OFMD Known Symbols

GNU Radio
1

Hello I’m trying to modify the OFDM module implemented in GNU Radio, and
I
have a question. In DVB-H I need to set the continual pilot carrier and
the
scattered pilot carrier. Both are known by TX and RX, then, Are the
known
symbols, implemented in OFDM module, pilots carrier?

Thanks!

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2

On Sat, Jun 19, 2010 at 1:20 PM, Chris_Spain [email protected]
wrote:

Hello I’m trying to modify the OFDM module implemented in GNU Radio, and I
have a question. In DVB-H I need to set the continual pilot carrier and the
scattered pilot carrier. Both are known by TX and RX, then, Are the known
symbols, implemented in OFDM module, pilots carrier?

Thanks!

No, the known symbols are preambles used for initial sync of a burst.
There is kind of a placeholder in the code for pilots (in the ofdm
mapper), but we haven’t implemented anything here to handle them in
the receiver. I believe others have done this on their own.

Tom

3

Thanks Tom, but in DVB-H, the continual and scattered pilot are used for
the
sync, If I change, in TX and RX, the position and value of knows
symbols,
Will I lost the sync?

Tom R. wrote:

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4

On Sat, Jun 19, 2010 at 2:11 PM, Chris_Spain [email protected]
wrote:

Thanks Tom, but in DVB-H, the continual and scattered pilot are used for the
sync, If I change, in TX and RX, the position and value of knows symbols,
Will I lost the sync?

Sure, because DVB-H is a continuous stream, so you don’t need to
resync for bursts and the pilots are just used to track it.

In this case, you would want to get rid of the idea of the known
symbols altogether. Then, you’ll need to add the pilot handling code
into the receiver. This will probably call for a pretty thorough
redesign of the ofdm receiver that’s in GNU Radio. It will probably
also require you to write a new ofdm sink C++ block to handle the
specifics of the standard.

Tom

5

Thank you very much Tom

Tom R. wrote:

resync for bursts and the pilots are just used to track it.

scattered pilot carrier. Both are known by TX and RX, then, Are the
Tom

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