## OA with Only One Run / Dual of Code Without Redundancy

A linear orthogonal array OA(1, s, Sb, 0) which is the dual of a linear [s, s, 1]-code exists for arbitrary values of s.

### The Orthogonal Array (Trivial OA)

The orthogonal array A = { 0} ⊂ Fbs is a linear OA(1, s,Fb, 0) for arbitrary values of s. It has only a single run 0 and therefore strength k = 0. Thus it is called trivial OA or OA with only one run. The generator matrix of A is an s matrix. If interpreted as a linear code, A is an [s, 0, s + 1]-trivial code.

### Its Dual Code (Code Without Redundancy)

The dual code C = A is a linear [s, s, 1]-code over Fb, namely the code without redundancy or complete code. It consists of all code words in Fqs, i.e., C = Fbs. Since every possible vector from Fbs is a valid code word, C has no redundancy and cannot even detect a single error. Any regular s×s-matrix over Fb is a generator matrix of C, in particular the s×s identity matrix. If interpreted as a linear orthogonal array, C is an OA(bs, s,Fbs), the complete OA.

### Optimality

A trivial OA meets the trivial lower bound on t and the Rao bound with equality and is therefore an OA with index unity as well as tight OA. Alternatively a code without redundancy is an MDS-code as well as a perfect code.