On the capacity for distributed index coding

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 all distributed index coding problems with n ≤ 4 messages and equal server link capacities, the achievable sum-rate of the proposed distributed composite coding scheme match the outer bounds, thus establishing the sum-capacity for these problems.