5 A-GNSS minimum performance requirements (UE supports A-GPS L1 C/A only)
38.1713GPPNRRelease 17Requirements for Support of Assisted Global Navigation Satellite System (A-GNSS)TS
5.0 Introduction
The minimum performance requirements specified in clause 5 apply for UEs that support A-GPS L1 C/A only. The requirements for UEs that support other or additional A-GNSSs are specified in clause 6.
The A-GNSS minimum performance requirements are defined by assuming that all relevant and valid assistance data is received by the UE in order to perform GPS L1 C/A measurements and/or position calculation. This clause does not include nor consider delays occurring in the various signalling interfaces of the network.
In the following clauses the minimum performance requirements are based on availability of the assistance data information and messages defined in annexes D and E.
5.1 Sensitivity
A sensitivity requirement is essential for verifying the performance of A-GNSS receiver in weak satellite signal conditions. In order to test the most stringent signal levels for the satellites the sensitivity test case is performed in AWGN channel. This test case verifies the performance of the first position estimate, when the UE is provided with only coarse time assistance and when it is additionally supplied with fine time assistance.
5.1.1 Coarse time assistance
In this test case 8 satellites are generated for the terminal. AWGN channel model is used.
Table 5.1: Test parameters
|
Parameters |
Unit |
Value |
|---|---|---|
|
Number of generated satellites |
– |
8 |
|
HDOP Range |
– |
1.1 to 1.6 |
|
Propagation conditions |
– |
AWGN |
|
GNSS Coarse time assistance error range |
seconds |
±2 |
|
GPS L1 C/A Signal for one satellite |
dBm |
-142 |
|
GPS L1 C/A Signal for remaining satellites |
dBm |
-147 |
5.1.1.1 Minimum requirements (Coarse time assistance)
The position estimates shall meet the accuracy and response time specified in Table 5.2.
Table 5.2: Minimum requirements (coarse time assistance)
|
Success rate |
2-D position error |
Max response time |
|---|---|---|
|
95 % |
100 m |
20 s |
5.1.2 Fine time assistance
This requirement is only valid for fine time assistance capable UEs. In this requirement 8 satellites are generated for the terminal. AWGN channel model is used.
Table 5.3: Test parameters for fine time assistance capable terminals
|
Parameters |
Unit |
Value |
|---|---|---|
|
Number of generated satellites |
– |
8 |
|
HDOP Range |
– |
1.1 to 1.6 |
|
Propagation conditions |
– |
AWGN |
|
GNSS Coarse time assistance error range |
seconds |
±2 |
|
GPS L1 C/A Fine time assistance error range |
μs |
±10 |
|
GPS L1 C/A Signal for all satellites |
dBm |
-147 |
5.1.2.1 Minimum requirements (Fine time assistance)
The position estimates shall meet the accuracy and response time requirements in Table 5.4.
Table 5.4: Minimum requirements for fine time assistance capable terminals
|
Success rate |
2-D position error |
Max response time |
|---|---|---|
|
95 % |
100 m |
20 s |
5.2 Nominal accuracy
Nominal accuracy requirement verifies the accuracy of A-GNSS position estimate in ideal conditions. The primarily aim of the test is to ensure good accuracy for a position estimate when satellite signal conditions allow it. This test case verifies the performance of the first position estimate.
In this requirement 8 satellites are generated for the terminal. AWGN channel model is used.
Table 5.5: Test parameters
|
Parameters |
Unit |
Value |
|---|---|---|
|
Number of generated satellites |
– |
8 |
|
HDOP Range |
– |
1.1 to 1.6 |
|
Propagation conditions |
– |
AWGN |
|
GNSS Coarse time assistance error range |
seconds |
±2 |
|
GPS L1 C/A Signal for all satellites |
dBm |
-130 |
5.2.1 Minimum requirements (nominal accuracy)
The position estimates shall meet the accuracy and response time requirements in Table 5.6.
Table 5.6: Minimum requirements
|
Success rate |
2-D position error |
Max response time |
|---|---|---|
|
95 % |
30 m |
20 s |
5.3 Dynamic range
The aim of a dynamic range requirement is to ensure that a GNSS receiver performs well when visible satellites have rather different signal levels. Strong satellites are likely to degrade the acquisition of weaker satellites due to their cross‑correlation products. Hence, it is important in this test case to keep use AWGN in order to avoid loosening the requirements due to additional margin because of fading channels. This test case verifies the performance of the first position estimate.
In this requirement 6 satellites are generated for the terminal. AWGN channel model is used.
Table 5.7: Test parameters
|
Parameters |
Unit |
Value |
|---|---|---|
|
Number of generated satellites |
– |
6 |
|
HDOP Range |
– |
1.4 to 2.1 |
|
GNSS Coarse time assistance error range |
seconds |
±2 |
|
Propagation conditions |
– |
AWGN |
|
GPS L1 C/A Signal for 1st satellite |
dBm |
-129 |
|
GPS L1 C/A Signal for 2nd satellite |
dBm |
-135 |
|
GPS L1 C/A Signal for 3rd satellite |
dBm |
-141 |
|
GPS L1 C/A Signal for 4th satellite |
dBm |
-147 |
|
GPS L1 C/A Signal for 5th satellite |
dBm |
-147 |
|
GPS L1 C/A Signal for 6th satellite |
dBm |
-147 |
5.3.1 Minimum requirements (dynamic range)
The position estimates shall meet the accuracy and response time requirements in Table 5.8.
Table 5.8: Minimum requirements
|
Success rate |
2-D position error |
Max response time |
|---|---|---|
|
95 % |
100 m |
20 s |
5.4 Multi-path scenario
The purpose of the test case is to verify the receiver’s tolerance to multipath while keeping the test setup simple. This test case verifies the performance of the first position estimate.
In this requirement 5 satellites are generated for the terminal. Two of the satellites have one tap channel representing LOS signal. The three other satellites have two-tap channel, where the first tap represents LOS signal and the second reflected and attenuated signal as specified in Annex C.2.
Table 5.9: Test parameters
|
Parameters |
Unit |
Value |
|---|---|---|
|
Number of generated satellites (Satellites 1, 2 unaffected by multi-path) (Satellites 3, 4, 5 affected by multi-path) |
– |
5 |
|
GNSS Coarse time assistance error range |
seconds |
±2 |
|
HDOP Range |
– |
1.8 to 2.5 |
|
GPS L1 C/A Signal for satellite 1, 2 |
dBm |
-130 |
|
GPS L1 C/A Signal for satellite 3, 4, 5 |
dBm |
LOS signal of -130 dBm, multi-path signal of -136 dBm |
5.4.1 Minimum requirements (multi-path scenario)
The position estimates shall meet the accuracy and response time requirements in Table 5.10.
Table 5.10: Minimum requirements
|
Success rate |
2-D position error |
Max response time |
|---|---|---|
|
95 % |
100 m |
20 s |
5.5 Moving scenario and periodic update
The purpose of the test case is to verify the receiver’s capability to produce GNSS measurements or location fixes on a regular basis, and to follow when it is located in a vehicle that slows down, turns or accelerates. A good tracking performance is essential for certain location services. A moving scenario with periodic update is well suited for verifying the tracking capabilities of an A-GNSS receiver in changing UE speed and direction. In the requirement the UE moves on a rectangular trajectory, which imitates urban streets. AWGN channel model is used. This test is not performed as a TTFF test.
In this requirement 5 satellites are generated for the terminal. The UE is requested to use periodical reporting with a reporting interval of 2 seconds.
The UE moves on a rectangular trajectory of 940 m by 1 440 m with rounded corner defined in Figure 5.1. The initial reference is first defined followed by acceleration to final speed of 100 km/h in 250 m. The UE then maintains the speed for 400 m. This is followed by deceleration to final speed of 25 km/h in 250 m. The UE then turn 90 degrees with turning radius of 20 m at 25 km/h. This is followed by acceleration to final speed of 100 km/h in 250 m. The sequence is repeated to complete the rectangle.
Table 5.11: Trajectory Parameters
|
Parameter |
Distance (m) |
Speed (km/h) |
|
l11, l15, l21, l25 |
20 |
25 |
|
l12, l14, l22, l24 |
250 |
25 to 100 and 100 to 25 |
|
l13 |
400 |
100 |
|
l23 |
900 |
100 |
Figure 5.1: Rectangular trajectory of the moving scenario and periodic update test case
Table 5.12: Test Parameters
|
Parameters |
Unit |
Value |
|---|---|---|
|
Number of generated satellites |
– |
5 |
|
HDOP Range |
– |
1.8 to 2.5 |
|
Propagation condition |
– |
AWGN |
|
GPS L1 C/A signal for all satellites |
dBm |
-130 |
5.5.1 Minimum requirements (moving scenario and periodic update)
The position estimates shall meet the accuracy requirement of Table 5.13 with the periodical reporting interval defined in Table 5.13 after the first reported position estimates.
NOTE: In the actual testing the UE may report error messages until it is able to acquire GNSS measured results or a position estimate. The test equipment shall only consider the first measurement report different from an error message as the first position estimate in the requirement in Table 5.13.
Table 5.13: Minimum requirements
|
Success Rate |
2-D position error |
Periodical reporting interval |
|---|---|---|
|
95 % |
100 m |
2 s |