Study On Equalization Technology Of LED Indoor Visible Light Communication

With the rapid development of wireless communication technology,he communication rate of equipment is getting higher and higher,the same time,he spectrum resources of wireless communication are becoming increasingly scarce in the process of people’s gradual exploration.As a new access technology,LED-based indoor visible light communication has spectrum resources of 380nm-780 nm,which can solve the problem of the current wireless communication spectrum resource shortage.Therefore,it has become one of the research hotspots in the field of communication.In daily life,a single LED layout has insufficient luminous power and it is difficult to meet the requirements of communication and lighting at the same time.Therefore,a multi-light LED layout is usually required.However,the light power distribution and light level under this layout are very uneven,and the time of light signals of multiple LEDS arriving at the receiving end is quite different due to the complexity of indoor communication environment,which will cause multipath effect and inter-symbol interference.In this paper,the following aspects of this problem are studied:(1)The visible light communication system with classical light source layout is studied.Modeling analysis of the indoor visible light communication system,the classic light source under the layout of the indoor light,optical power distribution,as well as the channel impulse response are simulated,the simulation shows that the light source layout under light and light power distribution can satisfy the basic lighting requirements of ISO regulation,the impact of the channel delay in response to a received the influence of reflected light increases,The reason of code-to-code interference is analyzed.(2)Aiming at the problem that the performance of visible light communication system is degraded due to inter-symbol interference,the method of eliminating ISI is analyzed from principle,and the method of solving ISI caused by multi-path effect by equalization algorithm is introduced.Aiming at the problems of large initial error and unbalanced convergence performance of traditional LMS algorithm,an adaptive equalization algorithm based on brainstorming algorithm is proposed.The results show that the communication performance of the system is greatly improved under this algorithm.(3)A cascade blind equalizer based on orthogonal wavelet transform was proposed to solve the problem of poor noise resistance and poor equalization effect.In this algorithm,a decision guided equalizer is added on the basis of the equalizer of orthogonal wavelet transform.Firstly,the signal is processed by the blind equalizer of orthogonal wavelet transform to filter out the noise components effectively,and then the error of the algorithm is further reduced by the second equalizer.Experimental results show that the bit error rate of the algorithm is effectively reduced.