multiple radio usage

[jesse_ccwis]

Hi Everyone,
Our work is planning in creating a city-wide wireless connection and becoming a WISP. We have in the past had experience in connecting far distant companies via wireless b/g. Our plan is to build our own access point with a wrap board and hopfully take use of StarOS.

The original plan was to use 3 radios. Two used for point to point to connect to other access points and then one omni-directional. After doing some more research I realize that it is not going to be very decent using just the single-radio style setup.

So I understand I have to have at least a backhaul for this to work somewhat more decent at all. This is where I am getting a little confused now. So say I have 3 wireless g radios, am I going to need 3 wireless a radios to couple with the other radios for the backhaul to work? And would this mean I need 6 antennas? I have yet to see an access point though with 6 antennas... One thing I have always thought though was that wireless a had a smaller coverage then that of wireless b or g. But during my reasearch I have read from a few sites the benifits of the 6 radio access point. I have always read that there is others "tasks" you can assign radios to other then being the backhaul or "main connection".

Anyways, I have a lot running through my head on how I am going to make this work. Any suggestions or help is greatly appreciated!!! :)

Thanks,
Jesse

[tog]

You don't need one backhaul for every single AP or anything like that. One backhaul can feed an entire site, even if the site consists of multiple WAR boards. (You can connect multiple boards together via ethernet.)

Speaking generally, using a WAR4 with four radios you can do an example setup like:

1 backhaul coming in from any other Internet-connected site
2 APs using appropriate type sector panels (whatever width and frequency you decide to use, 5GHz/11a is always nice if you have a tall tower and good line of sight)
1 additional radio could be used for a PTP link to feed another remote tower site

Or you can use an omni or two omnis.. though I have to tell you that sectors are way better than omnis.

[jesse_ccwis]

Thanks Tog for your quick reply. Here is another question. Say you have 2 access points. Do you have to bridge the backhaul too then when connecting to other APs? How does a wireless g card (with no wireless a support) connect at full duplex to a AP if the backhaul is wireless a? Is it just a configuration file that tells the radios what task it has (backhaul, access, ptp, etc)?

And last, is there a reason for having more then one access radio? I notice in your example, you have 2 APs. Does this help reduce the traffic even though all traffic has to go through the same AP anyways? OH, and then in your example, how many antennas would you use?

Sorry for all the questions....Can't really find the greatet how-to guide...

Thanks again!

[tog]

Think of the wireless interfaces like ethernet interfaces. If you are familiar with building a network which includes separate routed segments, this should help you draw a picture of how to set a system up. You don't want or need to bridge each 11g mode AP to an 11a card.

A very simple example:
wpci1 is your 11a backhaul, it has 10.0.0.2 assigned to it, the wireless card in 11a mode at the other end of this link has 10.0.0.1 assigned to it. Your default gateway to reach The Internet is 10.0.0.1.
wpci2 is an 11g AP pointed east connected to a 180 degree sector panel antenna
wpci3 is an 11g AP pointed west connected to a 180 degree sector panel antenna

Each radio is only capable of a certain amount of throughput and also if you don't use omnidirectional antennas (like I said, sectors are much better) you will need multiple radios to cover a 360 degree area.

One radio attaches to one antenna, simple as that. Your wpci1 backhaul would be a highly directional high-gain antenna.