Concatenation of linear block codes enhances the performance with respect to the use of single linear block codes, while increasing the decoding complexity. In particular, the serial concatenation of linear block codes has proven to be an important tool for the design of powerful binary linear short codes. This was decisive for the discovery of new codes capable of approaching the bounds of the best possible codes at finite length. The class of convolutional codes, upon termination, are known to provide very powerful codes for large memory values at the encoder. However, the decoding complexity of these codes grows exponentially with their encoding memory, preventing the practical use of very large memories.