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View Full Version : 802.11b Through Concrete



Corduroy
05-14-2002, 03:48 PM
The house I live in is built on to the business that my father owns, so the floor/ceiling seperating the first and second floor is a layer of pre-stressed concrete, like what you would find in most commercial buildings of any good size. This floor is about 6 inches thick.

Does anyone know if 802.11b WAPs will work through such a material or am I foolish to buy it and limit myself to one floor use? :confused:

Albinus
05-15-2002, 08:54 PM
I've actually seen 802.11b networks fail to go through thin fibro or timber walls, my friend has one that won't even go 10 metres upstairs :(

So go fixed cabling unless you really, really need wireless - it's slow as a pig in molasses :(

Corduroy
05-16-2002, 08:35 AM
Thanks for the advice Albinas. I'm actually going to run a test with a friend's WAP, as soon as he gets a card for his laptop, as f now he only has the WAP. As soon as I do test it out I will post my findings.

We do have 900mhz cordless phones in the house and they easily broadcast through the concrete, or however the signal reaches the phone. They come in crystal clear even on the opposite end of the house or out in one of the garages, which would be going through several cinder block wall.

Isn't 802.11b supposed to be in a frequency that can travel farther than 900mhz phones? I suppose a test will tell for sure, but if others concur with Albinus, I won't even waste my time with that.

Wiggo
05-16-2002, 10:48 AM
And if you live in a builtup area I'd always be worried about signal interference. :smokin:
<center>:cheers:</center>

Albinus
05-17-2002, 08:21 PM
900MHz actually has a longer range than 2.4GHz, longer wavelength remember ;)

Which transmits further... AM or FM radio signals? In northern Australia where AM stations are on boosters, the signal can often carry up to 300KM with no trouble with 50KW powering it. FM starts struggling at around 90~100KM with significantly more power (10MW) powering it.

Also, 2.4GHz is the Bluetooth band - 900MHz is the GSM band in Australia, and GSM has a range of 35KM compared to the paltry 10M of Bluetooth :(

As Wiggo said, interference is an issue (security primarily), but as soon as you encrypt your data the bandwidth more than halves. The same friend who has the wireless setup puts his laptop in direct line of sight of the base station about 4M away, at only connects at 5.5Mbps, not 11Mbps like 802.11 is capable of.

So I still say 802.11 is not ready for prime time just yet.

DigitalDD
05-17-2002, 09:17 PM
The house I live in is built on to the business that my father owns, so the floor/ceiling seperating the first and second floor is a layer of pre-stressed concrete, like what you would find in most commercial buildings of any good size. This floor is about 6 inches thick.

Does anyone know if 802.11b WAPs will work through such a material or am I foolish to buy it and limit myself to one floor use? :confused:

The expensive Cisco Aironet cards can broadcast to Cisco access points through 18 inch thick concrete provided it is not steel reinforced concrete. Most budget 802.11b equipment won't do this.

The Cisco products are still too expensive though.

Kheldar
05-21-2002, 07:06 PM
don't forget that as your signal strength drops so does your bandwidth, ie it may work but you'll probably only get 1 Mb connection

802.11b drops from 11 Mb to 5.5 to 2 to 1 mb

So I'd run some cat 5 out the window and then upstairs

DigitalDD
05-22-2002, 12:20 AM
don't forget that as your signal strength drops so does your bandwidth, ie it may work but you'll probably only get 1 Mb connection

802.11b drops from 11 Mb to 5.5 to 2 to 1 mb

So I'd run some cat 5 out the window and then upstairs

I hate the fact that the new 802.11a [54mbs speed] don't seem to have an in between speed to fall back to. They have 54MB/s then drop to 11MB/s which is the same as the max speed of 802.11b then 5.5 then 2 then 1...