Question about Antenna Gain

Rajesh Kongath · ‎11-04-2007

Dear Frends,

Could any one can explain me the usage of "Antenna Gain" field in Cisco WLC software v4.2 (Go to Wireless > Accesspoints> radios >802.11b/g/n Cisco APs > Configure - page in Gui)

if i'm using an 2.2Dbi cisco antenna, which value should i mention there? 2.2 or 4.4 ?

Anybody can suggest me any white paper or any documents regarding the mentioned page ?

Thanks in advance

Raj

john.preves · ‎11-04-2007

You would use the gain of your antenna, 2.2dBi.

Just because there are two antennas does not mean the value doubles. The other antenna is for diversity purposes; in the event a signal recieved is weaker due to a host of reasons, the other antenna is exactly 180 degrees out of phase of the first antenna and would most likely be in a better position to receive the strongest signal.

With diversity on, the AP constantly determines which antenna would be the best antenna at that moment in time to recieve signals. They flip on and off all the time.

The only way to increase gain would be to use a higher gain antenna. Depending on your original intent and your surrounding environment, this does not necessarily equate to better; sometimes it equates to worse.

You type it in so the WLC knows what you stuck on the end of the radio so it can act accordingly, supposedly.

dennischolmes · ‎11-04-2007

John is correct here. What you need to understand is that WCS RF mapping services are based on a predictive agent and the heatmaps you see are plotted based on the transmission power plus antenna gain minus the attenuation you assign to the drawings walls. All three of these variables are required to have an accurate vision of the network. The goal is to build a symetric powered network offering good coverage to all areas desired. Equal EIRP to the client device is very important in designing your network so using high gain antennae can actually hurt your network.

Rajesh Kongath · ‎11-05-2007

Thanks John and dennis for ur quick response.

I think you mistaken about my question, i understood the concept of diversity. but below the diversity field there's a field called Antenna Gain, where we have to mention the antenna gain. the confusing part is, they mentioned " x 0.5 dBm " over there. what does it exactly means. suppose if i'm usign an 2.2Dbi antenna, should i give 2.2 or 4.4 (since its multiplying by .5)? pls see the attached image to make it more clear.

I couldnt find any documents regarding ap configuration in cisco support site, anybody can recommend me a good reading on this specified subject?

Thanks alot for sharing the information

Raj

Rajesh Kongath · ‎11-05-2007

Thanks John and dennis for ur quick response.

I think you mistaken about my question, i understood the concept of diversity. but below the diversity field there's a field called Antenna Gain, where we have to mention the antenna gain. the confusing part is, they mentioned " x 0.5 dBm " over there. what does it exactly means. suppose if i'm usign an 2.2Dbi antenna, should i give 2.2 or 4.4 (since its multiplying by .5)? pls see the attached image to make it more clear.

I couldnt find any documents regarding ap configuration in cisco support site, anybody can recommend me a good reading on this specified subject?

Thanks alot for sharing the information

Raj

dennischolmes · ‎11-05-2007

Got it! Yes use times 2. If the antenna is a 6.5db gain put 13 in the box.

Rajesh Kongath · ‎11-05-2007

Thanks dennis - could you please advise me any documents on the requested matter ?

regards

Raj

dennischolmes · ‎11-12-2007

Look at the configuration guides for WLC Controller Code.