Research On Indoor Wireless Communication Technology Based On Ultrasonic

The rise of acoustic communication is mainly in the field of hydroacoustic in the military field,while the development of acoustic communication in the air is far less mature than underwater.With the enrichment of application scenarios,acoustic communication technology begins to develop into the civil field.Acoustic communication has become a new choice for new demands such as no Wifi indoors,weak Wifi environment,strong electromagnetic interference and covert communication.At the same time,wireless communication technologies such as Wifi depend on corresponding hardware,which virtually increases the cost of the equipment.In order to realize the low-cost acoustic communication technology witnout Wifi,this paper uses ultrasound as the carrier to build a communication system that can be used in the indoor environment of office buildings.The hardware equipment used in the system is low-cost and low-energy-consumption,which is more advantageous in application convenience and market promotion.At the same time,because ultrasound cannot be heard by human ears,it will not affect people’s normal life,and avoid the risk of eavesdropping.The paper starts from the research on the indoor communication environment and channel characteristics of airborne ultrasonic,combined with the characteristics of ultrasound,simulates the channel environment in the corridor,analyzes the time delay and reflection path of ultrasonic communication channel,studies various communication modes,and analyzes the characteristics of acoustic attenuation,multipath,Doppler,etc.,for follow-up research Lay the foundation.To further understand the ultrasonic frequency response characteristics of ultrasonic transmitter and MEMS microphone(as a receiver),we study low-cost indoor ultrasonic communication hardware devices.According to the wide beam transmission signal requirements(near omnidirectional radiation)of ultrasonic indoor broadcast communication,the structure of the transmitter is designed and optimized to reduce the beam directivity of the transmitter to meet the requirements of omnidirectional radiation in the half space in the office.Finally,based on the low-cost ultrasonic communication system,the ultrasound wireless communication was tested in the office and the long and narrow corridors outside the office.According to different communication requirements,the modulation method is changed,and the reliability of the current communication system is analyzed through the key performance index of bit error rate.The test results show that: in the office environment,The coverage space of the communication system can reach more than 10 meters(coverage diameter),so that multiple devices in the office can communicate normally.Spread spectrum and QPSK with time domain equalization technology is applied,which can ensure the accurate and error-free transmission of the information of each station in the office.Moreover,it is found that the FSK communication system can only support the requirements of stations near the transmitter.In the long and narrow corridor environment,the effective distance of communication under FSK modulation mode is up to 20 m,the effective distance under QPSK mode is 40 m,spread-spectrum communication method can reach up to 45 m,In the case of low signal-to-noise ratio,the spread spectrum modulation method is the best choice for long-distance communication in the corridor.The experimental results in this thesis provide positive support for future indoor ultrasound communication applications,and have broad prospects and strong competitiveness in the field of wireless communication technologies.