On Mar 11, 2010, at 6:53 PM, MCH wrote: > So if there are two TRBO repeaters in the same area, there is no way to > keep them both from being active and interfering with each other? That > doesn't sound right.
They're on different frequencies. Not sure what you're saying here. > Or, if I have a repeater, anyone can just buy TRBO radios and use it? The "color codes" are like CTCSS or DCS, someone wants to use your repeater they have to know your frequency, and what "color codes" are active on the repeater, I assume. Those I'm sure are programmed into the repeater, but the data stream with the user ID's and talk group numbers, the repeater probably doesn't care about... it's just data passing by. It all depends on if they demodulate the digital signal at the repeater and then remodulate, whether or not they can "do stuff" with that information at the repeater site. They probably do, but they probably also rely on off-board applications via some standardized connector, protocol (likely serial), and an application programming interface to "do that stuff" at the repeater site. It would be shortsighted to put too much "brains" into the repeater box's controller itself.... modular is good, in this case. As far as how to really "secure" a radio network... first off, nothing's 100% "secure".. but one implementation is like cell phone networks that have always had serialized radios that transmit their factory-burnt-in serial numbers, but very few 2-way systems have ever had that feature. I doubt TRBO does either. That would be the only way to keep a radio from talking on your repeater. (Think IMEI numbers on cell phones.) Another way is loading an encryption key into each rig that has access to a certain system, and using decryption on each stream to look and see that a particular rig is transmitting a specific key prior to repeating, whenever the radio keys up. That's a bit much, but could be done in any digital radio system. I hear that there's been talk of radio serialization in P25, somehow tied to the encryption functionality. If not that, there's supposedly already some proprietary systems that you can load an encryption key into a fleet of rigs, and those radios can then be remotely shut off or even fully wiped by the radio system manager... if someone steals one and want's to play with it. Stuff like that. But does TRBO have these features? I kinda doubt it. But again, I don't own any of these things... this stuff's just REALLY obvious to anyone who's worked in wireline data for 20 years. The two-way world is finally catching up to the rest of the world now that the on-air protocols are digital... the same progression is happening that happened to LAN technology that eventually became "The Internet"... 1. Get data flowing, build some protocols for transporting it. 2. Mess around with all the transport mechanisms for a few years until someone comes up with an elegant transport layer mechanism that everyone agrees is robust enough and simple enough to transport "whatever". (TCP/IP... which is a misnomer, since UDP/IP is used just as heavily these days... but doesn't get its name up in lights.) While doing this, figure out a global routing scheme. 3. Realize dumb/malicious people will dork around with the transport if you let them. Employ encryption on the embedded data. 4. Realize again that dumb/malicious people will dork around with the unencrypted headers. Come out with a way to encrypt the whole thing that's so complex, no one's interested. Two-way digital radio is right in the middle of step two, historically speaking. Which digital on-air protocol is going to be the historical version of "IP" (a good protocol suite, annoyingly simple, and works well but has warts, and will survive seemingly "forever"), and which one is "IPX" (going to die but was probably implemented better for the short-term, but has limitations that mean it can't be used long-term), and which one is Banyan Vines (going to die REAL fast because it's too specialized but works well)... remains to be seen. :-) Same thing's going on in my line of work. ALL... and I mean ALL of the mistakes the audio-conferencing folks made in the 90's and then fixed, are being made again by the video-conferencing people, and fixed again. "There's nothing new under the Sun." There could probably be a book written about this same technology cycle over and over again... or maybe there already has been... Early adopters are bright folks who get some TECH thing and it does little. They have to make it do something interesting or useful from scratch... Middle adopters come along, and the bright folks decide they're tired of answering questions so they make it "easier" by building systems from that tech that do useful things and take away some of the choices... Late adopters come along and by then, the middle adopters have formed "fan" camps and "know" that "this is the best way to use this tech... this brand, these features... buy this..." Late adopters push for even "easier" solutions to problems that really didn't need one.. (think push-button car starting here... so easy now people can't figure out how to turn their cars OFF... was the keyswitch really all that "broken" a technology?)... Right now, digital two-way radio is at the middle adopter stage. Maybe not in Amateur Radio (we're way late to the party) but the camps are forming... D-STAR, TRBO, P25, TETRA, insert next whiz-bang digital radio tech here... Those that study the underlying tech, even if middle adopters, are at an advantage -- they know a data stream, is a data stream... how you form the headers, interlace the data, and all that... is just an IMPLEMENTATION... pick the one that meets your needs. Cellular is more advanced in this regard. Definitely well into Late Adoption. We're now building phones with two buttons (one for "parents" one for "police" for little kids. A) Does a little kid actually need a cellular phone, and B) If they can't dial a phone number yet, is it a bit too soon to be putting that kind of tech in their pockets? :-) You see where I'm going here. It'd make a fascinating book if you could pair up with a behavioral economist to explain the "why's" of why folks even buy this stuff to begin with... Nate WY0X
