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DARPA Looks To Adaptive Battlefield Wireless Nets
An anonymous reader passed us a NetworkWorld link about an effort at DARPA to succeed in combat through networking. The idea is to keep soldiers in a position of informational superiority through a tactical radio network that would 'link' everyone together on the battlefield. "Project WAND, for Wireless Adaptive Network Development, will exploit commercial radio components, rather than custom ones, and use a variety of software techniques and algorithms, many of them only just now emerging in mature form. These $500 walkie-talkie-size radios will form large-scale, peer-to-peer ad hoc nets, which can shift frequencies, sidestep interference, and handle a range of events that today completely disrupt wireless communications ... [right now] 'The average soldier on the ground doesn't have a radio,' says Jason Redi, principle scientist for BBN's network technologies group, and the man overseeing the software work. Radios are reserved for platoon and company commanders, in part because of their cost: typically $15,000 to $20,000 each, with vehicle-mounted radios reaching $80,000."
we pay $4000 for a repeater and $1000 for a radio.
there's no fucking way those radio's in their jeeps are worth $80,000. even for the latest wizz bang model with built in encryption chips, at most i'd expect $40,000 for the repeater and $10,000 for the radio. and even then i'd be blown away at how much of a rip they are.
If you mod me down, I will become more powerful than you can imagine....
That's why many modern tactical radio systems use frequency-hopping or direct-sequence spread spectrum techniques to make it difficult to jam or DF (direction finding) the radios on the net. Even with older FM radios, keeping power to a minimum and using proper radio discipline can reduce the risk to friendly forces. The signal from a direct-sequence spread spectrum transmitter can be below the noise floor when viewed on a spectrum analyzer.
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> It'll make communications a lot easier if we can use our handhelds, and have it eventually retransmitted to our dispatch center rather than having to run back to the truck to ask for an air ambulance or whatever.
That technology already exists. It is called an HT, Project 25, and a repeater. Most public safety agencies have HTs and repeaters. Many of them are converting to or using Project 25 at this time.
-Valen
A large portion of that cost is making the radio conform to military specifications for ruggedness, reliability, extreme environmental conditions, etc. It has to work in all possible conditions and also be "soldier proof". You wouldn't believe the amount of abuse that they are subjected to. The manufacturer is making a reasonable profit, it's very expensive to design, build, and support mil-spec hardware. It's not the sort of business to go into if you want to get rich quick.
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Have you priced mil-spec parts? They are damned expensive due to low production volumes, inspection, testing, and documentation. They also have to meet tougher specs than commercial grade parts. I haven't seen any commercial radios that would meet all of the mil-spec requirements. It would cost too much money to design and build them to that standard. That said, the military has bought a lot of commercial grade radio equipment (VHF/UHF HTs for example), on the theory that they are good enough for most situations and they are cheap enough to buy in large quantities and issue to the average soldier.
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These factors leads to a distinctly different design then a commercial unit. A poster argued that commercial radios with similar capabilities cost a fraction of the price; i bet those same commercial radios are not in fact milspec rated, and thus are not as reliable as this kit.
Of course, the discussion could be wether to buy the gold-plated milspec stuff or about 10 commercial units. No offense, but if i was a footslogger, I would take the (heavier) milspec kit; I can only carry so many commercial units to switch out when they fail, but the milspec one will work in almost any condition.
Frequency Hopping Spread Spectrum is the technology the GP was referring to rather than the broader term "encryption". While FHSS can and usually is considered a form of encription not all flowers are roses.
The benifit to FHSS is that both endpoints know the frequency list so they know which frequencies and what order they should be hopping through therefore it is seamless as long as both endpoints remain in synch.
There are two ways that devices synch up their frequency list. One is physical connection (e.g. a 900MHz FHSS cordless phone placed in the cradle will re-synchronise the "channel" list and, if additional encription is implemented, their encryption key). The second method is during the handshake, or initial connection period of the radio link, on a pre-defined static frequency the frequency list is transmitted, then subsequent transmissions are carried out on the specified frequencies. In this case an encryption key is usually used to prevent eavesdroppers from being able to collect and use this frequency list. A new frequency list can be transmitted after the initial connection is made and perodically updated to increase the security or reliability of the link if needed.
Now this appears to be background noise as only very small snippets of the conversation, often times digital and/or encrypted to futher obfuscate the transmission, will be transmitted on any given frequency. This means that the pieces that can be received on any given frequency are tiny spikes in the transmission which are clicks or pops and would not be discernable from the "noise".
FHSS has been in use for many, many years by everyone from civilians to ultra top secret government orginizations to both hide or "encrypt" the communications and to reduce the interferance of similar devices operating on the same frequency bands.
Hope that is helpful.
See my previous comment regarding FHSS. By using both a long, complex frequency list and an algorythm that decreases transmission power to just above the point where data begins to be lost (think auto-focusing a camera lens) it would be conceivable that they could evade detection very easily.
I am a H.A.M radio operator and know how "foxhunts" go. Imagine you have this "foxhunting" gear and are trying to locate enemy soldiers/vehicles using this technology. How would you determine what frequency to tune your directional reciever to? You would scan for strong signals that present a clear modulated signal that the equipment you are using can "tune-in" to. This will not work with FHSS. As your receiver scans through it will get pops and clicks that is is DESIGNED to ignore. It sees no modulated signals so it moves on. Even if you connect the receiver to an osilliscope and snoop around the radio waves for anomolous waveforms you won't be able to see them with your superior pattern recognition abilities of your human brain (the human brain is amazing at pattern recognition) because it will look like pops and clicks in the noise that are normal in background noise.
The only way to get a lock on the signal is to know the frequency list, and calibrate a FHSS receiver to the list and lock onto the scattered modulated signal. Then using a phase shift, yagi, parabolic reflector or other directional antenna you can trace the signal to its source (providing the signal is not too chaotic to interfere with the method of direction finding you are using, traditional signal strength based triangulation is probably your best bet).
Hope that clears a few things up.
I've been researching self-managing networks, which like adaptive networks are a subset of a new field of research known as cognitive networks. The majority of research in this field was started by J. Mitola of Motorola Labs study of cognitive radio, which is basically synonymous with adaptive radio. The term "cognitive network" was coined only last year, but both IEEE and ACM have a handful of articles on this topic if you want to learn more. I truly believe this (autonomy) is where all networks are headed.