Need advice on AP placements

Ptenisnet

Active Member
Hi all,

I’m moving to a new home and the house is currently under major renovation. I’m planning to have cat6 cables throughout the house and install multiple APs to get good wifi coverage. I already have a Unifi POE switch so will be getting a few Unifi wifi6 APs & the UDM-Pro.

The house is a 3 storey with 6 bedrooms. My worry is all the walls are solid 6” brick (no drywall or plasterboard) & concrete between floors and I have no idea how bad wifi signal will spread through solid walls.



IMG_1360.jpeg




The problem is soon I need to decide where to lay the cat6 cables for the AP positions.


I’m looking to get good wifi 5Ghz coverage in all rooms 1-6 as well as main busy areas (living & kitchen) and to have seamless roaming.


I’m looking for suggestions for best placement for the APs. I’ve sketched some positions (A-E) but using Unifi planner it shows some black spots in the rooms for 5Ghz spread (especially for Room 2)


Also the distance between C & D is about 15 feet, would that give problem with interference?


I don’t mind putting an AP for each room of that is necessary.


I know this is going to be best guess but I’m trying to avoid having to retrofit the cables for the APs after the renovation is completed.


Many thanks
 

mickevh

Distinguished Member
I would prefer to place C & D close to the party walls of rooms 2/3 and 4/5 (even if they are ceiling mounted.) That way the transmissions are firing more perpendicular through the structures rather than at acute angles which means they have to shoot through less material. Take your pick as to which rooms get line of sight - generally one favours the rooms with most users in them.

In order to avoid co-channel interference, you need to devise a radio channel plan so that adjacent cells are tuned to different radio channels. In the 2.4GHz waveband choose from the set [1,6,11] in the 5Ghz waveband just ensure they are different. There's more channels available in 5Ghz, so if your kit can use the "DFS" channels (not all can) you might pick a set so that again adjacent cells are as far apart as possible.

In the 2.4GHz there's only bandwidth for 3 20Mhz (thin) non-interfering channels available or one 20MHz plus one 40Mhz without overlapping and causing interference. In big implementations I normally disable 40MHz (fat) channels in the N protocol for 2.4GHz. That effectively halves the maximum link rate, but gives us more channels to plan with and stands a better chance of creating a channel plan that reduces co-channel interference from neighbouring cells. Even then it often tricky creating a channel plan in the 2.4GHz waveband.

Fortunately more and more Wi-Fi is using the 5GHz waveband so 2.4GHz is gradually becoming something we only support for legacy purposes.

If all of your clients are relatively new, you could disable support for some of the older protocols - B/G/A for example. Technically, that will make it minutely quicker, but you wouldn't notice it in normal use.

Technically there's no such thing as "seamless roaming" - if/when to roam is a decision made by the client devices not "the system." Though "managed" Wi-Fi systems such as enterpirse deployments or some of the newer "whole home" type offerings employ mechanisms to try to "encourage" a client to roam to a "better" AP, but ultimately if the client doesn't want to, it doesn't have to. All we can do a system builders is give it the best chance.

AVF mantra for cabling it so "always run 2" (or more.) It's highly unlikely a UTP will fail in service, but if it does, you are off the air until you rip and replace. If there's a alternate in situ you can get up and running again sooner. Cable is cheap compared to the hassle of installing it.
 
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D

Deleted member 24354

Guest
I would move C & D into rooms 2 and 4 their current locations will be problematic
 

Ptenisnet

Active Member
I would prefer to place C & D close to the party walls of rooms 2/3 and 4/5 (even if they are ceiling mounted.) That way the transmissions are firing more perpendicular through the structures rather than at acute angles which means they have to shoot through less material. Take your pick as to which rooms get line of sight - generally one favours the rooms with most users in them.

In order to avoid co-channel interference, you need to devise a radio channel plan so that adjacent cells are tuned to different radio channels. In the 2.4GHz waveband choose from the set [1,6,11] in the 5Ghz waveband just ensure they are different. There's more channels available in 5Ghz, so if your kit can use the "DFS" channels (not all can) you might pick a set so that again adjacent cells are as far apart as possible.

In the 2.4GHz there's only bandwidth for 3 20Mhz (thin) non-interfering channels available or one 20MHz plus one 40Mhz without overlapping and causing interference. In big implementations I normally disable 40MHz (fat) channels in the N protocol for 2.4GHz. That effectively halves the maximum link rate, but gives us more channels to plan with and stands a better chance of creating a channel plan that reduces co-channel interference from neighbouring cells. Even then it often tricky creating a channel plan in the 2.4GHz waveband.

Fortunately more and more Wi-Fi is using the 5GHz waveband so 2.4GHz is gradually becoming something we only support for legacy purposes.

If all of your clients are relatively new, you could disable support for some of the older protocols - B/G/A for example. Technically, that will make it minutely quicker, but you wouldn't notice it in normal use.

Technically there's no such thing as "seamless roaming" - if/when to roam is a decision made by the client devices not "the system." Though "managed" Wi-Fi systems such as enterpirse deployments or some of the newer "whole home" type offerings employ mechanisms to try to "encourage" a client to roam to a "better" AP, but ultimately if the client doesn't want to, it doesn't have to. All we can do a system builders is give it the best chance.

AVF mantra for cabling it so "always run 2" (or more.) It's highly unlikely a UTP will fail in service, but if it does, you are off the air until you rip and replace. If there's a alternate in situ you can get up and running again sooner. Cable is cheap compared to the hassle of installing it.

But wouldn’t placing the AP close to the party wall makes the coverage a lot worse in the room which has less lines of sight? The reason I place C & D is so I have as much coverage as possible for their adjacent rooms.

For 2.4Ghz done there’s only 3 non-overlapping channels I plan to just enable 2.4Ghz in just one AP for each floor although I’m not sure whether I can do that for Unifi APs. If not at least I hope to reduce the power to minimum.

For 5Ghz, if I put C & D on non-overlapping channels that would solve the issue of interference right? Would there be any other problem arising from their close proximity keeping in mind that I probably have to increase their power hoping to get good coverage in the 2 rooms that each of them serve.

Is it ok use DFS channel? From what I’ve read seems a lot of people avoiding them.
 

Ptenisnet

Active Member
I would move C & D into rooms 2 and 4 their current locations will be problematic

But rooms 5 & 3 will have very poor 5Ghz coverage right? I assuming here that 5Ghz wave have poor penetration through the brick wall ( tbh I really have no idea / experience so just make the assumption because they’re brick lol)

Or are you suggesting that I should place an AP in each room (2-5)?
 
D

Deleted member 24354

Guest
Placing 2,APs where you currently have them will not work, they are too close and will talk over one another. To even get a chance of working you would have to turn the radios down to low, then your 5Ghz would not penetrate any of the walls.
 

mickevh

Distinguished Member
But wouldn’t placing the AP close to the party wall makes the coverage a lot worse in the room which has less lines of sight? The reason I place C & D is so I have as much coverage as possible for their adjacent rooms.
As planned, the only location with line of sight is the landing, everywhere else transmissions pass through at least one wall (or door.) By moving AP's to rooms 2 & 4, those rooms gains line of sight and the other rooms are no worse off (except the landing and who cares about that.) Plus the transmissions pass through the party walls at more of a perpendicular angle which means they have less masonry to get through. It'll even improve coverage in the bathrooms and balcony for anyone who likes to play with their phones there. I'd do something like attached.

For 2.4Ghz done there’s only 3 non-overlapping channels I plan to just enable 2.4Ghz in just one AP for each floor although I’m not sure whether I can do that for Unifi APs. If not at least I hope to reduce the power to minimum.
That's one way to go, then you'll only need three 2.4GHz channels.

For 5Ghz, if I put C & D on non-overlapping channels that would solve the issue of interference right? Would there be any other problem arising from their close proximity keeping in mind that I probably have to increase their power hoping to get good coverage in the 2 rooms that each of them serve.

None at all. About the only "problem" is that the clients may be spoiled for choice as to which AP they choose to Associate with.

Is it ok use DFS channel? From what I’ve read seems a lot of people avoiding them.

Again, none at all. The only "issue" with DFS channels is that the same frequencies are also used by things like weather RADAR and by statute (at least in the UK,) if the AP's detect such RADAR they are required to shut down and change to another channel. For indoor use, unless you live near an air lane or a cost guard station or something, it's unlikely to be a problem.

I had one job in central London where the site was under the approaches to Heathrow and our AP's on the high floors used to moan like mad when EGLL was on Westerly operations (which is about 75% of the time.)

I wouldn't over think it - just try it, if it becomes a "problem," then fix it.
 

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mickevh

Distinguished Member
But rooms 5 & 3 will have very poor 5Ghz coverage right? I assuming here that 5Ghz wave have poor penetration through the brick wall ( tbh I really have no idea / experience so just make the assumption because they’re brick lol)

Or are you suggesting that I should place an AP in each room (2-5)?

Signal penetration through a "typical" masonry or block wall is about 15dB - but the only way to know for sure is to go try it. If this is new build, it may be worse initially as the structure continues to dry out. Wi-Fi hates anything wet or metal. Water tanks, for example, are a real pain. Stud walls made with metal channel aren't a lot of fun either.

15dB sounds dramatic, but even in free air the drop off close to the source can be even higher. Due the simple physics of propagating energy over the surface of an expanding sphere, (in reality no radio transmitter is perfectly spherical) the energy levels fall off logarithmically and the effect is greatest closest to the source. The amount of energy that actually hits the receiving antenna is minuscule compared to what was emitted by the source. The clever guys who design the receivers are well aware of all this and do great things. Paradoxically, you can actually get problems overdriving the receiver circuits if you are "too close" (though you virtually have to sit on it.)
 
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D

Deleted member 24354

Guest
In theory 2 APs on different channels in close proximity shouldn't overlap. In reality it doesnt always work that nicely. My experience with Ubiquiti APs that they will not only overlap they will actually cause significant interference with one another resulting in highly reduced throughput. I am not a radio engineer so I cant tell you why, but as somebody who has installed a lot and troubleshot a lot of other peoples installs, including more than a few AVF members I can tell you that is the reality. That is why I recommended separating the two landing APs into their respective rooms. As @mickevh says the attenuation, even with solid walls shouldnt be too extreme and in may ways may actually work in your favour as it will attenuate the signals between the two APs.

Unfortunately AP placement can often be trial and error as many other things, especially on domestic premises can have significant impact in signal propagation, including boilers, water heaters, mirror wardrobes, foil backed plasterboard, RSJs, metal coated glass, to name a few. Experience helps with placement but sometimes it really is a guessing game. Then you have other factors like Sonos, Sky Q etc which also create their own wifi networks add to this neighbours in close proximity with their own wifi and meshing devices and now it gets even muddier.

Also I just revisited your plan, if you leave them where you intend, C and A may also interfere with one another as they are stacked directly over one another.
 

mickevh

Distinguished Member
Placing 2,APs where you currently have them will not work, they are too close and will talk over one another. To even get a chance of working you would have to turn the radios down to low, then your 5Ghz would not penetrate any of the walls.

It's not just the AP's, it's all the Associated clients. If we think about it like Venn diagram, then the total coverage footprint of any Wi-Fi hotspot is the union of the AP's coverage footprint and all the client devices Associated with the AP. (In three dimensions of course.)

So you can get scenarios where the AP's are far enough apart to not stomp over each other, but the clients are. For example, I live in flats and myself and next door have our sofa's next to each other separated by the party wall; our AP's are "the other side" of our respective rooms. Our AP's don't "hear" each other enough to interfere, but sitting on our sofas, our client devices certainly do.

Unfortunately, none of the freebie Wi-Fi scanners show the clients, only the AP's.

Wi-Fi has a kind of "good neighbour" protocol to cope with this sort of thing: Very roughly if co-channel interference is a "problem" then mechanisms exist to allow a wannabe transmitter to tell everything nearby (whether it's my network or not) to shut up for a bit and give me a chance to transmit. Called RTS/CTS or CTS to self for anyone who want to get into the weeds. It's one of the many, many things that can effect perceived performance over Wi-FI even if we're getting "good signal" on one of those pesky "bar" meters.
 
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mickevh

Distinguished Member
boilers, water heaters, mirror wardrobes, foil backed plasterboard, RSJs, metal coated glass, to name a few.

Mirrors is one of my favourite use case for "Wi-Fi killers" - it doesn't occur to people that it's essentially a huge sheet of metal stuck on some glass. Ever done one of those trendy bars with a mirrored back wall! Fish tanks is one of my other favourites. Ourdoors I've had heaps of hassle with trees that "creep up" on you over time! "It's fine in the winter, but always falls apart in the summer." :D
 
D

Deleted member 24354

Guest
I see this so much - 'I have 5 bars on my wifi, but I am getting almost zero throughput...why?' then people assume because they see 5 bars the problem is with their broadband connection. Some of this is down to AVF-itis a well documented disease that makes people buy the most expensive and powerful devices that they can, 'because bigger must be better right ...??' well not with APs and wifi. Smaller, better spaced, lower power is often the key to getting a better set-up.
'I must have wifi 6'..Why? Wifi6 isnt optimised for faster throughput its optimised for higher densities of connection and I dont mean 20 or 30 IOT devices. Replacing your APs with Wifi6 is not going to illicit better performance on your iphone 12, Pornhub will be quite happy on wifi5. If wifi throughput is that critical to you, you really ought to re-think your network and how devices are connected to it. If you are starting from scratch, great buy whatever is the newest, but for most people your existing wifi 5 APs are going to be good for a few more years yet.

I always love @mickevh analogy where he compares APs to people having conversations in a room. Lots of people shouting loudly is distracting and you only get to hear bits of the conversation that you are trying to listen to. Lots of people talking at lower volume and everyone gets to hear their local conversations. I use this all of the time now with my clients.
 

mickevh

Distinguished Member
I couldn't agree more. I blame Top Gear and Tool Time ("more power") for propagating the belief the "shouting louder" fixes everything. I've often used an analogy of a college I worked at - if I go to the student bar on a Friday evening when everyone is drunk and yelling at each other, I can barely hear what the person next to me is saying. But if I head to the "quiet" hall in the library, literally a hundred kids are having conversations simultaneously as they are all whispering to their neighbours.

On big deployment, I maintain that you know when you've got "enough" AP's when they start to dial down their transmit power.
 
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Kristian

Well-known Member
mushii and mickevh know their onions so the only thing I'll add is that you really need to get on site and survey it. Less is more with wifi so you might even find you only need two APs (ceiling mount one in the kitchen and one in room 2/3).
 

Ptenisnet

Active Member
Thanks all, things are a bit clearer now

I think I’m going to try AP in rooms 2 & 4 first and play around with the power to see how much signal I can get in the adjacent rooms and I’m going to still lay the cables in them should I need (it doesn’t cost much at this stage of construction)

With redundant cables, there’ll be quite a lot of them - do people just label, bunch them together & hide them behind the rack? Or is there any other way to make them ‘tidier’?
 

Ptenisnet

Active Member
mushii and mickevh know their onions so the only thing I'll add is that you really need to get on site and survey it. Less is more with wifi so you might even find you only need two APs (ceiling mount one in the kitchen and one in room 2/3).

Yes I think that’s the wise thing to do, I’ll start with 2 or 3 APs, assess and add where necessary. At least all the cables are in place should should I need.
 

Kristian

Well-known Member
With redundant cables, there’ll be quite a lot of them - do people just label, bunch them together & hide them behind the rack? Or is there any other way to make them ‘tidier’?

One would usually terminate all the cables onto a patch panel and label accordingly. When you need to use one one would then 'patch' it into the switch (using some short, bought patch leads).
 

mickevh

Distinguished Member
...I’m going to still lay the cables in them should I need (it doesn’t cost much at this stage of construction)...
I did that for a school once - I argued they should have an "AP in every class room" but they didn't want to spend the money as they were effectively doing a "soft launch" and were only going to be using a few rooms to start with. I managed to persuade them to at least put in the cabling for "an AP in every classroom" whilst it was a building site, thence in future all they needed to do was buy more AP's and hang them up.

I think in a SOHO install "an AP in every room" would be serious overkill, but if you don't mind the expense of the additional cabling, then it won't hurt to install the extra cabling during build (though your architect might have some views about the fire stopping and so on.) You might even consider extra cables for phones, TV, CCTV and basically anything else that might one day need a data connection and doesn't physically move. The more you can get onto wires, the more it frees up "air time" for the Wi-Fi devices. (And wired ethernet is much faster and more reliable.)

Don't obsess over "signal" strength unduely; it's certainly a factor that "matters" but it's nowhere near as important as newbies think it is. It isn't as simple as "more signal (from the AP) equals more data." For example, a quiet high quality signal can often convey more data than a loud noisy (as in distorted) one. And never forget that the radio signals travel client-->AP as well as client<---AP. No amount of playing with the power setting in the AP will do anything to affect the client-->AP transmissions, though the client devices may employ their own tricks to try and eek out the battery life.

Personally I'd just let the automation deal with setting the Tx power in a managed fleet rather than trying to outthink it myself. For a small install, I'd devise my own channel plan (and fix it) set up the SSID name and passphrase and then just suck and see for a few weeks.
 
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D

Deleted member 24354

Guest
This is actually a situation where you may find LR-APs useful because they also have a higher gain on their receive side of the aerial as well as slightly higher power on the transmit side. Again its hard to know. I have been known to put APs onto long flying leads to try and work out best placement at first fix. I know its kind of extreme but with challenging buildings it is sometimes the only way to work out optimum placement
 

Ptenisnet

Active Member
Just heads up for anyone waiting for the U6-LR they are now in stock in EU store. Been waiting for weeks.

FYI I ordered the U6-Lite a few weeks ago from EU store, you pay the pre-vat web price and dpd will charge vat 20% + £5 processing fee prior to delivery
 

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