11-18-2014 09:05 AM
We currently have both 2.4GHz and 5 GHz antennas for our AP-175s. How high should we place the AP-175s from the ground? How can we calculate this from the azimuth/polar chart?
Also, are v-pol antennas installed on the top of the AP-175 and the h-pole antennas installed on the bottom? I'm already aware about the R1 and R0 radios for 2.4 & 5GHz on the AP-175. For example, if we install an AP-175 very low to the ground. Wouldn't it be better to install the H-pole antenna on the top of the AP-175 and the V-pole antenna on the bottom since the H-pole has a broader signal that can reach higher areas of coverage.
However, If we install the AP-175 up high on a building, then shouldn't we install the V-pol on top and the H-pole on the bottom of the AP-175?
Are these antennas considered low gain antennas? (5dbi) Low gain antennas have a broader vertical coverage than a high gain antenna (flatter vertical coverage).
5GHz: Omindirectional antenna
The E-plane is 29 ° (Vpol antenna) 33° (Hpol antenna)
2.4GHz: Omnidirectional antenna
The E-plane is 30° (Vpol antenna) 25°(Hpol antenna)
11-18-2014 12:45 PM
It does not matter whether H or V is on top or bottom.
The beamwidths are exactly the same - they are designed to match on purpose otherwise they could not be used together for MIMO. Baseband processing & recovery of the individual spatial streams occurs upstream from the individual radio chains.
FWIW, the V-pol is a standard end-fed colinear dipole type, while the H-pol is a magnetic dipole type. This allows you to flip the polarization but maintain the pattern shape.
As for mounting height, please see pages 41-46 of the Aruba Outdoor MIMO Networks VRD. There is a charge on p43 that deals with this specifically. It uses the D607 antenna as an example, which has a 60 degree BW versus the 30 degree you are thinking to use. So you'll have to update the math but everything you need is there.
11-19-2014 05:47 AM - edited 11-19-2014 06:07 AM
There is a reason Aruba sells V-Pole & H-Pole antennas for AP-175s. These antennas are directly connected to the AP-175 (screwed on, no pigtails) I was hoping to get clarity on the scenario I mentioned.
The CWNA and the book you referenced "Aruba Oudoor MIMO Networks VRD" talks about fresnel zone calculations for point-to-point LOS shots. I'm very familiar with those calculations. I wanted to figure out how to calculate how high should I mount an (Access Point) but CWNA and the book you referenced does not explain that. For example, a typical 3-story building has an access point installed half-way up to cover "outer" floors 1-3. However, another installation might install the access point on the roof or the first floor and expect to cover "outer" floors 1-3 near windows. NOTE: Outdoor installation scenario.
Is this just a guess? I thought there might be a formula we can use.
If the building is 30ft tall and the elevation plane is 33°=Bada Boom bang= Hang it 23.3ft :)
I'm going to say the antennas I mentioned are low gain.
11-19-2014 08:55 AM
So if I am following you the proposal is to hang an outdoor AP onto the same building you plan to cover, serving indoor areas from outside?
In general we don't recommend outside in coverage due to structural losses.
An AP directly outside a building will not open up sufficiently to cover more than one floor of that building. People who try to do this stand the APs back from the building to be covered by a good distance - typically tens of meters for this reason. You see this a lot in resorts to provide internet access to hotel buildings.
On page 43, I am solving for distance of 3dB beamwidth to the ground from the tower. You can use the same solution - in your case the height is simply 1/2 of the height you are trying to cover. you can then solve for the minimum standoff distance you need to achieve that width.
If I am off track, can you please provide more information on your scenario?
11-19-2014 09:24 AM - edited 11-19-2014 09:29 AM
I understand absoption will be an issue. We have access points already installed indoors. The access points mounted outside the building will be for outdoor coverage beyond the building (Not specifically for that building). However, there will be some RF signal that will bleed into the building. Which is good for users near the outdoor AP. That is where I would want to know the height of a mounted AP based off of the elevation plane 33°. Imagine, splitting a circle from the side of a building (looking at it as vertical not horizontal). That half circle will represent the RF coverage beyond the building. The other half circle going into the building will be mostly absorbed but still leak some signal in the building. The signal going into the building does not concern us because we already have indoor access points.
If we wanted to cover building (A) using AP-175. We would mount an AP-175 at a different location for maximum coverage, not on building (A). That is not what we are trying to do. I just want to know the predictive RF coverage based off the elevation plane and optimal height for that AP.
Can you send me a link for page 43?