Amplify-and-Forward MIMO Y Channel: Power Allocation Based Signal Space Alignment

In this paper, we propose a power allocation based signal space alignment for analog network coding (SSA-ANC) scheme for the MIMO Y channel with amplify-and-forward (AF) strategy. The specific SSA- ANC scheme to achieve the maximum degrees is discussed first, with an emphasize on the design of the precoding vectors. Then, we propose a suboptimal algorithm called OMAC to optimize the power allocation at three users aiming at maximizing the sum rate of the MIMO Y system with zero-forcing (ZF) receiver. It is shown that the proposed power allocation algorithm is a convex optimization problem and therefore a global optimal solution can be obtained. Numerical results show that the OMAC algorithm can achieve improvement in sum rate performance compared to the non-optimization case.