Differentiating trapping sets with the same label [w; u]

Trapping sets (TSs) have been known to contribute to errors in the decoding of low-density parity-check (LDPC) codes, particularly at the high signal-to-noise ratio (SNR) region. Moreover, TSs with the same label [w; u] are considered equivalent under the automorphism of the graph of a regular code. But according to our our simulations, TSs with the same label [w; u] are producing different error rates in the case of irregular codes. In this paper, we will identify and explain the cause of the differences in error rates for TSs with the same label. Further, we will propose a simple mechanism to differentiate these TSs.