  This paper considers the problem of network coding for multiple unicast
connections in networks represented by directed acyclic graphs. The concept of
interference alignment, traditionally used in interference networks, is
extended to analyze the performance of linear network coding in this setup and
to provide a systematic code design approach. It is shown that, for a broad
class of three-source three-destination unicast networks, a rate corresponding
to half the individual source-destination min-cut is achievable via alignment
strategies.
