Content for TS 38.305 Word version: 18.0.0

1… 4… 5… 6… 6.5… 6.7… 7… 7.3A… 7.4… 7.6… 7.11… 7.12… 8… 8.1.2.1a… 8.1.3… 8.2… 8.3… 8.4… 8.5… 8.6… 8.7… 8.8… 8.9… 8.10… 8.11… 8.12… 8.13… 8.14… 8.15… A…

7.12 General UE-only sidelink positioning and ranging procedure 7.13 Positioning Integrity 7.13.1 General 7.13.2 Integrity Principle of Operation
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7.12 General UE-only sidelink positioning and ranging procedure |R18| p. 69

Figure 7.12-1 shows the sequence of operation for sidelink positioning and ranging in the UE only mode of operation as further defined in TS 23.586.

Reproduction of 3GPP TS 38.305, Fig. 7.12-1: Procedure for sidelink positioning and ranging (UE-only operation)

Figure 7.12-1: Procedure for sidelink positioning and ranging (UE-only operation)

Step 1.

UE1 (e.g., target UE) may receive a Ranging/SL Positioning Service Request from a client UE or from its own application layer as defined in TS 23.586.

Step 2.

UE1 discovers UEs 2 to n, as described in TS 23.586, if not already discovered.

Step 3.

UE1 may obtain the sidelink positioning capabilities from UEs 2 to n using the SLPP Capability Transfer procedure described in clause 7.11.2.1.

Step 4.

If UE1 does not support SL Server UE functionality or decides to select a different SL Server UE, a SL Server UE may be discovered (if not already discovered at step 2) and selected as described in TS 23.586.

Step 5.

If step 4 was performed, UE1 may send a Supplementary RSPP SL Positioning/Ranging Service Request message to the SL Server UE including the Application layer IDs of UEs 1 to n together with an indication of location results requested (e.g., absolute location, relative location or distances and directions) and desired QoS.

Step 6.

If step 4 was performed, the SL Server UE may request the SL positioning and ranging capabilities of UE1 using the SLPP Capability Transfer procedure described in clause 7.11.2.1.

Step 7.

If step 4 was performed, the SL Server UE may request the SL positioning and ranging capabilities of UEs 2 to n using the Supplementary RSPP Capability Transfer Procedure. The Supplementary RSPP Capability Transfer messages may include embedded SLPP Capability Transfer messages for UEs 2 to n together with their Application Layer IDs. If step 3 did not occur, UE1 obtains the sidelink positioning capabilities from UEs 2 to n using the SLPP Capability Transfer procedure described in clause 7.11.2.1 at this step.

Step 8.

If step 4 was performed, the SL Server UE may provide assistance data for UE1 using the SLPP Assistance Data Transfer procedure described in clause 7.11.2.2.

Step 9.

If step 4 was performed, the SL Server UE may provide assistance data for UEs 2 to n using the Supplementary RSPP Assistance Data Transfer Procedure. The Supplementary RSPP Assistance Data Transfer messages may include embedded SLPP Assistance Data Transfer messages for UEs 2 to n together with their Application Layer IDs.

Step 10.

UE1 may provide assistance data to UEs 2 to n using the SLPP Assistance Data Transfer procedure described in clause 7.11.2.2. If step 9 was performed, the SLPP Provide Assistance Data message includes the assistance data received from the SL Server UE at step 9.

Step 11.

If step 4 was performed, the SL Server UE may send a SLPP Request Location Information message to UE1 as described in clause 7.11.2.3 if the ranging/positioning result determination is performed by the SL Server UE.

Step 12.

If step 4 was performed, the SL Server UE may request location information for UEs 2 to n using the Supplementary RSPP Location Information Transfer Procedure if the ranging/positioning result determination is performed by the SL Server UE. The Supplementary RSPP Location Information Transfer messages may include embedded SLPP Request Location Information messages for UEs 2 to n together with their Application Layer IDs.

Step 13.

UE1 may send a request for sidelink location information to UEs 2 to n using the SLPP Location Information Transfer procedure described in clause 7.11.2.3. If step 12 was performed, the SLPP Location Information Request message includes the information received from the SL Server UE at step 12.

Step 14.

If step 11 was performed, UE1 sends a SLPP Provide Location Information message containing the sidelink location information obtained by UE1 to the SL Server UE as described in clause 7.11.2.3.

Step 15.

If step 12 was performed, UE1 provides the sidelink location information from UEs 2 to n to the SL Server UE using the Supplementary RSPP Location Information Transfer procedure. The Supplementary RSPP Location Information Transfer messages may include embedded SLPP Provide Location Information messages for UEs 2 to n together with their Application Layer IDs.

Step 16.

If steps 11 or 12 (and 14 or 15) were performed, the SL Server UE performs the ranging/SL positioning results calculation.

Step 17.

If step 5 was performed, the SL Server UE sends a SL Positioning/Ranging Service Response to UE1 including the results requested in step 5.

Step 18.

The ranging/positioning result is delivered to the requestor from step 1.

7.13 Positioning Integrity |R18| p. 70

7.13.1 General p. 70

Positioning Integrity is supported for the following positioning methods:

GNSS positioning methods as specified in clause 8.1;
Multi-RTT positioning as specified in clause 8.10;
DL-AoD positioning as specified in clause 8.11;
DL-TDOA positioning as specified in clause 8.12;
UL-TDOA positioning as specified in clause 8.13;
UL-AoA positioning as specified in clause 8.14.

For UE-assisted mode and network-based positioning, an LMF may address the UE and TRP local errors from UE and/or TRP measurement results. A specific method for determining local UE and TRP errors/threats is not specified as this is implementation defined.

7.13.2 Integrity Principle of Operation p. 71

For integrity operation, the network will ensure that:

P(Error > Bound for longer than TTA | NOT DNU) ≤ Residual Risk + IRallocation

(Equation 7.13.2-1)

for all values of IRallocation in the range: irMinimum ≤ IRallocation ≤ irMaximum

for all the errors in Table 8.1.2.1b-1, Table 8.11.2.1.1-1, and Table 8.12.2.1.1-1 which have corresponding integrity assistance data available and where the corresponding DNU flag(s) are set to false.

The integrity risk probability is decomposed into a constant Residual Risk component provided in the assistance data as well as a variable IRallocation component that corresponds to the contribution from the Bound according to the Bound formula in Equation 7.13.2-2. IRallocation may be chosen freely by the client based on the desired Bound, therefore the network should ensure that Equation 7.13.2-1 holds for all possible choices of IRallocation. The Residual Risk and IRallocation components may be mapped to fault and fault-free cases respectively, but the implementation is free to choose any other decomposition of the integrity risk probability into these two components.

For GNSS Integrity in SSR, the validity time of the integrity bounds is set as equal to twice the SSR Update Interval for the given SSR Assistance Data message, i.e. the time period between the SSR Epoch Time and the SSR Epoch Time plus twice the SSR Update Interval in the GPS time scale.

Equation 7.13.2-1 holds for all assistance data that has been issued that is still within its validity period. If this condition cannot be met then the corresponding DNU flag must be set.

Equation 7.13.2-1 holds at any epochs for which Assistance Data is provided. Providing Assistance Data without the Integrity Service Alert IE or GNSS Real Time Integrity IEs (in the case of GNSS) is interpreted as a DNU=FALSE condition. For any bound that is still valid (within its validity time), the network ensures that the Integrity Service Alert and/or GNSS Real Time Integrity IEs (in the case of GNSS) are also included in the provided Assistance Data if needed to satisfy the condition in Equation 7.13.2-1. It is up to the implementation how to handle epochs for which integrity results are desired but there are no DNU flag(s) available, e.g. the Time To Alert (TTA) may be set such that there is a "grace period" to receive the next set of DNU flags.

Only those satellites and TRPs for which the integrity assistance data are provided are monitored by the network and can be used for integrity related applications.

Where:

Error:

Error is the difference between the true value of a parameter (e.g. ionosphere, troposphere etc. in the case of GNSS, or ARP location, RTD, etc. in the case of NR positioning), and its value as estimated and provided in the corresponding assistance data as per Table 8.1.2.1b-1, Table 8.11.2.1.1-1, and Table 8.12.2.1.1-1.

Bound:

In the case of GNSS, Integrity Bounds provide the statistical distribution of the residual errors associated with the GNSS positioning corrections (e.g. RTK, SSR etc). In the case of GNSS, integrity bounds are used to statistically bound the residual errors after the positioning corrections have been applied.

In the case of NR positioning, Integrity Bounds provide the statistical distribution of the errors.

The bound is computed according to the Bound formula defined in Equation 7.13.2-2. The bound formula describes a bounding model including a mean and standard deviation (e.g. paired over-bounding Gaussian). The bound may be scaled by multiplying the standard deviation by a K factor corresponding to an IRallocation, for any desired IRallocation within the permitted range.

The bound for a particular error is computed according to the following formula:

Bound = mean + K * stdDev

K = normInv(IRallocation / 2)

irMinimum ≤ IRallocation ≤ irMaximum

(Equation 7.13.2-2)

where:

mean:

mean value for this specific error, as per Table 8.1.2.1b-1, Table 8.11.2.1.1-1, and Table 8.12.2.1.1-1.

stdDev:

standard deviation for this specific error, as per Table 8.1.2.1b-1, Table 8.11.2.1.1-1, and Table 8.12.2.1.1-1.

Time-to-Alert (TTA):

The maximum allowable elapsed time from when the Error exceeds the Bound until a DNU flag must be issued.

Target Integrity Risk (TIR):

The probability per unit of time that the Error exceeds the Bound without issuing a DNU flag within the TTA.

DNU:

The DNU flag(s) corresponding to a particular error as per Table 8.1.2.1b-1, Table 8.11.2.1.1-1, and Table 8.12.2.1.1-1. Where multiple DNU flags are specified, the DNU condition in Equation 7.13.2-1 is present when any of the flags are true (logical OR of the flags).

Residual Risk:

The residual risk is the component of the integrity risk provided in the assistance data as per Table 8.1.2.1b-1, Table 8.11.2.1.1-1, and Table 8.12.2.1.1-1. This may correspond to the fault case risk but the implementation is permitted to allocate this component in any way that satisfies Equation 7.13.2-1.

The Residual Risk is the Probability of Onset which is defined per unit of time and represents the probability that the feared event begins. Each Residual Risk is accompanied by a Mean Duration which represents the expected mean duration of the corresponding feared event and is used to convert the Probability of Onset to a probability that the feared event is present at any given time, i.e.

P(Feared Event is Present) = Mean Duration * Probability of Onset of Feared Event

(Equation 7.13.2-3)

irMinimum, irMaximum:

Minimum and maximum allowable values of IRallocation that may be chosen by the client. Provided as service parameters from the Network according to Integrity Service Parameters.

Correlation Times:

The minimum time interval beyond which two sets of assistance data parameters for a given error can be considered to be independent from one another.