High Density Wireless Deployment

Unanswered Question
Aug 15th, 2007

We just tried a wireless deployment in a large room with 7 APs serving 120 wireless laptops. The clients came with all different laptops and wireless cards. We use WiSM and this deployment was not successful. Some clients got problem to connect the network and some experienced disconnecting problem. For the clients not able to connect to the network(wireless network not responding), usually a "repair" fixed the problem. Any ideas? Anyone tried the similar high density deployment with success?



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Overall Rating: 4.3 (3 ratings)
chris-marshall Thu, 08/16/2007 - 04:59

The issue you're running into is related to channel utilization. You could try tuning each radio down to it's lowest power setting, and ensure that you have properl channel placement (no overlapping channels between cells). If that doesn't work, you'll need to look into what are called pico cells. Cisco controllers are able to handle this pico cells, but because of the unique RF nature of pico cells, you'll need to first talk with TAC, and more than likely bring in an expert. A good example of a pico cell environment would be the NYSE floor. Due to the high density nature of the floor, the RF consultant company that did that job needed to design pico cells that were only a few feet in radius, radiating up from the floor. The accomplished this by using attenuators and finely tuned RF channel and power settings. With luck, you won't need to go this far.

ericgarnel Thu, 08/16/2007 - 05:20

Just out of curiousity, since we have a high density deployment,

How did you set up your power levels - auto or on demand?

Also, what APs & antennas did you use? and were there obstacles and/or rf interference to contend with. The reason I ask, is because we face the challenge of deploying wireless in a dynamic environment that changes almost on daily basis. We to have to deal with the issue of windows PCs sometimes not connecting. An interesting note, the problem rarely occurs on macs and Linux. In fact, during a recent troubleshooting situation, I booted my dell into both XP sp2 & ubuntu 7.04. Ubuntu not only had less issues, but had a better connection with the same radio & environment

chris-marshall Thu, 08/16/2007 - 05:37

For high density environments, you should always avoid auto. High density environments are a lot like voice over 802.11... they just won't work unless you perform a proper site survey. We have two high density environments here... one is a warehouse like environment that is constantly changing due to inventory levels and product density changes in the shelves. In this case, some APs are operating at higher power levels, and some at extremely low levels to provide small, focused, cells. Keep in mind that for a high density RF deployment, directional antennas are your friends. You'll need to pay attention to signal propigation patterns, and that's a lot easier when you can point the signal like a flashlight, rather than radiating out in a big flat circle like an omni directional antenna will. Our other deployment is a large conference room frequently full of wireless voice and data users. We went with half a dozen cells at the lowest power level, radiating upward from the tabletops using small directional antennas fixed beneath the conference tables. It's worked quite well.

Rob Huffman Thu, 08/16/2007 - 05:26

Hi Guys,

Chris, very interesting/informative answer here! 5 points from this end for your good work.



zhenningx Thu, 08/16/2007 - 09:01

Thank you for all the replies. We were using auto power/channel adjustment. Also among the 7 APs, four of them are 1131 APs with unidirectional antennas and three of them are 1231 APs with directional antennas. So from my understanding from the replies, the auto adjustment is the main problem.

Thanks again!



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