Tip:
Highlight text to annotate it
X
Hi. I am Allison Douglas and I am a product manager at Agilent Technologies.
I have been supporting our one-box testers and channel emulators for seven years and
I am going to show you how they work together for a cost-effective solution for MIMO over-the-air
test for LTE devices.
Requirements for MIMO OTA are being largely being driven by cellular operators, who want
to ensure that the field performance of their devices is satisfactory to their end users.
3GGP will be requiring MIMO OTA test as part of their LTE conformance standards.
CTIA and 3GGP are currently discussing what those standards will be and Agilent is actively
participating in those discussions.
The ultimate goal of MIMO OTA test to be able to distinguish a good handset, or device,
from a bad one.
Agilent’s engineers have come up with an innovative new method to help out LTE antenna
and devices designers quickly and cost-effectively validate the MIMO performance over their LTES
devices.
I will now walk you through Agilent’s proposed solutions proposed solution for MIMO OTA test
– two stage method.
The two stage method combines the benefits of traditional an anechoic chamber radiated
measurement with the flexibility of digital channel emulation.
This fast, efficient, and cost-effective method provides a solution for engineers to perform
design validation test until 3GGP and CTIA decide which test methods or methods will
be supported for MIMO OTA test.
In stage one of the two stage method, the device under test is placed in a standard
farfield an anechoic chamber and stimulated by a signal from the PXT, Agilent’s LTE
bay station emulator.
The antenna gain is measured while the device under test is rotated inside the chamber.
This gain information is used to generate a 2-D or 3-D antenna pattern that will be
used in stage two.
A graphical representation of this antenna pattern can be seen here and here.
The setup I have here it is stage two of the two stage method.
Our PXT is generating a 2x2 downlink MIMO signal, which is being fed into two MXA single
analyzers, where the signal is digitized and downconverted to baseband.
The signal is then sent digitally to our PXB baseband generator and channel emulator.
This is where the fading channel model and the antenna pattern gains are applied.
The signal is then sent digitally two MXGs.
This is now our faded downlink signal going to our device.
Since the antenna gains have already been applied, we are accurately characterizing
the over-the-air performance of our device through our cable connection here.
The uplink signal from our device is then going back to our PXT, where we can measure
the physical layer throughput.
There are several LTE channel models specified for MIMO over-the-air test, which replicate
real-world MIMO conditions and channels and generate realistic feeding scenarios including
path and channel correlations.
The PXB emulates these channel models.
In our demo, we will be using the SCME urban macro cell model.
The PXB is also digitally applying the antenna gains from the antenna pattern generated in
stage one.
The favored metric for determining if a MIMO device is good or not, is throughput.
With our existing Tull parameters set up on the PXT, the maximum throughput of this device
19.82 mbps.
We have lowered the cell power to a level where we are being to see some impact on the
receiver sensitivity.
As you can see, our throughput was slightly below the maximum rate.
Now let us see what happens to our throughput rates when we start rotating the antenna pattern.
The data rate we just measured was for zero degrees.
Now on the PXB, we can rotate the antenna pattern to simulate rotating your device inside
an a anechoic nacode chamber.
We will rotate the antenna pattern to 90 degrees and run the throughput test again.
You can see an improvement in throughput, which is what we expect based on our antenna
pattern that has a higher gain at 90 degrees.
We can continue to step through the rotation angles, until we have a complete set of data
for a given cell power level.
This can be repeated for multiple power levels to get a more complete picture of the data
throughput rates for different angles of rotation and cell power levels.
This is what a typical set of results look like, with angle of rotation on the X-axis
and throughput on the Y-axis.
This if we then average the throughput values across the angles of rotation for an individual
power level, we can chart cell power level versus throughput.
This gives us the information we need to show the over-the-air performance for a MIMO LTE
device and meet our initial goal of distinguishing a good device from a bad one.
As you have seen in the demonstration, Agilent’s flexible two stage method using the PXT and
PXB provides a cost-effective and efficient solution for validate of LTE devices.
I hope you found today demonstration useful.
For more information on Agilent’s MIMO OTA solutions please go to www.agilent.com/find/mimo
Thank you for your time. www.agilent.com/find/MIMO