A computationally efficient selective node updating scheme for decoding of LDPC codes

In this paper, we introduce a computationally efficient selective node update algorithm for the decoding of low-density parity check codes. Unlike the standard sum-product algorithm, where all bit and check nodes are updated at each decoding iteration, the developed algorithm only updates unreliable check and bit nodes. A simple reliability criteria is developed to determine the active bit and check nodes per decoding iteration. Based on the developed technique, significant computation reductions are achieved with very little or no loss in the BER performance of the LDPC codes. At a WER of 10(-5), 91.8% and 72.7% check node and 80% and 41% bit node computation reductions are obtained for a (96, 48) and a (504, 252) LDPC code, respectively. The proposed method can be implemented with a slight modification to the standard sum-product decoding algorithm with negligible additional hardware complexity. From a hardware point of view, the proposed algorithm offers power reductions proportional to the computation savings and it leads to higher decoding speeds in serial implementations by decreasing the number of required memory accesses.