Study On Secure Communication Based On LED

White LED has a high electro-optical conversion efficiency, energy saving, reliable, long life, high-speed modulation characteristics, is recognized as the next generation of green lighting products. White LED compared to traditional incandescent and fluorescent obvious advantages in terms of energy savings, while others use white LED high-speed, broadband optical wireless access provides a new way, but also to alleviate the current serious shortage of radio spectrum resources problem and provides a new solution.Indoor visible light communication is an emerging wireless communication technology, which is based on white LED emitted compared to conventional radio frequency to communicate with indoor visible light communication confidentiality, no electromagnetic interference, do not take the radio spectrum. Meanwhile, the technology can be used in lighting white LED, light it emitted without any harm to the human eye, and indoor infrared communication is the use of infrared technology, which is damaging to the human eye. Lighting is currently widely used in incandescent low photoelectric conversion efficiency, high power consumption, easily broken. Phosphors used in fluorescent emissions harmful to the environment and produce can cause pollution, and the use of a shorter life span. HPS commonly used in urban, high power consumption and low luminous efficiency and lighting effect is not very good, so the white LED is very suitable next generation of lighting alternatives.In the information society, people demand and reliance on the information is getting higher and higher, but in certain situations due to electromagnetic interference is very sensitive, it cannot achieve seamless coverage information, such as in some areas of the hospital, in order to prevent electromagnetic interference on the patient’s health hazards is prohibited radio communications. On the plane, in order not to make personal phone signal communication signal interference is not caused by aircraft using conventional radio communication, so in a lot of a particular environment, we cannot use the traditional means of wireless communication. This is also the intention of our development based white LED indoor visible light communication, this technology is not to replace the traditional wireless communication technology, but in many specific situations cannot be achieved radio communication functions, the technology is and traditional radio communications people together to achieve a fast, simple, and provide a means of real-time communication.This paper focuses on the visible light communication based LED were studied. First of all visible light communication system model is introduced, and then the LED visible light communication key technologies were studied last OFDM applications in the visible communication to do a detailed study. Main work and innovations are as follows:1) Introduces LED visible light communication system based on principle. Which the system is the key part of the LED for a detailed description, including the principle of LED, LED conversion efficiency and modulation principle of the LED. In the analysis of the visible channel, we have a variety of channels and channel topology model transport model were studied and compared.2) Visible on the key system implementation techniques to improve system performance. Covers a series of key technologies from the sender to the receiver, including the LED drive circuit design, LED modulation bandwidth expansion, improve signal transmission rate of advanced modulation techniques, MIMO channel interference and visible light communication technology based on spread spectrum technology. Which focuses on visible light communication channel jamming technology based on spread spectrum technology and a detailed study, which spread and other technology in the visible light communication system is its use of the new extension, which improve system interference tolerance, other system security and even resistance to light interference, etc. has an important role.As we know, OFDM (Orthogonal Frequency Division Multiplexing) can provide almost the highest spectral efficiency with the same bit rate, and it can also improve anti-jamming capability. So the project is mainly to implement OFDM in VLC, in order to improve the transmission efficiency and anti-jamming capability of VLC system.