Motorola MC9090 handhelds and 7363 Access Points with Zone Director

[michael_daracz]

I have 4 motorola handheld guns roaming between 6 overlapping 7363 access points with Zone Director 1100. The guns are running a simple wavelink telnet application. They are sitting on a separate open WLAN with no authenticaion but with an MAC ACL. Intermittently, the guns are having problems re-establishing a link to the access point(bars that indicate signal strength go from full to none, and the handheld indicates that it lost connection with the server), even though they are within the range of them. It doesn't happen often but its annoying enough. It usually takes 10 - 20 seconds to re establish a link. What settings should I check? Thank you!

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[primoz_marinsek]

"We have 8 AP's in our ware house they are about 15-20 meters apart mounted on the roof, the roof is about 10 meters high. Is that too far apart? Should we get more?"

I think that's your problem right there. Unplug 4 of your APs and I things should get better straight away.

[primoz_marinsek]

Well first you disabled OFDM, which should drop minimum bss rate from 6 to 1Mbps, so the disablement of bss-minrate shouldn't have changed anything. But I don't know what an AP actually does in this instance.

Minimum rate of OFDM is 6Mbps (11g). If not enabled minimum rate is 1Mbps (11b).
By rasing min-rate you try and help the 9090 to change AP at a different time, i.e. distance from the AP. What I think others here are probably thinking is that maybe the 9090 are roaming either too much or too little and that's causing issues.
So we've told you to raise bss-minrate to 12, 18, 24 or higher to provoke 9090s into a roam at a better time (read: distance from AP), however you need to be careful because you actually don't shrink AP cell size with that, just the distance a 9090 will still connect at so you 'trick' your 9090 into a roam and hopefully another AP is there with enough signal to give the handheld 18Mbps when it decides to do that.

This however is highly dependent on what your 9090 does. Since you are using archaic handhelds things probably won't work as you'd expect and enabling OFDM only and raising min-rate will probably not change anything, like you've found out.

Another thing is how APs are placed. They might be spread to thin or too close. Either way you can run into problems. That's why proper installers take allot of care in designing a WLAN network. If they are smart, they even document stuff and give you all the measurements and everything.

The only thing that would make sense in this case is your DTIM setting which if I understand is helping, which is logical since that's rate-independent.

But there are greater and greater benefits of using OFDM. It has to do with the speed that some frames are transmitted at, cell-sizing, roaming, etc. Too much for this post, but the general rule now is to use OFDM only with higher minimum rates. Not applicable everywhere, but like 95% of implementations.

[julius_kisieli1]

Funny story that, our site was "professionally surveyed" and my apologies for some confusion we are not even using Motorola's we are actually using Touchstar Boston 8500 of Belgarvium fame, I am not sure if anyone is familiar with the company?

But the hardware is new but the OS is Windows CE 5.0 and network cards prefer to run in B only even though they are capable of G, we have had to use a registry setting to make them go to G.

I think that the network cards and OFDM disagree, I will give it a try but I don't think the technologies are compatible.

[primoz_marinsek]

11g is OFDM (ERP-OFDM to be exact). The problem is most likely in the drivers that implement that, which is nothing new especially with handhelds and/or Win CE.

Define "professionally surveyed". I've seen a 100 professionals that survey with eyes and at most an InSSIDer.

[julius_kisieli1]

😉 Perhaps slightly more sophisticated than eyes only. They came in with an access point that they set up in various places and something that looked like an over sized tricorder from star trek, then they told us we will need 8 evenly distributed through our warehouse. No map, no readings, so here we are today.