PMP450i - AP Evaluation from an AP

Can we get an AP evaluation tool on PMP450i Access Points? A lot of times in our areas, we're one of the only users of 900MHz and when we start deploying 3GHz equipment, we'll also be in a similar situation. In these cases, it would be nice to know which APs are seeing each other at what signal strength without changing them into subscriber unit mode. This would allow us to plan out our frequency selection better. The spectrum analyzer tool is handy, but it would be nice to know that the RF being shown on the spectrum analyzer is actually our own GPS-synced APs rather than interference from another source.

To clarify, you want AP Eval page to be available on another AP (without converting it into an SM first)? I will ask about this possibility. Are you using cnMaestro? You should be able to tell pretty quickly which of your other APs are in the area and/or being seen by the AP in question...

That's right Matt, I would like that AP evaluation page available in AP mode as well. While we have cnMaestro and our own internal tower / customer map, it would be useful to know at what RSSI we're seeing the other towers at to better plan our frequencies for best performance. Our geography is very rough and sometimes a tower 5km away is invisible yet one 15km comes in strong. It would also be good to know on the edge of our network if we're seeing neighbouring WISPs with Cambium equipment or plain old interference.

I'm strongly in favor for this feature... I think it would be very useful on shared tower sites with multiple PMP450 operators. At a new site with existing operators, it would be awesome to be able to throw up an AP, scan, and then set your center channel/width and sync settings to NOT interfere with their AP(s). This would give far better resolution then just running an SA at the AP.  

BenJ and Eric,

Thanks for posting! I agree it would be nice as well if both AP and SM tried to decode beacons when doing a Spectrum Analyzer scan.

Do I have this correct?

  • Current flow: Configure AP to SM, reboot, scan for APs, store Evaluation data, configure back to AP, reboot
  • Desired flow: Start Spectrum Analyzer on AP, get Evaluation data whenever you want.

If we implemented it, there would be some limitations however, such as:

  • The channel bandwidth must match on the scan and the AP. Right now best to spectrum analyzer scan at 5 MHz, the lowest channel bandwidth for finest grain data. But most APs are not at 5 MHz. So you'd have to do multiple spectrum scans at each channel bandwidth you want to look for APs for.
  • The competitor network operator might have AP Evaluation Data disabled.


So I used to remember in earlier PMP450 firmware versions you could swap an AP back and for between AP and SM mode... but I can no longer find that setting as of 16.1 on 450m or 450i AP's... maybe I'm missing something? Seems like this feature has been removed.

That being said, would it be possible to automate the AP eval scan process, to have it just automatically scan through a checked list of channel widths (e.g. on a 2.4ghz AP we'd check channel widths 10, 15 and 20 as we find those are the most commonly used channel widths both us and our competitors use) and return the results at the end? I know this might take a little while to perform... especially on PMP450i 5GHz AP's where it will need to scan the entire 5GHz band... but what are we talking about here... like maybe 5-10 minutes tops?

I agree. It would be nice to be able to check off channel bandwidths used in an automated scan. We would typically run that sort of scan in a maintenance window or early in the AM on an active site, so having the radio do all the work with switching channel bandwidths and re-scanning would be helpful to minimise downtime. On a new site with no customers, just checking off everything and going to do something for a few minutes is also preferable than having to babysit it, wait for each scan to finish, pick another dropdown menu, start another scan and repeat.

450m can never be a SM, so that option was never not there. It might be a lot of work to get this AP Evaluation to work on 450m. In fact the 450m can't change channel bandwidths without rebooting, so that for sure can't happen.

On non 450m, in 16.0, I moved the option to Radio -> Device Type.

So is this it?

  • Desired flow: Check box desired channel bandwidths to scan, Start Spectrum Analyzer on AP, get Evaluation data whenever you want after scan finishes.

Displaying multiple channel bandwidths on one spectrum analyzer page will be confusing. We'd have to think through that. Maybe keep data separate for each channel bandwidth. Feature creep x 2. :)

I'd suggested in the past (don't remember what product line, ePMP probably) that it would be VERY helpful if we could see what signal in a spectrum analysis was from other Cambium gear, and let us see what the settings were on that remote AP (up/down ratio, control slots, etc) - let us determine whether it would be non-interfering with proper sync.  All the necessary information is in the beacon from the AP, isn't it?


"Check box desired channel bandwidths to scan, Start Spectrum Analyzer on AP, get Evaluation data whenever you want after scan finishes."

That sounds perfect!

Derp, OK... I found the AP/SM switch... right there at the top of radio config! Nice to know that the 450m doesn't support that... although it would be strange if it did! Thanks!

So I don't mind having a long list/page of all the AP's and channel widths, as long as it's sorted by channel width and channel from smallest to highest... e.g. if 5, 10, 20MHz are checked, then the page would display 5MHz AP's first, in the order they were found, then 10Mhz, and so on...