I was able to implement qpsk on my board. I could check data transfer between two seperate boards and it working fine. but what i observed was sometimes when mu goes to maximum it starts toggling between max and min so because of which the decoded data has some errors. It is continuous transmission so i am think i should not stop timing recovery in between burst of actual data. otherwise pure carrier is transmitted.
I am assuming wired transfer between board should have zero errors. how do i fix mu problem. could it be because of base band filtering or RRC filtering. or do i have to tweak loop parameters??? any expert help would help
Briefly explained the setup:
My receiver contains: AGC,timing recovery,carrier recovey blocks.
I am using gardner timing recovery. It contains fractional interpolater, TED, loop filter, interpolater control (looped back to fractional interpolater) . Mu is the fractional input to the fractional interpolater or the interpolation control. THe input to this block is 2 samples/symbol and out is also 2 samples per symbol. But we are picking only one sample based on data valid.