Decoding low density parity check codes with finite quantizationbits

This letter is concerned with the implementation issue of the sum-product algorithm (SPA) for decoding the low density parity check codes. It is shown that the direct implementation of the original form of SPA is sensitive to the quantization effect. We propose a parity likelihood ratio technique to overcome the problem. It is shown that for comparable performance the new method can be implemented with much less quantization bits, which can lead to considerably lower decoding cost