Hi everyone,
I've been trying to implement a DSSS encode/decode stage on top of the GNURadio tutorial BPSK transceiver chain to study GPS/IMU applications in university. Before that, I tried running OOT modules that implemented DSSS but I was unsuccessful in getting any of them to run, even in the proper software versions they were intended for. Thus, I'm running in a few problems regarding this:
* I'm having trouble understanding how to properly spread my text file bit stream. Is a chip rate of Rc = 10 equivalent to interpolating the bit input by 10? I'm currently taking the following approach on a Embedded Python Block:
output_items[0][:] = np.bitwise_xor( np.repeat(input_items[0], len(self.chip)), np.tile( self.chip , len(input_items[0] ) ) )
where
input_items = input int8 (unpacked bits)
chip = vector int8 (spreading sequence)
interp = len(chip), according to the chip rate
* In the decoding stage, I'm unsure how to align the bit stream to properly multiply it by the spreading sequence. Should I use Tags? Is there any way to implement it using built in modules? I looked into the "PN Correlator", "Correlation Estimator" and "Correlate Access Tag" block but haven't found any examples on how to follow up in this case.
* If anyone can point me to any examples of
DSSS
implementations or better ways to accomplish it using builtin blocks, it is also much appreciated.
I'm currently using GNURadio 3.8.0, but I'm willing to move versions if it is necessary.
Thanks for taking the time to read my questions.
Best regards,
Gabriel Pinheiro