What is the maximum bits-per-symbol possible using FSK on telephone devices?
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From: Green Xenon on 17 Dec 2009 18:54 >Green Xenon wrote: >>> Green Xenon <green_xenon1(a)yahoo.com> wrote: >>> >>>> [glen writes] >>>>> All the FSK I know of are one bit/symbol. >>>> Isn't MFSK [Multiple Frequency Shift Keying] a form of FSK that uses >> more >>>> than 1-bit-per-symbol? >>> Does the M stand for Multiple or does it mean Minimal? >> >> M stands for multiple > >Can you cite an example? Quote from http://en.wikipedia.org/wiki/Multiple_frequency-shift_keying : "Multiple frequency-shift keying (MFSK) is a variation of frequency-shift keying (FSK) that uses more than two frequencies."
From: Green Xenon on 17 Dec 2009 19:03 >Jerry Avins wrote: >> Green Xenon wrote: >>>> Green Xenon <green_xenon1(a)yahoo.com> wrote: >>>> >>>>> [glen writes] >>>>>> All the FSK I know of are one bit/symbol. >>>>> Isn't MFSK [Multiple Frequency Shift Keying] a form of FSK that uses >>> more >>>>> than 1-bit-per-symbol? >>>> Does the M stand for Multiple or does it mean Minimal? >>> >>> M stands for multiple >> >> Can you cite an example? >> >> Jerry > >Take a colour photograph of an artist's depiction of each of >the symbols A - Z, a - z, 0 -9 etc at a resolution of 10 >Mpixels in RAW format,and send your message in the form of >consecutive image files. That should give you around 240 >million bits per symbol. >Note that the OP asked: "What is the maximum amount of >bits-per-symbol of FSK possible using a >telephone system ... " Telephone systems have a bandwidth of 4 kHz. Hence, I doubt they could handle anywhere near 240-Mbits-per-symbol. In FSK, more bits-per-symbol means more frequencies will be used. The number of frequencies must not exceed a the 4 kHz bandwidth or aliasing will occur. In Binary-FSK, there is only 1-bit-per-symbol and thus, two frequencies -- one frequency represents a "1" while the other represents a "0". MFSK is used to decribe FSK with higher-order than the simple Binary-FSK. So I ask again, what is the highest-order FSK compatible with telephone systems? Higher-order = more bits-per-symbol
From: glen herrmannsfeldt on 17 Dec 2009 19:34 Green Xenon <green_xenon1(a)yahoo.com> wrote: (snip) > Telephone systems have a bandwidth of 4 kHz. Hence, I doubt they could > handle anywhere near 240-Mbits-per-symbol. > In FSK, more bits-per-symbol means more frequencies will be used. The > number of frequencies must not exceed a the 4 kHz bandwidth or aliasing > will occur. No. Most importantly, you ignore symbol rate. > In Binary-FSK, there is only 1-bit-per-symbol and thus, two frequencies -- > one frequency represents a "1" while the other represents a "0". One could have more frequencies, as you say, or more FSKs. That is, multiple carriers each modulated at a low rate all at once. That allows for a more adaptive system that gets around much of the non-linearity in the phone system. > MFSK is used to decribe FSK with higher-order than the simple Binary-FSK. > So I ask again, what is the highest-order FSK compatible with > telephone systems? > Higher-order = more bits-per-symbol As I said, at what symbol rate? Otherwise, the other answers are correct. As one said, you can get 28 bits per symbol, and one symbol per day. An amazing amount of processing power to get 28 bits/day through the system. -- glen
From: Green Xenon on 17 Dec 2009 20:15 >Green Xenon <green_xenon1(a)yahoo.com> wrote: >(snip) > >> Telephone systems have a bandwidth of 4 kHz. Hence, I doubt they could >> handle anywhere near 240-Mbits-per-symbol. > >> In FSK, more bits-per-symbol means more frequencies will be used. The >> number of frequencies must not exceed a the 4 kHz bandwidth or aliasing >> will occur. > >No. Most importantly, you ignore symbol rate. > >> In Binary-FSK, there is only 1-bit-per-symbol and thus, two frequencies -- >> one frequency represents a "1" while the other represents a "0". > >One could have more frequencies, as you say, or more FSKs. That is, >multiple carriers each modulated at a low rate all at once. That >allows for a more adaptive system that gets around much of the >non-linearity in the phone system. > >> MFSK is used to decribe FSK with higher-order than the simple Binary-FSK. > >> So I ask again, what is the highest-order FSK compatible with >> telephone systems? > >> Higher-order = more bits-per-symbol > > As I said, at what symbol rate? Let's assume a baud of 1-symbol-per-second.
From: Mark on 17 Dec 2009 20:48
> > So I ask again, what is the highest-order FSK compatible with telephone > systems? > > Higher-order = more bits-per-symbol Hint:::: SNR Mark |