Expert: Cezar L. Palconet Date: 11/9/2007 Subject: 1 Gbps on dial-up modems -- physically-possible?
Question QUESTION: Hi:
I might have sent you this question before. I so, I apologize profusely for the repitition. Something was wrong with my browser making me unable to tell whether I sent you this question.
Is it physically possible to for dial-up internet connection to reach a speed of 1 Gbps by using a baud of 1-symbol-per-second [to conserve bandwidth] but 1-billion-bits-per-symbol?
Each symbol carries a billion bits bits but with only 1 baud.
bps = baud X number of bits per baud.
Is this physically-possible?
Thanks,
Green
ANSWER: What limits the bandwidth on twisted pair is the line insertion losses,
With a typical house wiring for telephone in a dial up connection, line losses in 400 Mhz. will be enormous, much so with a 1Ghz. even with the best cable the usable limits is around 400 Mhz.
It is not the bps to a word ratios that determine losses in a cable transmission it is the frequency.
Bps per word is only valid on the modulator, and not the transmission line.
Good luck.
---------- FOLLOW-UP ----------
QUESTION: Why is the telephone wire pair twisted?
Answer Twisted pair cabling is for the purposes of canceling out electromagnetic interference (EMI) from external sources, electromagnetic radiation from the cable, and crosstalk between neighboring pairs. It reduces interference because the loop area between the wires (determines the magnetic coupling into the signal) is reduced.
For packing more bits per baud, this can only be achieve trough an efficient and revolutionary form of modulation, however I would like to suggest reading the Nyquist and Shannon theorem, better understanding on the paradoxity of the two theorems.
All data signals, whether they are transmitted trough, Air, fiber or copper wires are transmitted as electromagnetic waves. And thus are subject to the same rules that apply to it, Due to the physical limitations of media, signals are attenuated above a certain frequency. This limits the rate of information that can be sent, there is no point sending huge amount of data, over a medium, if the receiver will not be able to understand what they are.
