Research On Low-complexity Precoding Algorithm In Massive MIMO Systems

The research of this thesis is supported by the National Natural Science Foundation of China"Research on low complexity key algorithms in massive MIMO systems"(No.61571108).In massive multiple input multiple output(MIMO)systems,the number of transmitting antennas at base station(BS)is very large.With the increase of transmitting antennas,the computational complexity of linear precoding algorithm increases rapidly and the performance is worse.Based on regularized zero force(RZF)precoding algorithm,the thesis proposes two low-complexity precoding algorithms.The thesis proposes a RZF precoding algorithm based on Conjugate Gradient(CG-RZF)and accelerates the iteration speed by optimizing initial value and using preconditioner.The simulation results show that CG-RZF precoding algorithm has lower complexity and two-iteration CG-RZF precoding algorithm has lower bit error rate.Then the thesis proposes a RZF precoding algorithm based on Chebyshev iteration(Chebyshev-RZF)and optimizes its initial value to reduce more complexity.The simulation results show that Chebyshev-RZF precoding algorithm has lowest complexity compared with algorithms mentioned in references.With the same initial value and performance,the complexity of Chebyshev-RZF precoding algorithm is lower than that of Newton-RZF precoding algorithm.This algorithm has been published in the IEEE ACCESS.The main contents of the thesis are as follows.Chapter 1 introduces the research background,research status and main research work and chapter arrangement of the thesis.Chapter 2 analyses the massive MIMO channel model and the precoding algorithms in MIMO system,including non-linear precoding algorithm,linear precoding algorithm and low-complexity linear precoding algorithm and gives their corresponding precoding matrices.Chapter 3 proposes a CG-RZF precoding algorithm and optimizes its initial value and iterative speed.Then the thesis gives the computational complexity of CG-RZF precoding algorithm under different iteration times.Finally,the thesis compares the CG-RZF precoding algorithm with the algorithms in Chapter 2 in bit error rate.Chapter 4 proposes a Cheby shev-RZF precoding algorithm and optimizes its initial value.Then the thesis gives the computational complexity of Chebyshev-RZF precoding algorithm under different iteration times.Finally,we compare the Chebyshev-RZF precoding algorithm,CG-RZF precoding algorithm and algorithms in Chapter 2.Chapter 5 summarizes the research result of this thesis and prospects the future work.