On the Capacity and Generalized Degrees of 
Freedom of the X channelChiachi Huang, Viveck R. Cadambe, and Syed A. Jafar 
Electrical Engineering and Computer Science 
University of California Irvine 
Irvine, California, USA 
Email:fchiachih, vcadambe, syedg@uci.edu 
Abstract 
We explore the capacity and generalized degrees of freedom of the two-user Gaussian X channel, i.e. a 
generalization of the two-user interference channel where there is an independent message from each transmitter to 
each receiver. There are three main results in this talk. 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.