Planning WLAN in places with many users

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Jun 20th, 2007
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Hi!


I am about to plan a wireless network on a school with 800 students. My thought was to design this network in a combination of 802.11a and 802.11g due to issues regarding bandwidth, inteference and channel planning. Is the Cisco 802.11A/G AP's able to run these to technologies simulaneously and theoretical obtain a speed of 54Mbit/s x 2?


Any other good suggestion on planning wireless in schools`?

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srosenthal Wed, 06/20/2007 - 06:04
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In order to get 54Mbit/s x2, that would imply being able to get the .11g and .11a nic card to load balance.


The AP with dual radio's will actively use both nic's, but again, I do not know of any that can load balance over both at the same time.



Seth Rosenthal, CWNE #55

ericgarnel Wed, 06/20/2007 - 06:06
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Are you planning to use The Lwapp or autonmous solution? In your environment, the lwapp solution (WLC + WCS) would be a good fit as it would provide for dynamic channel/power/noise management. Keep in mind that a uses OFDM modulation while b uses dsss/cck - g also does dsss/cck as well as OFDM; dsss/ck will provide better coverage than OFDM.


Also B & G use 11 channels, 3 of which are non-overlapping, while A has 23 available.


Your best bet is to focus on AP count & cell size rather than speed. This will allow for radio load balancing, failover, etc. Also, several of the Cisco APs have b/g/a that can run b/g/a simultaneously.


Also keep in mind that the 54Mbits is bitrate rather than speed and that the bitrate and speed over wireless are affected by distance, interference, obstructions, phase of the moon, what paris hilton is doing, etc....


We have 90 1020 APs covering 600,000 sq ft and 5 Vivato panels covering 280,000 sq ft (which will be replaced by Cisco APs this summer).

Our biggest obstacle was getting a wire to where we wanted the APs mounted.


Do a site survey, of course, but also make note of where people congregate AND, a big factor... where accessible power outlets are located. We see it all the time, people camped out by the power outlets to plug in their laptops. Most site surveys don't tell you the social engineering part, but in your environment and mine, it is a huge factor.

In your site survey, also try to determine if you can get data and/or power to where you want the AP mounted and if it is within ethernet spec. Bring an electrician along to get an idea of where & how much conduit you will need & labor involved.

Rob Huffman Wed, 06/20/2007 - 06:23
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Hi Eric. Excellent info here plus a good laugh as well :) 5 points for sure!



Thanks,

Rob

frengky Wed, 06/20/2007 - 22:21
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Hi!


I am planning to use the LWAPP solution.


So I guess that a WLC can handle noise management, AP load-sharing or clients and so on?


I am also responsible for designing the LAN and are working with the electrician engineer who are planning all the power out-let.


Are there some way you can deny access to clients who is not able to get a proper connection (i.e a lower limit of 11Mbps) Just to make sure your are not degrading your WLAN micro-cell.


Will an AP using 11a and 11g simultanously appear as one common SSID or will there be one SSID for 11a and one for the 11g?

ericgarnel Thu, 06/21/2007 - 04:58
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Yes, the WLC can do that. You can define global templates for APs for many things such as power, load,RSSI,max connections, etc... global templates for controllers too.

You can also configure AP settings (once it registers with a controller) for the same as above, as well as wlan override, external antennae (AP model dependent), etc.

Not only that, but if you use the WCS, you can pull up a web interface that shows you the heatmaps with all sorts of good info.


Yes, you can disable bitrates, alter power, etc.

You can have a common ssid for b,g & a, or you can divide them up. For one event, I had a ssid called "internet" just on the b radio -g was disabled, and another called "internet5G" just on the a radios.


My goals are coverage and user load. Bandwidth is not important and we massage it down with policy-maps, nbar, policing,voodoo chants, etc...

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