Wireless Access

Hi community.

I have to comply the following requirements for an AP:

• Each antenna gain must be at least 2.3 dBi at 2.4 GHz
• Each antenna gain must be at least 3.4 dBi at 5 GHz

I was checking the datasheet for Aruba 330 Series Access Points:

https://www.arubanetworks.com/assets/ds/DS_AP330Series.pdf

And we can find the following:

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AP-335/IAP-335
-Four (vertically polarized) integrated 2.4 GHz downtilt omni-directional antennas for 4x4 MIMO with peak antenna gain of 3.8dBi per antenna.
-Each 5 GHz radio chain has both a vertically and a horizontally polarized antenna element; AP software automatically and dynamically selects the best set of elements for each data packet transmitted or received.
-Four integrated vertically polarized 5 GHz downtilt omni-directional antennas for 4x4 MIMO with peak antenna gain of 4.9dBi per antenna
-Four integrated horizontally polarized 5 GHz downtilt omni-directional antennas for 4x4 MIMO with peak antenna gain of 5.7dBi per antenna
-Built-in antennas are optimized for horizontal ceiling mounted orientation of the AP. The downtilt angle for maximum gain is roughly 30 degrees.
-Combining the patterns of each of the antennas of the MIMO radios, the peak gain of the effective per-antenna pattern is 1.6dBi in 2.4 GHz and 2.5dBi in 5 GHz.

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I do not understand the RF hardware engineering inside the AP-330, but according to the datasheet, can anybody explain me if AP-335/IAP-335 complies with the requirement and what are the values of each antenna gain at 2.4 and 5 GHz?

Is there a scheme that depicts the internal hardware of the AP in order to understand what is said in the datasheet?

Thanks in advance

So this is a tricky one to answer. If you just read the summed antenna gains, we would not meet the requirement. The summed gains are kind of complicated (but relevant as far as FCC certification is concerned). Most antennas from any vendor will reflect much lower summed gains over the rating of the antnenna compared to peak gains. If you look at peak gain, then we would meet this requirement. 

But the thing to note is that with any MIMO AP, there are also MIMO gains that should be accounted for. In a 4x4 AP, it's an additional 6dB of MIMO gain on top of the antenna gain (10logN where N is the number of spatial streams/chains). So not sure if that is something you want to account for. 

Hi Jerrod,

Thanks for your explanation. As you say, it is a tricky question.

• Each 2.4 GHz MIMO radio has 4 vertically polarized antennas.
• Each 5 GHz MIMO radio has 4 vertically polarized antennas and 4 horizontally polarized antennas.

The requirement refers to "each antenna gain", it does not say "effective per-antenna gain", so I think, the AP complies the requirement.

About the additional 6dB of MIMO gain, I would really appreciate an explanation about how to arrive to that result according to the hardware and spatial structure (spatial streams and chains).

Regards