reporting an error with GPS synchronization and XM devices!!!!

[Maurix09]

- this week, replace all AP Rocket M5 with AP PRISM AC.

- ALL clients of that node were "AirMax M"->  XW or XM.

- Update the firmware to 6.1.3 (CPE's) and 8.4.3 (for APs).

- Note that several clients appeared as connected to the AP, but they had no latency, and could not access the CPEs.

I could only access if I deactivated GPS synchronization and the FF left it as flexible.

- The problem was the following (at least check it on XM devices) ...

AP configuration:

If the CPE client is configured in MSC0, it can be connected to the AP, but it has no latency, nor data traffic. In summary, it does not work. And technician goes to the client's house, changes to MSC7 or MSC15, and puts it in automatic, and goes out working.

I guess it's a BUG from firmware 8.4.3....

Or is it normal for a CPE client with the configuration in MSC0 not to work well? (because connect, connect but it does not work)

[dignome]

Wouldn't think that is a bug since the setting is certainly not default setting and someone other than ubnt set them to run that way.  Another setting that is not compatible with fixed frame is RTS on M devices.

Now you know what to look for if they do not connect.

[UBNT-SNK]

From an initial look I have to agree with @dignome here. Why were some CPEs set that way? It is not the default configuration. If you want to rate limit individual CPEs it is best to do that at a router.

[elmorekevin]

Surely it makes sense to post a list of incompatible settings when trying to switch to Fixed Frame, this was a good find and thanks for sharing.

I agree with the other here though, if the intention was to rate limit by choosing MCS0, that should be done elsewhere like in Traffic Shaping or a router.

If the intention was to make a very stable link at the extreme cost of little performance, then I would consider it a FF bug. What is the minimum FF should support? If it can't support MCS0, should it be removed totally? If the radio knows it is in FF mode, should it automatically override that MCS0 setting to a setting that it can support?

Lots of questions in situations like this!

[WisTech]

Control rates are transmitted using QPSK by default. Forcing BPSK will prevent control frames from being transmitted, so your CPEs will not pass traffic. I run MCS15 auto on my M5s without issue.  You never want to inhibit your uplink rate potential as it will cause uplink starvation (TCP and wireless acks have to be serviced!).

[tuckerdog]

Ya, all CPEs should be set to MCS 15 (or maybe 7) and set to auto, and then QOS at a router.

You will find the AC AP will out-perform the Rockets in almost every situation.,