Permutation-based M-ary chaotic-sequence spread-spectrum communication systems

From the spectrum utilization point of view, an M-ary modulation scheme is sometimes preferred over a binary one because more data can be transmitted in the same bandwidth. In this paper, we propose an M-ary chaotic- sequence spread-spectrum modulation scheme. In this scheme, each block of chaotic sequence produced by a chaotic map undergoes a transformation before it is transmitted. At the receiver, based on the block of chaotic sequence received, the appropriate inverse transformation is performed, and the received symbol is decoded. A permutation-based transformation process is proposed, and a simple method to construct the permutations corresponding to different symbols is also presented. Coherent and noncoherent systems are investigated, and their performances are studied by computer simulations.