You should not put access points in hallways. It’s a rule.
In today’s rules for efficient Wireless LAN design, we’re going to talk about why you should not put access points in hallways and give you some examples.
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Do not place access points in hallways
It’s a rule
In this little short training video, we’re going to
talk about why you should not
put access points in hallways
and give you some examples
It’s part of the Wireless LAN Design Rules series
Let’s get started and just talk
about why people want to put access points in hallways
Part of the reason was a long time ago
decades ago actually
people want to put APs in hallways because
what we thought Wi-Fi needed was a lot of coverage
We wanted to cover a big area
and we put them in the hallway
we could see that AP from a long ways away
and we thought we were getting something really good
and they were easy to do
It was easy to put in hallways, easy to get access
The problem is it doesn’t work as good
as you think it should
We’re going to give you some examples inside Ekahau
so you can see the difference of what happens when
you use an AP in a hallway or
when you don’t use an AP in a hallway
Hopefully at the end of this little video
you’ll feel a lot better about not
putting your APs in hallways
Well to start, we have an access point
and it’s sitting on top of a football field
Now, I picked an American football field
because a pretty easy to do work in
You can go and take an access point, put it in the middle
and every line is about 10 meters, 10 yards apart
And so you can see if we take an access point
that’s an omni access point and it covers in all directions
That’s where it’s supposed to do
If you look at the coverage pattern
and I’ll come over here and do so
And we can come over here and detail out
and see that the coverage pattern here,
you can see that it’s omni in the azimuth plain
It’s putting out a circle
We can also see on the football field
when you place it there in proper orientation
It covers the entire football field
60, 70 meters in every direction
that’s where this access points been designed
So starting here with no walls and nothing around
you can see it covers a long way
Next up, we’re going to switch up and look at
what happens if we take that exact same access point
and put it in a small medical clinic
Here’s one access point in the medical clinic
I’ve already added walls in areas
and I just want to show you that it’s no longer circle
It was, you saw the exact same access point
Same height, same power, nothing changed,
and I moved it and just put it here
Now what we’re seeing is Ekahau is doing this little math
What it’s doing is it’s taking the signal strength
coming from the AP, pushing it through the
pattern of the antenna and then doing
freespace loss calculations, covering distance
And then when it hits a wall, looking at the wall material
looking at its RF loss and changing the angle of how that
degradation or attenuation is taking place
So we have both freespace loss, degradation
and you saw on the football field
there’s not a lot of that
But here in the Medical Clinic, you can see
the walls are controlling it as well
So if you put an AP in this medical clinic
and you put it in the hall, it’s going to have a long tail
We used to think what we wanted was a lot of coverage
What we really want is controlled coverage
So if I take this exact same access point and I just move it
so it’s not in this hall and it’s not in this hall
I’m just going to move it up and over out of the way
Now, it still covers the area that it was covering before
these rooms in the corner, but it lost its tails
Now, here’s one of the reasons we don’t want tails
We move it back into the corner and you’ll see that it has tails
That’s, you know, like that coverage
Or you might say, well, I have voice over AP
And so I walk down the hall, I want to have good coverage
And then when I turn the corner
I want coverage from a different AP
That’s true
But if we walk down here and say, I was right here
at the end of the hall about to turn
and right now you’re getting oh, sorry
little glass this time we’re getting a 58
So right there, there is absolutely
no reason whatsoever for you to roam
You’re getting a great meg 58
But if I just walk a little bit further
and if I bring in my ruler tool, you can see that
where I was getting a 58 if I walk 1.3 meters away
What’s that take half a second to walk
maybe a second at the top
If I just move 1.3 meters away from here
and now I’m over here
and now my signal dropped down to 68
Do I need to roam?
No, depending on how the client’s been programmed?
Maybe, maybe not.
As I turn that corner, though, there is probably another
AP that’s going to have better signal there
And as I turn the corner
I’m going to have to have a quick change
How about if we look up over here
right here before I turn the corner
I’m getting, a 54
Again, no reason whatsoever to change
If I again just walk from this corner and I go down
let’s say I walked 2, 2 1/2 meters down
and look at the coverage
Now, I was a 54 and within 2 meters away I dropped to a 78
At a 78, I’ve got to roam
Well, how much time did I have to do that roam
As I turned the corner, boom, I instantly have to roam
Watch what happens when we just move the AP
out of the hallway and back over here
Now, right here, as I’m nearing the corner, I’m getting 66
I walk a little further, I’m getting a 68
And as I turn the corner,
I have this slow loss, not instantaneous
I have enough time to let the client device go
Oh, I’m lowering my signal
Perhaps I should start looking
and then I start looking and then I have some time
I don’t have the quick instant loss
as you turn around the corner
Every time you put a AP in a hallway
you’re going to get that kind of effect
Now, let’s look at some other places
where you might put in AP in hallways
Because that’s what you’ve always done
Let’s look at a Hotel
So here’s a hotel
And if we only put in two access points
One bottom left, the other one up at the upper right
We have fantastic coverage in the hallways
APs in the hall give great holiday coverage
The problem is that’s not
where the people use Wi-Fi in a hotel
They need to use Wi-Fi in their rooms
Well, this doesn’t do a very good job
It barely covers two rooms
So if we look at it and say
well let me come and add some more APs
Let’s go and add an AP and let’s put one right here
And see if, oh, I can get one more room and right here
and get another room and right here
I can get another room
And if I did this continually and I have so let me jump ahead
and show you this is what it looks like
if you put AP in hallways
You can get really decent coverage
Let’s come over here and look at the statistics
and you can see statistically
We’ve got, what, 98 percent coverage
of the areas of all the rooms by sticking with the halls
You can use a AP in the hallway to cover signal in the rooms
That’s not like all the Wi-Fi rules, if you break the rule
it doesn’t mean Wi-Fi doesn’t work
it’s just not a matter of efficiency
So let’s come back and say
I don’t want to do AP in the hallway
How could I do it more efficiently?
Now, in this one, with all these AP in the hallways
we used a total of 24 AP
So you can see up and left corner here
we use twenty four APs
If I switch up and say no, I don’t want that
I want to put AP in the room
Now, we have only used 10 APs, less than half the APs,
and we achieved a better result
Now, the reason for that, and this is true not just in hotels
but in many hospitals, schools, other places
the walls on both sides of a hallway
are usually load-bearing
Meaning they’re more dense material
meaning they stop the RF more
The walls between rooms, between classrooms
between hall room, hotel rooms
or hospital rooms are less dense
They have lower RF attenuation, so it’s easier and cleaner
to allow a single AP to go through multiple rooms
And as you can see, we really used
less than half the APs and achieved a better result
Now, when I’ve talked to hotel operators
like put them in the hallways, why?
Because we always did it, because we have access
and we don’t want you to have to go back in the hotel room
You know what if the AP breaks
we don’t want to lock in the hotel room
And I asked them, what’s the Mean Time Between Failure?
That’s a IT term, MTBF
Of I don’t know, a dirty towel and the like
Well, once I explained MTBF after when they go well
we change the towels every day
So you’re going in the hotel room every day
and you want me to not put the AP in the hotel room
because our APs have a
Mean Time Between Failure measured in decades?
I don’t think that’s a legitimate reason
And once you explain that, they kind of get over that one
But they’re like, but we’ve done it in hallways before
And as soon as I show them the difference between 24 APs
And I’ve been in hotels, have these happen to be around
5 meters apart or 10 APs
Amazing how fast they switch their mind up and go
Oh, APs in hotel rooms make a lot of sense
So just to recap, if you want to have efficient Wi-Fi
don’t put your apps in hallways and we’ve had some
examples here today to show you live directly in the software
You can see the results
So you can take your own copy of Ekahau
Try this, do a design in the halls, do design, not in halls
And you will see you can achieve better results
Now, there may be times like you’re on a cruise ship
and the walls are made of steel and the only place
you can not, you cannot get access in the rooms
then you might want to put one on a hall
and use a direction antenna and aim it across the hall
and shoot it into the room
There might be reasons to break this rule
Most of the time though, follow rule
Don’t put AP in hallways
If you have more questions
come to WLANPros.com we have a lot more videos
and a lot more training, podcasts, videos, WLPC videos
Glad to have you as part of the community
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