WiMAX, WiBro Measurements (Options K92/K93) R&S FSL
1300.2519.12 2.152 E-11
IQ Impairments
IQ imbalance in an OFDM transmitter or receiver leads to an interference of the symbols
kl
a
,
with the
symbols
kl
a
,
. In case of subchannelization, the used sub carriers are always situated in such a way, that
0
,
=
kl
a , if 0
,
&
kl
a . T
here is no impact of IQ imbalance on the actually allocated carriers of a
subchannelization transmission. The effect can only be seen on the unallocated carriers and yields a
pattern around the origin of the constellation diagram.
Fig. 2-92 Constellation vs Symbol
The unsymmetrical allocation of the sub carriers prevents a measurement of gain imbalance and
quadrature error in case of subchannelization. The influence of the occupied carriers
kl
a
,
on the
unoccupied carriers
kl
a
,
could be measured, but there is no possibility to distinguish them from an
unknown channel coefficient.
RSSI
See [6] section "8.3.9.2 RSSI mean and standard deviation''. The Received Signal Strength Indication
[RSSI] is basically the preamble power. The result summary provides the RSSI statistics according to
the standard. A possible method to compute RSSI[k] at the antenna connector is given in [6] equation
(87). RSSI[k] is the RSSI measurement based on the k–th signal/preamble.
The RSSI statistics of the result summary is calculated as follows:
1. RSSI row:
Statistic {min, mean, max} of the R[k]=RSSI[k].
The mean value is
dBmRSSI
µ
ˆ
[k] according to [6] formula (89).
2. RSSI Standard Deviation row:
dBRSSI
/
ˆ
according to [6] formula (91).
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