How to improve the wireless LAN coverage?

Unanswered Question
Feb 14th, 2007

Hi all,

We are using Cisco 1200 access point in our small retail shops and use some wireless heldheld devices to connect the wireless network. Since the shops are inside the shopping plaza, there are many other wireless access point which interference our wireless clients. The access point were installed in the middle of the shop, sometimes, our client walked to the shop entrance (< 10m from the access point), the wireless network was disconnected and it may try to connect the other unknown access point. I tried to change the frequent but it doen't help. We are using a pair of 2.2dBi Dipole Anntenna wit the AP and mount in on the wall (~ 1m above the ground). Is there any suggestions to improve the coverage? Is there any improvement if I use a more powerful anntenna (e.g. 6.5 dBi Wall Mount anntenna)?

Thanks,

Dovelet

I have this problem too.
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rob.huffman Thu, 02/15/2007 - 05:45

Hi Dovelet,

The first thing that I would do (without seeing the environment or doing a site survey) would be to mount the AP with the Dipole antennas much higher. You probably want to be at least 3m above the ground. At 1m you will encounter many problems associated with Retail Display racks/cases as well as people walking in front of the AP. It is amazing what the fluids in a Human will do to a wireless signal, and multiply that by a number of people in a retail shop (hopefully :) shopping and signal degradation is bound to occur. You might also want to try an upgraded antenna, but make sure it is mounted above the height of people and racks and I'm sure things will greatly improve!

Here is a doc that may help (based on AP placement etc.)

Site Survey RF Recommendations

http://www.cisco.com/en/US/products/hw/phones/ps379/products_implementation_design_guide_chapter09186a00802a09e0.html#wp1011285

Hope this helps!

Rob

claeysg Thu, 02/15/2007 - 05:54

Hi,

Try to switch to 802.11a if your clients support it. There is less interferences in 802.11a and more channels available.

Rgds,

Gaetan

scottmac Sat, 02/17/2007 - 06:31

With the caveat that a site survey should be done, I believe i'd start by looking at some sort of "Patch" antenna ... it focuses the RF pattern in one general direction .... and put them above the doorway facing into the area of coverage.

Of course, the deeper into the area the client walks, the weaker the signal, but it's also farther away from the interfering signals.

As Rob mentioned, humans (plants, most organic things) and display racks will greatly affect the signals.

These freqs bounce pretty well, and some of the shadow areas should be covered by (sub-optimal) reflections.

Look into a 180 degree "patch" ... look at the coverage pattern and see if it'll genrally match your area of interest.

Good Luck

Scott

rtford31 Mon, 02/19/2007 - 23:41

Dovelet,

I was going to suggest upgrading your AP to 802.11a but you are probably using Symbol handhelds and they don't support 802.11a yet (for that matter I don't think there is a handheld that supports 802.11a yet).

Use a computer and scan the airwaves to see what APs are out there and what frequency they are on. Configure your AP to a different channel either 1,6 or 11 (that no one else is on).

Put two 6 dBi Patch Wall Mount Antennnas 3 to 4 feet apart on one wall, part # AIR-ANT2460P-R. If you have a long narrow store the patch antennas will be your best bet, They have a narrow beam and you will get less multipath distortion from the radio waves bouncing off your walls. You can also get an Antenna mount kit, part # AIR-ACC2662 to help better aim your patch antennas.

If you have a square or circular store place two omnidirectional antennas in the center of the store, use a high grade low loss cable like part # AIR-CAB100ULL-R. Or for that matter put your current AP high in the center of the store. Run Cat5e cable to it and use a Power Injector to provide power to your AP over the cat5e. You can also add the high gain omnidirctional antennas (2 of them) to this configuration without needing the low loss cable.

These are powerful antennas and you don't want your signal going into the store across the way from you. So take a laptop or your hand held walk across the way to the front of the store and see what kind of signal you get. Reduce the power setting of your AP so the signal doesn't bleed into the store across the way from you and if you use omnidirectional antennas into stores on either side of you.

Make sure you mount the antennas high 8 to 10 feet. I assume you have your Encryption set,SSID broadcast disabled and your handhelds configured to only connect to your APs SSID.

Hope this helps.

Robert

murphychan Tue, 02/20/2007 - 06:38

Hi all,

Thanks all of your information (especially Robert). FYI, our handhelds are only support 802.11b, so 802.11a cannot be used. Due to some limitation, the AP cannot be installed above the ceiling. The shapes of stores are in square.

Robert,

Do you mean I can keep the AP in the existing position and use the cable (AIR-CAB100ULL-R) to extent the existing 2.2dBi Dipole Antenna to the ceiling? Do I need to keep the distance between two antenna same as before or I can put one antenna near the entrance and one antenna inside the Shop? Thanks.

Regards,

Dovelet

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