Data storage systems may include a solid-state memory array configured to store encoded data units and a controller configured to decode the encoded data units. Decoding the encoded data units may include updating a check node of a plurality of check nodes associated with a parity check matrix by identifying first and second sets of variable nodes in a plurality of variable nodes associated in the parity check matrix with the check node and constructing a trellis based on the second set of variable nodes. The trellis may be used to determine a message and, based at least in part on the message, a first set of messages to be sent from the check node to the first set of variable nodes may be determined. A second set of messages to be sent from the check node to each variable node in the second set of variable nodes also may be determined.