R&D On Local Wireless Digital Audio Broadcasting And Interactive Terminal Based On WIFI

At present, the embedded system technology is developing rapidly, and the integration ofembedded technology and network technology is the inevitable trend of the development.Wireless network technology has good flexibility, convenient construction, low cost andmany other advantages, which makes the wireless network technology has been more andmore popular. Digital audio communication can overcome many disadvantages of thetraditional analog audio communication, which leads that the audio transmission has strongeranti-interference ability, better real-time performance, and more desirable voice quality.IP-based voice communication technology can effectively use the existing cyber source,and can greatly reduce communication cost. So we can see that the real-time communicationof wireless digital audio by using the embedded technology and wireless network technologyis of great researching value.This project combines the embedded technology, the wireless network communicationtechnology and the multimedia technology together. The goal is to design an embedded audioterminal working in WIFI LAN environment. The terminal has the wireless network settingfunction, digital audio broadcasting function, digital audio interactive function, audio savingfunction and audio playback function. At the same time, we must ensure good sound qualityby using some certain advanced audio processing technologies. The terminal can be used inspeech teaching and some other short-distance communication applications. According to thedesign target, I made a system design scheme through detailed needs analysis, and conducteda comprehensive demonstration and feasibility analysis of the project. By reading a lot ofscientific literature, I mastered the key technologies involved in project design, which laysthe foundation for the success of the project.This paper mainly introduces three aspects: the hardware circuit design, the WIFInetwork environment formation and the software design of the system. In terms ofhardware, the system uses ARM embedded processor as the hardware core. The periphery ofthe system is equipped with audio codec circuit, SD card storage circuit, LED display andkeyboard control circuit, etc. Both the circuit schematic and the PCB board are made. In theformation of wireless network environment, we realized fast ad-hoc working model throughthe configuration of WIFI modules. In software aspect, we use the embedded Linux OS as thesoftware platform. The project mainly includes the development environment setting up, thedesign and transplant of hardware drivers, the realization of all functions on the application layer. We use the DSP programming under Linux to realize the audio collection and play, anduse the UDP protocol to realize the audio broadcasting. We use the Streaming mediatransmission protocol to realize the audio interactive communication, and we adopt theJRTPLIB library to achieve the RTP communication. Moreover, in order to ensure the clearand smooth speech quality, this system adopts the powerful Speex speech engine toaccomplish the noise suppression and the Echo cancellation. And the silence detectiontechnology of Speex is also used to filter the silent parts so as to save the audio storage space.Through the study of these key technologies, and also by using the Linux thread technologyto achieve the integration of all the functional modules, finally I finished the design work ofthe project.Through the system integration, debugging and testing, this design has achieved all thefunctions successfully. The performance of the system has reached the expected effect. Theswitching between each working mode is simple and smooth. And the system is stable andreliable, and the voice quality is also guaranteed. The expected goals of the subject design aresuccessfully achieved.