I just did PDR testing between two USRPs with D8PSK modulation scheme.
The files I used are benchmark_rx.py and benchmark_tx.py. Two
exceptional results confused me a lot:
1, the --tx-amplitude has to be adjusted to the default value (12000),
with which the PDR could reach 100%, otherwise, if 10000 were used, the
PDR would experience a huge slump (around 40%). This phenomenon never
happened to DQPSK.
2, For indoor testing, the distance between two USRPs should be less
than 1 meter. In 1.5 meters, the PDR would also plunge a lot.
Is there any problem with the D8PSK in Gnuradio? Should I modify the
parameters of the carrier tracking and timing syn circuits? The
–costas-loop I used was 0.05 with gain-mu set to 0.001 which worked
very well for DQPSK.