Application of Improved Chaotic Code in a Multi-User Coded Hybrid Spread Spectrum System under Frequency Selective Fading Channel

Abstract

Spread spectrum techniques can be considered one of the main solutions to design a reliable and secure communication system. However, due to the developments of applications and huge increase of the demanded users, its applicable spreading codes become not sufficient to full fill all the security and applications requirements. As an alternative solution, a hybrid spread spectrum with application of specific codes appeared to solve most problems of the traditional spreading codes. Recently, many researches focused on the chaotic codes, due to its attractive security properties, in addition to its availability to generate a huge number of spreading codes. In this paper, the performance of a multiuser coded hybrid spread spectrum system is presented and evaluated under frequency selective fading channel. The system is constructed from conventional coding technique with Viterbi decoder, and three different types of spread spectrum technique using improved chaotic codes. The mathematical model is presented, and a performance evaluation and comparison is performed between different types of improved chaotic codes and the Gold code as spreading codes in the DSSS. The results show that, in the case of the multiuser , the improved chaotic codes give better performance than the Gold code.