I trying to run a GMSK mod/demod test under GRC. My objective is to create a single GSM-like burst and to store it in a file. The waveform should have defined bits (by now I assume them to be random). Thus I created a flowgraph that looks like this Random Source (fixed # of samples, no repeat) -> Packet Encoder -> GMSK Mod (->File Sink gmsk_tx) -> GMSK Demod -> Packet Decoder -> File Sink (integer of bits_out) 1. If I keep increasing the number of bits in Random Source, I have noticed that the number generated complex samples (I read them into MATLAB using read_complex_binary) stays constant at 8496 complex samples until 255 modulated bits. From 255 to 383 it is 2*8496, from 384 to ... it is 3*8496. Are these the bursts? Why are the bound to integers of 8496? 2. When forming a loopback, reading the modulated signal and demodulating it, the bits_out are not demodulated when reading the file bits_out via read_int_binary. Whats wrong with the flowgraph? I attached the respective .grc file. I appreciate any help! -Flo
on 2013-08-12 13:06
on 2013-08-13 15:31
To put it in simple words, I am wondering why the GMSK-Mod blocks always outputs 8192 bits - no matter when I input 50 bits or 255 bits. Is there a GMSK-burst-like modulation happening?