[ biased article?]
HI Bill--you know that I think there is a misinformation
campaign going on from both camps. I have several
problems w/this article, but it would be good to get
Steve M or Rupert's respose rather than my limited
knowledge one
I find the following disturbing, to say the least:
>>It has been shown theoretically that for any loss and noise vs. frequency shapes, a single-channel system such as CAP with an ideal DFE provides the same performance as a DMT system with ideal bit allocation. However, practical implementation issues cause both systems to deviate from ideal. The single-carrier system requires a well-designed DFE with more than 100 taps. The DMT requires extremely high constellation sizes, in the order of thousands of points, in the high SNR region. Also, a practical DMT system is restricted to an integral number of bits per subchannel, further reducing bit rate from the theoretical ideal. For these reasons, recently developed DFE techniques have caused CAP performance, in terms of transmission distance for a given rate, to exceed that of DMT.
As I understand it, an ideal DFE would require much more
power consumption that a typical DMT system. Notice, that
he never said that such a system existed or ever could be built.
Then he goes on to say that power consmption is not an
issue for CAP, surreptitiously implying that you can build a
CAP modem with better noise rejection AND lower power.
Not a blatant lie, but........ |
