Connecting over 400m. Bridge or Repeater mode?

I'm getting inconsistent results with Linksys WAP54G over about 400m
with bursts of high speed then periods of nothing.

Both Linksys are set to repeater mode.

Far end has cantenna on one of the aerials and the other aerial is
removed. Ethernet to hub.

Near end have tried with both aerials on and also one aerial to
cantenna with other standard aerial picking up from notebook.

(view with fixed font for clarity)

(( )) represent wireless signal

Home
Notebook )) ((Near Linksys ))Cantenna or standard aerial

|
|
|
~300m | House
Tree |
|
~380m Over an office roof
|
Far Linksys )) Cantenna
|
Office Hub

I seem to get less dropouts when the near (home) linksys has the two
supplied aerials fitted and placed in the window but a low speed. The
fastest results are when one aerial is connected to the cantenna at
home but then it will then drop/lock out.

The aerials are set to diversity mode and I wonder whether it can get
confused as to whether it is setting the aerials speeds to the
notebook or to the distant cantenna.

The "obstruction" of House and Tree is about 2 - 3 metres horizontally
and the office roof is about 1m vertically.

Any suggestions welcomed.

Thanks

--
TonyL

"Tony Lewis" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I'm getting inconsistent results with Linksys WAP54G over about 400m
> with bursts of high speed then periods of nothing.
>
> Both Linksys are set to repeater mode.
>
> Far end has cantenna on one of the aerials and the other aerial is
> removed. Ethernet to hub.
>
> Near end have tried with both aerials on and also one aerial to
> cantenna with other standard aerial picking up from notebook.
>
> (view with fixed font for clarity)
>
> (( )) represent wireless signal
>
> Home
> Notebook )) ((Near Linksys ))Cantenna or standard aerial
>
> |
> |
> |
> ~300m | House
> Tree |
> |
> ~380m Over an office roof
> |
> Far Linksys )) Cantenna
> |
> Office Hub
>
> I seem to get less dropouts when the near (home) linksys has the two
> supplied aerials fitted and placed in the window but a low speed.
The
> fastest results are when one aerial is connected to the cantenna at
> home but then it will then drop/lock out.
>
> The aerials are set to diversity mode and I wonder whether it can
get
> confused as to whether it is setting the aerials speeds to the
> notebook or to the distant cantenna.
>
> The "obstruction" of House and Tree is about 2 - 3 metres
horizontally
> and the office roof is about 1m vertically.
>
> Any suggestions welcomed.

It sounds like a weird config. Ordinarily when you put a WAP in
repeater mode
the ethernet is disabled but you say the remote site connects to a hub
via ethernet.
Im really surprised it works at all that way, but then again I aint
seen everything.
If you want wireless at the home end then I would use AP mode there
and AP
Client mode at the Remote but his may depend on the number of PCs at
the remote site.
AP Client usually only handles "A Client", not multiples unless a
router is involved or you can use
bridge mode on both ends but neither end will have wireless client
capability unless you add an AP on that end.
Unless you can get the signals out of the trees and house ( a clear
Fresnel zone) then you may
continue to have intermittent type problems.

On Mon, 7 Mar 2005 15:10:09 -0600, "Airhead"
<(E-Mail Removed)> wrote:

>
>"Tony Lewis" <(E-Mail Removed)> wrote in message
>news:(E-Mail Removed)...
>> I'm getting inconsistent results with Linksys WAP54G over about 400m
>> with bursts of high speed then periods of nothing.
>>
>> Both Linksys are set to repeater mode.
>>
>> Far end has cantenna on one of the aerials and the other aerial is
>> removed. Ethernet to hub.
>>
>> Near end have tried with both aerials on and also one aerial to
>> cantenna with other standard aerial picking up from notebook.
>>
>> (view with fixed font for clarity)
>>
>> (( )) represent wireless signal
>>
>> Home
>> Notebook )) ((Near Linksys ))Cantenna or standard aerial
>>
>> |
>> |
>> |
>> ~300m | House
>> Tree |
>> |
>> ~380m Over an office roof
>> |
>> Far Linksys )) Cantenna
>> |
>> Office Hub
>>
>> I seem to get less dropouts when the near (home) linksys has the two
>> supplied aerials fitted and placed in the window but a low speed.
>The
>> fastest results are when one aerial is connected to the cantenna at
>> home but then it will then drop/lock out.
>>
>> The aerials are set to diversity mode and I wonder whether it can
>get
>> confused as to whether it is setting the aerials speeds to the
>> notebook or to the distant cantenna.
>>
>> The "obstruction" of House and Tree is about 2 - 3 metres
>horizontally
>> and the office roof is about 1m vertically.
>>
>> Any suggestions welcomed.
>
>It sounds like a weird config. Ordinarily when you put a WAP in
>repeater mode
>the ethernet is disabled but you say the remote site connects to a hub
>via ethernet.

Seems as though it has some dual mode abiltiy then?

>Im really surprised it works at all that way, but then again I aint
>seen everything.
>If you want wireless at the home end then I would use AP mode there
>and AP
>Client mode at the Remote but his may depend on the number of PCs at
>the remote site.

I definitely want to connect the Remote Linksys to the wired office
network. Only a handful of PC's and a couple of file servers but it
would be great to:

a) piggy back onto the office broadband
b) access the office systems

from home.

>AP Client usually only handles "A Client", not multiples unless a
>router is involved or you can use

I'm not using AP Client mode at all.

>bridge mode on both ends but neither end will have wireless client
>capability unless you add an AP on that end.

>Unless you can get the signals out of the trees and house ( a clear
>Fresnel zone) then you may
>continue to have intermittent type problems.
>
The farmer won't move his house

Perhaps I have asked the question the wrong way round. What do you
suggest is the right way to set up the devices for:

A couple of wireless laptops at home so that they can see eachother
and both connect to the office network (400m) away with line of sight?


--
TonyL

On Mon, 7 Mar 2005 15:10:09 -0600, "Airhead"
<(E-Mail Removed)> wrote:


>router is involved or you can use
>bridge mode on both ends but neither end will have wireless client
>capability unless you add an AP on that end.

Am I correct in understanding that in bridge mode no-one in the middle
will be able to jump into my network? If so that is a good thing as I
would prefer to have that security.


--
TonyL

On Mon, 07 Mar 2005 14:20:52 GMT, (E-Mail Removed) (Tony Lewis)
wrote:

>I'm getting inconsistent results with Linksys WAP54G over about 400m
>with bursts of high speed then periods of nothing.

How long are the bursts of high speed? How long are the times with no
traffic? Just guess at approximate values. The times are very useful
for determining a possible source of interference?

Have you tried using different channels?

>Both Linksys are set to repeater mode.

Bad idea for initial testing. Set it to the transparent bridge mode.
That will keep other wireless users and devices from associating and
only allow traffic between endpoints.

>Far end has cantenna on one of the aerials and the other aerial is
>removed. Ethernet to hub.
>
>Near end have tried with both aerials on and also one aerial to
>cantenna with other standard aerial picking up from notebook.

I'm guessing that you're at the bitter edge of marginal performance.
If I knew how much pigtail and coax cable you had between the WAP54G
and antenna, I can make a better guess. Let's play with the numbers
and please correct my guesswork.

I'll guess that you have the cantenna end connected with a rather long
and thin (LMR-240) pigtail with about 6dB loss including connectors.
The cantenna is good for about 8dBi gain, if built correctly. I have
no clue how fast your burst of performance are running and therefore
cannot guess at what association speed you're running. I'll assume
16Mbits/sec OFDM for a receiver sensitivity of -88dBm. The stock
rubber ducky antennas have about 0dBi gain. In theory, they should be
more, but that's what I've measured. Grinding the numbers.

TX power = +15dBm (Cantenna end)
TX coax loss = 6dBm
TX antenna gain = +8dBi
Distance = 400 meters (0.25 miles)
RX antenna gain = 0dBi
RX coax loss = 0.5dBm
RX sensitivity = -88dBm (6Mbits/sec OFDM)
Desired fade margin = ????

Plugging into:
http://www.terabeam.com/support/calculations/som.php
I get a fade margin of: 10.3 dB which is awful. The way fade margin
works is that the rated sensitivity of -88dBm will yield about 10^5
BER (bit error rate) which is a rather flakey and useless connection.
You have a fade margin of 10dB (about 10 times) more than that
resulting in a substantially better BER. However, the errors will
still be there and can be statistically estimated.
Fade Margin Reliability
10 dB 90
20 99
30 99.9
40 99.99

However, this is under ideal conditions and does not include the
attenuation of the house and tree as well as the fact that they're in
the Fresnel zone and will cause some signal to be diverted via
diffraction. Without a description, I can't offer a guess as to how
much additional path loss these will present, but I'm fairly sure it
will be more than 10dB. In other words, this link is not going to
work reliably.

>(view with fixed font for clarity)
>
> (( )) represent wireless signal
>
>Home
>Notebook )) ((Near Linksys ))Cantenna or standard aerial
>
> |
> |
> |
>~300m | House
> Tree |
> |
>~380m Over an office roof
> |
> Far Linksys )) Cantenna
> |
>Office Hub
>
>I seem to get less dropouts when the near (home) linksys has the two
>supplied aerials fitted and placed in the window but a low speed. The
>fastest results are when one aerial is connected to the cantenna at
>home but then it will then drop/lock out.
>
>The aerials are set to diversity mode and I wonder whether it can get
>confused as to whether it is setting the aerials speeds to the
>notebook or to the distant cantenna.
>
>The "obstruction" of House and Tree is about 2 - 3 metres horizontally
>and the office roof is about 1m vertically.
>
>Any suggestions welcomed.

In order of importance.

1. Get line of sight. Relocate the antennas so that there's nothing
in the way and that you have Fresnel zone clearance. If you can't get
LOS and clearance, you will have flakey performance (guaranteed).

2. Get bigger antennas. You want to have at least 20dB fade margin
with the above calculations. My guess is that you need at least
+15dBi gain antennas at both ends. If you have an aesthetics problem,
you might want to try add on reflectors:
http://www.freeantennas.com/products.htm

3. Turn off the repeater mode and use the bridge mode for testing.

4. Try a different channel in case you are having intereference
problems.

5. Position antennas as close to WAP54G to reduce coax losses.

6. Fix the speed to 6MBits/sec OFDM. Do not let it rate adjust
itself. AP's spend an awful long time adjusting their speeds for
noisy connections.

7. Run the numbers. Aim for 20dB fade margin. It's not that
difficult. If it doesn't work on paper, it's not going to work on the
air. Actually, I'm rather amazed that it works at all with your
existing configuration.


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

On Mon, 07 Mar 2005 14:20:52 GMT, (E-Mail Removed) (Tony Lewis)
wrote:

>I'm getting inconsistent results with Linksys WAP54G over about 400m
>with bursts of high speed then periods of nothing.

Here you say 400 meters.

>Home
>Notebook )) ((Near Linksys ))Cantenna or standard aerial
> |
>~300m | House
> Tree |
> |
>~380m Over an office roof
> |
> Far Linksys )) Cantenna
> |
>Office Hub

Here, I add 300m and 380m and get 680meters. Is it 400m or 680m?


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

On Tue, 08 Mar 2005 09:58:32 -0800, Jeff Liebermann
<(E-Mail Removed)> wrote:

<snipped>
>7. Run the numbers. Aim for 20dB fade margin. It's not that
>difficult. If it doesn't work on paper, it's not going to work on the
>air. Actually, I'm rather amazed that it works at all with your
>existing configuration.
>


A lot to digest there Jeff and it'll be a few days before I will be
able to test out and report back.

A couple of quick comments:

1) Have tried to keep coax cable lengths down so that there is a
theoretical net gain

2) I have no latitude to change the horizontal path. It is the only
clear line of sight I have. I could go higher but cable lengths will
go up (I'm already on a shed roof the office end to get a line of
sight).

3) I've hit around 400kbits/sec (with cantennas both ends) which would
be acceptable if sustained. Try to download a 3mb file for testing
(from the LAN not the net) and after a couple of attempts the systems
seem to lock and do not recover. I then have to revert to the "rubber
duckies" in the window. Typically then I'm down to 100kbit/sec but
sustainable.

4) There is another cantenna arrangement about 30 metres to one side
at the office end. The office end cantenna is pointing at 90 deg to
it but I'm sure it is able to pick up some signal as I can with my
laptop if standing under the aerial.

5) Bridge mode seems my next test with probable channel change.

I'll report back.



--
TonyL

On Tue, 08 Mar 2005 10:31:51 -0800, Jeff Liebermann
<(E-Mail Removed)> wrote:

>On Mon, 07 Mar 2005 14:20:52 GMT, (E-Mail Removed) (Tony Lewis)
>wrote:
>
>>I'm getting inconsistent results with Linksys WAP54G over about 400m
>>with bursts of high speed then periods of nothing.
>
>Here you say 400 meters.
>
>>Home
>>Notebook )) ((Near Linksys ))Cantenna or standard aerial
>> |
>>~300m | House
>> Tree |
>> |
>>~380m Over an office roof
>> |
>> Far Linksys )) Cantenna
>> |
>>Office Hub
>
>Here, I add 300m and 380m and get 680meters. Is it 400m or 680m?
>

the distances are absolute from Home. 400m total. All the potential
obstructions are around the office end.


--
TonyL

On Wed, 09 Mar 2005 12:21:13 GMT, (E-Mail Removed) (Tony Lewis)
wrote:

>1) Have tried to keep coax cable lengths down so that there is a
>theoretical net gain

How much coax in meters? What type of coax? I like numbers, not
vague descriptions.

>2) I have no latitude to change the horizontal path. It is the only
>clear line of sight I have. I could go higher but cable lengths will
>go up (I'm already on a shed roof the office end to get a line of
>sight).

Think about mounting the WAP54G in an outdoor box to reduce the coax
length. See:
http://www.sveasoft.com/articles/armored/
(see tiny "next" in lower right of page)
for the general idea. One correction. The WAP54G and WRT54G will run
on anything between about 4VDC and 15VDC. No need for PoE (power over
Ethernet) converter. Just run two extra wires from the CAT5 cable to
power and ground from the 12VDC wall wart. There will be cable loss
but the WRT54G power supply regulator will not care.

>3) I've hit around 400kbits/sec (with cantennas both ends) which would
>be acceptable if sustained.

That's about what you will get at the very slowest speed of 1Mbit/sec.
The access point has decided that the path is so bad, that it has
slowed down to it's slowest data rate in a heroic effort to maintain
communcations.

>Try to download a 3mb file for testing
>(from the LAN not the net) and after a couple of attempts the systems
>seem to lock and do not recover.

Yep. That's usually what happens.

>I then have to revert to the "rubber
>duckies" in the window. Typically then I'm down to 100kbit/sec but
>sustainable.

Actually, you're down to about 450kbits/sec nominal thruput with a
huge number of lost packets and resends. I'm amazed that it's
"sustainable" as it usually hangs if the packet loss is excessive.
Try playing some 64kbit/sec streaming audio through the link and you
can actually hear the stalls and resends.

>4) There is another cantenna arrangement about 30 metres to one side
>at the office end. The office end cantenna is pointing at 90 deg to
>it but I'm sure it is able to pick up some signal as I can with my
>laptop if standing under the aerial.

Oh-oh. Trouble. Try to identify (with Netstumbler) the channel that
they're using and find another. Cantennas are NOT very directional:
http://www.learnbydestroying.com/pic...400/index.html
At 90 degress, you're approximately either -8dB or -15dB down
depending on orientation.

>5) Bridge mode seems my next test with probable channel change.

I goofed. I thought you had two WAP54G radios and didn't see the
laptop as one end. That cannot be used in the bridge mode. The
WAP54G has to be in the access point mode. Try a different channel
(1, 6 or 11) but I don't think that will help. You need a better RF
path.

>I'll report back.


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

On Wed, 09 Mar 2005 09:03:12 -0800, Jeff Liebermann
<(E-Mail Removed)> wrote:

>
>>4) There is another cantenna arrangement about 30 metres to one side
>>at the office end. The office end cantenna is pointing at 90 deg to
>>it but I'm sure it is able to pick up some signal as I can with my
>>laptop if standing under the aerial.
>
>Oh-oh. Trouble. Try to identify (with Netstumbler) the channel that
>they're using and find another. Cantennas are NOT very directional:
> http://www.learnbydestroying.com/pic...400/index.html
>At 90 degress, you're approximately either -8dB or -15dB down
>depending on orientation.
>
We're both on Channel 11

>>5) Bridge mode seems my next test with probable channel change.
>
>I goofed. I thought you had two WAP54G radios and didn't see the
>laptop as one end. That cannot be used in the bridge mode. The
>WAP54G has to be in the access point mode. Try a different channel
>(1, 6 or 11) but I don't think that will help. You need a better RF
>path.
>

I was planning to initially use an ethernet cable to connect one
laptop to the WAP54G at home to test. I presume that will allow the
WAP54G to be in bridge mode. If all works out ok I'll put in another
access point in normal access point mode then connect that to the
WAP54G so that both laptops can either talk to eachother or to the
office lan/broadband.

The WAP54Gs have dual aerials currently set to diversity mode. With
bridge mode I plan to set the aerial to only the one connected to the
cantenna.

I've tried to find an answer to a relative straightforward question
but there is too much noise - what is repeater mode for if it is not
for what I am doing?


--
TonyL