Hi,
I created a flow graph as shown in the attachment. It was modified based on gr-digital/examples/ofdm_tx.grc. I added LDPC encoding for error correction, but I have some problems. There are two places where data is lost.
1. If the length of my sent data is 822 bits, LDPC codeword n=8, k=4, rate=1/2 but 822%4=2, the remaining two bits will not be processed, which will cause My data cannot be sent completely
2. Because my label "packet_len"=100, therefore, the encoded data 820*2=1640, 1640/8=205, 205% 100=5, after going through "repack bits" with the label "packet_len"=100 The remaining data after the module is (205-5)=200 (of course multiply by 4)
So there are two places that will cause the data to not be completely sent. I can think of zero padding to solve this problem, but how does the receiving end know how many 0s I have added (unless it knows what to send)?
I mean how is this problem solved in an actual communication system? Maybe there is a higher-level agreement? After all, what I am doing here is only the function of the physical layer. Does the physical layer ignore these issues?
vedio_tx.pdf