How do I make Modulation Accuracy Measurements?

Last updated: December 2, 2008

This section is only applicable to EGPRS.

Measuring 3GPP TS 51.010 Section 13.17.1 Modulation Accuracy

The following topics are discussed in this section:

After obtaining the measurement results, verify that they meet the conformance requirements defined in 3GPP 51.010 section 13.17.1.

A. Test Set Configuration

Setup parameters for this measurement are assumed to be set to their default (Full preset) values unless otherwise stated. This procedure also assumes that the BCH parameter for band is set up correctly for your mobile station and that the appropriate RF IN/OUT Amplitude Offsets have been set to offset loss between the mobile station and the test set.

Press the CALL SETUP key.
Press Operating Mode ( F1 ) and select Active Cell (EGPRS) .
Press the Data Conn Type ( F2 ) key, and select ETSI Type A. (See Modulation Accuracy Measurement Description for other connection types that can be used with this measurement.)
Select PDTCH Parameters ( F9 ) from the Call Parms menu.
Select Modulation Coding Scheme ( F11 ) from the PDTCH Parms menu. The Modulation Coding Scheme popup menu appears.
Select Uplink Modulation Coding Scheme and select one of the following modulation coding schemes: MCS-5 (8PSK), MCS-6 (8PSK), MCS-7 (8PSK), MCS-8 (8PSK), or MCS-9 (8PSK) .

NOTE
The Modulation Accuracy measurement is only useful for measuring 8PSK signals, therefore, it is necessary to select a modulation and coding scheme using 8PSK modulation for the measured signal.
Press the Close Menu ( F6 ) key.

B. Start a Data Connection

Connect the mobile.
Turn the mobile on and wait for Attached in the Active Cell field.

NOTE
For mobiles that don't perform an EGPRS attach automatically, set the mobile to data mode. For example, your mobile station may have a connectivity setting for GPRS that allows you to specify whether you are always on-line or only use GPRS when it is needed.
Press the Start Data Connection ( F3 ) key and watch for the Active Cell field changing to Transferring .

C. Start the Measurement

Press the Measurement selection key.
Select the EGPRS Modulation Accuracy measurement.
The measurement results for the default measurement setup are displayed.

D. Setup the Measurement

Press the Modulation Accuracy Setup ( F1 ) key.
You can set the measurement parameters as needed for your measurement, for example, statistical measurement results can be turned on by selecting the Multi-Measurement Count parameter and changing to the value to something greater than zero. For this example, enter 5 .
Press the Close Menu ( F6 ) key.
The measurement results now include statistical results.

E. How to view IQ Imbalance Results

Press the Modulation Accuracy Setup ( F1 ) key.
To view results for IQ Imbalance, select IQ Imbalance Calculate State and select On .
Press the Close Menu ( F6 ) key.
The measurement results now include IQ Imbalance results.

F. View the Modulation Accuracy Graphical Results

The procedures below all start from the Control menu. (This is the menu on the left in the previous figure.)

General

Press the Change View ( F2 ) key.
Press the EVM Demod Symbols ( F2 ) key, Magnitude Error Phase Error ( F3 ) key, or the Sample EVM Histogram ( F5 ) key to display their respective measurement graphs.
Use the Return ( F6 ) key to return to the Control menu.
You can access the other graphs from any one graph's display by pressing Next Graph ( F5 ) until the graph you want is displayed.

View the EVM and Demodulated Symbols Graph

Press the Change View ( F2 ) key.
Press the EVM Demod Symbols ( F2 ) key to display the graphical EVM and Demod Symbols measurement results. You can change the EVM % per division by pressing Axis Control ( F1 ) and then %/ div ( F3 )and entering the desired value. For the following example, 1.00 % was the value used.

Press Return ( F6 ) to return to Graph Control . You can also turn on markers to see the Demodulated symbols, EVM, Magnitude Error, and Phase error for individual symbols. Also, notice that the previous figure shows the demodulated symbols in octal. You can change the display to show the demodulated symbol values in binary by pressing the Demod Symbols ( F4 ) key and selecting Binary .
Use the Return ( F6 ) key to return to the Control menu.

View the Magnitude and Phase Error Graphs

Press the Change View ( F2 ) key.
Press the Magnitude Error Phase Error ( F3 ) key to display the graphical Magnitude and Phase Error measurement results. The graphs display error versus symbol position. You can alter the error axis of the magnitude error graph by pressing Axis Control ( F1 ) and then %/div ( F3 ) and entering the desired value. For the following example, 5.00 % was the value used. The phase error graph's error axis is altered by pressing deg/div ( F4 ).

Press Return ( F6 ) to return to Graph Control . You can also turn on markers to see the Magnitude Error and Phase error for individual symbols. Also, notice that the previous figure shows the demodulated symbols in octal. You can change the display to show the demodulated symbol values in binary by pressing the Demod Symbols ( F4 ) key and selecting Binary .
Use the Return ( F6 ) key to return to the Control menu.

View the Sample EVM Histogram

Press the Change View ( F2 ) key.
Press the Sample EVM Histogram ( F5 ) key to display the sample EVM histogram and the 95th Percentile EVM measurement results. You can also turn on markers to measure the probability for a particular range of EVM percentages.
Use the Return ( F6 ) key to return to the Control menu.

Changing the Sample EVM axis

You can change the Maximum Sample EVM displayed on the graph to increase the resolution of the histogram.

Press Return ( F6 ).
Press Return ( F6 ) again.
Press Modulation Accuracy Setup ( F1 ).
Select Histogram Maximum Sample EVM and select from the list. The proceeding figure used the 100% setting. The following figure uses the 10% setting. The vertical orange line is the 95th percentile EVM. The 10.00+ displayed as the limit of the x axis indicates that there were samples with an EVM that exceeded 10 and are not displayed on the graph.
Press Change View (F2).
Press Sample EVM Histogram (F5). You can now use the markers.
Use the Return ( F6 ) key to return to the Control menu.