AP that allows to limit the range.

Unanswered Question
May 4th, 2008

Hi,

We need to setup an office with complete wireless network. I just want to know what devices are good if we want to limit the wireless to some particular range. I mean that we do not want our devices to be visible to outside users. If we can limit this on the device at some spots as required ?

Please guide.

Thanks.

I have this problem too.
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rob.huffman Sun, 05/04/2008 - 09:04

Hi Kalpesh,

This is an excellent question! I'm going to start with the requisite Site Survey recommendation :)

You should try to perform a site survey to help determine the AP/Antenna types and placement.Make sure the site survey is done when the facility is in full activity mode and everything is up and running. Here is some info to help get you started.

"In a Wireless network, many issues can arise which can prevent the radio frequency (RF) signal from reaching all parts of the facility or reaching far outside the building borders. 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.

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

Tweak the Radio Transmit Power Settings (after you choose non-overlapping Channels) so your signal does not "bleed out" beyond your walls too much. This ability is available on all Cisco AP's;

Configuring Radio Transmit Power

From this good doc;

http://www.cisco.com/en/US/products/hw/wireless/ps4570/products_configuration_guide_chapter09186a00804194ce.html#wp1017196

Hope this helps!

Rob

Scott Fella Sun, 05/04/2008 - 09:18

Rob is right... a site survey is required. The only thing is that if you require a certain voice or data coverage, that means a signal of -65 or maybe -72 in room and right by the exterior walls. This means that the signal outside might still be -78 or so. If you are really worried about blocking all RF, you can have this tint installed on your windows:

3M™ Counter Intelligence Films

You have to understand that someone still can grab a good signal by using an external yagi attached to his or her laptop sitting outside in your parking lot or a building across the way. That is why securing your wifi should be your #1 priority.

rob.huffman Sun, 05/04/2008 - 09:49

Hi Scott,

Very cool info! I've never heard of such a product. 5 points for this and all your great work here.

Cheers!

Rob

Scott Fella Sun, 05/04/2008 - 18:26

Thanks Rob! The only thing with this is users will complain about their cell phones :)

ciscokalpesh Sun, 05/04/2008 - 20:52

Hi,

Thanks for reply.

This is a very good info. I would like to ask, if anyone does recommend any particular device model that would be best in such scenario.

Thanks again.

rob.huffman Mon, 05/05/2008 - 04:37

Hi Kalpesh,

You are most welcome :) This is a hard question without knowing the scope of this deployment. If you are going with multiple AP's in a medium to large deployment it's likely they will be "Lightweight" AP's working in conjunction with a WLC (Wireless Lan Controller) here are 3 good choices;

AIR-LAP1131AG - Good AP with built-in Antennas and multiple mounting options.

http://www.cisco.com/en/US/docs/wireless/access_point/1130/installation/guide/113h_c4.html

AIR-LAP1242AG - Good Rugged AP with many External Antenna choices and multiple mounting options.

http://www.cisco.com/en/US/docs/wireless/access_point/1240/installation/guide/124h_c4.html

AIR-LAP1252 - Newest AP with many External Antenna choices and multiple mounting options.***Supports the newest "N" radio Draft format.

http://www.cisco.com/en/US/docs/wireless/access_point/1250/installation/guide/125h_c4.html

Understanding the Lightweight Access Point Protocol (LWAPP)

http://www.cisco.com/en/US/netsol/ns340/ns394/ns348/ns337/networking_solutions_white_paper0900aecd802c18ee.shtml

Lightweight Access Point FAQ

http://www.cisco.com/en/US/products/hw/wireless/ps430/products_qanda_item09186a00806a4da3.shtml

Deploying Cisco 440X Series Wireless LAN Controllers

http://www.cisco.com/en/US/products/ps6366/prod_technical_reference09186a00806cfa96.html

Cisco Wireless LAN Controller Configuration Guide, Release 4.0

http://www.cisco.com/en/US/products/ps6366/products_configuration_guide_book09186a00806b0077.html

WLC Video

http://www.cisco.com/en/US/products/ps6366/index.html

Hope this helps!

Rob

ciscokalpesh Mon, 05/05/2008 - 06:36

Hi Rob,

Thanks for the receptive reply.

These plentiful links would indeed help us during the scope.

Thanks and regards,

Kalpesh.

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