In article ,
Larry Ozarow wrote:

It's hard to generalize about all digital communication. I think
BPL is some kind of phase modulated OFDM as Frank says, so in that
case you could use essentially rectangular pulses (in practice there
is probably some roll-off and guard time to boot). Each individual
tone would actually occupy a bandwidth much greater than its keying
rate, but since each tone's keying rate is so low compared to the
total bandwidth, the net effect is minor, again exactly as Frank
says.

For single carrier high date rate systems however, the last thing you
want to use is rectangular pulses. The spectrum won't have discrete
harmonics but it will look like (sin(x)/x)^2 in frequency with
significant energy beyond the Nyquist frequency. In those applications a
waveform that falls off in time as t^2 is generally used, though there
are other options, like minimum-shift keying, which can be looked at
either as continuous phase FSK or QPSK using smooth shaped pulses.
Continuous phase modulation has some complications though.

I haven't read how BPL is supposed to work but is it reasonable to
expect that a encoding scheme would be used that would shift the
spectrum requirements downward so that increased coupling would be
needed across the transformers in the power system?

--
Telamon
Ventura, California