Cancelling known interference in multiple access channels

We study two generalizations of the writing on dirty paper problem. The first scenario is the cross interference multiple access channel, where each user knows the interference that accompanies the transmission of the other user. In the second scenario we consider a two-user multiple access chancel with a common interference known to both transmitters. For the first scenario, we provide new inner and outer bounds for the capacity region. While the capacity region for the second problem was previously known, we provide a constructive coding scheme which attains it.