Content for TS 38.305 Word version: 18.0.0

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8.1.2.1a Recommendations for grouping of assistance data to support different RTK service levels 8.1.2.1b Mapping of integrity parameters 8.1.2.2 Information that may be transferred from the UE to LMF 8.1.2.2.0 General 8.1.2.2.1 GNSS Measurement Information 8.1.2.2.1.0 General 8.1.2.2.1.1 UE-based mode 8.1.2.2.1.2 UE-assisted mode 8.1.2.2.2 Additional Non-GNSS Related Information
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8.1.2.1a Recommendations for grouping of assistance data to support different RTK service levels p. 79

This clause provides recommendations for the different high-accuracy GNSS service levels: RTK, N-RTK, PPP and PPP-RTK.

The high-accuracy GNSS methods can be classified as:

Single base RTK service: RTK is a technique that uses carrier-based ranging measurements i.e., phase-range to improve the positioning accuracy in a differential approach. The basic concept is to reduce and remove errors common to a Reference Station, with known position, and UE pair. When only pseudo ranges (code-based measurements) are used to compute the UE location, this method is known as DGNSS (Differential GNSS).

Table 8.1.2.1a-1: Single base RTK service: Specific information that may be transferred from the LMF to the UE

Assistance Data
RTK Reference Station Information
RTK Observations
RTK Common Observation Information
GLONASS RTK Bias Information (if GLONASS data is transmitted)
Ephemeris and Clock (if UE did not acquire the navigation message)

Non-Physical Reference Station Network RTK service: In this approach the target UE receives synthetic observations from a fictitious Reference Station. The Network RTK software at the location server is performing the error estimation and creates a virtual Reference Station close to the initial location of the target device (provided a priori to the location server). The target UE interprets and uses the data just as if it had come from a single, real Reference Station. Additionally, the target UE can also receive network information such as RTK Network Residuals (see clause 8.1.2.1.19) or even FKP gradients (see clause 8.1.2.1.20).

Table 8.1.2.1a-2: Non-Physical Reference Station Network RTK service: Specific information that may be transferred from the LMF to the UE

Assistance Data
RTK Reference Station Information
RTK Observations
RTK Common Observation Information
GLONASS RTK Bias Information (if GLONASS data is transmitted)
RTK Residuals
RTK FKP Gradients
Ephemeris and Clock (if UE did not acquire the navigation message)

MAC Network RTK service: In MAC network RTK, a group of Reference Stations are used and one of them is chosen as a Master station. The other stations are then called Auxiliary stations. In this service, the location server sends full raw observations and coordinate information for a single Reference Station, the Master Station. For all auxiliary stations in the network (or a suitable subset of stations) the information is provided to the UE in a highly compact form: their reduced ambiguity-levelled observations, coordinate differences (to the Master Station observations and coordinates), and network residuals. Two Reference Stations are said to be on a common ambiguity level if the integer ambiguities for each phase range (satellite-receiver pair) have been removed (or adjusted) so that the integer ambiguities cancel when double-differences (involving two receivers and two satellites) are formed during processing. The maintenance of a common ambiguity level at a specific set of stations rather than across the whole GNSS network will lead to a grouping in network clusters or subnetworks of all ambiguity-levelled Reference Stations. If one network has only one subnetwork, this indicates that an ambiguity level throughout the whole network is established. When subnetworks are predefined, the assistance data can be broadcast to all UEs located in the assigned sub-network. More details on the usage of subnetworks can be found in [31].

Table 8.1.2.1a-3: MAC Network RTK service: Specific Information that may be transferred from the LMF to the UE

Assistance Data
RTK Reference Station Information
RTK Auxiliary Station Data
RTK Observations
RTK Common Observation Information
GLONASS RTK Bias Information (if GLONASS data is transmitted)
RTK MAC Correction Differences
RTK Residuals
Ephemeris and Clock (if UE did not acquire the navigation message)

FKP Network RTK service: With the concept of FKP, horizontal gradients of distance-dependent errors like ionosphere, troposphere and orbits are derived from a network of GNSS Reference Stations and transmitted to a target device together with raw or correction data of a corresponding Reference Station (physical or non physical). The target UE may use the gradients to compute the effect of the distance-dependent errors for its own position.

Table 8.1.2.1a-4: FKP Network RTK service: Information that may be transferred from the LMF to the UE

Assistance Data
RTK Reference Station Information
RTK Observations
RTK Common Observation Information
GLONASS RTK Bias Information (if GLONASS data is transmitted)
RTK Residuals
RTK FKP Gradients
Ephemeris and Clock (if UE did not acquire the navigation message)

PPP service: This concept uses precise satellite orbit and clock parameters derived from global networks of Reference Stations as well as atmospheric models to perform single station positioning [31]. Compared to RTK and Network RTK, PPP is not a differential technique as there is no baseline limitation. When the orbits and clocks assistance data elements are provided in real-time, with no latency, the method is called Real-Time PPP.

Table 8.1.2.1a-5: SSR PPP service: Information that may be transferred from the LMF to the UE

Assistance Data
SSR Orbit Corrections
SSR Clock corrections
SSR Code Bias
Ephemeris and Clock (if UE did not acquire the navigation message)
SSR IOD Update
SSR Satellite PCV Residuals

PPP-RTK service: This concept uses precise satellite orbits and clock parameters, the satellite signal biases derived from global networks of Reference Stations as well as ionosphere and troposphere corrections to perform single station positioning IS-QZSS-L6-001 [36]. Therefore, PPP-RTK services compensate the global and local corrections for a more accurate location information. Compared to PPP, PPP-RTK requires the UE to be located within the region covered by the ionosphere and troposphere corrections.

Table 8.1.2.1a-6: SSR PPP-RTK service: Information that may be transferred from the LMF to the UE

Assistance Data
SSR Orbit Corrections
SSR Clock corrections
SSR Code Bias
Ephemeris and Clock (if UE did not acquire the navigation message)
SSR Phase Bias
SSR STEC Corrections
SSR Gridded Correction
SSR URA
SSR Correction Points
SSR IOD Update
SSR Satellite PCV Residuals

8.1.2.1b Mapping of integrity parameters |R17| p. 82

Table 8.1.2.1b-1 shows the mapping between the integrity fields and the SSR assistance data according to the Integrity Principle of Operation (Clause 7.13.2). The corresponding field descriptions for each of the field names listed in Table 8.1.2.1b-1 are specified under Clause 6.5.2.2 of TS 37.355.

Table 8.1.2.1b-1: Mapping of Integrity Parameters

Error	GNSS Assistance Data	Integrity Fields
Error	GNSS Assistance Data	Integrity Alerts	Integrity Bounds (Mean)	Integrity Bounds (StdDev)	Residual Risks	Integrity Correlation Times
Orbit	SSR Orbit Corrections	Real-Time Integrity (see 8.1.2.1.8)	Mean Orbit Error Mean Orbit Rate Error (Calculated according to Equation 8.1.2.1.21-1)	Standard Deviation Orbit Error Standard Deviation Orbit Rate Error (Calculated according to Equation 8.1.2.1.21-1)	Probability of Onset of Constellation Fault Probability of Onset of Satellite Fault Mean Constellation Fault Duration Mean Satellite Fault Duration	Orbit Range Error Correlation Time Orbit Range Rate Error Correlation Time
Clock	SSR Clock Corrections		Mean Clock Error Mean Clock Rate Error	Standard Deviation Clock Error Standard Deviation Clock Rate Error		Clock Range Error Correlation Time Clock Range Rate Error Correlation Time
Code Bias	SSR Code Bias		Mean Code Bias Error Mean Code Bias Rate Error	Standard Deviation Code Bias Error Standard Deviation Code Bias Rate Error
Phase Bias	SSR Phase Bias SSR Satellite PCV Residuals		Mean Phase Bias Error Mean Phase Bias Rate Error	Standard Deviation Phase Bias Error Standard Deviation Phase Bias Rate Error
Ionosphere	SSR STEC Correction	Ionosphere DNU	Mean Ionospherre Error Mean Ionospherre Rate Error	Standard Deviation Ionosphere Error Standard Deviation Ionosphere Rate Error	Probability of Onset of Ionosphere Fault Mean Ionosphere Fault Duration	Ionosphere Range Error Correlation Time Ionosphere Range Rate Error Correlation Time
Troposphere Vertical Hydro Static Delay	SSR Gridded Corrections	Troposphere DNU	Mean Troposphere Vertical Hydro Static Delay Error Mean Troposphere Vertical Hydro Static Delay Rate Error	Standard Deviation Troposphere Vertical Hydro Static Delay Error Standard Deviation Troposphere Vertical Hydro Static Delay Rate Error	Probability of Onset of Troposphere Fault Mean Troposphere Fault Duration	Troposphere Range Error Correlation Time Troposphere Range Rate Error Correlation Time
Troposphere Vertical WetDelay	SSR Gridded Corrections	Troposphere DNU	Mean Troposphere Vertical Wet Delay Error Mean Troposphere Vertical Wet Delay Rate Error	Standard Deviation Troposphere Vertical Wet Delay Error Standard Deviation Troposphere Vertical Wet Delay Rate Error

8.1.2.2 Information that may be transferred from the UE to LMF p. 84

8.1.2.2.0 General |R18| p. 84

The information that may be signalled from UE to the LMF is listed in Table 8.1.2.2.0-1.

Table 8.1.2.2.0-1: Information that may be transferred from UE to the LMF

Information	UE-assisted	UE-based / standalone
Latitude/Longitude/Altitude, together with uncertainty shape	No	Yes
Velocity, together with uncertainty shape	No	Yes
Reference Time, possibly together with GNSS to NG-RAN time association and uncertainty	Yes	Yes
Indication of used positioning methods in the fix	No	Yes
Code phase measurements, also called pseudorange	Yes	No
Doppler measurements	Yes	No
Carrier phase measurements, also called Accumulated Delta Range (ADR)	Yes	No
Carrier-to-noise ratio of the received signal	Yes	No
Measurement quality parameters for each measurement	Yes	No
Additional, non-GNSS related measurement information	Yes	No
Protection Level, optionally together with achievable Target Integrity Risk	No	Yes

8.1.2.2.1 GNSS Measurement Information p. 84

8.1.2.2.1.0 General p. 84

The GNSS measurement information reported from the UE to the LMF depends on the GNSS mode (i.e., UE-based, autonomous (standalone), or UE-assisted).

8.1.2.2.1.1 UE-based mode p. 84

In UE-based or standalone mode, the GNSS receiver reports the latitude, longitude and possibly altitude, together with an estimate of the location uncertainty, if available.

If requested by the LMF and supported by the UE, the GNSS receiver may report its velocity, possibly together with an estimate of the uncertainty, if available.

If requested by the LMF and supported by the UE, the GNSS receiver may report the relation between GNSS system time (where the specific GNSS is indicated by a GNSS ID; the specific GNSS system time may be selected by the UE) and NG-RAN air-interface timing. This information may be used by the LMF to assist other UEs in the network.

The UE should also report an indication of which GNSSs and possibly other location methods have been used to calculate a fix.

8.1.2.2.1.2 UE-assisted mode p. 84

In UE-assisted mode, the GNSS receiver reports the Code Phase and Doppler measurements together with associated quality estimates. These measurements enable the LMF to calculate the location of the UE, possibly using other measurements and data.

If requested by the LMF and supported by the UE, the GNSS receiver may report Carrier Phase measurements (also called Accumulated Delta Range), together with associated quality measurements, if available.

8.1.2.2.2 Additional Non-GNSS Related Information p. 85

Additional non-GNSS measurements performed by NG-RAN or UE may be used by the LMF or UE to calculate or verify a location estimate. This information may include OTDOA positioning measurements, pathloss and signal strength related measurements, etc.