[opendtv] Re: Mobile ATSC reception paper
- From: Mark Aitken <maitken@xxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 12 Dec 2005 11:50:49 -0500
Other possible alternatives. Look at the ATSC activities being worked on
by Rohde and Schwarz with Samsung. A-VSB provides another promising
avenue of possible progress. It relies on:
i. Deterministic Trellis Reset *(DTR)*
ii. Deterministic Frame *(DF)*
The stated objective of this (A-VSB) proposal is to bring
"Extensibility" to the ATSC 8-VSB physical layer.
Manfredi, Albert E wrote:
>Al Limberg wrote:
>
>
>
>>U.S. patent No. 6,975,689 titled DIGITAL MODULATION
>>SIGNAL RECEIVER WITH ADAPTIVE CHANNEL EQUALIZATION
>>EMPLOYING DISCRETE FOURIER TRANSFORMS will issue
>>tomorrow, December 13. This patent describes Doug
>>McDonald's use of DFT on several-thousand-symbol
>>sequences of samples of 8VSB signal to characterize
>>the reception channel on a continuing basis.
>>Long-signature analysis works well because of data
>>randomization in the 8VSB signal. A second patent
>>will issue early next year describing later work.
>>The several thousand samples do not have to be a
>>training signal and can be taken from a sliding
>>window, so dynamic multipath can be tracked quite
>>closely. In contradistinction to the prior art this
>>is not an incremental approximation procedure, so
>>revealed-ray or concealed-ray dynamic multipath does
>>not upset the apple cart with regard to channel
>>equalization.
>>
>>Characterization times are about 100 microseconds, as
>>I recall.
>>
>>
>
>So what I think you're saying is that a series of 8-VSB
>symbols can themselves be used as if they were training
>symbols, because the data randomization makes them look
>so flat in the frequency domain (in the absence of
>multipath distortion).
>
>So, symbols being 0.09 usec apart, you can look at a
>sliding window of thousands of symbols and obtain a
>good characterization of the dynamic changes in the
>channel within a few usec of time. Much more frequently
>then possible with the actual training sequence, which
>only appears every 24.2 msec.
>
>There is a certain symmetry to this. In COFDM, where
>symbols are very slow, you need to depend on many and
>frequent sync sequences. But you can also accommodate
>these easily, with the multiple active carriers. In
>8-VSB, you can't accommodate enough training symbols
>without seriously degrading the usable bit rate, but the
>short symbol duration can be used to achieve the same
>purpose.
>
>Cool.
>
>Bert
>
>
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--
><> ><> ><> ><> ><> ><> ><>
Regards,
Mark A. Aitken
Director, Advanced Technology
<>< <>< <>< <>< <>< <>< <><
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