Co-location of 3rd Party 5 GHz PMP with Cambium Canopy 5 GHz PMP450


With a project I'm working on, there is a plan to co-locate on the same tower situated on a hill-top, a 3rd party 5 GHz PMP Outdoor Units (ODUs) in between two existing systems of Cambium PMP 450 APs on 5 GHz. All systems are on 4 sectors that cover 90 deg each. The 3rd party is using TDD system and like the PMP 450s, bandwidth is 10 MHz.

There's about a 100 MHz and 200 MHz frequency separation between 3rd party and PMP 450s.

The two sets of PMP 450s vertical separation is 2.5 m (one is on 15 m and the other one is on 17.5 m). The 3rd party Outdoor Units is planned to be installed at 16 m on the same square lattice tower.

  1. Will it be acceptable for the 3rd party PMP to be at 15 m? From an F-intermodulation study, there is already a 3rd and 5th intermodulation order hits
  2. Is the 100 and 200 MHz frequency separations enough to consider the 3rd party as on different band or range and a 5-feet vertical separation will be sufficient. (one wavelength calculation seems to give about 2 feet only)
  3. The two sets of APs internal antennas are on the same azimuths (15 deg, 105 deg, 195 deg and 285 deg) and vertical separation is 2.5 m (as mentioned above). The 3rd party PMP is on 45 deg, 135 deg, 225 deg and 315 deg. So there's a 30 deg boresight azimuth difference between two different systems. Will the 1 m and 1.5 m vertical separation plus some horizontal offset be enough to meet certain isolation margin (assuming all systems are on the same physical down-tilts, e.g. 6 degrees)? 
  4. If synchronization is a concern, is the idea of having GPS synchronization of the 3rd party PMP taken from the Cambium PMP 450 advisable/possible? (maybe set same parameters setting as well, if possible)



I will get some extra eyes on these questions, but in the meantime, can you clarify for me a couple of things?

Is the other system (not yours) using Cambium equipment? If not, do you know what type of 5 GHz PMP equipment it is?  It may not be possible or likely to synchronize with non-Cambium equipment. There are not that many manufacturers that support timing in the same manner.

That said, with the spacing (both vertical physical spacing and the frequency spacing) should provide some protection against interference.  Can you tell what level of interference you are seeing in the 3rd and 5th intermodulation "hits"?  It may be low enough to overcome with good signal strength.

As Matt mentioned if the 3rd party is Cambium then GPS Sync would allow for all APs to be mounted at the same height without concern for interference.

In the case that they cannot be GPS Synced then 1m vertical separation should be enough with 100MHz of spectral separation.

I would NOT recommend mounting them at the same height.

Also as Matt mentioned you can verify the impact during install by running spectrum analysis from the 450 APs with the 3rd party turned on and turned off. It should be obvious whether or not interference will occur.

I hope this helps.



Hi Matt,

The 3rd Party PMP is the Alcatel-Lucent MPT-Sub6. You can google the name. The specs talks about a Hub Site Synchronization feature via Ethernet and another option using Internal GPS.

Regarding the intermodulation calculation, I only used a tool which calculates the IM products without power component. Actually the product takes into account other co-located radio services as well, like 23 GHz PTP and 18 GHz PTP and LTE Band 1 (2100 MHz).

From online FSPL tool, I can get about 47 dB isolation margin with 1 m vertical spacing for 5.6 GHz so that should provide some protection. Plus the frequency spacing of 100 MHz and 200 MHz, I should not experience further issues.

Thank you for your advise!



Thank you Seth!

I replied to Matt earlier by the way.

1m vertical separation should be enough with 100MHz of spectral separation.

And that step of running spectrum analysis from the 450 APs with the 3rd party turned on and turned off, will be beneficial to see the effect of interference if there's any.

As our customer is replacing the tower, I'm also suggesting to re-locate the Cambium Canopies to another heights to have better physical spacing than 1 to 1.5m just to have some buffer. LOS should not be an issue as the tower is on top of a hill.

Thank you.


1 Like