Deciphering wireless

[KWestos]

Hi, we are using Zyxel wireless switches with access points (dumb) which is a complete managed wireless system we put in earlier this year. We have recently realised that some of the access points need to be moved as they have a range of about 120 degrees. What I want to know from some wireless experts out there is what the following screen grabs mean. I have used Network stumbler and inSSIDer to monitor the same access point at the same time. Do these images look ok? The network stumbler program shows the access point in green then a few seconds later in yellow (is this ok). I am no expert in wireless (obviously) and just want to know what these readings mean.

 

 

Many thanks

 

Karl

screen grabs.doc

[matt40k]

Looks alright, I think. I think it's just "normal" wireless traffic "noise"

 

dBM is on about the strenght. -30 to -90 how interesting lol.

[KWestos]

dBM is on about the strenght. -30 to -90 how interesting lol.

 

What would you expect it to be. The laptop was directly next to the access point

[matt40k]

Well it goes to, if it's legal +20dbm (UK legal limit). So I would guess so. Not being a wireless expert.

 

Assuming I understand correctly. You're not getting as good a signal... I assume someone locally has put up a wireless access point or some other such device that has affected it.

[Ric_]

I've been having some randomness going on with some of my APs of late... I'm going to do some investigation using a Wi-Spy because I suspect that there is some interference going on.

 

EduGeek has an offer available on these at the moment at http://www.edugeek.net/forums/recommended-suppliers/24738-cheap-wi-spy-devices-edugeek-members.html#post236951

[KWestos]

I have just changed one of the channels from 11 to 6 and the dmb has gone to +30. Is this making any sense??

[HodgeHi]

If you have two access points in proximity of each other and they are both on the same channel then there will be interference.

 

According to a site survey i had done, they say if you have access points that overlap they should be on different channels.

 

As for the rest of what you are on about i've no idea.

 

If i rememebr right you should use 1,6 and 11. They are further apart and thus less prone to interference.

[matt40k]

Look up the freq of the channels..

 

I think so are close.

 

1 and 12

 

some can get interference on some channel.

 

Ask your LEA, there networking guy should know these things!!

[KWestos]

Our setup is a blanket coverage so all the access points can be on the same channel. We use ZYxel 81600 switches with NWA-8500 access points. So we have free roaming without loss around the school (in theory).

 

Just wondering if anyone else had this setup

[Richie]

Having all your access point on the same frequency is generally not a good idea. We have wireless across all our site. All our access points use the same SSID and encryption settings. Any access point that is within range of another is on a different frequency. In fact, following advice from a D-Link engineer who site surveyed our school recommended using only every other available channel as the frequencies are so close that two nearby AP's on channels 1 and 2 for example could cause interference with each other. (Depends on the AP and surrounding environment)

 

We do use the same channels on more than one access point but they are situated at opposite ends of the site and are nowhere near each other.

 

It is worth checking if you can detect any 'other' channels in use from nearby houses or other buildings and then avoid those as well. We have a line of houses that runs along one side of our site. There are a few Ch6 and Ch11 devices (these must be common default channels) so we don't use those channels along this side of our school.

[KWestos]

Hi Richie

 

Our access points are basically dumb terminals. Our main wireless switches can only be on one channel at any one time. The access points plug into the main wireless switch and take all the settings from their (minimal configuration). The only issue we have is that we have two wireless switches, so in theory we can have a maximum of two channels even though we can connect 16 access points (8 on each).

 

It is a corporate blanket coverage.