Research On Sub-optimal Signal Detection Algorithm In MIMO-OFDM Power Line Communication System

In recent years, with the expansion of the scale of smart grid, in order to ensure the safety and reliability of power transmission, power grid scheduling needs to strictly monitor the power generation, transmission and distribution links, power line carrier communication came into being. Among them, Multi-Input Multi-Output Power Line Communication (MIMO) system can improve the system spectrum efficiency and transmission rate without increasing the bandwidth. However, due to the system in the signal transmission when there is a serious interference, to explore the effective signal detection algorithm to restore the signal sent to become a need to overcome the problem.Although the detection performance of maximum likelihood detection is the best, the computational complexity is high, which is not conducive to fast decoding. In this paper,the sub-optimal signal detection algorithm with low complexity in MIMO-PLC is studied,and the detection performance of these algorithms is analyzed by simulation.Firstly, this paper describes the fading characteristics and noise characteristics of the channel in detail for the MIMO-PLC system, and briefly summarizes the ZF (Zero Forcing)and minimum mean square error (MMSE) in the sub-optimal signal detection algorithm ),And proposes an extended MMSE detection algorithm, which lays the foundation for the detection algorithm based on lattice reduction based on the fusion MMSE criterion.Secondly, according to the advantage that the base vector in the channel matrix can be as short as possible and almost orthogonal, so as to improve the channel transmission characteristic. This paper presents the LLL-LR QR-ZF based on Householder transform in MIMO-PLC system Detection algorithm. The algorithm is orthogonal to the base vector in the channel passing matrix based on the Householder transformation. Secondly, the channel matrix is reduced according to the LLL constraint to realize the base vector as short as possible and almost orthogonal. The estimated value of the transmitted signal is then formed by the successive interference cancellation (SIC) method according to the sufficient statistics induced by the QR decomposition. The LLL algorithm based on Householder transform constructs the integer transformation matrix according to the upper triangular matrix R, and transforms each column vector in the matrix one by one. It is not affected by other vectors, so it has higher stability than LLL reduction The The simulation results show that the error rate of LLL-LR QR-ZF detection algorithm based on Householder transform is lower than that of ZF detection algorithm.Then, the multi-path for the environment makes the MIMO channel a problem of frequency selective fading channel. In this paper, a new method based on segment LLL lattice reduction in multi-input multi-input orthogonal frequency division multiplexing(OFDM) (MMSE-SIC, Minimum Mean Square Error-Successive Interference Cancellation)signal detection algorithm for S-LLL (Segment-LLL). The algorithm first divides the channel passing matrix into a certain number of sub-matrix blocks. Secondly, according to the LLL constraint and the adjacent inter-block exchange condition induced by this, the length reduction and the exchange reduction are completed quickly, Orthogonal length is the shortest. Finally, the QR decomposition and continuous interference cancellation method based on the MMSE criterion are used to obtain the approximate global estimate of the transmitted signal. The simulation results show that the error rate of MMSE-SIC based on S-LLL lattice reduction is lower than that of LLL-LR QR-ZF detection based on Householder transform.Finally, in order to further optimize the performance of the reduction and achieve the optimal order, and further reduce the bit error rate of the system, this paper presents a MIMO-OFDM system based on complex KZ grid reduction (CKZ-LR, Complex Korkine Zolotareff-Lattice (MMSE-PSQRD) is the Minimum Mean Square Error (MMSE)algorithm. Firstly, the complex LLL algorithm and the enumeration algorithm are used to iterate the base vector of the channel passing matrix to be orthogonal and the length is shorter. Then, by optimizing the order of rows and columns of the block matrix of the unitary matrix Q induced according to the MMSE criterion, the optimal ordering is realized iteratively based on the minimum norm criterion, and the approximate optimal global estimate of the transmitted signal is obtained. The CKZ reduction of the channel passing matrix can produce a lattice which is more orthogonal to the LLL reduction. At the same time, the number of iterations can be reduced by calling the enumeration algorithm to improve the computational efficiency. The simulation results show that the error rate of MMSE-PSQRD signal detection algorithm based on CKZ-LR is lower than MMSE-SIC signal detection algorithm based on packet LLL-LR.