Title: Test Tolerance analysis for TS 34.122 Test cases 8.6.5.3 and 8.6.5.4

Source: CATT

1 Introduction

The test cases in sections 8.6.5.3 and 8.6.5.4 of 34.122, Combined UTRA TDD inter-frequency and E-UTRA FDD cell search under fading propagation conditions, have not been completed. The measurement uncertainty and test tolerance are missed, and 8.6.5.4 is currently absent. This document describes the process to derive the Test Tolerances. The calculations are provided in the accompanying spreadsheet.

2 Test case in TS 34.122

The test conditions are defined in the following extract from TC 8.6.5.3 in TS 34.122 v9.7.0 modified the thresholds (indicated by yellow). The modification including:

• Decrease T_{non used 2b} to -82 dBm from -80 dBm.

• Add a row in the Cell 1/2 specific parameters table giving the derived parameter Io in dBm/1.28MHz.

• Decrease T_{other_RAT} to -100dBm from -98dBm.

• Add a row in the Cell 3 specific parameters table giving the derived parameter Io in dBm/9MHz.

The thresholds of corresponding test cases in TS 25.123 are modified also in RAN4. The modification reason is that the margins are insufficient due to UE P-CCPCH RSCP measurement accuracy for cell 2 and UE RSRP measurement accuracy for cell 3 during T2 is ±8dB under the Io conditions defined and 3dB margin for fading, and the test cases may give an unpredictable or incorrect verdict.

8.6.5.1 Combined UTRA TDD inter-frequency and E-UTRA FDD cell search under fading propagation conditions

……

<<Some clauses skipped>>

8.6.5.3.4.2.1 Initial conditions

Test environment : normal; see clauses G.2.1 and G.2.2.

Frequencies to be tested : mid range; see clauses G.2.4.

This test scenario comprised of 2 UTRA TDD cells working on different frequency, and 1 E-UTRA FDD cell. General test parameters are given in the table 8.6.5.3.4.2-1, and they are signalled from test device. In the measurement control information it is indicated to the UE that event-triggered reporting with Event 2B and Event 3A shall be used. New measurement control information, which defines neighbour cells etc., is always sent before the event starts. Scheduled idle interval of 80ms period as defined in TS25.331 is provided. Two UTRA TDD cells shall be synchronised, i.e. sharing the same frame and timeslot timing.

The test consists of two successive time periods, with time duration of T1 and T2 respectively. The cell specific test parameters are shown in table 8.6.5.3.4.2-2 and table 8.6.5.3.4.2-3.

Table 8.6.5.3.4.2-1: General test parameters for combined UTRA TDD inter-frequency and E-UTRA FDD cells search under fading propagation conditions

Parameter	Unit	Value	Comment
DPCH parameters active cell		DL Reference Measurement Channel 12.2 kbps	As specified in TS 25.102 section A.2.2. The DPCH is located in an other timeslot than 0.
Active cell		Cell 1	1.28Mcps TDD cell operating on channel 1
Neighbour cell		Cell 2	1.28Mcps TDD cell operating on channel 2
		Cell 3	E-UTRA FDD cell
CP length of cell 3		Normal
Idle intervals period	ms	80	As specified in TS 25.331
Tused 2b	dBm	-73	Absolute P-CCPCH RSCP threshold for event 2B
Tnon used 2b	dBm	-82	Absolute P-CCPCH RSCP threshold for event 2B
Tused	dBm	-73	Absolute P-CCPCH RSCP threshold for event 3A
Tother_RAT	dBm	-100	Absolute RSRP threshold for event 3A
H2b	dB	0	The hysteresis parameter for the event 2B
H3a	dB	0	The hysteresis parameter for the event 3A
CIOother_RAT	dB	0	Cell individual offset for the cell of the other system
TimeToTrigger	ms	0
Filter coefficient		0	L3 filtering is not used
Monitored cell list size		24 on channel 1 16 on channel 2
T1	s	5	During T1, cell 2 and cell 3 shall be powered off, and during the off time the physical layer cell identity shall be changed.
T2	s	7

Table 8.6.5.3.4.2-2: Cell specific test parameters for combined UTRA TDD inter-frequency and E-UTRA FDD cell search under fading propagation conditions (cell 1 and cell 2)

Parameter	Unit	Cell 1 (UTRA)				Cell 2 (UTRA)
Timeslot Number		0		DwPTS		0		DwPTS
		T1	T2	T1	T2	T1	T2	T1	T2
UTRA RF Channel Number Note 1		Channel 1				Channel 2
PCCPCH_Ec/Ior	dB	-3				-3
DwPCH_Ec/Ior	dB			0				0
OCNS_Ec/Ior	dB	-3				-3
	dB	4+TT	4+TT	4+TT	4+TT	-Infinity	12+TT	-Infinity	12+TT
	dBm/1.28 MHz	-80
PCCPCH RSCP Note 2	dBm	-79+TT	-79+TT	n.a.		-Infinity	-71+TT	n.a.
IO Note 2	dBm/1.28 MHz	-74.54	-74.54	-74.54	-74.54	-80	-67.73	-80	-67.73
Propagation Condition		AWGN				Case 3
Note 1: In the case of multi-frequency network, the UTRA RF Channel Number can be set for the primary frequency in this test. Note 2: PCCPCH_RSCP and Io levels have been derived from other parameters for information purposes. They are not settable parameters themselves. Note3: The DPCH of all cells are located in a timeslot other than 0.

Table 8.6.5.3.4.2-3: Cell specific test parameters for combined UTRA TDD inter-frequency and E-UTRA FDD cell search under fading propagation conditions (cell 3)

Parameter	Unit	Cell 3
		T1	T2
E-UTRA RF Channel Number		3
BWchannel	MHz	10
OCNG Pattern defined in A.3.2.1.2 (OP.2 FDD) in [24]		OP.2 FDD	OP.2 FDD
PBCH_RA	dB	0	0
PBCH_RB	dB
PSS_RB	dB
SSS_RB	dB
PCFICH_PA	dB
PHICH_PA	dB
PHICH_PB	dB
PDCCH_PA	dB
PDCCH_PB	dB
PDSCH_PA	dB
PDSCH_PB	dB
OCNG_RANote1	dB
OCNG_RBNote1	dB
	dB	-Infinity	9+TT
	dBm/15kHz	-98
	dB	-Infinity	9+TT
RSRP Note 3	dBm/15kHz	-Infinity	-89+TT
SCH_RP Note 3	dBm/15kHz	-Infinity	-89+TT
IO Note 3	dBm/9MHz	-70.22	-60.70
Propagation Condition		ETU70 (Note 4)
Note 1: OCNG shall be used such that cell is fully allocated and a constant total transmitted power spectral density is achieved for all OFDM symbols. Note 2: The resources for uplink transmission are assigned to the UE prior to the start of time period T2. Note 3: RSRP, SCH_RP and IO levels have been derived from other parameters for information purposes. They are not settable parameters themselves. Note 4: ETU70 propagation conditions are specified in Annex B.2 of 3GPP TS 36.101.

……

We note that the level and time parameters in TS 25.123 TC A.8.5.4 are identical with TC A.8.5.3. In current specification TS34.122, the TC of Combined UTRA TDD inter-frequency and E-UTRA TDD cell search under fading propagation conditions is missed, and it should be added in section 8.6.5.4. The same treatment for Test Tolerances can be applied for both Test cases. We can ensure that the proposed solution can be applied to both E-UTRA FDD and E-UTRA TDD cell search test cases.

3 Discussion

In the test case, there are three cells, serving cell 1 (UTRA TDD cell), and neighbour cell 2 (UTRA TDD cell) and neighbour cell 3 (E-UTRA FDD cell). The test case consists of two successive time periods, T1 and T2. During T1, cell 2 and cell 3 shall be powered off, and the physical layer cell identity shall be changed. UE have not any timing information of cell 2 and cell 3. Idle interval of 80ms period is configured for monitoring E-UTRA cell. At starting T2, cell 2 and cell 3 becomes stronger than threshold T_{non used 2b} and T_{other_RAT}. The UE is expected to detect cell 2 and cell 3 and send an event 2B measurement report and an event 3A measurement report. The values of signal level for each cell versus time, together with the thresholds are shown in figure 1.

Figure 1 Signal levels and thresholds in the cell search test process

3.1 Handover criterion

The 2B event criterion for the test is as such:

• The serving cell 1 signal is below than the threshold T_{used_2b}, and neighbour cell 2(UTRA cell) signal is changed to higher than threshold T_{non used 2b} (note: here the hysteresis H_2b parameters are set to 0dB) with enough margin at start of T2.

• The UE will detect these conditions and will trigger an event 2B report with allowed delay after T2.

The 3A event criterion for the test is as such:

• The serving cell 1 signal is below than the threshold T_used, neighbour cell 3 (E-UTRA cell) signal is changed to higher than threshold T_{other_RAT} (note: here the offset CIO_{other_RAT} and hysteresis H_3a parameters are set to 0dB) with enough margin at start of T2.

• The UE will detect these conditions and will trigger an event 3A report with allowed delay after T2.

3.2 Test case verdict

The design of the test case relies on:

• The UE being able to measure cell 1 RSCP within accuracy requirements during T2, and correctly compare it to the signal thresholds T_{used_2b} and T_used.

• The UE being able to search cell 2 and measure cell 2 RSCP within accuracy requirements during T2, and correctly compare it to the signal threshold T_{non used 2b}.

• The UE being able to search cell 3 and measure cell 3 RSRP within accuracy requirements during T2, and correctly compare it to the signal threshold T_{other_RAT}.

A detailed analysis of the test case is given in section 5 of this document.

4 Choice and values of uncertainties to be specified

The SS provides AWGN and three cells on different frequencies to the UE. We propose to control the following parameters:

• AWGN absolute power on cell 1 frequency, I_oc ± 0.7dB

• AWGN absolute power on cell 2 frequency, I_oc ± 0.7dB

• AWGN absolute power on cell 3 frequency, N_oc ± 0.7dB

• Ratio of cell 1 and cell 2 code level / I_or , Ec / I_or ± 0.1dB

• Ratio of cell 1 signal / AWGN, Î_or / I_oc ± 0.3dB

• Ratio of cell 2 signal / AWGN, Î_or / I_oc ± 0.6dB

• Ratio of cell 3 signal / AWGN, Ê_s / N_oc ± 0.6dB

This choice forms a minimum set, so the superposition principle can be applied if necessary.

For the test case, the signals of cell 2 and cell 3 are faded, so the uncertainties for Î_or / I_oc and Ê_s / N_oc need to be widened from the usual default value of ±0.3dB. The approach taken here aligns with the values used for demodulation test cases in Annex F.1.4 of TS 36.521-1:

Overall system uncertainty for fading conditions comprises two quantities:

1. Signal-to-noise ratio uncertainty ±0.3dB

2. Fading profile power uncertainty ±0.5dB

Items 1 and 2 are assumed to be uncorrelated so can be root sum squared:

Test System uncertainty = SQRT (Signal-to-noise ratio uncertainty² + Fading profile power uncertainty²) = SQRT (0.3² + 0.5²) = 0.58dB, round up to 0.6dB.

The absolute levels of I_oc and N_oc is specified as ± 0.7dB, similar to the uncertainty for other absolute power values such as RefSens. The value for E_c / I_or is specified as ± 0.1dB, similar to the uncertainty in UTRA TDD test specification TS 34.122.

5 Calculation of Test Tolerances

General approach

The general approach is given in the steps below:

1. Copy the originally specified key parameters from the core requirements

2. Where relevant, calculate derived parameters from the core requirements

3. Define uncertainties for a minimum set of parameters

4. Define controlled parameters (critical to the test verdict), calculate sensitivity factors and uncertainty

5. Determine which original or derived parameters to offset (apply Test Tolerances to) and by how much

6. Recalculate original or derived parameters including Test Tolerances

7. Check that the controlled parameters meet requirements to get the correct test verdict

Each step is explained below, and the calculations are given in the accompanying spreadsheet.

a) Original specified key parameters

The key parameters are copied from tables 8.6.5.3.4.2-2 and 8.6.5.3.4.2-3 in TS 34.122 v9.7.0. The key parameters are selected as the minimum set to define the cell power levels, and which are subject to a test system uncertainty which may affect the verdict of the test. The signalled parameters threshold T_{used_2b}/ T_used , T_{non used 2b} and T_{other_RAT} is also copied, although these are not subject to uncertainty.

The key parameters appear in section a) of the accompanying spreadsheet. The layout for Cell 1, Cell 2 and Cell 3 are similar to tables 8.6.5.3.4.2-2 and 8.6.5.3.4.2-3 in TS 34.122 v9.7.0, but the AWGN is given a separate set of columns for each frequency. This allows the spreadsheet calculations to be done in a consistent way.

b) Derived parameters

A number of derived parameters are calculated, using the base information in a). The reason for deriving each additional parameter is given in the “Comment” column of section b) in the accompanying spreadsheet.

In this test case at the start of T2, cell 2 becomes detectable and the UE is expected to detect and send an event triggered measurement report. The criterion is Event 2B: The estimated quality of serving cell is below than a certain threshold and an inter-frequency neighbour cell is above a certain threshold. The UE makes a measurement of cell 1 and cell 2, and compares RSCP values to the signalled threshold T_{used 2b} and T_{non used 2b}, so a further step is done to calculate the difference between RSCP and the thresholds:

• (Cell 1 RSCP – T_{used 2b})

• (Cell 2 RSCP – T_{non used 2b})

In this test case at the start of T2, cell 3 becomes detectable and the UE is expected to detect and send an event triggered measurement report. The criterion is Event 3A: The estimated quality of serving cell is below than a certain threshold and other system neighbour cell is above a certain threshold. The UE makes a measurement of cell 1 and cell 3, and compares RSCP and RSRP values to the signalled threshold T_used and T_{other_RAT}, so a further step is done to calculate the difference between RSCP/RSRP and their thresholds:

• (Cell 1 RSCP – T_used)

• (Cell 3 RSRP – T_{other_RAT})

c) Uncertainties

The choice of uncertainties is covered in section 4 of this document. They appear in section c) of the accompanying spreadsheet.

In addition the UE measurement accuracies need to be considered, it has some inaccuracy which could affect the test verdict.

For UTRAN TDD P-CCPCH RSCP measurement accuracy TS 25.123 clause 9.1.1.1.1.2 is given in the following extract:

9.1.1.1 P-CCPCH RSCP (TDD)

These measurements consider P-CCPCH RSCP measurements for TDD cells.

The measurement period for CELL_DCH and CELL_FACH state state can be found in section 8.

9.1.1.1.1 Absolute accuracy requirements

<<Some clauses skipped>>

9.1.1.1.1.2 1.28 Mcps TDD option

The accuracy requirements in table 9.1A are valid under the following conditions:

P-CCPCH RSCP  -102 dBm

P-CCPCH Ec/Io > -8 dB

DwPCH_Ec/Io > -5 dB

Table 9.1A: P-CCPCH_RSCP absolute accuracy

Parameter	Unit	Accuracy [dB]		Conditions
		Normal condition	Extreme condition	Io [dBm/ 1.28 MHz]
P-CCPCH_RSCP	dBm	 6	 9	-94...-70
	dBm	 8	 11	-70...-50

For E-UTRAN RSRP measurement accuracy TS 25.123 clause 9.1.1.5a refers to the inter-frequency requirements in TS 36.133, and the relevant clause is 9.1.3 as given in the following extract:

9.1.3 Inter-frequency RSRP Accuracy Requirements

9.1.3.1 Absolute RSRP Accuracy

The requirements for absolute accuracy of RSRP in this section apply to a cell that has different carrier frequency from the serving cell.

The accuracy requirements in Table 9.1.3.1-1 are valid under the following conditions:

Cell specific reference signals are transmitted either from one, two or four antenna ports.

Conditions defined in 36.101 Section 7.3 for reference sensitivity are fulfilled.

RSRP|dBm -127 dBm for Bands 1, 4, 6, 10, 11, 18, 19, 21, 33, 34, 35, 36, 37, 38, 39, 40,

RSRP|dBm -126 dBm for Bands 9,

RSRP|dBm -125 dBm for Bands 2, 5, 7,

RSRP|dBm -124 dBm for Bands 3, 8, 12, 13, 14, 17, 20.

Table 9.1.3.1-1: RSRP Inter frequency absolute accuracy

Parameter	Unit	Accuracy [dB]		Conditions1
		Normal condition	Extreme condition	Bands 1, 4, 6, 10, 11, 18, 19, 21, 33, 34, 35, 36, 37, 38, 39, 40	Bands 2, 5, 7	Bands 3, 8, 12, 13, 14, 17, 20	Band 9
				Io	Io	Io	Io
RSRP for Ês/Iot  -6 dB	dBm	6	9	-121dBm/15kHz … -70dBm/ BWChannel	-119dBm/15kHz … -70dBm/ BWChannel	-118dBm/15kHz … -70dBm/ BWChannel	-120dBm/15kHz … -70dBm/ BWChannel
RSRP for Ês/Iot  -6 dB	dBm	8	11	-70dBm/ BWChannel … -50dBm/ BWChannel	-70dBm/ BWChannel … -50dBm/ BWChannel	-70dBm/ BWChannel … -50dBm/ BWChannel	-70dBm/ BWChannel … -50dBm/ BWChannel
Note 1. Io is assumed to have constant EPRE across the bandwidth.

The ±8dB applies during T2 because the Cell 2 Io and Cell 3 Io are between -70dBm and -50dBm. Normal conditions are used for the test.

The ±6dB applies for cell 1 RSCP measurement because the Cell 1 Io is between -94dBm and -70dBm. Normal conditions are used for the test.

d) Controlled parameters critical to verdict

A diagram giving the Cell 1, Cell 2 and Cell 3 signal level during T1 and T2 is provided in section 3 of this document. It also includes the relevant thresholds. This is the most appropriate view to analyse the critical parameters for this test.

From 34.122 clause 8.6.5.3.

1. During T1, the UE has connected with Cell 1, and is required to measure serving Cell 1 and neighbour Cell 2 and Cell 3. Cell 2 and Cell 3 are powered off. The conditions are:

• Cell 1 must meet the P-CCPCH RSCP and DwPCH side conditions (level, Ec/Io) in TS 25.123 clause 9.1.1.1.1.2.

2. During T2, the UE is required to detect cell 2 and send an event 2B trigger report. The conditions are:

• The serving cell 1 signal is below T_{used 2b} with a margin of at leat 6dB.

• The neighbour cell 2 is good enough, expressed as RSCP > T_{non used 2b} with a margin of 8dB for measurement accuracy and 3dB margin for fading signal.

• Cell 1 and Cell 2 must meet the P-CCPCH RSCP and DwPCH side conditions (level, Ec/Io, Io) in TS 25.123 clause 9.1.1.1.1.2.

3. During T2, the UE is required to detect cell 3 and send an event 3A trigger report. The conditions are:

• The serving cell 1 signal is below T_used with a margin of at leat 6dB.

• The neighbour cell 3 is good enough, expressed as RSRP > T_{other_RAT} with a margin of 8dB for measurement accuracy and 3dB margin for fading signal.

• Cell 1 must meet the P-CCPCH RSCP and DwPCH side conditions (level, Ec/Io) in TS 25.123 clause 9.1.1.1.1.2.

• Cell 2 must meet the RSRP and SCH side conditions (level, Es/Iot, Io) in TS 36.133 clause 9.1.3.

The critical conditions are related to the 14 controlled parameters listed in section d) of the accompanying spreadsheet. They have been derived by study of the test case diagram and by careful reading of the relevant clauses in TS 36.133 and TS 25.123. The reason for each parameter being critical to the test verdict is given briefly in the “Comment” column of section d) in the accompanying spreadsheet. Information about the value to be achieved is given later in the “Comment” column of section g) in the spreadsheet.

Having identified the parameters critical to the test verdict which need to be controlled, we now need to consider how they are affected by the parameters which can be set by the test equipment. The sensitivity factors are the ratio (effect on a critical parameter y / a test equipment uncertainty x), and are usually in dB/dB. In this RRM test case there is a simple one-to-one relationship between the parameters that can be set by the test equipment, and their effect on parameters determining the test verdict. The sensitivity factors are therefore derived by inspection as one or zero.

For example, an error of 1dB in the absolute AWGN level N_oc would cause 1dB error in the Cell 3 RSRP, so the sensitivity factor is 1.000 during T2. It would also cause 1dB error in the derived parameter (Cell 3 RSRP - T_{other_RAT}), so the sensitivity factor is also 1.000 during T2. However the same error of 1dB in the absolute AWGN level N_oc would cause no change to Cell 3 E_s/I_ot, because all other powers are specified relative to N_oc, so the sensitivity factor is zero.

In some cases, the sensitivity factor is an intermediate value. For example, the Cell 1 I_or/I_oc has an effect on P-CCPCH_E_c/I_o which depends on ratios of the powers making up the total. In such cases a sensitivity factor value between 0 and 1 results. It is important to calculate these correctly to obtain the overall uncertainty.

For example,

• During T1 and T2, the effect of Cell 1 I_or/I_oc uncertainty on Cell 1 P-CCPCH_Ec/Io is x 0.285

These factors can also be derived intuitively, by considering the relative powers in step b). For example, I_oc forms 28.5% / (28.5%+71.5%) of the total power I_o, which is 0.285. A change in the Cell 1 I_or/I_oc has little effect on the ratio of P-CCPCH power to overall power, because the I_or makes up most of the overall power.

Having filled in the matrix of sensitivity factors, the accompanying spreadsheet calculates the overall uncertainty for each controlled parameter, taking into account the uncertainties and sensitivity factors for each parameter that can be set by the test equipment. This process follows the superposition principle. More details and explanation can be found in section 4 of TS 34.902. Uncertainties are calculated separately for T1 and T2.

The normal procedure of combining uncorrelated uncertainties root-sum-square is followed.

When the test system uncertainties and the UE reporting accuracies are combined, the (root-sum square of test system uncertainties) is added arithmetically to the UE reporting accuracies. If all the uncertainties were combined root-sum square, the resulting smaller test limits could case a conformant test system to fail a conformant UE, which would be unacceptable.

e) Determine parameters to offset

For Cell 1:

• During T2 (Cell 1 RSCP – T_used) is 6dB, just meeting the margin of at least 6dB measurement accuracy for AWGN. For maintain at least 6dB margin for UE measurement, The I_or/I_oc for Cell 1 is therefore decreased by the Cell 1 RSCP uncertainty.

• During T1 and T2, the I_oc of Cell 1 is unchanged.

For Cell 2:

• During T2 (Cell 2 RSCP – T_{other_RAT}) is 11dB, just meeting the margin of at least 8dB measurement accuracy plus 3dB margin for fading. The variations due to uncertainty will vary the margin for fading by less than 1dB, which is unlikely to affect the test case verdict significantly and is considered acceptable.

For Cell 3:

• The side conditions for cell 3 are fulfilled easily. The N_oc is unchanged.

• During T2 (Cell 3 RSRP – T_{other_RAT}) is 11dB, just meeting the margin of at least 8dB measurement accuracy plus 3dB margin for fading. The variations due to uncertainty will vary the margin for fading by less than 1dB, which is unlikely to affect the test case verdict significantly and is considered acceptable.

The check that all other controlled parameters meet their required range is done in step g). In theory it is possible for steps e) to g) to be iterative, or possibly even steps c) to g) to be iterative, but this test case can be done without such iteration.

f) Parameters modified by Test Tolerances

Based on the decision in e), the set of parameters in a) and b) is reproduced in section f) of the accompanying spreadsheet, but this time modified by the Test Tolerances (applied offsets).

Re-derived parameters are calculated using the same methods as were used in step b).

g) Check controlled parameters Min/Max

Using a format similar to that in step d), the nominal value of each controlled parameter is recalculated, as at least some will have changed from the original due to the application of the Test Tolerances in step f).

The minimum and maximum values, due to variability from uncertainties, of controlled parameters is then calculated and compared against the requirements (Required margin relative to threshold, E_s/I_ot range, RSRP level..). It is not necessary to calculate all parameters during each time interval T1 and T2, so a selection is made of those critical to the test verdict. The critical requirement for each parameter is given briefly in the “Comment” column of section g) in the accompanying spreadsheet. The cases closest to limit (in these test cases, all limits are one-sided) are identified by turquoise cells in the spreadsheet. If all requirements are met, then the exercise is complete.

It can be seen that with the uncertainty values and Test Tolerances proposed, all the requirements are met.