Roaming in a warehouse

[INSCOL]

Hi,

What are the best ways to optimize roaming? We have several big warehouses with RF scanners + wireless printers moving around like crazy. They all have around 20-30 Meraki APs on the 5Ghz.

I see a lot of Association failure in the logs (see the screenshots below). I think that when they go from let's say AP1 to AP4, their devices are trying to connect to AP2 or AP3 in between but by the time the association is done, they are already at AP4, causing a "Failed connection". That's what I think, I'm not a wireless expert by far.

Users are not complaining but I don't like seeing Red everywhere in the dashboard 🙂

We did professional surveys and followed their recommendations but I saw nothing about roaming in the survey reports.

Thanks !

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[cmr]

@INSCOL you are correct that, if a device is moving about and you have a decent amount of overlap, you will experience what you are seeing.  If the devices are working then I wouldn't worry about it.  We have a lot of it with wireless phones that people walk around our buildings with and we generally only get complaints in areas where we don't have APs close enough for a seamless handover.

[Twitch]

That's interesting, @cmr @INSCOL . I see the same sort of thing in our shops. We also have employees who roam the shop with handheld scanners.

I recently installed some new APs in one shop, and I have noticed while testing connectivity that the scanner remains connected to the first AP it associated with at the end of the shop, and it remains connected to that AP despite passing two others as I walk away from the original. Even if I stop and stand in front of another access point, the association does not change, but the connection speed sure takes a nosedive. I can verify the AP association by using ap.meraki.com which shows me which AP the scanner is using. In fact, the only way I get the association to change is by turning WiFi off, then back on. At that point, the device will associate with the closest AP.

The scanners we are using are old and sensitive to fluctuations in the connection, which is why I would like the devices to always connect automatically to the closest AP as they roam around the shop instead of remaining connected to one that is 300' away.

We have one SSID and one subnet in the shop. APs are set to Bridge Mode.

I did read this document: https://documentation.meraki.com/MR/WiFi_Basics_and_Best_Practices/Seamless_Roaming_with_MR_Access_P...

This morning I set the channel settings to be the same for all radios on the 2.5 and 5 GHz channels. However, after doing so, I do not see any mesh neighbors listed yet, which makes me wonder if they're too far apart, or if having them all on one side of the shop instead of staggered on opposite walls prevents the neighbor relationship from forming. I'm sure steel columns everywhere doesn't help, either.

The strange thing is that I can walk around with a laptop or my phone and use speedtest.net and get excellent speed along the entirety of the shop using wireless, but I still have to turn WiFi off, then back on to get the association to change to use the nearest AP.

[Bruce]

Sticky clients are a common problem. Unfortunately it is the client that makes the final decision when to roam. You can try and influence this by changing minimum data rates or lowering power levels (even modifying RX-SOP in some instances), but sometimes the clients just won’t budge. There are some times parameters you can modify on the client too.

Mesh only works if the AP can’t get a wired connection (I.e. it can’t get a DHCP address), and then the APs automatically converge onto the same channel (they scan for the meshing SSID). If you’ve got wired connections to the APs then I’d stick with using wired.

[Twitch]

@Bruce   Good info. Thanks for the reply. All of our MR74s have a wired connection, which explains why they are not seeing neighbors except for the APs that we have setup specifically as bridges.

Still, it makes me wonder if we powered the MR74s with PoE injectors and allowed them to make a mesh, would the scanners behave better? Scanning of barcodes is the primary function of the wireless on the shop floors. It's critical to operations as time is scanned off as the piece progresses through the various stages of fabrication. In other words, there really isn't much user data traffic that would normally be seen from laptops, for example. Some folks have cell phones on the wireless, but that is not mission critical.

All that to say, I wonder if the benefits of having a mesh in our case would outweigh the benefits of having a wired network connection to each AP? The roaming would be more seamless for the scanners, and the perception of an improvement in network performance may outweigh the wired benefits. 

It may be worth a test, at least.

Thanks for your post. You have me thinking, which hurts most days, but I try to do it anyway.

Twitch

[Bruce]

By all means give it a try, but I’d be surprised if it works any better. Every time I’ve had APs on the same channel it’s just given me headaches - with the exception of where I’ve expected that, like mesh with just a couple of APs. You don’t need power injectors if you want to try it, just switch the APs to a VLAN with no DHCP server.

Just be aware that because the AP is on the same channel and is broadcasting the same SSID as another, it doesn’t mean a client can connect to it. A client still has to associate to the AP before it can communicate with it, that’s no different to when the APs are on different channels.

If you can then give it a try, the client may more readily associate with an AP on the same channel, than one which isn’t, so roaming may work better, but you’ll also get more interference. If the clients are old then they’re probably not using some of the newer 802.11 amendments (e.g. 802.11k),or they may just not be implemented in the client’s stack, so just see what works best for your environment.

[jmoake]

for my $.02,  there are settings to prevent devices from roaming as long as there is a tiny bit of signal.  older cisco wireless phones for example can be set to a power saving mode that restricts it's radio from even looking at other APs to see if there is better signal until it nearly looses the one it has.  Could be your scanners were designed that way to extend battery life.