Research On Modulation And Demodulation Techniques Of Optical Commuication Based On LED

Nowadays, the outdoor positioning technology based on the global positioning system is quite sophisticated. Because of the application of this technology, the development and research of indoor positioning technology has been stimulated. As the popularity of smart phones, most people rely more on smart mobile devices. However, the satellite signal is very weak and even cannot be received in indoor facilities, the need for a new technology that don’t rely on satellite signals to achieve indoor positioning is urgent.For indoor positioning technologies such as Wi-Fi, ZigBee, RFID, UWB, Bluetooth, and wireless, there are critical problems: resource consumption, low precision, system implementation complexity and hardly can be used in a wide range of large areas. Wireless optical communication technology is viewed as the hybrid achievement of optical communication technology and radio frequency wireless communication technology. It provided infinite and alternative spectrum to the limited radio frequency resources and given clever remedies to the short board of traditional wireless communication. Optical communication is convenient, low radiation and anti-interference, which has attracted more and more attention at home or abroad and is expected to become one of the most important directions of the future research in the field of wireless communications.The indoor positioning system based on wireless light communication technology was mainly researched and the implement of Android mobile app client to build a set of indoor positioning system prototype was discussed. This system requires no exterior equipment, it only used the phone comes with sensors and realized 1 meter indoor positioning accuracy. Mainly research content of this paper is as follows:First, concerned with the actual indoor environment, the wireless optical communication system channel was analyzed and the whole system framework and workflow was determined.Second, concerned with the LED’s luminous characteristics and positioning accuracy, the simulation analysis of the system performance of the laser energy distribution was discussed, the main layout parameters of the LED light source transmitter was determined and the installation of the LED transmitter was completed.Third, the characteristics of indoor wireless optical communication technology and several conventional optical communication modulations were analyzed, and also referred to the performance of mobile phone receiving end sensors, the appropriate modulation mode was selected. Then to complete LEDs’ light signal modulation, the microprocessor sent a signal to the driving circuit, and experimental platform to complete the preliminary test of optical signal modulation was also built.Fourth, the programing in the Android platform and the design of Android mobile app client which can achieve precise indoor location and display results on the mobile phone screen were studied.Fifth, the research combined the indoor positioning and Baidu API to achieve indoor and outdoor seamless convergence positioning, the entire system was completed and system tests was conducted.The system can achieve 1 meter indoor positioning accuracy for ordinary mobile phone users and the success rate of positioning hardly be influenced by the light environment.The mobile phone app compatibility on Android platform is also good.