Hello, my name is Martha Zemede, a wireless application engineer. As we all know, carrier
aggregation is one of the most important features of LTE-Advanced, allowing wider transmission
bandwidth corresponding to higher data rates. This new technology introduces new requirements
and new challenges to the RF conformance testing of base stations and user equipment. In this
video, I will explain the new RF requirements and measurement challenges pertaining to base
station transmitters and how Agilent can help you address these challenges using X-Series
signal analyzers with the LTE-Advanced measurement application. In this setup, I have the Agilent
MXG vector signal generator emulating an LTE-Advanced base station that is transmitting
both contiguous and non-contiguous carrier aggregation signals. The RF output is connected
to the RF input of the Agilent X-Series signal analyzer that is running the embedded
LTE-Advanced measurement application. Here is a list of base station transmitter tests as
defined in Section 6 of the 3GPP TS 36.141 specification, as well as the list of corresponding
measurements on Agilent's X-Series LTE-Advanced measurement application covering all the tests.
For those of you that have experience with LTE, these should look very familiar. There
are new tests introduced for LTE-Advanced as a result of carrier aggregation highlighted
here in green. Other tests highlighted in dark blue, are existing LTE tests, but the
test parameters have been modified to support carrier aggregation. The time alignment error
test was initially defined for MIMO and transmit diversity in LTE Release 8 and 9. However,
new requirements have been added to LTE-Advanced for carrier aggregation. The most extensive
changes were introduced in Release 11, where new RF requirements were added for non-contiguous
carrier aggregation to take into account additional emissions within the sub-block gap called
cumulative ACLR and cumulative spectrum emission mask. Here is an example of non-contiguous
carrier aggregation with the sub-block gap. Sub-block gap is the frequency gap between
two consecutive sub-blocks within an RF bandwidth. The spectrum in the sub-block gap can be occupied
by other service providers, perhaps deploying other technologies such as W-CDMA.
So the new base station RF requirements within the sub block gap are based on coexistence
for uncoordinated operation. The cumulative ACLR and the cumulative spectrum emission
mask measurements are defined within the sub-block gap, and the challenge with these new
requirements is that you have to take into account contributions from carriers on both
sides of the sub-block gap. I am going to show you how this works with two quick demonstrations.
The first demonstration will include two non-contiguously allocated component carriers
with a sub-block gap of 18 MHz to show the new cumulative ACLR and cumulative spectrum
emission mask requirements. The second demonstration will take you through measurements for five
contiguously allocated component carriers. In the case of ACLR, depending on the width
of the sub-block gap, the leakage from carriers from both sides of the gap can overlap. This
is what cumulative ACLR measures. As you can see here, if the gap is greater than 5 MHz
and less than 20 MHz, either one or both of the inner offsets will be cumulative. For
our demonstration, we will use 18 MHz sub-block gap, so the second offset will be cumulative.
Similarly for spectrum emission mask, the mask within a sub-block gap is calculated
as the cumulative sum of contributions from the upper and the lower sub-blocks, except
for offsets greater than or equal to 10.5 MHz where the mask is non-cumulative per the
definition of 3GPP. So Let us look at our first demonstration. The signal generated
by the MXG vector signal generator is two, 10-MHz wide component carriers with a
sub-block gap of 18 MHz. On the exterior signal analyzer, under the Mode key, there are
LTE-Advanced FDD and TDD modes, but we will focus on FDD for this demonstration. Both uplink
and downlink tests are available, but I will leave it on downlink for base station transmitter
testing. Let us now configure the component carriers. We do that under the Frequency key.
There are two component carriers, but I can choose up to the maximum of five so it is
ready for your future scenarios that will exceed two component carriers. For this demonstration,
the carrier allocation is set to non-contiguous. Now let us configure each individual component
carrier in terms of frequency offsetsand bandwidth. On the screen, you can quickly see the two
10 MHz component carriers with the sub-block gap of 18 MHz. We are now ready to measure
the transmitter measurement and you can see all available measurements from channel power
to occupied bandwidth, to all of the unwanted emission measurements and modulation analysis.
Let us look at cumulative ACLR measurement first. I will select ACP. Since this is a
non-contiguous carrier aggregation, you can define both the inner and outer offset parameters
and limits under the Measure Setup key. By default, the display is showing outer offsets,
but if I go to the View Display key, I can choose to show outer and inner, and it will
show me both offsets. Since the sub-block gap is 18 MHz, I have set the Inner Offset B
to be cumulative. And you can see that listed on the bottom of the table. Similarly, for
spectrum emission mask, you can go to measure spectrum emission mask, and choose to configure
and view either the inner or outer offsets. According to the standard, inner offsets less
than or equals to 10.5 MHz use cumulative mask, and you can see that in the display
with a different color for the cumulative mask. Let us now move to our second demonstration
for contiguous carrier aggregation measurement. We are using five contiguously allocated component
carriers, each 20 MHz wide. The ACP and SEM measurements are similar to multicarrier transmissions
where the limits are defined relative to the carriers on the edges of the RF bandwidth.
For transmitted signal quality measurement, the RF components requirement is to measure
the EVM and frequency error of the individual component carriers. Under Measure, select
Modulation Analysis. I have set up the windows to show the constellation diagram of all five
component carriers. You can change each of windows to show whatever you choose for any
of component carriers. All the powerful demodulation capabilities and the color codings in our
LTE application are available for each individual component carrier. You can also measure the
time alignment between each component carrier by using either an external trigger or the
internal frame trigger. For manufacturing, where speed is critical, the Conformance EVM
measurement returns speed optimized numeric demodulated results for each of the component
carriers. Here, you can see the results for Component Carrier 0, Component Carrier 1,
and more. This completes our tour of the LTE-Advanced measurement application for performing
base station transmitter RF conformance testing as defined by the 3GPP. The X-Series LTE-Advanced
measurement application provides the most comprehensive transmitter conformance testing
in the industry. For non-contiguous carrier aggregation, I showed you the RF requirements,
particularly cumulative ACLR and cumulative spectrum emission mask. For contiguously allocated
component carriers, you saw a quick demo of ACLR and spectrum emission mask. In addition,
you looked at the demodulation measurements where the demodulated results of all component
carriers being displayed side-by-side. For more information and free 30-day trial license,
please visit the links on the screen. Thanks for watching.