Wireless Access

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Super Contributor I

AP Comparison

Hi guys,

 

I have compared two APs at the Aruba website and this is the output:

 

ap_comp.PNG

 

It is difficult to me understand the parameters Radio MIMO type and Integrated antennas. I understand that 4x4:4 for SU-MIMO means 4 transmit antennas, 4 receive antennas and 4 spatial streams with a single user. Does 4x4:4 for MU-MIMO mean the AP supports 4 simultaneous users?

And why AP-320 has 8 omni antennas and AP-310 has 4 omni antennas if both have 4 transmit antennas and 4 receive antennas (4x4). For my understanding, AP-310 should also have 8 omni antennas.

Please some help for understanding these parameters. Many thanks.

 

Regards,

Julián

Re: AP Comparison

Please check the 802.11ac page for some videos on MU-MIMO. In short: with MU-MIMO you can split the available number of streams over multiple client devices and communicate in the same time to for example 1 dual-stream client and a 2 stream client or 3 single stream clients with the 320 series (4x4:3 MU-MIMO). Note that clients must support MU-MIMO to take advantage of that feature.

For the 310, the 4x4:4 MU-MIMO indeed means that you can have 4 single-stream clients at the same time, or 2 dual, or combinations like 1-1-2, 1-3.

On the number of antennas question, all the antennas are for both receiving and transmitting. According to the specifications, the AP-315 has 4 dual-band antennas, where the 325 has 2 times 4 single-band antennas (separate antennas for 2.4 and 5GHz).

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If you have urgent issues, please contact your Aruba partner or Aruba TAC (click for contact details).
Super Contributor I

Re: AP Comparison

Hi Herman,

 

Thank you for your interest.

For the first part, then the AP-310 can support up to 4 single stream clients and the AP-320 3 single stream clients at the same time. Isn't it weird that AP-310 support more clients than the AP-320 even when the model is lower?

For the second part, did you mean each single antenna is for both receiving and trasmitting or there are separate set of antennas for receiving and another set for transmitting?

 

Regards,

Julián

Re: AP Comparison

The specifications are built-in the chips that are used in the AP and the AP-310 has a different (newer) chip than the AP-320. The 320 can do 4 streams, when in SU-MIMO. I doubt that you will really see the difference in practice as it only attributes if there is actual data to send to enough multi-user mimo capable clients at the moment of the transmission. Don't expect 33% more performance from a 4x4:4 versus 4x4:3 in practice, it might be under laboratory conditions.

 

The same antenna element is used for receiving and for transmission. Remember that wifi is half-duplex, so an antenna will either transmit or receive at a single moment (and the radio can very fast switch between sending/receiving). If an antenna element is a dual-band, which means it is designed for both 2.4GHz and 5GHz simultaneous operations, one of each radio chains are connected to the same element. The 310 has 2 radios, with 4 antenna chains each, where each of the antennas is connected to a radio chain on both radios (with filtering).

From the datasheet of the 315:

5 GHz 4x4 MIMO (1,733 Mbps max rate) and 2.4 GHz 2x2 MIMO (400 Mbps max rate) radios,with a total of four integrated omni-directional downtilt dual-band antennas

From the datasheet for the 320:

5 GHz (1,733 Mbps max rate) and 2.4 GHz (800 Mbps max rate) radios, each with 4x4 MIMO support and a total of eight integrated omni-directional downtilt antennas.

 

I wouldn't pick my AP based on these differences or specifications though; there are more important things to look at, like the customer requirements, a possible redundant Ethernet on the 325 or the higher capacity of the 325 versus the 315. Please use your local Aruba SE to help you pick the right AP for each environment and match the customer requirements and budget.

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If you have urgent issues, please contact your Aruba partner or Aruba TAC (click for contact details).
Super Contributor I

Re: AP Comparison

Hi Herman,

 

Many thanks, good explanation. Just two more questions because I want to understand completely this matter:

 

  • The AP-310 has a different (newer) chip than the AP-320.Isn't it weird that the AP-310 has a newer chip than the AP-320 even if it is a lower model? Just for curiosity.
  • The higher capacity of the 325 versus the 315.When you say higher capacity, what do you exactly refer to? Do you refer to higher data rates? Or other parameter? Because the number of supported users is the same.

Regards,

Julián

 

Super Contributor I

Re: AP Comparison

Hi guys,

 

Does anyone have answer for my two last questions for totally understand this?

 

Many thanks,

Julián

Re: AP Comparison

Not weird, the AP-325 was the first 11ac Wave 2 we released, the 315 was released later, when we had more options from silicon providers that were later generations of silicon that were more efficient, better power savings, etc. 

 

325 has dual ethernet, and on the extreme side of client loads (over 100) the 325 is slightly higher performing in our tests. 

 

if you need dual ethernet 4x4 11ac Wave 2, the 325 is it. If not, the 315 is. If you need MAX performance, the 335 is likely better, but if you plan on running over 100 and can't do the 335, the 325 might be a better option than the 315.

 

If it were me, I would be deploying 315 and forgo the dual ethernet and deploy more APs. 

Jerrod Howard
Sr. Technical Marketing Engineer
Super Contributor I

Re: AP Comparison

Clear, many thanks Jerrod!

 

Best regards,

Julián

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