  The distributed index coding problem is studied, whereby multiple messages
are stored at different servers to be broadcast to receivers with side
information. First, the existing composite coding scheme is enhanced for the
centralized (single-server) index coding problem, which is then merged with
fractional partitioning of servers to yield a new coding scheme for distributed
index coding. New outer bounds on the capacity region are also established. For
213 out of 218 non-isomorphic distributed index coding problems with four
messages the achievable sum-rate of the proposed distributed composite coding
scheme matches the outer bound, thus establishing the sum-capacity for these
problems.
