Transmit power configuration, Power balance optimization for fdd, Online resources – Ubiquiti Networks airFibe5 User Manual
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Transmit Power Configuration
The AF5 allows for a very high degree of flexibility in
configuring transmit power, supported constellations, channel
bandwidths, and duplexing modes. Because of the number of
configuration options, refer to this guideline as you customize
your AF5 configuration:
Depending on the country or region, the AF5 may be
configured to support maximum transmit power as high
as +50 dBm EIRP. Power levels in excess of approximately
+43 dBm will start to affect the maximum supported
constellation.
TX Power (dBm EIRP)
Supported Constellation
43
256QAM
45
64QAM
47
16QAM
50
QPSK
For example, if you have a relatively short-range link and you
need to support a maximum constellation of 256QAM, then
configure the AF5 for less than +43 dBm EIRP.
To minimize interference, you should use the lowest practical
power setting that supports the intended target constellation
for a given distance. Looking at the sensitivity values for the
given channel bandwidth, you should target a receive signal
value approximately 3 to 6 dB higher than the sensitivity
threshold.
10 MHz
20 MHz
40 MHz
50 MHz
8x
-70 dBm
-67 dBm
-65 dBm
-64 dBm
6x
-77 dBm
-74 dBm
-72 dBm
-71 dBm
4x
-84 dBm
-81 dBm
-79 dBm
-78 dBm
2x
-90 dBm
-87 dBm
-85 dBm
-84 dBm
1x
-93 dBm
-90 dBm
-88 dBm
-87 dBm
Ultimate
-95 dBm
-93 dBm
-92 dBm
-91 dBm
To obtain the greatest range performance, you may
want to explore power settings above +43 dBm since
the longest-range links will be limited to the lower-order
constellations. The best possible range will be achieved with
a combination of maximum power level, narrowest channel
bandwidth, lowest-order constellation, and TDD.
Power Balance Optimization for FDD
In the default state, the AF5 has this configuration:
§
TX power: +40 dBm
§
Channel bandwidth: 10 MHz
§
Duplexing mode: TDD
To optimize throughput with maximum frequency reuse:
1. Aim the AF5 using the factory default settings and TDD.
2. Allow the AF5 to automatically rate-adapt.
3. Configure the AF5 for FDD operation.
4. Check the modulation rate and capacity indicators for
asymmetry.
5. You may notice significant asymmetry. If you do, then
this could be due to a poorly aimed AF5 or an AF5 that is
operating in some sort of reflective Fresnel environment.
Ensure that the AF5 is correctly aimed and free of any
potential reflections before proceeding to the next
procedure.
To optimize both ends of the link for the best symmetry:
1. Test for a local desense condition (possibly due to a
reflection or other disturbance). Begin with the AF5 that is
receiving the lowest RX capacity reading, and decrease the
TX power on that AF5 by 1 dB.
a. Check if there is any increase in the RX capacity at the AF5.
b. Watch for decreases in the TX capacity of the AF5.
2. Perform step 1 iteratively to find out if there is any RX
capacity sensitivity to the local TX power level.
3. If this condition persists, try the following:
a. Run the lowest transmit power that still allows for the best
balance of performance on both ends of the link.
b. Increase the FDD frequency separation and repeat the
optimization process. (In general you should run the
lowest power possible to meet the data rate requirements
for the link.)
This link symmetry procedure should be repeated on the
opposite end of the link to test for desense on the other side.
If desense is not an issue, then try this method to mitigate
the asymmetry: Slightly increase the transmit power on the
opposite end of the link. (Note: This should be tried only after
you rule out local desense first.)
For the best possible FDD performance, use as much
frequency separation as possible to minimize external
coupling of energy.
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