[Discuss-gnuradio] decode problem in benchmark

[yeran]

Hi everyone,

I have a question about benchmark decoding. I'm using bpsk mod and demod.

In order to understand what's happening in the demodulation process, I added a file sink after time_recov block and after unpack block respectively. According to my understanding, the receiver block does the mapping and decision making process. It maps the complex number in rx_time_recov.32fc to 1 if the complex number is bigger than zero. It will map the complex number in rx_time_recov.32fc to 0 if the complex number is smaller than zero. And this mapping result, 1 or 0, is written into rx_unpack.8b.

However, in real experiment, I found wired result. Sometimes the mapping is using the algorithm as above, sometimes it is totally the opposite way. (complex number in rx_time_recov.32fc smaller than zero will be mapped as 1). Even this algorithm is not the same within one packet. For instance, the access code is mapped using one algorithm, and the payload is mapped the other way.

I don't understand why this is happening. Is there anything to do with the phase error or anything? Can anyone give me some suggestions on how it works?

Thanks!
Ada