If an LDPC encoder with code rate 3/4 was used and parity check matrix of dimension $H=168$ rows $\times 672$ columns is used, is it correct to say that the maximum number of information bits in each LDPC codeword is 168 bits?
I think the answer is wrong as $\frac{k}{n}= \frac{3}{4}= \frac{504}{672}$ and therefore the maximum number of bits is 504.
Update:
1) If 168 bits instead of 504 bits are used with 3/4 code rate, why is the effective rate with shorteneing equal to 1/2?
2) what is the difference between systematic and non systematic LDPC coders?