Rohde & Schwarz CMW 500 - GSM Programming

R&S
®
CMW 500 GSM Applications
GSM TX Measurements
Operating Manual 1202.3986.32 – 03 221
frames.
The periodic access bursts that the mobile may use during packet data
connections in order to transmit its CTRK_ACK messages.
If no filter condition is specified ("Modulation View: Any"), the R&S CMW 500
measures any burst sequence. Varying burst types during the measurement will cause
inconsistent statistical results.
Measurement Principle
Capturing a particular burst sequence requires two steps:
1. The R&S CMW 500 determines the frame structure of the measured signal (slot
nos. 0 to 7), most conveniently using a gap or pattern trigger. See "Detecting
GSM Multislot Frames" on page 219. After this step, the GSM multi-evaluation
measurement is frame-aligned; it is continued irrespective of the actual burst
pattern in the measured frames.
2. Use the "Modulation View" settings to filter frames with a definite burst pattern,
rejecting all other frames.
Trigger and "Modulation View" settings
The acquisition trigger and modulation view settings are completely independent of
each other. It is possible to specify the same burst pattern for the pattern trigger and
the modulation view. However, it is also possible to use different settings, e.g. in order
to pi
n down the frame boundary using the predominant burst pattern and then measure
a different, occasionally transmitted burst pattern.
Example: Two EDGE bursts and one access burst
The mobile transmits two EDGE bursts in slots 0 and 1, followed by a GMSK-
modulated burst in slot 2. Suppose that the GMSK-modulated burst is occasionally
replaced by an access burst.
To detect the frame boundary and measure the access burst frames, proceed as
follows:
1. Feed the GSM uplink signal to the input connector and perform the necessary
analyzer settings.
2. Open the "GSM Measurement – Multi Evaluation Configuration" menu.
3. Select "Trigger > Trigger Source: Acquisition (Internal)", "Trigger > Acquisition >
Mode: Pattern", "Trigger > Acquisition > Pattern: EDGE EDGE GMSK OFF OFF
OFF OFF OFF".
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