  For improving coarsely quantized decoding of LDPC codes, we propose a check
node aware design of the variable node update. In contrast to previous works,
we optimize the variable node to explicitly maximize the mutual information
preserved in the check-to-variable instead of the variable-to-check node
messages. The extended optimization leads to a significantly different solution
for the compression operation at the variable node. Simulation results for
regular LDPC codes confirm that the check node aware design, especially for
very coarse quantization with 2- or 3-bit messages, achieves performance gains
of up to 0.2 dB - without additional hardware costs. We also show that the
2-bit message resolution enables a very efficient implementation of the check
node update, which requires only 2/9 of the 3-bit check node's transistor count
and reduces the signal propagation delay by a factor of 4.
