Hello. In this video we’ll be looking at designing our office-based environment to meet our capacity requirements.
Now, as we know, the corporate network could have up to 70 users across the floor, and the business’ most demanding requirement was for voiceover IP, where up to 60% of all users could be on simultaneous voice or video calls. Now, given that this wireless LAN will also be serving data clients, we said that we would design capacity for no more than seven simultaneous voice calls per AP.
So let’s look at this design and assess, does it meet our capacity requirements? And we can see that currently, I’ve got nine access points meeting all my [inaudible 00:01:04] requirements. And my capacity requirements said that I would need, for the number of users that are going to be on simultaneous voice calls, I would need at least six access points.
So, if my users were nicely spaced out across the entire floor plan, these nine access points would definitely meet my capacity requirements. But what I’ve got to look at is is there any areas where a large number of users are all congregating? And in those areas, do I have enough capacity?
Well, the obvious area, as we look at this office plan, is on the left-hand side of the plan, where there’s a large open office area, and meeting rooms and offices around the side, and this is an area where most of my users are. Yes, we have a conference room up at the top here, which [inaudible 00:02:03] users may use when in meetings. There is a smaller office area down here, and then sort of individual single-person offices along the bottom, but the majority of the users in this office are all on the left-hand side. In fact, when we counted the chairs and worked out how many people could be working to the left of the restrooms and stairwells, we got 45 users.
Now, we know that at any one time, 60% of the users could be on voice calls. So, when we work out 60% of 45, that gives us 27. So, we could have, just in this area here, 27 simultaneous voice calls going on. So, if we, one AP with data connections, we’re going to say we can have seven simultaneous voice calls, that means we’d be really looking at having at least four access points covering this area. And how many do we have? Well, we’ve got one, two, and then there’s this one here that’s also helping to cover that area. So, we’ve really only got three access points covering this area at the moment. So, from a capacity point of view, it could really do with an additional access point.
So, let’s go ahead and place our additional access point. Now, the question is, where do we put it? We could just place it right in the center of this open office area. Let’s have it close to where all our users are. And while it seems quite a sensible idea, one thing we have to consider when placing access points is which access points are users most likely to connect to? And by placing an access point directly above this big group of users here, means that most of these users will probably connect to this one access point, and that means we still may end up then having too many users connecting to the same AP.
So, I would prefer, in this design, to move this access point over more over to the left-hand side. By doing it, I’m allowing my users in this area to have multiple APs they may choose to connect to. It might be that a user sat at the desk here would connect to the AP above it. A user sat here is going to more likely connect to this AP, and a user sat down here would be likely to connect to this one. So, all the users are not going to pick the same access point, by spreading them out a little bit more. In fact, if I now hover my mouse over this area here, I can see that there’s a selection of access points, which we can see, all with a signal strength greater than minus -60 dBm.
Having added a new access point into this area, because I’m adding an access point for capacity, I will want to make sure that the 2.4 gigahertz radio is disabled, which it already is on this access point, but I’ll also want to re-establish the channel plan. So, I’m going to just come in here and recreate my channel plan, so the five gig channel plan can take into account this new access point. And then I just want to check that it’s not caused any additional co-channel contention, so I come to my channel interference map, and I can see the five gig plan is still green, so I’m still okay with my 40 megahertz-wide channels. I’m not causing any channel interference, and I’ve now added an extra AP for capacity.
And we can see that my primary signal strength looks very good. I’ve got 100% coverage there, and when I look at my secondary signal strength, it also looks very good. In fact, by adding this extra AP, it’s now even got rid of some of those small secondary coverage issues we had, and we’ve got pretty much 100% secondary coverage too.
And that’s the process we go through when designing an office for a voice grade robust wireless LAN design. Thank you for watching, and goodbye.
VoIP Capacity Requirements
VoIP capacity requirements are normally dictated by the number of simultaneous VoIP calls per AP radio. See Mist's design VoIP guidelines below: