LTE Signaling
R&S
®
CMW-KM5xx/-KS5xx
64
User Manual 1173.9628.02 ─ 16
If you want to set up a downlink signal with a specific CQI index value, use a "CQI"
scheduling type.
When you start the measurement, the R&S
CMW sends data to the UE via PDSCH
subframes and requests the UE to confirm the correct reception. The UE confirms
each received subframe with an ACK or NACK via the PUSCH. The R&S
CMW calcu-
lates the DL BLER from the received ACKs and NACKs. It determines the CQI, PMI
and RI results from the corresponding reported values. For the uplink, the R&S
CMW
performs a CRC check and calculates the UL BLER from the results of the check
For transmission schemes using several downlink streams, the ACKs, NACKs and CQI
indices reported for the streams are evaluated separately.
Note: As the transmit time interval for LTE equals one subframe, a subframe corre-
sponds to one transport block.
It is possible to insert block errors into the downlink data (send wrong CRC value). For
configuration see
"Downlink MAC Error Insertion"
Active neighbor cell measurements cause an increased number of NACKs. So it is rec-
ommended to disable neighbor cell measurements for BLER evaluation, see
.
Reduced PDCCH resources may also result in an increased number of NACKs. So it is
recommended to disable "Reduced PDCCH", see
For configuration of CQI, PMI and RI reporting, see
.
For configuration of DL HARQ settings, see
.
Confidence BLER measurements
In a normal BLER measurement, typically a fixed number of subframes is transmitted,
leading to a fixed test time. The idea behind confidence BLER measurements is to
apply probability theory and predict a range for the BLER at an early stage of the mea-
surement. The measurement is stopped if the probability of the UE to pass or fail the
receiver quality test is large enough (early pass or early fail decision).
Confidence BLER measurements can reduce test times considerably, especially if the
BLER of a receiver is very low or very high. They are specified in Annex G of 3GPP TS
36.521 as "Statistical Testing". Option R&S CMW-KS510 is required for confidence
BLER measurements.
To perform a confidence BLER measurement, configure especially the following mea-
surement settings (see also
●
Set "Stop Condition" to "Confidence Level"
●
Select the "Error Ratio Calculation" according to the test case
●
Configure the "Minimum Test Time" according to the test case
●
Select a "Limit Error Rate"
Depending on this selection, the pass/fail decision is made according to the rules
specified in 3GPP TS 36.521 Annex G.2 or Annex G.4.
●
For tests with carrier aggregation, select the "Over All Stop Decision"
General Description
深圳德标仪器
135-1095-0799