Setting up a GSM/EDGE/EDGE Evolution Measurement

The GSM Global System for Mobile Communications: Originally developed as a pan-European standard for digital mobile telephony, GSM has become the world’s most widely used mobile system. It is used on the 900 MHz and 1800 MHz frequencies in Europe, Asia and Australia, and the 1900 MHz frequency in North America and Latin America./EDGE Enhanced Data for Global Evolution: A technology that gives GSMA and TDMA similar capacity to handle services for the third generation of mobile telephony. EDGE was developed to enable the transmission of large amounts of data at a high speed, 384 kilobits per second. (It increases available time slots and data rates over existing wireless networks.)/EDGE Evolution demodulator can automatically demodulate GSM, EDGE, or EDGE Evo signals once the signal is connected to the VSA.

This topic provides information on connecting and successfully demodulating a signal using the GSM/EDGE/EDGE Evolution demodulator. A typical measurement includes the following measurement setup process (each step is discussed in the following text).

Connect your signal to the VSA
Configure measurement setup and input parameters
1. Set the Center Frequency
2. Set the Frequency Span
3. Configure the Input Range
4. Configure Triggering
5. Verify input signal and initial parameter settings
Configure the GSM/EDGE/EDGE Evolution demodulator
1. Select the GSM/EDGE/EDGE Evolution demodulator
2. Open the GSM/EDGE/EDGE Evolution Demod Properties dialog box
3. Preset to Standard
Setup required signal parameters
1. Set Burst Type
2. Set HSR Pulse Shape Filter for high symbol rate bursts
3. Set Mirror Frequency Spectrum
4. Select Also Auto-detect AQPSK and AQPSK Alpha when necessary
Configure optional demodulation parameters
Run the measurement

Measurement Setup Procedure

Connect your Signal to the VSA
- Single channel connection
  
  Connect the signal to the Channel 1 on the measurement hardware.
  
  Click Input > Channels and select 1 Channel. Multiple channels can be selected but the demodulator will only use Channel 1.
- I+jQ connection
  
  Connect the I and Q signals to the measurement hardware. To configure the VSA, select Input > Channels > I + jQ.
  Notes for I+jQ input:
  - Selecting an I+jQ configuration enables DC coupling.
  - Use User Correction to correct for any offset or gain imbalance between the I and Q signals.
  - Range is set independently for the I and Q inputs, but can be coupled by selecting the Couple Paired Channels parameter.
- Recorded signal
  
  Recall the recorded signal by selecting File > Recall > Recall Recording
  
  The center frequency and input range will be set by the recording.
For more information about your specific measurement hardware, see the Measurement Hardware book.
Configure Measurement Setup and Input Parameters
1. Set the Center Frequency
  
  By default, the 89600 VSA's center frequency must be set to within approximately 400 kHz kiloHertz: A radio frequency measurement (one kilohertz = one thousand cycles per second). of the signal's carrier frequency for the demodulator to lock to the signal. However, for best EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. performance, set the center frequency within 200 kHz of the signal's carrier frequency.
2. Set the Frequency Span (optional)
  
  The span can be set at this point to be able to verify your signal in step e but Preset to Standard (performed later in this procedure) will set the span to 1 Mhz automatically.
  
  See the Span topic for details on setting the frequency span.
3. Configure the Input Range
  
  The input range must be set correctly to obtain accurate measurements. Input ranges that are too low overload the VSA's ADC Analog-to-Digital Converter. Input ranges that are too high increase noise, which increases errors reported in error summary data, such as EVM.
4. Set up triggering
  
  The default triggering mode is set to "FreeRun". However, a different type of triggering can be configured using the parameters on the Input > Trigger tab.
5. Verify the input signal and initial parameter settings
  
  View the signal in the frequency domain (Spectrum trace) to verify the parameters set.
Configure the GSM/EDGE/EDGE Evolution demodulator
1. Click MeasSetup > Measurement Type > GSM/EDGE/EDGE Evolution to enable the GSM/EDGE/EDGE Evolution demodulator.
2. Click MeasSetup > GSM/EDGE/EDGE Evolution Demod Properties to display the properties and measurement parameters dialog box.
3. Click Preset to Standard to set demodulation parameters to default values.
Try restarting the measurement (see Step 6 below) to see whether your signal will demodulate with the default values.
Setup required signal parameters

These parameters are not autodetected and will need to be set if the default values are not correct for your signal.
1. Specify Burst Type.
2. Set HSR Pulse Shape Filter for high symbol rate signals.
3. Set Mirror Frequency Spectrum if necessary
  
  The GSM/EDGE/EDGE Evolution demodulator provides a feature that configures the demodulator to conjugate the complex time-domain waveform. This has the effect of flipping the spectrum around the VSA's center frequency.
4. Select Also Auto-detect AQPSK and set AQPSK Alpha when demodulating bursts containing AQPSK modulation.
Configure optional demodulation parameters
1. Set the Search Length
  
  Search Length determines the signal capture length to use for burst search. Set Search Length to capture the desired data.
2. Set the Timeslot to demodulate
3. Choose a different way of synchronizing to the burst using Burst Sync Mode
4. Set Modulation Scheme to search for a specific modulation scheme
5. Enable the Multi-carrier Filter for signals with adjacent channels
6. Specify custom symbol rates using Normal Symbol Rate and High Symbol Rate
7. Specify whether to undo filter effects and derotate the symbol points before displaying them using IQ Constellation Type
8. Disable Wide Frequency Lock Range to increase measurement speed
9. Configure whether the signal displayed in the IQ Meas Time trace is to be compensated for Amplitude Droop.
Run the Measurement

Press the Restart ( ) button to restart the measurement.

For help when your signal is not demodulating correctly, see the Troubleshooting topic.