Wi-Fi Interference with Cisco WLC 5508 / AIR-CAP3702I-E-K9 / Large Glass Protection Screens

[Mike Pennycook]

Hi All, 

We are troubleshooting slow Wi-Fi speeds in a new office we are moving to. This floor has:

 - lots of large glass windows,

 - glass partitions for meeting rooms

 - and recently, glass shields on top of desks which were put in for Covid protection

We find that when we are close to the AP the max download speed is reached (approx. 30mb which is capped) but when we test about 15 meters away from the AP with lots of desks (including their glass shields) in between, the download speeds can drop to about 10Mb. This is tested using Speedtest.net

The glass shields are about 7-8mm thick and when standing next to them the height would be about 5 foot 6 inches. I've attached some pictures to give an idea of the glass shielding attached to the desks. With only few people currently in the office, approx. 5, the download speed had dropped considerably. 

Is there a possibility of these glass shields causing interference in the Wi-Fi signal (2.4Ghz/5Ghz)? I hope the picture shows the setup clearly, but in between a set of two desks you will see a partition that goes up and supports a glass shield. The second picture shows the thickness of the glass shield.

Appreciate some Wireless expertise in helping us troubleshoot this issue!

Many thanks

[Leo Laohoo]

Talk to the manufacturer of these glass sheet.  Are these classed/classified as "low E" or not? 

[Mike Pennycook]

Thanks I will check this

[Mike Pennycook]

Hi @Leo Laohoo the glass is not certified as "low e" , but they are 8mm toughened glass

[Leo Laohoo]

"Toughened" glass?  Like "reinforced glass"?  If this is so, then it is just as worse (maybe worst) than "low e" glass.  

I've been to a site with reinforced glass all over the place.  No wireless signal can bleed out through those until someone opens the door.

Here is one way to test:  Take the glass off and lie them (flat) on the floor.  How is the WiFi after doing that?

[Mike Pennycook]

@Leo Laohoo thanks I'm just getting the exact specs. Unfortunately I don't think it's easy to remove these glass panels from the desk, but we are trying to do some tests where there are no glass panels in the line of sight. I'll check again if it's possible to remove the glass panels.

[Leo Laohoo]

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@Mike Pennycook wrote:

 I don't think it's easy to remove these glass panels from the desk

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Can you, at least, move the glass + desk to form a void? 

I would like to know if you move the glass + desk to form a "wall" around a small area to test WiFi.

If this is not possible then do the opposite, put an AP in between two glass "walls" and see how the WiFi bleeds out.  That is the only way to determine if these glass actually complicate the issue.

[patoberli]

One thing I might miss on the pictures, where are the APs mounted? Centrally in the ceiling or on the sidewalls?

You might have some luck with mounting them in the ceiling or in parallel to the glas windows, but in general, glass = evil for wi-fi signals. Besides not really getting through (reinforced or low-e) glass, it also causes incalculable reflections, which wreak havoc with the quality. 

Regarding your speed numbers, are they Mbps or MB/s?

[Mike Pennycook]

Thanks for your response

The APs are mounted on the ceiling, not hidden within it but exposed so they are visible. I'll see if we can adjust the positioning of one of the APs to see if that has any effect. 

Yes it does look like glass has quite a bad effect on the signal, I'm just trying to verify what the exact specs are. There are glass doors, meeting rooms on the whole floor. 

The speed numbers are in Mbps using Speedtest.net

[Mike Pennycook]

Hi All, 

Turns out there was a port on the switch (older but 100mb full duplex) connecting to the AP with lots of incrementing output errors. Interestingly we didn't need to swap the cable out but put in a new switch (1Gb full duplex) which had no incrementing output errors on the interface towards the AP. This has solved the problem and low download speeds!

Thanks for your advice regarding the glass however, I've got in touch with the manufacturer and we will be doing an in-depth Wi-Fi survey shortly to see how much of an effect that has had.

Many thanks

[Rich R]

back to basics - glad you solved the problem.