8.5 Uplink positioning method

36.3053GPPEvolved Universal Terrestrial Radio Access Network (E-UTRAN)Release 17Stage 2 functional specification of User Equipment (UE) positioning in E-UTRANTS

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

8.5.1 General

In the uplink positioning method, the UE position is estimated based on timing measurements of uplink radio signals taken at different LMUs , along with knowledge of the geographical coordinates of the LMUs. The time required for a signal transmitted by a UE to reach a LMU is proportional to the length of the transmission path between the UE and the LMU. A set of LMUs is tasked to sample the UE signal at the same time.

The specific of any uplink positioning methods or techniques used to estimate the UE’s location from these measurements are beyond the scope of this specification.

In order to obtain uplink measurements, the LMUs need to know the characteristics of the SRS signal transmitted by the UE for the time period required to calculate uplink measurement. These characteristics should be static over the periodic transmission of SRS during the uplink measurements. Hence, the E-SMLC will indicate to the serving eNodeB the need to direct the UE to transmit SRS (see 5.2.2) signals for uplink positioning. It is up to the eNodeB to make the final decision on resources to be assigned and to communicate this configuration information back to the E-SMLC so that E-SMLC can configure the LMUs. The eNB may decide (e.g., in case no resources are available) to configure no resources for the UE and report the empty resource configuration to the E-SMLC.

8.5.2 Transferred information

This clause defines the information that may be transferred between E-SMLC and eNodeB/LMU.

UTDOA measurements are performed on Sounding Reference Signals (SRS), configured as periodic SRS involving multiple SRS transmissions.

NOTE: The tables in clauses 8.5.2.1, 8.5.2.2, and 8.5.2.3 will be updated if needed.

8.5.2.1 Configuration Data that may be transferred from the eNodeB to the E-SMLC

The following configuration data may be transferred from the eNodeB to the E-SMLC:

Parameter Category	Parameters
General	PCI of PCell ^{Note 1} UL-EARFCN of PCell Timing advance measurement for the UE in PCell [36.214] ^{Note 3}
SRS	For each serving cell in which SRS is configured ^Note2: – PCI – UL-EARFCN – UL cyclic prefix – UL system bandwidth of the cell – Cell-specific SRS bandwidth configuration srs-BandwidthConfig [36.211] – UE-specific SRS bandwidth configuration srs-Bandwidth [36.211] – number of antenna ports for SRS transmission srs-AntennaPort [36.211] – frequency domain position [36.211] – SRS frequency hopping bandwidth configuration [36.211] – SRS-Cyclic shift [36.211] – Transmission comb [36.211] – SRS configuration index [36.213] – MaxUpPt, used for TDD only [36.211] – Group-hopping-enabled [36.211] – deltaSS, parameter [36.211, 5.5.1.3], included when SRS sequence hopping is used [36.211, 5.5.1.4] and not included otherwise
Note 1: Indicating PCell should not imply configuring SRS on the PCell Note 2: Multiple serving cells are possible for a UE configured with CA Note 3: Used for search window calculation

8.5.2.2 Configuration Data that may be transferred from the E-SMLC to LMU

The following configuration data may be transferred from the E-SMLC to LMU:

Parameter Category	Parameters
General	Search window parameters ^{Note 2}: – expected propagation delay, T, corresponding to distance between LMU and PCell, – delay uncertainty ∆
SRS	For each serving cell in which SRS is configured and to be measured by LMU ^Note1: – PCI – UL-EARFCN – UL cyclic prefix – UL system bandwidth of the cell – Cell-specific SRS bandwidth configuration srs-BandwidthConfig [36.211] – UE-specific SRS bandwidth configuration srs-Bandwidth [36.211] – number of antenna ports for SRS transmission srs-AntennaPort [36.211] – frequency domain position [36.211] – SRS frequency hopping bandwidth configuration [36.211] – SRS-Cyclic shift [36.211] – Transmission comb [36.211] – SRS configuration index [36.213] – MaxUpPt, used for TDD only [36.211] – Group-hopping-enabled [36.211] – deltaSS, parameter [36.211, 5.5.1.3], included when SRS sequence hopping is used [36.211, 5.5.1.4] and not included otherwise
Note 1: Multiple serving cells are possible for a UE configured with CA; SRS may be transmitted on the PCell and/or SCell(s). Note 2: Search window is calculated by the LMU as [T-∆,T+∆], where ∆ may be e.g. the timing advance measurement provided by eNodeB.

8.5.2.3 Location Information that may be transferred from the LMU to E-SMLC

The information that may be transferred from LMU to the E-SMLC is listed in Table 8.5.2.3-1. The individual measurements will be defined in TS 36.214 [20].

Table 8.5.2.3-1: Information that may be transferred from LMU to the E-SMLC

Information	Measurements
Uplink Measurement Results List for EUTRA	UL Relative Time of Arrival
Uplink Measurement Results List for EUTRA	Physical cell IDs

8.5.3 Uplink Positioning Procedures

The procedures described in this clause support the uplink positioning method.

8.5.3.1 Uplink Information Request and Delivery Procedure

The Information Request procedure for Uplink positioning is used by the E-SMLC to obtain measurement results from the LMU which it uses to calculate a position for the UE. To do this, it needs to first indicate to the serving eNB the need to configure the UE to transmit SRS (see 5.2.2) signals and retrieve target UE configuration data from the eNodeB.

Figure 8.5.3.1-1 shows the messaging between the E-SMLC, the LMU and the serving eNodeB to perform this procedure.

Figure 8.5.3.1-1: Uplink information request procedure

1. The E-SMLC sends an Information Request message indicating to the eNodeB the need to invoke periodic SRS (see 5.2.2) for target UE. The E-SMLC may provide the eNB with a number of SRS transmissions. The final decision of SRS transmissions to be performed and whether to take into account this information is entirely up to the eNB implementation.

2. The eNodeB determines the resources to be allocated for the UE and sends an Information Response to the E-SMLC that includes the allocated resources and the associated parameters. The eNB may decide (e.g., in case no resources are available) to configure no resources for the UE and report the empty resource configuration to the E-SMLC.

3. If in step 2 the eNodeB determines that resources will be allocated, the eNodeB then allocates the resources to the target UE.

4. The E-SMLC selects a set of LMUs to be used for the UTDOA positioning and sends a measurement request with the SRS configuration to each one of them (via SLm).

5. LMUs report back to E-SMLC the uplink measurement reports.

8.5.3.2 Uplink Positioning Information Update Procedure

This procedure is used to notify the E-SMLC of a change to the UE SRS transmission configuration for one or more cells with respect to a previously sent UTDOA INFORMATION RESPONSE message. If the configured SRS transmission for the target UE has been modified, or if a handover of the target UE has been triggered, the eNB uses the Uplink Positioning Information Update procedure to inform the E-SMLC.

Figure 8.5.3.2-1: Uplink Positioning Information Update Procedure

1. If the SRS configuration changes or if a handover of the target UE has been triggered prior to the expected completion time of the previously communicated SRS configuration, the eNB initiates the Uplink Positioning Information Update Procedure. In the case of handover, the source eNB sends the update message after deciding to perform handover execution for the UE.

2. If the UE SRS transmission configuration has changed for one or more cells, the eNB sends an Uplink Positioning Information Update message to the E-SMLC carrying the UE SRS transmission configuration information for all cells with SRS configured.