Abstract
In mmWave massive MIMO systems, traditional digital precoding is difficult to be implemented because of the high cost and energy consumption of RF chains. Fortunately, the hybrid precoding which combines digital precoding and analog precoding not only solves this problem successfully, but also improves the performance of the system effectively. However, due to the constant mode constraint introduced by the phase shifter in the analog domain, it is difficult to solve the hybrid precoding directly. There is a solution which divides the total optimization problem into two stages to solve, that is, first fix the digital precoding matrix, solve the analog precoding matrix, and then optimize the digital precoding matrix according to the obtained analog precoding matrix. In this paper, a high energy-efficient hybrid precoding scheme is proposed for the subconnection structure. In the first stage, the optimization problem can be decomposed into a series of subproblems by means of the independent submatrix structure of the analog precoding matrix. When the optimized analog precoding matrix is obtained, the digital precoding matrix can be solved by the minimum mean error (MMSE). Finally, the digital precoding matrix is normalized to satisfy the constraint conditions. The simulation results demonstrate that the performance of the proposed algorithm is close to that of fully digital precoding based on subconnection structure and better than that of the existing algorithms. In addition, this paper presents the simulation analysis of the algorithm performance under imperfect channel state information. Simulation results show that when the estimation accuracy of channel state information is 0.8, the spectral efficiency of the proposed algorithm can already be maintained at a good level.
Highlights
With the rapid development of technology, the fifth generation mobile communication (5G) has attracted wide attention due to higher frequency, greater network capacity, and lower latency
The performance of the proposed algorithm is simulated and compared with the hybrid precoding algorithm based on continuous interference cancellation in [11] and the HPD-PS algorithm in [13]
We mainly focus on the hybrid precoding of millimeter-wave large-scale multiple-input multiple-output (MIMO) systems based on subconnection structures
Summary
With the rapid development of technology, the fifth generation mobile communication (5G) has attracted wide attention due to higher frequency, greater network capacity, and lower latency. In view of the hybrid precoding problem of energy-saving subconnection structure, a hybrid precoding scheme based on successive interference cancellation (SIC) is proposed in [11] It does not require singular value decomposition and matrix inversion, and the computational complexity is much lower than traditional sparse reconstruction precoding algorithms. A new subconnection structure is introduced in [14] to further reduce the power consumption of the system According to this structure, an efficient hybrid precoding scheme based on service quality constraint is proposed. Some scholars have gradually focused on the energy-saving and more practical subconnection structure, far, achieved some results, but the performance of the hybrid precoding algorithm and the complexity of the algorithm still need to be further improved. Notation: in this paper, A, a, and a denote a matrix, a vector, and a scalar, respectively; ðAÞT , ðAÞH, and kAkF are the transpose, conjugate transpose, and Frobenius norm of A, respectively; A−1 and A†represent the inverse and MoorePenrose pseudo inverse of A; TrðAÞ indicates the trace of matrix A; det ðAÞ expresses the determinant of A; diag ðAÞ is the diagonal version of A; absðAÞ is the element-wise absolute value of A; A⊘B is the Hadamard division between Aand B; CN ð0, σ2Þ is a complex Gaussian vector with mean 0 and covariance σ2; Eð⋅Þdenotes the expectation; Cm×ndenotes an m × ndimensional complex space; RðaÞis the real part of a
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