Research And Implementation Of VoIP Terminal Echo Cancellation Method

With the development of communication technology become more integral, digitized, intellectualized and personalized, the traditional telecommunication service represented by PSTN can not meet people’s need. Especially after the appearance of data service, this has huge impact on PSTN. This has urged the production of pronunciation data communication system in computer, which adopts the technique generally called the VoIP (Voice over IP) or the IP telephone. However, VoIP’s call function need data compression codec and network transmission processing will cause delay, to produce echoes when the echo path is greater than 30ms will affect call quality, when the echo path is greater than 50ms basic communication can not continue. The basic principle of the echo canceller is an adaptive filter to model the echo path and thus the echo estimate, subtracting the simulated echo signal from the proximal end in order to achieve the purpose of the echo canceller. The adaptive filter coefficient updating process is the process of adaptive filter model the echo path. At present, the adaptive algorithm LMS algorithm, NLMS algorithm, RLS algorithmFirstly, the LMS algorithm theoretical derivation, then the LMS algorithm and NLMS algorithm, RLS algorithm were analyzed and compared. Due to the VoIP terminal’s echo path is relatively long VoIP terminal to complete the compression of the signal, the codec tasks, network transmission, etc., and the function Once the convergence of the adaptive filter coefficients will be relatively stable. Echo cancellation algorithm to calculate the amount of as small as possible. In summary, the select of LMS algorithm with low computational complexity and speed of convergence in general. Then use LabVIEW platform to simulation algorithm, test results show good performance of echo cancellation LMS algorithm to achieve better echo cancellation.VoIP terminal selection dsPIC33F family of high-performance 16-bit digital signal controller with extended digital signal processor (DSP) functionality and high-performance 16-bit microcontroller (MCU) architecture, a high-performance digital signal controller. Select of Wolfson Microelectronics production of mono codec chip WM8510 voice capture playback. In MAPLAB development environment, the LMS echo cancellation algorithm applied to the echo canceller hardware platform for real-time voice communication, the echo canceller to achieve satisfactory results through debugging, to improve the quality of voice communications.