Nanostations, OLSR, and OpenWRT

Well, it has been an interesting period of time since my last post.

Please understand that I have been simultaneously working on the technical aspects of the Ayrstone AyrMesh(TM), updating the web page, writing the business plan, and preparing to show the product at the World Ag Expo in Tulare, CA.

So, first, the technology. While OLSR does definitely work on Ubiquiti's AirOS, the odd fact is that they have somehow messed with MadWiFi so that you cannot create a VAP running in adhoc or ahdemo mode. This, of course, effectively prevents the creation of a mesh network using AirOS.

Ubiquiti must have had some very good reason for doing this, but I have not yet had the temerity to ask them.

I decided at this point to start working with the open-source OpenWRT OS, a Linux distribution originally built for the Linksys WRT54G. It has been ported to the Atheros chipset used by Ubiquiti and runs very well on the NanoStations while providing a lot more control. I started by studing two existing meshing packages: RoBIn and NightWing. From them I was able to figure out how to build a version of OpenWRT that (1) fits in the 4 MB space on the NanoStation and (2) does what we want it to do. So far it's working very, very nicely.

A very nice added bonus is that it works perfectly on the new Ubiquiti Bullet2HP, which is better-suited to our purposes than the NanoStation. I have one of the early units, and it is working very well.

In the meantime, we showed the Ayrstone AyrMesh at the World Ag Expo and were very well-recieved there. People asked what we had and, when we explained, were simultaneously very surprised and very interested. Those who were able to fully understand the capabilities and potential of the concept were eager to try it out, although, in fairness, not everyone really understood it. This is the bane of the high-tech marketer's existance: figuring out how to explain technology so that people understand the full potential of the device - the facsimile machine being a "classic" example.

Meanwhile, we are polishing up the business plan and starting to look for funding. Anyone with a few hundred thousand that you'd like to use to buy into the next high-growth agricultural technology company, please form an orderly line...

More from Radio Boy...

A friend of mine, a few Christmases back, bought me a couple of old serial books, part of the "Radio Boys" series, about a group of boys experimenting with radios (new-fangled, high-tech stuff). They make me smile every time I look over at them - from the 1920s, the language is somewhat odd, but the stories are cute.

I'm trying to find the "perfect" radio system for this product. The perfect radio system will be no-config - just power it up and it will figure out its role. Each node should automatically configure itself as a gateway, repeater, or client (or, even better, repeater-client). I know this is possible, because the Open-Mesh boxes do it. They're just not suitable for outdoor use.

So far, the Ubiquiti radios (I have been testing the NanoStation 2) have won the day - mostly open-source firmware, with a very nice SDK for developing new extensions. The only problem is that the only "meshing" protocol that comes with them is WDS with STP. It actually works pretty well, and will get the job done. However, it requires more setup than I like (not automatic configuration) and doesn't use the "best" encryption algorithm (WEP vs. WPA).

The Open-Mesh boxes run an interesting mix of software, and they can use either B.A.T.M.A.N. or OLSR as the meshing protocol. I recently changed my Open-Mesh boxes from B.A.T.M.A.N. to OLSR and noticed no difference in performance. Running either of these protocols would seem to be a possible solution, but I'd have to change my NanoStations over to OpenWRT, which I am somewhat reluctant to do.

However, I recently found a fellow in Austria who has ported OLSR to Ubiquiti's AirOS as part of a "free wi-fi network" project - see https://wiki.graz.funkfeuer.at/UbntStations.

So I downloaded the SDK, code, patches, and other files from ubnt.com and from funkfeuer.at, and made myself a firmware file for the NanoStation 2 (on about the fifth try - hey, I haven't done real software development for over 15 years!) I loaded it on to one of the Nanos, fired it up, turned it on, and it was running happily.

There are still some small glitches to be worked out before this solution is ready for prime time, so, for now, we'll keep going with WDS. However, the more I read about OLSR the more excited I am about it. The benefits for the Ayrstone customers are great.

Three good months of learning about wi-fi, writing and re-writing business plans, and networking, and I'm approximately where I was when I wrote the last entry.

But I'm learning a lot.

I started out by evaluating Meraki - they have very nice equipment and a system that is really both beautiful and effective. I was able to get a couple of Meraki nodes on Ebay and put them up on my home network. I can't say enough good about them - the system really works well for providing well-isolated internet access across a geographical area. However, my problem is that I want to distribute a LAN, not just internet access, and Meraki's system does not enable access to your LAN. This is a good thing in a "metro" network (you don't want random folks wandering through your LAN) but doesn't fit into my needs.

I then evaluated Open-Mesh, buying two nodes from Open-Mesh.com. I found some basic reliability problems with them, particularly the well-documented problem of the nodes losing connectivity after a brief poser outage. I actually found mine would not connect if the power was off for less than 20 seconds. When I move or reboot a node, I have to remember to unplug it, go do something else, then plug it in again.

I initially decided that they couldn't access my local network because, while they posessed 192.168.1.x addresses (my local NAT) and I could SSH to them at that address, they were providing DHCP addresses in a different net. The Open-Mesh nodes are also very low-power and not suitable for outdoor use. Given those disadvantages, I decided to put them aside.

I took a look at Ubiquiti's radios, particularly the Nanostation 2. It's a terrific radio - sealed, weather-resistant, with an open-source-derived OS called AirOS for which they provide an entire SDK to suppport the creation of third-party software. It also puts out 26 dBm to either an external antenna (now attached with the "standard" SMA-RP connector) or an internal "adaptive polarity" 10 dBi directional patch antenna. One of the standard features is a Wireless Distribution System (or Wireless Domain System, WDS) implementation with an "Auto" feature that can automatically associate with other nearby WDS radios. They also implement Spanning Tree Protocol (STP) to prevent looping in this sort of an ad-hoc network. This provides the same benefits of B.A.T.M.A.N., the protocol used in Open-Mesh, and just distributes the LAN instead of providing "public" hotspots, client isolation, and other features I don't want or need.

It turns out that there are two problems with this approach. First, the "Auto" feature generates a lot of traffic as the number of nodes increased. With three nodes on "Auto" WDS mode, the traffic overwhelmed my little (factory-spec) Linksys WRT54GS. I was afraid of what might happen when I pushed that up to 10 or 20 nodes.

The second problem is that WPA cannot be used in conjunction with WDS. This is a technical limitation of at least their implementation (see here and numerous other places in the Ubiquiti forums) if not WDS and WPA in general.

This brings me to a conundrum: WEP is not very secure (better than nothing, but still...) and the only way to get WDS to work reliably is to set up the partnering manually.

Now, going back to Open-Mesh, it turns out that you can access the LAN, but it does not seem to be reliable in my network. Sometimes it works, sometimes for some nodes, sometimes it doesn't work, for any nodes. However, if I could get the B.A.T.M.A.N. - RoBIn combo working the way I want, I could load OpenWRT onto the NanoStations and try building a NanoStation OpenMesh node. In fact, I might even try just running B.A.T.M.A.N. and see if I could build what I want without the other parts.

That's where the ag mesh network is as we swing into the Thanksgiving holiday.

More to come...