  The demand for flexible broadband wireless services makes the pruning
technique, including both shortening and puncturing, an indispensable component
of error correcting codes. The analysis of the pruning process for structured
lowdensity parity-check (LDPC) codes can be considerably simplified with their
equivalent representations through base-matrices or protographs. In this
letter, we evaluate the thresholds of the pruned base-matrices by using
protograph based on extrinsic information transfer (PEXIT). We also provide an
efficient method to optimize the pruning patterns, which can significantly
improve the thresholds of both the full-length patterns and the sub-patterns.
Numerical results show that the structured LDPC codes pruned by the improved
patterns outperform those with the existing patterns.
