Ekahau RW AP power ouput values

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Does anyone know what the power output values of APs in Ekahau SS PRO are?
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Primož Marinšek, AlphaDog

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Posted 4 years ago

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Bill Burns, AlphaDog

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Do you mean their site survey tool? (ESS?)

I haven't used it, so I'll guess at your answer:
Any laptop based survey tool depends on the "RSSI" data provided by the wifi adapter it's using.
If you buy ESS, it should come with an "Ekahau NIC-300 Wi-Fi Adapter" but it's compatible with others.
http://www.ekahau.com/wifidesign/ekah...

There's no standard for calibrating RSSI from a wifi card and wifi cards can put out very different numbers from each other.
If the site survey tool isn't configured to know exactly what the RSSI values from a certain card mean and how to map that to dbm (decibel differences from a milliwatt) values, then all bets are off.

Does that answer your question at all?
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Primož Marinšek, AlphaDog

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No, I'm talking about what power level must I set on a particular Ruckus AP when I want to perform a predictive site survey. I need to input the right power output for the virtual AP. The default value is 25mW for both bands which is wrong probably
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Bill Burns, AlphaDog

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Ah. I think you need EIRP values.
This is different per AP.
That information can most easily be found on the Ruckus Product Guides, conveniently hidden away here:
http://a030f85c1e25003d7609-b98377aee...

Maybe Keith could find us a better link to this on the Ruckus site somewhere.
(I wasn't able to find it)

Unfortunately, you seem to need this in mW and the product guide presents it in dbm.

So... take each dbm value and... um...
mW is 10 to the power of (dbm/10)

So... a 7982's 2.4Ghz power is 34dbm which is 10 to the 3.4 which is...
2511mW
Hmm.. That sounds high (slightly higher than a class-1 cell-phone) certainly very powerful for a wifi device.
The same math gives me 1584mW for the 5Ghz band.

You might want to check my math here:
http://www.rapidtables.com/convert/po...

Is that what you were looking for?
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Primož Marinšek, AlphaDog

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What that RW table of APs is showing is MAX EIRP, not what is allowed in a specific country.

There's a much easier way of calculating how much a certain dBm is in mW actually. For example take those 34dBm. You get to that by subtracting 2 times 3dB from 40dBm rigt. So 40dB - 3dB - 3dB. 40dB is 10.000 (count the zeros). So 40dBm is 10.000mW or 10W. Each 3dB less devides that by factor of 2.

So the first 3dB means 5000mW and the second 2500mW or 2,5W and there you go.
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Primož Marinšek, AlphaDog

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Thanks for the answer Bill , however I do know what dB an mW means actually. I have learned that quite a while back.

And I know exactly what EIRP should be for my country, however EIRP is regulated and is a max power output. An AP must regulate it's power output as it must combine it with antenna gain.

In the end I was thinking that maybe 25mW is an OK parameter if we take into account that my regulatory allows max 100mW. If we take into account that APs have up to 6dBi gain than that's just about right, but that's a max value that is achievable maybe 30% of the time (not all patterns have this much gain probably). So now I'm thinking to use 50mW to strike some middle ground, but some guidance would be apreshiated.
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Bill Burns, AlphaDog

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This is a planning tool then, right?
So it's about the kind of AP you plan to deploy.

If you use a value of 50mW transmit power then that means you're expecting 3dB worth of line, connector and "other" losses to end up w/ 100mW EIRP on a 6dB antenna.

3dB of losses sounds like a lot. (especially assuming your antennas are integrated or connected directly to your AP)
You'd be much safer with the 25mW transmitter-power figure.

I figure connector losses (for RP-SMA?) to be someting like .2dB at 2.4Ghz, and .4dB at 5Ghz.
If you assume connector losses weren't accounted for when calculating the gain of your antennas, then to overcome that you could bump your transmit power up to 26mW in the 2.4Ghz band and maybe 27mW in the 5Gig band.
(if your APs have that kind of resolution in their power output)

You aren't using antenna cables, right?
If you were, you could do a calculation to compensate for those losses.

..but does your software really simulate those losses?
Probably not.
That means sticking w/ 25mW transmit power, or 100mW EIRP.

In fact, you might want to simulate w/ less than 100mW EIRP to give you a margin of (coverage) safety in your plans.

--

Wow. 100mW legal limit?
That's less than a "standard" linksys device in the US. (at about 250mW)
..and 100mW EIRP?
Sounds like a pretty severe limitation.

There's regulation limiting most wifi devices to 1000mW in the US.
Ruckus gets around that by way of it's directivity. (that type of system has higher limits)

I don't know what country you're in but if you were using the Ruckus gear that I use here, you'd have to manually configure each AP to be "down" by 14db. (for a 7982)
... and the most my controller allows me to adjust down is 10db.

So.. you either don't (can't?) use the 7982 there, or the 7982/controller that's sold in your country is a different version. (to meet a 100mW EIRP spec)
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Primož Marinšek, AlphaDog

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Yes, ESS is among other things a planing tool.

I'm implementing a WLAN network. I did the SS on site, now I'm filling the gaps with virtual APs. I have to guess attenuation of walls which I can do to a fair degree since I've done the SS, however I have another variable which is the output power. NOT EIRP, but the power of the amplifier before the antenna. I'm using only RW APs with integrated antennas, not any kind of external antennas. But don't worry I'll figure something out, I just thought that someone had a good suggestion for power setting in ESS.

--

We can use 7982 and any other RW AP here, no problem. I just use the regulatorry setting in the GUI.
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John Olsthoorn

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As far as I know, the controller and AP will bring the power down to the allowed levels for your area when you have selected the right country when you configured the system. So you do not need to adjust the power level yourself as long as you do not use separate external antennas.