PMP 450 Ask the Experts May 13

@test123 wrote:

My Questions are for the PMP 450 900mhz:

- How well will the AP and SM cope with interferiance (both self and exsternal)?

- Will the AP and SM have inbuilt interferance filters or filtering?

- Will there be some kind of GPS sync allowing for frequiency re-use in 4 and 6 gang configuration?

- Willl there be  MIMO and in what conguration?

- What antenna selection wll be avalible for the PMP450 900, both for SM and AP?

Lastly, please dont bring back that god alful reflector dish... The Fore 110 was a great step forward.


  • In the 900 MHz band, the planning guidelines to minimize the interference are equivalent to those in any other band. The APs have to be GPS synchronized, and the downlink and uplink frames aligned (this always happens if configuration parameters are the same). Frequency planning guidelines should also be followed like in other bands.
  • The AP and SM do not have inline filters. The AP has a super heterodyne receiver to suppress out of band interference.
  • GPS synchronization is available. Frequency reuse is possible in back-to-back sectors.
  • Both MIMO-A (added robustness) and MIMO-B (higher throughput) are available in the 900 MHz product. The radio dynamically adapts the modulation according to varying channel conditions.
  • Both the AP and the SM are connectorized (no dish). For the AP, we are planning to have a 60⁰ sector and a 90⁰ sector options.

1 Like

Thank you to everyone who participated in today's session, and a special thanks to the PMP 450 development team. Feel free to continue to post questions to this thread or recommend it to your colleagues.

Our next Ask the Experts session will be Wednesday 20 May, when we will have three WISPs from North America answer any questions you may have. Details on that session are HERE.

@CambiumMatt wrote:

@David Hannum wrote:

Questions about PMP450 900MHz

1)  What will the AP and SM total throughput be?

2)  What is the suggested upgrade plan (co-exist with PMP100 gear???)

3)  Any chance it can be backward compatible with PMP100 (450 was touted to do that when first announced)

~ And last but not least ~

4)  Is Q4 avability still possible?

1) First release of 900 MHz will support 5, 7 and 10 MHz channel bandwidths that will have the same throughput of other PMP 450 systems. If you have clean spectrum in a 10 MHz channel, you can get more than 50 Mbps.

2) We will publish a migration plan prior to launch.

3) As stated, we are not planning compatibility with PMP 100, but "co-location" via synchronization will be capable, and necessary for effective migration.

4) Absolutely, the launch is planned for Q4 of this year!

Sorry, but if #2 & #3 work as well on the 900MHz as the 3.65GHz does migrating from/colocating with PMP320 then we won't waste our time.  Our test with a PMP450 in the middle of a PMP320 network on 3.65 has been a disaster with no useful solutions.


If the PMP 450 900mhz does not have amazing NLOS thoughput, then I think that will be the final nail in the Cambium Networks coffin.

Since most WISP's and Business customers will move to Telrad LTE for its better NLOS and throughput capability.

@test123 wrote:

If the PMP 450 900mhz does not have amazing NLOS thoughput, then I think that will be the final nail in the Cambium Networks coffin.

Since most WISP's and Business customers will move to Telrad LTE for its better NLOS and throughput capability.

Sure it has better throughput? It does only do qam64 at the moment? And the uplink is even lower? So with LOS it is slower at much higher cost.

@test123 wrote:

If the PMP 450 900mhz does not have amazing NLOS thoughput, then I think that will be the final nail in the Cambium Networks coffin.

Since most WISP's and Business customers will move to Telrad LTE for its better NLOS and throughput capability.

Are you thinking Telrad LTE is great because you tried it and found it to be great?  Or do you think it's great because that's what they told you?  I moved from a Cambium shop to another company running Alvarion/Telrad.  I would give my left arm to have the reliability and mangaeability of Cambium back.

The current state of that product does not have better throughput than the 450....and whether NLOS is better is arguable.  And if NLOS is better, it's the only way in which that product is better.  The rest of what you've heard about its capabilities is stuff they think they're going to do in the future. 

If I go on about it, I risk ranting.


The issue is that the NLoS performance of the 450 is poor.  Then it doesn't matter what the throughput capabilities of the 450 product is since the installation cost becomes to prohibited to install the customer in the first place. 

I currently run PMP FSK900, PMP 320 and 450.  Any LTE platform is going to have the same or likely better NLoS capabilities then the 320.  We heavily invested into the 320 platform, replacing our FSK900 network with it.  We where successful 90% of the time in migrating FSK900 to 320.  Granted to obtain this level of success, ruffly 40% of the time a modification of the original installation was required.   Some examples would be moving the mounting location to a cleaner shot or installing a tripod to clear the majority of the tree canopy. 

There is no real comparison in NLoS between the 450 platform and the 320.  The 320 wins hands down in nearly every situation.  I suspect it is mainly due to 320's 1024fft (subcarriers) vs the 450's 512.  Along with other error correction mechanisms such as HARQ.  Also the 450 is not able to operate at lower signal CINR, S/N ratios with the same reliability of the 320 platform.  This is again likely due to the lower subcarrier count. 

We are continuing to install the 320 platform on new customers and have regulated the 450 deployment to situation dependent or ruffly 5% of new installations.  Unless the 450i platform is going to significantly improve NLoS capabilities over the current 450 platform then it is a non starter.  And 450 in a 900mhz platform is a band-aid not a solution due to limited spectrum and the noise level in that band.  And now it will have to share that band with our existing FSK system for migration is nearly impossible.  Again due to the limited spectrum availability. 

I hope my experience is the odd ball and others are seeing the opposite.  Has anyone seen results contradictory to mine?

This debate between PMP320 non-LOS and PMP450 non-LOS coverage has been going on for awhile. There was a pretty good thread regarding this where I outlined an apples to apples comparison of PMP320 vs PMP450.

From a technical perspective, assuming that you're running legal EIRP's on everything, the PMP320 should only have slightly better non-LOS performance due to the items mentioned by anthonyw... e.g. HARQ, and more sub-carriers. Aside from that EVERYTHING else is better with the PMP450... much much better throughput, and much lower latency, the user interface and manageability, the future looks far brighter as well.

On the Telrad side... something that a lot of people don't know is the fact that the  LTE build they're distributing is only a 2x2 implementation, and it's only 64QAM ATM... which again, side by side comparison, if you're running legal EIRP's... the PMP450 overall beats the Telrad platform when you factor in entry price, ease of management, and overall sector capacity (e.g 256QAM).  By the time that Telrad implements 4x4 and/or 256QAM.... I'd wager that Cambium will respond with the next generation platform that will not only build on the PMP450's success, but surpass the competition.


@paulchops wrote:

On the PMP 450....  we are attempting to read the value that the SMs are set to as far as 1x/2x/4x/6x/8x using OID   It returns no such object.  The notes say "Engineering Use Only".   

We can rate the actual connected rate using:  We use both of these variables in our custom analysis tool.

Is there a way to get the value (setting in the radio for Adaptrate) on PMP 450?  if not today, is is coming?

With the 100 series, platform we can do this without problem.

Paul McCall, PDMNet / Florida Broadband


I will open an issue for this.  Thanks for letting us know!


Cambium Jonathan