User`s guide

2-9
GPIB Tutorial and Examples
Example C - Making Measurements
Receiver Sensitivity Test
Bit Error Ratio (BER) is the primary measure of GSM receiver sensitivity. For a hand-
held mobile, the residual type II BER should be less than 2.4% at -102dBm. For most
mobile testing, the downlink power will be maintained at a relatively high level of around
-80dBm. This level is dropped to -102dBm to perform the BER test, then increased again
to -80dBm once the test is complete. When the mobile’s receiver input level drops from
-80 to -102dBm, its receiver AGC compensates by increasing gain. The AGC time
constant varies from mobile to mobile. It can take several seconds for the receiver to
adjust to the new power level and be ready for BER testing. If the level change is large
and followed by a channel assignment, the mobile will often drop the call because its
receiver is not able to decode the FACCH while adjusting to the reduced input power.
Select GPIB commands from "GPIB Commands Used in Exercises" to extend your
program as follows:
❒ Select single trigger mode for DSP measurements
❒ Select single trigger mode for BER measurements
❒ Establish call as in exercise A
❒ Perform TX peak power test on channels 1, 63, 124, levels 5 to 15 with code from
exercise B and C
❒ Perform DSP measurements with code from exercise C
❒ Display the bit error test screen
❒ Reduce the RF Generator power to -102dBm
❒ Wait 2 seconds for the mobile’s AGC to settle
❒ Set up a loop to count through three ARFCN: 1, 63, 124
❒ Command the phone to the new ARFCN
❒ Trigger a BER measurement
❒ Query the BER
❒ Repeat for the next ARFCN
❒ Increase the RF Generator power to -80dBm
❒ Return to the Cell Control screen
❒ End call as in exercise A