[opendtv] Re: Latest S/N test
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 25 Jan 2005 11:19:12 -0500
Bob Miller wrote:
> Recent test of DMB-T, DVB-T, ATSC
>
> S/N
> 18.5 db ATSC OQam Linx
> 16 db DVB-T
> 15 db DMB-T
> and
> 12.5 db DMB-T using a similar scheme to DVB-S-2
> with LDPC
>
> How close is that to Shannon limit?
Can't tell, unless you give the actual bandwidth used
in the RF channel and the channel capacity (b/s). With
that info, the limiting S/N for error-free
communications can be computed.
Strange that the OAM scheme measured lower than ATSC,
but again, need more information. When Linx first
developed that, they claimed 15 dB for the wide
channel. Perhaps having those two extra pilots,
while it does increase robustness, also demands more
power. But they were rather low power. Weird.
If I remember, DMB-T uses a CDMA spread spectrum scheme
to transmit the training sequence, and COFDM for the
signal. Not positive, though.
> So the latest DVB-T compared to the latest 8-VSB
> gives DVB-T a 2.5 db advantage.
That's doubtful, as it would mean DVB-T is capable
of 12.5 dB C/N in a 5.38 MHz channel for ~20 Mb/s.
Perhaps you need to supply more detail on these
tests. And no silly propaganda, please!
BTW, the Shannon limit for 20 Mb/s in a 5.38 MHz
channel would be that you need 10.85 dB of C/N
for error-free comms.
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.
Other related posts:
