Introduction: Mobile Emergency Communications: Mobile Repeater and Mesh Node.
What happens when the grid breaks? Communications need to be restored.
After Hurricane Katrina hit, BellSouth announced that it would take 3 months to restore phone lines. Volunteers using WiFi gear were able to connect churches and community centers within the first weeks and within three days of setting up an asterisk call server, routed 10,000 phone calls. Reliable backup infrastructure can be brought up in hours or minutes if you are prepared and have a plan in place.
Here is a plan for a mobile mesh repeater node to be used while you are setting up permanent installations, doing site surveys or for completely mobile teams.
Step 1: Make Sure You Have Everything.
Spool of Cat5e: I always use red to announce that there is power running through it.
Crimpers and Connectors: Even though it's wireless, you always need to use *some* wire.
Backpack or messenger bag: The orange bag pictured is a waterproof backpack/messenger that I got as a promotional item, Any durable, rubberized bag will do the job.
Power Source: I use a sealed lead acid Hawker Genesis 12V 16Ah. You can use any 12V battery, but it's important to pick something up with long life and low weight. Having an easy to find charging system is also a good idea.
Mesh Node: We are using the Metrix Mark II Kit here. Running Pyramid Linux, it can act as an access point, a client, a mesh node, and more. Being waterproof is also a nice touch.
Antennas: Whips are nice, but they don't go very far, For this setup, we've got an outdoor 8dbi omni and a small 10dbi patch antenna. This allows us to set up a directional link to our upstream node while serving clients locally. Picking your antennas really depends on how far you're going to advance and what you can carry. If you're using this as temporary infrastructure while setting up permanent installations or using it as site survey equipment, I recommend matching them with your standard kit. If you are only doing temporary sites, the above combination is pretty flexible. Both of these antennas were picked up at HyperLink
Step 2: The Wire
Because the Metrix Kit is powered over ethernet, this is amazingly simple.
Get a length of Cat5e (I usually use about two feet) and use a Cat5 stripping tool or sharp knife to cut the jacket right around the halfway mark. Slide the jacket off and cut it in thirds. Separate the orange and green pair from the blue and brown pair and slide the jacket pieces back on to make the cable tidy. Crimp connectors to the base of the Y as well as the orange and green side following this chart.
base of Y
orange/white | orange | green/white | blue | blue/white | green | brown/white |brown
orange/white | orange | green/white | empty | empty | green | empty | empty
On the brown/blue pairs, strip the individual jackets to expose the copper and twist together. You will be wrapping these around your battery posts.
Step 3: Make Sure It Powers Up.
Plug everything in before you screw the lid on. BLUE goes to RED on the battery, BROWN goes to BLACK.
Make sure the LEDs light up. If they don't, doublecheck your connections.
You may also want to configure your kit at this point.
Step 4: Plug Everything in and Put It in the Bag
You're pretty much done at this point. Toss a wifi phone in for testing and you're all set!
We have a be nice policy.
Please be positive and constructive.