On 02/08/2016 09:12 PM, Peter C. Wallace wrote: >> The number of bits required goes to the root of Shannon's information >> theory. We see how effective it is in our daily life everywhere and it >> is better than analog. >> >> Telephony has been digitalized completely today. Television has >> transitioned from analog to digital, freeing more than 50% of the >> bandwidth, while increasing the number of channels. Radio will follow >> (currently running parallel). > > I would disagree here, many high speed transmission systems mix > analog and digital techniques to get a higher bandwsith at a lower > symbol rate (100BT ethernet uses MLT3 (3 level) and 1G Ethernet uses > PAM5 with 5 signal levels)
Actually, digital channels send X bits per symbol for X > 0. F.ex. 256-QAM, used in digital TV broadcasts, sends 8 bits for each transmitted symbol. Standard async serial coding (8n1) sends effective only 0.8 bit per symbol. You are right that there is a combination of analog/digital here, but the fact is that all signals are analog if you get to the bottom of it. It is the digital /interpretation/ of the signal that enables you to gain large benefits. Information theory states that the recovery of the signal is dependent on the coding of the signal. That is, coding at several levels (hardware and software). For example using predictive filters , compression and FEC. The theory does not state how the coding is performed, merely that there is a limit to what you can do. And that limit is a very large number. But, I should not hijack the thread with information theory... -- Greetings Bertho (disclaimers are disclaimed) ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
