Antenna Booster

[ziggy1621]

hello all,

i've got a client who has a setup where we are getting a good wireless signal (i can connect to the Bellsouth modem at any time), but not getting good throughput (web surfing is not constant).

Here is the scenario.. A dlink dwl-7100ap (http://www.dlink.com/products/?pid=304) is mounted about 15' up the outdoor face of one of the buildings (these are metal buildings.. I know not smart, but he wanted to do it and is willing to pay for it). That is my router. About 75' away, I have a DWL-G710 Range Extender (http://www.dlink.com/products/?pid=357) with an ANT24-0800 (http://www.dlink.com/products/?pid=52) on it mounted on top of a small building (approx 12' high) with clear site of the router. Then about 100' later is another dwl-g710 range extender in the upstairs window of his office.

Now again, we are getting good signal. At any time I can ping the main router, so its going through the range extender's, but I'm loosing a lot of throughput.

My question is how do I find out what kind of antenna boost/dBm I need to get the throughput "up to speed"

thanks in advance

[M/Q]

You probably are not going to get any better bandwidth with the setup you have. Not knowing if the dwl-7100ap is hard wired or not you are talking about at least three hops with two repeats. Each repeat will cut bandwidth in half. So if you are getting good signal strength and not perfect you are also reducing bandwidth a certain percentage. Lets say you are running 11b, and even 11g would be down to 11b bandwidth at those distances. So that is 11mb/s in a perfect world. First hop, you are down to 5mb/s. Second hop you are down to 2.5mb/s. And third hop you are down to 1.3mb/s in a perfect world. I bet it is even less than half of that.

That is not that great of a distance, I would get two access points with directional panel antennas on each and have them act as a bridge link. You already have one AP, and if you want wireless coverage in the office it would require three AP's total.

Like this:

Bell Modem
|
|-Ethernet cable
|
- DWL-7100 with directional antenna
....<<>>
....<<>> Wireless bridge link
....<<>>
....DWL-7100 with directional antenna at office
......|
......|- Ethernet cable
......|
......- DWL-7100 acting as AP in office.

Your throughput under perfect conditions would be approximately 2.5-5.0mb/s depending on the exact topology. Also just to make sure you understand, there is no way any improvements in antennas will help significantly. If you use this suggestion it would be best to have the bridge link channel and the AP channel in the office be as far apart as possible. Like channel one and 11, as that will reduce intererence.

[ziggy1621]

Thanks for the reply..

Although I did get lost in your first calculation. I'm running in G mode, so that is 54Mbs, if it gets cut in half on each repeat, then thats initially 54, cut to 27, then cut to 13.5 which should still leave room for error of getting down to the 5.0 max you were talking about in your scenario.

correct me if I'm wrong.

ziggy

[M/Q]

I guess I did not make it very clear. It may advertise 54mb/s but it ain't getting anywhere near that. On a single hop with perfect signal conditions you are at most getting 27mb/s, due to management overhead and the fact that wirelessis simplex.

Then when you add any kind of distance your signal strength is going to be weaker and 802.11 rachets down bandwidth in accordance with signal strength. From experience I can say that any hop of 75ft has it down to 802.11b bandwidth.

Think about it, what is your cable modem running at? Lets say at most 3mb/s and if you were hooked up to that directly you would not have any problems. But you are, so logically the throughput bandwidth will be much less than 3mb/s. My DSL is 1.5mb/s and I have no problems,so hopefully that cleared it up.

Also because of the metal buildings and omni-directional antenna in the middle you are most likely getting multi-path signal bounce. That in most cases has a negative effect on the signal strength, that is why I suggested using just two directional antennas that you can aim and obtain maximum signal strength.