This document discusses the implementation and optimization of dual polarization microwave links using XPIC technology. It covers: - Using dual polarization antennas and XPIC to create two radio links through one path for increased capacity and hardware protection. - The hardware configuration including two MMUs and RAUs integrated to a dual polarization antenna at each terminal. - Procedures for alignment and configuration of the dual polarization links. - Tests and optimization of cross polarization discrimination (XPD) to ensure adequate isolation between the two polarizations. - Using ML Craft to test for interference by turning off the far end transmitter and checking for unexpected signal levels.

1. ML-TN Xpic
implementation
and
xpd Optimization
Khalil Al-Alami

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›Dual Polarization MW.
›XPIC Technology.
›XPD Test and Optimization.
›Interferences and its impact.
›Interference Test for ML-TN MW.
Agenda

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› Is the MW radio link combination where we creates two links
through one path with different polarization and via one dual
polarization antenna at each terminal.
› Here we use such technology to duplicate the capacity. And
in the same time it’s a hardware protection, in case one
polarization has hardware problem one polarization will carry
the traffic but with the half capacity.
› In each radio terminal there will be two MMU’s which supports
XPIC and two similar band and sub-band RAUs.
› The two RAUs at each radio Terminal will be integrated to
one dual polarization antenna via a hardware structure called
“integration kit” or “Assembled OMT”.
Dual pollarization

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›
Mini-link tn instalation
MMU2 K
MMU2 K
RAU
RAU
MMU2 K
MMU2 K
RAU
RAU
f1
f1
f1
V
f1
H
V
H
XPIC
Dual Pol.
XPIC
Dual Pol.
Packet link V
Packet link H

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›
Dual polarization installation
Feed
Integration Kit

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Dual polarization installation

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› For protected (1+1) radio terminals, two MMUs must be
placed in a pair successively, starting with an even Slot.
› Each pair of MMUs placed in adjacent slots (2 and 3, 4 and
5, and so on) is related to the same polarization. The XPIC
cable to be connected between the 2 MMUs which will build
XPIC. Therefore, the front panel XPIC cross-cable connects
modems in alternate slots (2 and 4, 3 and 5, and so on).
Mini-link tn installation

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› It is better to enable the XPIC during Configure Radio
Link.
› When you configure the Modulation capacity for each radio
link of the 2+0 links the value will be half of that in the FSC
then the total capacity of the 2+0 will be as the FSC. For
example the below FSC the Modulation Capacity will be 204
and 46
Mini-link tn Configuration

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› XPIC cable: RJ45-RJ45 screened 100 Ω pair cable
(4x2x0.25) cable with the below Pin layout.
XPIC signal cable

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› It is better to enable the XPIC during Configure Radio Link.
Mini-link tn Configuration
slot 2 config. (Vertical) slot 4 config. (Horizontal)

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› WAN Creation: go RL-IME and select Radio Link Bonding
Mode, and Assigned the 2 Packet Links.
› Note: (For 6P, NPU3D only RL-IME 1/7/100 and RL-IME
1/7/101 can do the bonding configure, 20P NPU1C RL-IME
1/11/100 ~RL-IME 1/11/107 can do the Bonding)
› Right Click RL-IME then Configure :
Mini-link tn Configuration

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Mini-link tn Configuration

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› Turn off the transmitters for H pol and do the Alignment
for V polarization as normal 1+0 until get the max RSL.
› Loosen the 4 screws on the OMT Assembly with the Reflector
Support Bracket. Rotate until the max value is found. The
rotation range is ±5°. Do the same procedures in both Sites.
› Turn the H Pol on and check the RSL at both Pol.
2+0 alignment.
Dual Pol Antenna
RAU
Integration kit

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Cross Polarization Discrimination
Optimization (XPD):
 The Min XPD value for bands (15 – 38 GHz )= 27dB
 1st do the XPD test (see XPD Test Slides), if value is >= 27dB then done,
else you need to do XPD optimization by the below steps:
1. Turn on the Tx on far end of V pol and turn off The Tx of H.
2. Check with a voltmeter at near end on the RAU of H pol and Rotate +/-
until the worst voltage value found. (The rotation is performed to
minimize the leakage between the two polarizations, that is, to
maximize the XPD).
3. Verify the RX Level at near end in H pol and record the value.
4. Verify the RX level at near end in V pol and record the value.

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XPD Optimization :
› A cross polarization discrimination (XPD) of at least 27dB
must be reached. The value is the difference between the
signals measured on the two radios (H & V).
› If the reached value is less than 27 dB, perform steps (1,4)
again.
› If the reached value is less than 27 dB, after repeating steps
(1,4) verify again the hardware installation.

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This screen shots to show how to check the XPD value by
MINI-LINK Craft.
• Vertical & Horizontal TX ON
• Polarization: Vertical
XPD Test screen shots

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XPD Test screen shots
• Polarization: Horizontal

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• Vertical TX ON & Horizontal OFF
• Polarization: Vertical RSL.
• Polarization: Horizontal Off . XPD=27.0dB (different
between Horizontal and Vertical) and its critical.
XPD Test screen shots before XPD alignment

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• Start the Test.
• Vertical TX ON & Horizontal OFF
• Polarization: Vertical RSL.
XPD Test screen shots After XPD alignment

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• Polarization: Horizontal RSL.
• XPD= 33.0dB (different between Horizontal and Vertical).
Which is better than before.
XPD Test screen shots After XPD alignment

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› Interference is one of the challenges which is facing the
MW Radio systems. It can degrade the performance or even
stop the transmission.
› During the alignment when we face difficulty to achieve the
desired RSL, the interference is one of the issues we expect.
› Also during the link life when we get E1 BER or Ethernet PER
we put the interference in our considerations.
› Here we will take the interference test by using our ML Craft:
Access the far-end terminal through ML Craft and switch the
far-end transmitter off. Note: In a 1+1 system both
transmitters must be switched off.
Check RSL level at near end, If the level exceeds -90dBm,
there could be a such interference. Like in the following screen
shots.
Interference Test

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› We off Transmitter power from Far end
at RSL view by tick Transmitter on Ra1 box and save.
Interference Test Scr. shots

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› Check the RSL at near End terminal. In this below screen
Shot means there is an interference.
Interference Test Scr. shots

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› In this screen shot its normal RSL as no signal coming from
The far end terminal.
Interference Test Scr. shots

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› After you finish the test don’t forget to turn the far end
transmitter to restore back the traffic.
Interference Test Scr. shots

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