Hello everyone and welcome to the third installment of our Encore wireless section.
In this section we're going to be talking about how to place your APs to get the best
coverage and things to keep in mind when you're dealing with your APs.
This is a really short lesson but a very important one.
Placing your AP in your environment is all about maximizing the signal without leaking
outside of the bounds of your building.
Remember we're dealing with a signal that it can be picked up by anyone.
So having it extend beyond your physical walls, having that wireless signal shoot out into
the street, not really a good idea even with security and stuff in place.
You really don't want that wireless signal going too far out of bounds.
So let's go ahead and dive into how this actually works.
Now one of the first things that we're going to talk about within the wireless AP placement
is the AP effectiveness.
Where can I place an AP to make it the most effective?
And the first thing you need to know is the closer you are to the signal, the better the
signal.
And that doesn't seem like too much of a stretch.
You can see we have a higher PHI rate, P-H-I.
Now the PHI rate basically means the physical rate, that's what it stands for.
And all that means is the bit rate of the actual data.
The closer you are to the center, the better you are.
The further you are away, the worse it gets.
Now this is, the size from here to here is dependent on what technology you use.
If you use 2.4 GHz, that has a lower data rate, but it travels farther.
So the data gets further, further.
Now if I use 5 and 6 GHz, this is much shorter.
The effective rate of the data is much shorter, but you get much more data in that area.
So there is a definite trade-off as you go up in technologies to how far your wireless
access points will be able to deliver bit rates.
Now that brings up this, the actual design and placement.
We now need to ensure coverage in our building.
In order to ensure coverage, we have to have what's known as overlapping circles.
You see how we have kind of like a Venn diagram.
This is our cells, each one of these is called a cell, and we want them to overlap.
We want them touching because I don't want a person like right here who has no wireless coverage.
I want wireless coverage throughout the entire building or the entire floor.
So that means I want these to be overlapping.
I want the cells to look more like this, so that there's no free space in between.
There's no place where you're not getting wireless coverage.
And how we do that, and how we implement that, it depends greatly on the antennas we're using.
Are we using omnidirectional antennas?
Are we using directional antennas?
The best way to do this, the best way I've found, is start at the edges.
If I have a room, let's do a room here.
I have a room, and I place my AP here, and I place my AP here, and I place my AP here,
and here, and then I have an AP here, and here, and one here.
Well, now I have full coverage.
What I can do is I can start filling in.
I can say, oh, I need coverage here, and here, and here, and here, and here.
And I just kind of honeycomb effect all the way in the middle.
But by starting at the edges, I can ensure that I work my way in.
Now it's important to realize, remember when we talked about those different channels,
we want to make sure that adjacent channels are different.
If I didn't have an adjacent channel, let's say up here, where it's 64, I'm going to cross
that out and put 116.
So I have two 116s that actually overlap each other.
What am I going to have?
I'm going to have a ton of interference right here.
That's not good.
We want to make sure that the channels are different.
Remember, we're using a smaller band of the frequency.
So I'm not going to get any interference when I'm using 64, 116, 36, 48.
None of these are touching.
It would be okay if I had a 36 here again because it's not touching the area or cell
that has channel 36 running.
I'm not using the same frequencies.
So that even though it's five gigahertz or whatever I'm using, remember we're using those
20 to 22 megahertz bands within this range that gives me that difference or that little
bit of uniqueness in my band.
So I'm not creating interference to other ones that attach to me.
Now remember for client density, you're going to want to pay attention to this.
This differs on APs and antenna types.
Client density, how many people are sitting here?
That's going to determine a lot.
How many different SSIDs you're using?
How is your wireless LAN controller placement?
Who needs to be on what SSID?
How do they need to roam?
All that stuff is going to come into play later.
We're going to have a discussion of that in architecture.
But when we're talking about basic coverage, when we're talking about an AP and its placement,
this is what I want you to think about.
Start at the edges, fill your way in.
How many people are sitting there?
That's going to determine the number of APs you need as well.
How far will people be sitting from an AP?
Are they sitting here?
Well then that's not good.
They don't have enough coverage.
They need to be closer or I need to add yet another AP to make sure that they have the
coverage they need.
Or even this, maybe the speeds are not enough.
Remember our signal to noise ratio.
Remember how we need a certain level of signal in order to make VoIP work.
If I have a VoIP customer who's sitting here but they're only receiving a signal to noise
ratio of 20 dB, is that going to work?
Absolutely not.
Remember I need a little bit of higher version of my signal to noise ratio.
I need 25.
So either I need to move this person in closer to the AP or I need to add another AP that
makes them close enough for this to work.
Focus on my drawing there for a second.
So this is a very important aspect of wireless.
You know a lot of people get away with wireless because they just keep throwing up APs without
a plan.
Don't be that administrator in your environment.
Really take the time to plan it out and do it right.
So that's all I have for this lesson.
Very short and sweet but very important.
This is the one that's going to determine the signal strength that your users are going
to experience.
So spend some time here.
Make sure you understand everything we've done thus far has built upon the placement
of these APs.
It's now an easy topic to discuss but it relies on all that information we talked about before
and a little bit of planning on your part.
I'll see you in the next one.
Bye for now.