Re: [Discuss-gnuradio] Packet chopping

[Tom Rondeau]

On Tue, Mar 10, 2009 at 4:13 PM, Peter Vizi <address@hidden> wrote:
> List,
>
> We are implementing a packet-based system with gnuradio, and we
> experience that the packets are not sent in one flush from the USRP.
>
> In our transmitter we are maintaining a data path and a control path, so
> we exactly know where is the beginning of a packet and where is the end.
> We use this method to pad the outgoing complex waveform to the multiple
> of 128 samples, as it is required by the USRP (in a particular setup our
> packet is 468 samples long, so it is padded to 512 samples).
>
> Image [1] shows the abs of the complex waveform that our transmitter
> block produces, this is fed into the USRP sink (a copy of the ofdm
> benchmark's USRP sink). Image [2] shows abs from the received signal
> when the transmitter was operating. You can discover the preamble in the
> received signal and similar things to the rest of the packet, but this
> is not continuous. Interestingly there seems to be some parts from the
> previous packet before the preamble.
>
> We tried to set the fusb_block_size of the USRP sink to 8, so this
> buffer will hold a whole packet, but this did not help either.
>
> Any ideas would be greatly appreciated.
>
> Best, Peter.
>
> [1] http://nd.edu/~pvizi/transmitted.png
> [2] http://nd.edu/~pvizi/onair.png


Please label your axes! I'm not sure what I'm looking at here. Also,
from what I gather, you are doing a comparison, but you are using two
different ranges in the x-axis. I am not at all clear what the problem
you are having is from your explanation.

Tom