The following email report from Bob Miller of Viacel, is posted by permission. --Dennis
"Recent test suggests that the digital TV modulation being developed in China (actually deployed in a few locations) is far better in a number of very important ways than either that being used in the US, ATSC 8-VSB, or that being used in most of the world, DVB-T COFDM.
One of the supposed strong points attributed to 8-VSB was that it needed only half the power that the world standard, DVB-T COFDM, needed to cover the same area. Most of the world rejected 8-VSB despite the supposed power advantage saying that in their test this advantage could not be found or was insignificant. They all concluded that the far more multipath resistant DVB-T COFDM was preferred.
Now the Chinese, coming last to the party, have their own standard, DMB-T, that these recent test suggest is far better than either the world standard or the ancient (by todays standards) US standard. With at least four already making DMB-T digital TV receivers for the Chinese market and many more companies in the wings maybe the US should consider bailing out of our disastrous digital TV transition while there are still few receivers in the market and going with the Chinese DMB-T standard. DMB-T Receivers would probably cost less than $10 in a few years if recent history serves.
DVB-T receivers can be bought for $37 in a convenience store in the UK and sell like hot cakes. US receivers sell for $200 to $600 and don't hardly sell at all. With China trying to get digital TV into as many homes as possible before the 2008 Olympics maybe we should try to get on the bandwagon now.
It is not as if we would lose to Chinese manufacturers by going with the Chinese standard. The lowest priced US ATSC 8-VSB receiver is already being made in China, the Hisense USDTV $200 8-VSB ATSC receiver. We are going to buy Chinese digital TV receivers anyway. Why not just buy the best at $10 instead of the worst at $200?
Test S/N reception characteristics (lower is better)
- 18.5 db ATSC OQam Linx (8-VSB)
- 16 db DVB-T (COFDM World standard)
- 15 db DMB-T (COFDM Chinese standard) and
- 12.5 db DMB-T (COFDM Chinese standard) using a similar scheme to DVB-S-2 with LDPC
How close is that to Shannon limit?
So the latest DVB-T compared to the latest 8-VSB gives DVB-T a 2.5 db advantage. Better than I thought. I thought it was about even. Doug don't jump. You can live with this.
These test put the US modulation, ATSC 8-VSB, at the bottom of the power list. That is it takes more power to get an 8-VSB signal to you than it does for all other DTV modulation systems. The supposed advantage was with 8-VSB, NOT SO. Now we have the worst modulation as far as reception in multipath environments and in power requirements.
BTW the DMB-T is the Chinese standard. The Korean Standard has now been changed from DMB-T to T-DMB to differentiate it from the Chinese standard. Both radically different COFDM implementations.
More to come when they let me."