Wireless Access

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Super Contributor II

Coverage in elevator shaft

HI All,

 

I've had a strange request from a client to provide WiFi inside the elevators in high rise building.

 

In principle it sounds doable, get a cable in and mount the AP in the ceiling. The more i think about it the more i think - bad idea.

 

Has anybody ever done this before? What was your experience? My concern is that this would play havoc with ARM / Roaming each time the AP passes a floor.

 

Scott

 

 

 

Re: Coverage in elevator shaft

That is a very interesting request indeed.  Not something I've done before.

 

If the lift is contained in a solid shaft and not one of those glas ones, I don't think you need to worry too much about ARM.  Perhaps just set a static channel and the lowest power you can.

 

Not sure where you would place that AP on an Airwave VisualRF plan though. ;-)


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

ACCP, ACCX #817, ACMP, ACMX #294
Occasional Contributor II

Re: Coverage in elevator shaft

Elevator coverage is always a subject that comes up during design, but rarely is implemented due to extensive costs. Wiring/bridge to the elevators and APs in every elevator would require a good salesperson to seem economically sound for that 30-second ride.  However, if the application is important enough, the price is never too high. Although this should not be the location you place your most expensive APs.

 

As Michael is saying, I would not worry about ARM; with the AP limited to the lowest power, the attenuation through the elevator casing and the elevator shaft should well prevent any interference with the other APs on the passing floors. Naturally, the elevator lobby would be affected when the doors open, so keep that in mind when you design your network.

 

I would however not use static channels for the elevator-APs, as they should be able to move to a different channel if they themselves are affected by noise or interference. Potentially this could cause problems when multiple elevators run inside a single shaft. I would recommend you monitor the channel use and if the APs frequently are changing channels, you could try the static approach. Make sure you analyze the spectrum while the elevators are running/standing at the same floor.

                                                                                                                                                                                                                                           

The typical problem is however how to wire the AP in the elevator. With the maximum allowed length of a Cat 6 cable at 100 meters, you might be short in your “high rise building”. The most discussed option is to deploy a directional antenna (high gain dish/sector etc.) at the floor or ceiling of the elevator shaft or even a similar wireless bridge to the elevator. There is also a few interesting posts on running DSL to the elevators in high buildings on the Whirlpool Forums; http://bit.ly/1kXipuU.

 

Either way, let us know how you proceed. Good luck! :)

 

Jan Vidar

Guru Elite

Re: Coverage in elevator shaft

Yes, ARM becomes an issue when the doors of the elevator open and the signal bleeds out. Many deployments will choose a single channel for the elevator which is not available for use on the floors.

Tim Cappalli | Aruba Security TME
@timcappalli | timcappalli.me | ACMX #367 / ACCX #480
Contributor I

Re: Coverage in elevator shaft

You could use "leaky coax" and run it down the entire length of the elevator.  PLace a 50 ohm dummy load on one end, and a AP-175 on the other.  But, this would be expensive because the coax will have to be a large diameter for 2.4 and 5.8 GHz.  This is similar to whay they do in tunnels.

 

Matt

Frequent Contributor I

Re: Coverage in elevator shaft

If you do decide to go with an in-car AP, be aware that it's pretty tough to find cat6 cables that are certified for use in an elevator.  Due to the constant flex on the cables as the car goes up and down, plus the fact that it's considered a life/safety environment, most cat6 cables can't be installed - especially solid conductor.  As part of installing IP surveillance cameras a few years back, the only good option that I found was Datwyler 191032, which comes in a mostly cat6 option.

 

The "mostly" part is that in order to meet the constantly flex requirements, the cables are smaller than normal - 26 gauge.  This means that they'll only perform cat6 at up to 65m, rather than the normal 100m.  Depending on your cable paths, you may want to consider installing a small switch in your elevator machine room to minimize the cable run length.  In addition, you'll have to be careful about how much power loss is incurred, and what this does to your PoE budget.

 

On the plus side, the cable is a single flat jack about 1 inch wide containing 4 cat6 cords, so a single pull gets you plenty of spares for adding cameras or dealing with a broken cable without bringing the costly elevator service tech in.

Guru Elite

Re: Coverage in elevator shaft

Have you considered doing a mesh deployment? Then you would only need power in the car. No data. Obviously depends on how many floors the building is.

Tim Cappalli | Aruba Security TME
@timcappalli | timcappalli.me | ACMX #367 / ACCX #480
Super Contributor II

Re: Coverage in elevator shaft

Hi All,

 

Thankyou for the great tips and considerations that i didn't think about. This is still in the "can we do it" stage with the customer so no firm plans as of yet.

 

My feeling is the cost will be hard to justify for the benefit.

 

Scott

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