Technical data

374 Chapter 12
GSM and EDGE Analyzer
Metrics Provided by the GSM and EDGE Analyzer Measurement
GSM and EDGE Analyzer
Mod Type
Modulation Type can be either GMSK or 8PSK. GSM signals use GMSK
modulation, and EDGE signals use 8PSK modulation.
TS Pwr (Timeslot Power)
The average power of the highest power timeslot in the acquired frame. This is the
absolute power level and displayed in both dBm and microWatts.
OBW (Occupied Bandwidth)
This is the 99% power bandwidth of the centered 500 kHz span at the channel
frequency. In other words, the total power of 500 kHz span centered at the channel
frequency is computed, then the bandwidth that contains 99% of the total power is
returned as the occupied bandwidth.
I/Q Offset
I/Q origin offset is a value in dB of the I and Q error (magnitude squared) offset
from the origin. It indicates the magnitude of the carrier feedthrough signal. When
there is no carrier feedthrough, I/Q Offset is zero.
RMS and Peak Phase Error
Phase error is the fundamental measure of modulation quality in GSM and EDGE
systems. Since GSM and EDGE systems use relative phase to transmit information,
the phase accuracy of the GSM or EDGE transmission is critical to the system’s
performance, and ultimately to its effective range.
The Phase Error metrics are only reported for GSM signals with their GMSK
modulation. Phase Error is not reported for EDGE signals, with their 8PSK
modulation, since this measurement of signal quality is reported as part of the Error
Vector Magnitude metric. For more details on Error Vector Magnitude
measurements with EDGE signals, see “RMS, Pk, and 95%tile Error Vector
Magnitude” on page 375.
The phase error is computed by measuring the test signal and computing the
difference between the phase of the transmitted signal and the phase of a
theoretically perfect signal.
RMS Phase Error: This is the RMS of the phase error (in degrees) between the
measured phase and the ideal phase of a TCH timeslot. The GSM standard specifies
the RMS phase error not to exceed 5 degrees during the useful part of the GSM
burst.
Pk Phase Error: Peak phase error is the maximum phase error (in degrees) between