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Re: [Discuss-gnuradio] OFMD Known Symbols

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] OFMD Known Symbols
Date: Sat, 19 Jun 2010 14:23:05 -0400

On Sat, Jun 19, 2010 at 2:11 PM, Chris_Spain <address@hidden> 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 Rondeau wrote:
>> On Sat, Jun 19, 2010 at 1:20 PM, Chris_Spain <address@hidden>
>> 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

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