In this article we construct a new family of linear maximum rank distance (MRD) codes for all parameters. This family contains the only known family for general parameters, the Gabidulin codes, and contains codes inequivalent to the Gabidulin codes. This family also contains the well-known family of semifields known as Generalised Twisted Fields. We also calculate the automorphism group of these codes, including the automorphism group of the Gabidulin codes.
Delsarte's duality theoremDefine the symmetric bilinear form b on M m,n (F) by b(X, Y ) := tr(Tr(XY T )),where Tr denotes the matrix trace, and tr denotes the absolute trace from F q to F p , where p is prime and q = p e . Define the Delsarte dual C ⊥ of an F p -linear code C by C ⊥ := {Y : Y ∈ M m,n (F q ), b(X, Y ) = 0 ∀X ∈ C}.