Digital communications interleavers re-order the bits of a data coding block in a way that can be described by a table of indices that map the original order to the interleaved order. Conventional interleavers include index table interleavers, which store an index table ahead of operation and algorithmic Interleavers, which generate the indices during operation.Described herein are a new class of interleavers: Subset Transform Interleavers. A subset of generator outputs is selected and processed to create the interleaver indices. The selection is determined apriori and the selection results are stored in a Subset Usage Table. During operation, the generator is operated again and the Subset Usage Table entries determine which generator outputs are used. The generator may be a pseudo-random number generator. Implementations can use an Indexes Remaining Table, which can additionally be manipulated during operation such that it returns to an initialized state after each block interleaving process.