Re: [Discuss-gnuradio] Digital communications between two USRP1

[Nick Foster]

On Tue, 2010-12-14 at 08:21 -0800, nadia yoza wrote:
> Hi all,
> 
> I want to send and receive data between two different USRP1 (both
> directly connected) using the GMSK modulation at 30 MHz. I am using
> the GMSK mode implemented in GNU Radio. For transmission, I am using
> the LFTX daughterboard and for reception, the BasicRX. 
> As a result, when I transmit at low frequencies(e.g. 10 MHz), all the
> data is always correctly received. However, when I use 30 MHz, the PC
> can receive the data correctly most of the time, but sometimes it
> doesn't receive anything at all. I've also tried with other
> modulations (the types of PSK and QAM implemented in GNU Radio),
> different rates, different longitude of the cables, but the problem
> persists. When tested in a loop using the same USRP for transmission
> and reception, all the data was always correctly received.
> Is there a way to do digital communications using the USRP1 at 30 MHz?
> If so, is there anything I should take into account?
> 
> Best regards,
> 
> Nadia
> 

You need to take into account frequency drift between the two USRPs,
either by manually offsetting the frequency parameters you use or by
performing real frequency estimation in your demodulation.

--n