Comparative Study of Q-ary and Binary Low-Density ParityCheck(LDPC) Codes

Nonbinary LDPC codes,capable of correcting burst errors efficiently,provide an effective solution to the high speed data transmission in the fading environment.In this paper,an algebraic method for constructing nonbinary LDPC codes based on finite fields GF(q)(q2) is presented,which is decoded by Fast Fourier Transform(FFT) based q-ary SPA.We compare the performance of q-ary LDPC codes and binary LDPC codes on AWGN channel and Rayleigh fading channels,including LDPC-coded 16-QAM and BPSK modulation.Simulation results show that,with BPSK modulation,binary LDPC codes are better than q-ary LDPC codes on both AWGN and independent fading channels,but not on correlated Rayleigh fading channels.When these two LDPC codes are modulated with 16-QAM,we find that q-ary LDPC codes can achieve better performance than binary LDPC codes with the same spectral efficiency both on AWGN and Rayleigh channels.