apparatus comprising a wireless transceiver, a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of the claims 1 to 8.

10. User Equipment comprising an apparatus according to claim 9.

11. Base station comprising an apparatus according to claim 9.

12. Wireless communication system, comprising at least one base station (gNB) communicating with at least one UE, wherein the base station comprises a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of claims 1 to 8, wherein the UE comprises a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of the claims 1 to 8.