[BC] TV Standards

[Dan Dickey]

> At 08:27 AM 10/18/2005, DANA PUOPOLO wrote
>>Look at what the HDTV 'Grand Alliance' did. Because they refused to wait 
>>SIX
>>MONTHS, we got saddled with 8 VSB HDTV, which as about a quarter as robust 
>>as
>>COFDM, the system the rest of the world adopted.
>>

This is something that is often repeated as a fact when it is more accurate 
to say it is an opinion held by many.  There are many studies on both sides 
that would indicate one system is better than the other.  But it is fairly 
easy to show than if both systems are done "correctly" then a single carrier 
will beat a COFDM system.  The reason is that single carrier systems are 
more power and spectrally efficient.  The oft mis-stated opinion that OFDM 
systems are better in multipath environments over single carrier has been 
shown by a few researchers to not be true.

One indication about the merits of single carrier versus multi-carrier 
modulation is to look at the mobile telephone industry.  There are no 
multi-carrier systems deployed because of the efficiency issues.  However, 
there are some multi-carrier broadcast systems deployed mostly due to the 
lack of time available to properly characterize and design a single carrier 
system.  Single carrier systems are harder to get right than OFDM.

>>Because they couldn't wait, our HDTV system is INTERLACED, instead of 
>>being
>>progressive scanned (which would have made it compatible with computer
>>video).

There are over a dozen video formats in the ATSC standard.  Some of them are 
progressive HD formats as well as interlaced verions.  The issue isn't with 
the standard.  It's with the display technology.  It's still cheaper to make 
an interlaced tube display than a progressive display.  It probably always 
will be cheaper.

Best regards,
Dan