I'm looking for any material, i.e., whitepapers, texts, webinars etc., that talks about capacity planning in a practical sense.
For example I would like to know how many users I can adequately accommodate on an 802.11g AP. The performance I am looking at, for the users, is 512kbps for non-real-time data (i.e., email, web, file servers). The theoretical TCP traffic limit for 802.11g is 24.4Mbps, however it is not as simple as dividing through by 512kbps to get number of users.
How does the shared medium handle more and more users?
What delay are users going to experience, will this increase with amount of users?
If I have a noisy environment, of which there are one or two I am aware of, then if I enable protection mechanisms and fragmentation how does this affect the capacity?
Any help, or a push in the right direction, would be appreciated.
I was just wondering as to what is your level of knowledge about WLANS ? CWNA level ,CWSP level or CWNE level ?
Because some of the stuff that you asked is covered under the CWNA like
If you are talking about 512 kbps per user, then even the least data rate will work i.e. 1 mbps.
So in your case you might not have to worry a lot about the cell size. (If a higher throughput was required per user e.g. 2mbps, then you typically would be required to use a smaller cell size than you would have if the required throughput was 512kbps )
You should be able to accommodate 30 users on a single 802.11g AP safely if 512kbps is the required throughput. Well, in theory you could even have 100 users associate to an AP with extremely extremely light usage.
But I think I remember reading in my cwna manual that 25 users per AP is the optimal limit (with not very high throughput demanding users or appz), because with more users the latency is going to increase a lot as the wireless medium is going to be busy all the time.
Protection mechanisms will increase the overhead and decrease the throughput. But sometimes when there is lot of noise , this decrease in throughput is well worth it as you might have a much less throughput in a very noisy environment with all the collisions and back offs with only DCF and no RTS/CTS enabled.
It is the same thing with fragmentation, if you decrease the the packet size, it will cause a decrease in throughput because of the fragmentation protocol overhead, but there will be much lesser collisions and hence more resilient to interference.
And for whitepapers, you don't need to look too far. There are loads of them on cwnp.com.
This is one that I had read regarding DCF / PCF if you want to take a look .
Go there and you'll find loads of whitepapers some or many of which cover things that you asked about.
I hope this -> post helps
In my experience, a lot depends on the product. That being said, in an environment with low usage users just doing email and basic web surfing, an AP should adequately handle around 25-30 clients. You mention file servers; as long as you do not expect heavy sustained downloads, you should be good to go in this range. Also, you cannot really dedicate bandwidth per se as WLAN's are a shared medium. Also, the more you fragment the lower your overall bandwidth. You will need to test the environment to find a custom solution. Sorry I can't be any more of a help on that issue. Good luck!
I'm not sure about the rules about posting other websites but the other day I found a capacity planning tool by VeriWave (excel format) on the following website: http://julioanguita.wordpress.com/2008/09/26/aplicaciones-para-entendidos-freeware/
I have played around with it and it looks like a very useful utility.... Hope it helps :D