Re: [Discuss-gnuradio] Successful transmission in gr-ieee802-11 with adding extra samples (before OFDM preamble)

[Bastian Bloessl]

On 2014-11-29 12:28, Isen I-Chun Chao wrote:
> Hi Bastian,
> Thanks for your reply.
> The peaks you mentioned is like the correlation result?

Yes, exactly

> /Best Regards,
> Isen I-Chun Chao/
>
> On Sat, Nov 29, 2014 at 6:21 AM, Bastian Bloessl <address@hidden
> <mailto:address@hidden>> wrote:
>
>     Hi Isen,
>
>
>     On 2014-11-29 07:01, Isen I-Chun Chao wrote:
>
>         Hi,
>         I am using gr-ieee-802-11 and putting a custom block, which is
>         responsible for adding a 90-sample preamble at the head of incoming
>         sample stream, right after the output of WiFi PHY Hier, as attached
>         figure, generator.png. So the sample stream is changed as attached
>         figure, adding_preamble.png.
>
>         However, in the case of use of transceiver.grc, I can still
>         successfully
>         decode received data, which is keep printing out "Hello World!".
>
>         Does anyone know why adding extra samples at the head of
>         transmission
>         samples does not affect the receiving results? Does it because
>         somewhere
>         in Rx side detect the OFDM preamble so the payload can be normally
>         processed without being affecting by the extra samples placed before
>         OFDM preamble?
>
>
>
>     The sync long block does matched filtering with the long preamble
>     and searches for peaks in a configurable window (sync length
>     parameter). Looks like even if you add 90 symbols the peak that the
>     block is looking for is still in the window.
>
>     Best,
>     Bastian

--
Dipl.-Inform. Bastian Bloessl
Distributed Embedded Systems
University of Paderborn, Germany
http://www.ccs-labs.org/~bloessl/