  Communication over a multiple access channel is considered. Each user
modulates his signal as a superposition of redundant data streams where
interconnection of data bits can be represented by means of a sparse graph. The
receiver observes a signal resulting from the coupling of the sparse modulation
graphs. Iterative interference cancellation decoding is analyzed. It is proved
that spatial graph coupling allows to achieve the AWGN channel capacity with
equal power transmissions.
