OK, most of the Unifi recommendations are that you turn off automatic frequency assignment and then do it, yourself. Of course there are very few guides that tell you exactly how to do that, but basically, there are few ideas that I use.
The Basics: non-overlapping channels
There are six 80MHz 5GHz channels. We try to use the non-DFS ones externally and keep those separated. Two of these are completely free to use and three are DFS which means they are shared with air traffic control radar in the US. So they will detect is the radars are being used and then use them. They also have lower maximum power, so you really want to use them indoors because there is going to be natural signal reduction with the walls in your home and also because they are lower power. The non-DFS are for 80MHz are:
- 42 (36+1). The UniFi notation is a little confusing what this means is that it is a set of 4 blocks of 20Mhz that start at channel 36 and that cover 40, 44, and 48. So each channel is actually a 10Mhz block. They say 42 because that's the average between and it is unambiguous that this must be an 80MHz channel.
- 155 (149+1). This is the upper-frequency block that is really 149, 153, 157, and 161.
The DFS channels for 80MHz are:
- 60 (52+1)
- 106 (100+1)
- 122 (116+1)
- 138 (132+1)
Each DFS seems to have a different maximum output, so here’s the list of what I’ve found are the maximums by the trial and error of changing each of these AP types and seeing what they radiate:
- AC U6-LR. non-DFS: 31 dbM and DFS: 31 dbM
- AC U6-Pro. non-DFS: 30dbM and DFS: 24dbm
- AC HD. non-DFS: 29dbM and then DFS is different depending on frequency so 52:29 100:22 116:24 132: 28
- Ap nanoHD: non-DFS:29 DFS 29
- AC Pro: non-DFS: 25dgM DFS 25
So what this means is the Ubiquiti AC Unifi 6 Long Range (AC U6-LR) are best for pointing into the great outdoors which makes sense given their name. The Unifi AC Unifi 6 Pro (AC U6-Pro) is best for higher-density areas where you have a lot of computers. The AP NanoHD is Wifi 5 and is best for small locations. I also have an AC Pro left over that I can use really small fill-in networking.
Then for 2.4 GHz, there are 3 non-overlapping 20MHz channels even though there are other numbers, they all overall with these frequencies, so
For relatively isolated locations needing outdoor coverage
- Understand which frequencies are overlapping and nonoverlapping
- To get maximum coverage outdoors (this assumes we are talking about a single-family home or farm with some property so you want uniform coverage indoors and then as much outdoors as possible).
- There is minimal interference from neighbors so can just worry about interference
So the key concept is to lump your access points into a couple of classes and then organize your frequencies from the biggest (that need to radiate the most) to the least (which are fill-in systems):
- Exterior boomers. At the same time, you can put them outside of your house. For mere mortals, its probably more convenient just to have them near a window and to angle the curved UFO part outwards towards where you want the signal. The UniFi APs are designed so that most of the power comes out of the "top" and you point where you want to go. In this example, assume there are three outside locations, the Kitchen, the Office and the Mother-in-Law where you want to push signal out along three parts of your property. For your situation, you may want to radiate in four directions or two, it depends on the shape of your property. In today's current lineup, the $179 Unifi U6-Pro is best of this job. Note that these are also going to radiate into the house so you can think of them as your main access points.
- Big fill-in. These are for spaces where you are going to have a high density of computers and things and you want to make sure to have good coverage. A classic example is in the bedroom area where your kids may have a bunch of computers. So in this example, let's call that the Bedroom AP.
- Small fill-in. Finally, there are going to be places that are hard to cover rooms where you just want a "room-size" coverage. For this example assume these are in the Garage, in the Family Room which has a dead spot, the Guest Bedroom, and the Basement. All of these don't get much coverage
So given this layout for this house the “exterior” APs should be set to Auto for 2.4 and Auto for 5GHz. In the strange land of UniFi, Auto really just means High power, but we will leave it on automatic for the day that they figure out how to manage power. They should also use non-DFS 5GHz signals. Now there are only two of those signals and in this example three APs, so what should you do? And for 2.4 GHz, we only have three channels to play with, so what about that?
The first trick is that we need to reserve some frequencies for the "fill in" systems. For the 5GHz, this is pretty simple, we have the four DFS channels at 52, 100, 116, 132 and 149, but for the 2.4 GHz, we only have three, so we use channels 1 and 11 for the outside and then channel 6 for "interior"
The trick here is to use "spatial diversity" which is a fancy term for using the same frequency for the APs that are farthest apart, so the self-interference is low. In this example, we would set it so that the Mother in Law uses the same frequencies as the Office but they are physically very far apart.:
- Kitchen U6-LR 1 at Auto or 30dBM, 42(36+) at 31dBm
- Office U6-LR at 11 Auto (30dBM), 155(149+1) at 31 dam
- Mother in Law U6-LR at 11 Auto (30dbM), 155(149+1) at 31dbM so same as Office but is physical the farther so we are doing space division multiplexing, we could use 6, but this will make it harder to make the fill-in APs not interfere.
For the “big fill-in APs,” we want power at Medium/Auto to fill and this works because Auto in DFS is much less than on the non-DFS channels. These can use medium channel 6 for 2.4GHz and should be far enough apart so as not to interfere and they can use Auto and DFS, as well as they, are indoors where interference will be less and there are three channels that are free here. The trick is to pick the locations that really need the extra power, in this example, the Bedroom is pretty close to the Kitchen and the Office and the Garage is closest to the Mother in Law and Kitchen so this is a good compromise, run them at Medium and Auto and use the channel 6 since they are far from themselves by definition and then pick two of the DFS channels and run them at full. The decision on Medium or Low depends on how well the coverage is working from the main boomers. Turn them down if they are over-covering the 2.4GHz devices:
- Bedroom U6-Pro. 6 at Low (10 dbM) and go to Medium (18dbM) if fill-in is not enough, DFS 138(132+1) at Auto (24dBm)
- Garage U6-LR. 6 at Low (10dbM) and go to Medium (21dbM) if fill in is not enough, DFS 106(100+1) at 31 dBm
We have the small fill-in ones. These need to be at lower power and typically, they are in corners, so they can reuse “the exterior” signals as needed” and try to pick frequencies that have competing APs as far apart as possible:
- Family Room nanoHD. 11 at Low (10dbM), which works because the Office and Man Cave are very far away, DFS 112(116+1) at Auto 29dbM
- Guest Bedroom nano HD. 1 at Low (9dbM) because it is far from the Kitchen and DFS 58 (52+1) at 29dbM
- Basement AC Pro. This one is the furthest away so it can also reuse the interior 2.4GHz so it is 6 at Medium 17dBM and can also reuse the furthest fill-in which is the Family Room 122(116 +1) at Auto 25dbM
You can check to see the interference by starting with the Unifi > Network > Unifi Devices > _the AP_ > Insights section to see the interference on real data. If any of these have significant interference, then start running “Scan”.
You should turn down the small fill-in first as an aside as these should radiate the least. Then check the “big fill-in” and tune these lower signals until there is less. This should leave the outside “boomers” with the most interference-free signal
Working with a House or Apartment with lots of interference
This is often the case in an urban setting where your house or townhouse is right up against neighbors. In this case, most times the neighbors are going to have left their access points on high so you are going to get a lot of interference. The trick here is that you need to take a look at the signals that are in the area and then figure out how to position your AP, so here is what to do:
- Shrink the channels to 40MHz at 5GHz, this will give you double the frequencies to play with.
- Get an application like WiFi Explorer on the Mac so you can see the signals and pick some frequencies with less interference. It might very well be that on 2.4GHz, they will be "odd" that is channel 5 might work better because misconfigured and automatic neighbor access points may not use the 1, 6, and 11 scheme. In this example, look at the signals, you see that channel 5 is clear and that most folks are using the public frequencies, so you can flip to DFS and use a clear channel, in this example channel 165
- Be careful about setting it to auto-optimize, this will hop frequencies as needed, but it can be unpredictable so you might want o just do the optimization yourself.
- Many times in situations like this you are not going to have Ethernet everywhere, so you need to use Meshing so the APs daisy chain, so you want to design something more like a chain with radiating points
So in this example assume you have a very long house and your router and AP are at one end and then there is a Den and then at the far end you have a Basement, so you want to mesh these other two APs together:
- Bedroom UDM. Assume you have a UniFi Dream Machine with a WiFi 5 AP, then set it to channel 5 at 20MHz and set the transmission to Auto. And the 5GHz is at 40 MHz at channel 165
- Den. Set this 2.4GHz channel 1 and Auto and then the 5GHz at 40MHz at channel 149, this will automatically mesh to the Bedroom UDM at 165.
- Downstairs. Set this to 2.4 GHz Channel 11 Auto and then 5GHz at channel 36, this will automatically mesh with the Den AP at 165