  In the context of error control in random linear network coding, it is useful
to construct codes that comprise well-separated collections of subspaces of a
vector space over a finite field. In this paper, the metric used is the
so-called "injection distance", introduced by Silva and Kschischang. A
Gilbert-Varshamov bound for such codes is derived. Using the code-construction
framework of Etzion and Silberstein, new non-constant-dimension codes are
constructed; these codes contain more codewords than comparable codes designed
for the subspace metric.
