Perception System Based On Ultrasonic's Doppler Effect On Smartphones

Smartphones play an increasingly important role in people's daily life.The ability to play and record sounds on mobile phones is also more powerful.Mobile phones on the market have generally been able to receive and analyze sound signals in the ultra-sonic band.Audio devices on mobile phones have been used not only for traditional applications such as music playback,but have also begun to send and receive ultrasonic waves to achieve environment perception,devices positioning and other services.Ul-trasound has excellent physical properties and related applications are easy to develop.So ultrasound related mobile phone application is known as a hot spot in the field of mobile computing recently.The main content of this dissertation is to build a kind of perception system us-ing the application of ultrasonic mobile phones for ultrasonic distance measurement and data transmission module,and implements a set of feasible solutions named AIS(Acoustic Interactive System).AIS system realizes three user behaviors and sound an-chor recognition in a lab environment.After an experimental test,the AIS system can achieve a false positive rate of 3.33%and a false positive rate of 5%.This dissertation first introduces the research status of ultrasonic smartphone ap-plications at home and abroad,and then introduces the related knowledge of ultrasound required by AIS system.According to the requirements of specific application scenar-ios,the design ideas of the AIS system and the detailed description of the constituent modules are introduced.After that,it introduces the specific implementation of AIS system and improvements to the system on two specific issues.Finally,the experimen-tal analysis of AIS verifies the effectiveness of our system.The main innovations and contributions of this article are:(1)We design and implement an perception system based on the ultrasonic Doppler effect of smartphone.The AIS system exploits the Doppler shift effect of ultrasonic waves to measure the speed of the mobile phone holder and calculate the distance change from the relative sound source by integration.The unique sound source is de-termined in conjunction with the data transmission of ultrasonic providing an indoor localization service for users.Experiments show that the AIS system can effectively identify different user behavior scenarios.At the same time,the AIS system has high scalability,and its ultrasonic transmission and reception equipment are all commercial spot and the installation cost is very low.(2)We combine distributed frequency-modulated continuous wave technology with ultrasonic data transmission technology to construct a scene recognition and data trans-mission module.Distributed frequency-modulated continuous wave technology mea-sures the relative movement distance between the sound source and the equipment by transmitting a continuous chirp signal.AIS system uses this method to construct a scene recognition module.At the same time,the chirp signal is encoded and a data transmis-sion module is constructed.(3)We propose a new method for distinguishing effective bands based on super-imposed chirp signals.In order to increase the density of deployed ultrasonic speakers,AIS system separates the adjacent signal transmitters into different frequency bands.In the frequency band selection,the scheme for detecting the sound field strength is not satisfactory due to limitations of equipment and environmental factors.For this rea-son,AIS determines the validity of the frequency band by detecting the superimposed chirp signal,and this scheme has better robustness.