R&S
®
CMW 500 GSM Applications
GSM TX Measurements
Operating Manual 1202.3986.32 – 03 216
The energy that spills outside the designated radio channel increases the interference
with adjacent channels and decreases the system capacity. According to the
conformance test specification 3GPP TS 51.010-1, the amount of unwanted off-carrier
energy is assessed by the spectrum due to modulation and the spectrum due to
switching (the "ACP modulation" and "ACP switching" results of the multi-evaluation
measurement). The ACP limits are defined in the configuration menu.
The GSM limit specifications are equal for GMSK and 8PSK modulation, however, the
limits can be chosen independently on the R&S CMW 500.
ACP Modulation Limits
The limit lines for the spectrum due to modulation depend on the GSM band, the
frequency, and (for frequencies that differ from the carrier frequency by more than 400
kHz) on the output power of the mobile station. The following values apply up to a
frequency offset of 1.8 MHz:
GSM400/GT800/850/900 Relative power at
MS output power
GSM1800/1900 Relative power at MS
output power
Frequency offset /
[MHz]
e 33 dBm (in dBc) d 39 dBm (in dBc) e 24 dBm (in dBc) d 36 dBm (in dBc)
0.1 +0.5 +0.5 +0.5 +0.5
0.2 –30 –30 –30 –30
0.25 –33 –33 –33 –33
0.4 –60 (GMSK mod.)
–54 (8PSK mod.)
–60 –60 (GMSK mod.)
–54/–60 (8PSK
mod.)
*)
–60
d 0.6, e 1.8 –60 –66 –60 –60
*) For equipment supporting 8PSK, the limit of –54 dBc applies to MS output powers
up to +30 dBm, –60 dBm to MS output powers above +30 dBm.
In the frequency range above 400 kHz from the carrier and for output powers between
33 dBm and 39 dBm (GSM400/GT800/850/900), the limit depends linearly on the
output power. The resulting spectral mask for GMSK modulation is shown below.
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