  The index coding problem is studied from an interference alignment
perspective, providing new results as well as new insights into, and
generalizations of, previously known results. An equivalence is established
between multiple unicast index coding where each message is desired by exactly
one receiver, and multiple groupcast index coding where a message can be
desired by multiple receivers, which settles the heretofore open question of
insufficiency of linear codes for the multiple unicast index coding problem by
equivalence with multiple groupcast settings where this question has previously
been answered. Necessary and sufficient conditions for the achievability of
rate half per message are shown to be a natural consequence of interference
alignment constraints, and generalizations to feasibility of rate
$\frac{1}{L+1}$ per message when each destination desires at least $L$
messages, are similarly obtained. Finally, capacity optimal solutions are
presented to a series of symmetric index coding problems inspired by the local
connectivity and local interference characteristics of wireless networks. The
solutions are based on vector linear coding.
