In orthogonal signalling as k increases there is improved error performance or a reduction in required Eb/N0 at the expense of bandwidth.

Orthogonal signals are perpendicular to each other, the inner or dot product between those two signals must equal zero, one vector has zero projection over the other because they do not share same signal space.

Some examples of structured sequence or structured redundancy codes are block codes, convolutional codes and turbo codes.

Antipodal signals are mirror images, one is negative of the other and they are 1800 apart.

Channel coding can be partitioned into two area of studies, one is waveform coding or signal design and the other is a structured sequence or structured redundancy.

The cross correlation is the measure of distance between two vectors. The smaller the cross correlation value the greater the distance between the two vectors.

Non orthogonal signalling manifests improved bandwidth efficiency at the expense of degraded error performance and increases in required Eb/N0.

In orthogonal set all cross correlation coefficients can be made zero.