Wireless and RF

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Aruba
Posts: 1,287
Registered: ‎08-29-2007

Split Antenna array setup

Hi,

I am going to be deploying wireless to cover some warehousing area that contains long aisles between high shelving. I will be using a split antenna array with two AP-ANT-18 to each point down a different aisle.

My question is really what is the best setup, or what is best practice for this? Should the radomes from each AP cover adjacent aisles, or should I alternate it?

The attached diagram explains it better.

Appreciate any thoughts or advice.

Thanks

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ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Guru Elite
Posts: 21,023
Registered: ‎03-29-2007

Re: Split Antenna array setup


Hi,

I am going to be deploying wireless to cover some warehousing area that contains long aisles between high shelving. I will be using a split antenna array with two AP-ANT-18 to each point down a different aisle.

My question is really what is the best setup, or what is best practice for this? Should the radomes from each AP cover adjacent aisles, or should I alternate it?

The attached diagram explains it better.

Appreciate any thoughts or advice.

Thanks




The answer is C. Neither.

Both antennas on the same access point must provide overlapping coverage for diversity. Warehouses can be areas where there is considerable interference. Antennas must be configured to provide overlapping coverage to minimize that as much as possible. Pointing antennas in different directions can decrease your performance considerably.


Colin Joseph
Aruba Customer Engineering

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Aruba
Posts: 1,287
Registered: ‎08-29-2007

Re: Split Antenna array setup

Thanks Colin,



Appreciate that, but it's not quite different antennas, but more like one split into two. The attachment shows it bit better what I mean. The left and right antennas would point down different aisles.

Is this a reasonable setup? Obviously I can have an AP for each aisle, but just thinking of cost and trying to keep the deployment sensible for the customer.

Thanks


If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Aruba Employee
Posts: 571
Registered: ‎04-17-2009

Re: Split Antenna array setup

I'd say that if these antennas overlap in any way, it will probably cause issues. So, that would denote pointing them in opposite directions. Not to mention, when you use splitters, your signal will be drastically degraded. You'd have to know the db loss of the splitters to boost the AP to compensate.

I'd say just use omnis with no splitters. But that get's into an RF design plan. Talk to your local SE about a good design plan to fit your needs.

Zach
Thanks,

Zach Jennings
Aruba Employee
Posts: 99
Registered: ‎09-08-2010

Re: Split Antenna array setup


Thanks Colin,
Is this a reasonable setup? Obviously I can have an AP for each aisle, but just thinking of cost and trying to keep the deployment sensible for the customer.




With the splitter, you're cutting your transmit and receive signal in half, and sending half that power in each direction. not to mention the power loss from the splitter itself, plus the length of antenna cable for three elements in both directions.

The only valid use case I've seen for using splitters on an AP-12x was to split the 2.4 and 5GHz frequencies out for different antennas, and even that is a marginal use case when there are purpose built APs that will handle that better.

While splitters may look less expensive initially, realistically someone will be back to undo the splitters and install additional APs down the road, so the initial saves will be consumed with man hours re-engineering and deploying proper gear. Warehouses are tough environments to begin with, I wouldn't recommend starting off with one arm tied behind your back due to splitters if you can avoid it.
Aruba
Posts: 1,287
Registered: ‎08-29-2007

Re: Split Antenna array setup

The power loss will be taken into account when provisioning the AP. In the case of the AP-ANT-18, being a gain of 7.5 dBi, this would be provisioned with a gain of 4.5 dBi, or more like 4 dBi to take into account some extra loss from the cables.

I've seen this deployed before and works quite well. It may or may not be deployed like this, just looking at different options.

So my original question.....is it better to have the antennas from each AP pointing down adjacent aisles, or should it be alternated?

If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Aruba Employee
Posts: 571
Registered: ‎04-17-2009

Split Antenna array setup

Michael,
While I understand what you are trying to do, I do not think you will get an official answer. The official answer will be this is not supported.

That being said, and if you understand that this is completely unsupported, I would say alternate, because you would not want the antenna coverage to overlap. But again, I just wouldn't do it.

Zach
Thanks,

Zach Jennings
Aruba
Posts: 1,287
Registered: ‎08-29-2007

Re: Split Antenna array setup

Thanks Zach,

Appreciate the consensus is not do it. Anyone can chuck APs all over the place, but this has an obvious impact on cost, not only on the actual AP cost, but the licencing which may require a bigger more expensive controller.

All options are still on the table at the moment.

:)

If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Guru Elite
Posts: 21,023
Registered: ‎03-29-2007

Re: Split Antenna array setup


Thanks Zach,

Appreciate the consensus is not do it. Anyone can chuck APs all over the place, but this has an obvious impact on cost, not only on the actual AP cost, but the licencing which may require a bigger more expensive controller.

All options are still on the table at the moment.

:)




Like Zjennings said, please contact your local Aruba SE about this. You are at the stage in the design where quite a few small things can either drive up costs or significantly affect the performance of your clients. A warehouse deployment difficulty is probably only second to outdoors in terms of complexity and the detail determines the success of such a deployment. No one on this forum can advise you correctly on your approach for this deployment in a way that will incoporate all important factors into your design.


Colin Joseph
Aruba Customer Engineering

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