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Microcap & Penny Stocks : International Automated Systems

IAUS 0.0400

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Jul 8 5:00 PM EST

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To: paulmcg0 who wrote (127)	7/15/1996 3:12:00 PM
From: Lyle Abramowitz	of 7618

Paul, it's taken me a while to get back to you on Shannon's theorem. I will do it a little differently here. As I've noted in several posts here one of the major issues with IAUS's claims is that their feasibility varies widely with the transmission channel in question. The claimed data rate for cable are low, if anything. I don't understand the wireless claims. So let's go the the PSTN which I do understand. One form of the Shannon limit is that reliable communication can be achieved at a maximum bit rate of Blogbase2(1+ signal-to-noise ratio), where B is the bandwidth in Hz of the communication channel and the signal-to-noise ratio is measured in the bandwidth B. "Reliable communication" means that the error rate can be (in theory) driven as low as one wants through the use of multiple bit per symbol coding and forward error correction coding, but this point is not too important for this discussion. The claim made in the Investors Business Daily of 17 June 1996 is that 150000 to 600000 baud can be achieved over "POTS". I interpret this to mean at least 150000 bps over a dial-up phone connection. Note that there is an ambiguity with the term "baud", I'm giving them as much slack as possible in minimizing their claim. I assumed the standard PSTN bandwidth of 3.2 kHz. Running through the calculation the signal-to-noise ratio required to support that link is about 138 dB or 7 10^13. The PSTN has an SNR of about 30 dB or 1000. I'll also give a heuristic intrepretation of the Shannon limit for anyone interested. In order to convey information by modulating something (a radio wave, a light wave or even smoke signals) the signal must transition to various states (or waveforms) at some rate. The bandwidth parameter (among other things) is roughly a measure of how rapidly the state can changed and still be determined accurately at a receiver. The state of a modulation (or a "symbol") can be one of several--for example a sinewave can have its phase varied among four fixed angles (QPSK). Higher level modulations with greater numbers of states or symbols can be also used. As more states are used the signal becomes more complex and requires more structure. A question then arises: can the number of modulation states be endlessly increased? The answer is no, because of noise. Noise tends to distort signals--changes the "shape" of a given waveform. A more highly structured waveform can tolerate less distortion, as it is more easily distorted into a "shape" which would be mistaken at the receiver for a different symbol than that which was transmitted. Thus, the signal-to-noise ratio in Shannon's theorem gives the limit to how much structure a waveform can have if it is to be transmitted over a particular channel. Paul, I'm curious to see a description of DWM. I imagine that it does "work", just that it will not perform as indicated by IAUS. Is there a way for me to get a description of the scheme? Lyle

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