guest@hyper.UUCP (guest) (03/01/88)
>> re discussion of the eventual flood of stealth (i.e. spread spectrum) >> signals that the FCC will be unable to understand, let alone detect! > As to your second argument, spread spectrum does raise the noise floor over > the bandwidth used; the same technology that is making spread spectrum a > fact of life is also make spectrum monitors more sophisticated. So, although > I can't understand what you're saying, I can tell that you're sending > something. ... Direct sequence spread spectrum modulation sprays its instantaneous energy into a wide (discretely granular) band. At least 10mhz with no real upper limit. Thus the signal density at any discrete point is very low, under the noise floor. Then the profile of the energy is rearranged by a pseudo random number generator. Once per bit sent in fact. In other words the energy sent is all over the place. Only an informed receiver can sync and correlate the signal. The act of correlating averages the incoming discrete energies, thus the signal pops out of the noise floor -- statistically speaking. The April 1987 issue of Radio-Electronics has an article about it. The only way to detect the existence of the signal is to monitor a very wide band, and somehow guess the PN sequence. Sounds pretty tricky to me. Sure any code can be broken, but it makes it harder when you have to break the code before you can see it!!!!!!! John Logajan umn-cs!hyper!ns!logajan Network Systems Corp 7600 Boone Ave Brooklyn Park, MN 55428