  Partial ordering of communication channels has applications in performance
analysis, and goes beyond comparisons of channels just on the basis of their
Shannon capacity or error probability. Shannon defined a partial order of
channel inclusion based on convex mixture of input/output degradations of a
discrete memoryless channel (DMC). In this paper, extensions to channels other
than DMCs are considered. In particular, additive noise channels and phase
degraded channels, and multiple input multiple output (MIMO) linear Gaussian
channels (LGC) are considered. For each of these models, the conditions under
which the partial order becomes a lattice are also discussed.
