Noise-Limited OTA Performance in Transmit Diversity Mode
R&S
®
AMS32-K31
20
User Manual 1175.6678.02 ─ 01
Normalization of sensitivity threshold levels
The levels in the CDF, Avg. Throughput, and CCDF graphs and tables are expressed in
units of dBm/15 kHz, which corresponds to the normalization of the RS EPRE values
(see
"Downlink levels for MIMO sensitivity tests"
on page 11). 15 kHz is the fixed sub-
carrier spacing of the LTE signal.
Multiplying the RS EPRE with the number of subcarriers per band yields the "full cell
bandwidth power" values. If desired, R&S AMS32 can convert the levels in the CDF
graphs and tables to full cell bandwidth powers (click "Extras > Options > OTA
Options" and check "Correct LTE TIS power level for EPRE offset" in the "Test Control"
tab of the dialog opened). You can also re-calculate the CDF results of an exisiting test
in order to convert the levels ("Test > OTA MIMO Evaluation > (C)CDF EValuation... >
Do Evaluation").
The number of subcarriers depends of the cell bandwidth. E.g. for a 10 MHz band, the
number is 600, so the full bandwidth powers are 10 * log(600) dB = 27.78 dB above the
RS EPRE values
In addition to the sensitivity thresholds measured at each point, which are saved to the
"Result Tables" of the test, R&S AMS32 logs the BLER and throughput values measured
at every downlink level during the test. The data are logged to a file
LteMimoData.csv
in the test’s
\System
sub-folder. The layout of this
*.csv
file is as
shown below.
Fig. 2-7: LteMimoData.csv file opened in Microsoft
®
Excel
Result Evaluation and Reporting
