Necessary and sufficient condition for Tanner codes without girth 4
Yang Xiao · Systems engineering and electronics · 2009
To solve the problem of the girth 4 which will lead to a serious decrease in the performance of quasi-cyclic low-density parity-check(QC LDPC) codes,this paper presents the necessary and sufficient conditions of Tanner codes without girth 4 in the form of several theorems.These theorems can be used as the constraint conditions for the construction of Tanner codes.To construct the Tanner codes without girth 4 needs to adjust the dimension and the shift factors of the circulant matrices of the given sparse parity-check matrices according to the proposed theorems.Examples are provided to verify the theorems,and computer simulation results show that the Tanner codes obtained by proposed constructions achieve good BER performance compared with that of randomly constructed LDPC codes.