Technical data

Chapter 12 375
GSM and EDGE Analyzer
Metrics Provided by the GSM and EDGE Analyzer Measurement
GSM and EDGE Analyzer
the measured phase and the ideal phase of a TCH timeslot, at a single instant. The
GSM standard specifies the peak phase error not to exceed 20 degrees during the
useful part of the GSM burst.
RMS, Pk, and 95%tile Error Vector Magnitude
Error Vector Magnitude (EVM) is used as a measure of the quality of a signal, and
represents the difference, in both phase and magnitude, between a theoretically
perfect signal and the actual signal received.
Another measure of quality similar to EVM is Modulation Error Ratio (MER),
which is sometimes referred to as Carrier to Interference Ratio (C/I). For further
details on MER and C/I, see the section at the end of “Interpretation of GSM and
EDGE Analyzer Measurement Results” on page 376.
NOTE RMS EVM, Peak EVM, and 95%tile EVM measurements are only available if
Option 235 - EDGE Analyzer is installed
RMS EVM: This is the RMS of the EVM (Error Vector Magnitude), and is only
reported for 8PSK modulated signals, that is, for EDGE signals only and not for
GSM signals. EVM is measured and calculated over the useful part of the burst, and
is shown as a percentage.
The EVM metrics are only reported for EDGE signals with their 8PSK modulation.
EVM is not reported for GSM signals, with their GMSK modulation, since this
measurement of signal quality is reported as the Phase Error metric. For more details
on Phase Error measurements with GSM signals, see “RMS and Peak Phase Error”
on page 374.
Pk EVM: This is the Peak of the EVM (Error Vector Magnitude), and is only
reported for 8PSK modulated signals, that is, for EDGE signals only and not for
GSM signals. EVM is measured and calculated over the useful part of the burst, and
is shown as a percentage.
95%tile EVM: This is the 95th Percentile of the EVM (Error Vector Magnitude),
and is only reported for 8PSK modulated signals, that is, for EDGE signals only and
not for GSM signals. In other words, it is the EVM value below which 95% of all
measurements fall. EVM is measured and calculated over the useful part of the
burst, and is shown as a percentage.