Construct the concatenated code from the outer code O and the inner code I. The outer code O is defined over an alphabet that is an extension field of the alphabet of the inner code I. Each symbol of the outer code is encoded using the inner code based on its representation as sequence over the alphabet of the inner code.

Construct the Justensen Code from the RS code R and a primitive element a of the alphabet of R; the powers of the inner code are shifted by k. Each symbol x_i of the RS code is encoded using the inner codes x |-> (x, x.a^(i + k)). Each symbol in the resulting sequence is represented as sequence over the prime field of the alphabet of the RS code.