Design And Optimization Of Large-scale Low-power IoT Backscatter Communication System

Backscatter communication is a low-power communication technology that does not require power supply.It uses common electromagnetic waves in the environment as carrier to send signals,such as WiFi,ZigBee and Bluetooth signals.It can communicate anytime and anywhere.In the field of Internet of Things(IoT)it is widely used.However,most of the existing reflection communication systems are small in scale,cannot be used in ordinary indoor office scenes,and usually have relatively high maintenance costs.This dissertation designs a low-power,large-scale passive IoT communication system based on backscatter communication.The system consists of a transmitter,multiple communication nodes(Tags)and a receiver.Based on the existing optical signal energy acquisition module,a high-frequency signal energy acquisition module is designed for the Tag,which eliminates the need to install batteries for the Tag and reduces the maintenance cost of the node.Compared with other passive communication systems,the communication protocol designed in this dissertation adopts a signal processing method based on the combination of OOK modulation and CDMA coding based on backscatter communication,which increases the node capacity of the system.The main advantages of this system are:(1)A radio frequency signal energy acquisition module is designed on the basis of optical signal energy acquisition.This module can collect radio frequency signal energy and continuously supply voltage to the Tag to ensure that the Tag can work passively;(2)The calculation method of impedance matching network for high frequency signal is improved to reduce the loss of high frequency signal when it enters digital circuit.(3)The combination of OOK modulation and CDMA coding on the basis of backscatter communication increases the number of TAG in the system.In the actual environment,Tag can install sensors and collect environmental information through the sensor.The environmental information is sent out in the way of passive communication.The energy of signal transmission process is obtained from the environmental electromagnetic wave.As a low-power communication system with sustainable development,it can be applied to a variety of IoT communication scenarios such as smart home and intelligent office.