  In practice, LDPC codes are decoded using message passing methods. These
methods offer good performance but tend to converge slowly and sometimes fail
to converge and to decode the desired codewords correctly. Recently,
tree-reweighted message passing methods have been modified to improve the
convergence speed at little or no additional complexity cost. This paper
extends this line of work and proposes a new class of locally optimized
reweighting strategies, which are suitable for both regular and irregular LDPC
codes. The proposed decoding algorithm first splits the factor graph into
subgraphs and subsequently performs a local optimization of reweighting
parameters. Simulations show that the proposed decoding algorithm significantly
outperforms the standard message passing and existing reweighting techniques.
