Wireless mesh networks are self organising and self healing networks that can be used to connect computers across small and large areas, depending on the radio technology used. Normal wifi equipment can be used to create home made radio networks, and there are several successful examples like Freifunk and Athens Wireless Metropolitan Network (see wikipedia for a large list) around the globe. To give you an idea how it work, check out the nice overview of the Kiel Freifunk community which can be seen from their dynamically updated node graph and map, where one can see how the mesh nodes automatically handle routing and recover from nodes disappearing. There is also a small community mesh network group in Oslo, Norway, and that is the main topic of this blog post.
I've wanted to check out mesh networks for a while now, and hoped to do it as part of my involvement with the NUUG member organisation community, and my recent involvement in the Freedombox project finally lead me to give mesh networks some priority, as I suspect a Freedombox should use mesh networks to connect neighbours and family when possible, given that most communication between people are between those nearby (as shown for example by research on Facebook communication patterns). It also allow people to communicate without any central hub to tap into for those that want to listen in on the private communication of citizens, which have become more and more important over the years.
So far I have only been able to find one group of people in Oslo working on community mesh networks, over at the hack space Hackeriet at Husmania. They seem to have started with some Freifunk based effort using OLSR, called the Oslo Freifunk project, but that effort is now dead and the people behind it have moved on to a batman-adv based system called meshfx. Unfortunately the wiki site for the Oslo Freifunk project is no longer possible to update to reflect this fact, so the old project page can't be updated to point to the new project. A while back, the people at Hackeriet invited people from the Freifunk community to Oslo to talk about mesh networks. I came across this video where Hans Jørgen Lysglimt interview the speakers about this talk (from youtube):
I mentioned OLSR and batman-adv, which are mesh routing protocols. There are heaps of different protocols, and I am still struggling to figure out which one would be "best" for some definitions of best, but given that the community mesh group in Oslo is so small, I believe it is best to hook up with the existing one instead of trying to create a completely different setup, and thus I have decided to focus on batman-adv for now. It sure help me to know that the very cool Serval project in Australia is using batman-adv as their meshing technology when it create a self organizing and self healing telephony system for disaster areas and less industrialized communities. Check out this cool video presenting that project (from youtube):
According to the wikipedia page on Wireless mesh network there are around 70 competing schemes for routing packets across mesh networks, and OLSR, B.A.T.M.A.N. and B.A.T.M.A.N. advanced are protocols used by several free software based community mesh networks.
The batman-adv protocol is a bit special, as it provide layer 2 (as in ethernet ) routing, allowing ipv4 and ipv6 to work on the same network. One way to think about it is that it provide a mesh based vlan you can bridge to or handle like any other vlan connected to your computer. The required drivers are already in the Linux kernel at least since Debian Wheezy, and it is fairly easy to set up. A good introduction is available from the Open Mesh project. These are the key settings needed to join the Oslo meshfx network:
|Protocol / kernel module||batman-adv|
|ESSID||meshfx@hackeriet||Channel / Frequency||11 / 2462||Cell ID||02:BA:00:00:00:01|
The reason for setting ad-hoc wifi Cell ID is to work around bugs in firmware used in wifi card and wifi drivers. (See a nice post from VillageTelco about "Information about cell-id splitting, stuck beacons, and failed IBSS merges! for details.) When these settings are activated and you have some other mesh node nearby, your computer will be connected to the mesh network and can communicate with any mesh node that is connected to any of the nodes in your network of nodes. :)
My initial plan was to reuse my old Linksys WRT54GL as a mesh node, but that seem to be very hard, as I have not been able to locate a firmware supporting batman-adv. If anyone know how to use that old wifi access point with batman-adv these days, please let me know.
While investigating mesh networks in Oslo, I came across an old research paper from the university of Stavanger and Telenor Research and Innovation called The reliability of wireless backhaul mesh networks and elsewhere learned that Telenor have been experimenting with mesh networks at Grünerløkka in Oslo. So mesh networks are also interesting for commercial companies, even though Telenor discovered that it was hard to figure out a good business plan for mesh networking and as far as I know have closed down the experiment. Perhaps Telenor or others would be interested in a cooperation?
Update 2013-10-12: I was just told by the Serval project developers that they no longer use batman-adv (but are compatible with it), but their own crypto based mesh system.