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I know very little about WiFi. I know how to measure throughput, I know that 2.4GHz tends to be slower than 5GHz but has a further range.

So here's my scenario. I have an office with 1x Aruba IAP-315 with 16-30 clients on at a time, they're all clustered underneath it in a room about 1200 sq.ft.

Off that main room is a boardroom, which, we found going into that room problematic because the WiFi signal would weaken or drop off entirely. No problem, I thought, I'd just put another AP in there. Enter the Ruckus R510 (also with a built-in controller).

So with both of them auto-managing their own 2.4GHz and 5.0GHz networks (same SSID/password for seamless roaming), we found that devices would still hang on to the Aruba rather than switch to the Ruckus, even though the Ruckus was placed in that boardroom.

So, I began tweaking. On the Ruckus, I pulled the power down on the 2.4GHz and 5.0GHz bands to the absolute minimum, ensuring you had to be in that room to have your device connect to that AP.

Then I turned auto-management off on the 5GHz network on the Aruba, and you have to then pick a channel and give it a power setting. I picked a channel (I think I just looked at which channel it was on before), and dialed it back 1-3 dBm at a time. My goal was to have the signal drop off entirely just as I was walking into that boardroom - so that it would switch to the Ruckus, but because the Ruckus signal is so weak, you'd be forced to jump back on the Aruba coming out of that room.

That worked beautifully, except the speeds on both of those APs are now horrendous.

If I disable the Ruckus (just to eliminate variables), put the Aruba back on auto, turn my WiFi off and back on (and watch it jump from 2.4GHz onto 5GHz DFS [I'm not even sure what DFS means ...]), I basically see my throughput quadruple. I want to maintain that and have devices automatically jump onto the Ruckus when entering that room. I thought turning down the power would reduce range but not throughput.

So. What do I need to know to be able to do this properly? I have been in IT for a long time, and somehow avoided learning properly about how RF works. I guess now's the time to roll up my sleeves. I am at your mercy.

EDIT: a day after accepting one of the answers, I did some more testing and found it wasn't working as well as I'd like.

My Ruckus AP didn't allow me to set minimum rates, so I had to get creative. I set my Aruba (primary AP) to prefer 5GHz channels, and I set a high minimum transmit rate. I eliminated all but the top 5, 5GHz channels, travelled into the room where I wanted it to switch and then started turning down the power (on the main AP) until I saw my laptop switch to the secondary AP.

Eliminating channels I didn't want also helped, it seems like some channels punch through walls too easily, hence the devices managing to hang on to the less ideal AP. Also, I found that some channels performed way better (149 for example got me 1300Mbps). I then repeated the exercise as closely as I could with the secondary AP, eliminating slow channels, then setting up my devices where I would want them to switch back to the main AP and turning down the power until I lost my connection to the secondary AP.

Then I took signal and SNR readings, as well as timed 1GB transfers to the main server/NAS.

With Ethernet clocking in just under 13s, my WiFi performance numbers were anywhere between 23.5s - 101.1s depending on where I took the readings from, with the 101 being an anomaly - the next highest was 47.7s, and the average was 39.62s. I'm happy with that.

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Remember that the client decides when to roam, not the AP. Here’s a good way to tune your network:

  1. Adjust the minimum data rates on both APs to 22MHz. That’s about half the maximum rate.
  2. Now adjust the power levels so that clients roam about halfway between the APs.

This will give you the best coverage without sacrificing too much performance.

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  • Why does the minimum data rate need to be adjusted? – Harv Oct 6 '18 at 18:36
  • Because the clients will hang on to the AP even if they're running at the lowest possible speed. You want to set a minimum limit to that speed so they start to roam before performance drops off significantly. – Ron Trunk Oct 6 '18 at 18:50
  • So is the minimum data rate a value that gets sent from the AP to the connecting client, that tells it to roam if the minimum data rate isn't reached? – Harv Oct 6 '18 at 18:54
  • If the client can't associate at the minimum speed, it will look for another AP (roam). If the minimum speed is too low, the client will stay associated with AP-1, even if AP-2 has much better reception. By setting a minimum speed, the client has to roam sooner, and therefore will connect to the better AP. – Ron Trunk Oct 6 '18 at 19:01
  • Right, so these values are communicated from the AP to the client upon associating? This is perfect, just what I need – Harv Oct 6 '18 at 19:02
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If you reduce the transmission power to the point where a connection is barely possible, the speed will be very low. You need to turn up the power until the speed is satisfactory.

(same SSID/password for seamless roaming)

While this allows some roaming it's not seamless. A client will only reconnect to the second WAP when its connection to the first is severed.

All in all, you'll need a controller-based setup where the controller decides which client goes where. This usually requires using a single brand of WAPs.

Also, you'll want to make sure the used channels don't interfere with each other - on 2.4 GHz, the channels need to be three counts apart.

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Another reason Rons suggestion of allowing only higher speeds is a great way to "tune" is because one really slow client can slow down everyone on that AP. A wifi radio sends or receives to one device at a time. Yep, half duplex. Advancements in MIMO have helped and forcing new 802.11 specs to use 5ghz only will help channel interference (which can come from your neighbors as well).

The comment you made about different frequencies is correct. Each channel is a different freq. Lower frequencies penetrate walls better and travel further. You may find a better controllable connection by turning off your 2.4ghz radios and using 5ghz only. We do this a lot in a high capacity designs like schools (vs a high coverage area design where device count is lower in a larger area).

In your 2.4ghz bandwidth you really want to use channel 1, 6 or 11 only. The channels in between overlap frequencies and it can become a mess for you and your neighbors if you use others. Example, if you use channel 4 you can't have a nearby AP on channel 1 or 6 without interference. In 5ghz you can use any channel that doesn't interfere in your air space. They do not overlap with each other.

If you have an android phone there are free wifi analyzer apps that you can see your signal strength and other networks in your area. When adjusting power manually, try to have your devices have -70db or better (this is a negative number so -60 is even better for example) for a quality connection.

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  • Thanks for the info - my Aruba in testing last night had 12 devices and no real load on it, so the way it performed was very different. Today my client reported no real difference despite those hours of tuning, and I suppose that might be because of the 2.4GHz clients that were connecting. Ugh. Instead of 12, we had 39 devices connected,and none of them joined the other AP. What a mess. I may make one 5GHz and the other 2.4-only with only channels 1, 6 and 11 as per your suggestion. Thanks. – Harv Oct 10 '18 at 0:23
  • Thirty-nine clients is a lot for any AP. – Ron Trunk Oct 10 '18 at 0:26
  • I try to keep them under 30 clients per radio. Basically, a classroom of kids. 39 clients mixed on your 2.4 and 5ghz radio's isn't terrible. I'd disable 2.4 all together if you don't have legacy devices without 5ghz radios. Turn the minimum speed connection requirement up higher and maybe power down on the one they won't let go of. Remember, it's not just about the power of the AP reaching the computers, the computers have to reach the AP. Also, the client devices only switches when the original connection isn't good anymore. We see this with school hallway APs with laptops in classes. – Fixitrod Oct 11 '18 at 1:41
  • I thought I'd show how I get to 30 per radio. If my AP radio's are 300mbps max rated you take 25%off the top for overhead. That leaves 225mbps. A student streaming YouTube uses about 6-8 mbps. At 8mbps that's just over 28. I've seen 95 users on one radio and basic surfing was working well. I was surprised but all the pcs had quality radios (all the same model and a customer who thought about it ahead of time) and a good quality low interference connections. Just wanted to explain the why. And we also use 54mbps as the minimum connection speed at that site. Works great! – Fixitrod Oct 11 '18 at 1:52

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