[opendtv] Re: Comparisons between systems
- From: "Bob Miller" <robmxa@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 15 Nov 2006 11:12:21 -0500
From what I understand about DMB-TH is that it works very well at high
bit rates mobile. For instance we were testing DVB-T mobile at 64 QAM
at data rates of from 12 to 18 Mbps. I was convinced that using
diversity receivers and building a proper SFN that we could do 18 Mpbs
plus as a very acceptable mobile offering.
I am told that DMB-TH without the use of diversity antennas will match
DVB-T with them. And of course DMB-T will also benefit from diversity
antenna.
That would be very impressive. I should note that DVB-T without
diversity was also very good. Good enough to advertise as portable and
knowing that it would work very well mobile as well. Just wouldn't
advertise it as a mobile solution.
Hope to test DMB-TH very soon.
Bob Miller
On 11/14/06, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx> wrote:
I guess some of you guys saw this Doug Lung column:
http://www.tvtechnology.com/pages/s.0001/t.456.html
but didn't catch this interesting tid-bit.
It is interesting to see two similar design approaches, one being the
new Chinese OFDM-based system with advanced FEC and the other being
A-VSB in the STS mode. For all the skeptics, take a look at the most
robust modes and how they compare:
CDMB-T in 8 MHz channel, 4-QAM (most robust), 4K mode, LDPC FEC:
~5 Mb/s and 1.9 dB C/N margin.
A-VSB in 6 MHz, 1/4 rate STS mode (also most robust), turbo code:
4.5 Mb/s and 1.7 dB C/N margin.
To compare capacity fairly, 5 * 6/8 = 3.75, which shows somewhat lower
spectral efficiency for the CDMB-T system, although that 5 Mb/s figure
was approximate.
Also to be fair, no mention of whether the Chinese system was using a
diversity antenna. But then again, the diversity antenna is more
essential and beneficial in a single carrier scheme.
I'd say, not bad for an afterthought to 8-VSB, eh?
Another point about OCRs is a strange paradox that this column also
mentions. Which is, the newer receivers are the most compatible with OCR
nets, however they are also the ones that benefit from OCRs least. In
the sense that they *already* make use of echo energy created by the
single transmitter, without needing an OCR to sort of shape that energy
better.
Bert
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
