  This paper provides an explicit expression for the capacity region of the
two-user broadcast Z channel and proves that the optimal boundary can be
achieved by independent encoding of each user. Specifically, the information
messages corresponding to each user are encoded independently and the OR of
these two encoded streams is transmitted. Nonlinear turbo codes that provide a
controlled distribution of ones and zeros are used to demonstrate a
low-complexity scheme that operates close to the optimal boundary.
