Some MSM410 AP on MSM760 changing channel randomly at approx 1 per second rate

[Olivier RIEBEN]

We have 17 MSM410 on a MSM760 controller. We had a globally good user feedback until 2 month ago. Then some locations were experiencing random disconnection. We have checked with the tools "InSSIDer 2" and we discovered that 2 AP had ill-behavior: they changed randomly the channel at approx 1 per second rate, between the attributed channel and an other one. If changing the attributed channel, it was then flipping

with an other one. We founded no error, in any log, so we suspected it was a pure radio chip problem and HP changed the AP under guarantee and it was ok again.

But now I have again 2 other AP with the same behavior !

Has somebody experienced the same problem ? Is any reliability problem know with this product of a specific lot ?

[Arimo]

Are there APs installed in the same location as the previously replaced boxes?

The APs are configured to use Auto channel. If you run InSSIDer or similar, do you see new APs in the neighborhood?

What happens if you configure the APs to use static channels according to the 1-6-11 or 1-7-13 scenario?

What SW version are you running? Current releases contain some fixes concernng Auto channel selection.

[Olivier RIEBEN]

- the replaced AP were put at the same place with strictly equivalent parameters (radio, LAN, etc..); only the MAC address and the S/N are different...

- all AP use *fixed* channel according to an in-house planification because according to the MSM760 reports, there is more than 40 AP in the vicinity of my company (near buildings) and channels were allocated not only on the theoritical best channel separation of my own network but also to minimize effect of these perturbating network at every floor/location. A very difficult job.

- due to compatibility request for old WLAN equipement, we work in 802.11g/n.

- a flipping AP has: "Access Point Only", Channel width:  20 MHz, Channel 2, all others as default value

- I tried to change many parameters on the flipping AP without success

- I have updated the MSM and AP to 5.5.2.1-01-10012 without sucess 

[Olivier RIEBEN]

The annexed graph from inSSIDer shows this strange behavior. In fact the AP emits on 2 different channels:

- on the attributed fixed channel (2) with the -55dB 

- on the flipping channel (11 actually) with the -85dB

If Radio is unchecked in the controller for this AP, it stop emitting on the channel 2 but it continue to emit on channel 11 with the low power ! This pause is visible in the graph.

Never seen such behavior !

[Arimo]

That's really weird... I'd get in touch with the support.