[Discuss-gnuradio] Question on the Packet Decoder

[Zhiwen He]

Hello all,

i'm working on the digital modultaion, and i build a system like this:

random source -> packet encoder -> qam mod -> (adder and noise source) -> qam demod -> packet decoder ->file sink

I found that,  when the amplitude of the noise is low, there will be some data in file sink, but when the amplitude of noise is high, the packet decoder doesn't output any more. Who can tell me why? does the noise destroy the structure of the packet so that i can not be decoded any more?

I also tried psk mod/demod and gmsk mod/demod, it comes the same problem.

thanks,

Zhiwen