Research On Modulation And Detection Algorithm Of MIMO Visible Light Communication Based On Channel Statistics

With the rapid development of wireless communication technology,the shortage of wireless spectrum resources is becoming more and more obvious.As a new technology of wireless communication,visible light communication has relieved the tension of the radio spectrum in a certain extent.Because of the advantages of environmental safety,simple building as well as no need for radio spectrum certification,visible light communication can be applied to intelligent transportation,intelligent lighting,indoor positioning and many other areas.In recent years,visible light communication technology has earned widely concern and study,and it will certainly act an important role in wireless communication technology in the future.However,due to the non-negative characteristics of optical signals,it is difficult to apply the exciting matured technologies we've gained now to the visible light communication.At present,researches about visible light communication are mostly concentrated in the indoor scene,but few pay attention to the outdoor scene.As outdoor visible light communication is mainly affected by the flow and the attenuation of atmospheric signal path,the light intensity signal is random.What's more,there is no defined mathematical model for signal path.The problems above have seriously cumbered the performance of visible light communication under outdoor scene.In view of this,this paper mainly studies the modulation and detection algorithm of outdoor visible light communication system.Firstly,this paper analyzed the characteristics of the signal path of outdoor visible light communication,the typical model of signal path and the probability density distribution of the final statistical decision quantity system.As for the problems of complication of signal path and multiple influencing factors,here raised a method which improved the existing mean detection algorithm as well as a method for semi-blind detection of unipolar multi-Stage pulse amplitude modulation(PAM)which can modulation signals using maximum likelihood criterion under the scene of extensive MIMO visible light communication system.The simulation results showed that the accuracy of such algorithm is much higher than the traditional mean detection algorithm.It can reduce the average error probability and improve the performance of the system.Secondly,based on the research of the maximum likelihood detection algorithm,further exploration has been done to deduct the expressions of the average constellation error probability.The existing unipolar PAM modulation in interval constellation has been improved and a non-equal-interval joint constellation has been raised to adjust to the characteristics of the outdoor visible light communication channel.Finally,a method of numerical solution is proposed for the suboptimal solution of the optimization problem of the nondeterministic polynomial in this paper.Simulation results showed that by using the optimized modulation constellation can further reduce the average probability of the system constellation error,and it is more obvious for the advantages of the proposed method especially in the case of high SNR or the number of antennas at both ends of the transceiver.