We propose two generalized block-diagonalization (BD) schemes for multiple-input multiple-output (MIMO) relay broadcasting\nsystems with no channel state information (CSI) at base station. We first introduce a generalized zero forcing (ZF) scheme that\nreduces the complexity of the traditional BD scheme. Then the optimal power loading matrix for the proposed scheme is analyzed\nand the closed-form solution is derived. Furthermore, an enhanced scheme is proposed by employing the minimum-mean-squared error\n(MMSE) criterion. Simulation results show that the proposed generalized MMSE scheme outperforms the other schemes and\nthe optimal power loading scheme improves the sum-rate performance efficiently.
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