  We investigate the information theoretic limits of two types of
state-dependent models in this dissertation. These models capture a wide range
of wireless communication scenarios where there are interference cognition
among transmitters. Hence, information theoretic studies of these models
provide useful guidelines for designing new interference cancellation schemes
in practical wireless networks. In particular, we first study the two-user
state-dependent Gaussian multiple access channel (MAC) with a helper. Inner and
outer bounds on the capacity region are first derived, which improve the
state-of-the-art bounds given in the literature. Further comparison of these
bounds yields either segments on the capacity region boundary or the full
capacity region by considering various regimes of channel parameters. We then
study the two-user Gaussian state-dependent Z-IC and state-dependent IC. Three
interference regimes are studied, and the capacity region or the sum capacity
boundary is characterized either fully or partially under various channel
parameters. The impact of the correlation between the states on the
cancellation of state and interference as well as the achievability of the
capacity is demonstrated via numerical analysis. Numerical investigation
indicates that for the regular IC, the correlation between states impacts the
achievability of the channel capacity in a different way from that of the Z-IC.
