14 Barometric Pressure positioning methods

25.3053GPPRelease 17Stage 2 functional specification of User Equipment (UE) positioning in UTRANTS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

14.1 General

In the Barometric Pressure positioning method, the UE vertical component of the position is estimated by combining the measured atmospheric pressure and a reference atmospheric pressure. This is accomplished through barometric pressure sensors measuring atmospheric pressure at the UE, and applying a height determination algorithm using the reference atmospheric pressure.

Two positioning modes are supported:

– UE-Assisted: The UE performs Barometric Pressure measurements without assistance from the network and sends these measurements to the SAS/RNC where the vertical position calculation may take place, possibly using additional measurements from other sources;

– Standalone: The UE performs Barometric Pressure measurements and calculates its own vertical component of the position, possibly using additional measurements from other sources.

A UE with Barometric Pressure sensing capability operates without assistance from the network.

14.2 Information to be transferred between UTRAN Elements

This subclause defines the information (e.g., vertical position and/or measurement data) that may be transferred between UTRAN elements.

14.2.1 Information that may be transferred from the UE to Network

The information that may be signalled from UE to the SAS/RNC is listed in table 14.2.1-1.

Table 14.2.1-1: Information that may be transferred from UE to the Network

Information	UE‑assisted	Standalone
UE 3D position estimate with uncertainty shape	No	Yes
Indication of used positioning methods in the fix	No	Yes
Timestamp	Yes	Yes
Barometric Pressure measurements	Yes	No

The information reported from the UE to the Network depends on the positioning mode (i.e., standalone, or UE-assisted).

14.2.1.1 Standalone mode

In standalone mode, the UE reports the altitude, together with an estimate of the location uncertainty, if available.

The UE should also report an indication of which positioning method(s) have been used to calculate a fix.

14.2.1.2 UE-assisted mode

In UE-assisted mode, the UE reports the Barometric Pressure measurements together with associated quality estimates. These measurements enable the Network to calculate the vertical location of the UE, possibly using other measurements and data.

If requested by the SAS/RNC and supported by the UE, the UE may report Barometric Pressure measurements together with associated quality measurements, if available.

14.3 Location Information Transfer Procedure

The purpose of this procedure is to enable the SAS/RNC to request Barometric Pressure measurements or 3D position estimate from the UE, or to enable the UE to provide Barometric Pressure measurements to the SAS/RNC for vertical position calculation (e.g., in case of basic self location where the UE requests its own location).

14.3.1 SAS initiated Barometric Pressure positioning procedure

The following describes the signalling for the optional initiation of the network Barometric Pressure vertical positioning procedure by the SAS.

Figure 14.3.1-1: Barometric Pressure methods when initiated by the SAS

1. The operation begins with an authenticated request for positioning information about a UE from an application in the core network being received at the SRNC. The request from the CN may be a request for on-demand or periodic reporting. The SRNC acts as interface between the Core Network and the UE Positioning entities in the UTRAN.

2. The SRNC sends parameters received in the location request, including any periodic reporting information, together with the Cell ID and UE capability information to the SAS in a PCAP: Position Initiation Request message via the Iupc interface.

3. Depending on the UE capabilities, the SAS initiates a Barometric Pressure positioning procedure by sending a PCAP: Position Activation Request message that allows for the use of Barometric Pressure positioning (along with GPS or OTDOA, and optionally WLAN, Bluetooth or TBS positioning methods) to the SRNC via the Iupc interface. The PCAP Position Activation Request message may include periodic reporting information (number of reports and reporting interval).

4. The SRNC forwards to the UE the Barometric Pressure positioning request received from the SAS using RRC signalling. The SRNC also forwards in the RRC signalling message(s) the SAS request for either Barometric Pressure measurements, in the case of UE assisted, or a vertical position coordinate, in the case of standalone. The RRC signalling may include a request for periodic reporting as described in subclause 6.6.4.1 if this was received in step 3. For a description of standalone Barometric Pressure mode, jump to step 9.

5. For UE assisted Barometric Pressure, the SRNC requests from the UE the atmospheric pressure measurements. These measurements may be made while the UE is in RRC connected mode CELL_DCH state.

6. The UE returns to the SRNC the available barometric pressure measurements, together with a time stamp of when these values were obtained.

7. The information obtained in step 6 is sent from the SRNC to the SAS in a PCAP: Position Activation Response message.

8. The SAS calculates the vertical UE position. If periodic reporting was not requested in step 2, the SAS returns the UE position to the SRNC in a PCAP: Position Initiation Response message. If periodic reporting was requested in step 2, the SAS forwards the position information to the SRNC in a PCAP Position Periodic Result message. The PCAP Position Initiation Response or PCAP Position Periodic Result message may include the positioning method(s) used and an indication of whether the position estimate satisfies the requested accuracy or not.

9. In case of standalone method, the UE returns the vertical position estimate to the SRNC via RRC signalling. The SRNC forwards the position estimate to the SAS in a PCAP: Position Activation Response message. This estimate includes the position, the estimated accuracy of the results and the time of the estimate.

10. If periodic reporting was not requested in step 2, the SAS returns the resulting estimate to the SRNC in a PCAP: Position Initiation Response message. If periodic reporting was requested in step 2, the SAS forwards the position estimate to the SRNC in a PCAP Position Periodic Result message. The PCAP Position Initiation Response or PCAP Position Periodic Result message may include the positioning method(s) used and an indication of whether the position estimate satisfies the requested accuracy or not.

11. If there is insufficient information to yield a UE vertical positioning estimate satisfying the requested accuracy, the SAS may start a new process from step 3.

12. The SRNC passes the position estimate received from the SAS to the CN including the positioning method (or the list of the methods) used to obtain the position estimate. If the CN has requested accuracy for the position estimate, the Location response shall include an indication whether the position estimate satisfies the requested accuracy or not.

13. If periodic UE reporting was requested in step 4, the UE continues to send Barometric Pressure measurement reports one reporting interval after the previous measurement report. The SRNC forward the Barometric Pressure measurement report information to the SAS in a PCAP Position Periodic Report message. The SAS may calculate the UE vertical position and sends the position information to the SRNC in a PCAP Position Periodic Result message. The SRNC passes the new position estimate to the CN including, if available, the positioning method (or the list of the methods) used to obtain the position estimate. If the CN has requested accuracy for the position estimate, the Location response shall include an indication whether the position estimate satisfies the requested accuracy or not. This step 13 is repeated until the desired amount of reports has been attained or the procedure is cancelled by the CN or UTRAN. The SAS may send the final location estimate in a PCAP Position Initiation Response message to the SRNC, and the SRNC forwards the final location information to the CN.

14. If periodic UE reporting was not requested in step 4, but was requested in step 2, the SAS may repeat the steps 3 to 12 as for the first request until the desired amount of reports has been attained or the procedure is cancelled by the CN or UTRAN. When repeating step 10 for the final request, the SAS returns the resulting final position estimate to the SRNC in a PCAP: Position Initiation Response message.