ptp 820 field experiences

PTP 820 Field Experiences

January 2017

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PTP 820 Field Experiences

• Resolving RSL issues• Resolving XPI issues• Investigating MSE issues• Understanding Activation Key Violations

Copyright 2017 Cambium Networks, Ltd. All rights reserved.

Resolving RSL issues

• Help! The RSL doesn’t match LINKPlanner’s estimate!

• The LINKPlanner Install Report may differ from the LINKPlanner Performance Summary!– When you are planning a link, LINKPlanner reduces the Maximum Power in the Configuration At Each End to

ensure that the RSL is no greater than -30 dBm in the Performance Summary

– Use the Install Report during alignment!

• Create two LINKPlanner Install Reports: Alignment and Operational– “Alignment Install Report”: In LINKPlanner, configure link (and generate Install Report) as link will be

configured during alignment:

QPSK

ATPC disabled

– “Operational Install Report”: In LINKPlanner, configure link (and generate Install Report) as link will be configured during normal operation:

ACM?

ATPC enabled?

Etc.

• Follow the PTP 820 Installation Procedure outlined on the next page…


PTP 820 Alignment Procedure: Alignment

• Using the LINKPlanner Alignment Install Report– In each link end, configure the link as per the Alignment Install Report

Under Radio, MRMC, Symmetrical Scripts, FCCo MRMC Script operational mode Fixed

o MRMC Script profile Profile 0, 4 QAM, …

Under Radio, Radio parameterso Adaptive TX power admin Disable (disables ACM with Adaptive Transmit Power)

o Tx Level (dBm) as per LINKPlanner’s Maximum Power

Under Radio, ATPC, Local ATPC, Admin Disable (disables ATPC)

– Align the antenna (see following slides)

– Once the RSL ≥ Predicted Received Power, antenna is aligned– Repeat procedure for opposite direction


Antenna alignment

• Remember that the antenna pattern is three dimensional– You can’t simply scan left to right, find the maximum RSL, then scan up and down,

and find the maximum RSL—this procedure might put you on an antenna side-lobe, which is typically 10-12 dB less than the link’s maximum RSL

– You may not find the maximum RSL by scanning in a simple X pattern!

• Start with the LINKPlanner Install Report—use the following:– Antenna Tilt angle– Bearing– Magnetic Declination– Write the bearing (that the installer should see on their compass, including the

magnetic declination) and the tilt angle on the antenna!– Using a compass, point the antenna before you start reading RSLs!

• Scan in a grid pattern—get several scans to find the maximum RSL


Antenna alignment: avoid the side lobe!

XScanning in an “X” pattern can align your link on one of the side lobes!

PTP 820 Alignment Procedure: Operational

• Using the LINKPlanner Operational Install Report– In each link end, configure the link as per the Operational Install Report

Under Radio, MRMC, Symmetrical Scripts, FCCo MRMC Script operational mode as per LINKPlanner (Adaptive)

o MRMC Script maximum as per LINKPlanner (profile Profile 10, 2048 QAM, …)

o MRMC Script minimum as per LINKPlanner (profile Profile 0, 4 QAM, …)

Under Radio, Radio Parameterso Tx Level (dBm) as per LINKPlanner (26)

o Adaptive TX power admin Enable (Enables ACM with Adaptive Transmit Power)

Under Radio, ATPC, Local ATPC,o Admin Enable (enables ATPC)

o Reference RX Level (dBm), as per LINKPlanner Operational Power (-30)

• Observe that the RSL ≥ Predicted Receive Power in both directions!


Resolving XPI issues: What is XPI?

• XPI: Cross Polarization Isolation– How much Horizontal signal appears on the Vertical receiver?

– How much Vertical signal appears on the Horizontal receiver?

• Confirm with the following procedure:– Mute far end V transmitter (Tx). The difference between local H’s RSL and

local V’s RSL is the XPI.

– For example, with far end V Tx muted, local H’s RSL is -30 dBm, and local V’s RSL is -55 dBm. (-30 – (-55) = 25 dB)

– Un-mute far end V Tx, and mute far end H Tx. The difference between local V’s RSL and local H’s RSL is the XPI.

• XPI should be greater than or equal to 25 dB


Resolving XPI issues: Use a level!

• When aligning a cross-polar link (a link that has two signals: one vertically polarized (V) and the other horizontally polarized (H)), each link end’s polarities must be aligned:

– V to V

– H to H

• With six foot (6 ft) or smaller antennas, maximize XPI by:– Aligning the antennas for maximum RSL (as per the alignment procedures)

– Slightly twisting one link end’s OMT

– Instead of slightly twisting one link end’s OMT, ensure that both OMTs are level!

Use a bubble level or digital level at each link end!

• Antennas (typically larger than 6ft) may have separate feedhorns– one for V and one for H

– These separate feedhorns may require individual twist alignment

– Follow the antenna manufacturer’s instructions to ensure that the link end polarities are aligned!


V

V

H

HV

V

H

HV’s alignedH’s aligned

Investigating MSE issues: What is MSE?


MSE: Mean Square Error• A measure of interference• How far away is the received signal from a known

portion of the signal?• -40 dB is typical• -99 dB indicates no link (the modem is not locked)• MSE values > -40 dB indicate interference

Picture from http://www.raymaps.com/index.php/tag/modulation/

http://www.raymaps.com/index.php/tag/modulation/

Investigating MSE issues: interference source

• Self-interference– On a 2+0 link, if MSE improves when either far end transmitter is muted, there

might be a problem with self-interference (ATPC might be needed, for example)– If the link traverses water (or a flat surface) reflections may cause interference—

the RSL may be OK, but the MSE will be higher than -40 and may fluctuate– Check the MSE performance statistics. If the MSE changes over time, or the MSE

changes with other environmental conditions, this may be caused by reflections.– Check the RF connections and/or waveguide.

• External interference– If the RSL doesn’t drop below -90 dBm when the far end transmitter(s) are muted,

there might be a problem with external interference– In other words, if the link is down, and there’s received signal, that signal might be

interference!


Investigating MSE issues: Radio Loopback

• If none of the previous things are remarkable, try a Radio Loopback under Radio, Diagnostics, Loopback

• Radio Loopback is service affecting• Radio Loopback allows you to test one radio at a time (if you have a

multi-radio link (2+0, 2+2, etc., mute all radios except the one under test)

• Radio Loopback provides 60-70 dB of attenuation, good MSE, and zero defective blocks

• Set the Tx power to maximum, set the Radio Loopback, and observe the following:– RSL 60-70 dB less than the Tx Level

If Tx Level is 22 dBm, RSL should be -38 to -48 dBm

– MSE at -40 dB or lower– zero defective blocks


Understanding Activation Key Violations

• Go to Platform, Activation Key, Activation Key Overview (see next page): this will tell you what the radio is complaining about– Activation key-enabled feature usage: what you’re using– Activation key-enabled feature credit: what you paid for– Activation key violation status: what’s wrong (if using > paid for)

• The most common complaint: Ethernet port usage exceeded• Notice that all PTP 820S and PTP 820C radios ship with all Ethernet ports

enabled.– If you’re only using one Ethernet port, the radio will raise a activation key

violation.– Disable the unused Ethernet ports, and the license violations will disappear

• Notice also that all PTP 820G radios ship with all Ethernet ports disabled. In order to pass traffic, you’ll have to set up the RF link, provision Ethernet services, and enable the Ethernet ports to be used.


Activation Key Overview


Thank you

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