CTIA 01.21, Version 7.0.0
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Section 1 Reverberation Chamber Test Overview
Cellular-enabled machine-to-machine (M2M) and wireless-internet-of-things (W-IoT) devices can take on
many shapes and form factors, from health and fitness monitors worn on the wrist to vending machines
and car dashboards. The over-the-air (OTA) performance of larger IoT devices, those having a physical
dimension greater than 42 cm and smaller W-IoT devices, including tests conducted with phantoms, may
be evaluated using reverberation chambers, as described in Section 1.3 of CTIA 01.01 [1]. The exact
placement of the device within the valid test volume of a reverberation chamber is not critical. This can be
an advantage in some cases, for example, for large devices that may be heavy or awkward to position
precisely or for devices where the exact location of the radiating element is not known. When properly
configured, the reverberation chamber provides Total Radiated Power (TRP) and Total Isotropic
Sensitivity (TIS) values for SISO wireless devices with uncertainties comparable to anechoic chambers.
The reverberation chamber produces a multipath environment with a decaying time response. In loaded
reverberation chambers, instantaneous channels corresponding to individual, stepped, mode-stirring
states have a time and spatial dependence (also manifested as a frequency dependence). For most
metrics of interest, the ensemble of stepped mode-stirring states is averaged to provide statistically
determinable channel characteristics. By carefully loading the chamber, the frequency dependence can
be reduced to a level that allows viable wireless communication (e.g. approximating a flat-fading channel)
while still maintaining the statistical nature of the measurement result. That is the approach taken in this
test plan.
In stepped mode, each measurement is acquired over a static multipath channel that is assumed to be
relatively flat in frequency over the coherence bandwidth to be tested. No Doppler component or other
time dependent variations are present during each error rate measurement. Note that when the
reverberation chamber is continuously stirred, additional time-dependent fading occurs. Consequently,
TIS measurements are made using step-wise stirring to eliminate this additional temporal fading during
each TIS measurement.
The reverberation chamber configuration(s) necessary to allow accurate SISO testing of large-form-factor
IoT devices and small-form-factor IoT devices in free space or with phantoms is thoroughly described in
this document. In addition to proper configuration and validation steps, chamber pre-characterization is
described. Because the reverberation chamber must typically be loaded with RF absorber for wireless-
system tests ([2], [3], [4]) and the RF absorbing properties of the equipment under test may affect the
performance of the reverberation chamber ([5], [6]) the chamber’s power transfer function
characterization steps must be carried out under the loading conditions under which the DUT will be
tested. Pre-characterization allows the test lab to measure certain parameters in advance of the actual
device test in order to save time during actual DUT performance testing.
The testing requirements fall into three categories:
1. Procedures for configuring and pre-characterizing certain parameters of the test system.
2. Pre-characterizing certain parameters of the test system.
3. Estimating the power transfer function (path loss) of the test system for the DUT test and
measuring the performance of the wireless device.
