| Although the traditional radio technology has been widely used and the technology is quite mature, the industry and the scientific community access technology for the next generation of wireless communication systems (4G) will be based on the combination of technology for multiple access technology and optical wireless communication technology is Included. The Optical Wireless has many advantages which the radio does not have. First, optical wireless has huge available bandwidth which are not been used, and light waves will not produce electromagnetic interference (EMI). In addition, OW signal does not penetrate walls. This constraints signal in the room so that each room automatically become a communication cell and will be no inter-cell interference. Thus, the communication frequency can be repeated used in the adjacent cells, and each cell can use the same system and equipment. As the transmission need not be adjusted in adjacent rooms, and therefore can be devised by a simple high-capacity wireless LAN. Optical wireless can naturally protect the privacy of communication and be able to prevent eavesdropping, this system has a strong appeal for some industries, for example, be used for military purposes or financial news. In addition, they have broad application prospects in some special environments and scenes, such as hospitals and aircraft where the radio system is prohibited for use. The combined use of the radio and optical wireless will be able to provide a broad spectrum capacity, which if implemented individually by radio is more difficult. Recently with the technical progress in solid-state lighting LED (400-780nm), visible light communications (VLC) research and design have also gotten widespread concern in the world’s research institutions.LED is the key factor in VLC system, LED is the. next generation of green lighting equipment, it is not only low power consumption, long life, small size, green, and you can also use its transmission modulation signal. Current the fastest LED devices modulation bandwidth is about10M, but have to use the modulation if it is used for high-speed data transmission, the current use of orthogonal frequency division multiplexing (OFDM) can reach the maximum transmission rate of500MHz/s, which has reached the limits of the modulation rate, if all the LEDs send the same signals to all users, this rate is far from being able to meet the current high-speed business needs, so the need for VLC space division multiplexing research is urged. Allocation information by a user’s different requests, each LED is only responsible for the current user’s signal transmission, thereby greatly improving the utilization of the LED modulation bandwidth, the technology is based on the communication of the user’s location and therefore must first determine the location of the user, and then notifies the appropriate LED to signal transmission of the user. Therefore, first locate the user is the key to the whole space division multiplexing.In this paper, I’ve proposed a positioning technology based on visible light communication, and validate the superiority of the visible light communication for indoor positioning through simulation and experimental. A super-frame communication slot for indoor positioning method is first made on the basis of the full research of IEEE802.15.7standard. Followed by the establishment of optical power distribution model in the indoor channel, thereby building a database of the location of fingerprint for positioning technology. Propose solutions to optimize the location fingerprint to reduce location time and calculation process. And establish a visible light communication hardware platform for signal transmission and reception through the LED. |
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