Recent studies show that dynamic scheduling using the latest available information is superior to the flooding scheduling. While the existing works on informed dynamic scheduling focus on belief propagation (BP) based algorithm for binary LDPC codes, in this paper we devise novel methods which are appropriate for majority-logic decoding of non-binary LDPC codes. Firstly we propose a low complexity extrinsic message based decoding algorithm for non-binary LDPC codes. The novelty of this decoding algorithm lies in that we compute extrinsic messages and iteratively update the messages in every iteration. Then we propose a dynamic scheduling schemes specifically designed for majority-logic decoding of non-binary LDPC codes. The proposed scheduling method, named informed dynamic scheduling, can achieve better performance compared with the layered and the flooding schemes.Index Terms-LDPC; Non-binary LDPC; Informed dynamic scheduling; Majority logic decoding.
I. INTRODUCTIONLow-Density-Parity-Check (LDPC) codes were firstly invented in early 1960s by Gallagar [1] and rediscovered by Mackay [2] in 1996. It has been proved that binary LDPC codes can achieve rates close to channel capacity when codeword length is long enough [3], and LDPC codes have become candidate communication protocols (WiFi, WiMax, etc). Recently, their counterpart, non-binary LDPC codes constructed over Galois field (GF) of size q, have shown their potential in improving the coding gain especially at small or moderate codeword lengths, or when higher order modulation is employed. By now, a great deal of research efforts have been done on non-binary LDPC codes defined over GF(q) [4]-[7], for some q > 0.Although non-binary LDPC codes have shown significant improvement in performance, the decoding process is much more complicated than binary LDPC codes. A straight-forward implementation of belief-propagation (BP) decoder requires O(q 2 ) complexity. Mackay [8] devised a fast Fourier transform (FFT) based q-ary sum-product algorithm (QSPA) to reduce the complexity from O(q 2 ) to O(q log q). Declercq [9] proposed the extended min-sum (EMS) algorithm where only a subset of the n m most significant messages in GF(q) is utilized. This decoding technique can reduce the computational complexity because n m is usually much smaller than q. In addition, the min-max algorithm [10] further reduces the complexity by replacing the sum operation with max operation in check node update. Unfortunately, these algorithms are still too complicated for some practical applications.