One choice of feedback matrix for FDNs is a specific Householder reflection proposed by Jot (1992):
where
is the specific vector about which the input vector is reflected in -dimensional space.
In addition to being lossless and not requiring any multiplies when is a power of 2 (for fixed-point implementations), the Householder matrix is attractive because the feedback matrix-times-channel-vector operation can be computed with only additions (by first forming
times the input vector, applying the scale factor , and subtracting the result from the input vector).