Metrocrest Amateur Radio Society
AREDN
Updated March 3, 2017
More about AREDN
by Kevin Grantham, N5KRG
At the January 12, 2017, meeting, Paul Newman, KA5TYW, and Dale Finley, KB5NFT, talked about AREDN™, or Amateur Radio Emergency Digital Network. Dale also presented some of the technologies and his implementation. Dale is certainly the most experienced AREDN experimenter in the club, and he has created a “War Wagon” out of his Honda Element to drive around looking for AREDN nodes. (See the Archives for photos of some of his gear.)
Briefly, AREDN is a WiFi data radio organized into a “mesh” configuration, and able to operate on frequencies reserved for amateur radio. One of these bands is just below the standard WiFi 2.4GHz band, and that’s the most popular for experimenting.
Conceptually, meshed AREDN nodes create a wide-area local area network (LAN), where every node can pass traffic to every other node. The idea is that each node can mesh with at least two or more other nodes. If a node goes out of service, the traffic can automatically reroute through other nodes and still get to its destination.
Individual nodes can also be connected to the internet or other networks through their “gateway” functionality, although this isn’t required. If there is at least one node connected to the internet on the mesh, any device can get to the internet through the mesh to the gateway. If there’s more than one, mesh routing automatically finds the “closest” one, the one with fewest hops.
Individual nodes don’t have to be connected to anything. They can function as relay nodes, meshing with other nearby nodes and repeating traffic to and from the mesh.
Unlike “regular” WiFi, you don’t connect directly to an AREDN node using your smartphone or WiFi-equipped computer. That’s because the WiFi radio part of the node is used to connect—or mesh—with other AREDN nodes. You connect using the wired port on the AREDN node.
Local devices such as IP telephones (“voice over IP” or VoIP), IP cameras, computers, servers and just about anything that has an IP connection, can all connect to a node.
What makes all of this possible is work done on the old Linksys WRT54G routers. Experimenters found that some versions (versions 1, 2, 3, and 4, and both versions of the WRT54GS and the newer and still-manufactured WRT54GL) were running open source Linux. Once you have installed the necessary firmware, you can add other applications such as print servers, storage for network access and backup, and more. There are hundreds of applications that run on these and similar devices from other manufacturers.
Hams created an application group called Broadband High Speed Multimedia Mesh, or Broadband-HSMM (later changing the name to Broadband-Hamnet™, or BBHN). They took commercial mesh software and ported it to the WRT54G routers. This was very successful, and that group is still in operation.
However, those devices are very limited in memory, and quite slow. A group moved away from BBHN and ported everything to the excellent Ubiquiti® airMAX® devices. They are inexpensive, powerful, and require no hardware modifications to operate in the 2.4GHz amateur band. TP-Link also has a unit that has been tested and certified. This group became known as AREDN, for Amateur Radio Emergency Data Network.
There is nothing “emergency” about it, although it is definitely Amateur Radio. The software allows the devices to operate at higher power than the Part 15 consumer limits, and allows them to operate in the ham-only part of the band. The WRT54G devices used by BBHN cannot operate at those frequencies without major surgery, so the BBHN guys are also moving to Ubiquiti devices. Problem is, folks purchased lots of WRT54G devices to play with mesh and being the cheap hams that we are, don’t want to throw them away.
Really? Most paid $5 or $10 for their WRT54Gs at the Goodwill, Salvation Army, or a yard sale. We’re not talking about throwing away a Yaesu FT-5000 here! But I digress.
The ham-only portions of the band are very desirable because there’s no one there but us, so the noise floor is very low, and distance between nodes can be greater.
The Ubiquiti stuff is inexpensive as well. The airRouter® is an indoor-only device that comes with a gateway port for connecting to the internet if desired, a port to cable to another node or network directly such as an outdoor node, and three ports for connecting computers, cameras, printers and so forth. The airRouter is about $32 from Amazon Prime. They go up in price depending on what model and antenna combinations one choose. The PicoStation®HP (high power) is a small unit that comes with an 8dbi omnidirectional antenna and a power unit for about $80. Just add Category 5 or 5E shielded data cable and it’s ready to deploy. It’s weatherproof and can go inside or outside.
So what’s been going on with AREDN and MARS? Basically, no one can hear any other hams. Mesh works when there is something to mesh with.
The guys at AREDN have developed “virtual tunnel” (VTUN) software that runs in the nodes. A node can be set up as a “client” where it connects to another node via the internet, or it can be set up as a “server” to accept connections from client nodes over the internet. Using tunnel software, each of these “mesh islands” can mesh over the internet. This is better than nothing but sort of defeats the purpose of setting up an internet-independent network that can function even when the internet goes down.
I have been asked by the Dallas Amateur Radio Society to approach Dallas Medical Center about putting AREDN nodes on their roof. Since I live close by that would give me and possibly other hams in the area (northwest Dallas and Farmers Branch) at least one node with which to connect.
I’m also working on a proof of concept for the Dallas County Medical Reserve Corp that would use 3.4G point-to-point AREDN connections to various sites throughout the County which would also have 2.4G AREDN collectors to support portable Point of Dispensing (POD) sites. This would provide an internet-independent network to support WebEOC® and possibly phone and fax connectivity to the Public Health Operations Center in an emergency.
How can you help? Get involved. Get an AREDN node—maybe a PicoStation®HP to start. Put it up high, above your roofline, and see if you can mesh with another ham. The more hams we have participating, the better and more resilient the mesh network.
If you want more information, please contact Kevin Grantham N5KRG at n5krg@arrl.net. You may also visit: