Hybrid precoding is an effective solution to reduce the cost of millimeter wave systems. In recent years, joint optimization has begun to attract the attention of researchers due to its excellent performance. In this letter, we adopt the alternating optimization method to design a low complexity hybrid precoding. In particular, the spectral efficiency optimization problems are simplified to sub-optimization problems under certain constraints. For each sub-optimization problem, we alternatively optimize the columns of the analog precoding matrix and combining matrix by using the projected gradient method. Then, the digital domain matrices are derived from the equivalent channel. Simulation results and complexity analyses show that the performance of the proposed hybrid precoding based on alternating optimization is close to the unconstrained optimal precoder and the algorithm has lower complexity.

中文翻译：

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毫米波 MIMO 系统中基于交替优化的低复杂度混合预编码

混合预编码是降低毫米波系统成本的有效解决方案。近年来，联合优化因其优异的性能开始受到研究人员的关注。在这封信中，我们采用交替优化方法来设计一种低复杂度的混合预编码。特别地，频谱效率优化问题在一定约束下被简化为子优化问题。对于每个子优化问题，我们通过投影梯度法交替优化模拟预编码矩阵和组合矩阵的列。然后，从等效信道导出数字域矩阵。