PMP450x Release 20.3 is now available

Cambium is officially releasing the PMP450x Radio 20.3 software.

Radio software and documentation can be found on the support site and cnMaestro cloud.

New Features

Enhanced CBRS Alternate channel selection feature (Channel Hunt)

The System Release 20.2 includes a channel hunt feature such that if an operators grants on an AP were terminated, and that termination from the SAS did not include a useable smaller EIRP, the AP would randomly select an available channel from the SAS indicated subset of available channels, and automatically move the sector to this new channel.

The System Release 20.3 adds significant improvements to the channel hunt feature, which are mentioned below:

  1. Instead of randomly selecting a new channel, the AP/BHM will use channel information provided in the Spectrum Inquiry Response message from the SAS as well as the AP’s own spectrum scan information to select the best channel available to move to.
  2. In System Release 20.3, the channel hunt now also takes place not just on terminations, but also on DPA triggered suspensions of the entire spectrum of the sector. The AP will carefully select the best available channel to move to temporarily while DPA is in effect on the original channels. When the original channels are re-authorized by the SAS, the AP/BHM will relinquish the temporary channels and move operations back to the original channels.
  3. The System Release 20.3 channel hunt feature will make use of the Max EIRP provided by the Google SAS for determining the EIRP to request for the new channels. This avoids an inefficiency in the System Release 20.2 channel hunt algorithm, where EIRP higher than that would be requested, causing the new channels to go into suspended state until CPAS. For Commscope and Federated Wireless SAS users, higher EIRP will/can still be requested, and the AP will make use of the same day grant functionality to get AUTHORIZATION immediately.

Support for Federated Wireless and Co-Existence feature

Earlier in the summer (2021) Federated Wireless deployed partial support for co-existence on their production SAS. The sector ID is now used for sorting of the Spectrum Inquiry Response channels. The Spectrum Reuse ID will be stored in the SAS for future use when Federated Wireless supports this parameter as well.


  1. In CBRS Management Tool, usage of Federated Wireless option is not supported for co-existence parameters in cnMaestro version 3.03 and 3.04
  2. This feature is targeted for cnMaestro 3.1 release. However, Federated Wireless and Commscope operators are encouraged to add their Spectrum Reuse IDs into the AP’s database on System Release 20.3 via direct edit on the AP’s UI Configuration → CBRS → Coexistence Parameters, or by pushing a template with this configuration item from cnMaestro.

Additional Enhancements

Products Affected Tracking Description
All 3GHz AP/BHM PMP products CPY-17255, CPY-17392 Improvements to prevent grantRequests going out with slightly higher EIRP than suggested by the SAS in terminations, which causes a grant to go to suspended state.
All 3GHz AP/BHM PMP products CPY-17389 Improvements to prevent CBRS Grant EIRP reduction when changing channels and bandwidths.

Problems and Limitations corrected

Products Affected Tracking Description
All AP/BHM PMP products CPY-17169 AP sends grant request with higher EIRP than operator settings if it’s offered by the SAS.
450i and 450m CPY-17354 Increased prioritization of CBRS task on 450i and 450m.
450SM CPY-17352, CPY-17350, CPY-17355 MPU Violation crash.
All AP/BHM PMP products CPY-17360 Low Priority Data Channel for LUID 3 not appearing under “Data Channel” statistics until auto-refresh.
450 AP CPY-17435 Appropriate calibration values are saved to flash. Unlike, radios storing incorrect values.
All PMP SM/BHS products CPY-17457 Operators advised to migrate to AAA. Add warning message BAM (Bandwith and Authentication Manager) not supported.
450i AP CPY-17455 Problems with High Priority AUX port traffic on 20.x (not seen in previous 16.2.x builds) when using 450i AP.
All PMP AP/BHM products CPY-17365 DL/UL modulation rate reductions seen in certain customers sites on 20.x builds (not seen on software).
450 AP CPY-17477 AP Frame Utilization statistics under heavy load incorrectly shows 0% instead of 100%.
All PMP AP/BHM products CPY-17296 AP running System Release 20.x does not pass through IPv6 Multicast packets downstream.
All AP/BHM products CPY-17283 Few cases with very high antenna Gain confirmed, a CBRS AP running Bandwidth > 10 MHz might see a small unexpected power reduction/limit after bootup.
All AP/BHM products CPY-17475 SM dropped session due to Tx Audit with overloaded traffic and no CIR allocated.
All PMP AP/BHM products CPY-17512 Network loop caused by bridging table conflict after idle SM’s removed.
3 GHz 450m CPY-17527 Improved Modulation Rate adapt algorithm.
450b MicroPoP CPY-17405 MicroPoP was capping SM to 4 Mbps aggregated when MIR source was AAA.
All PMP AP/BHM’s CPY-17556 Configuration file does not have a variable for “MIMO Rate Adapt Algorithm”.
All PMP AP/BHM’s CPY-17562 LQI Downlink SNMP Trap: Beacon LQI OID fixed and added Beacon Percent.
All 450 products CPY-17537 Applied patch updated for vendor code.

Known Problems or Limitations

Products Affected Tracking Workaround/Description
3GHz CBRS AP/BHM CNSSNG-21435 The grants for the temporary channels obtained when channel hunting due to suspension have a clear “tmp” indication in the Logs → CBRS page of the AP. However, this tmp indication is not currently shown on the cnMastro management tool.
Workaround: None
3GHz CBRS SM’s CPY-17460 When temporary channels are obtained due to a suspension triggered channel hunt, the CBRS logs page on the AP clearly marks this temporary channels as TMP. In System Release 20.3, no such TMP indication for the grants for the SM’s (on the AP’s Logs → CBRS page).
Workaround: None
3 GHz CBRS devices CPY-17357 Cambium shows a TMP flag on the HOME-> Session Status page of the AP for all grants that are considered temporary due to being obtained via “same day grant”. However, this flag is currently only shown with FW SDG implementation, not with Commscope SDG implementation. Also, if with FW, there are some inefficiencies and inaccuracies in a few cases on when the flag is set and cleared"
Workaround: None
450b MicroPoP CPY-17383 The Invalid Message Count field on the Sync Status UI page increments by one every second on a MicroPoP Connectorized AP whenever the on-board GPS is active. This issue affects only the connectorized hardware and is not seen on the omni/sector MicroPoP versions.
This issue is considered as invalid statistic, which does not cause any issue with sync stability.
Workaround: None
1 Like

Great news, the 20.3b3 release has been working well for us when the SAS tells us to stop transmitting all 10MHz grants at the AP, successfully selecting and switching to usable channel(s).

But we’re still getting killed by SM-only shutdowns 180° around the tower from those APs while the corresponding APs keep running uselessly on frequencies their clients are prohibited from using… I hate to seem ungrateful, but when can we expect to see the “change AP channel when X% of clients cut off by DPA event” feature? We’re losing customers on a daily basis specifically due to that circumstance, and having to roll a truck for removal sometimes within days of rolling the same truck to migrate clients from older gear to CBRS.


Is there any work being done to support the Google SAS Co-exist/ spectrum analysis?

It’s already supported. Check out this Cambium Course on features introduced in 20.3

1 Like

Thanks for the response Eric. Bad link or did they take it down?

You must login to the training portal.

1 Like

Yeah, I am logged in. Maybe I don’t have access. I can search the topic, but the text is not linked to anything. I will take your word on the coexist working with Google now. Thanks again.

Hmmm strange, you can get to it by clicking on New Training:

Or by searching for 20.3:

1 Like

I’ve reported this problem to the training team.