Research On High-performance Receiving Technology Of High-speed Visible Light Communication System

Visible light communication systems have attracted more and more attention due to their rich spectrum resources,good security,high transmission rate,and environmental protection.The visible light communication system uses visible light for data modulation,which can provide illumination and communication services at the same time without being interfered by the wireless network,it is an effective supplement to wireless communication.Efficient signal detection methods are of great significance for improving the transmission rate of the system and making full use of power resources and bandwidth resources.Among them,the sphere decoding algorithm and the expected propagation algorithm are two detection algorithms with superior performance in modern communication.This paper takes the performance and complexity into account,further research on these two algorithms are studied in the visible light communication system,the main research contents include:Firstly,the problem of adaptive signal detection in MIMO-VLC system is studied.For the research of sphere decoding detection algorithm,an adaptive sphere decoding detection algorithm that can automatically adjust the search radius according to the result of the previous iteration is proposed,which improves detection efficiency and effectively reduces the complexity of the algorithm;on this basis,according to the characteristic that the visible light channel response will rapidly decrease with the increase of frequency within a limited bandwidth,a detection scheme based on channel differentiation is given,which can select the corresponding detection algorithm according to the different modulation methods on different frequency bands,Research indicates that the scheme can realize the good match between the algorithm and the channel.Secondly,the high-efficiency and high-performance detection problem based on the expected propagation algorithm in the MIMO-VLC system is studied.The expected propagation detection algorithm is optimized: use the last iteration information to terminate the iteration reasonably,which can avoid useless calculations and speed up the iteration process;combined with the characteristics of different channel conditions,use different iteration times for different signals to reduce the number of active nodes in a single iteration;the radius adaptive compression method is used to reduce the range of the constellation points that should be calculated,which can reduce the amount of exponential calculations.Research indicates that,compared with the traditional expectation propagation detection algorithm,the proposed high-efficiency expectation propagation detection algorithm after joint optimization has similar detection performance,lower computational complexity and higher detection efficiency.Thirdly,the problem of robust signal detection under non-ideal channel conditions in MIMO-VLC systems is studied.Considering the scenario where channel estimation error and channel space correlation problems exist at the same time,a expected propagation detection method which joint with channel estimation and lattice reduction is proposed.The algorithm effectively utilizes the channel estimation error information in the detection process,uses the lattice reduction algorithm to effectively improve the channel conditions,and redefines the set of all integer points within a certain radius of the detection signal as the constellation which solves the problem of determining the constellation caused by the lattice reduction algorithm.Simulation results indicate that the detector can show good robustness in non-ideal environments.