  We consider the three-receiver Gaussian multiple-input multiple-output (MIMO)
broadcast channel with an arbitrary number of antennas at each of the
transmitter and the receivers. We investigate the degrees-of-freedom (DoF)
region of the channel when each receiver requests a private message, and may
know some of the messages requested by the other receivers as receiver message
side information (RMSI). We establish the DoF region of the channel for all 16
possible non-isomorphic RMSI configurations by deriving tight inner and outer
bounds on the region. To derive the inner bounds, we first propose a scheme for
each RMSI configuration which exploits both the null space and the side
information of the receivers. We then use these schemes in conjunction with
time sharing for 15 RMSI configurations, and with time sharing and two-symbol
extension for the remaining one. To derive the outer bounds, we construct
enhanced versions of the channel for each RMSI configuration, and upper bound
their DoF region. After establishing the DoF region, in the case where all the
nodes have the same number of antennas, we introduce some common properties of
the DoF region, and the capacity region of the index coding problem.
