Design And Analysis Of Visible Light Communication Platform For Body Area Networks

Visible light communication refers to the communication mode that uses visible light band as the information carrier to directly transmit visible light signals in channels such as free space,which has the characteristics of high speed,no electromagnetic interference,rich spectrum and high security.Body area networks equipment can help medical staff to monitor the health status of patients in real time,so as to carry out early detection and diagnosis of diseases,and provide timely medical assistance for patients.In this thesis,the body area networks is combined with visible light communication to realize the monitoring of patient health information,and the factors that affect the transmission of visible light signals in the human body surface channel are analyzed through channel characterization,which is helpful to better understand the human body surface channel under visible light communication,so as to achieve higher quality transmission.The application of visible light communication in body area networks for vital signs information monitoring and channel characterization has strong prospective and research value.The main results of this thesis are as follows:1.A visible light communication platform for body area networks is designed.Firstly,the hardware circuit design of the platform and the program design of the MCU are completed:According to the design of hardware circuit to complete the transmitter and receiver as well as the control chip selection,the LED is the core of the transmitting end,the photodetector is the core of the receiving end,and the control chip realizes the control of the whole platform,and based on three core components to build the hardware circuit design,mainly including power amplification and LED driver circuit,the visible light detection circuit,etc.;According to the program design scheme of MCU to complete the transmitter and receiver program design,which mainly includes communication protocol design,serial port data receiving and transmitting,modulation,demodulation program,etc.And the processing of the transmitting and receiving data are completed.In addition,an optimization scheme is designed to further optimize the heat dissipation and wearability of the system.2.Completed the vital sign information transmission experiment.Under the premise of the same transmission rate and the relative position between the transmitter and the receiver,this thesis uses different modulation modes to carry out multiple groups of experiments,and completes the transmission of ECG signals,EEG signals and heart rate signals with low bit error ratio.By comparing the bit errors ratio of the three vital sign signals transmitted under different modulation modes,it is obtained that the PWM modulation with 75% duty cycle has the lowest bit error,which proves that the platform designed in this thesis can well realize health monitoring.3.A human surface channel transmission feature characteristics scheme based on visible light communication is designed.In this thesis,channel characterization is carried out under the modulation mode determined by the vital sign information transmission experiment.The amplitude,frequency and phase of the received signal are analyzed and processed.The path loss,cumulative distribution function of path loss and energy attenuation of visible light signal are obtained to characterize their transmission characteristics in the static channel on the human body surface.Through the analysis of the above indexes,it is found that the path loss of visible light signal transmitted on the human surface channel is not only related to the center distance between the transmitter and receiver,but also related to the relative Angle of the transmitter and receiver and the position of the body,and the trend of energy attenuation is given.