Design And Implementation Of Acoustic Near Field Communication System Based On Multitrack Spatial Multiplexing

With the widespread popularity of smart mobile devices,the demand for near-field offline communication is increasing.The existing near-field communication technology cannot meet the short-distance and convenient transmission scenarios of small data,low power consumption,low cost,and weak hardware dependence in the offline state.,Such as the high cost of NFC hardware and complex Bluetooth connection.So there is an urgent need for a near field communication technology to solve the transmission problem of this type of scene.At this time,acoustic near-field communication stands out for its convenience,weak hardware dependence,no network dependence,and low power consumption and low price.However,due to the slow transmission rate of acoustic wave communication and the more susceptible to distortion caused by environmental interference,the main research goal of this article is to achieve a high data transmission rate and reliable acoustic near field communication system.Based on the development background of acoustic wave communication,wireless communication and near-field communication and the current research status at home and abroad,this paper finds that Multiple-Input Multiple-Output Spatial Multiplexing and Orthogonal Frequency Division Multiplexing technology can be used to improve the transmission rate and reliability of terrestrial acoustic near field communication.After a lot of experiments,find that when the spectrum resources are the same,the use of Multitrack Spatial Multiplexing technology can double the channel capacity,and solve the problem of the limited transmission speed of terrestrial acoustic communication;the use of Orthogonal Frequency Division Multiplexing technology can reduce the influence of multipath fading,Doppler Shift and noise interference on acoustic signals,achieving high-reliability terrestrial acoustic communication.Taking into account the high penetration rate of Android smartphones,the freedom of development environment,and the greater market value of application development,this article decided to design and implement an acoustic near field communication system client based on Multitrack Spatial Multiplexing and OFDM under the Android platform,and carried out detailed demand analysis and design,and carried out a comprehensive plan for system functions and non-functional characteristics.Then,on the basis of requirement analysis and detailed design,this article develops the system according to the MVC development framework.It mainly focuses on the three modules of audio communication client module,acoustic communication data processing module and dual-channel audio transceiver module to elaborate on the specific realization of the basic functions of the system,and uses data flow diagrams,class diagrams and timing diagrams to parse comprehensively processing procedures and functions classes.Among them,the audio communication client module is responsible for the front-end development of the system's Android client and the realization of front-end interaction;the acoustic communication data processing module is responsible for the encoding,modulation and encapsulation of valid file data,real-time unpacking of recorded audio data,and dualchannel transmission and reception of audio data.Coding and modulation are mainly implemented by OFDM and Multitrack Spatial Multiplexing technology,encapsulation is based on a custom physical layer data unit audio frame structure;the key technology of unpacking lies in the realization of channel estimation and equalization algorithms;the dualchannel audio transceiver is responsible for enabling the audio I/O device to send and receive dual-channel PCM audio bare stream.Finally,after completing the integrated development of the system client,in a typical office environment,use smartphones whose operating system is at least Android 8.0 to execute varieties of acoustic near field communication system tests with multiple control variables,verifying that the system is capable of function and performance from many aspects and meet user's needs and business logic requirements.The effective data transmission speed and reliability of the acoustic near field communication system based on Multitrack Spatial Multiplexing are doubled higher than that of mono acoustic communication,and the android client has good human-computer interaction.