Category Archives: Wireless

Budget Wireless Distribution

Working for a non-profit organization requires a special type of ingenuity at times. In this case it was due to the requirement of setting up easy to use systems that are sustainable, yet affordable. Below are some pictures that show a wireless distribution system that I helped setup that serves the needs of 10 families, 4 guest apartments, and 2 work shops.

The Internet access is being provided via a business DSL modem in the lower level of the building with a red star on it. From there, a multi-purpose wireless router (RT-N16) is configured with DD-WRT and acts as the LAN’s gateway and firewall. Other common services it provides to the LAN include ones like local DNS, static DHCP, DynDNS client, SSH client/server, and OpenVPN client/server. It also has real time traffic monitoring, traffic graphs over time, QOS capabilities, and other exciting features. Nobody actually uses the wireless from the RT-N16 though, as it is being used only as a powerful, yet inexpensive wired appliance.

From there the only wired client connected is the main AP, a Bullet M2 HP. This little piece of equipment is quite exciting. A tough 600 mW self contained outdoor router built on Linux. It has already survived through the year long seasonal variations and is rated to operate at temperatures between -40C to 80C. Along with a 9dBi outdoor omnidirectional antenna mounted to it, they provide over 600,000 square ft. of network coverage through trees, hills and buildings with users reliably connecting in their homes over 250 feet away (though with the right antenna and conditions, the Bullet M2 HP is rated to perform at distances of over 50km away).

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WDS Bridging Experiences

At the moment, our best solution for network coverage to multiple buildings is wireless. I have been planning out various solutions to improve our system (fiber optics, dslam, or a better wireless setup) but wanted to share what we have now and how well it has worked in this particular area of our property.

WDS Repeating Map

The image above shows the main buildings that are being linked. The main router sits in an upstairs window and is a:

Linksys WRT300N

  • Runs DD-WRT V24 – SP2 (Beta)
  • Has original antennas
  • Has the following properties set (among others, these are the interesting ones)
    • Wireless – Basic Settings
      • Mode: AP
      • Network Mode: BG-Mixed
      • Channel: 11 – 2.462 GHz
      • SSID Brodcast: Enable
    • Wireless – Advanced Settings
      • TX Power: 71
    • Wireless – Security
      • Security Mode: WEP (I haven’t tested WPA2 with WDS yet, and I understand that WEP can be cracked easily)
    • Wireless – WDS
      • The three router’s MAC addresses are filled in, and are set to “LAN”

The three client WDS routers are also sitting in windows, and are on the first level of the buildings that they are in. They repeat the same SSID, and run on channel 11.

Buffalo WLI-TX4-G54HP

  • Originally purchased as an ethernet bridge, it is now running DD-WRT V24 – SP2 (Beta)
  • Replaced the stock antenna with a 9 dBi omni-directional
  • Is on the 72.6m link

(2) Belkin F5D7230-4 routers

  • WDS on the stock firmware works with DD-WRT, sweet!
  • These are unmodified, running with their tiny fixed (two) omni-directional antennas
  • One is on the 35.4m link, and the other on the 88.5m link

This setup has been going for weeks without an issue, and has served upwards of six families, a two person office, a fifteen to twenty person office, and a classroom with sixteen students.

We have other areas on the same property that have wireless access between buildings, but are nowhere near as complete as this arrangement. If we do end up using wireless to unify the property’s networks, then I will start looking into site to site links, multiple gateways, OLSR, and other mesh technologies. I have my doubts as to how well WDS scales. Has anyone had positive results with professional mesh solutions built on DD-WRT and Linksys hardware?


Wireless keyboard

I am happy to report that I am typing this blog entry from my first wireless keyboard… it was free and it even had two rechargeable AAA batteries inside! The only issue I have with it, is that it is infrared… meaning it has to be pointed directly at the receiver, and also, I can’t read the monitor from this far away. :-)


Woktenna

Here is a pic of my semi professionally made (that is I spent time in the wood shop) dish setup for my D-Link DWL-122 802.11b 11 Mbps USB Adapter:

usb-wifi-wok-dish-closeup.jpg

To develop this dish setup, I did the following:

  1. Used ideas from http://www.usbwifi.orcon.net.nz/
  2. Mostly the focal point math from http://www.usbwifi.orcon.net.nz/usbscoop.jpg
  3. Took a wok lid and removed the wooden handle
  4. Cut a small length of wood (a) (this gets the USB dongle to the calculated focal point)
  5. Cut a small block of wood (b) (this connects the dish to the camera stand)
  6. Drilled the appropriate holes into the the two pieces of wood
  7. Put a long screw into the block of wood (b) that extends through the other side (this joins the length of wood (a), dish, and block together)
  8. Embedded a nut the size of the camera stand’s butterfly bolt into the block of wood (b) and used a hardening putty to keep it there
  9. Put two thumb tacks into the length of wood (a) to hold bands around the usb dongle

The whole setup collapses in seconds, is aimable, portable, and gave me terrific gain… though I don’t have comparison screenshots. This is a great setup for a laptop on the go trying to get the distant wifi access.

usb-wifi-wok-side-by-side-cantenna-wrt54g-bridge.jpg

Here, the woktenna is seen by the Cantenna. I had the Cantenna hooked up to a wrt54g running dd-wrt as a wireless bridge to another access point.

See also:


WiFi Antenna

After reading through some websites and gleaning information from different sources, I decided to experiment with some antenna design. Even though I don’t have much of an artistic/creative mindset I figured I had some tools and a roll of duct tape… so I gave it a go. The first idea I tried to implement was the Pringles “Cantenna”. It is a neat design, plus I was able to munch on some ketchup flavored Pringles for my first time here in Canada. To make a long story short… it didn’t work with my USB adapter… partially because I changed the design in the process. Probably not good, right?

So moving on I found an awesome webpage called Poor Man’s WiFi. I must say, this is a masterpiece of an idea. They simply took the dish concept, like from a satellite dish, and put a USB WiFi adapter to it using common household items. For my pseudo WokFi, common items I could fine in my area happened to be a spaghetti strainer, rather than a Chinese cooking vat scoop.

Items I used:

1 USB WiFi adapter
1 Spaghetti Strainer
1 roll of duct tape
1 ruler
->
->
->
->
$9.99 ($29.99 mail-in rebate)
Free (graciously taken from wife)
$4.99? (I can’t remember)
$0.99? (I can’t remember)
Karl holding his spaghetti strainer usb 802.11 2.4 ghz antenna The spaghetti strainer 802.11 2.4 ghz antenna
The dwl-122 connection utility that shows the signal strength without the dish attached The dwl-122 connection utility that shows the signal strength with the dish attached

While if I made a permanent structure it would have much more sturdiness to it, this one worked great. Check out the screen shot pictures. I was able to get a 24% increase in signal strength and 40% increase in link quality. Unfortunately I wasn’t able to get Netstumbler to work with the DWL-122 USB adapter correctly. So actual decibel and wattage information is beyond me. I have estimated by pacing that the distance the signal is traveling is 126.4 feet (38.5 meters). The signal is originating off of a DI-624 AirPlus Extreme-G router, travels through a window, across the yard, and another window.


WiFi in the News

The first wifi news story I would like to talk about exposes some of my own hobby radio interests… though I haven’t tried any of this sort of thing yet. A couple of teen guys at the DEFCON hacker conference were able to establish a 55.1 mile unamplified wifi connection. Obviously this is point-to-point but it raises an interesting topic. Wifi sharing. Neighbors across the country should be setting this sort of thing up. It would dramatically reduce the cost of broadband for consumers, bring neighbors together, increase the use of homebrew equipment, and provide a partial solution the “last-mile” broadband problem.

Read the article from Wired News.

In other news, today, I am pleased to announce my laptop runs Ndiswrapper and the 802.11G Intel Centrino drivers. I did it and it wasn’t hard! I am happy. I write this article while running on the wireless network here at home.

Here are some links to get those who would like to do the same started:

http://ndiswrapper.sourceforge.net/wiki/index.php/Intel2200
http://web.bii.a-star.edu.sg/~kuobin/linux/wireless.html
http://ndiswrapper.sourceforge.net

I also found the INSTALL file in the Ndiswrapper tar ball to be helpful.


The World of Wireless

I’ve embarked on a strange journey in computer land. The other day I decided it was time to find out what all this wireless talk was all about. 802.11g this, and WIFI that, WEP this, and WAP that! HA!

My equipment thus far is a WRT54G Linksys router… (I think this was a good buy as it has a lot of “community” backing and seems to be quite “configurable.”) and the wireless card is the WMP55AG. It supports 802.11a/b/g and I have it running on Linux… kind of.

The madwifi drivers were difficult to install, but I found someone who knew what they were doing that did it before, and they helped. Whew… where do I go from here?