Wireless on a big meeting Room

[jorge.s]

Hi,

I'm looking at implementing Wireless in a meeting room with about 17m per 17m, and I'm thinking about using the 1231 Accesspoints with AIR-ANT5959 antennas in the false ceilling. Do you know how many antennas in maximum I can put in such a room? How many channels can I overlap? what is the distance which such antenna will cover?

I'm looking at having a very good coverage, since we can have there many users.

Thanks for any help you can give me.

Jorge

[robert.wright]

When considering this implementation you will want to compile a small list before getting started. Likly rob and the otehrs will add several more lines to this, however i hope this gets you off to a good start.

1.) How many users am i going to serve?

2.) What areas am i serving and which am i not?

3.) What are the bandwidth considerations?

4.) Are other APs covering this area and if so what channels?

1. The maximum amount of users you want to shoot for per AP is 20.

2. If you are serving a room 17x17(55ftx55ft), a single AP will likly cover the entire area however it may not be ideal given bandwidth requirements, number of users, environmental conditions or possibly your APs bleeding into an area which you do not wish (IE parking lot)

3. When considering bandwidth, this determines your cell edges. If you want to serv 54mb to each laptop your cell size is going to much smaller than if you were to deliver 11mb. Thus additional APs MAY be required.

4. You will want to at the very least use a tool such as kismet or netstumbler to see what other APs if any are in the area to ensure against co-channel interference. Obtain a spectrum analyzer if possible, such as the Spectrum Expert by cognio. This very well not be the best one on the market however its one that i have used and liked.

802.11b/g, the non overlaping channels are 1,6, and 11. You could serv 33/162mb to an area via 3 APs using the non overlaping channels however each client will still only recieve 11/54mb.

The distance any antenna will cover is govern by several aspects. However the main aspects are the environment, the power setting you set on the AP, and the gain on the antenna.

You can have several antennas in the area given that you keep the power down :) Certain high gain directional antennas will allow you to place several in close proxmity of each other. Google ' cisco antenna guide '.

ok ive written enough that i likly left out a point i brought up earlier so Rob or the others, will likly slap my hand ;)

[jorge.s]

THanks a lot Robert, it really guide me through what I need, but of course I've another question.

Considering that it is just an empty space, and the office has around 3 meters tall, I cannot have more than 4 antennas? How do I know what will be the coverage of an antenna 5959? If I introduce 10 antennas more likely I will have issues with the channels right?

Is there any way to see if a certain antenna will have a circle coverage of 3 to 6 meters, or something similar? Considering that I don't have yet any antenna to go there an make a Survey.

[robert.wright]

http://www.cisco.com/en/US/products/hw/wireless/ps469/products_data_sheet09186a008008883b.html

The above link shows the radiation paterns of the different antennas offerd under the cisco brand.

Im goign to seperate your questions apart and answer them.

Considering that it is just an empty space, and the office has around 3 meters tall, I cannot have more than 4 antennas?

You very well possibly could if you set the power on the AP different. The cisco APs has a power setting of 1-100mW which will increase and decrease the cell's size.

How do I know what will be the coverage of an antenna 5959?

Please refer to the link i pasted at the beginning of this post. You can get an idea of the radiation pattern from there. If your asking how far can this reach, most people throw out the number of 300ft/~100 meters. This is purely theory.. Its just a fact with wireless that even if i have a room the exact size here at my facility, the RF while having similar behavior will be different.

If I introduce 10 antennas more likely I will have issues with the channels right?

If i am doing the meters to feet calculation correctly, i would believe in a small area such as this, i believe you would def have some co-channel interference. And i would also expect your clients to hop around alot.

Is there any way to see if a certain antenna will have a circle coverage of 3 to 6 meters, or something similar?

Thats a rather small cell... If you dropped your power down, i imagine you COULD get it that small. Going that small on your cell size will end up with you obtaining more APs.

Considering that I don't have yet any antenna to go there an make a Survey.

Honestly, no. However, you can look at what APs are presently in your environment and decide at this point if you should plan your wireless to be 2.4ghz or 5ghz.

One recommendation i will make if its a multi-story is to use a ANT24120. Its however not as easy on the eyes though. :)

Also check this book out.. You can find it via safari as well as in the book stores.

802.11 Wireless Network Site Surveying and Installation

by Bruce E. Alexander

Publisher: Cisco Press

Pub Date: November 09, 2004

Print ISBN-10: 1-58705-164-8

Print ISBN-13: 978-1-58705-164-7

[ethiel]

Robert has some great insight he has offered. I will add just a bit of my own experience.

I have not seen you mention how many users you expect, but here is my experience from a large classroom environment. I have a classroom with ~130 wireless users at any given time. I have 3 APs in the room since any more than that running b/g would almost certainly generate interference. Now I often find I peak over 40 users on one AP, but in this case not many are active at the same time, so the users seem to bear it. In a conference room I would expect similar, where everyone comes in, boots up their laptop and logs in then closes the lid for most of the meeting. If this is the case, I would suspect 3 would be a good number to balance out load with interference. If your number of users will be 50 or less, you could probably get away with 2.

If you do find you have a lot of active users, the best thing you can do is encourage them to use A capable radios. Because 802.11a has 12 non-overlapping channels, you can have up to 12 APs that have A enabled, compared to 3 for b/g. In the classroom I mentioned I will likely deploy one or two APs with the G radio shut down just to service A clients.

Hopefully this provides some additional insight into some of your options.

-Eric

[Rob Huffman]

Hi Jorge,

Robert and Eric have given you some really excellent info here so I won't add too much. (Robert and Eric you both get 5 points from me).

We have used 1231's with 5959 antennas in a 1:1 ratio and they work great. I would think that your original thought of 3 AP's with the 3 5959's will work well in the room you have described (as indicated use non-overlapping channels 1,6 & 11 for 802.11b/g).

Hope this helps! And good luck!

Rob

[jorge.s]

Ok. Let me know if you agree or would recommend something differenet, from the following config:

- 3 AP's with the Antenna 5959 distributed in the meeting room, using 'b/g' and 'a' technology enabled using the 3 different 1,6,11 channels. With also 'a' technology enabled, using 5145 Antennas on 2 of them.

- 1 additional AP with 5145 antenna, to cover only 'a' technology, and any additional speed issue.

- 1 AP with normal 4941 and 5135 antennas on a corner on a closed room, used for small meetings due to the possible high density of users. With 'a' and 'b/g' technology enabled.

Shopping list:

5x AIR-AP1242AG-E-K9 (or 1232?)

5x AIR-PWRINJ3

3x AIR-ANT5959

2x AIR-ANT4941

2x AIR-ANT5135D-R

3x AIR-ANT5145V-R

[Rob Huffman]

Hi Jorge,

I quite like your design, but of course not being there to see the actual environment is a limiting factor (normal caveat!!).

I think I might delete the one stand-alone 1242 with the 5145 antenna and just piggyback the 5145 (802.11a) on the last one of the 3 distributed 1242's, just to save a little money. I like the fact that you have chosen diversity antennas for a deployment like this due to the likelyhood of obstructions (people).

Try to mount the antennas at a height that is not too low and you should be good to go!

Just my two cents.

Good luck!

Rob

[robert.wright]

list looks good, i would do what Rob recommends but keep the other AP. Either for onsite swap or to utilize the hot-standby feature.