MR84 and dual band antennas vs MR74

[MarcelTempelman]

Hello all,

We're looking into a warehouse wireless solution based on Meraki access points for one of our customers. The MR74 and MR84 are candidate access points. What bugs me a bit is the lack of proper documentation on how to combine access points and antennas. For example nowhwere in the documentation of the MR84 can you find if you can use the AP with one or two antennas and if you are able to use it with one, what the benefit would be if you'd use two. As far as I know the MR84 can be used with one antenna based on this 'if' statement in the installation guide:

Reminder: Both 2.4 GHz and 5 GHz client serving radios are diplexed onto each antenna port, so if using multiple antennas it is best practice to aim all in the same coverage area. 

Using 2 antennas in this case makes installation extra complex because you need to align them in a proper way and the construction needed for mounting the aps will be bigger. I'd say the stadium antenna or a 3rd party dual band antenna with 4 leads is a better fit for this access point.

The MR74 can use single band and dual band antennas (will be reduced to singe band antenne on the MR74). So my question is; what is best suited for a warehouse setup? The MR74 of a MR84 ? And if it's the MR84 what's the best practice concerning antennas (1 or 2) ?

Thanks in advance,

With kind regards,

Marcel Tempelman.

[BrechtSchamp]

My understanding is that both radios (2.4GHz and 5GHz) use all 4 antenna connections, basically as an array of antennas. If you don't use two antennas you'll lose some of the MIMO functionality due to the lack of antennas/paths. Similarly if you do use both and the antennas point in a different direction then MIMO will not function optimally and you open yourself up to the exposed node problem. Basically a client would be denied from sending due to someone already using the medium in a totally different area (due to the antenna's facing a different direction).

See also this post by @TylerJ :

https://community.meraki.com/t5/Wireless-LAN/Can-we-mix-two-types-of-antenna-sector-antenna-and-omni...

And also this one by @PhilipDAth :

https://community.meraki.com/t5/Wireless-LAN/Can-we-mix-two-types-of-antenna-sector-antenna-and-omni...

[MarcelTempelman]

Hello Brecht,

Thank you for your reply. What you describe is my assumption also : decreased functionality when only one antenna is in use. We were certainly not planning using the anntennas is different directions because in that case the MR84 should have had an extra radio like the Cisco 3800.

Hopefully someone will update the documents so that we don't have to assume things.

This morning I was discussing the situation with my colleague and I tested some antenna patterns in Ekahau and the MR42E with the 3F antenna (narrow patch) is probably a better option. The 'Universal AP and Antenna Articulating Mount' from Acceltex makes the installation also a bit easier. If the (exptected) warehouse enviroment is friendly for this type of access point than we will go the MR42E way.

Nonetheless I would like to have an official Meraki statement about the MR84 antennas.

With kind regards,

Marcel Tempelman.

[MarcelTempelman]

Hello all,

I got an answer from Meraki : The MR84 can work with one dual band antenna. They did not specify the difference between using 1 vs 2 antennas. When using 1 antenna you need to terminate the unused antenna ports with RF Load terminators (https://www.pasternack.com/50-ohm-rf-load-terminations-category.aspx).

with kind regards,

Marcel Tempelman.

[MerakiDave]

As you stated perhaps the MR42E with a narrow patch is the better option, assuming it's not outdoors and exposed to the weather elements.  On the MR84, @BrechtSchamp  is correct, all 4 antenna ports are dual band and there is a diplexer to separate 2.4 and 5 off of each antenna.  While you could use the MR84 with a single antenna (assuming you use the proper terminators on the other 3 ports) I wasn't clear why that would be advised, as it's significantly defeating the purpose of a 4x4:4 AP.  Perhaps you've got a special use case where it applies, but generally speaking you'll want to use two patch or two sector antennas per MR84 and orient them in the same direction. 

[MarcelTempelman]

Hello Dave,

thank you for your reply. The APs will be placed in a warehouse and it depends on the enviroment if you can use indoor access points. That's why we looked at the MR74/84 in the first.

The MR84 is a bit strange in my opinion:

- it is a top level access point (in my opinion) with only 1 radio per frequency (compared to the Cisco 2800/3800)

- there is no Meraki dual band (sector) antenna with 4 leads

- the construction with 2 sector antennas is quite big and i'd prefer a single antenna in front of the AP. Having 2 anntennas next to each other (vertical or horizontal) will increase the coverage angle. This is why I wanted to know if the AP works with 1 antenna and what the impact would be. The 4x4:4 functionality is nice but not necessary for aisles with one or two handscanners.(there is also no documentation on the mounting of both antennas; I asume they need to be mounted at least 5" apart).

It seems the MR84 is designed for omnidirectionals in mind not with directional antennas.

For now the MR42E is our best option (unless we need to adapt to an harsher enviroment).

with kind regards,

Marcel Tempelman.

[MerakiDave]

That's correct @MarcelTempelman the MR84 has 2 fixed radios, one for 2.4GHz and one for 5GHz, it does not have an XOR radio to support dual 5GHz if that's what you were referring to. 

Also correct that there isn't a Meraki ANT part number with 4 leads, so on an MR84 you would use 2xANT-25 dual-band patch or 2xANT-27 dual-band sector antennas for example.  Each of those antennas is dual-band 2x2.  For an antenna with 4 leads, the 4x4 Aironet AIR-ANT2513P4M-N antenna is also supported, but that's a larger panel antenna for HD deployments like in stadiums, perhaps not ideal for warehouse aisles.

Thanks for pointing out the documentation not mentioning proper antenna separation, I'll bring that up to the documentation team.  Ideally directional antennas would be at least a few wavelengths apart, so I wouldn't suggest placing them right next to one another, might be more aesthetically pleasing but definitely less effective.

I've designed several MR84 deployments with directional antennas like 25/27, but more typically in outdoor stadium type deployments and a few other use cases.  As you said, for warehouse aisles, and wanting a single antenna element, and not needing 4x4:4, I agree with your direction to go with MR42E and likely either the E5 wide patch or F5 narrow patch antenna.  Note the narrow patch is physically a larger antenna, much larger than the size of the AP, which might be a consideration but that's just the physics of a narrow patch.

Regards,

Dave

[MarcelTempelman]

Hello Dave,

thank you for your extensive reply. You answered a lot of my questions I had. I hope we win the deal. I look forward doing a large scale Meraki wireless infrastructure . Until now it has been Cisco Enterprise only. 

With th kind regards,

Marcel Tempelman. 

[brad1]

We have 14 MR32's about 3 years old now in our shop and warehouse abut the size of 2 football fields side by side and they work great for connecting wireless Zebra printers and Intermec CK71 scanguns. Not sure why you would need the extra antennas.

[MarcelTempelman]

Hello Brad,

as they say in the wireless community 'it depends'. What might work in your warehouse might suck in the other. If you have racks which are not filled to the brim or the materials stored are 'wireless friendly' (when looking at attenuation) you can have great coverage with only a few access points. Things get tricky with metal parts or with food. Omnidirectional antennas can be great in offices but can completely screw up your wifi performance in a warehouse.

So it really depends...

Here's a great video about Warehouse WIFI:

https://www.wlanpros.com/resources/warehouse-wi-fi-francois-verges-glenn-cate-wlpc-phoenix-2018/

and this is a great blog post on why chosing a different antenna can make a big impact:

https://blog.theitrebel.com/2018/08/27/warehouse-wireless-design-ideas/

With kind regards,

Marcel Tempelman.