WLAN in Large Engineering factory

Unanswered Question
Apr 9th, 2009

Hi,

I have surveyed a large Engineering Manufacturer who wants to install WLAN on its manufacturing floor. It is very similar to a large warehouse with lots of over head cranes and gantrys. ( I am mounting below these)

I was thinking 1242's or 1250's and was going to mount a total of three AP's across the width of the factory, what antennas would you recommend, I was thinking directional Omnis on the walls facing in on each side and an AP in the center with di-poles in the centre.

They will be running RFID over this set up, please feel free to tell me if I am wrong so far.

Mick

I have this problem too.
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jeff.kish Thu, 04/09/2009 - 07:30

You're correct to use 1240s or 1250s for such an environment. But as for antennas, there's simply no way to know how the signal will propagate without a site survey.

If you don't want to hire someone to do the survey, simply purchase an AP and one of each of the antennas you're thinking of using. Mount the APs where you think they'll work best and check the coverage. Keep the power turned down to 14dBm, full power tends not to work the best in factory environments.

This will tell you exactly how many APs are needed, as well as which types of antennas worked best. Personally, I'd recommend omnidirectional antennas that aren't mounted against a wall. The only reason to do this is if you're performing location tracking via RFID.

terminalvelocity777 Thu, 04/09/2009 - 08:36

Jeff,

Thanks I have conducted a site survey using ekahau and a test AP 1242, what I am unsure of is the mix of antennas.

Do I use the standard dipole ant or a remote surface mounted omni?

I have just looked at the survey and decided just before your post to move the AP's away from the walls.

Mick

Leo Laohoo Thu, 04/09/2009 - 17:47

Hi Mick,

First off, the easy ones. For RFID, I'd recommend AeroScout. The company has made intensive R&D with Cisco. AeroScout has it's own Wireless Location appliance which is very impresive.

Next comes the difficult bit. You need to take note the location and the HEIGHT of the AP to be installed. You also have to understand the way transmission footprint of an antennae: vertical and horizontal azimuth.

Below are very simple yet comprehensive data sheets (with some information regarding azimuth) for various AP's.

To take advantage of the full potential of the 1250, make sure you have the enough input power (18.5 watts).

Cisco Aironet 2.4 GHz and 5 GHz Antennas and Accessories

http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008022b11b.html

Cisco Aironet Antennas and Accessories Reference Guide

http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html

Hope this helps you.

terminalvelocity777 Fri, 04/10/2009 - 01:09

Leo,

Many thanks for the information, I am thinking of wall mounting 1242/50's around the perimeter wall with AIR-ANT2465P-R antennas facing inwards on either wall and AP's suspended on cross beams in the center with dipoles.

How does this sound to you am I making any basic mistakes.

Leo Laohoo Fri, 04/10/2009 - 01:34

Hi Mick,

ANT2465P is OK if you are using the AP1240. Unfortunately you can't use this on the 1250 because of the number of TNC connectors. But isn't the ANT2465P for the 2.4Ghz? What about the 5.0 Ghz range? How does the ANT5170P sound?

For 1250, you can use ANT2430V (2.4Ghz) and ANT5140V (5.0 Ghz).

terminalvelocity777 Fri, 04/10/2009 - 03:37

Leo,

Thanks, I had looked at the 2465P will use the 5170P too, I cant decide if i should wall mount facing in or move the aps out into the floor area a bit and just use dipoles.

scottmac Fri, 04/10/2009 - 05:27

You should not wall mount an omni - it's a waste of (at least) 50% of the energy and can generate its own multipath interference wasting even more.

If you are mounting to a wall, you should use a patch or sector antenna (which radiates some portion of a hemisphere) or a panel (an intelligent antenna with a self-steering pattern).

If you intend to use an omni, then they should be mounted in a (predominantly) open area, if you are using dipoles (a bowtie pattern) then the broadside of the dipole should be oriented to cover a longer, narrower area.

You should also lose the thought of "I'm going to use {some number} of antennas" ... when you don't even know what kind of antennas you are going to use.

You did a survey (or say you did). Take that info to a scale diagram of the room, then fill the room with RF in specific patterns from specific antennas, taking into account the RF shadows, and interfering sources.

If the wireless info is critical in nature, then you also have to assume some overlap and backup, such that if one AP dies, other APs can step up and fill the gaps.

What's the point of doing a survey if you aren't going to use the information it provided?

Good Luck

Scott

terminalvelocity777 Fri, 04/10/2009 - 06:56

Scott,

I didnt say I was going to use a certain number of antennas, I said to Leo I was thinking of using a mix of wall mounted and centrally mounted antennas..so nothing to lose there!!

I have done a wireless survey and I am using it so there is a point, the problem I was discussing with Leo was using wall mounted antennas and specifically what model and if I should move the aps in away from the walls?

Thanks for the input.

Mick

Robert.N.Barrett_2 Fri, 04/10/2009 - 07:08

Here's what looks like a good patch antenna solution (they also have 2.4GHz only and 5GHz only models)

http://www.provantage.com/terrawave-solutions-m6060070mp13602~7TRWV0ER.htm

I would caution against using three of the Cisco patch antennas - you will not be able to space them at intervals of one wavelength or less. According to what I've been seeing, MIMO/diversity works best when the antennas are space at intervals of one wavelength or less.

Depending on how the coverage maps out, I would recommend wall-mounted patch antennas on the perimeter in order to help reduce the RF coverage that extends beyond the facility walls.

terminalvelocity777 Fri, 04/10/2009 - 07:59

Robert,

Thats great coupled with the reply from Leo, the main area I was unsure of was the types of antennas to use especially for the 1250 (never deployed them before)

Regards

Mick

Robert.N.Barrett_2 Fri, 04/10/2009 - 11:14

One word of caution - I think that the 1250 install guide has a specific list of approved antennas with wording to the effect of "other antennas are prohibited". The gain on the antenna I linked to is within spec, but it is not listed as supported. If Cisco says it is prohibited, then I'm not sure where things stand from an FCC perspective (assuming you are in the USA). Your mileage may vary, not FDIC insured, buyer beware, etc.

Scott Fella Sun, 04/12/2009 - 07:39

Just look at the gain on the antenna Cisco has and find a 3rd party antenna that matches that gain. What you have to watch out for is the total EIRP out of the antenna.

gamccall Mon, 04/13/2009 - 13:49

note that three APs is almost certainly not enough to give any decent level of accuracy with RFID tracking. A location services design has some specific requirements regarding AP placement- I would recommend reviewing the Wi-Fi Location-Based Services Design Guide on Cisco's website before getting too far with this project.

Specifically, to get good position accuracy you're going to have to have at least 5 AP's- one in each corner of the building, plus one in the middle- and possibly more than that depending on the building's size and shape.

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