Based On The Dsp Real-time Speech Codec Secret Communication System Design

This paper designs a speech secure communication system, this system uses TMS320VC5509A made from TI as core. This system can achieve the speech signal coding and encryption processing. In other words the system can save bandwidth by coding the speech signal, also can guarantee the safety of the speech information by encrypting the speech signal. On the other hand, this system also can realize voice recording or playback and processing the recorded speech signal. This system can be applied to the real-time voice communication like mobile contact and non-real-time voice communication like telephone recording.In order to ensure the basic functions of the system, the software design mainly achieved two algorithms, the speech compression to code algorithm G.729A and encryption algorithm. G.729A speech coding algorithm can ensure the date transported in the way which is able to achieve a low algorithm delay, high compression ratio and high speech quality. The encryption method based on Lorenz equations is used so as to ensure a large enough key space and improve the secrecy of the speech communication.According to the requirements of the system functions, the hardware design of the system uses the DSP as the core. According to the program and data memory space requirements of the codec and encryption required, choose the right DSP chips and peripheral circuit chips to design the hardware system modules and interface design. The hardware of the system uses TMS320VC5509A as the core, includeing three modules:DSP minimum system module, audio codec modules, asynchronous serial communication module.Ensure all the functional modules are configured correctly. Based on CCS3.3development environment, use parallel EMIF-boot mode to write the bootstrap program in to the TMS320VC5509A. In this way, the system can achieve the offline operation. After the corresponding test and simulation, the system proved to be feasible.