Topic: Link over 20 km!!!

Is possible with wrt54g create a link over 20 km from ap to client?
I want to test but don't work,the signal is -65 /-70 dbm and i see the beacon but is not possible create a net (no ping...)!
Help me...
tortelli2

Re: Link over 20 km!!!

Flash my latest snapshot at http://downloads.openwrt.org/people/nbd/whiterussian/ and set wl0_distance=20000 (or more, if that's not enough)

Re: Link over 20 km!!!

20 km? That's a lot.

Perhaps with a dedicated antenna on both sides (with a "dish" reminding satellite antennas), yes, but I'd ask on a list that deals primarily with wireless networking.

I myself made about 6 km link once (it still works) a couple of years ago, it took some time to get the know-how and to make it working.

No wrt54 though, I used some planet equipment.

WPKG - http://wpkg.org
Software deployment / silent installation with Samba

Re: Link over 20 km!!!

The problem here is that due to wrong ACK timings you can't do much more than 7 km with a standard configuration. My snapshot fixes that by allowing you to tweak the timings for a much higher distance.
I believe without these tweaks it is not possible to get any data through with a WRT at that distance...

Re: Link over 20 km!!!

nbd wrote:

Flash my latest snapshot at http://downloads.openwrt.org/people/nbd/whiterussian/ and set wl0_distance=20000 (or more, if that's not enough)

In this link i see 2 .bin from wrt54g, whitch i sent in my router?
Where is the list of command-istruction?
Thanks of all
N.B. I use 2 dish of 120 cm of diameter....

Re: Link over 20 km!!!

Flash openwrt-wrt54g-squashfs.bin
Then log in and run:
nvram set wl0_distance=20000
nvram commit
wifi
Do this with both routers.

7 (edited by doddel 2006-03-14 19:14:54)

Re: Link over 20 km!!!

should be no problem with 1m20 parabolic antennas.
Am running a 9 km link here with 0.8 m parabolas on either side, no external amplifiers, WRT54G v3.1, and get 8 MByte effective data througput.

Your post contains very little specific data (which equipment, which software, which configuration etc. etc. ) to give a hint on what could cause the problem of not getting associated or authenticated and getting ping responses.

In general it would be a good idea to go about it as follows:
1) flash the software that nbd has indicated;  the distance setting is essential to get high data throughput.
However, also without distance adjustment, i could always get ping responses over 9 km.  So something more basic in the configuration may be wrong.
2) get the boxes connected and pinging while being side to side next to your PC. Make sure that after loosing contact for whatever reason, e.g. power interruption, they get associated again by themselves without your involvement.
3) only then start experimenting long distance.

For the boxes to get easily associated and pinging, a signal to noise ratio of about 8 - 10 dB is required in mode g.
For a reliable connection at say 36 Mbps g mode modulation or better you'll need like 15-18 dB. (Linksys wrt54g experimental results with OpenWrt)
The radio driver will reduce datarate in a few steps to only 1 or 2 Mbps when the distance setting is not done.
The S/N ratio you can see by issueing 'iwconfig eth1' and subtracting noise level from signal level.
To see the modulation data rate i use the wl package and 'wl rate' command.

Re: Link over 20 km!!!

@doddel: it makes sense that the 20km link doesn't give any ping response. the link is probably so long that the ack doesn't arrive in the allowed timeframe after a few retransmits.

9 (edited by vincentfox 2006-03-14 19:09:29)

Re: Link over 20 km!!!

Does original poster have  clear air?

If you have competing 2.4 GHz RF sources in the intervening distance, that noise is a big problem.

Re: Link over 20 km!!!

@nbd: you may be right, let's see what 'tortelli2' reports. In my experiments pinging always was possible as soon as association and authentication had happened, be it at low data rate. Perhaps the very same timing problems prevent association to start with.

11 (edited by tortelli2 2006-03-14 21:07:31)

Re: Link over 20 km!!!

My actual configuration is:
-2 wrt54g v2.2 with firmware alchemy v6.XX from svasoft.
-2 dish 120 cm diameter,in 1 location i use cavity filter 4 cell for reduce noise over channel 8.
-the beacon received have a signal of -65/ -75 dbm .
-power setting 150 mw.
-data rate 1 mbps
I don't now if with alchemy firmware is possible set delay form tx-rx packet data....
The next day i test this firmware with setting of distance and report here the results !!!
Thanks and sorry from my bad english!
Tortelli2 or IW4ENL

12

Re: Link over 20 km!!!

Alchemy won't do you much good there. Better get rid of it quickly smile

13 (edited by doddel 2008-03-16 20:52:33)

Re: Link over 20 km!!!

Careful with the cavity filter; it should at least have a passband of 5 channels wide because the g mode signal is not confined to 1 channel spacing as is normally implied when talking about channels. The 802.11g signal is much wider then 1 channel spacing.
This forum is about OpenWrt and also would also recommend to change to that firmware; in this case the very latest version nbd referred to. It will then be easier to help you further and compare results and others here can benefit from your experiences.

14 (edited by tortelli2 2006-03-15 01:08:40)

Re: Link over 20 km!!!

I use data rate of 1 mbps in b mode for my test and channel 1 ,the cavity filter is more larger of 22 mhz.
Witch program is better and simple use for connect in ssh with router?
Is possible to find the updated list of command wl0 for setting of this router?
73

Re: Link over 20 km!!!

Some of the guys here in Melbourne Wireless have a 14km link.  It used to have a data rate of roughly 60KBytes/s, then when they used the dctrl utility and set it to 22000 the rate jumped to 1130KBytes/s.  Pretty impressive!