A novel low bit rate speech secure terminal system based on PSTN line

In this paper, a novel low bit rate speech secure terminal system is designed to meet the strict requirement of very low bit error rate in data communication based on Public Switched Telephone Network (PSTN) line. This system uses the ARM+FPGA architecture, its main purpose is to make a balance between voice quality and coding efficiency is to obtain lower bit error rate and guarantee the quality of speech. In this system, secure mode adopts the AES 128bit algorithm, and audio encode uses WT2000 chip which be used for aviation voice communication, and digital modulation uses CX93011. Finally, experiment results under different complex conditions show that the system is very static and safe and clear voice can be obtained, and the bit error rate of encrypted communication under in most complex PSTN with ADSL is only 5.7*10^-6.