CN113424610B

CN113424610B - Enhanced positioning method, device and computer readable medium based on OTDOA

Info

Publication number: CN113424610B
Application number: CN201980091730.8A
Authority: CN
Inventors: 刘建国; 陶涛; 孟艳; 沈钢
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2019-02-11
Filing date: 2019-02-11
Publication date: 2023-09-22
Anticipated expiration: 2039-02-11
Also published as: WO2020163983A1; CN113424610A

Abstract

Embodiments of the present disclosure relate to enhanced positioning mechanisms based on observed time difference of arrival (OTDOA). A method of object management, comprising: in response to receiving a location request for locating a terminal device from a location client at a location server, obtaining a location requirement associated with the terminal device from the location request; determining a positioning measurement configuration based at least in part on the positioning requirements, the positioning measurement configuration indicating a set of target cells for positioning the terminal device; and transmitting the positioning measurement configuration to the terminal device to enable the terminal device to perform positioning measurements based on the positioning measurement configuration. In this way, the solution can provide the target UE with the desired positioning performance while reducing power consumption, since the number of cells required for Reference Signal Time Difference (RSTD) measurements will be greatly reduced.

Description

Enhanced positioning method, device and computer readable medium based on OTDOA

Technical Field

Embodiments of the present disclosure relate generally to the field of telecommunications, and in particular, to an enhanced positioning mechanism based on observed time difference of arrival (OTDOA).

Background

Recently, research projects concerning NR localization were approved for Rel-16 NR. In LTE and Rel-15 NR, the main positioning techniques include observed time difference of arrival (OTDOA), enhanced cell ID (E-CID), and uplink time difference of arrival (UTDOA). In Rel-16 NR, it is expected that OTDOA techniques will be further enhanced.

OTDOA is a downlink positioning technique in which a target UE measures TOA (time of arrival) of Positioning Reference Signals (PRS) transmitted from a reference cell and a neighboring cell and reports a Reference Signal Time Difference (RSTD), which is used to determine the location of the target UE. To support OTDOA, higher layer signaling, i.e. the transfer of OTDOA assistance data and the transfer of RSTD measurements between the UE and the location server, e.g. an evolved serving mobile location center (E-SMLC) or a Service Location Protocol (SLP). Here, a ProvideAssistanceData (provide assistance data) message body in the LPP message is used by the location server to provide assistance data to the UE. The IE OTDOA-referenceCellInfo (OTDOA reference cell information) and IE OTDOA-neighbor cell InfoList (OTDOA neighbor cell information list) are used by the location server to provide the assistance data information of the reference cell and neighbor cells, respectively, for OTDOA assistance data. For target UEs it would be critical to provide not only high accuracy positioning but also low measurement complexity to preserve battery life.

Disclosure of Invention

In general, example embodiments of the present disclosure provide a solution for an enhanced positioning mechanism based on OTDOA.

In a first aspect, a method for an enhanced positioning mechanism based on OTDOA is provided. The method comprises the following steps: in response to receiving a location request from a location server for locating a terminal device from a location client, obtaining a location requirement associated with the terminal device from the location request; determining a positioning measurement configuration based at least in part on the positioning requirements, the positioning measurement configuration indicating a set of target cells for positioning the terminal device; and transmitting the positioning measurement configuration to the terminal device to enable the terminal device to perform positioning measurements based on the positioning measurement configuration.

In a second aspect, a method for an enhanced positioning mechanism based on OTDOA is provided. The method comprises the following steps: receiving, at the terminal device, a positioning measurement configuration from a location server, the positioning measurement configuration being determined and indicative of a set of target cells for positioning the terminal device based at least in part on positioning requirements associated with the terminal device, the positioning requirements being obtained from a location request sent from a location client to the location server; performing positioning measurements based on the positioning measurement configuration; and determining a positioning measurement report based on the results of the positioning measurements.

In a third aspect, an apparatus for an enhanced positioning mechanism based on OTDOA is provided. The apparatus includes at least one processor; and at least one memory including memory for computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: receiving a location request from a location client for locating a terminal device at a location server, obtaining a location requirement associated with the terminal device from the location request; determining a positioning measurement configuration based at least in part on the positioning requirements, the positioning measurement configuration indicating a set of target cells for positioning the terminal device; and transmitting the positioning measurement configuration to the terminal device to enable the terminal device to perform positioning measurements based on the positioning measurement configuration.

In a fourth aspect, an apparatus for an enhanced positioning mechanism based on OTDOA is provided. The apparatus includes at least one processor; and at least one memory including memory for computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to receive a positioning measurement configuration from a location server at the terminal device, the positioning measurement configuration being determined based at least in part on positioning requirements associated with the terminal device and indicating a set of target cells for positioning the terminal device, the positioning requirements being obtained from a location request sent from a location client to the location server; performing positioning measurements based on the positioning measurement configuration; and determining a positioning measurement report based on the results of the positioning measurements.

In a fifth aspect, there is provided an apparatus comprising means for performing the steps of the method according to the first aspect. The device comprises: means for obtaining a positioning requirement associated with a positioning terminal device from a location request for the terminal device in response to receiving the location request at a location server from a location client; means for determining a positioning measurement configuration based at least in part on the positioning requirements, the positioning measurement configuration indicating a set of target cells for positioning the terminal device; and means for transmitting the positioning measurement configuration to the terminal device to enable the terminal device to perform positioning measurements based on the positioning measurement configuration.

In a sixth aspect, there is provided an apparatus comprising means for performing the steps of the method according to the second aspect. The device comprises: means for receiving, at the terminal device, a positioning measurement configuration from a location server, the positioning measurement configuration determined based at least in part on positioning requirements associated with the terminal device and indicating a set of target cells for positioning the terminal device, the positioning requirements being obtained from a location request sent from a location client to the location server; means for performing positioning measurements based on the positioning measurement configuration; and means for determining a positioning measurement report based on the results of the positioning measurements.

In a seventh aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform the method according to the first aspect.

In an eighth aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform a method according to the second aspect.

It should be understood that the summary is not intended to identify key or essential features of the embodiments of the disclosure, nor is it intended to be used to limit the scope of the disclosure. Other features of the present disclosure will become apparent from the following description.

Drawings

Some example embodiments will now be described with reference to the accompanying drawings, in which:

FIG. 1 illustrates an example communication environment 100 in which example embodiments of the present disclosure may be implemented;

fig. 2 illustrates a schematic diagram of an example process 200 for discontinuous reception by a terminal device according to some example embodiments of the present disclosure;

FIG. 3 illustrates a flowchart of an example method 300 for an enhanced positioning mechanism, according to some example embodiments of the present disclosure;

FIG. 4 illustrates a flowchart of an example method 400 for an enhanced positioning mechanism, according to some example embodiments of the present disclosure;

FIG. 5 is a simplified block diagram of an apparatus suitable for implementing example embodiments of the present disclosure; and

fig. 6 illustrates a block diagram of an example computer-readable medium, according to some embodiments of the disclosure.

Throughout the drawings, the same or similar reference numerals refer to the same or similar elements.

Detailed Description

Principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described for illustrative purposes only and to assist those skilled in the art in understanding and practicing the present disclosure without suggesting any limitation to the scope of the present disclosure. The disclosure described herein may be implemented in various ways other than those described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard or protocol, such as Long Term Evolution (LTE), LTE-advanced (LTE-a), and 5G NR, and employs any suitable communication technology, including, for example, multiple Input Multiple Output (MIMO), OFDM, time Division Multiplexing (TDM), frequency Division Multiplexing (FDM), code Division Multiplexing (CDM), bluetooth, zigBee, machine Type Communication (MTC)), eMBB, mctc, and wrlc technologies. For discussion purposes, in some embodiments, an LTE network, an LTE-a network, a 5G NR network, or any combination thereof is taken as an example of a communication network.

As used herein, the term "network device" refers to any suitable device on the network side of a communication network. The network devices may include any suitable devices in an access network of a communication network, including, for example, base Stations (BSs), relays, access Points (APs), node BS (nodebs or NB), evolved nodebs (enodebs or enbs), 5G or next generation nodebs (gnbs), remote radio modules (RRUs), radio Heads (RH), remote Radio Heads (RRHs), low power nodes (such as femtos, piconets), and so forth. For discussion purposes, in some embodiments, an eNB is taken as an example of a network device.

The network devices may also include any suitable devices in the core network, including for example multi-standard radio (MSR) radio devices such as MSR BS, network controllers (BSC) such as Radio Network Controllers (RNC) or base station controllers, multi-cell/Multicast Coordination Entities (MCEs), mobile Switching Centers (MSC) and MMEs, operations and management (O & M) nodes, operations Support System (OSS) nodes, self-organizing network (SON) nodes, positioning nodes such as enhanced services mobile positioning centers (E-SMLC), and/or Mobile Data Terminals (MDT).

As used herein, the term "terminal device" refers to a device that is capable of, configured for, arranged for and/or operable to communicate with a network device or another terminal device in a communication network. The communication may involve the transmission and/or reception of wireless signals using electromagnetic signals, radio waves, infrared signals, and/or other types of signals suitable for conveying information over the air. In some embodiments, the terminal device may be configured to send and/or receive information without direct human interaction. For example, the terminal device may send information to the network device on a predetermined schedule when triggered by an internal or external event, or in response to a request from the network side.

Examples of terminal devices include, but are not limited to, user Equipment (UE) such as smartphones, wireless-enabled tablets, laptop embedded devices (LEEs), laptop installed devices (LMEs), and/or wireless Customer Premise Equipment (CPE). For purposes of discussion, some embodiments will be described hereinafter with reference to a UE as an example of a terminal device, and the terms "terminal device" and "user equipment" (UE) may be used interchangeably in the context of the present disclosure.

As used herein, the term "location server" may refer to a service function that provides the location of a target UE to a location client. The location server may communicate with the target UE via higher layer signaling to obtain the location measurement report from the target UE. The location service may also communicate with the network device to obtain information associated with the location of the target UE. The location server may be a component independent of the network device. Alternatively, the location server may be any functional module or functional entity embedded in the network device.

Corresponding to the term "location server", as used herein, the term "location client" may refer to an application or entity requesting the location of the target UE. The location client may send a location request to a location service and receive the location of the target UE from the location server. Furthermore, the location client may be considered as the target UE itself.

As used herein, the term "cell" refers to the area covered by radio signals transmitted by a network device. Terminal devices within a cell may be served by a network device and access a communication network via the network device.

As used herein, the term "circuitry" may refer to one or more or all of the following:

(a) Pure hardware circuit implementations (such as implementations in analog and/or digital circuitry only) and

(b) A combination of hardware circuitry and software, such as (if applicable): (i) A combination of analog and/or digital hardware circuit(s) and software/firmware, and (ii) any portion of the hardware processor(s) with software, including digital signal processor(s), software, and memory(s), which work together to cause a device such as a mobile phone or server to perform various functions, and

(c) Software (e.g., firmware) is required to allow hardware circuit(s) and/or processor(s), such as microprocessor(s) or portion of microprocessor(s), but may not exist when it is not required for operation.

This definition of circuitry applies to all uses of this term in this application, including all uses in any claims. As a further example, as used in this disclosure, the term circuitry also encompasses hardware-only circuitry or processor (or processors) or a portion of hardware circuitry or processor and its (or their) implementation in conjunction with software and/or firmware. For example and where applicable to the elements of the specific claims, the term circuitry also encompasses a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "comprising" and its variants are to be interpreted as "based at least in part on". The terms "one embodiment" and "an embodiment" should be read as "at least one embodiment. The term "another embodiment" should be read as "at least one other embodiment". Other definitions, whether explicit or implicit, may be included below.

Fig. 1 illustrates a communication environment 100 in which embodiments of the present disclosure may be implemented.

As shown in fig. 1, communication environment 100 may include a plurality of network devices 121, 122, and 123, and a UE 130.UE 130 may communicate with a plurality of network devices 121, 122, and 123. Cell 143 may be a serving cell 130 of the UE, which may be considered a reference cell for UE 130, while cells 141 and 142 may be considered neighbor cells. It should be appreciated that the reference cell may not be the serving cell for UE 130. For example, UE 130 is moving to the edge of the serving cell and the SNR of the reference signal associated with the other cell is better than the SNR of the reference signal associated with the serving cell, in which case the reference cell may be a cell other than the serving cell.

Location server 110 may communicate with UE 130 to obtain location measurement reports for UE 130. In general, location server 110 may periodically receive location measurement reports from UE 130. The location of UE 130 may be determined by means of observed time difference of arrival (OTDOA) techniques. As mentioned above, OTDOA is a downlink positioning technique in which a target UE measures TOA (time of arrival) of Positioning Reference Signals (PRS) transmitted from a reference cell and a neighboring cell and reports a Reference Signal Time Difference (RSTD), which is used to find the location of the target device.

Referring to fig. 1, a time difference 130 between an arrival time of a positioning reference signal from a reference cell 141 to a UE 130 and an arrival time of a positioning reference signal from neighboring cells 142 and 143 to the UE may be used to determine a location of the UE 130 based on a predetermined algorithm. To support OTDOA, higher layer signaling, i.e. the transfer of OTDOA assistance data and the transfer of RSTD measurements between the UE and the location server, e.g. an evolved serving mobile location center (E-SMLC) or a Service Location Protocol (SLP).

It would be critical for UE 130 to provide not only high accuracy positioning but also low measurement complexity to preserve battery life. Since UE 130 may perform positioning measurements (e.g., RSTD, SNR of TOA measurements, etc.) based on assistance data provided by the network and the resulting measurements based on Positioning Reference Signals (PRS) or other reference signals are used to position UE 130. Existing positioning measurement methods lead to high complexity problems for UE 130.

First, the location server may not have previously acquired SNR information for the location measurement of the neighbor cells to the target UE, and thus the location server may need to configure a sufficient number of neighbor cells in order to improve the location performance of the target UE. In LTE, a maximum of 24 neighboring cells belonging to the same or different frequency layers will be configured to the UE for positioning measurements in order to provide a reasonably accurate positioning performance.

Second, even though the location server may update the measurement list based on the location measurement report from the target UE, it may be difficult to guarantee location performance if the radio environment between the neighboring cell and the target UE changes within the update period. Thus, the location server may still maintain a sufficient number of neighboring cells to ensure the positioning performance of the target UE.

Although measuring multiple cells may achieve higher positioning accuracy, for some situations, partially configured neighboring cells may be sufficient to meet positioning accuracy requirements, such as E911 to make positioning measurements. However, the positioning requirements from the location client are transparent to the target UE, and thus the UE has to measure all configured neighbor cells, which would lead to an unnecessary increase in complexity burden and power consumption. To overcome these drawbacks, it is desirable for the UE itself to autonomously determine which cells it should measure based on assistance data configured by the location server, providing not only the required positioning performance but also low measurement complexity to preserve battery life.

The principles and implementations of the present disclosure will be described in detail below with reference to fig. 2, fig. 2 showing a process 200 according to an example embodiment of the present disclosure. For discussion purposes, process 200 will be described with reference to FIG. 1. Process 200 may involve an enhanced positioning mechanism based on OTDOA.

As shown in fig. 2, location client 201 may send 310 a location request to location server 110 for locating UE 130. In some embodiments, the location request may include a positioning requirement associated with UE 130. Positioning requirements may include, for example, positioning accuracy, response time, and service SNR for a location service. The positioning accuracy may depend on the type of UE to be positioned. For example, positioning accuracy for E911 is not expected to be very high.

Alternatively, if there is no positioning requirement in the location request, a default positioning accuracy may be specified by the location server 110 according to some rule.

If the location server 110 receives the location request and determines a positioning requirement, the location server 110 determines 315 a positioning measurement configuration. The positioning measurement configuration may indicate a set of target cells for positioning the UE. In other words, the positioning measurement configuration may be considered as a measurement rule for indicating a cell to be measured by the UE 130 for positioning the UE 130 in a predetermined scenario.

In some embodiments, location server 110 may require UE 130 to prioritize a particular number of neighbor cells in the measurement list that have TOA measurements with minimum effective SNR requirements related to PRS configuration.

In this case, the location server 110 may obtain the PRS configuration and SNR threshold for the TOA for the reference cell of the UE 130. For example, the SNR threshold may refer to the minimum effective signal-to-noise ratio (SNR) of the TOA configured for this PRS. For example, PRS configuration for a reference cell of UE 130 may be included in a previous positioning measurement report from UE 130, which may be periodically sent 305 from UE 130 to location server 110.

In some embodiments, the SNR threshold may be preconfigured based on a predetermined PRS configuration. The location server 110 may determine a first mapping between the number of target cells and the SNR of TOA measurements associated with a predetermined PRS configuration of a reference cell for the UE. Alternatively, the first mapping table may be obtained experimentally by using a reference positioning device having a known position.

Assuming a positioning scenario and PRS configuration for each cell, the location server may configure different cells to the reference positioning device for OTDOA based positioning measurements. Since the location information of the reference positioning device is known in advance, the location server can record the actual SNR of the TOA measurements from each cell and arrive at positioning accuracy based on the reports from the reference device, including, for example, RSTD and TOA from each cell and the corresponding SNR of the TOA measurement cell, etc. To achieve the desired positioning accuracy, the required SNR from the TOA of each cell may be achieved by adjusting the transmit power of the positioning gNB for a given number of cells for the positioning measurements.

That is, the location service 110 may determine the number of target cells based on the first mapping due to a PRS configuration for the reference cell of the UE 130 and a minimum effective signal-to-noise ratio (SNR) for the TOA of the PRS configuration. An example of a first mapping is shown in table 1 below, which may be used for outdoor scenes; PRS configuration with 5MHz bandwidth and 15KHz SCS and desired positioning accuracy of 1 m.

Table 1: example of the first mapping Table

SNR of TOA (dB)	Number of cells required
		20	2
10	3
		6	4
0	5
		-3	6

If the location server 110 can determine the number of target cells based on the first mapping, such as table 1, the location server 110 can determine the positioning measurement configuration based on the number of target cells and the SNR threshold of the TOA.

In some embodiments, the positioning measurement rules may require that the target UE preferentially measure a particular neighbor cell with TOA measurements of minimum effective SNR requirements related to PRS configuration of the reference cell.

In this case, location server 110 may obtain PRS configurations for the reference cell of UE 130 and a set of available cells of UE 130. The location server 110 may also obtain the SNR of the TOA associated with the reference cell and a set of available cells of the terminal device.

Based on the PRS configuration for the reference cell and the set of available cells, and the SNR of the TOAs associated with the reference cell and the set of available cells, the location server 110 may determine an SNR threshold, such as a minimum effective signal-to-noise ratio (SNR) of the TOAs for the PRS configuration.

For the case where the PRS configuration of the reference cell is equal to the PRS configuration of the available cells, the location server 110 may select a target cell having an SNR not less than a minimum effective SNR from a set of available cells based on positioning requirements and an SNR threshold and determine a positioning measurement configuration based on an identification of the selected target cell.

For the case where the PRS configuration of the reference cell is different from the PRS configurations of the available cells, the location server 110 may determine a second mapping indicating a relationship between the SNR of the TOA related to the PRS configuration of the reference cell and the SNR of the TOA related to the PRS configuration of each cell in the set of available cells.

The second mapping may be used to map the SNR of the TOA measurement from one PRS configuration to another PRS configuration in order to achieve the same TOA accuracy. This type of mapping table is mainly used in the case of different PRS configurations per cell.

In some embodiments, the effective SNR of the TOA measurement may be obtained by theoretical calculation methods. For example, suppose that PRS configurations for a reference cell and neighboring cells are considered for OTDOA positioning. Using PRSs of neighboring cells or PRSs of reference cells, the following estimate of the effective SNR of the PRSs of neighboring cells can be obtained to reach the same Cramer-Rao lower limit (CRLB) of TOA measurements. The second mapping may be expressed as the following equation:

Wherein N is _symb Is the total number of OFDM symbols with downlink reference signals and M is in the slotThe transmission duration of the individual OFDM symbols; SNR of _rc-PRS Is the SNR of the TOA measurement of the reference cell PRS.

In some embodiments, the effective SNR of the TOA measurement may be obtained experimentally. For example, the location server may train the reference device to measure TOA and corresponding SNR for different PRS configurations in an actual positioning scenario. Based on the measurement information, a second mapping may be performed to map the SNR required for TOA measurements for one PRS configuration to another PRS configuration with the same TOA accuracy.

In some embodiments, the location server 110 may determine the location measurement configuration based on the first mapping. In some embodiments, the location server 110 may determine the positioning measurement configuration based on the first mapping and the second mapping. The first and second mappings herein may be considered as a positioning measurement configuration.

If a location measurement configuration is determined, the location server may send 320 the location measurement configuration to UE 130.

In some embodiments, the positioning measurement configuration may be sent to UE 130 with positioning assistance data via a "provideasistancedata" message based on the LTE Positioning Protocol (LPP) protocol.

Based on the location measurement configuration, UE 130 performs 325 location measurements of cells associated with the location of UE 130. The cells associated with positioning may be indicated in a positioning measurement configuration or may be determined by UE 130 based on the positioning measurement configuration.

Since the SNR of the TOA measurement from the reference cell is critical to the positioning accuracy, UE 130 may perform the TOA measurement from the reference cell and fall back to the general positioning measurement if the SNR of the TOA measurement from the reference cell is below the required effective SNR indicated in the positioning measurement report. That is, UE 130 may seek to measure other neighboring cells in the measurement list such that the location server may use measurements from more neighboring cells to improve positioning accuracy or/and update assistance data to UE 130 based on reports of the measurements.

In some embodiments, if the positioning measurement configuration indicates a particular number of target cells, UE 130 may select a corresponding number of target cells from the measurement list based on a predetermined measurement order of the measurement list and perform positioning measurements for each target cell in the set of target cells.

If the SNR of the TOA of each target cell in the set of target cells is not less than the threshold TOA, the UE 130 may determine at least one of the TOA, the SNR of the TOA, and a Reference Signal Time Difference (RSTD) of each target cell in the set of target cells as a measurement result.

In some embodiments, the order of measurement may be the same as that provided by the location server in the measurement list.

In some embodiments, UE 130 may determine the measurement order from the SNR of the TOA measurements based on previous results of the TOA measurements. The measurement order may be the same as the order provided by the location server in the measurement list if no TOA measurements have been made before.

In particular, UE 130 may initialize the number of available neighbor cells for positioning measurements to zero. If the measured PRS configuration of the neighbor cell is different from the PRS configuration of the reference cell, the UE 130 may map the TOA measured SNR to the TOA measured effective SNR for the PRS configuration of the reference cell. Otherwise, the effective SNR of the TOA measurement is set to the actual SNR of the TOA measurement from the neighboring cell.

If the effective SNR measured by the TOA is greater than the required effective SNR, then the cell will be considered one of the available cells. Otherwise, if the number of available cells is greater than the specific number of target cells provided by the network, it means that UE 130 may stop positioning measurements from other neighboring cells. Otherwise, UE 130 may continue to measure other neighboring cells until a certain number is met.

In some embodiments, if the positioning measurement configuration indicates an identity of a target cell, UE 130 may select a set of target cells from a set of available cells of UE 130 based on the identity of the target cell and perform positioning measurements for each target cell in the set of target cells. If the SNR of the TOA of each target cell in the set of target cells is not less than the SNR threshold of the TOA, at least one of the TOA, the SNR of the TOA, and a Reference Signal Time Difference (RSTD) of each target cell in the set of target cells is determined as a measurement result.

Specifically, UE 130 may measure SNR, RSTD of TOA measurements from a particular cell indicated in the positioning measurement configuration. If the PRS configuration for the measured cell is different from the PRS configuration for the reference cell, the UE 130 may map the TOA measured SNR to the TOA measured effective SNR of the PRS configuration for the reference cell. Otherwise, the effective SNR of the TOA measurement is set to the actual SNR of the TOA measurement from the particular cell. If the effective SNR of TOA measurements from any particular cell is lower than the required effective SNR, UE 130 may fall back to the general positioning measurements and measure other neighbor cells in the measurement list. Otherwise, UE 130 may cease positioning measurements from other neighboring cells.

In some embodiments, if the positioning measurement configuration indicates a first mapping between the number of target cells for the plurality of predetermined PRS configurations and an SNR threshold for the TOA and a second mapping between an SNR for the TOA related to a PRS configuration for a reference cell of the UE130 and an SNR for the TOA related to a PRS configuration for each target cell of the set of target cells, the UE130 may perform positioning measurements on the set of available cells of the UE130 and select the set of target cells from the set of available cells based on the first and second mappings and the measurement results for each cell of the set of available cells.

Specifically, UE130 may measure TOA measured SNR, RSTD from a set of available cells in a measurement list with a given measurement order. The UE may initialize the number of measured available cells to zero. If the PRS configuration of the measured cell is different from the PRS configuration of the reference cell, the UE130 may map the TOA measured SNR to the TOA measured effective SNR for the PRS configuration of the reference cell. Otherwise, the effective SNR of the TOA measurement is set to the actual SNR of the TOA measurement from the available cells. After each measurement, the number of available cells that have been measured is increased by one.

UE130 may check whether any combination of TOA measurements from the measured available cells meets the positioning requirements by looking up the first mapping.

After completing the TOA measurements from one available cell, UE130 may look up a first mapping of TOA measurements with the smallest effective SNR from any combination of other measured available cells and the last measured available cell to estimate the number of available cells needed for the desired positioning accuracy. If the number of available cells required is not greater than the number of measured available cells in the combination. Combinations of measured available cells will be available.

If there are available combinations of measured available cells that meet the positioning requirements, then UE130 stops positioning measurements from other available cells. Otherwise, UE130 may continue to measure other neighboring cells until a particular number of target cells is met.

In some embodiments, UE130 may update the location measurement report based on the results of the location measurement and send 330 the updated location report to location server 110.

In some embodiments, in order to reduce signaling overhead for location information reporting, one embodiment is elaborated for enhanced location reporting. For example, UE130 may report the available measurements to the location server only in the same order as provided by the location server, and the bitmap is designed to indicate available neighbor cells in the measurement list that have been measured for positioning measurements (e.g., SNR of ToA measurements, RSTD).

In this way, low complexity positioning measurements are allowed for the target UE based on the configuration of the positioning measurement rules provided by the location server, which may reduce the positioning measurement complexity and power consumption of the target UE and reduce the signaling overhead of the UE for location reporting with the enhanced positioning measurement reporting mechanism.

Further details of example embodiments according to the present disclosure will be described with reference to fig. 3-4.

Fig. 3 illustrates a flowchart of an example method 300 for an OTDOA-based enhanced positioning mechanism, according to some example embodiments of the present disclosure. The method 300 may be implemented at a location server 110 as shown in fig. 1. For discussion purposes, the method 300 will be described with reference to FIG. 1.

At 310, if the location server 110 receives a location request from a location client for locating a terminal device, the location server 110 obtains a location requirement associated with the terminal device from the location request.

In some embodiments, location server 110 may obtain at least one of: response time and distance accuracy for location requests.

At 320, the location server 110 determines a location measurement configuration indicating a set of target cells for locating the terminal device based at least in part on the location requirement.

In some embodiments, the location server 110 may obtain a signal-to-noise ratio (SNR) threshold and a Positioning Reference Signal (PRS) configuration for a time of arrival (TOA) of a reference cell of the terminal device, the reference cell being different from a set of target cells; determining a number of target cells based on SNR thresholds and positioning requirements of TOAs related to PRS configurations of reference cells of the target device; and determining a positioning measurement configuration based on the number of target cells and a signal to noise ratio threshold of the TOA.

In some embodiments, the location server 110 may obtain a signal-to-noise ratio (SNR) of a time of arrival (TOA) associated with a reference cell of the terminal device and a set of available cells, the reference cell being different from the set of target cells; acquiring Positioning Reference Signal (PRS) configuration of a reference cell and a group of available cells of a terminal device; determining an SNR threshold of TOAs related to PRS configuration of a reference cell of a target device based on SNR of TOAs associated with the reference cell and a set of available cells of the terminal device and PRS configuration of the reference cell and the set of available cells of the terminal device; selecting a target cell from a set of available cells based on SNR thresholds and positioning requirements of TOAs related to PRS configuration of reference cells of the target device; and determining a positioning measurement configuration based on the identity of the target cell and the SNR threshold of the TOA.

In some embodiments, the location server 110 may determine a first mapping between the number of target cells and SNR thresholds for time of arrival (TOA) of a plurality of predetermined Positioning Reference Signal (PRS) configurations for positioning accuracy and determine a positioning measurement configuration based on the first mapping.

In some embodiments, the location server 110 may determine a second mapping between the SNR of the TOA related to a Positioning Reference Signal (PRS) configuration of a reference cell of the terminal device and the SNR of the TOA related to a PRS configuration of each target cell of the set of target cells and determine a positioning measurement configuration based on the second mapping.

At 330, the location server 110 sends the location measurement configuration to the terminal device to enable the terminal device to perform location measurements based on the location measurement configuration.

In some embodiments, the location server 110 may also receive from the terminal device a location measurement report generated by the terminal device based on the location measurement configuration and determine the location of the terminal device based on the location measurement report. Location server 110 may provide the determined location of the terminal device to the location client.

Fig. 4 illustrates a flowchart of an example method 400 for an OTDOA-based enhanced positioning mechanism, according to some example embodiments of the present disclosure. Method 400 may be implemented at UE 130 as shown in fig. 1. For discussion purposes, the method 400 will be described with reference to FIG. 1.

At 410, UE 130 receives a location measurement configuration from a location server at the terminal device, the location measurement configuration determined based at least in part on a location requirement associated with the terminal device and indicating a set of target cells for locating the terminal device, the location requirement obtained from a location request sent from a location client to the location server.

At 420, UE 130 performs positioning measurements based on the positioning measurement configuration.

In some embodiments, UE 130 may obtain a number of target cells and a signal-to-noise ratio (SNR) threshold for a time of arrival (TOA) from a positioning measurement configuration and select a set of target cells from a set of available cells of the terminal device based on the number of target cells and a predetermined measurement order for the set of available cells. UE 130 may also perform positioning measurements for each target cell in a set of target cells. If the SNR of the time of arrival (TOA) of each target cell in the set of target cells is not less than the SNR threshold of the TOA, UE 130 may determine the TOA, the SNR of the TOA, and a Reference Signal Time Difference (RSTD) of each target cell in the set of target cells as measurement results.

In some embodiments, UE 130 may obtain an identification of the target cell and a signal-to-noise ratio (SNR) threshold for a time of arrival (TOA) from the positioning measurement configuration and select a set of target cells from a set of available cells of the terminal device based on the identification of the target cells. UE 130 may also perform positioning measurements for each target cell in a set of target cells. If the SNR of the time of arrival (TOA) of each target cell in the set of target cells is not less than the SNR threshold of the TOA, UE 130 may determine the TOA, the SNR of the TOA, and a Reference Signal Time Difference (RSTD) of each target cell in the set of target cells as measurement results.

In some embodiments, UE 130 may obtain a first mapping between a number of target cells and a SNR threshold for a time of arrival (TOA) of a plurality of predetermined Positioning Reference Signal (PRS) configurations from a positioning measurement configuration and a second mapping between a SNR of a TOA related to a Positioning Reference Signal (PRS) configuration of a reference cell of a terminal device and a SNR of a TOA related to a PRS configuration of each target cell in a set of target cells and perform a positioning measurement on a set of available cells of the terminal device. UE 130 may select a set of target cells from a set of available cells based on the first and second mappings for each cell in the set of available cells and determine at least one of a TOA, an SNR of the TOA, and a Reference Signal Time Difference (RSTD) for each target cell in the set of target cells as a measurement.

At 430, UE 130 determines a location measurement report based on the measurement results of the location measurement.

In some embodiments, UE 130 may also generate a location measurement report for the terminal device, the location measurement report indicating at least one of: reference Signal Time Difference (RSTD) of a set of available cells of the terminal device, time of arrival (TOA) of the set of available cells of the terminal device, and SNR of time of arrival (TOA) associated with the set of available cells of the terminal device; and sends a location measurement report to the location server.

In some embodiments, UE 130 may obtain a location measurement report for the terminal device and generate a result of the location measurement based on the location measurement.

In some example embodiments, an apparatus (e.g., implemented at location server 110) capable of performing method 300 may include means for performing the various steps of method 300. The component may be implemented in any suitable form. For example, the components may be implemented in a circuit or software module.

In some example embodiments, the apparatus includes: means for obtaining, in response to receiving a location request for a positioning terminal device from a location client at a location server, a positioning requirement associated with the terminal device from the location request; means for determining a positioning measurement configuration based at least in part on the positioning requirements, the positioning measurement configuration indicating a set of target cells for positioning the terminal device; and means for transmitting the positioning measurement configuration to the terminal device to enable the terminal device to perform positioning measurements based on the positioning measurement configuration.

In some example embodiments, an apparatus (e.g., implemented at UE 130) capable of performing method 400 may include means for performing the various steps of method 400. The component may be implemented in any suitable form. For example, the components may be implemented in a circuit or software module.

In some example embodiments, the apparatus includes: means for receiving, at the terminal device, a positioning measurement configuration from a location server, the positioning measurement configuration determined based at least in part on positioning requirements associated with the terminal device and indicating a set of target cells for which the terminal device is located, the positioning requirements being obtained from a location request sent from a location client to the location server; means for performing positioning measurements based on the positioning measurement configuration; and means for determining a positioning measurement report based on the result of the positioning measurement.

Fig. 5 is a simplified block diagram of an apparatus 500 suitable for implementing embodiments of the present disclosure. Device 500 may be provided to implement location server 110 and UE 130 as shown in fig. 1. As shown, device 500 includes one or more processors 510, one or more memories 520 coupled to processor 510, and one or more transmitters and/or receivers (TX/RX) 540 coupled to processor 510.

TX/RX 540 is used for two-way communication. TX/RX 540 has at least one antenna to facilitate communication. The communication interface may represent any interface required to communicate with other network elements.

Processor 510 may be of any type suitable for use in a local technology network and may include, by way of non-limiting example, one or more of a general purpose computer, a special purpose computer, a microprocessor, a Digital Signal Processor (DSP), and a processor based on a multi-core processor architecture. The device 500 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock that is synchronized to the master processor.

Memory 520 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, read-only memory (ROM) 524, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact Disks (CD), digital Video Disks (DVD), and other magnetic and/or optical storage. Examples of volatile memory include, but are not limited to, random Access Memory (RAM) 522 and other volatile memory that will not last for the duration of the power outage.

The computer program 530 includes computer-executable instructions that are executed by an associated processor 510. Program 530 may be stored in ROM 524. Processor 510 may perform any suitable actions and processes by loading program 530 into RAM 522.

Embodiments of the present disclosure may be implemented by means of program 530 such that device 500 may perform any of the processes of the present disclosure discussed with reference to fig. 2-4. Embodiments of the present disclosure may also be implemented in hardware or a combination of hardware and software.

In some embodiments, program 530 may be tangibly embodied in a computer-readable medium that may be included in device 500 (such as in memory 520) or other storage device accessible to device 500. Device 500 may load program 530 from a computer readable medium into RAM 522 for execution. The computer readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig. 6 shows an example of a computer readable medium 600 in the form of a CD or DVD. The computer readable medium has a program 530 stored thereon.

In general, the various embodiments of the disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. For example, in some embodiments, various examples of the disclosure (e.g., methods, apparatus, or devices) may be partially or fully implemented on a computer-readable medium. While various aspects of the embodiments of the disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The elements included in the apparatus and/or devices of the present disclosure may be implemented in various ways, including software, hardware, firmware, or any combination thereof. In one embodiment, one or more of the units may be implemented using software and/or firmware, such as machine executable instructions stored on a storage medium. Some or all of the elements in an apparatus and/or device may be implemented at least in part by one or more hardware logic components in addition to or in place of machine-executable instructions. For example, but not limited to, illustrative types of hardware logic components that may be used include Field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), application Specific Standard Products (ASSPs), system-on-Chip Systems (SOCs), complex Programmable Logic Devices (CPLDs), and the like.

By way of example, embodiments of the present disclosure may be described in the context of computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions for program modules may be executed within a local device or within a distributed device. In distributed devices, program modules may be located in both local and remote memory storage media.

Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus such that the program code, when executed by the processor or controller, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this disclosure, a computer-readable 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. The computer readable medium may be a machine readable signal medium or a machine readable storage medium. The computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of machine-readable storage media would include: 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), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Moreover, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some scenarios, multitasking and parallel processing may be advantageous. Also, while the above discussion contains several specific embodiment details, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Although the disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A method, comprising:

in response to receiving a location request for locating a terminal device from a location client at a location server, obtaining a location requirement associated with the terminal device from the location request;

determining a positioning measurement configuration based at least in part on the positioning requirements, the positioning measurement configuration indicating a set of target cells for positioning the terminal device, whereby the set of target cells is determined based on the positioning requirements; and

transmitting the location measurement configuration to the terminal device to enable the terminal device to perform location measurements based on the location measurement configuration,

wherein determining the positioning measurement configuration comprises:

obtaining a signal-to-noise ratio (SNR) threshold and a Positioning Reference Signal (PRS) configuration for a time of arrival (TOA) of a reference cell of the terminal device, the reference cell being different from the set of target cells;

Determining a number of the target cells based on the SNR threshold of the TOA and the positioning requirements related to the PRS configuration of the reference cell of the terminal device; and

the positioning measurement configuration is determined based on the number of the target cells and the SNR threshold of the TOA.

2. The method of claim 1, wherein obtaining the positioning requirements comprises obtaining at least one of:

positioning accuracy, and

response time for the location request.

3. The method of claim 1, further comprising:

receiving from the terminal device a positioning measurement report generated by the terminal device based on the positioning measurement configuration;

determining a location of the terminal device based on the positioning measurement report; and

providing the determined location of the terminal device to the location client.

4. A method, comprising:

wherein determining the positioning measurement configuration comprises:

obtaining, from the terminal device, a signal-to-noise ratio (SNR) of a time of arrival (TOA) associated with a reference cell of the terminal device and a set of available cells, the reference cell being different from the set of target cells;

acquiring Positioning Reference Signal (PRS) configurations for the reference cell and the set of available cells of the terminal device;

determining an SNR threshold for a TOA associated with the PRS configuration for the reference cell and a set of available cells of the terminal device based on the SNR for the TOA associated with the reference cell and the PRS configuration for the set of available cells of the terminal device;

selecting the target cell from the set of available cells based on the SNR threshold and the positioning requirements of the TOA related to the PRS configuration for the reference cell of the terminal device; and

the positioning measurement configuration is determined based on the identity of the target cell and the SNR threshold of TOA.

5. A method, comprising:

wherein determining the positioning measurement configuration comprises:

determining a first mapping between the number of target cells and a signal-to-noise ratio (SNR) threshold of a time of arrival (TOA) of a plurality of predetermined Positioning Reference Signal (PRS) configurations for the positioning requirement; and

the positioning measurement configuration is determined based on the first mapping for the positioning requirements.

6. A method, comprising:

wherein determining the positioning measurement configuration comprises:

determining a second mapping between a SNR of a time of arrival (TOA) associated with a Positioning Reference Signal (PRS) configuration for a reference cell of the terminal device and a SNR of the TOA associated with a PRS configuration for each target cell of a set of target cells; and

the positioning measurement configuration is determined based on the second mapping.

7. A method, comprising:

receiving, at a terminal device, a positioning measurement configuration from a location server, the positioning measurement configuration being determined based at least in part on positioning requirements associated with the terminal device and indicating a set of target cells for positioning the terminal device, whereby the set of target cells is determined based on the positioning requirements, the positioning requirements being obtained from a location request sent from a location client to the location server;

Performing a positioning measurement based on the positioning measurement configuration; and

determining a positioning measurement report based on measurement results of the positioning measurements,

wherein performing the positioning measurement comprises:

obtaining a signal-to-noise ratio (SNR) threshold for a number and time of arrival (TOA) of the target cells from the positioning measurement configuration;

selecting a set of target cells from a set of available cells of the terminal device based on the number of target cells and a predetermined measurement order of the set of available cells;

performing the positioning measurement for each target cell in the set of target cells; and

at least one of the TOA of each target cell in the set of target cells, the SNR of the TOA, and a Reference Signal Time Difference (RSTD) is determined as the measurement responsive to the SNR of the TOA of each target cell in the set of target cells not being less than the SNR threshold of the TOA.

8. The method of claim 7, further comprising:

generating the location measurement report of the terminal device, the location measurement report indicating at least one of:

reference Signal Time Difference (RSTD) of a set of available cells of the terminal device, and

Time of arrival (TOA) of a set of available cells of the terminal device, and

SNR of TOA associated with a set of available cells of the terminal device; and

and sending the positioning measurement report to the position server.

9. A method, comprising:

wherein performing the positioning measurement comprises:

obtaining an identification of the target cell and a signal-to-noise ratio (SNR) threshold for a time of arrival (TOA) from the positioning measurement configuration;

selecting the set of target cells from a set of available cells of the terminal device based on the identification of the target cells;

10. A method, comprising:

wherein performing the positioning measurement comprises:

obtaining a first mapping between the number of target cells and a signal-to-noise ratio (SNR) threshold of a time of arrival (TOA) of a plurality of predetermined Positioning Reference Signal (PRS) configurations and a second mapping between an SNR of the TOA related to a PRS configuration for a reference cell of the terminal device and an SNR of the TOA related to a PRS configuration for each target cell in a set of target cells from the positioning measurement configuration;

Performing positioning measurements for a set of available cells of the terminal device;

selecting the set of target cells from the set of available cells based on the first and second mappings and the measurement results for each cell in the set of available cells; and

at least one of a TOA of each target cell in the set of target cells, the SNR of the TOA, and a Reference Signal Time Difference (RSTD) is determined as the measurement.

11. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to:

wherein the device is caused to determine the positioning measurement configuration by:

12. The apparatus of claim 11, wherein the apparatus is caused to obtain the positioning requirement by obtaining at least one of:

positioning accuracy, and

response time for the location request.

13. The apparatus of claim 11, wherein the apparatus is further caused to:

14. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

Obtaining from the terminal device a signal-to-noise ratio (SNR) of a time of arrival (TOA) associated with a reference cell and a set of available cells of the terminal device;

obtaining Positioning Reference Signal (PRS) configurations for the reference cell and the set of available cells of the terminal device, the reference cell being different from the set of target cells;

determining an SNR threshold for the TOA related to the PRS configuration for the reference cell of the terminal device based on the SNR for the TOA associated with the reference cell and a set of available cells of the terminal device and the PRS configuration for the reference cell and the set of available cells of the terminal device;

15. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

16. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

17. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

wherein the device is caused to perform the positioning measurement by:

18. The apparatus of claim 17, wherein the apparatus is further caused to:

generating a positioning measurement report of the terminal device, the positioning measurement report indicating at least one of:

time of arrival (TOA) of a set of available cells of the terminal device, and

SNR of TOA associated with a set of available cells of the terminal device; and

and sending the positioning measurement report to the position server.

19. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

wherein the device is caused to perform the positioning measurement by:

20. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

wherein the device is caused to perform the positioning measurement by:

21. An apparatus, comprising:

means for obtaining a positioning requirement associated with a positioning terminal device from a location request for the terminal device in response to receiving the location request at a location server from a location client;

means for determining a positioning measurement configuration based at least in part on the positioning requirements, the positioning measurement configuration indicating a set of target cells for positioning the terminal device, whereby the set of target cells is determined based on the positioning requirements; and

means for transmitting the location measurement configuration to the terminal device to enable the terminal device to perform location measurements based on the location measurement configuration,

wherein the means for determining the positioning measurement configuration comprises:

Means for obtaining a signal-to-noise ratio (SNR) threshold and a Positioning Reference Signal (PRS) configuration for a time of arrival (TOA) of a reference cell of the terminal device, the reference cell being different from the set of target cells;

means for determining a number of the target cells based on the SNR threshold of the TOA and the positioning requirements related to the PRS configuration of the reference cell of the terminal device; and

means for determining the positioning measurement configuration based on the number of target cells and the SNR threshold of the TOA.

22. An apparatus, comprising:

means for receiving, at a terminal device, a positioning measurement configuration from a location server, the positioning measurement configuration being determined based at least in part on positioning requirements associated with the terminal device and indicating a set of target cells for positioning the terminal device, whereby the set of target cells is determined based on the positioning requirements, the positioning requirements being obtained from a location request sent from a location client to the location server;

means for performing positioning measurements based on the positioning measurement configuration; and

Means for determining a positioning measurement report based on measurement results of the positioning measurements,

wherein the means for performing the positioning measurement comprises:

means for obtaining a signal-to-noise ratio (SNR) threshold for a number and time of arrival (TOA) of the target cells from the positioning measurement configuration;

means for selecting a set of target cells from a set of available cells of the terminal device based on the number of target cells and a predetermined measurement order of the set of available cells;

means for performing the positioning measurement for each target cell of the set of target cells; and

means for determining at least one of a TOA of each target cell in the set of target cells, the SNR of the TOA, and a Reference Signal Time Difference (RSTD) as the measurement in response to the SNR of the TOA of each target cell in the set of target cells not being less than the SNR threshold of the TOA.

23. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any one of claims 1-6.

24. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any one of claims 7-10.