suggestions on ap's

Unanswered Question
Feb 16th, 2007

I am looking to put wireless capabilities into a automobile service department for use by technicians servicing automobiles. Walls are concrete block. service department has a wal down the middle the ceiling is metal with a showroom above. I would like to give access to both floors if possible. Area is about 100 ft by 80ft on each floor. Can anyone suggest a access point and antennas? What problems do you think we might encounter?

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scottmac Sat, 02/17/2007 - 06:22

One access point will almost certainly not cover both floors.

It is likely that you will need two or three (possibly more) per floor for adequate coverage of the entire floor.

A proper site survey, and a good statement of your needs / needs analysis should be done. There are way too many variables involved to be able to tell you which one (or more) APs and antenna combinations will fit your scenario.

Also note that while many / most APs have two antenna connections, they are for "diversity," to cover a single area well, not cover multiple areas.

Start with a good site survey, then move on from there.

Good Luck

Scott

rob.huffman Sun, 02/18/2007 - 08:09

Hi Michael,

I just wanted to add a note to Scott excellent points. As he said you are going to need at least 2 AP's per floor to accomplish your goals. You should try to perform a site survey to help determine the AP/Antenna types and placement. Here is some info to help get you started. I would recommend an AP with external antenna connectors (like 1240) this will give you more flexability in your design.

"In a Wireless network, many issues can arise which can prevent the radio frequency (RF) signal from reaching all parts of the facility. Examples of RF issues include mulitpath distortion, hidden node problems, and near/far issues. In order to address these, you need to find the regions where these issues occur. A site survey helps you to do this. A site survey helps define the contours of RF coverage in a particular facility. It helps us to discover regions where mulitpath distortion can occur, areas where RF interference is high and find solutions to eliminate such issues. A site survey that determines the RF coverage area in a facility also helps to choose the number of Wireless devices that a firm needs to meet its business requirements.

A proper site survey provides detailed information that addresses coverage, interference sources, equipment placement, power considerations and wiring requirements. The site survey documentation serves as a guide for network design and for the installation and verification of the Wireless communication infrastructure.

These are some of the steps that are performed during your site survey:

Obtain a facility diagram in order to identify the potential radio frequency (RF) obstacles.

Visually inspect the facility to look for potential barriers or the propagation of RF signals and identify metal racks.

Identify user areas that are highly used and the ones that are not used.

Determine preliminary access point (AP) locations. These locations include the power and wired network access, cell coverage and overlap, channel selection, and mounting locations and antenna.

Perform the actual surveying in order to verify the AP location. Make sure to use the same AP model for the survey that is used in production. While the survey is performed, relocate APs as needed and re-test.

Document the findings. Record the locations and log of signal readings as well as data rates at outer boundaries."

Wireless Site Survey FAQ

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_q_and_a_item09186a00805e9a96.shtml

Cisco Aironet Wireless Access Points Solution Overview (There are some great recommendations in Table 4)

http://www.cisco.com/en/US/products/ps6521/prod_brochure0900aecd8035a015.html

Cisco Aironet Antenna Reference Guide

http://www.cisco.com/en/US/products/hw/wireless/ps469/products_data_sheet09186a008008883b.html

Hope this helps!

Rob

mpmccarron Tue, 02/20/2007 - 11:20

Have seen somewhere that Cisco has some SIte survey software, but I haven't seen it. I didn't see it with the stuff I got with the Aironet 140AG I have. Do you know what equipment it comes with? Can you suggest any other low cost alternative? We will propably only use it this one time.

csannedhi Sun, 02/18/2007 - 15:42

First of all you really don't need to buy Cisco APs to provide wireless coverage. You can any consumer-grade wireless routers made by Linksys, etc.

Regarding the coverage, having metallic ceiling really complicates things. You don't need to worry about the walls because the signal doesn't need to penetrate them to provide coverage outside the walls. As others are pointing out you need more than 1 AP. I would start with 1 AP on each floor. Keep them at the center of each floor - any AP will give 50 ft coverage radius which is enough to cover an entire floor. Setup AP1 on channel 1 and AP2 on channel 11 to avoid any potential interference between the APs.

HTH

andrew.brazier@... Mon, 02/19/2007 - 02:41

I disagree. You can buy Linksys (DON'T buy routers, you need AP's) and be disappointed at the coverage and performance or you can swallow the extra cost and buy Cisco kit which will give you the coverage you want.

From your description I also would think in terms of 2-3 AP's per floor but to be sure of quantities and locations of APs you must do a site survey.

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