مرکز منطقه ای اطلاع رساني علوم و فناوري - Digital chaotic codec for DS-CDMA communication systems

Abstract :

The potentialities of chaos to secure transmitted messages in digital communications has been proved. This by use Direct Sequence Code Division Multiple Access (DS- CDMA) system using chaotic spreading sequences. Two synchronization methods for Chua s digital chaotic generator, are presented: the master-slave synchronization and the impulsive synchronization. In the first method, the driving signal is continuously transmitted from the driving to the driven system. In the second method, impulses from the driving system are transmitted to the driven one, by means of a time division scheme. A more robust digital chaotic codec is then developed to increase the complexity ofthe chaotic digital signal. The later is based on the general structure Penaud s codec and Frey s modified codec, associated with the technique of dead-beat chaos synchronisation developed by Angeli. Contrary to the others, the proposed codec is suitable to pass-band modulation. Comparison between these methods is achieved. The principle of the secure communication systems and the general chaotic QAM modem are presented.