Leaky Coax for 2.4GHz?

i'm helping a client design a house that'll be built using concrete
and rebar, which may significantly impact his WiFi coverage. Rather
than put an AP in every room (and deal with the problems of seamless
roaming), does anyone make a "leaky coax" that I can string around the
house? I've seen this used in tunnels and subways for radio gear...

Thanks!

On Mon, 06 Dec 2004 07:26:14 -0500, William P.N. Smith wrote:

>i'm helping a client design a house that'll be built using concrete
>and rebar, which may significantly impact his WiFi coverage. Rather
>than put an AP in every room (and deal with the problems of seamless
>roaming), does anyone make a "leaky coax" that I can string around the
>house? I've seen this used in tunnels and subways for radio gear...

Not for 2.4GHz. The highest frequency in use is 900MHz and that's
with fairly high power radios. The problem is that it's still coax
cable whether it leaks or not and coax cable at 2.4GHz is very lossy.
By the time you would snake it around the house, most of your signal
will be absorbed by the coax, not radiated.
http://www.mitsubishi-cable.co.jp/pr...i/leakytb1.htm
http://www.mitsubishi-cable.co.jp/pr...i/leakycl.html

Since this construction is new, it would be easy enough to install
signalling conduits in the walls, and snake whatever cables are
required for a wired LAN later. With concrete construction, the last
thing the owner needs is a jack hammer remodel. It's not just the LAN
but CATV coax, rotator cable, intercom, telco, fiber, hi-fi, satellite
dish, free to air, ham radio, GPS time sync, and whatever else I
forgot that will be a problem with wiring. Put in BIG conduit,
especially to the roof, leave lots of room for expansion, leave a
non-rotting pull string, and forget about wireless for now. Make sure
everything comes to one place (19" rack, communications closet, or
structured wiring panel) with lots of room for punch down blocks (type
110), LAN boxes, and standby power UPS.

If the owner insists on wireless in each room, use the CAT5 LAN wiring
in the conduit to act as a backhaul for multiple access points.
Methinks you'll find the $50-$70 cost of one access point per room to
be much less than any exotic RF solutions.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

Jeff Liebermann <(E-Mail Removed)> wrote:
>http://www.mitsubishi-cable.co.jp/pr...i/leakytb1.htm
>http://www.mitsubishi-cable.co.jp/pr...i/leakycl.html

Ah, live and learn, thanks!

>Since this construction is new, it would be easy enough to install
>signalling conduits in the walls

Oh, yes, we're planning lots of conduit, but one of the requirements
is seamless wireless networking, and AFAICT that's not possible with
the current state of the art in residential-class APs (unless there's
something I'm missing).

Thanks for all your help, Jeff!

On Tue, 07 Dec 2004 09:23:10 -0500, William P.N. Smith wrote:

>Jeff Liebermann <(E-Mail Removed)> wrote:
>>http://www.mitsubishi-cable.co.jp/pr...i/leakytb1.htm
>>http://www.mitsubishi-cable.co.jp/pr...i/leakycl.html
>
>Ah, live and learn, thanks!
>
>>Since this construction is new, it would be easy enough to install
>>signalling conduits in the walls
>
>Oh, yes, we're planning lots of conduit, but one of the requirements
>is seamless wireless networking, and AFAICT that's not possible with
>the current state of the art in residential-class APs (unless there's
>something I'm missing).

Seamless, as in roaming from room to room without dropping
connections? No problem.

The "problem" with roaming wireless is in roaming between access
points that each have different routes to the internet via different
ISP's. Each access point would assign a different IP address,
gateway, and DNS server as the client radio moves among the access
points. At this time, there's no common standard for transfering an
IP address between access points, but it's being worked over and will
be part of some future 802.11(something) standard.

However, that's NOT a problem with a home network of multiple access
points. Each access point has the exact same route to the internet
and delivers the exact same IP addresses to the client from a single
DHCP server. Setup all access points with the same SSID and WEP/WPA
key, select channels for the minimum interference between adjacent
access points, and a wireless client will roam merrily among them.
There will be a slight delay as the client switches between AP's, but
the connection will resume momentarily. It's exactly the same as if
you unplugged a wired computah from an ethernet switch, and moved the
cable to another port on the same (or nearby) switch.

Some Windoze clients are better at roaming than others. XP SP2 does a
decent job of it. I really haven't played with this much. If you
really want seamless and like spending money, try one of the "wireless
switch" vendors, where the radios are literally brain dead, and all
the action happens in the central switch.
http://www.symbol.com/products/wirel...tchsys-ov.html
http://www.arubanetworks.com/products/wlan/
3Com and Cisco also have wireless switch products. However, methinks
this is overkill for a home network. It can be done with generic
access points, but it would be a good idea to buy two and test it
first to avoid suprises. I'm guessing(tm) that you'll have more
problems with the various wireless clients not wanting to let go of a
connection from an AP with a marginal signal, than with any problems
inherent in the AP's.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

Jeff Liebermann <(E-Mail Removed)> wrote:
>Setup all access points with the same SSID and WEP/WPA
>key, select channels for the minimum interference between adjacent
>access points, and a wireless client will roam merrily among them.
>There will be a slight delay as the client switches between AP's, but
>the connection will resume momentarily. It's exactly the same as if
>you unplugged a wired computah from an ethernet switch, and moved the
>cable to another port on the same (or nearby) switch.

>it would be a good idea to buy two and test it
>first to avoid suprises.

Ah, maybe that's my problem, I was using D-Link products, and it was a
real nightmare. I'll try again with Linksys...

Thanks!

Actually "Leaky Coax" is available for 2.4Ghz, but it is quite costly..
I have worked with many different distributed antenna systems for 2.4..
Many Installers of Malls, Hotels, Train Tunnels, i.e. Sprint etc.. use DAS
instead of gobs of AP's...

Andrew makes a great one for 2.4 that I have used in a tunnel in Europe..
It is a combination of their RADIAX and HELIAX cables:
http://www.andrew.com/search/docviewer.aspx?docid=3892

Very cool stuff that works, but probably way way too costly for your home..
Besides 5/8" hardline is not easy to pull anyway


"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Mon, 06 Dec 2004 07:26:14 -0500, William P.N. Smith wrote:
>
> >i'm helping a client design a house that'll be built using concrete
> >and rebar, which may significantly impact his WiFi coverage. Rather
> >than put an AP in every room (and deal with the problems of seamless
> >roaming), does anyone make a "leaky coax" that I can string around the
> >house? I've seen this used in tunnels and subways for radio gear...
>
> Not for 2.4GHz. The highest frequency in use is 900MHz and that's
> with fairly high power radios. The problem is that it's still coax
> cable whether it leaks or not and coax cable at 2.4GHz is very lossy.
> By the time you would snake it around the house, most of your signal
> will be absorbed by the coax, not radiated.
> http://www.mitsubishi-cable.co.jp/pr...i/leakytb1.htm
> http://www.mitsubishi-cable.co.jp/pr...i/leakycl.html
>
> Since this construction is new, it would be easy enough to install
> signalling conduits in the walls, and snake whatever cables are
> required for a wired LAN later. With concrete construction, the last
> thing the owner needs is a jack hammer remodel. It's not just the LAN
> but CATV coax, rotator cable, intercom, telco, fiber, hi-fi, satellite
> dish, free to air, ham radio, GPS time sync, and whatever else I
> forgot that will be a problem with wiring. Put in BIG conduit,
> especially to the roof, leave lots of room for expansion, leave a
> non-rotting pull string, and forget about wireless for now. Make sure
> everything comes to one place (19" rack, communications closet, or
> structured wiring panel) with lots of room for punch down blocks (type
> 110), LAN boxes, and standby power UPS.
>
> If the owner insists on wireless in each room, use the CAT5 LAN wiring
> in the conduit to act as a backhaul for multiple access points.
> Methinks you'll find the $50-$70 cost of one access point per room to
> be much less than any exotic RF solutions.
>
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 AE6KS 831-336-2558

On Sat, 11 Dec 2004 09:16:36 GMT, "Fresnel Fadermargini"
<(E-Mail Removed)> wrote:

>Actually "Leaky Coax" is available for 2.4Ghz, but it is quite costly..
>I have worked with many different distributed antenna systems for 2.4..
>Many Installers of Malls, Hotels, Train Tunnels, i.e. Sprint etc.. use DAS
>instead of gobs of AP's...
>
>Andrew makes a great one for 2.4 that I have used in a tunnel in Europe..
>It is a combination of their RADIAX and HELIAX cables:
> http://www.andrew.com/search/docviewer.aspx?docid=3892
>
>Very cool stuff that works, but probably way way too costly for your home..
>Besides 5/8" hardline is not easy to pull anyway

Does it work with 802.11b/g? When I tried some lab experiments with
multiple antennas on a coax run, I found that multipath was just
killing the data with delay spreading and generating intersymbol
interference. I got great signal signal strength, thruput just stunk.

We didn't use leaky coax as we didn't want to lose signal by radiating
inside walls, risers, ducts, etc. The system was a number of fairly
high impedance radiators, located on multiples of a half wave
electrical along the coax. The end was terminated to eliminate
reflections. The match was tolerable (-15dB return loss) mostly
thanks to cable loss. A typical large room had 4 radiators.

It worked well if I had only one radiator per room, but would screwup
badly with 4 due to multipath. I never tried leaky coax because I
assumed it would have the same problem. However, this was before
802.11g, where OFDM may have helped deal with the reflections.

Duz leaky coax work with 802.11b/g?


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

Leaky Coax works well with 11b, and actually better with 11g as OFDM is more
forgiving. Multi-path has not been an issue with our installs as we only
run 1 radiator in
an area... Even with multiple radiators, each antenna is only x-mitting and
rcving at the same
instance (TDD) as it is hooked to the same Radio..
Multi-Path from the perspective of the client has not happened... I can only
guess why..
perhaps because the area from the cable that is in the radiation zone is
small, low DB after
a reflection and phase shift, the difference in gain is great hence no
problem???
We have actually loaded Radio's farther
down the line with Duplexors made by Motorola (but I am not sure how they
take care
of issues.. already a done design) This was done on a Metal Vessel..
3 Radios per cable... 1,6,11

The only problem with the design of these systems and 802.11 is CSMA...
Hidden node
can become an issue for obvious reasons.. so RTS/CTS helps... I have found
great results
in limited clients, and good results for internet access which can take
collision reduced bandwidth
with higher number of users...

For a lower loss for 2.4Ghz but a super high price, there is Leaky
Waveguide... but will suffer
the same problems.

The stuff is just to expensive for me to experiment with for
more qualified data



"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Sat, 11 Dec 2004 09:16:36 GMT, "Fresnel Fadermargini"
> <(E-Mail Removed)> wrote:
>
> >Actually "Leaky Coax" is available for 2.4Ghz, but it is quite costly..
> >I have worked with many different distributed antenna systems for 2.4..
> >Many Installers of Malls, Hotels, Train Tunnels, i.e. Sprint etc.. use
DAS
> >instead of gobs of AP's...
> >
> >Andrew makes a great one for 2.4 that I have used in a tunnel in Europe..
> >It is a combination of their RADIAX and HELIAX cables:
> > http://www.andrew.com/search/docviewer.aspx?docid=3892
> >
> >Very cool stuff that works, but probably way way too costly for your
home..
> >Besides 5/8" hardline is not easy to pull anyway
>
> Does it work with 802.11b/g? When I tried some lab experiments with
> multiple antennas on a coax run, I found that multipath was just
> killing the data with delay spreading and generating intersymbol
> interference. I got great signal signal strength, thruput just stunk.
>
> We didn't use leaky coax as we didn't want to lose signal by radiating
> inside walls, risers, ducts, etc. The system was a number of fairly
> high impedance radiators, located on multiples of a half wave
> electrical along the coax. The end was terminated to eliminate
> reflections. The match was tolerable (-15dB return loss) mostly
> thanks to cable loss. A typical large room had 4 radiators.
>
> It worked well if I had only one radiator per room, but would screwup
> badly with 4 due to multipath. I never tried leaky coax because I
> assumed it would have the same problem. However, this was before
> 802.11g, where OFDM may have helped deal with the reflections.
>
> Duz leaky coax work with 802.11b/g?
>
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 AE6KS 831-336-2558