Chaos shift keying spread spectrum with multicarrier modulation for secure digital communications

Combining chaos shift keying (CSK) spread spectrum (SS) system with the multicarrier modulation (MCM) scheme, orthogonal frequency division multiplexing (OFDM), and wavelet-based OFDM is presented in this paper. A chaotic sequence for chaos shift keying (CSK) (that provides auto- and cross-correlation properties that are similar to those of random white noise) is used for spread spectrum systems. Due to its bifurcation behavior depending on the initial condition, the number of chaotic sequences that can be generated by a single formula is not restricted and will not repeat itself. These characteristics provide an increase in system capacity and security performances. On the other hand, multicarrier modulation provides an efficient way to modulate multiple data into multiplexed data streams with the inherent ability to combat impulsive and narrowband noise. However, conventional OFDM multicarrier modulation scheme suffers from peak-to-average power ratio (PAPR) problem. Extensive research on this direction had found that wavelet-based OFDM (WOFDM) can provide a superior spectral containment and a lower PAR that leads to performance gains. This paper presents a comprehensive performance study for chaos shift keying SS-OFDM (CSK-OFDM) and chaos shift keying SS-wavelet OFDM (CSK-WOFDM). Simulation showed that wavelet based multicarrier system will provide a better BER performance