The MESH, HSMM, Broadband-Hamnet (BBHN), what ever you want to call it, I find it to be an exiting new addition to ham radio. I have been a fan of the mesh network since I stumbled across it a little over a year ago. For those of you who are maybe new to Mesh Networking, the basics of the network is to take an old Linksys WRT54G series router, flash the router with the new Broadband-HamNet firmware, and for the most part, it is a functioning node. The nice thing about the MESH network is that it is self discovering, and self healing. What this means is that when you put your system on the air, if there is a node close to you that you can connect to, it will connect by itself. Maybe a node goes offline for some reason, the mesh will reconfigure the routing so that the network can still pass information around the now missing node.
There are a few things you need to do to set up your node. You need to enter your call sign for the node, if your node is connected to the internet, either locally or through the mesh, you can start adding some functionality to your node by downloading services like an IRC(Internet Relay Chat) server or a PBX system to make ham to ham phone calls. Even without adding the additional functionality to the node, you are still extending the range of the network. The mesh needs multiple nodes to create a reliable network, so the more that join the mesh, the better.
The idea of creating a stand alone wireless network free of any other networking infrastructure has great potential. With some of the new components like the Ubiquity gear, and Raspberry pi coming into play, the options of what this simple stand alone network can de are almost limitless. Where it once was a necessity to purchase an obsolete router on the used market, now you can buy brand new Ubiquity gear and have the network up and running on 900Mhz, 2.4Ghz, 3Ghz, and 5Ghz. This creates more options to create links where they may not have been possible, or at least difficult on the 2.4GHz band.
I see the benefit from an emergency perspective, but I'm not that guy. yes I have the minimal set up to keep me up and running if there is some type of natural disaster, but if I never hear the phrase "zombie apocalypse" again, it won't hurt my feelings. There are definitely situations where having your own Intranet for file transfers could be beneficial. Maps of disaster areas, photos or live video streams of an event, the possibilities are endless, and if you can send a type of file over the internet, you can send it over the MESH. If a situation were to arise, no matter what my intent was, emergency, casual file transfer to a ham friend a few miles away, using it as a remote access to my station... when I put up my node, it is on line ready to pass what ever traffic come to it seamlessly.
Why mesh networking? I love the challenge of working with the high bands. At 2.4Ghz and 1/4 watt output, it doesn't take much to block the signal. If you have ever worked the 1296 band and thought that was a tough contact, 2.4Ghz is a lot like 1.2Ghz but more of a challenge. Taking one of these units, setting it up, and linking to another node is kind of like calling CQ for the first time and having someone answer you, it is exciting watching the network grow node by node. Setting up your first node takes a little effort. You don't need to have a strong networking background, but it does help.
Testing! The testing phase is the part that I enjoy the most. It takes some time and patients to be able to get things set up correctly. sometimes it takes trying different set-ups to figure out what is going to work for you. Two of the most common set-ups are to use a 24Dbi dish antenna if you need to cross a long distance to connect to another node. If you have a node closer to you, you may be able to get away with a high gain vertical omni. With the WRT54G series, there are actually 2 antenna connectors so you can set up one with a dish for the long distance link, and the vertical to extend the range of your node by a few blocks or more. If you have at least 2 nodes and a laptop computer, it is pretty simple to set up one node in what you think is a good direction, go for a drive with the laptop connected to your second node, and every block or so(depending on environment) just pull over and scan for nodes to see if you can still pick up your node. If you cant pick it up, go back, adjust where you can and try again. Remember at 2.4Ghz, the signal is line of sight and even the slightest obstruction will cause issues.
Aside from antennas, as hams, we can also run amplifiers to help the signal out. Before we go too deep into this area, you need to make sure that an amplifier is truly needed. If you have a 24Dbi dish pointed at another 24Dbi dish 5 miles across town and you are not linking, the amplifier is probably not going to help, remember, it is line of sight, either the antennas can see each other, or they can't. If you have a link but it is poor quality, a small amplifier may be something to look into adding. When adding an amplifier, remember that this will raise the noise floor of the wifi around you so you only want to add an amplifier if it is truly needed. There are different types of amplifiers out there, so you need to be sure you choose carefully. You will want to use a Bidirectional amplifier to ensure that your RX is as good as your TX. Also, 1 watt into a 24Dbi antenna has an ERP of 150 watts, so no need to go overboard here.
Once you have converted your device to a BBHN node, you will not be able to connect to it with your computer over wifi, you will have to use a hard cable connection to access your network. If you really want to connect to it wireless, you could always put a standard wifi router coming out of your mesh node and connect to the node that way, so don't waist a lot of time trying to login with wifi.
I have not used any of the Ubiquity gear, but I do know some of the basics of it. With the Linksys unit, you have to put the unit in a waterproof box and mount it up on your tower, pole, mast, or whatever you are using to mount your antenna (to keep it within a few feet of the antenna to keep the coax run short). You need to run 110 AC up to the wall wart, or run a Power Over Ethernet(POE) adapter. The issue with long runs of cable on a 5 volt or 12 volt node, it may not function properly because of the voltage drop, the nice thing about the ubiquity gear, is it is designed for this type of installation. After flashing the Ubiquity gear with the BBHN firmware, you just have to mount the antenna, plug in your Ethernet cable and your done. The Ubiquity gear does make things a bit easier to set up.
You have some options with the Raspberry pi also if you want to get a little more in depth with the system. If you are unfamiliar with the raspberry pi, it is a $35 credit card sized computer running a Linux based operating system and an ARM processor. The Raspberry pi has GPIO pins on the board so if you have a little Python experience, you can write our own programs to run external devices controlled by the Raspberry pi. This is Where it starts getting real fun when you realize you could control almost anything you want through this system.
This isn't meant to be an in depth lesson on all things MESH, and there is definitely a lot of info out there, so if you are interested in Broadband-hamnet, check out http://www.broadband-hamnet.org/ and dig out that old router and join the mesh.