Waveform Quality Measurement Description

How is a Waveform Quality Measurement Made?

3GPP TS 34.121 s5.13 states "The Error Vector Magnitude is a measure of the difference between the reference waveform and the measured waveform. This difference is called the error vector. Both waveforms pass through a matched Root Raised Cosine filter with bandwidth 3,84 MHz and roll-off a = 0,22. Both waveforms are then further modified by selecting the frequency, absolute phase, absolute amplitude and chip clock timing so as to minimise the error vector. The EVM result is defined as the square root of the ratio of the mean error vector power to the mean reference power expressed as a %."

The waveform quality measurement in the test set compares the received signal's IQ modulation characteristics to an ideal signal, as defined in 3GPP TS 34.121 s5.13 and annex B.

Measurement Interval in Non-HSDPA Mode

When on a non-HSDPA connection, you must set Trigger Source to any value other than HS-DPCCH . When operating in this mode, the measurement is made during one timeslot (666.7 us). You can choose in which timeslot of the W-CDMA frame the measurement is performed using the Timeslot setting. You can also choose whether to include or exclude the 25 us transient periods on the slot boundaries using the Transient Period setting.

Measurement Interval Duration and Placement for Non-HSDPA

Measurement Interval in HSDPA Mode

This section is only applicable to the lab application or feature-licensed test application .

To measure waveform quality on an HSDPA connection, you must set Trigger Source to HS-DPCCH . When Trigger Source is set to HS-DPCCH, you can specify the measurement interval and its placement within any of the 6 HSDPA subframes.

1. Use the HS-DPCCH Trigger Subframe Alignment setting to choose in which 2 ms subframe (0 to 5) you want to place the measurement interval.
2. Use the HS-DPCCH Trigger Slot Alignment setting to specify in which slot within the subframe you want to place the measurement interval ( AckNack = the first slot of the subframe, CQI1 = the second slot of the subframe and CQI2 = the third slot of the subframe).
3. Set the duration of the measurement interval using the HS-DPCCH Measurement Interval setting. Note that the sum of HS-DPCCH Trigger Subslot Alignment and HS-DPCCH Measurement Interval cannot exceed 1.0 slot.
4. Use the HS-DPCCH Trigger Subslot Alignment setting to specify where you want to place the measurement interval within the slot. You can place the measurement interval at the slot boundary, 0.1 slot (66.7 us) after the slot boundary, 0.2 slot (133.3 us) after the slot boundary... up to 0.5 slot (333.3 us) after the slot boundary. Note, however, that the sum of HS-DPCCH Trigger Subslot Alignment and HS-DPCCH Measurement Interval cannot exceed 1.0 slot. If you wish to place the measurement interval after the slot boundary using the HS-DPCCH Trigger Subslot Alignment setting, you must first decrease the HS-DPCCH Measurement Interval setting appropriately.
5. You can choose to shorten the measurement interval so as to exclude the 25 us (96 chip) transient periods at the start and end of the measurement interval using the Transient Period setting. For example, if you set HS-DPCCH Measurement Interval to 0.5 slot (333.3 us or 1280 chips) and set Transient Period to Exclude , the measurement is performed over 283.3 us (or 1088 chips).

Measurement Interval Duration and Placement for HSDPA

Waveform Quality Measurement Parameters

• Multi-Measurement Count: see Statistical Measurement Results .
• Timeslot

  When Trigger Source is set to any value other than HS-DPCCH , you can specify which timeslot of the W-CDMA frame (0 to 14) is evaluated by the waveform quality measurement. See Measurement Interval in Non-HSDPA Mode .

• Transient Period

  When Transient Period is set to Include and Trigger Source is set to any value other than HS-DPCCH , the measurement is performed over one timeslot. When Transient Period is set to Include and Trigger Source is set to HS-DPCCH , the measurement is performed over the interval specified by the HS-DPCCH Measurement Interval setting.

  When Transient Period is set to Exclude , the 25 us at the start of the measurement interval and the 25 us at the end of the measurement interval are excluded from the measurement. Thus, when Trigger Source is set to any value other than HS-DPCCH , the measurement is performed over 666.7 us - 50 us = 616.7 us. When Trigger Source is set to HS-DPCCH , the measurement is performed over an interval equal to HS-DPCCH Measurement Interval less 25 us from each end (see Measurement Interval in HSDPA Mode ).

• Trigger Arm: see Trigger Arm (Single or Continuous) Description .
• Trigger Source

  Triggering choices are immediate, protocol, external, auto, and HS-DPCCH ( lab application or feature-licensed test application only ). See Trigger Source Description for more information.

  Auto triggering is the default choice. In most cases, auto triggering provides the optimum measurement triggering condition for the waveform quality measurement. For example, if the UE is synchronized to the test set, auto triggering causes protocol triggering to be used. Auto triggering causes immediate triggering is used if the UE is not synchronized. When immediate triggering is used, the measurement result returned for timing error is always NAN (Not a Number) because it is not possible to evaluate a timing error in this measurement situation.

• Measurement Timeout: see Measurement Timeouts .

HSDPA Measurement Parameters

This section is only applicable to the lab application or feature-licensed test application .

These settings are only applicable when Trigger Source = HS-DPCCH .

See Measurement Interval in HSDPA Mode for more information about using these parameters to specify the duration and placement of the measurement interval.

• HS-DPCCH Trigger Subframe Alignment

  Selects which 2 ms subframe (0 to 5) contains the measurement interval.

• HS-DPCCH Trigger Slot Alignment

  Selects which slot in the 2 ms subframe contains the measurement interval ( AckNack = the first slot in the subframe, CQI1 = the second slot in the subframe and CQI2 = the third slot in the subframe).

• HS-DPCCH Measurement Interval

  See Measurement Interval in HSDPA Mode .

  Note, the sum of HS-DPCCH Trigger Subslot Alignment and HS-DPCCH Measurement Interval cannot exceed 1.0 slot.

• HS-DPCCH Trigger Subslot Alignment

  Selects where to place the measurement interval within the slot, in 0.1 slot (66.7 us) increments. This is useful because depending upon the Current DPCH Offset , the uplink DPCH and HS-DPCCH can be offset in time by increments of 0.1 slot (see HS-DPCCH/DPCCH Alignment vs. DPCH Frame Offset ).

  Note, the sum of HS-DPCCH Trigger Subslot Alignment and HS-DPCCH Measurement Interval cannot exceed 1.0 slot.

• 34.121 5.13.1A Measurement Configurations

  These settings should be used in conjunction with the 34.121 Preset Call Configurations . All four of the 5.13.1A measurement configurations set the following: Transient Period = Exclude , HS-DPCCH Measurement Interval = 0.5 slot and Trigger Source = HS-DPCCH . They also set the trigger alignment settings so as to capture the regions indicated in the diagram below.

  

  	Measurement Point	HS-DPCCH Trigger Subframe Alignment	HS-DPCCH Trigger Slot Alignment	HS-DPCCH Trigger Subslot Alignment
  34.121 5.13.1A Low of Low-High Transition	1	subframe 5	CQI2	0.5 slot
  34.121 5.13.1A High of Low-High Transition	2	subframe 0	AckNack	0.0 slot
  34.121 5.13.1A High of High-Low Transition	3	subframe 3	AckNack	0.5 slot
  34.121 5.13.1A Low of High-Low Transition	4	subframe 3	CQI1	0.0 slot

  You can then ensure that your UE conforms to 5.13.1A (see Measuring 3GPP TS 34.121 v7.5.0 s5.13.1A Error Vector Magnitude (EVM) with HS-DPCCH ).

Waveform Quality Measurement Results

• EVM: Error Vector Magnitude (in %)
• Peak EVM (maximum chip EVM, in %) - available through GPIB query only.
• Frequency Error (in Hz)
• Origin Offset (in dB)
• Phase Error (in degrees)
• Magnitude Error (in %)
• Time Error (in chips)

  The time error is determined as a result of minimizing the error vector between the measured and ideal signals. It is a measure of the timing error of the UE's transmission relative to the frame clock. The requirements for UE timing are defined in 3GPP TS 25.133 s7.1, which states "The uplink DPCCH/DPDCH frame transmission takes place approximately T ₀ chips after the reception of the first detected path (in time) of the corresponding downlink DPCCH/DPDCH or F-DPCH frame, from the reference cell". The time error reported by the test set does not include T ₀ (defined to be 1024 chips by 3GPP TS 25.211 s7.6.3). The time error is the error beyond 1024 chips.

• PCDE

  Peak Code Domain Error (in dB) and the code channel at which it occurs (C _{ch,Spreading Factor,Code Number} ).

• Beta _c , Beta _d1 , Beta _d2 , Beta _d3 , Beta _d4 , Beta _d5 , Beta _d6 , Beta _hsacknak , Beta _hscqi

  Only Beta _c (DPCCH) and Beta _d1 (DPDCH 1) provide results (other than NaN) while on a non-HSDPA connection. Beta _d2-6 are reserved for future use. See Uplink DPCH Bc/Bd Control for more information on Beta _c and Beta _d .

  Beta _hsacknak and Beta _hscqi only provide results (other than NaN) when on an HSDPA connection ( lab application or feature-licensed test application only ). Beta _hsacknak represents the value of Beta _hs when measuring the Ack/Nack portion of the subframe. Beta _hscqi represents the value of Beta _hs when measuring the CQI portion of the subframe. Thus, when HS-DPCCH Trigger Slot Alignment is set to AckNack , a valid result is returned for Beta _hsacknak , NaN is returned for Beta _hscqi . Likewise, when HS-DPCCH Trigger Slot Alignment is set to CQI1 or CQI2 , a valid result is returned for Beta _hscqi , NaN is returned for Beta _hsacknak . See HS-DPCCH Gain Settings for more information on Beta _hs .

  The beta results are available through GPIB query only.

• IQ Gain Imbalance and IQ Phase Imbalance (in dB) - available through GPIB query only.

  IQ gain imbalance and IQ phase imbalance measurements are determined by comparing the received signal's IQ modulation characteristics with an ideal signal (IQ gain imbalance, IQ phase imbalance and Origin Offset are solved for using the parameter estimator described in Estimation of Amplitude Imbalance, Phase Imbalance, and Origin Offset of a Complex Signal Relative to an Ideal Reference by R. A. Birgenheier, Jan. 4, 2000).

Waveform Quality Input Signal Requirements

• For this measurement the test set's receiver uses auto-ranging to adjust for the level of the signal being measured; therefore the expected signal level does not need to be specified during measurement setup. However, it is recommended that Expected Power be configured to match the actual signal level expected to ensure the auto-ranging procedure executes as quickly as possible.
• The frequency of the signal being measured must be in the range of 800 MHz to 1000 MHz, 1700 MHz to 1990 MHz, or 2480 MHz to 2580 MHz.
• The level into the test set's RF IN/OUT connector must be in the range of -25 dBm to +28 dBm, in a 3.84 MHz bandwidth.
• Maximum measurable EVM = 35%
• Maximum measurable frequency error = ± 1 kHz
• Maximum measurable timing error = +/- 50 chips

Waveform Quality Measurement Calibration

This measurement should be calibrated using the Calibrate Measurements function ( CALibration:MEASurements? ) when the temperature has changed by ± 10° C or more since the last calibration. If this situation exists, the integrity indicator value becomes 19 and a message is displayed indicating "Uncalibrated Due to Temperature".

Related Topics

• Manual Operation: How Do I Make a Waveform Quality Measurement?
• Programming a Waveform Quality Measurement
• Waveform Quality Troubleshooting
• What 3GPP W-CDMA/HSPA Conformance Tests Are Supported?
• Triggering of Measurements
• Statistical Measurement Results
• Integrity Indicator