The Study Of Mixed Excitation Linear Prediction Of Speech Coding

Recently, with the development of broadband communication, it seems that the band is not a serious problem any more. But in wireless communication field, band is always a kind of rare resource. Especially in military and secret communication, any improvement in speech coding may enhance the system's performance rapidly.Speech Coding is of great importance in digital communication systems. When transmission rate is limited strictly, Very Low Bit Rate Speech Coding (LBRSC) is especially significant. Now many new Speech Coding techniques appear, and diversified schemes of Speech Coding inosculate to each other and learn from each other. As a important algorithm of LBRSC MELP can work at the rate of 2.4kb/s has been chosen as U. S. Federal Standard, MELP algorithm is on the basis of Linear Prediction (LP). Five auxiliary characters has been introduced into MELP algorithm, they are mixed excitation, aperiodic pulse, Fourier series, pulse dispersion and adaptive spectral enhancement filtering. There are other two merits of MELP algorithm, the lower operating complexity and the adaptive ability in serious noise environment which make it can be easily transplanted into DSP system. So the MELP algorithm has a great future.In this paper several LBRSC algorithms is studied, and MELP algorithm has been considered to be the greater algorithm at 2.4kb/s. On this condition, the theory of the MELP algorithm is deeply investigated, including the procedure of coding and decoding. With the increase requirement of the speech quality for the communication system, an improved MELP scheme is given which can improve the speech quality. The new MELP scheme has a great future in the field of communication system.