The Analysis Of Outdoor Wireless Communication System Based On The LED Visible Light

LED technology has been already widely applied for the past few years and thewireless communication technology based on visible light LED has been improved day byday. Owing to its innate characteristic such as power saving, long operating life, excellentvibration resistance and response speed etc, LED is widely used as indicator light, signallight, display screen and landscape lighting etc which can be seen everywhere. As theprogress of the manufacturing process and the development of new material of LED, theultra-high light brightness (UHB) LED with all sorts of colors has achieved a breakthrough,making LED to be the fourth generation light source gradually. As a semiconductor device,LED has a faster conversion rate of electricity to light in addition to the general lightingfunction. Applying this property, modulate the lighting light by flashing pulse lightintensity modulation which isn’t perceptive by the human eyes, the purpose ofcommunication in addition to the traditional lighting and display function is achieved.In the basis mentioned above, the wireless visible light communication technologybased on outdoor LED traffic light is proposed in this paper. This outdoor wirelesscommunication system is achieved without increasing the relatively complicatedequipment and has the advantage of low cost, convenient and efficient, dispensing withchanging the existing equipments etc, having a broad prospect of research anddevelopment in the future.The main research content of this paper is wireless communication technology basedon outdoor LED traffic light. Beginning with the basic working principle of the LEDtraffic light communication, the advantages and the feasibility of wireless visible lightcommunication technology based on outdoor LED traffic light is discussed in detail. Thenthe mathematical model is built for the further quantitative research of system performanceby researching the physical model of outdoor LED traffic light communication andmeasuring the parameters in practical situations. Meanwhile, the effect of acceptance angleon the working range of system is also analyzed quantitatively.Due to the outdoor communication channel’s complexity, the outdoor wireless light communication is affected by the background light, environment light, light absorption andlight scattering etc. So the channel model of outdoor LED traffic light communication isalso researched in this paper and a fading model of the air channel close to the ground onthe power of light carrier in the system communication is proposed, furthermore, thesimulation works have been already done on the fading coefficients under the fogcondition, rainy condition and snowy condition respectively. On this basis, the concept ofworking range in which the system can achieve the task of normal communication isintroduced in this paper. By adopting the intensity modulation and OOK modulation, thesystem performance and communication quality in working range under fog condition,rainy condition and snowy condition are simulated respectively. The working range andcorresponding communication performance metrics are provided by analyzing SNR andBER when transmitter is LED traffic lights and the transmission channel is the air which isclose to the ground.By analyzing the effect of the acceptance angle to the working range of system, theconclusion that by increasing the acceptance angle, the working range can be broadened isdrawn. We can also draw the conclusion from the simulation experiments that in thecondition of the same distance and LED light intensity, the system performance is betterwhen the red LED traffic light is adopted in the outdoor wireless visible lightcommunication rather than the green ones. What’s more, the working range of red LEDtraffic light communication system is also greater than the green ones and the differencecan reach10meters above.