How many walls can wifi transmit through?

This seems like a newbie question. But here goes...

I want to link two computers together with wifi, preferably g-type.
Both computers are within the same house, but are ~8 meters apart, and
separated by three interior walls.

I have no idea how much those interior walls will weaken the signal.
Can anyone tell me how well this will work please, if at all?

Thanks

The router will be right adjacent to one of the computers...

iconoclastical wrote:

> I have no idea how much those interior walls will weaken the signal.
> Can anyone tell me how well this will work please, if at all?

It's hard to say without knowing what your walls are made of.

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Jeff Liebermann wrote:
> On Sat, 6 Jun 2009 20:25:40 -0700 (PDT), iconoclastical
> <(E-Mail Removed)> wrote:
>
>> This seems like a newbie question. But here goes...
>
> Warning: Math ahead. Please fasten your seat belt.
>
>> I want to link two computers together with wifi, preferably g-type.
>> Both computers are within the same house, but are ~8 meters apart, and
>> separated by three interior walls.
>>
>> I have no idea how much those interior walls will weaken the signal.
>> Can anyone tell me how well this will work please, if at all?
>
> It depends on what's inside the walls. If the 3 walls are just
> clapboard, cardboard, vegetable board, or Japanese wall panels, you
> could easily go through a dozen walls. However, if you have aluminum
> foil backed insulation in the walls, even one wall would be a
> challenge.
>
> From the FAQ, attenuation of various building materials:
> <http://wireless.navas.us/wiki/Wi-Fi#Attenuation>
> There are several ways to use the chart. Basically, 6dB loss equals
> half your range. 12dB loss is 1/4th the range.
>
> Put your router in a window and go for a walk with your wireless
> connected computah. The idea is to get a rough idea of how far you
> can go before the signal ceases being usable. Ping with large packets
> works well for this test. With the stock antennas, about 100 meters
> is typical.
>
> If you're able to go 100 meters, and still get a RELIABLE connection,
> then at 8 meters, you can tolerate a:
> 10 log (100/8) = 11dB loss
> Looking at the chart, one interior solid wall is about 9dB loss, which
> means you can go through one solid wall, but not two (which would be
> 18dB loss).
>
> Performance can be enhanced by changing antennas. Using the above
> example, a fairly crude direction antenna, with 8dBi gain, will give
> you 6dB more to work with. (That's because the antenna gain of your
> existing rubber ducky router antenna is about 2dBi). In theory, you
> should then be able to tolerate 11+6=17dB loss, or almost enough to
> make it through two 9dB loss inside walls.
>
> Of course, things never get better, only worse. When dealing with
> inside walls, multipath and reflections can become a problem. Just
> moving a few cm may be the difference between decent thruput and no
> signal. It may work, but isn't particularly reliable.
>
> My usual advice is once you get beyond one wall, find an alternative
> such as running the CAT5 cable, power line networking, or phone line
> networking.
>
A lurker says thank you.

Lou

Hmmm so I can pull out my NOS power line networking system and use that?
I was going to dispose of it since I have wireless routers on my DSL system.

I have run a Cat-5 cable from one side of my house through the attic to the
other side. Then I could have hooked up a wireless router there too, but it
went straight to one computer instead.
--
Thanks from another lurker! ;-)
later,
(One out of many daves)

"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Sat, 6 Jun 2009 20:25:40 -0700 (PDT), iconoclastical
> <(E-Mail Removed)> wrote:
>
>>This seems like a newbie question. But here goes...
>
> Warning: Math ahead. Please fasten your seat belt.
>
>>I want to link two computers together with wifi, preferably g-type.
>>Both computers are within the same house, but are ~8 meters apart, and
>>separated by three interior walls.
>>
>>I have no idea how much those interior walls will weaken the signal.
>>Can anyone tell me how well this will work please, if at all?
>
> It depends on what's inside the walls. If the 3 walls are just
> clapboard, cardboard, vegetable board, or Japanese wall panels, you
> could easily go through a dozen walls. However, if you have aluminum
> foil backed insulation in the walls, even one wall would be a
> challenge.
>
> From the FAQ, attenuation of various building materials:
> <http://wireless.navas.us/wiki/Wi-Fi#Attenuation>
> There are several ways to use the chart. Basically, 6dB loss equals
> half your range. 12dB loss is 1/4th the range.
>
> Put your router in a window and go for a walk with your wireless
> connected computah. The idea is to get a rough idea of how far you
> can go before the signal ceases being usable. Ping with large packets
> works well for this test. With the stock antennas, about 100 meters
> is typical.
>
> If you're able to go 100 meters, and still get a RELIABLE connection,
> then at 8 meters, you can tolerate a:
> 10 log (100/8) = 11dB loss
> Looking at the chart, one interior solid wall is about 9dB loss, which
> means you can go through one solid wall, but not two (which would be
> 18dB loss).
>
> Performance can be enhanced by changing antennas. Using the above
> example, a fairly crude direction antenna, with 8dBi gain, will give
> you 6dB more to work with. (That's because the antenna gain of your
> existing rubber ducky router antenna is about 2dBi). In theory, you
> should then be able to tolerate 11+6=17dB loss, or almost enough to
> make it through two 9dB loss inside walls.
>
> Of course, things never get better, only worse. When dealing with
> inside walls, multipath and reflections can become a problem. Just
> moving a few cm may be the difference between decent thruput and no
> signal. It may work, but isn't particularly reliable.
>
> My usual advice is once you get beyond one wall, find an alternative
> such as running the CAT5 cable, power line networking, or phone line
> networking.
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

Thank you Jeff, your posting was very helpful.

In my case, the three walls are hollow (6-9db), so overall my
situation is marginal. But I will find another way.

Thanks again.

On Jun 8, 4:18*am, Jeff Liebermann <je...@cruzio.com> wrote:
> Warning: *Math ahead. *Please fasten your seat belt.
>
> It depends on what's inside the walls. *If the 3 walls are just
> clapboard, cardboard, vegetable board, or Japanese wall panels, you
> could easily go through a dozen walls. *However, if you have aluminum
> foil backed insulation in the walls, even one wall would be a
> challenge.

Yes I have two wireless routers, one that is the DSL modem combo and a DLink
wireless router that has a better range.

I did
"Put it on a different channel (1,6 or 11) as the main router and disable
the DHCP server"

If I redo another place, I will plan out the CAT-5 cabling inside of the
walls! <g>

thanks!
--
later,
(One out of many daves)

"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Sun, 7 Jun 2009 17:30:45 -0500, "dave AKA vwdoc1"
> <(E-Mail Removed)> wrote:
>
>>Hmmm so I can pull out my NOS power line networking system and use that?
>>I was going to dispose of it since I have wireless routers on my DSL
>>system.
>
> Yep. That's what wi-fi is for. The problem is that it's not as
> reliable as wired networking. If you have a choice, CAT5 is always
> better.
>
>>I have run a Cat-5 cable from one side of my house through the attic to
>>the
>>other side. Then I could have hooked up a wireless router there too, but
>>it
>>went straight to one computer instead.
>
> You can have it both ways. Install a 2nd wireless access point at the
> computer end:
> <http://wireless.navas.us/wiki/Wi-Fi_How_To#Use_a_wireless_router_as_a_wireless_acce ss_point>
> Put it on a different channel (1,6 or 11) as the main router and
> disable the DHCP server. If your computer is a laptop with wireless,
> you now have connectivity.
>
> What do you mean by "I have wireless routers"? You have more than one
> in the system?
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

iconoclastical <(E-Mail Removed)> wrote in news:23b3e0b9-4f78-
467a-9b82-(E-Mail Removed):

> Thank you Jeff, your posting was very helpful.
>
> In my case, the three walls are hollow (6-9db), so overall my
> situation is marginal. But I will find another way.
>
> Thanks again.

If the walls are just that.....hollow.....then why marginal ?

My wireless rtr is in my basement, at one end of the house, inside a
metal cabinet mounted on the wall (circa 1955). This is my comm cabinet
with a rack mount switch and patch panel and (8) CAT5 runs come back to
this box. The cable modem is here as well. The wireless rtr is a small D-
Link with a cheesy little 3" swivel up antenna. I leave the cabinet door
open, and have complete wireless coverage anywhere in the entire house.
(It's a ranch so only one floor.)

A 'prediction' of 'marginal' is just that, a prediction. Even the most
expensive engineering tools are only making 'predictions'. You can never
be sure about anything wireless until you actually try it.

(Well that's not completely true........but.)




>
> On Jun 8, 4:18*am, Jeff Liebermann <je...@cruzio.com> wrote:
>> Warning: *Math ahead. *Please fasten your seat belt.
>>
>> It depends on what's inside the walls. *If the 3 walls are just
>> clapboard, cardboard, vegetable board, or Japanese wall panels, you
>> could easily go through a dozen walls. *However, if you have aluminum
>> foil backed insulation in the walls, even one wall would be a
>> challenge.
>

> Y'er welcome. *
>
> Hint: *You'll get better answers if you supply specifics, numbers,
> equipment list, materials, conditions, etc.

Yes, I guess I was vague.

I live in one of three connected flats. I'm in the flat at one end,
and want to network with the guy in the flat at the other end, so that
we can share a broadband connection. $100 a month around here.But
between us lies the vacant flat in the middle.

These flats were built as community housing in the late 50s, and
having spent some winters here, I can attest that there is no
insulation in those walls. And while the exterior walls are brick, the
internal walls between the flats appear hollow, materials and
thickness unknown.

Now, when I said earlier that there were 3 walls to penetrate, I
wasn't quite honest. There are the two obvious walls that separate the
flats. But I also counted a partition-closet (~50cm thick) in the
adjacent flat as a third wall.

But eventually someone will move into the flat adjacent to me. So
depending on what my new neighbour puts in his closet, it is hard to
judge what attenuation that will cause. If he decides to hide some
scrap metal in his closet, I'm screwed.

I liked you thorough treatment and maths above though, and if I had
routers and/or wireless laptops lying around, I would just put it all
together and see what signal I get. But really these are things I will
have to purchase.

It is marginal, but I'm not a quitter. I'm thinking about climbing up
the manhole in the ceiling, and seeing if I can get ethernet cable
between our two flats. That would be cheaper in lots of ways.

But failing that, then I think I can position the WAP and wireless
router creatively, such that it avoids that accursed partition-closet.
And if the signal through the two hollow walls still isn't strong
enough, then I can upgrade one or both the antennas to boost the
signal.

So nothings a problem, just a matter of finding the best and cheapest
way to do this I think... That said, I'm glad I asked the question, as
everyone here has been most helpful with their answers :-)

Grant

iconoclastical wrote:

> It is marginal, but I'm not a quitter. I'm thinking about climbing up
> the manhole in the ceiling, and seeing if I can get ethernet cable
> between our two flats. That would be cheaper in lots of ways.
....
> So nothings a problem, just a matter of finding the best and cheapest
> way to do this I think...

I reckon you've already found it. That's the first thing I'd try if I didn't
have any wireless kit to experiment with.

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A few flakes working together can unleash an avalanche of destruction