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Networking the Redwoods
linuxwrangler writes "SF Gate is reporting that ecology researchers are outfitting a grove of trees with tiny "micromote" sensors to monitor the light, humidity and other conditions as the trees grow. The sensors, running the open-source Tiny OS, form and maintain their own network. This test of the "Smart Dust" concept (mentioned on /. earlier) only uses 50 sensors but scientists hope to be able to deploy the sensors on a large scale to help figure out why California's Redwoods are dying off at an alarming rate."
Ah yes, forestry by hearsay. Always a recipe for success. :)
I think the concern is more about the rate that mature trees are dying off than the rate replacements are germinating.
Since I'm sure most of /. is more interested in coding a 1 square inch sensor than protecting a 300 foot tree, here's some programming background on the little bastards (which I work with on a daily basis, as part of a sensor network research group in a VA university).
- the architecture
The motes run 4MHz or 8MHz processors, with built in memory. The amount of memory varies across mote models (currently Rene, Rene2, Mica, Mica2, Mica2Dot, and SmartDust) but we're talking 16KB to 128KB of program memory, 4KB to 16KB of data memory, and 4Kb to 8KB EEPROM for permanent storage. They have a short range radio capable of I believe 10kbps, and use an active message model to provide what we know as "ports", so that you can direct a message to a specific handler based on its message type. The packet sizes top out at 36 bytes. The motes are powered by two AA batteries, which can last a surprisingly long time if the radio is put to sleep. Your main means for debugging: 3 LEDs ... you can begin to imagine the headaches I face on a daily basis.
- the bridge
When deployed, most motes are programmed with routing protocols to autonomously establish networks, which are used for data aggregation and getting sensor readings around. The network is rooted at a basestation, a "powerful" PC without the restricted computation, communication and power limitations of a mote. This way any complex processing is offloaded to the PC, and the motes don't waste battery power doing stuff the PC can do instead. So what bridges this mote network to a PC? Well, it's a programming board. You plug a mote directly into the thing, and you hook up a db-25 to your parallel port, and a db-9 to your serial port. The parallel port is used to program the mote's instruction memory, and the serial port is used to receive messages sent by the mote to the PC. The mote that's hooked up to the programming board is loaded with code to translate RF packets to UART, and vice versa.
- sensing
Motes are equipped with 10-bit resolution ADC sensors which can read light and temperature. Other sensor boards can be hooked up to motes to read vibration, acceleration, and a bunch of other stuff. The motes commonly read their sensors, stuff the data in a packet, and send it along to the basestation for processing. That's the generic application model, at least.
- security
The main part of our research deals directly with implementing security in the sensor networks. This is far from easy, since you can't even store a public/private key in the mote's limited memory, let alone do anything with it. The protocols used are complex, involving securely distributing keys, efficient authentication protocols, and all this in 16KB of program memory (on Rene2s) INCLUDING the operating system! Just remember that the point isn't to stop a mote from being compromised, it's to realize it's compromised and drop it from the network. There are supposed to be thousands of motes in the network after all, so dropping a bunch won't hurt.
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Here's hoping that background will help avoid the mass privacy paranoia that we /. readers love so much. At the time of this writing, motes aren't small enough or cheap ($250) enough to produce en masse, nor are they tiny enough to go unnoticed (remember the 2 AA batteries?). Yes, there are exceptions, but 1 square inch are the smallest production versions I know of (Mica2dots). And until they stop running on batteries, their biggest hindrance is their short lifetime, so they currently can't be constantly monitoring anything for months on end.
Aside: Take a look at the Spec. It could change that whole last paragraph. :)
As for the military surveillance stuff, that's what motes are ultimately designed for, to be dropped on
*blinking cursor*