Noise-Limited OTA Performance in Transmit Diversity Mode
R&S
®
AMS32-K31
6
User Manual 1175.6678.02 ─ 01
2 Noise-Limited OTA Performance in Transmit
Diversity Mode
This test case fundamentally consists in generating a two-stream signal in TX diversity
mode, and transmitting these two streams simultaneously to the EUT through the two
polarizations of the same cross-polarized measurement antenna (e.g. a quad-ridged
horn). TX diversity mode means that the two streams essentially contain the same data
so that there is no gain in the maximum data rate. The purpose of this single-antenna
MIMO OTA test is to determine the sensitivity threshold of the EUT when the downlink
signal is as stable and robust as possible.
According to the test case specification, the sensitivity threshold is defined as the mini-
mum downlink signal level at the EUT location that results in a block error rate (BLER)
lower than the threshold value of 10%. The level of an LTE downlink signal is defined in
terms of the RS EPRE (energy per resource element of the reference signal; see
ter 2.1.2.2, "Communication Settings"
, on page 11). With a properly calibrated test
setup, the powers of the horizontal and the vertical signal components at the UE location
are equal, and both correspond to the RS EPRE set at the R&S CMW500 (see also
chapter 2.1.1, "Hardware Setup"
In addition to the sensitivity threshold levels at arbitrary angular positions, the single-
antenna test case provides derived quantities such as the cumulative distribution function
(CDF) which serves as an overall figure of merit for the EUT.
As just one test antenna is used for this test, the configuration and test run is very similar
to the standard SISO OTA test which is described in the R&S AMS32 help system. More-
over, a SISO test chamber is sufficient for the test. The following sections describe spe-
cific MIMO OTA configurations and results.
2.1 Configuration
The configuration of a single-antenna MIMO OTA setup involves the following steps:
1. In the "Sensitivity" tab of the "Hardware Setup" dialog, select the appropriate setup
"MIMO 2x2 with single cross-polarized test antenna". See
Configuration
