----- Original Message ----- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
John Shutt wrote:At the 2000 NAB, Sinclair used HM-COFDM to delivered 13.6 Mbps to fixed receivers on the exhibition floor using indoor antennas, and simultaneously delivered 4.5 Mbps to a portable Nokia Mediascreen that worked everywhere in Las Vegas, including in a car traveling at well over the legal highway speed limit, and could only be made to fail when shut inside of a transmitter cabinet. At the 2007 NAB, A-VSB delivered 14 Mbps to fixed receivers and 500 Kbps to mobile receivers that never broke 25 MPH.Question 1: Did you do a C/N margin comparison? If not, why not? What are we comparing here?
Margins for HM-COFDM: 19.6 dB and 10 dB. I might add that those margins were, as I repeat myself, good enough for the high bitrate stream to be received inside the hall with bowtie antennas, and the robust stream was good enough to be receivable everywhere in Vegas except inside a closed transmitter cabinet.
Margins for 8VSB vary with the amount of equalization requred, so without knowing how many eq taps are engaged, how can you measure S/N?.
Question 2: Did the mobile test try highway speeds for A-VSB? If not, why not? What are we comparing here?
I suppose the A-VSB busses couldn't get to highway speeds on the Strip. What we are comparing is the cost in bits lost from the main bitstream for each bit in the robust stream. E-VSB and A-VSB are horrible at that, and the overhead associated with A-VSB in creating the 'psudo training sequences' lowers the total available to about 18.5 MBps, less than the COFDM mode used in the Sinclair Baltimore tests.
And what I didn't mention is that the high bitrate stream all by itself is receivable in the mobile mode, even if HM-COFDM weren't used, as demonstrated by the infamous Bob Miller video. I still have a copy if you want to watch it. Why you refused to watch it is beyond me.
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