SM deregistered - No GPFs from AP. Check signal level and interference on channel

Products ePMP
1

Hi Cambium,

I'm a french customer (in south of France) for a french internet service provider (Alsatis)

I'm trying desperately to install a new antenna (force 200 (5Ghz)), following a migration of speed

The problem is that my SM see the AP but it cannot register on the AP

On the wireless monitor ( and in syslog too) i'v got this message :

SM deregistered - No GPFs from AP . Check signal level and interference on channel

The AP is installed on the top of a church and my SM is 2km far away from it

I have tested my SM at the foot of the church and it's register perfectly

I'm going back to my installation site and the SM cant' register at all!

My software is 3.2.1 and my firmware version is : U-boot9342_PX1.1.4.e (Jul 15 2016 - 20:07:31)

i  ve only access on SM as admin, no access on AP unfortunately

I would like to have your opinion on this subject please

2

Hi,

From attached screenshot I can make conclusion that SM see two APs on same channel with same RSSI (-73 ~ -74 dBm).

And it cannot connect because of they produce interference for each other.

Could you please clarify why two AP are visible with same RSSI levels for SM?

Thank you.

1 Like
3

Hi,

indeed, from what I know and what I see, it's seem there are 4 AP on the church (surely the 4 cardinal points and probably more for a link with another antenna far away )

I am south of the church, so i guess the SM is seeing the south's AP and maybe the north's one ???

Most of the time, I only see one AP (and it's the first one on my screenshot)

 Is it possible to have four AP with same channel bandwidth and same frequency carrier ???

4
@djfot wrote:

Hi,

indeed, from what I know and what I see, it's seem there are 4 AP on the church (surely the 4 cardinal points and probably more for a link with another antenna far away )

I am south of the church, so i guess the SM is seeing the south's AP and maybe the north's one ???

Most of the time, I only see one AP (and it's the first one on my screenshot)

 Is it possible to have four AP with same channel bandwidth and same frequency carrier ???

Hi, 

We do not support frequency reuse across 4 APs (i.e AAAA). We support ABAB (two frequencies across four APs) enabled using GPS sync. What antennas are the north and south APs using? Are they the Cambium sectors? If not, do you know if the third party antennas have at least 30 dB of Front to Back ratio? If there isnt enough F/B ratio, then the north and south AP will interfer with each other if they are using the same frequency or overlapping frequencies.

There is iterature on the Cambium support web-site on how to correctly setup an ABAB deployment using GPS sync. If you need further help, please don't hesitate to contact our support team so an engineer can help you with this.

Thanks,

Sriram

1 Like
5

Hi

you are right

i ve been to the church to see frequencies used

So we 've got this:

South and West : 5700

North and East : 5660

For the hardware i don't know if it's Cambium or not, but i know it's mixed

look at the photo, maybe you will know ?

 i also know there are "old AP" ( 5.54Ghz) i'm still using it to connect to the internet ...

i think my SM isn't a GPS sync model

by the way, what is GPFS for ?

do you think, my difficulties to register on AP could come from settings too strict from my internet provider service?

thanks

6

Sorry to bump a post that is over a year old, but I looked at the supplied images and one thing stood out to me

Why in the world do all the APs have the same SSID in my experience this is a bad idea.
this could be the cause of the issue.

7

That's a good catch Spookie but I believe the issue is still the front-to-back is not sufficient. The isolation between the North and South AP appears to be < 10dB! That's barely enough to hold a link! I think the antennas do not provide sufficient FB ratio or they are not installed directly front to back. 

Also we don't know what the channel sizes are. If they are 40 MHz channels, then there is not enough guard band between the 5660 and 5700 center frequencies. We need at least 5 MHz of guard between adjacent sectors provided all APs are sync'd. 

1 Like
8
@djfot wrote:

Hi

you are right

i ve been to the church to see frequencies used

So we 've got this:

South and West : 5700

North and East : 5660

For the hardware i don't know if it's Cambium or not, but i know it's mixed

look at the photo, maybe you will know ?

 i also know there are "old AP" ( 5.54Ghz) i'm still using it to connect to the internet ...

i think my SM isn't a GPS sync model

by the way, what is GPFS for ?

do you think, my difficulties to register on AP could come from settings too strict from my internet provider service?

thanks

Hi djfot, 

From the picture, two of the antennas appears to be panel antennas. Not sure what make or model they are but it is critical they provide enough FB ratio (>30 dB).