| With the development of mobile communication, people's life style is changed. More people love thee small, portable, powerful communication equipment gradually. This promotes the development of wireless communication technology. With the high speed of communication and information technology in today, voice communication is still the basic and important information interchange style. But in voice transmission the band width means cost and the compressed voice signal can save band width and improve the efficiency of transmission, so it is important to compress the voice signal in voice transfer.Speex codec is developed into open-source software based on the code-excited linear prediction algorithm. It aims mainly at the voice communication wireless network. It's designed for providing high quality and low bit-rate voice encoding. So it fits for the wireless voice transmission system very much.This thesis is to design a wireless voice transmission system and apply the speex codec into this system. According to the need of wireless voice system, this thesis proposed the design idea and implementation program of wireless voice transimission system; and also select the chip according to the needs of the project. In many types of micro-controllers, we select the STM32F103xx series with ultra-low power; we select the audio processing chip W681310 with high performance, low power, less peripheral devices. We select A7102 transceiver special designed for 433MHz ISM band. The schematic and pcb are designed. And the drivers of voice chip and RF chip are designed.Then this paper introduced the advantage of Speex codec, analysised the basic principle of CELP coding algorithm, mainly analysised the narrow-band and wide-band sub-mode encoding principle of Speex.At last, according to the principle of TDD, this paper designed and implemented a wireless voice transmission system based on TDD mode, and also verified the feasibility of Speex codec in this system. |
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