This example shows you how to set up the new zone types that have been
added to the N7615C, and how to set up the 89601A VSA software to demodulate
these new zones.
In version 7.01 or later of the 89601A option B7Y VSA software, the
VSA has the ability to automatically decode a DL-MAP and set up the zone
maps for demodulating a signal. Since the signal created in Part 1 contains
a DL-MAP (with the added step), we can either use the auto DL-MAP decoding
or manually set up the demodulation. For tutorial purposes, we will set
up the demodulation manually first, then show how to use the auto DL-MAP
decoding.
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Select
> from the menu or click
the 
button in the toolbar to start a new waveform configuration.
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Click I
in the navigation tree on the left. Set the instrumentr's frequency to
2.5 GHz and leave the amplitude at the default value of –10
dBm.
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Click
in the navigation tree. The carrier table should show one advanced carrier.
If not, delete the basic carrier and add an advanced
carrier. We will use the default Waveform Setup parameters shown on this
page.
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Click
and change the to 5
MHz and to 512.
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Click
in the navigation tree. Click the 
button above the zone table and add an AMC
zone. Signal Studio supports 2x3 AMC zones, which refers to a basic structure
of 2 bins x 3 symbols, where a bin is 9 adjacent subcarriers. Note that
you cannot have just an AMC zone in the downlink, because the first zone
is required to be a DL-PUSC zone.
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Increase the number of symbols in the AMC zone to 9.
(Note this value must be a multiple of 3 because the AMC 2x3 slot size
is 3 symbols long.)
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Click
to view the settings for this zone. Click on the burst that has been added
by default and delete it by clicking on the "X" button. In section
3 of the parameter table, set "Auto DL-MAP" to Normal. You should
now have 2 symbols in this zone, containing an FCH and DL-MAP.
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Click
to view the settings for this zone. As with any downlink zone except the
first DL-PUSC zone, you can set the Permutation Base and PRBS ID. Check
the 
box for more description of these fields. There
is also a field for turning dedicated pilots on or off. When
dedicated pilots are on, it indicates that a subscriber station should
only use the pilots specific to its burst for channel estimation. For
now, leave this field set to off.
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Set
to off. Add a burst with 16QAM (CC) 3/4 modulation and another burst with
64QAM (CC) 2/3 modulation for a total of 3 bursts in the zone.
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Double-click on the row with the first burst, or click
on in the navigation
tree to display the configuration for the burst. Change
the to 110 bytes and
change the
to 20.
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Click
in the navigation tree and make the following changes:
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to 3
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to 6
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to 10
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to 0
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to 170 bytes
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Click
in the navigation tree and make the following changes:
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to 3
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to 6
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to 14
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to 10
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to 310
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Click the 
button in the toolbar to verify that there
are no errors with the setup. Error messages are
also displayed at the bottom of the window in the status bar. Click the
button to download the waveform into the instrument.
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Start the 89601A VSA software and go to
> > . Configure the proper center frequency,
span, and range to measure the signal from the instrument.
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Go to
> > >
to turn on the demodulator.
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Go to
> . On the
Format tab, click on
and select .
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Next we configure the VSA to measure the AMC zone. Select
the Zone Definition tab and click on the Edit Active Zone button. For
Type, select AMC. The AMC settings will be displayed. The default is "2:3”
which is the 2x3 zone configured in Signal Studio, so no change is needed.
The Offset should be set to 3 symbols (to skip the preamble and 2 symbols
of DL-PUSC zone in the downlink signal). Length should be set to 9 symbols.
Change the PRBS ID to 0, delete the default FCH burst, and add the data
bursts that you set up in Signal Studio in the AMC zone.
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Return to the Zone Definition page. Check the box for
Data Burst Analysis if needed to make the measurement on the bursts in
the AMC zone.
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Try measuring one burst at a time. Notice that in the
Error Vector Spectrum plot, all subcarriers for a burst are adjacent to
each other. Also note the burst power profile in the Search Time display.
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In Signal Studio, click on Zone #2, AMC in the navigation
tree. On the right top panel, change Dedicated Pilots to on and then generate
and download the waveform. In the VSA software, go to the Demodulation
Properties window, Zone Definition tab, and click the Edit Active Zone
button, and check the box for Dedicated Pilots on the left, then click
OK. What is the impact of this on the VSA measurement?
You should see that the spectrum has changed and the in-band power
is lower. In the Search Time display, you should see a big power drop
out corresponding to the symbols where there is no data. In the Error
Vector Spectrum display, you should see that there are now no pilots present
for the subcarriers where there is no data. Turning dedicated pilots on
causes Signal Studio to do 2 things: 1) only transmit
pilots for the subchannels that contain burst data, and 2) change the
Zone IE in the DL-MAP to indicate dedicated pilots mode, to indicate that
a subscriber station should only use the pilots specific to its burst
for channel estimation. In normal mode, pilots are transmitted even when
there is no data being transmitted for a particular symbol. With
dedicated pilots turned on, the source does not transmit anything when
there is no data, so the result is the power dropout during the middle
3 symbols of the DL-AMC zone.
Dedicated pilots are used in systems with beamforming.
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Now we will use the automatic DL-MAP decoding feature
in the VSA to make the same measurement. Repeat steps 1 through 3 to preset
the demodulation setup and input the basic format parameters.
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In the Demodulation Properties window, click on the
Advanced tab and uncheck the box next to "Decode ULMAP” since
there is no UL-MAP present in this signal.
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Click on the Zone Definition tab, and select "Auto”.
After one or two updates, you should see the zone maps displayed. Click
on the second zone to measure the AMC zone. To measure a single burst
only, select "Use Map File” and then click on the desired burst.
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In Signal Studio, select
> from the menu or click
the button in the toolbar to start a new waveform configuration.
Leave the instrument settings at the default frequency
of 1 GHz and amplitude of –10
dBm.
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Click
in the navigation tree and change to Uplink Only (TDD).
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Click Uplink in the navigation tree. Change to off, then change to 9.
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Add a second regular burst to the zone.
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Click
and change the to
250 bytes.
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Click ,
change to
16QAM (CC) 3/4, and change
to 450 bytes.
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Generate and download the waveform.
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In the 89601A VSA software, go to
> > . Configure the proper center frequency,
span, and range to measure the instrument's signal. Go to
> > >
to turn on the demodulator.
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Go to
> . On
the Format tab, select ,
click on and
select .
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Next we configure the VSA to measure the PUSC zone.
Select the Zone Definition tab and click on the Edit Active Zone button.
Set the PermBase to 0 and Length to 9 symbols.
Uncheck the
box. Delete any existing bursts before creating the new ones. Create the
two bursts that you set up in Signal Studio: Burst 1 is QPSK, 44 slots,
Burst 2 is 16QAM, 26 slots. If needed, set to Wrapped.
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Return to the Zone Definition page. Check the box for
Data Burst Analysis if needed to make the measurement on the bursts in
the PUSC zone.
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Notice there is a
dot in the center of the constellation, and the OFDM Error Vector Spectrum
plot shows green data points in addition to the orange and red ones that
correspond to the two data bursts. Why is this?
(Answer: Look on the Advanced tab in Demod
Properties on the VSA. Note that the default settings say "include
inactive subchannels.” Uncheck this box and
notice that the center dot and green data points disappear. The default
includes inactive subchannels because of the way RCE/EVM is defined for
uplink signals.)