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View Full Version : Best technology for "repeating" a wireless signal



toe@lavabit.com
02-21-08, 05:52 PM
I've got a wireless ADSL broadband router at one side of a building,
but its signal is very poor at the other side of the building.
Therefore I need some sort of "repeater".

Let's say that the network I'm trying to get onto is as follows:
SSID: MonkeyBrain
Channel: 3
Network: 10.9.8.0/24
Gateway: 10.9.8.1

So far, I've heard of two kinds of technology for "boosting" the
signal.

Technology 1: You have some sort of wireless device that gets an IP
address on the MonkeyBrain network. This device then broadcasts its
own network with a different SSID, different channel, different
network. Let's stay that the new network is:
SSID: GorillaBrain
Channel: 8
Network: 192.168.1.0/24
Gateway: 192.168.1.254
When you send a packet to the internet from this new GorillaBrain
network, it goes to the default gateway on GorillaBrain, which
forwards it on to the MonkeyBrain gateway, which forwards it to the
internet.

Technology 2: I'm not sure how this works, but you can actually have a
device that just boosts the signal. You've got the same SSID, same
channel, same network address. You can communicate in Layer 2
protocols with the all machines on MonkeyBrain because you trully are
sitting on the MonkeyBrain network. I don't see how you don't have a
problem with both devices (i.e. the broadband router and the repeater
device) sending duplicate signals and taking in duplicate signals.

Which technology do you think is better? Which tends to provide a
faster connection? Are there any other good ways of going about
boosting a signal so that it's strong on the other side of a building?
(The signal I'm trying to boost is coming from an ordinary broadband
router that you'd get from an ISP, nothing fancy).

I was thinking of another way of doing it. Let's say that you have a
device which does the following:

Technology 3: You want to be on the MonkeyBrain network. You have a
wireless device that broadcasts an SSID such as GorillaBrain. It's on
a different channel to MonkeyBrain (let's say it's on channel 12), but
it has the same network address (10.9.8.0/24). When GorillaBrain
receives a frame on channel 12, it forwards it on to MonkeyBrain on
channel 3. In this fashion, you could have MonkeyBrain using WEP, and
GorillaBrain using WPA, but essentially they're the same network.
(e.g. if you went into the router statistics on MonkeyBrain then you'd
be able to see all the hosts that are on GorillaBrain, also all the
GorillaBrain hosts would get their IP address from the DHCP server
running on MonkeyBrain).

Is there any device the accomplishes what I describe in "Technology
3"?

Can anyone please give advice as to what kind of "repeater" device I
should get. My preference would be either Technology 3 or Technology
2. I think Technology 1 would introduce unwarranted overhead and would
add the complication of only being able to communicate via IP with
machines on MonkeyBrain.

Can anyone suggest devices, and perhaps give me an overview of the
technologies used? And don't be afraid to get technical, I've a decent
knowledge of datacoms (and also of wave transmission and the like).

Thanks for listening! :)

Tomás

D. Stussy
02-21-08, 06:55 PM
<toe@lavabit.com> wrote in message
news:fd7b4bf2-e01b-46fd-8058-7345f60bbae7@n75g2000hsh.googlegroups.com...
> I've got a wireless ADSL broadband router at one side of a building,
> but its signal is very poor at the other side of the building.
> Therefore I need some sort of "repeater".

Why not move the wireless router to the CENTER of the building?

toe@lavabit.com
02-21-08, 07:08 PM
D. Stussy:

> > I've got a wireless ADSL broadband router at one side of a building,
> > but its signal is very poor at the other side of the building.
> > Therefore I need some sort of "repeater".
>
> Why not move the wireless router to the CENTER of the building?


Phone line's at one side of the building. I don't want to run a long
phone cable, nor do I want to run a long ethernet cable. Hence the
want for a "repeater" of some sort.

Jeff Liebermann
02-21-08, 08:36 PM
On Thu, 21 Feb 2008 15:52:19 -0800 (PST), toe@lavabit.com wrote:

>I've got a wireless ADSL broadband router at one side of a building,

Make and model of the wireless router?

>but its signal is very poor at the other side of the building.
>Therefore I need some sort of "repeater".

Can you get any kind of signal through the building? If yes, then an
improved antenna on your unspecified ADSL wireless router will
probably help. However, if there are too many walls in the way,
that's probably futile.

Alternatives to a repeater are:
1. Power line networking:
<http://www.homeplug.org>
<http://www.netgear.com/Products/PowerlineNetworking.aspx?for=All>
2. Phone line networking:
<http://www.homepna.org>
3. networking over CATV coax cable:
<http://www.multilet.us>

>Let's say that the network I'm trying to get onto is as follows:
>SSID: MonkeyBrain
>Channel: 3
>Network: 10.9.8.0/24
>Gateway: 10.9.8.1
>
>So far, I've heard of two kinds of technology for "boosting" the
>signal.

Rewind for a second. 802.11 wireless is all done on Layer 2, the MAC
layer. There is no involvement with Layer 3 services, that require IP
addresses. The only IP address that really needs to be involved is
the management IP of the device.

Boosting is not a good technical term. I suggest amplification,
repeating, repeating, regenerating, or something similar.

>Technology 1: You have some sort of wireless device that gets an IP
>address on the MonkeyBrain network. This device then broadcasts its
>own network with a different SSID, different channel, different
>network.

That's a back to back bridge/repeater. It's built from two different
wireless access points (not routers), with the Ethernet ports cross
connected. What one access point hears, is retransmitted by the other
wireless access point.

>Let's stay that the new network is:
>SSID: GorillaBrain
>Channel: 8
>Network: 192.168.1.0/24
>Gateway: 192.168.1.254

Reminder. Repeaters don't know about IP addresses. However, there
are devices that do. For example, a WDS repeater does know about IP
addresses.

>When you send a packet to the internet from this new GorillaBrain
>network, it goes to the default gateway on GorillaBrain, which
>forwards it on to the MonkeyBrain gateway, which forwards it to the
>internet.

Yeah, something like that. Again, the way it gets "forwarded" has
nothing to do with IP addresses. It's all done with MAC addresses.

The one exception is a WDS bridge/repeater, which allows a wireless
access point to simultaneously act as a wireless client bridge, access
point, and repeater.

>Technology 2: I'm not sure how this works, but you can actually have a
>device that just boosts the signal.

Those are mostly tower mounted bi-directional amplifiers. It goes
between your unspecified model wireless router and the antenna. I
don't think your application would be a good fit for one of these.

>You've got the same SSID, same
>channel, same network address.

Yep. Same everything because the amplifier doesn't change any of the
data. It just makes the signal stronger.

>You can communicate in Layer 2
>protocols with the all machines on MonkeyBrain because you trully are
>sitting on the MonkeyBrain network.

Yeah, I guess, whatever that means.

>I don't see how you don't have a
>problem with both devices (i.e. the broadband router and the repeater
>device) sending duplicate signals and taking in duplicate signals.

You *DO* have a problem. However, it's not what you're thinking.
802.11 wireless is half-duplex. You can only send and receive, one at
a time. To prevent collisions, where two transmitters xmit
simultaneously, there is an algorithm and timer included to prevent
this. In a give airspace (within range of your system) only one
transmitter can belch data at a time.

When you use a store and forward repeater to retransmit (repeat) your
data, you have two packets going through the air, one at a time, in
order to deliver one packet of data. Since you can only transmit and
receive one at a time, this cuts the maximum thruput in half.
Actually, it's usually much worse than half because the timing and
synchronization are rarely perfect.

If you decide that a store and forward repeater is the answer, you
should try this simple experiment. Drag your laptop, unspecified
wireless router, and repeater into a closed room and set it up to move
data. Use another computer as a server to simulate the internet.
You'll find that with the repeater functioning, performance will suck,
and downloads will be erratic. Remove the repeater, and things will
work smoothly.

What's happening is by creating an artificially small airspace, all
the 3 transmitters in the room are clobbering and colliding with each
other.

>Which technology do you think is better?

In order of personal prejudice:
- CAT5 wire or fiber to the other side of the building is best.
- Power line, phone line, and coax cable networking is tolerable.
- A directional antenna just might work but tends to marginal.
- A WDS bridge works fairly well, but is messy to configure and
supported on a limited number of access points and wireless routers.
- A simple store and forward repeater sucks but can be made to work.
- The absolute worst is a tower mounted power applier.

>Which tends to provide a
>faster connection?

Fiber optic cable and transceivers.

>Are there any other good ways of going about
>boosting a signal so that it's strong on the other side of a building?

See aforementioned list of alternatives.

>(The signal I'm trying to boost is coming from an ordinary broadband
>router that you'd get from an ISP, nothing fancy).

Is "Ordinary" a brand name or are you embarrassed by your selection of
hardware?

>Technology 3: You want to be on the MonkeyBrain network. You have a
>wireless device that broadcasts an SSID such as GorillaBrain. It's on
>a different channel to MonkeyBrain (let's say it's on channel 12), but
>it has the same network address (10.9.8.0/24).

Won't work. Wireless is bridging and works with MAC addresses. If
you duplicate a LAN IP block at both ends of a wireless link, it's
going to act exactly as if you plugged the duplicate IP's into the
other network. Bad idea.

>When GorillaBrain
>receives a frame on channel 12, it forwards it on to MonkeyBrain on
>channel 3. In this fashion, you could have MonkeyBrain using WEP, and
>GorillaBrain using WPA, but essentially they're the same network.

That reminds me. Many WDS bridges will only do WEP, not WPA. This
allegedly a side effect of the WPA key exchange mechanism. I'm not
convinced that this is true and prefer to think of it as a bug. There
are some products and alternative firmware that support WPA encryption
on WDS, so I know it can be done. Chose your hardware wisely or you
may get stuck with insecure WEP.

>(e.g. if you went into the router statistics on MonkeyBrain then you'd
>be able to see all the hosts that are on GorillaBrain, also all the
>GorillaBrain hosts would get their IP address from the DHCP server
>running on MonkeyBrain).
>
>Is there any device the accomplishes what I describe in "Technology
>3"?

If you insist on using two RF channels, only a back to back pair of
wireless bridges will do that. If you can do it on one channel, it's
called a store and forward repeater.

>Can anyone please give advice as to what kind of "repeater" device I
>should get.

Yes. Don't get a repeater. Run the CAT5 or piggyback on the house
wiring.

>My preference would be either Technology 3 or Technology
>2. I think Technology 1 would introduce unwarranted overhead and would
>add the complication of only being able to communicate via IP with
>machines on MonkeyBrain.

You're going to have store and forward overhead no matter what
technology you select.

>Can anyone suggest devices, and perhaps give me an overview of the
>technologies used?

Start here:
<http://www.smallnetbuilder.com/content/view/86/106/>
There's quite a bit on all manner of 802.11 technology. The reviews
are especially good reading. For example, the WRE54G "range expander"
review is quite informative.
<http://www.smallnetbuilder.com/content/view/24690/96/> (8 pages)
<http://www.smallnetbuilder.com/content/view/29840/98/>

There are really only three technologies.
1. MAC layer repeating with store and forward by SSID (only repeats
packets with a specified SSID on a single channel)
2. IP layer store and forward on top of MAC layer client as a WDS
bridge/repeater.
3. Back to back wireless client bridges.

>And don't be afraid to get technical, I've a decent
>knowledge of datacoms (and also of wave transmission and the like).

I'm not afraid of being technical. However, there's no need here.
Methinks repeaters (and some mesh networks) simply suck and should be
avoided. Note that mesh networks are just a collection of repeaters
and suffer from them collision problems. Some vendors have dual radio
mesh boxes designed to avoid the half-duplex collision problems.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

D. Stussy
02-21-08, 09:11 PM
<toe@lavabit.com> wrote in message
news:e4b4b610-4a6d-4714-9165-6f72c8677743@j28g2000hsj.googlegroups.com...
> D. Stussy:
> > > I've got a wireless ADSL broadband router at one side of a building,
> > > but its signal is very poor at the other side of the building.
> > > Therefore I need some sort of "repeater".
> >
> > Why not move the wireless router to the CENTER of the building?
>
> Phone line's at one side of the building. I don't want to run a long
> phone cable, nor do I want to run a long ethernet cable. Hence the
> want for a "repeater" of some sort.

Don't want to - or can't?

Bill Kearney
02-22-08, 08:54 AM
> Phone line's at one side of the building. I don't want to run a long
> phone cable, nor do I want to run a long ethernet cable. Hence the
> want for a "repeater" of some sort.

Run the wire. It'll be much more reliable, faster and quite likely cheaper
when you factor in the costs of the wifi hassle.

P.Schuman
02-22-08, 10:36 AM
I've got a wireless ADSL broadband router at one side of a building,
but its signal is very poor at the other side of the building.
Therefore I need some sort of "repeater".

> On Thu, 21 Feb 2008 15:52:19 -0800 (PST), toe@lavabit.com wrote:
> Alternatives to a repeater are:
> 1. Power line networking:
> <http://www.homeplug.org>
> <http://www.netgear.com/Products/PowerlineNetworking.aspx?for=All>
> 2. Phone line networking:
> <http://www.homepna.org>
> 3. networking over CATV coax cable:
> <http://www.multilet.us>
>

We used these types of "AC wire" solutions to get an Ethernet connection out
to a loading dock area.
From there, we installed a hub and WiFi AP for the dock area...

You could use the "AC wire" solution to get an Ethernet connection to the
other side,
and then just install another WAP over there.
OR - use the "AC wire" solution to go between the ADSL modem and the actual
router/AP
which then could be moved to a central location.

seaweedsteve
02-22-08, 11:07 AM
On Feb 21, 7:08 pm, t...@lavabit.com wrote:
> D. Stussy:
>
> > > I've got a wireless ADSL broadband router at one side of a building,
> > > but its signal is very poor at the other side of the building.
> > > Therefore I need some sort of "repeater".
>
> > Why not move the wireless router to the CENTER of the building?
>
> Phone line's at one side of the building. I don't want to run a long
> phone cable, nor do I want to run a long ethernet cable. Hence the
> want for a "repeater" of some sort.

Your problem sounds simpler than the solutions you propose. Here's a
few things to try:

1) Put a reflector on the antenna where it is to reach further

2) Reconsider running an ethernet cable to the center of the house if
it's relatively easy. This is the obvious starting point: placing the
wireless router to optimize coverage.

If it's still not quite enough, then a 5-7 dbi omni antenna may get
you over the hump. They are cheap.

3) use powerline networking to:
a: get the router centered in the house or
b: to get an ethernet signal on the other end. From there you can
connect directly or hang an AP on it

All of these solutions are easier and more reliable than the repeater
route.

Steve

lancer
02-15-09, 01:37 PM
Hi, please forgive me for digging up an old thread and for any other breaches of netiquette that I may commit, I'm new to this forum.

I have been trying to figure out how to set up an old-school wireless repeater using two wireless devices. (D-Link DI-624 & WRT54G w/DD-WRT) I know that I can just use my DD-WRT device to repeat the signal but I don't want to cut the throughput in half for the originating wireless broadcaster.

The situation:
I am receiving a wireless signal outside my home from a neighbor. I have permission to use the signal but not to access or alter any settings on the neighbor's router. A faint signal reaches a couple rooms of my house but not all of them. I would like to:
a) set up the Linksys/DD-WRT device with a cantenna to receive the signal from the source (this way I can also adjust the xmit power if needed)
b) Provide that captured signal from the Linksys device to the DI-624 via ethernet cable
c) Use the D-link to broadcast a wireless network within my home (on a different channel)

I know that this can be done. I know that it is what is referred to as 'Technology 1' in the thread above. I just don't know all the settings to use to make it happen.

When I was first researching this I could find several sites to help walk me through the process. Now that I have the hardware in place and I'm ready to begin, I can't find any.

If anyone can tell me what I need to know or direct me to a site that has the needed info, I would greatly appreciate it.

LR
02-17-09, 08:26 AM
On 16/02/2009 15:16, seaweedsl wrote:
> On Feb 15, 1:37 pm, lancer<lancer.3no...@no-mx.earth.universe.org>
> wrote:
>> I would like to:
>> a) set up the Linksys/DD-WRT device with a cantenna to receive the
>> signal from the source (this way I can also adjust the xmit power if
>> needed)
>> b) Provide that captured signal from the Linksys device to the DI-624
>> via ethernet cable
>> c) Use the D-link to broadcast a wireless network within my home (on a
>> different channel)
>>
>>
>> If anyone can tell me what I need to know or direct me to a site that
>> has the needed info, I would greatly appreciate it.
>>
>
>
> What you need to do is break it into two parts: Client bridge and AP.
>
> First you want a tutorial on setting up a client bridge in DD-WRT
>
> Try: http://www.wi-fiplanet.com/tutorials/article.php/3639271
>
> Or here: http://www.dd-wrt.com/wiki/index.php/Wireless_Bridge
> this wiki page link is over-complicated, but is good to review if you
> have problems. For starters, I suggest you just use the pictorial
> diagram and ignore the written instructions.
> direct link to pictorial: http://www.dd-wrt.com/wiki/index.php/Image:Standard_bridge_large.jpg
>
> Then setup your D-Link as an AP using it's interface instructions
> with some guidance from any AP setup tutorial. Here's one for DD-WRT:
>
> http://www.dd-wrt.com/wiki/index.php/Wireless_Access_Point
>
> Basically, give it a unique IP address within your subnet and connect
> from the DD_WRT router's LAN port to the D-Link's LAN port.
> Typically. You will have to sort out DHCP (which device is going to
> give out addresses) and turn off the firewall, but that's it.
>
> Oh, and set up your local security.
>
> Note: You may want to keep your house on a different subnet from your
> neighbor's, so you may want to go ahead and use DHCP on your AP
> instead of letting the main router assign it. If your main router is
> on 192.168.1.x subnet, then maybe setup your AP to 192.168.2.xxx
> subnet and hand out addresses from there. Setup your gateways to
> forward it to the next device.
>
> Maybe somebody else can chime in on the DHCP detail, but do study the
> AP setup and then see where you have questions.
>
> Steve
>
I don't think you will get a reply to this post Steve. If you look on
the speedguide.net forums there have been no posts shown that have
originated from alt.internet.wireless since 1st Jan 2009, the 2009 posts
originated from speedguide.net.
<http://forums.speedguide.net/forumdisplay.php?f=77>

seaweedsl
02-17-09, 11:04 AM
On Feb 17, 8:26 am, LR <l...@privacy.net> wrote:

> I don't think you will get a reply to this post Steve. If you look on
> the speedguide.net forums there have been no posts shown that have
> originated from alt.internet.wireless since 1st Jan 2009, the 2009 posts
> originated from speedguide.net.
> <http://forums.speedguide.net/forumdisplay.php?f=77>

Thanks for the heads up. I really dislike how these sites use the
newsgroups for content and rebrand it as their own. Worse if they
feed posts/topics into the newsgroups just to waste our time.

I'll try to remember to check where they came from first.

Steve