Deploying a cheap Wireless Access Point 802.11g in Linux with Madwifi

One of my main goals in the infraestructure that I am trying to setup at my home network is to deploy a cheap Access Point to be able to connect to the Internet just sitting in my living room :) (I know, I am too lazy). I am editing the post that I made because I forgot to mention two main advantages of this wireless card. One, of couse as mentioned in the subject, is very cheap, but the other two are, it is a cheap 802.11g wireless card, the most of the documentation that I found was only about Access Points of 802.11b, and the most interesting feature of madwifi, is the use of VAPs or Virtual Access Points. The advantage of this, it is that you could setup several virtual interfaces, in different modes, so you could have a virtual interface to provide connection without any password, another encrypted using WEP or WPA2, or establish managed mode and bridge your Access Point with another one (which is very good for Wireless communities).


Although the wireless interface of the Dell 600 Latitude that I have, has an Intel 2100 wifi interface (therefore b and not g), I wanted to deploy a g (and as any g AP, backwards compatible with b). For that I searched a little bit in Google and I discovered madwifi and the Atheros support. Another requirement was that the card should be PCI, for cutting the cost of having a PCMCIA card and then a PCI adapter for PCMCIA). After a few weeks researching I found the SMCWPCI card which has an Atheros chipset and only for about 20 euros. I bought first the 54 Mbps card (the one in the image above) , and like everything went right I bought an extra card and an antenna with a better gain (5 dBi)like the one below. The antenna provided with the card has only 2 dBi. The difference was, that the signal could go through two walls and reach my living room :)

The first PCI card was 54 Mbps, and worked fine in a Pentium MMX with 128 Mb running RedHat 7.3.

In the recycling center of my town I discovered some trashed PCs, and discovered someone left a AMD XP 1800 and AMD 1000, which I turned in two desktop PCs which respectively became my desktop computer and an extra desktop PC for my family. I several old PCs, Pentium II and III and I decided to turn the Pentium IIs into my routers/wifi APs to try to do better things like OpenVPN or things like that.

When I bought the extra SMC card for my family AP, I did not realize that It was actually a 108 Mbps card. Assuming that It was a 54 Mbps gave some headaches, but finally I managed also to make it to work.

The driver for using this card is madwifi (http://madwifi.org). Following the instructions was pretty easy, I went for the hardest way and try to compile a kernel with the madwifi driver patched in it, as I did with my RedHat (I compile a kernel 2.4.x), but as I was using Debian, in the end I decided to try to compile the driver following the instructions from madwifi for Debian.

I added the following entries in my sources.list :

# Testing
deb http://ftp.au.debian.org/debian testing main contrib non-free
deb-src http://ftp.au.debian.org/debian testing main contrib non-free

and then issue:

$ su
# apt-get update
# apt-get install madwifi-source
# apt-get install madwifi-tools
# m-a prepare
# m-a a-i madwifi

This left the madwifi driver installed, then you could load the driver using modprobe:

#modprobe ath_pci

And you will get something like:

ath_hal: 0.9.16.16 (AR5210, AR5211, AR5212, RF5111, RF5112, RF2413, RF5413)
wlan: 0.8.4.2 (svn 1451)
ath_rate_sample: 1.2 (svn 1451)
ath_pci: 0.9.4.5 (svn 1451)
ACPI: PCI Interrupt 0000:02:02.0[A] -> Link [LNKC] -> GSI 10 (level, low) -> IRQ 10
wifi0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
wifi0: 11g rates: 1Mbps 2Mbps 5.5Mbps 11Mbps 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps
wifi0: H/W encryption support: WEP AES AES_CCM TKIP
wifi0: mac 5.6 phy 4.1 radio 1.7
wifi0: Use hw queue 1 for WME_AC_BE traffic
wifi0: Use hw queue 0 for WME_AC_BK traffic
wifi0: Use hw queue 2 for WME_AC_VI traffic
wifi0: Use hw queue 3 for WME_AC_VO traffic
wifi0: Use hw queue 8 for CAB traffic
wifi0: Use hw queue 9 for beacons
wifi0: Atheros 5212: mem=0xd0000000, irq=10
ACPI: PCI Interrupt 0000:03:00.0[A] -> Link [LNKC] -> GSI 10 (level, low) -> IRQ 10
wifi1: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
wifi1: 11g rates: 1Mbps 2Mbps 5.5Mbps 11Mbps 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps
wifi1: turboG rates: 6Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps
wifi1: H/W encryption support: WEP AES AES_CCM TKIP
wifi1: mac 7.9 phy 4.5 radio 5.6
wifi1: Use hw queue 1 for WME_AC_BE traffic
wifi1: Use hw queue 0 for WME_AC_BK traffic
wifi1: Use hw queue 2 for WME_AC_VI traffic
wifi1: Use hw queue 3 for WME_AC_VO traffic
wifi1: Use hw queue 8 for CAB traffic
wifi1: Use hw queue 9 for beacons
wifi1: Atheros 5212: mem=0xd2000000, irq=10

and then you just have to add it to the modules:

# echo ath_pci >> /etc/modules

After this, starts the worst part, to make it to work when the system boots :)

The madwifi website recommends the use of pre-up and post-up scripts, as mentioned in this web page

My intention was to setup the card in master mode and tried it to add it in the interfaces script:

iface ath0 inet static
pre-up wlanconfig ath0 destroy
pre-up wlanconfig ath0 create wlandev wifi0 wlanmode ap
pre-up iwconfig ath0 essid breinestorm rate auto
address 192.168.1.1
netmask 255.255.255.0
network 192.168.1.0

but didn´t work properly, then I add a bash script to the /etc/rc.local script, which is the last service to run:

Then in my RedHat worked this script:

#!/bin/bash
echo "Arrancando Access Point"
wlanconfig ath0 destroy
ifdown ath0
wlanconfig ath0 create wlandev wifi0 wlanmode ap
ifup ath0
iwconfig ath0 essid breinestorm rate auto

with the original 2 dBi antenna was fine, but also with the 108 Mbps card, the link quality was not very good (20/94) but then I tried searching a little bit with:

iwconfig ath0 channel 9

and suddenly the link quality changed to 50/94 :)
to make use of the 5 dBi antenna I also had to add:

iwconfig ath0 txpower 16

so the script ended up like this:

#!/bin/bash
echo "Arrancando Access Point"
wlanconfig ath0 destroy
ifdown ath0
wlanconfig ath0 create wlandev wifi0 wlanmode ap
#iwpriv ath0 bgscan removed
ifup ath0
iwconfig ath0 essid breinestorm rate auto
#athctrl ath0 -d 20
sleep 10
iwconfig ath0 txpower 16
iwconfig ath0 channel 9

The commented out items could be tried to tune the performance even more in some cases :)

Hope this helps to the people who had the same problems like me with this card.

Comments are more than welcome, I am eager to know who is reading my blog :)