  We explore the capacity and generalized degrees of freedom of the two-user
Gaussian X channel, i.e. a generalization of the 2 user interference channel
where there is an independent message from each transmitter to each receiver.
There are three main results in this paper. First, we characterize the sum
capacity of the deterministic X channel model under a symmetric setting.
Second, we characterize the generalized degrees of freedom of the Gaussian X
channel under a similar symmetric model. Third, we extend the noisy
interference capacity characterization previously obtained for the interference
channel to the X channel. Specifically, we show that the X channel associated
with noisy (very weak) interference channel has the same sum capacity as the
noisy interference channel.
