450b SM will no longer connect, noise?

I have no decent experience with Cambium products, so please be gentle. I have an AP with single SM (PMP 450b High Gain, no other customers on tower) that will no longer connect. It has been working fine for many, many weeks. Both SM and AP have been rebooted.

I’m thinking it could be noise, but hoped CBRS would have done a better job at avoiding that. When I try to change channels I get:

05/02/2022 : 14:25:16 UTC : [1] Too much interference caused by the device for other users, hence grant rejected
05/02/2022 : 14:25:16 UTC : [2] Too much interference caused by the device for other users, hence grant rejected

Spectrum analysis looks awful, but admittedly I’ve never looked at it before so unsure what it was prior to the issues. I only have the single AP on the tower but I know another provider had added equipment, but again hoped that the CBRS platform prevented creating noise like this for a device with existing grant.

SAS isn’t at the point where it can help us with this automatically. In fact, I had issues getting my PAL enforced with a rogue operator. Basically, I was told to make a ticket with the FCC.

Anyway, have you tried lowering it to 20Mhz and putting it at 3610? You might have luck contacting the competitor as well and getting on the same frame period. If you already had it there you can try a bit up or down to see if it will run until you can figure out another solution for the customer. Even 10 or 5MHz might work until then.

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I have tried to change lower to both 20Mhz and 10Mhz, but once I make the drop-down change, click save then reboot, when the unit comes back online it has reverted to operating at 40Mhz?

I’ve had that issue on older firmware
Try this after you make the frequency change, on the web gui, try going to home> session status, then select relinquish grant and perform relinquish grant and deregister. You might have to uncheck it after it’s done.

On 20.2.1, you should be able to change the frequency/bandwidth without a reboot

I’ve managed to set it to 3610/20Mhz but it just sits idle and won’t bring the radio online.

05/02/2022 : 17:27:19 UTC : Domain Proxy URL resolved
05/02/2022 : 17:27:19 UTC : Initializing CBSD
05/02/2022 : 17:28:14 UTC : CBSD is already registered with SAS
05/02/2022 : 17:28:14 UTC : CBSD is already registered with SAS
05/02/2022 : 17:29:21 UTC : Sent Spectrum Inquiry
05/02/2022 : 17:29:21 UTC : Received Spectrum Inquiry Response
05/02/2022 : 17:29:21 UTC : No channel available in the spectrum inquiry response
05/02/2022 : 17:29:21 UTC : Frequency parameter unavailable

I’m afraid to release the existing grant thinking I won’t be able to bring the radio back online at all? Changing back to the original 40Mhz and 3680 brings the radio back online, but still no SM connection.

I don’t understand why you’re afraid… if the SM isn’t connecting in the first place, then who cares if you change the grant? So first off, please update both radios to firmware release R21. Second, no need to do anything in cnMaestro… you can simply change the center channel and channel width on the AP/master and this will release and request a new grant. As Alex mentioned, the best channel for you to use is probably 3610 @ 20MHz. Lastly, if you can figure out what equipment is being used at this site you might be able to use GPS sync to help reduce interference. If it’s LTE operators, change your AP to use 5ms frames and then enable the LTE collocation settings on the radio config tab to match their settings. If it’s a Cambium operator, try working with them and copy their sync settings. ALSO, you’ll need to make sure that your AP/master is getting a 1pps GPS sync source. There are various products that can do this.

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The SM was randomly connected, but it was unreliable.

I’ve changed the center to 3610 and 20Mhz. The logs shows the request was denied. I’ve changed the settings to 3635 and 10Mhz, and waiting to see if the SM will connect.

05/03/2022 : 16:31:41 UTC : CBSD is already registered with SAS
05/03/2022 : 16:31:41 UTC : CBSD is already registered with SAS
05/03/2022 : 16:32:42 UTC : Sent Spectrum Inquiry
05/03/2022 : 16:32:43 UTC : Received Spectrum Inquiry Response
05/03/2022 : 16:32:43 UTC : No channel available in the spectrum inquiry response
05/03/2022 : 16:32:43 UTC : Scheduling channel hunt as frequency parameter is unavailable
05/03/2022 : 16:34:12 UTC : Sent Spectrum Inquiry
05/03/2022 : 16:34:13 UTC : Received Spectrum Inquiry Response
05/03/2022 : 16:34:13 UTC : NumChannels = 13, Frequencies = 3555000 kHz 3565000 kHz 3575000 kHz 3585000 kHz 3595000 kHz 3625000 kHz 3635000 kHz 3645000 kHz 3655000 kHz 3665000 kHz 3675000 kHz 3685000 kHz 3695000 kHz
05/03/2022 : 16:34:13 UTC : Selected frequency 3635000 kHz at 10.0 MHz channel bandwidth
05/03/2022 : 16:34:13 UTC : Attempting 1 grants in multi grant mode
05/03/2022 : 16:34:15 UTC : Received grant expiry = 2023-05-03T16:34:14Z
05/03/2022 : 16:34:15 UTC : Received grant heartbeat duration = 60
05/03/2022 : 16:34:15 UTC : Received channel type : GAA
05/03/2022 : 16:34:15 UTC : Domain proxy heartbeat timeout modified from 60 to 55 seconds
05/03/2022 : 16:34:15 UTC : Grant renewal will be attempted 168 hours before expiry
05/03/2022 : 16:34:15 UTC : CBRS spectrum grant suspended by SAS.
05/03/2022 : 16:34:15 UTC : Error data received from SAS : ["Interference Calculations Pending"]
05/03/2022 : 16:34:15 UTC : SAS Error : SUSPENDED_GRANT: Interference Calculations Pending
05/03/2022 : 16:34:15 UTC : [0] Received grant suspend
05/03/2022 : 16:36:06 UTC : Channel bandwidth change requires reboot on 450m. Change frequency and bandwidth based on available grant.
05/03/2022 : 16:37:07 UTC : Channel bandwidth change requires reboot on 450m. Change frequency and bandwidth based on available grant.
05/03/2022 : 16:38:07 UTC : Channel bandwidth change requires reboot on 450m. Change frequency and bandwidth based on available grant.

Which SAS are you using? Did you upgrade both AP and SM to firmware R21? It’s vitally important that you make sure that your CBRS radios are up to date as Cambium is continually improving this functionality and fixing bugs.