if anyone likes DX'ing with wlan...

PittSpeed Automotive PittSpeed Off Topic
1

Using a wireless LAN, I was having trouble when I started getting far enough away to start pulling from -80 to -90 db’s @ 1Mb/s transfer speed to the router. Lots of “refresh”'es necessary to get a page to load…

So, I was thinking of making an antenna…directional, tunable for specific channels in the 2.4 ghz ranges, etc.

But, before I do something like that, I was thinking, nah, let me read a little bit on-line. Came up with some stuff to do to the router (like jacking up the signal strength, installing a directional on the AP versus the compy, etc.), but it was not recommended to crank them up really high (read: rf signals and cancer), and the chances of destroying (“bricking”) the router trying to play with signal strength wasn’t worth it.

By trial and error and some understanding of how TCP/IP works on an optimized wired network, I found some settings in the Windows Registry that make a greater distance possible with a wlan card…without a directional antenna and without flashing the OS on a WRT54GL wireless AP and risking a bricked router. Read on…

OK, so I’m thinking maybe I have a decent signal, it’s just weak. Maybe the link to the AP’s getting interrupted, I don’t know exactly what’s happenning?

How can I figure it out…using NetStumbler, of course!!! NetStumbler is a program (located here http://www.netstumbler.com/downloads/) that allows charting signal strength versus time to allow you to map out in real time a particular AP’s signal strength at a given time during the scan.

So I walk out, yeah, I get a good -86 to -90 on that one corner of the house consistently. Consistent quality signal everywhere, just weaker than usually acceptable (for a “Default” OS anyway).

OK I can work with this…plug everything in and start tweaking.

regedit.exe:
…nav over to
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]

This registry key holds the values for TCP/IP service paramaters. There’s a bunch of settings that do not get put in there by default in a base OS install. They are described here:

http://support.microsoft.com/kb/314053

So I know I have a clean signal, but it’s weak. I’ll try dynamically reducing packet fragmentation client side, increase response tries and packet request tries, send shorter interval keep-alives, and limit the TCP maximum number of connections and reduce the time tcp time-wait state is held…

Here’s the additional numbers I came up with for a signal in the -86 to -90 dbs range:

[code=regedit4.reg]
REGEDIT4

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"EnablePMTUBHDetect "=dword:00000001
“IGMPLevel”=dword:00000000
“KeepAliveTime”=dword:00600000
“TcpMaxConnectRetransmissions”=dword:00000003
“TcpMaxDataRetransmissions”=dword:00000006
"TcpNumConnections "=dword:00000120
"TcpTimedWaitDelay "=dword:00000010



Basically, I tweaked the TCP settings to allow for a more "sloppy" or "lazy" connnection and made it so that less things were being held in a state where the OS had to keep track of it.

Results:  less interrupted page loads in browser (IOW, less dropped packets due to retransmission request time and number of times being hit).
2

This would probably confuse the shit out of a lot of people, but good researching on it…

3

im confused

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:cool:

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Thanks for the info. I have a nice wireless cloud covering my block. I’ll try messing with those settings on my laptop - it occasionally acts how you describe when I am in my sister’s garage. I think anntennas are my solution though since I am trying to make a wireless bridge between 4 points with multiple clients.

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Walk to different points and start netstumber to map out the good & bad signal strength (naming the log files with the location) and you’ll have a pretty good idea of signal strength wherever you 'stumble. Just remember to unbind TCP/IP from your network adapter while ‘stumbling so it’ doesn’t lock onto a particular AP…but, only while testing! Don’t forget to hook it back up to the card or you’ll go nuts trying to figure out why the card doesn’t work when you do want to lock on!

You might even benefit from hooking up a GPS if the area is large enough. NetStumbler will map the AP’s in a session by GPS coordinates. If you have a coarse resolution GPS, you’re probably not going to have good enough resolution for a garage/house. But for a larger area, the GPS hookup is invaluable.

What will be really cool is if someone would make a google earth/maps plugin to overlay GPS coords in mapspace versus datapoints you collected…like a popup-POI that states “found 2 AP. Signal strength better than -80db”. That’d be awesome.

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I’ve used netstumbler quite a bit during my war driving days. There was a site similar to what you say that used Yahoo maps on one of the wardriving forums I used to use. It was all filled in with user data so it wasn’t too great… but in large cities every person’s AP was basically listed there, haha.

I am using 4 WRT54G’s in my network. I use the modified firmware from sveasoft to connect my sister’s house, my cousin’s house, and my garage to my main AP in my house. We all live in the same neighborhood.

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I got a little tired of the dropped signals…



It works extremely well, and if it’s a common SSID it will allow you to lock in on a particular AP versus getting the dreaded “constant AP switchover” problem.

It consists of

1 Linksys USB54G wireless device, disassembled to allow the antenna to “float” ouside it’s housing.

1 3 lb. coffee can, metal. Maxwell House, because the only thing that brand is good for is the metal can for this device.

1 foot of duct tape

1 1’ tall camera tripod (or a puffs facial tissue box!)

9

the “AP Switchover” is called roaming…just like a cell phone it hops onto the next(stronger) signal…on built in wlan devices(laptops & some desktops) this can be configured to allow or disallow roaming…stop being a wuss and flast your router…i did my WRT54G which is now running on “Freeman” and boosted my signal up to 200mw…i can get my wireless signal about 8 houses up the street with no problem

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:rofl::rofl::rofl:

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I wanted to put it in terms that everyone would understand, hence the quotes…Believe me, I know what it’s called and why it’s beneficial sometimes! :slight_smile:

Hope you’re not sitting anywhere near something that RF-hot.

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hell no…its buried behind our china cabinet in the dining room that nobody ever eats in

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i use wired internets… it’s the old school baller way to be hardcore…