Aligned interference neutralization and the degrees of freedom of the 2×2×2 interference channel with interfering relays

Previous work showed that the 2×2×2 interference channel, i.e., the multihop interference network formed by concatenation of two 2-user interference channels, achieves the min-cut outer bound value of 2 DoF. This work studies the 2×2×2 interference channel with one additional assumption that two relays interfere with each other. It is shown that even in the presence of the interfering links between two relays, the min-cut outer bound of 2 DoF can still be achieved for almost all values of channel coefficients, for both fixed or time-varying channel coefficients. The achievable scheme relies on the idea of aligned interference neutralization as well as exploiting memory at source and relay nodes.

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