I am trying to calculate BER for bpsk and qpsk using digital_bert_tx.py and digital_bert_rx.py. i want to compare BER of qpsk and bpsk. At same SNR around 20db i am getting constant .16 BER for qpsk and for bpsk it is 1e-12. when i change the SNR using gain of Transmitter and Receiving end there is no change in BER for qpsk, for bpsk its changes. I am not able to understand why with qpsk its not working. if anyone has any idea or anyone who has calculated BER previously please help me.