Wireless network design question

You need to do a site-survey, if that hasn't been done. Any consultant worth his money shoud have required and done one for you. Go over the site-survey with the consultant and let them prove to your satisfaction that the design is sound. My two cents!

Doan

I am definitely with you on this. Problem is that we have not even started building out the space yet and they are already buying equipment. I am trying to keep them from buying a ton of equipment that they don't need.

I have done numerous site survey's for wireless deployment and have yet to find a building that requires 180 AP's. Granted, most of the survey's where for small company's of 500 users or less. If you could give me the square footage of each floor and the approximate number of users per floor. I can probably give you a BALL PARK figure for the AP's.

My two cent's-

1) What kind of AP's? 2) How is the consultant going to deal with RF overlap? On most AP's they require their own channel, 802.11b/g they are only 11 channels. This is unless your doing MAC Cloning 3)Has the consultant taken into account that 802.11 is a contention based transmission? Ethernet is the same, however, when it is a switched Ethernet topology, each port of the switch is its' own collision domain, therefore no contention. 802.11 every client on a AP will have to contend for the right to tx/rx 4)Has the consultant taken into account the clients will be freakin' out switching between AP's. Thought, intermittent connectivity failure CITY 5)Number of AP's per floor Based on your comments about the building layout, I would say maybe 4, maybe even aslittle as 1-2 per floor. However, many AP's can only support or service X Number of clients at any one time, some Linksys models limit it to fewer than 50 clients. 6)Has the Consultant considered that going with Cat5e would be cheaper than 180 AP's. 7)Has the consultant considered that any Network Engineer worth his/her salt would prefer cable to wireless Wireless In May Opinion is reserved for mobile users inter-office. It is great for the board room and receiving email via a PDA while walking to the coffee machine.

Chris

Sqare foot 221556'

All floors are equal in size and space. The building is divided into 3 sections. The divider points are round and the elevators and stairs are there.

Hi

Just curious. If you have 1500 users using 11 channels = at LEAST 136 users per channel (some users can roam). Sounds little bit unpractical for 136 users on the SHARED medium. Another thing. If 1 AP gives away 100mW (0.1W) of microwave type of signal, 180 of them will worm up the place ;-) - just kidding. But I wound not want to sit the whole day surrounded by AP's

The whole proposal just looks scary, 1 AP can hold about 30-50 users or so. Even if you use 11g (54M/s) it gives you about 1 M/s per user (I am just speculating here), anyway you users most likely will not be pleased.

Just my 2c Roman Nakhmanson

Since you can't get more than about 30Mbps of user traffic through a wireless link, and some people are likely to get less than the 54Mbps full throughput because of signal quality issues, then it's likely to be much less than 1Mbps/user.

Sam

Hi Sam

you are right, it can be much less. That is why I've wrote "it gives you ABOUT 1 M/s" ;-)

Roman Nakhmanson

But you are assuming a worse case scenario where ALL 50 users are online at the same time, ALL using the FULL bandwidth. In reality, that is rarely the case!

Just my nickel!

Doan

Doan

well, maybe I was not clear enough First - please note "I am just speculating here". Second - do the math if ALL 50 users would "some how" be able to use FULL (as you mentioned) bandwidth (let's optimistically say 25Mbit/s of usefull traffic) - the AP should give away 50users*25Mbit/s = 1.25 Gbit/s (if you can find AP like that - sell it to me please 8-). So, if (just an assumption) 50 users at any given time would use just

0.5Mbit/s each (which is nothing in our modern, multimedia ready, cruel world) - simple calculation will give you total of 25Mbit/s - which is (BTW), reallistic number to get from an 11g AP. Of course users are not working all the time, so maybe 1 user will generate a 0.5Mbit/s and the other 5 will do nothing. But keep in mind that 1 kid watching the news over the Internet + another kid downloading lets say ISO image of FreeBSD 6.1 can bring the AP to the 60-70% of it's capacity really easy.

bottom line - IT ALL DEPENDS

Roman Nakhmanson