I often have to test hardware RXs and though I have a hardware BER test fixture, it's kind of ancient and difficult to work with. I have fantasized about using a USRP to transmit a PRB (pseudo-random bit-sequence) to a RX modem. The data would then be brought back into GnuRadio and compared with the originally transmitted PRB to determine the actual BER.
To align the data, I figured I could correlate the sent code against the received data to determine any offset and align the data for comparison. The correlation should be pretty forgiving to bit errors if the right PRB is chosen, I think.
My question is: does anyone have additional thoughts about this? I don't think that this sort of tool exists yet in GnuRadio. I have seen BER tools and even a nice BER block from Balint, but I think they all assume the data is already aligned. I imagine that Balint's block could still be used if the alignment was done first. Am I missing any other tools out there?
As for getting the received data back into the flowgraph, I imagine that this might require a new source, like a synchronous serial port. I have used libmpsse to work with some of the MPSSE-enabled FTDI chips before. Maybe that could be implemented as a source block. My other thought was to use a LFTX board and bring in the clock and data as separate RX channels then proceed from there.
Thanks!