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MODELING AND ANALYSIS OF SPATIAL INTER-SYMBOL INTERFERENCE
                   FOR MIMO IMAGE SENSORS BASED VISIBLE LIGHT COMMUNICATION

                                                1
                                                              1
                                                                         2
                                   Rongzhao Wu , Yarong Guo , Jiang Liu , Peng Liu  1
                     1
                      Yangzhong Intelligent Electrical Institute, North China Electric Power University
                                        Yangzhong city, Jiangsu Province, China
                                 2
                                  Faculty of Science and Engineering, Waseda University
                                                 Shinjuku, Tokyo, Japan
                                              Email:liupeng@ncepu.edu.cn



                             ABSTRACT

          In this paper, a MIMO image sensors based visible light com-
          munication system is designed and researched. In our study,
          the spatial inter-symbol interference was considered and the
          formation mechanism of the stray light and the influence of
          the spatial inter-symbol interference is analyzed. The math-
          ematics expression of the system SNR and BER is given. The
          simulation result indicates that there is a critical communi-  d
          cation distance in the system. Once the communication dis-
          tance exceeds the critical value, the system BER increases
          sharply. In addition, an adaptive threshold detection method
                                                                         (a)                    (b)
          is introduced and the performance is simulated. By means of
          estimating the spatial inter-symbol interference noise power,  500
          the optimal detection threshold can be obtained and the sys-
          tem BER performance enhances significantly.           450
          Keywords— Optical wireless communication, Image sensor
                                                               400
          communication, MIMO, spatial inter-symbol interference,
          optimum detection threshold method                   350


                                                               300
                         1. INTRODUCTION
                                                               250              A
          With several advantages such as saving the radio frequency
          resource and being harmless to human being, the visible light  200
          communication (VLC) technology develops rapidly in the
          last decade. Depended on the detection method, the VLC  150
          system can be divided into photodiode (PD) based VLC sys-
                                                                                B
          tem and image sensors based VLC (IS-VLC) system [1]. Due  100
          to the widespread use of image sensors, the IS-VLC tech-
          nology has a promising future in low-speed optical wireless  50             C
          communication, indoor positioning application and intelli-
                                                               0
          gent transportation system [2, 3, 4].                 0   50  100  150  200  250  300  350  400  450  500
          In order to improve the performance, multi-input multi-
          output (MIMO) scheme is utilized in IS-VLC system. Com-                    (c)
          pared with the single-input single-output scheme, MIMO-IS-
                                                             Fig. 1: Demonstration of the SISI. (a) The designed experi-
          VLC system can not only achieve a higher symbol transmis-
                                                             ment board with 6 × 6 LED array and the LED spacing dis-
          sion rate but also a lower bit error rate [5]. In a MIMO-IS-
                                                             tance d. (b) Imaging result of the LED array. (c) Light inten-
          VLC system, a frame of digital data stream drivers the LED
                                                             sity contour plot of (b).
          array where the on status of LEDs represents the data ’1’ and
          off status corresponds to the data ’0’. An image sensor used
          as receiver captures a picture and send it to be processed. By


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