On the girth of Tanner (3,7) quasi-cyclic LDPC codes

S. Kim, et al, have been analyzed the girth of some algebraically structured quasi-cyclic (QC) low-density parity-check (LDPC) codes, i.e. Tanner (3,5) of length 5p, where p is a prime of the form 15m+1. In this paper, by extension this method to Tanner (3,7) codes of length 7p, where p is a prime of the form 21m+ 1, the girth values of Tanner (3,7) codes will be derived. As an advantage, the rate of Tanner (3,7) codes is about 0.17 more than the rate of Tanner (3,5) codes.