WO2019009578A1

WO2019009578A1 - Method and apparatus for selecting rat-based positioning scheme in wireless communication system

Info

Publication number: WO2019009578A1
Application number: PCT/KR2018/007494
Authority: WO
Inventors: Jongwoo HONG; Oanyong LEE
Original assignee: Lg Electronics Inc.
Priority date: 2017-07-03
Filing date: 2018-07-03
Publication date: 2019-01-10

Abstract

A method and apparatus for selecting a radio access technology (RAT) based positioning scheme in a wireless communication system is provided. A user equipment (UE) receives information on a RAT-based selection condition for selecting either one of a first positioning scheme or a second positioning scheme from a network, and selects either one of the first positioning scheme or the second positioning scheme according to the RAT-based selection condition. The first and second positioning schemes are a long-term evolution (LTE) based positioning scheme and a new radio access technology (NR) based positioning scheme.

Description

METHOD AND APPARATUS FOR SELECTING RAT-BASED POSITIONING SCHEME IN WIRELESS COMMUNICATION SYSTEM

The present invention relates to wireless communications, and more particularly, to a method and apparatus for selecting a radio access technology (RAT)-based positioning scheme in a wireless communication system.

3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. 3GPP has to identify and develop the technology components needed for successfully standardizing the new RAT timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU radio communication sector (ITU-R) international mobile telecommunications (IMT)-2020 process. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usage scenarios, requirements and deployment scenarios including enhanced mobile broadband (eMBB), massive machine-type-communications (mMTC), ultra-reliable and low latency communications (URLLC), etc. The NR shall be inherently forward compatible.

Positioning functionality provides a means to determine the geographic position and/or velocity of a user equipment (UE) based on measuring radio signals. The position information may be requested by and reported to a client (e.g. an application) associated with the UE, or by a client within or attached to the core network. The position information shall be reported in standard formats, such as those for cell-based or geographical co-ordinates, together with the estimated errors (uncertainty) of the position and velocity of the UE and, if available, the positioning method (or the list of the methods) used to obtain the position estimate.

The legacy positioning scheme until Rel-14 only considers LTE. UE positioning should be enhanced in order to support NR-based positioning scheme.

In an aspect, a method for selecting a radio access technology (RAT) based positioning scheme by a user equipment (UE) in a wireless communication system is provided. The method includes receiving, by the UE, information on a RAT-based selection condition for selecting either one of a first positioning scheme or a second positioning scheme from a network, selecting, by the UE, either one of the first positioning scheme or the second positioning scheme according to the RAT-based selection condition, transmitting, by the UE, a request for assistance data of the selected positioning scheme to the network, and receiving, by the UE, the assistance data of the selected positioning scheme from the network.

In another aspect, a user equipment (UE) in a wireless communication system is provided. The UE includes a memory, a transceiver, and a processor, operably coupled to the memory and the transceiver, that controls the transceiver to receive information on a radio access technology (RAT) based selection condition for selecting either one of a first positioning scheme or a second positioning scheme from a network, selects either one of the first positioning scheme or the second positioning scheme according to the RAT-based selection condition, controls the transceiver to transmit a request for assistance data of the selected positioning scheme to the network, and controls the transceiver to receive the assistance data of the selected positioning scheme from the network.

The UE can select appropriate radio access technology (RAT) based positioning scheme.

FIG. 1 shows an example of a wireless communication system to which technical features of the present invention can be applied.

FIG. 2 shows another example of a wireless communication system to which technical features of the present invention can be applied.

FIG. 3 shows a block diagram of a user plane protocol stack.

FIG. 4 shows a block diagram of a control plane protocol stack.

FIG. 5 shows an architecture in evolved packet system (EPS) applicable to positioning of a UE with E-UTRAN access.

FIG. 6 shows an example of a LPP capability transfer procedure.

FIG. 7 shows an example of a LPP assistance data transfer procedure.

FIG. 8 shows an example of a LPP location information transfer procedure.

FIG. 9 shows an example of an error handling procedure.

FIG. 10 shows an example of an abort procedure.

FIG. 11 shows options 3/3a/3x of deployment scenarios for tight interworking between LTE and NR.

FIG. 12 shows options 4/4a of deployment scenarios for tight interworking between LTE and NR.

FIG. 13 shows options 7/7a/7x of deployment scenarios for tight interworking between LTE and NR.

FIG. 14 shows an example of a method for selecting a RAT-based positioning scheme according to an embodiment of the present invention.

FIG. 15 shows another example of a method for selecting a RAT-based positioning scheme according to an embodiment of the present invention.

FIG. 16 shows a wireless communication system to implement an embodiment of the present invention.

The technical features described below may be used by a communication standard by the 3rd generation partnership project (3GPP) standardization organization, a communication standard by the institute of electrical and electronics engineers (IEEE), etc. For example, the communication standards by the 3GPP standardization organization include long-term evolution (LTE) and/or evolution of LTE systems. The evolution of LTE systems includes LTE-advanced (LTE-A), LTE-A Pro, and/or 5G new radio (NR). The communication standard by the IEEE standardization organization includes a wireless local area network (WLAN) system such as IEEE 802.11a/b/g/n/ac/ax. The above system uses various multiple access technologies such as orthogonal frequency division multiple access (OFDMA) and/or single carrier frequency division multiple access (SC-FDMA) for downlink (DL) and/or uplink (DL). For example, only OFDMA may be used for DL and only SC-FDMA may be used for UL. Alternatively, OFDMA and SC-FDMA may be used for DL and/or UL.

FIG. 1 shows an example of a wireless communication system to which technical features of the present invention can be applied. Specifically, FIG. 1 shows a system architecture based on an evolved-UMTS terrestrial radio access network (E-UTRAN). The aforementioned LTE is a part of an evolved-UTMS (e-UMTS) using the E-UTRAN.

Referring to FIG. 1, the wireless communication system includes one or more user equipment (UE; 10), an E-UTRAN and an evolved packet core (EPC). The UE 10 refers to a communication equipment carried by a user. The UE 10 may be fixed or mobile. The UE 10 may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, etc.

The E-UTRAN consists of one or more base station (BS) 20. The BS 20 provides the E-UTRA user plane and control plane protocol terminations towards the UE 10. The BS 20 is generally a fixed station that communicates with the UE 10. The BS 20 hosts the functions, such as inter-cell radio resource management (MME), radio bearer (RB) control, connection mobility control, radio admission control, measurement configuration/provision, dynamic resource allocation (scheduler), etc. The BS may be referred to as another terminology, such as an evolved NodeB (eNB), a base transceiver system (BTS), an access point (AP), etc.

A downlink (DL) denotes communication from the BS 20 to the UE 10. An uplink (UL) denotes communication from the UE 10 to the BS 20. A sidelink (SL) denotes communication between the UEs 10. In the DL, a transmitter may be a part of the BS 20, and a receiver may be a part of the UE 10. In the UL, the transmitter may be a part of the UE 10, and the receiver may be a part of the BS 20. In the SL, the transmitter and receiver may be a part of the UE 10.

The EPC includes a mobility management entity (MME), a serving gateway (S-GW) and a packet data network (PDN) gateway (P-GW). The MME hosts the functions, such as non-access stratum (NAS) security, idle state mobility handling, evolved packet system (EPS) bearer control, etc. The S-GW hosts the functions, such as mobility anchoring, etc. The S-GW is a gateway having an E-UTRAN as an endpoint. For convenience, MME/S-GW 30 will be referred to herein simply as a "gateway," but it is understood that this entity includes both the MME and S-GW. The P-GW hosts the functions, such as UE Internet protocol (IP) address allocation, packet filtering, etc. The P-GW is a gateway having a PDN as an endpoint. The P-GW is connected to an external network.

The UE 10 is connected to the BS 20 by means of the Uu interface. The UEs 10 are interconnected with each other by means of the PC5 interface. The BSs 20 are interconnected with each other by means of the X2 interface. The BSs 20 are also connected by means of the S1 interface to the EPC, more specifically to the MME by means of the S1-MME interface and to the S-GW by means of the S1-U interface. The S1 interface supports a many-to-many relation between MMEs / S-GWs and BSs.

FIG. 2 shows another example of a wireless communication system to which technical features of the present invention can be applied. Specifically, FIG. 2 shows a system architecture based on a 5G new radio access technology (NR) system. The entity used in the 5G NR system (hereinafter, simply referred to as "NR") may absorb some or all of the functions of the entities introduced in FIG. 1 (e.g. eNB, MME, S-GW). The entity used in the NR system may be identified by the name "NG" for distinction from the LTE.

Referring to FIG. 2, the wireless communication system includes one or more UE 11, a next-generation RAN (NG-RAN) and a 5th generation core network (5GC). The NG-RAN consists of at least one NG-RAN node. The NG-RAN node is an entity corresponding to the BS 10 shown in FIG. 1. The NG-RAN node consists of at least one gNB 21 and/or at least one ng-eNB 22. The gNB 21 provides NR user plane and control plane protocol terminations towards the UE 11. The ng-eNB 22 provides E-UTRA user plane and control plane protocol terminations towards the UE 11.

The 5GC includes an access and mobility management function (AMF), a user plane function (UPF) and a session management function (SMF). The AMF hosts the functions, such as NAS security, idle state mobility handling, etc. The AMF is an entity including the functions of the conventional MME. The UPF hosts the functions, such as mobility anchoring, protocol data unit (PDU) handling. The UPF an entity including the functions of the conventional S-GW. The SMF hosts the functions, such as UE IP address allocation, PDU session control.

The gNBs and ng-eNBs are interconnected with each other by means of the Xn interface. The gNBs and ng-eNBs are also connected by means of the NG interfaces to the 5GC, more specifically to the AMF by means of the NG-C interface and to the UPF by means of the NG-U interface.

On the system of FIG. 1 and/or FIG. 2, layers of a radio interface protocol between the UE and the network (e.g. NG-RAN and/or E-UTRAN) may be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system.

FIG. 3 shows a block diagram of a user plane protocol stack. FIG. 4 shows a block diagram of a control plane protocol stack.

Referring to FIG. 3 and FIG. 4, a physical (PHY) layer belonging to L1. The PHY layer offers information transfer services to media access control (MAC) sublayer and higher layers. The PHY layer offers to the MAC sublayer transport channels. Data between the MAC sublayer and the PHY layer is transferred via the transport channels. Between different PHY layers, i.e., between a PHY layer of a transmission side and a PHY layer of a reception side, data is transferred via the physical channels.

The MAC sublayer belongs to L2. The main services and functions of the MAC sublayer include mapping between logical channels and transport channels, multiplexing/de-multiplexing of MAC service data units (SDUs) belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels, scheduling information reporting, error correction through hybrid automatic repeat request (HARQ), priority handling between UEs by means of dynamic scheduling, priority handling between logical channels of one UE by means of logical channel prioritization (LCP), and padding. The MAC sublayer offers to the radio link control (RLC) sublayer logical channels.

The RLC sublayer belong to L2. The RLC sublayer supports three transmission modes, i.e. transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). The main services and functions of the RLC sublayer depend on the transmission mode and include transfer of upper layer PDUs, sequence numbering independent of the one in PDCP (UM and AM), error correction through ARQ (AM only), segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs, reassembly of SDU (AM and UM), duplicate detection (AM only), RLC SDU discard (AM and UM), RLC re-establishment, and protocol error detection (AM only). The RLC sublayer offers to the packet data convergence protocol (PDCP) sublayer RLC channels;

The PDCP sublayer belong to L2. The main services and functions of the PDCP sublayer for the user plane include sequence numbering, header compression and decompression, transfer of user data, reordering and duplicate detection, PDCP PDU routing, retransmission of PDCP SDUs, ciphering, deciphering and integrity protection, PDCP SDU discard, PDCP re-establishment and data recovery for RLC AM, and duplication of PDCP PDUs. The main services and functions of the PDCP sublayer for the control plane include sequence numbering, ciphering, deciphering and integrity protection, transfer of control plane data, reordering and duplicate detection, and duplication of PDCP PDUs. The PDCP sublayer offers to the service data adaptation protocol (SDAP) sublayer RBs.

The SDAP sublayer belong to L2. The SDAP sublayer is only defined in the user plane. The main services and functions of SDAP include, mapping between a quality of service (QoS) flow and a data radio bearer (DRB), and marking QoS flow ID (QFI) in both DL and UL packets. The SDAP sublayer offers to 5GC QoS flows.

A radio resource control (RRC) layer belongs to L3. The RRC layer is only defined in the control plane. The RRC layer controls radio resources between the UE and the network. To this end, the RRC layer exchanges RRC messages between the UE and the BS. The main services and functions of the RRC layer include broadcast of system information related to AS and NAS, paging initiated by 5GC or NG-RAN, establishment, maintenance and release of an RRC connection between the UE and NG-RAN, security functions including key management, establishment, configuration, maintenance and release of RBs, mobility functions, QoS management functions, UE measurement reporting and control of the reporting, detection of and recovery from radio link failure, NAS message transfer to/from NAS from/to UE.

In other words, the RRC layer controls logical channels, transport channels, and physical channels in relation to the configuration, reconfiguration, and release of RBs. A RB refers to a logical path provided by L1 (PHY layer) and L2 (MAC/RLC/PDCP/SDAP sublayer) for data transmission between a UE and a network. Setting the RB means defining the characteristics of the radio protocol layer and the channel for providing a specific service, and setting each specific parameter and operation method. RB may be divided into signaling RB (SRB) and data RB (DRB). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

An RRC state indicates whether an RRC layer of the UE is logically connected to an RRC layer of the E-UTRAN. In LTE, when the RRC connection is established between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is in the RRC connected state (RRC_CONNECTED). Otherwise, the UE is in the RRC idle state (RRC_IDLE). In NR, the RRC inactive state (RRC_INACTIVE) is additionally introduced. RRC_INACTIVE may be used for various purposes. For example, the massive machine type communications (MMTC) UEs can be efficiently managed in RRC_INACTIVE. When a specific condition is satisfied, transition is made from one of the above three states to the other.

A predetermined operation may be performed according to the RRC state. For example, in RRC_IDLE and RRC_INACTIVE, public land mobile network (PLMN) selection, broadcast of system information (SI) and cell re-selection mobility are supported. However, in RRC_IDLE, paging for mobile terminated (MT) data is initiated by 5GC (i.e. core network (CN) paging), and paging area is managed by 5GC. Further, in RRC_IDLE, discontinuous reception (DRX) for CN paging is configured by NAS. On the other hand, in RRC_INACTIVE, paging is initiated by NG-RAN (i.e. RAN paging), and RAN-based notification area (RNA) is managed by NG-RAN. Further, DRX for RAN paging is configured by NG-RAN.

Meanwhile, in RRC_INACTVIVE and RRC_CONNECTED, 5GC-NG-RAN connection (both C/U-planes) is established for UE, and the UE AS context is stored in NG-RAN and the UE. However, in RRC_INACTIVE, NG-RAN merely knows the RNA which the UE belongs to. On the other hand, In RRC_CONNECTED, NG-RAN knows the cell which the UE belongs to. Furthermore, in RRC_CONNECTED, transfer of unicast data to/from the UE, and network controlled mobility, i.e. handover within NR and to/from E-UTRAN, including measurements are supported.

NAS layer is located at the top of the RRC layer. NAS control protocol is terminated in AMF on the network side. The NAS control protocol performs the functions, such as authentication, mobility management, security control.

The physical channels may be modulated according to OFDM processing and utilizes time and frequency as radio resources. The physical channels consist of a plurality of orthogonal frequency division multiplexing (OFDM) symbols in time domain and a plurality of subcarriers in frequency domain. One subframe consists of a plurality of OFDM symbols in the time domain. A resource block is a resource allocation unit, and consists of a plurality of OFDM symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific OFDM symbols (e.g. first OFDM symbol) of the corresponding subframe for a physical downlink control channel (PDCCH), i.e. L1/L2 control channel. A transmission time interval (TTI) is a basic unit of time used by a scheduler for resource allocation. The TTI may be defined in units of one or a plurality of slots, or may be defined in units of mini-slots.

The transport channels are classified according to how and with what characteristics data are transferred over the radio interface. DL transport channels include a broadcast channel (BCH) used for transmitting system information, a downlink shared channel (DL-SCH) used for transmitting user traffic or control signals, and a paging channel (PCH) used for paging a UE. UL transport channels include an uplink shared channel (UL-SCH) for transmitting user traffic or control signals and a random access channel (RACH) normally used for initial access to a cell.

Different kinds of data transfer services are offered by MAC sublayer. Each logical channel type is defined by what type of information is transferred. Logical channels are classified into two groups: control channels and traffic channels.

Control channels are used for the transfer of control plane information only. The control channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH) and a dedicated control channel (DCCH). The BCCH is a DL channel for broadcasting system control information. The PCCH is DL channel that transfers paging information, system information change notifications and indications of ongoing public warning system (PWS) broadcasts. The CCCH is a channel for transmitting control information between UEs and network. This channel is used for UEs having no RRC connection with the network. The DCCH is a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. This channel is used by UEs having an RRC connection.

Traffic channels are used for the transfer of user plane information only. The traffic channels include a dedicated traffic channel (DTCH). The DTCH is a point-to-point channel, dedicated to one UE, for the transfer of user information. The DTCH can exist in both UL and DL.

Regarding mapping between the logical channels and transport channels, in DL, BCCH can be mapped to BCH, BCCH can be mapped to DL-SCH, PCCH can be mapped to PCH, CCCH can be mapped to DL-SCH, DCCH can be mapped to DL-SCH, and DTCH can be mapped to DL-SCH. In UL, CCCH can be mapped to UL-SCH, DCCH can be mapped to UL- SCH, and DTCH can be mapped to UL-SCH.

UE positioning is described. Section 4, 5 and 7 of 3GPP TS 36.305 V14.1.0 (2017-03) may be referred.

The E-UTRAN may utilize one or more positioning methods in order to determine the position of an UE. Positioning the UE involves two main steps:

- signal measurements; and

- Position estimate and optional velocity computation based on the measurements.

The signal measurements may be made by the UE or the BS. The basic signals measured for terrestrial position methods are typically the E-UTRA radio transmissions. However, other methods may make use of other transmissions such as general radio navigation signals including those from global navigation satellites systems (GNSSs).

The positioning function should not be limited to a single method or measurement. That is, it should be capable of utilizing other standard methods and measurements, as such methods and measurements are available and appropriate, to meet the required service needs of the location service client. This additional information could consist of readily available E-UTRAN measurements.

The position estimate computation may be made by the UE or by the evolved serving mobile location center (E-SMLC).

The standard positioning methods supported for E-UTRAN access are as follows.

(1) Network-assisted GNSS methods: These methods make use of UEs that are equipped with radio receivers capable of receiving GNSS signals.

(2) Downlink positioning: The downlink positioning method, e.g. observed time difference of arrival (OTDOA), makes use of the measured timing of DL signals received from multiple transmission points (TPs) at the UE. The UE measures the timing of the received signals using assistance data received from the positioning server, and the resulting measurements are used to locate the UE in relation to the neighboring TPs.

(3) Enhanced cell identity (ID) method: In the cell ID (CID) positioning method, the position of an UE is estimated with the knowledge of its serving BS and cell. The information about the serving BS and cell may be obtained by paging, tracking area update, or other methods. Enhanced cell ID (E-CID) positioning refers to techniques which use additional UE and/or E-UTRAN radio resource and other measurements to improve the UE location estimate.

(4) Uplink positioning: The uplink positioning method, e.g. uplink time difference of arrival (UTDOA), makes use of the measured timing at multiple location measurement unit (LMUs) of UL signals transmitted from UE. The LMU measures the timing of the received signals using assistance data received from the positioning server, and the resulting measurements are used to estimate the location of the UE.

(5) Barometric pressure sensor method: The barometric pressure sensor method makes use of barometric sensors to determine the vertical component of the position of the UE. The UE measures barometric pressure, optionally aided by assistance data, to calculate the vertical component of its location or to send measurements to the positioning server for position calculation.

(6) WLAN method: The WLAN positioning method makes use of the WLAN measurements (AP identifiers and optionally other measurements) and databases to determine the location of the UE. The UE measures received signals from WLAN APs, optionally aided by assistance data, to send measurements to the positioning server for position calculation. Using the measurement results and a references database, the location of the UE is calculated.

(7) Bluetooth method: The Bluetooth positioning method makes use of Bluetooth measurements (beacon identifiers and optionally other measurements) to determine the location of the UE. The UE measures received signals from Bluetooth beacons. Using the measurement results and a references database, the location of the UE is calculated. The Bluetooth methods may be combined with other positioning methods (e.g. WLAN) to improve positioning accuracy of the UE.

(8) Terrestrial beacon system (TBS) method: A TBS consists method of a network of ground-based transmitters, broadcasting signals only for positioning purposes. The current type of TBS positioning signals are the metropolitan beacon system (MBS) signals and positioning reference signals (PRS). The UE measures received TBS signals, optionally aided by assistance data, to calculate its location or to send measurements to the positioning server for position calculation.

Hybrid positioning using multiple methods above is also supported. Standalone mode (e.g. autonomous, without network assistance) using one or more methods above is also supported.

The above positioning methods may be supported in UE-based, UE-assisted/E-SMLC-based, BS-assisted, and LMU-assisted/E-SMLC-based versions. Table 1 indicates which of these versions are supported for the standardized positioning methods.

Method	UE-based	UE-assisted(E-SMLC-based)	BS-assisted	LMU-assisted/ E-SMLC-based	SUPL
A-GNSS	Yes	Yes	No	No	Yes(UE-based and UE-assisted)
Downlink	No	Yes	No	No	Yes (UE-assisted)
E-CID	No	Yes	Yes	No	Yes (UE-assisted)
Uplink	No	No	No	Yes	No
Barometric	Yes	Yes	No	No	No
WLAN	Yes	Yes	No	No	Yes
Bluetooth	No	Yes	No	No	No
TBS	Yes	Yes	No	No	Yes (MBS)

Barometric pressure sensor, WLAN, Bluetooth, and TBS positioning methods based on MBS signals are also supported in standalone mode.

FIG. 5 shows an architecture in evolved packet system (EPS) applicable to positioning of a UE with E-UTRAN access. The MME receives a request for some location service associated with a particular target UE from another entity (e.g., gateway mobile location center (GMLC) or UE) or the MME itself decides to initiate some location service on behalf of a particular target UE (e.g. for an IP multimedia subsystem (IMS) emergency call from the UE). The MME then sends a location services request to an E-SMLC. The E-SMLC processes the location services request which may include transferring assistance data to the target UE to assist with UE-based and/or UE-assisted positioning and/or may include positioning of the target UE. For the uplink method, the E-SMLC processes the location services request which includes transferring configuration data to the selected LMU(s). The E-SMLC then returns the result of the location service back to the MME (e.g. a position estimate for the UE and/or an indication of any assistance data transferred to the UE). In the case of a location service requested by an entity other than the MME (e.g. UE or E-SMLC), the MME returns the location service result to this entity. The secure user plane location (SUPL) location platform (SLP) is the SUPL entity responsible for positioning over the user plane. A BS may control several TPs, such as remote radio heads, or PRS-only TPs for support of PRS-based TBS.

Positioning procedures in the E-UTRAN are modelled as transactions of the LTE positioning　protocol (LPP). The LPP is terminated between a target device (the UE in the control-plane case or SUPL　enabled terminal (SET) in the user-plane case) and a positioning server (the E-SMLC in the control-plane case or SLP in the user-plane case). It may use either the control- or user-plane protocols as underlying transport. A procedure consists of a single operation of one of the following types:

- Exchange of positioning capabilities;

- Transfer of assistance data;

- Transfer of location information (positioning measurements and/or position estimate);

- Error handling;

- Abort.

Parallel transactions are permitted (i.e. a new LPP transaction may be initiated, while another one is outstanding).

The protocol operates between a "target" and a "server". In the control-plane context, these entities are the UE and E-SMLC respectively. In the SUPL context, they are the SET and the SLP. A procedure may be initiated by either the target or the server. Both target initiated and server initiated procedures are supported.

FIG. 6 shows an example of a LPP capability transfer procedure. Capabilities in an LPP context refer to the ability of a target or server to support different position methods defined for LPP, different aspects of a particular position method (e.g. different types of assistance data for A-GNSS) and common features not specific to only one position method (e.g. ability to handle multiple LPP transactions). These capabilities are defined within the LPP protocol and transferred between the target and the server using LPP transport.

Referring to FIG. 6, in step S600, the server may send a request for the LPP related capabilities of the target. In step S610, the target transfers its LPP-related capabilities to the server. The capabilities may refer to particular position methods or may be common to multiple position methods.

FIG. 7 shows an example of a LPP assistance data transfer procedure. Assistance data may be transferred either by request or unsolicited. Assistance data delivery is supported only via unicast transport from server to target.

Referring to FIG. 7, in step S700, the target may send a request to the server for assistance data and may indicate the particular assistance data needed. In step S710, the server transfers assistance data to the target. The transferred assistance data should match any assistance data requested in step S700. In step S720, optionally, the server may transfer additional assistance data to the target in one or more additional LPP messages.

FIG. 8 shows an example of a LPP location information transfer procedure. The term "location information" applies both to an actual position estimate and to values used in computing position (e.g. radio measurements or positioning measurements). It is delivered either in response to a request or unsolicited.

In step S800, the server may send a request for location information to the target, and may indicate the type of location information needed and associated quality of service (QoS). In step S810, in response to step S800, the target transfers location information to the server. The location information transferred should match the location information requested in step S800. In step S820, optionally (e.g. if requested in step S810), the target may transfer additional location information to the server in one or more additional LPP messages.

FIG. 9 shows an example of an error handling procedure. The error handling procedure is used to notify the sending endpoint by the receiving endpoint that the receiving LPP message is erroneous or unexpected. This procedure is bidirectional at the LPP level. That is, either the target or the server may take the role of either endpoint.

In step S900, the target or server (indicated as "Target/Server" in FIG. 9) sends a LPP message to the other endpoint (indicated as "Server/Target" in FIG. 9). If the server or target ("Server/Target") detects that the receiving LPP message is erroneous or unexpected, in step S910, the server or target transfers error indication information to the other endpoint ("Target/Server").

FIG. 10 shows an example of an abort procedure. The abort procedure is used to notify the other endpoint by one endpoint to abort an ongoing procedure between the two endpoints. This procedure is bidirectional at the LPP level. That is, either the target or the server may take the role of either endpoint.

In step S1000, a LPP procedure is ongoing between target and server. If the server or target ("Server/Target") determines that the procedure must be aborted, and then, in step S1010, the server or target sends an LPP abort message to the other endpoint ("Target/Server") carrying the transaction ID for the procedure.

The LTE positioning protocol annex (LPPa) carries information between the eNB and the E-SMLC. It is used to support the following positioning functions:

- E-CID cases where assistance data or measurements are transferred from the eNB to the E-SMLC

- data collection from eNBs for support of downlink OTDOA positioning

- retrieval of UE configuration data from the eNBs for support of uplink (e.g. UTDOA) positioning.

The LPPa protocol is transparent to the MME. The MME routes the LPPa PDUs transparently based on a short routing ID corresponding to the involved E-SMLC node over S1 interface without knowledge of the involved LPPa transaction. It carries the LPPa PDUs over S1 interface either in UE associated mode or non-UE associated mode.

In the downlink positioning method, the UE position is estimated based on measurements taken at the UE of DL radio signals from multiple TPs (possibly including PRS-only TPs from a PRS-based TBS), along with knowledge of the geographical coordinates of the measured TPs and their relative downlink timing.

The following assistance data may be transferred from the E-SMLC to the UE.

- Physical cell IDs (PCIs), global cell IDs (GCIs), and TP IDs of candidate TPs for measurement;

- Timing relative to the serving (reference) TP of candidate TPs;

- PRS configuration of candidate TPs.

Table 1 shows an example of the PRS configuration, which is represented by PRS-Info information element (IE). The IE PRS-Info provides the information related to the configuration of PRS in a cell.

-- ASN1STARTPRS-Info ::= SEQUENCE { prs-Bandwidth ENUMERATED { n6, n15, n25, n50, n75, n100, ... }, prs-ConfigurationIndex INTEGER (0..4095), numDL-Frames ENUMERATED {sf-1, sf-2, sf-4, sf-6, ..., sf-add-v14xy}, ..., prs-MutingInfo-r9 CHOICE { po2-r9 BIT STRING (SIZE(2)), po4-r9 BIT STRING (SIZE(4)), po8-r9 BIT STRING (SIZE(8)), po16-r9 BIT STRING (SIZE(16)), ..., po32-v14xy BIT STRING (SIZE(32)), po64-v14xy BIT STRING (SIZE(64)), po128-v14xy BIT STRING (SIZE(128)), po256-v14xy BIT STRING (SIZE(256)), po512-v14xy BIT STRING (SIZE(512)), po1024-v14xy BIT STRING (SIZE(1024)) } OPTIONAL, -- Need OP [[ prsID-r14 INTEGER (0..4095) OPTIONAL, -- Need ON add-numDL-Frames-r14 INTEGER (1..160) OPTIONAL, -- Cond sf-add prsOccGroupLen-r14 ENUMERATED {g2, g4, g8, g16, g32, g64, g128,... } OPTIONAL, -- Cond Occ-Grp prsHoppingInfo-r14 CHOICE { nb2-r14 INTEGER (0.. maxAvailNarrowBands-Minus1-r14), nb4-r14 SEQUENCE (SIZE (3)) OF INTEGER (1.. maxAvailNarrowBands-Minus1-r14) } OPTIONAL -- Cond PRS-FH ]]}maxAvailNarrowBands-Minus1-r14 INTEGER ::= 15 -- Maximum number of narrowbands minus 1-- ASN1STOP

Referring to Table 2, The IE PRS-Info provides information on the bandwidth that is used to configure the positioning reference signals on (prs-Bandwidth), the positioning reference signals configuration index (prs-ConfigurationIndex), the number of consecutive downlink subframes with positioning reference signals (numDL-Frames), the PRS muting configuration of the cell (prs-MutingInfo), the PRS-ID (prsID), etc.

The following assistance data may be transferred from the eNB to the E-SMLC:

- PCI, GCI, and TP IDs of the TPs served by the eNB;

- Timing information of TPs served by the eNB;

- PRS configuration of the TPs served by the eNB;

- Geographical coordinates of the TPs served by the eNB

Multi radio access technology (RAT) dual connectivity (MR-DC) is described. NG-RAN supports MR-DC operation whereby a multiple Rx/Tx UE in RRC_CONNECTED is configured to utilize radio resources provided by two distinct schedulers. MR-DC is a generalization of the intra-E-UTRA DC. The two distinct schedulers are located in two different NG-RAN nodes connected via a non-ideal backhaul. One node of the two different NG-RAN nodes act as a master node (MN) and the other node of the two different NG-RAN nodes act as a secondary node (SN). That is, one scheduler is located in the MN, and the other scheduler is located in the SN. The two different NG-RAN provides either E-UTRA access (i.e. if the NG-RAN node is an ng-eNB) or NR access (i.e. if the NG-RAN node is a gNB). En-gNB is a node providing NR user plane and control plane protocol terminations towards the UE, and acting as SN in E-UTRAN-NR dual connectivity (EN-DC). Ng-eNB is a node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC. The MN and SN are connected via a network interface and at least the MN is connected to the core network. In this specification, MR-DC is designed based on the assumption of non-ideal backhaul between the different nodes but can also be used in case of ideal backhaul.

E-UTRAN supports MR-DC via EN-DC, in which a UE is connected to one eNB that acts as a MN and one en-gNB that acts as a SN. The eNB is connected to the EPC via the S1 interface and to the en-gNB via the X2 interface. The en-gNB might also be connected to the EPC via the S1-U interface and other en-gNBs via the X2-U interface.

NG-RAN supports NG-RAN E-UTRA-NR dual connectivity (NGEN-DC), in which a UE is connected to one ng-eNB that acts as a MN and one gNB that acts as a SN. The ng-eNB is connected to the 5GC and the gNB is connected to the ng-eNB via the Xn interface.

NG-RAN supports NR-E-UTRA dual connectivity (NE-DC), in which a UE is connected to one gNB that acts as a MN and one ng-eNB that acts as a SN. The gNB is connected to 5GC and the ng-eNB is connected to the gNB via the Xn interface.

In order to support MR-DC and/or tight interworking between LTE and NR, various deployment scenarios for LTE and NR may be considered.

FIG. 11 shows options 3/3a/3x of deployment scenarios for tight interworking between LTE and NR. FIG. 11-(a) may be referred to as Option 3, FIG. 11-(b) may be referred to as Option 3a, and FIG. 11-(c) may be referred to as Option 3x. In option 3/3a/3x, the LTE eNB is connected to EPC with non-standalone (NSA) NR. That is, the NR control plane is not connected to the EPC directly and is connected to the EPC via the LTE eNB. The NR user plane is connected to the EPC, through the LTE eNB (Option 3) or directly via the S1-U interface (Option 3a), or the directly connected user plane via the S1-U interface being split to LTE eNB from gNB (Option 3x). Options 3/3a/3x corresponds to the aforementioned EN-DC architecture.

FIG. 12 shows options 4/4a of deployment scenarios for tight interworking between LTE and NR. FIG. 12-(a) may be referred to as Option 4, and FIG. 12-(b) may be referred to as Option 4a. In option 4/4a, the gNB is connected to the NGC with non-standalone (NSA) E-UTRA. That is, the E-UTRA control plane is not connected to the NGC directly and is connected to the NGC via the gNB. The E-UTRA user plane is connected to the EPC, through the gNB (Option 4) or directly via the NG-U interface (Option 4a). Option 4/4a corresponds to a form in which E-UTRA and NR are reversed in Option 3/3a described above.

FIG. 13 shows options 7/7a/7x of deployment scenarios for tight interworking between LTE and NR. FIG. 13-(a) may be referred to as Option 7, FIG. 13-(b) may be referred to as Option 7a, and FIG. 13-(c) may be referred to as Option 7x. In option 7/7a/7x, the eLTE eNB (i.e. ng-eNB) is connected to the NGC with non-standalone NR. That is, the NR control plane is not connected to the NGC directly and is connected to the NGC via the eLTE eNB. The NR user plane is connected to the NGC, through the eLTE eNB (Option 7) or directly via the NG-U interface (Option 7a), or the directly connected user plane via the NG-U interface being split to eLTE eNB from gNB (Option 7x).

A problem of the prior art is described.

In the legacy positioning scheme until Rel-14, only LTE system was considered and NR system did not need to be supported. However, an architectural network interface between LTE and NR has been discussed in ongoing Rel-15 NR study/work item. For example, as described above in FIG. 11 to FIG. 13, MR-DC and/or tight interworking between LTE/NR has been discussed. A necessity of inter-RAT and RAT-based positioning scheme has been increasing.

Accordingly, the NR should specify support of UE positioning to comply with regulatory requirements. UE positioning for NR may be supported via RAT independent and E-UTRA RAT dependent positioning schemes, including transport of LPP messages between 5G-CN and UE through gNB, transport of LPPa type messages between 5G-CN and NG-RAN hosting E-UTRA (eNB), support of measurement gaps and idle periods for location related inter-RAT measurements. Furthermore, UE positioning for NR may be supported via network based NR CID and cell portion positioning, including definition of messages and transport between 5G-CN and NG-RAN hosting NR (gNB).

In perspective of the UE, while the UE has capabilities for both LTE and NR, the UE can access either LTE or NR. In perspective of the network (i.e. E-SMLC), the network can provide both LTE-based positioning scheme (e.g. LPP/LPPa) and NR-based positioning scheme (e.g. NRPPa). However, currently the legacy LPP is only applied for LTE and does not handle inter-RAT issue. Therefore, it may be necessary to consider how to support LPP protocol (e.g. exchange of LPP related messages error/abort handling) between LTE and NR. Furthermore, it may also be necessary to consider RAT-based positioning scheme selection.

Hereinafter, in order to solve the problem described above, the present invention proposes a method for selecting a RAT-based positioning scheme according to an embodiment of the present invention.

In the description below, it is assumed that a UE has capabilities for both LTE-based positioning scheme and NR-based positioning scheme. It is also assumed that a gNB or eLTE eNB (i.e. ng-eNB) is connected to the 5GC, and the gNB and eLTE eNB are interconnected with each other via Xn interface. Under this scenario, both UE and network can support either (or both) LTE-based positioning scheme and NR-based positioning scheme. Furthermore, among the various positioning methods described above, the present invention is focused on downlink/uplink positioning scheme via network (i.e. OTDOA, E-CID, UTDOA) where the UE performs measurement based on signals transmitted from gNB or eLTE eNB. Furthermore, in the description below, NR may be operated as stand-alone (SA) NR, which means that NR can be operated independently from LTE, or may be operated as non-stand-alone (NSA) NR, which means that NR should be operated with LTE. Furthermore, in the description below, LTE and NR may be configured with dual connectivity, e.g. EN-DC or NE-DC.

Meanwhile, NR introduces different physical structure (i.e. subcarrier spacing, number of subcarriers) compared to LTE. Therefore, NR-based positioning scheme may provide different PRS configuration compared to LTE-based positioning scheme, in perspective of bandwidth, mapping configuration or location, number of DL frames. In addition, since LTE and NR may use different frequency bands, its deployment (e.g. number of eNBs or gNBs) and actual coverage for supporting positioning scheme may be unequal.

According to an embodiment of the present invention, an indication may be attached to every LPP message to distinguish LPP message for LTE-based positioning scheme and NR-based positioning scheme. The indication may be 1-bit. For example, when a value of the indication is 0, the corresponding LPP message may be for LTE-based positioning scheme. When a value of the indication is 1, the corresponding LPP message may be for NR-based positioning scheme. With the indication, the network may configure different PRS upon the UE's request.

According to another embodiment of the present invention, the UE may select RAT-based positioning scheme (i.e. either LTE-based positioning scheme or NR-based positioning scheme) according to a condition of provided assistance data (e.g. NeighbourCellInfoList, E-CID measurement, associated). In addition, when the UE is using one positioning scheme, the UE may select other positioning scheme according to error condition of ongoing positioning scheme.

FIG. 14 shows an example of a method for selecting a RAT-based positioning scheme according to an embodiment of the present invention. The present invention described above may be applied to this embodiment.

In step S1400, the E-SMLC may send a request for the LPP related capabilities of the target UE. In step S1410, the UE transfers its LPP-related capabilities to the E-SMLC. The capabilities may refer to both LTE-based positioning scheme and NR-based positioning scheme.

In step S1420, the E-SMLC configures a RAT-based selection condition for using positioning scheme.

In step S1430, the UE may send a request to the E-SMLC for assistance data and may indicate the particular assistance data needed. In step S1440, the E-SMLC transfers assistance data to the UE. The transferred assistance data should match any assistance data requested.

The RAT-based selection condition may be used to select appropriate RAT-based positioning scheme for transmtting assistance data to the E-SMLC in step S1430. NR-based positioning scheme may be selected for transmitting assistance data in the following cases based on the RAT-based selection condition.

- The number of neighboring LTE cells (i.e. eNB) is not enough to perform LTE-based positioning;

- The UE cannot be aware of serving LTE cell's E-CID (or PCI).

On the other hand, LTE-based positioning scheme may be selected for transmitting assistance data in the following cases based on the RAT-based selection condition.

- There is no NR cell (i.e. gNB) in proximity;

- The number of neighboring NR cells is not enough to perform NR-based positioning

- The UE cannot be aware of serving NR cell's E-CID (or PCI).

In step S1450, the E-SMLC may send a request for location information to the target, and may indicate the type of location information needed. In step S1460, the UE (non-)periodically transfers positioning measurements or position estimate to the E-SMLC.

Furthermore, the RAT-based selection condition may be used to select appropriate RAT-based positioning scheme for measurement in downlink/uplink positioning scheme (i.e. OTDOA, E-CID, UTDOA). NR-based positioning scheme may be selected for measurement in the following cases based on the RAT-based selection condition.

- The measurement performance of LTE does not enough to calculate location estimation;

- The required quality of service (QoS) for LTE location estimation does not be satisfied.

On the other hand, LTE-based positioning scheme may be selected for measurement in the following cases based on the RAT-based selection condition.

- The measurement performance of NR does not enough to calculate location estimation;

- The required QoS for NR location estimation does not be satisfied.

Furthermore, while using one positioning scheme (i.e. either LTE-based positioning scheme or NR-based positioning scheme), the UE may switch the currently using positioning scheme. Specifically, the UE may switch positioning scheme when an error is detected during exchanging LPP messages or ongoing positioning procedure is aborted. In this case, the RAT-based selection condition may be used to select appropriate RAT-based positioning scheme for changing positioning scheme. The UE may switch positioning scheme from LTE-based positioning scheme to NR-based positioning scheme in the following cases based on the RAT-based selection condition.

- The error is detected during exchanging of LTE-based LPP message: The error may be detected upon detecting consecutive failure of N number of LPP message transmissions.

- On-going LTE-based positioning procedure is aborted.

The UE may switch positioning scheme from NR-based positioning scheme to LTE-based positioning scheme in the following cases based on the RAT-based selection condition.

- The error is detected during exchanging of NR-based LPP message: The error may be detected upon detecting consecutive failure of N number of LPP message transmissions.

- On-going NR-based positioning procedure is aborted.

FIG. 15 shows another example of a method for selecting a RAT-based positioning scheme according to an embodiment of the present invention. The present invention described above may be applied to this embodiment. In this embodiment, the UE has capabilities for both the first positioning scheme and the second positioning scheme. The network is an E-SMLC. The E-SMLC supports both the first positioning scheme and the second positioning scheme.

In step S1500, the UE receives information on the RAT-based selection condition for selecting either one of the first positioning scheme or the second positioning scheme from a network. In step S1510, the UE selects either one of the first positioning scheme or the second positioning scheme according to the RAT-based selection condition.

The selected positioning scheme may be the first positioning scheme, which is a LTE based positioning scheme. In this case, the RAT-based selection condition may be that there is no NR cells in proximity, or that a number of neighboring NR cells is not enough to perform NR-based positioning, or that the UE cannot be aware of an E-CID or a PCI of a serving NR cell. Alternatively, the selected positioning scheme is the second positioning scheme, which is a NR based positioning scheme. In this case, the RAT-based selection condition is that a number of neighboring LTE cells is not enough to perform NR-based positioning, or that that the UE cannot be aware of an E-CID or a PCI of a serving LTE cell.

In step S1520, the UE transmits a request for assistance data of the selected positioning scheme to the network. In step S1530, the UE receives the assistance data of the selected positioning scheme from the network. An indication for distinguishing a message for the first positioning scheme and a message for the second positioning scheme may be attached to the request for assistance data and the assistance data.

The UE may detect that an error occurs or an on-going positioning procedure is aborted, and switch a positioning scheme from the selected positioning scheme to other positioning scheme. That the error occurs may be detected due to consecutive failure of N number of LPP message transmissions.

A UE 1600 includes a processor 1610, a memory 1620 and a transceiver 1630. The processor 1610 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor 1610. The memory 1620 is operatively coupled with the processor 1610 and stores a variety of information to operate the processor 1610. The transceiver 1630 is operatively coupled with the processor 1610, and transmits and/or receives a radio signal.

A network node 1700 includes a processor 1710, a memory 1720 and a transceiver 1730. The processor 1710 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor 1710. The memory 1720 is operatively coupled with the processor 1710 and stores a variety of information to operate the processor 1710. The transceiver 1730 is operatively coupled with the processor 1710, and transmits and/or receives a radio signal.

The

processors

1610, 1710 may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The

memories

1620, 1720 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. The

transceivers

1630, 1730 may include baseband circuitry to process radio frequency signals. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in

memories

1620, 1720 and executed by

processors

1610, 1710. The

memories

1620, 1720 can be implemented within the

processors

1610, 1710 or external to the

processors

1610, 1710 in which case those can be communicatively coupled to the

processors

1610, 1710 via various means as is known in the art.

In view of the exemplary systems described herein, methodologies that may be implemented in accordance with the disclosed subject matter have been described with reference to several flow diagrams. While for purposed of simplicity, the methodologies are shown and described as a series of steps or blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the order of the steps or blocks, as some steps may occur in different orders or concurrently with other steps from what is depicted and described herein. Moreover, one skilled in the art would understand that the steps illustrated in the flow diagram are not exclusive and other steps may be included or one or more of the steps in the example flow diagram may be deleted without affecting the scope of the present disclosure.

Claims

A method for selecting a radio access technology (RAT) based positioning scheme by a user equipment (UE) in a wireless communication system, the method comprising:

receiving, by the UE, information on a RAT-based selection condition for selecting either one of a first positioning scheme or a second positioning scheme from a network;

selecting, by the UE, either one of the first positioning scheme or the second positioning scheme according to the RAT-based selection condition;

transmitting, by the UE, a request for assistance data of the selected positioning scheme to the network; and

receiving, by the UE, the assistance data of the selected positioning scheme from the network.
The method of claim 1, wherein an indication for distinguishing a message for the first positioning scheme and a message for the second positioning scheme is attached to the request for assistance data and the assistance data.
The method of claim 1, wherein the selected positioning scheme is the first positioning scheme, which is a long-term evolution (LTE) based positioning scheme.
The method of claim 3, wherein the RAT-based selection condition is that there is no NR cells in proximity.
The method of claim 3, wherein the RAT-based selection condition is that a number of neighboring NR cells is not enough to perform NR-based positioning.
The method of claim 3, wherein the RAT-based selection condition is that the UE cannot be aware of an enhanced cell ID (E-CID) or a physical cell ID (PCI) of a serving NR cell.
The method of claim 1, wherein the selected positioning scheme is the second positioning scheme, which is a new radio access technology (NR) based positioning scheme.
The method of claim 7, wherein the RAT-based selection condition is that a number of neighboring LTE cells is not enough to perform NR-based positioning.
The method of claim 7, wherein the RAT-based selection condition is that the UE cannot be aware of an E-CID or a PCI of a serving LTE cell.
The method of claim 1, further comprising:

detecting, by the UE, that an error occurs or an on-going positioning procedure is aborted; and

switching a positioning scheme from the selected positioning scheme to other positioning scheme.
The method of claim 10, wherein that the error occurs is detected due to consecutive failure of N number of LTE positioning protocol (LPP) message transmissions.
The method of claim 1, wherein the UE has capabilities for both the first positioning scheme and the second positioning scheme.
The method of claim 1, wherein the network is an evolved serving mobile location center (E-SMLC).
The method of claim 13, wherein the E-SMLC supports both the first positioning scheme and the second positioning scheme.
A user equipment (UE) in a wireless communication system, the UE comprising:

a memory;

a transceiver; and

a processor, operably coupled to the memory and the transceiver, that:

controls the transceiver to receive information on a radio access technology (RAT) based selection condition for selecting either one of a first positioning scheme or a second positioning scheme from a network;

selects either one of the first positioning scheme or the second positioning scheme according to the RAT-based selection condition;

controls the transceiver to transmit a request for assistance data of the selected positioning scheme to the network; and

controls the transceiver to receive the assistance data of the selected positioning scheme from the network.