Modified 24 kb/s ADPCM System

Abstract

This paper presents new modified 24 kb/s Adaptive Differential Pulse Code Modulation (ADPCM) system. The modified ADPCM uses 4-bit quantizer with sampling rate of 6,000 sample/s, while, the standard ADPCM uses 3-bit quantizer with sampling rate of 8,000 sample/s. The purpose of this modification is to reduce the nonlinear distortion introduced by ADPCM when QAM signal is sent over it. The performances of standard and modified ADPCM are studied using QAM signal at data rate of 9.6 kb/s. The simulation results show that the performance of modified ADPCM is better than standard ADPCM.