Degrees of freedom of wireless X networks

We study the degrees of freedom characterization of wireless X networks, i.e. networks of M distributed single antenna transmitters and N distributed single antenna receivers where every transmitter has an independent message to every receiver. We provide an outerbound on the capacity region of X networks within o(log(SNR)). If the channel co-efficients are time-varying/frequency selective, we show that the total number of degrees of freedom is equal to MN/M+N-1 using a coding scheme based on the idea of interference alignment.