Research On Lattice Reduction Aided Signal Detection Algorithm Of Underwater Visible Light Imaging MIMO

Aiming at the problem of the poor performance of signal detection caused by the strong correlation of underwater visible light MIMO channels,a simulation model of underwater optical imaging MIMO-OFDM system is established,and the related research on the correlation of underwater optical imaging MIMO channels and lattice reduction algorithm is studied.Because of multipath transmission,optical MIMO system obtain diversity gain or multiplexing gain.When the LED array size increases,the spatial correlation of MIMO channels is strong,the superposition of optical signals transmitted by multipaths is inevitable.Therefore,lattice reduction algorithm is performed before the linear signal detection or linear precoding to improve the signal detection performance of the underwater optical MIMO system.To further address the problem that the error of the decision for reduction domain signal makes the system's error performance poor,a joint decision algorithm for multi-path signal on the reduction domain signal is proposed,which improves the accuracy of the signal decision.The main work completed in this paper is summarized as follows:(1)Channel model and correlation research of underwater visible light imaging MIMO system.First,based on the research foundation of the light propagation characteristics under the sea and the Lambertian radiation model,a line-of-sight imaging MIMO channel model for underwater visible light communication is established.Then,the correlation of the channel is studied.Based on the correlation coefficient and the condition number,this paper simulated and analyzed the channel correlation of underwater optical imaging MIMO system.The results show that when the LED spacing and link distance are short,as the system transceiver scale increases,the spatial correlation of the imaging MIMO channel is stronger.(2)Aiming at the problem that the strong correlation of the underwater optical imaging MIMO channel makes the BER of the system high,lattice reduction algorithm is used at the receiving end to reduce the spatial correlation of the MIMO channel.By reducing the lattice basis of the channel matrix before linear signal detection,the correlation of the equivalent channel matrix is reduced,and the inter-signal interference is reduced,thereby the detection performance of the equivalent signal is better.The simulation results show that the correlation of the lattice reduced imaging MIMO channel is weaker than the original channel,and the performance of the linear signal detection which is performed after the lattice reduction is close to the nonlinear signal detection algorithm.(3)Precoding for underwater optical imaging MIMO system based on lattice reduction is studied.The lattice reduction and signal linear transformation are performed at the transmitting end,which reduces the correlation of MIMO channels and equalizes the influence of channel interference,and the linear detection is not needed at the receiving end.Aiming at the problem that the quantization error of the signal of the reduction domain affects the BER performance of the system,a joint decision algorithm for multipath signals of the reduction domain is proposed.The results of simulation prove that the performance of the precoding algorithm based on lattice reduction is better than the traditional linear precoding algorithm,and the optimized decision algorithm can further improve the system's BER performance.