[CLUG] [OT] Genesis (Is this actually OT?)
Donnchadh Ó Donnabháin
d_odonnabhain at vistech.ie
Tue Feb 29 11:30:11 GMT 2000
Owen Kelly wrote:
> Most telephone people moan on and on about the bandwidth capability of telephone cable. The theoretical
> bandwidth of phone lines is about 4-5 kHz. So, instead of being your average modem, Im guessing that the
> "Black Box" Genesis use uses maybe 3Khz for bandwidth modem style, and then uses serious multiplexing of
> signals in the other 1.5kHz, increasing the range of data that can be transmitted dramatically. Most modems
> only multiplex data using amplitude modulation, frequency modulation, or some other form that I cant
> remember, possibly due to some college social hangover ...
> 56k standard is also about 3-4 years old, no one ever said that would be the last system to transmit data on
> good old copper phone lines.
The reason 56K modems are limited to 56Kb/s not the line between the
and the exchange, but the fact that the line is sampled at 8Ksamples/s
and converted to 8 bits using mu-law/A-law compression => 8x8K =
64Kbit/s. The line
itself has much greater capacity than the 3400Hz bandwidth used by
Are Genesis going to connect to customers directly through their own
or are they going to get n*45Mbit/s interconnects to Eircom exchanges
rates and put their adapters/codecs in the Eircom exchange?
Then there's the issue of the channel capacity of the phone line. The
of a phone line is more than 3400Hz but I don't think it would be
give 45Mbit/s. xDSL already places strict limits on the quality of line
be used. Anyway the Hartley-Shannon Law gives the theoretical maximum
C = B lg(1 + S/N)) b/s
where lg is log base 2
S/N is signal to noise ratio
B is bandwidth
C is channel capacity in bits per second.
Also EMC regulations would prevent them just increasing the power level
to improve SNR.
More information about the Cork