An encoder encodes data into a series of parallel codewords. Each codeword is expressed two sets of logic values (e.g., a set of logic 0s and a set of logic 1s) on output nodes. The encoder selects a current codeword from a group of codewords in a codespace which does not overlap the other group of codewords, i.e., codewords in a given group of codewords are not included in any other group of codewords in the codespace. This property allows a receiver of the codewords to be simplified. In particular, a mathematical operation performed on symbols in the current codeword uniquely specifies the corresponding group of codewords. This allows a decoder to decode the current codeword using comparisons of symbols received on a subset of all possible combinations of node pairs.