Config guard interval

[ComplitNetworks]

At one of our customers we have a negative impact from multipath. I want to use long guard intervals instead of short guard intervals to see if it improves the situation, however I don't know where I can do this config in the Meraki dashboard (checked everything). Any help would be nice.

Thx!!

[ww]

what guard you referring to?

meraki does not let you tweak timers. its intended to be easy to setup and just work.

[ComplitNetworks]

since 802.11n you can choose between a short guard interval and a long guard interval. Single radio/antenna devices do not support mimo and still having trouble with inter symbol interference by multipath, especially in warehouses where barcodescanners are used. normally you can configure that the access point will use long guard intervals (it is 800ns instead of 400ns) to improve the negative result of multipath. And this feature I can not find in the dashboard.

[MRCUR]

You cannot configure this in Dashboard. Short guard is always used from what I have seen. 

If you open a Support case they may have a backend way to change this for a specific SSID. 

[DCooper]

GI is model specific. Atheros and Broadcom both have different GI support for different channel widths and MCS rates in the past.This means the GI would actively shift when you negotiated a different data rate. If you could, forcing a GI would pin data rates.

IMO- I would change the design and add antennas to provide additional diversity before going down this troubleshooting path. Honestly, we rarely troubleshoot multipath issues anymore. I am not even positive this can be changed since it’s usually different depending on the model of chipset/AP running.

[ComplitNetworks]

Hi DCooper

Thx for the feedback, love the learn ;).

It's about barcodescanners, low bandrates are acceptable. offcourse the traffic is mostly upstream, the antennes will not have any issues. We use Meraki semidirectional antennes in this warehouse to focus the signal between all the metal. However some spots giving issues, I have to go onsite to do a validation (this is not done yet) I just thought to have the guard interval as something to try if the RF does not shown any issues (SNR, transmitpower, datarates, roaming issues,...). The barcodescanners does not support antenna diversity I believe. I had some issues in the past with multipath in other warehouses.

Ok, I will see what the packet capture and validation survey on-site will tell us.

Many Thx.

[Hammer]

DCooper.
I assume you mean Short Guard Interval (SGI) when you say GI?
If so, with other vendors that I've worked, I've been able to enable/disable SGI across all of their APs that I've worked with (which is more extensive with some vendors that others). I haven't heard before of this support for SGI with certain channel widths/MCS rates on a per chipset basis.
I would normally decide to enable/disable SGI based on the RF environmental conditions.
Does Meraki have a list of APs and their supported SGI abilities?
Thanks.

[DCooper]

Guard Interval = GI - SGI/LGI is not configurable on Meraki. We do not publish our chipset's and capabilities. I will give you an example on an older common radio, Atheros AR92XX radios or older only support short GI on HT40 & not HT20, so max HT20 rates are 65 Mbps/130 Mbps/195 Mbps (1x1/2x2/3x3) instead of 72 Mbps/144 Mbps/217 Mbps. This information is public.

[Hammer]

Can you confirm if you're referring to the chipsets in the clients or the APs? Just want to make sure we're talking about the same thing here.