The goal of this project was to understand a bit more about how wifi repeaters work. There are some great tutorials of how to build a router using a raspi but I struggled to find a functional repeater or range extender using a raspberry pi zero. This would be handy and (in principle) quite affordable to since the rapi zero is just $5 and a cheap usb wifi card is about £10. The idea is that you need two wifi antennae (the built in one and the usb one). One wifi acts as the receiver and another the transmitter.
The raspi has an onboard wifi antenna and it is apparently very good with antennae placed in an etched resonant cavity to amplify signal. You will need to buy an extra usb wifi card and I bought this. The chipset for this card is Realtek which tends to have linux compatible drivers but worth checking the amazon reviews/questions first. Addition, tested with Alfa AWUS036NEH and worked out of the box (Ralink RT3070 chipset and actually v quick too). Tested the Alfa AWUS036NH and it didn't work out of the box and I was too lazy to download the drivers (although the amazon Q/A did say the chipset is Ralink RT3070 which meant it should have worked)...
You could also consider using this as a portable Raspi VPS! Please let me know if you do this since it might be a useful project.
I made a disk image and all you need to do is clone this repo.
git clone https://github.com/tmopencell/wifirepeater.git
cd wifirepeater
unzip raspizero_wifirepeater.dmg.zip
Type diskutil list and note the names of the drives in the form /dev/disk**X**. Then write down the size of the SD card you will be using. Insert the SD card into your reader on your laptop. Now type diskutil list and look for the drive that was not there previously, for example: /dev/disk3. Look at the file size, does it roughly match the size that you recorded previously? If so you are good to proceed. Copy the drive number.
NOTE: this may seem a bit overkill but you want to make sure you are sure you are overwriting the right drive.
Now unmount the drive by typing:
diskutil unmountDisk /dev/disk**X** where X is the drive number you recorder previously.
Now type sudo dd if=rasppizero_wifirepeater.dmg of=/dev/disk**X** bs=1m (insert the drive number for X). This will take a bit of time, maybe 10-15 mins and there will be nothing displayed meanwhile. At the end of the process you will see something like this:
dd: /dev/disk3: Resource busy
4087880+0 records in
4087880+0 records out
2092994560 bytes transferred in 1332.643448 secs (1570559 bytes/sec)
This is good, you were successful! Now pop the SD card into your raspi and insert a usb wifi adaptor.
The system can be accessed normally by logging in with a screen and entering your password etc.
However, you can also use headless login. The system is set up to launch a wifi network right away! SSID: Pi-Extender with passcode: raspberry. It also has fixed IP addresses the Pi-Extender network is 192.168.220.1 and for the network you attempt to connect to it is 192.168.0.2 (NOTE you may need to edit this depending on your network).
To login connect to the Pi-Extender network. Once connected type: ssh pi@192.168.220.1 and enter the username+password:
username: pi
password: raspberry
Then you will need to set up your wifi credentials for your current network.
Type sudo nano /etc/wpa_supplicant/wpa_supplicant.conf and you will see:
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=GB
network={
ssid=""
psk=""
}
Put your details into the quotation marks, it should look like this:
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=GB
network={
ssid="yourwifiname"
psk="yourwifipassword"
}
To check if oyu are connected type sudo ifconfig
You should see something like this:
~ sudo ifconfig
lo: flags=7XX<UP,LOOPBACK,RUNNING> mtu XXXXX
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 2079 bytes 195277 (190.7 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 2079 bytes 195277 (190.7 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wlan0: flags=XXXX<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.220.1 netmask 255.255.255.0 broadcast 192.168.220.255
inet6 XXXX::XXXX:XXXX:XXXX:XXXX prefixlen 64 scopeid 0x20<link>
ether XX:XX:XX:XX:XX:XX txqueuelen 1000 (Ethernet)
RX packets 1033126 bytes 1447522803 (1.3 GiB)
RX errors 0 dropped 3 overruns 0 frame 0
TX packets 592482 bytes 75293703 (71.8 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wlan1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.2 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 XXXX::XXXX:XXXX:XXXX:XXXX prefixlen 64 scopeid 0x20<link>
ether XX:XX:XX:XX:XX:XX txqueuelen 1000 (Ethernet)
RX packets 614913 bytes 63994832 (61.0 MiB)
RX errors 0 dropped 9 overruns 0 frame 0
TX packets 1028656 bytes 1481624145 (1.3 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
If you type ping google.com and you should see something like this:
ping google.com
PING google.com (XXX.XX.XX.XX) 56(84) bytes of data.
64 bytes from XX-in-YY.net (XXX.XX.XXX.XX): icmp_seq=1 ttl=52 time=30.4 ms
^X64 bytes from XX-in-YY.net (XXX.XX.XXX.XX): icmp_seq=5 ttl=52 time=268 ms
--- google.com ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4008ms
rtt min/avg/max/mdev = 9.316/65.574/268.818/101.945 ms
hold the ctrl and c buttons to exit this.
If you are not connected then restart the dnsmasqing and networking (NOTE: this will kick you out of the system and you will need to login again). Type:
sudo service dnsmasq restart
sudo service networking restart
Reconnect to the wifi network Pi-Extender and check if you are connected to the net!
You may want to edit the IP address(es) and if you choose to then type:
sudo nano /etc/network/interfaces
I am not an expert so please don't take my word for this. The default login is:
username: pi
password: raspberry
Please change the password by typing sudo raspi-config and select change user password
I also like to use an ssh key for login and to disable password login altogether. You can read about how to do this here.
This was a first attempt and the performance was.. Terrible.. The summary outputs of ping google.com when I am connected to my main network and when I am then connected to the extender network. I also did an internet speed test and the results were about an order of magnitude drop in speed (100 mb/sec vs 10 mb/sec).
Output from main normal network:
--- google.com ping statistics ---
29 packets transmitted, 29 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 8.403/15.406/97.911/20.073 ms
Output from my Raspi when connected to main network:
--- google.com ping statistics ---
33 packets transmitted, 33 received, 0% packet loss, time 32047ms
rtt min/avg/max/mdev = 8.641/13.662/104.204/16.463 ms
Output from my computer when connnected Pi-Extender Network:
--- google.com ping statistics ---
47 packets transmitted, 47 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 10.286/25.701/161.280/27.542 ms
You can see the roundtrip is doubled and actually important to note the differences between the max and min speeds and the stddev (standard deviation, the variation in times), it is the source of the flakiness. Sommetimes loads lightning quick and other times takes ages.
NOTE: Please help! The physical distance from London to Mountain View, California (where 216.58.213.1 supposedly lives) is 8,631 km or (8.6 x 10^6 m). If it takes 8 ms (or 8x 10^-3 s) to get there and the speed of light is fixed (at 2 x 10^8 m/s in optical fibres) then we have got a little issue of a breach of the laws of physics.. The shortest possible time to travel that distance is roughly 43ms (double assuming reply)... hmmm. Maybe someone can help me out here? Even assuming the computer/server adds no delay to the system if one of the pings takes only 8ms then the location is within 1600 km. Since the server is probably not in the ocean (probably..) then it is either in Ireland somewhere or somewhere in continental europe as far east as about Poland or as south to Spain.
I suspect much of the issues are coming from the DNS side. If the unit was set up more as an access point (i.e., not issuing IP address leases) then it would be quicker, the DNSMASQ that I use is probably not the best and I don't know enough to optimise it. This would be my recommended first port of call.
I don't think the wifi cards are the problem. I have used the Raspi as a wifi router previously and while it does throttle the speed (usually about 30/40 mb/sec) it is still quick. This is true for the external antenna as well. Thus I think the issue is more in the computational task (the witchcraft of which I do not claim to understand) of issuing/managing IP addresses rather than just hardware limitations.
Happy repeating!
ASIDE
If you have are contributing and get this error after pusshing changes:
ERROR: Authentication error: Authentication required: You must have push access to verify locks
Then the following witchcraft might help:
git lfs update
Also utter this phrase three times: "praise be to the gitlord" while wishing really hard for it to work.