Re: COFDM technical details

On Wed, 13 Sep 2006 19:29:36 -0400 Karl S <karls@xxxxxxxxxxxxxxxxxxxx> wrote:

| Another thing to factor in might be the miles-per-watt efficiency. Just
| as SSB is more efficient than FM, I've heard that 8VSB is more efficient
| than COFDM. The rather vague comments I've read suggested "about twice
| the range" for 8VSB...
| I'd also like to get more accurate information.

I think that depends on whether you are comparing equal average wattage,
or equal peak wattage. Generally the information level is average watts.
So with the same average wattage, you should see basically about the same
distance. The issue with COFDM is there is a higher peak/average ratio,
meaning that to achieve the same average power, the transmitter has to
support higher peak power in its linear PA range. For low power that is
not so much of an issue. For high power, it can be critical. However,
VSB (and QAM) modulating a single carrier widely do not have as flat a
power density as OFDM does, because the channel is a bunch of sidebands
rathern than a bunch of low rate carriers.

I'm wanting to simulate some waveforms under a variety of parameters for
different modulation schemes and see what the theoretical spectrum and
envelope curves look like.

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2006-09-14-0316@xxxxxxxx |
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.

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