I’m currently using GNU Radio to transmit a signal from a file source between two LimeSDR-Mini v2.4 devices, connected via a wired link at 30 MHz. On the transmitter side, I’m utilizing a constellation modulator, and on the receiver side, I have a polyphase clock sync, Costas loop, and an equalizer in place.
The issue I’m encountering is that when I connect the Tx and Rx of the same LimeSDR, the data is decoded correctly. However, when I transmit between two separate LimeSDRs, the signal is not decoded properly.
Is there any special consideration or configuration required for transmission between two different LimeSDRs?
Can your receiver deal with a frequency error? 2 different units may have a frequency error, while 1 unit receiving itself will cancel out any error in the TCXO.
Are you sure your polyphase timing correction works? I’ve seen people fool themselves by doing a loopback like this, and because the timing was already correct, a non-working sync section had no impact.
Can you try running your transmission in software loopback, but with a programmable impairment block to add timing error, frequency error etc. and see what breaks the recovery?
I tried with frequency offset without the channel and it can adjust upto 20 KHz with a sampling frequency of 1 MHz. I also tried the timing error and it was recovered. Although a higher frequency offset definitely breaks the recovery.
Is there any example grc file of using gnuradio with two different LimeSDR without using any external clock or synchronization?
