Quote:
Originally Posted by glatt
OK all you experts, assuming the advances can be made to increase the range to hundreds of miles, what about interference? If you have a military theater of operations with 200,000 RFIDs all transmitting at the same frequency at a range of hundreds of miles, how will you not have interference? This isn't cars zooming single file under a reader, or jeans coming out of a store one at a time.
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There are numerous solutions to this problem. Ethernet demonstrates one using collision avoidance. Two common solutions include time domain and frequency domain multiplexing. AT&T cell phone systems used frequency domain multiplexing. Other better systems use time domain multiplexing. Another is Wide Band Spread Spectrum broadcasting. A technology originally patented by Hedy Lamar in the WWII era. A technology that probably should have been appearing in a scaled down version in Version N of Wifi.
Also useful are antenna polarity. This is why satellites with only 12 frequencies (channels) can operate 24 transponders on those 12 frequencies.
Obviously is antenna gain. MaggieL posted pictures of her satellite directional antenna - a yahgi. I suspect it is so directional as to require adjustments to within single digit degrees.
And then we go back to Shannon's 1940s theories on communication. How to cut through the noise? Two methods. More power or slower data rates. Today those revolutionary concepts should be common knowledge to the computer user.