Questions about overlapping wifi access points

Solution 1:

First I add that some of these replies need clarification.

There are two kinds of overlap, one is channel overlap where the frequencies overlap, and the second being signal overlap.

You MUST have signal overlap for all devices to have coverage in all areas, or even most devices in most areas.

Secondly, there are various schools of thought for frequency overlap and some manufacturers even suggest putting all APs on a common channel. In the case of roaming IP phones this case becomes even stronger as a phone may hop across APs while in a call. This of course depends much on the hardwae of the phones and antenna placement and design.

Let us assume that we had a large open area that we wanted wifi coverage in. Now lets take a pole and place it in the middle of the area. Now we place 4 directional 90 degree antennas on the pole, each 90 degrees from the other . In this situation one may make a strong case for having all APs on the same channel to facilitate roaming. In theory there is little signal overlap but all frequencies overlap.

Now we have an open area with walls on four sides. and place an AP on each of the four walls. The signals WILL overlap from each of the 90 degree antennas , so we may want to consider using separate non overlapping channels on each AP , however there are only 3 non overlapping channels. 1, 6 , and 11. So instead we do the best we can in North America this might be 1, 4, 7, and 11 , each AP having SOME necessary frequency overlap. Of course in a perfect world this might be better accomplished with three APS in a triangular configuration.

In my home I have toyed with APs on Same channel and separate channels and in the end I see little coverage difference., I do see however that some devices such as wireless IP phones can more easily hop to another AP while in a phone call. I see that in most areas I do not have more than 2 overlapping signals and each on channel 4 at present. As I sit here I can launch wifi seeker on my android and see either of the 2 available APs and even connect to either. This of course is easier to test with separate SSIDs but more practical to use common SSIDs fopr everyday use.

Solution 2:

From past experience working with these sort of networks, I can offer the following:

• No, I don't believe your standard consumer-grade APs will have any sort of load-balancing. there are options out there, like Cisco's wireless solution (for the right $$$) that can do things like this.

• In areas that are hard to cover, you may need to look at different antenna configurations or simply adding more APs. This will require a bit of work to determine the right balance, as adding too many will affect performance as well. You may want to get some wireless mapping software to help you determine the signal strength in these areas, as well as overlap. A stronger radio will not help if it cannot 'hear' the Iphone; for this you will need a more sensitive radio / antenna.

• I believe the client has a lot to do with how this scenario will perform. Normally I think they will simply pick the strongest signal, all things being equal. Multiple APs on the same channel will interfere with each other, but you will probably need to do testing to see how bad the situation really is. Drops and collisions are expected in wifi.

• When/If budget allows, you might upgrade to some commercial grade routers. These shouldn't need nightly reboots, and will probably perform better under higher loads. You may also want to look into 802.11n if you aren't already. (iPhone 4S supports the 2,4 GHz 802.11n, the iPhone 5 adds support for the 5GHz band of 802.11n)

hope that helps somewhat... ?

(in a previous life I did support around 50 Cisco APs in a hospital setting... we never had much problem with overlapping or slowness, as long as the channels were spaced out as they could be)

Solution 3:

I set up and maintain a set of wireless APs for a mobile IP phone system in our factory. In order to facilitate roaming, the AP radios have to overlap enough to get a good signal from one of them at all times in the transition zone. So long as the AP radios are on well-separated channels they work well.

This IP phone network fully overlaps a separate wireless data network. The installation, which I wasn't consulted on, placed each phone AP one foot from each data AP because it was convenient for wiring. Each AP is at least half the channel range away from its "partner" so there is no frequency overlap.

This hasn't created a problem. (Caveat: They're Symbol APs which are rather expensive and may not compare well to sub-$100 APs.)