Degrees of freedom of a class of non-layered two unicast wireless networks

Previous work showed that the fully connected layered 2^L interference channel, i.e., the multihop interference network formed by concatenation of L - 1 2-user interference channels, achieves the min-cut outer bound value of 2 DoF. In this paper, we study the effects of non-layered cross-layer links on the fully connected layered 2^L networks. In particular, we consider the 2⁴ interference channel with arbitrary cross-layer connectivity. We show that the min-cut outer bound value of 2 DoF can be always achieved (almost surely) except if there is a direct link from a source to its interfering destination. In this case, the DoF collapse to 1.