Practical private speech communication system with chaos using digital signal processor.

Abstract

In this paper, we propose a practical system for private communications with chaos using digital signal processor (DSP). Recently, many analog circuits for private communications with chaos have been proposed. The core technique of this method is based on the strict parameter matching between the transmitter and the receiver system. However, it seems difficult, at least practically in analog circuits, to match the transmitter parameters with the receiver parameters for a long time. Therefore, we try to use the DSP for modulation and demodulation systems by assuming the digital transmission line such as computer networks. Today the DSP has calculation performance over 10 MIPS, therefore, almost all the calculation processes for modulation and demodulation can be performed in real time in audio frequency range. We investigate the round-off error problem peculiar to the fixed point DSP with finite bit length variables, and then propose a new algorithm that can overcome this problem to achieve perfect information recovery characteristics using the 16-bits fixed point DSP.