Chaotic Composite Spread Spectrum Sequence Based PAPR Suppression for Underwater Acoustic MC-CDMA Communication System

As a combination of orthogonal frequency division multiplexing (OFDM) and code division multiple access (CDMA) modulation technology, underwater acoustic multi carrier code division multiple access (MC-CDMA) communication system also has the problem of high peak-to-average power ratio (PAPR). In this paper, a method of PAPR suppression for underwater acoustic MC-CDMA communication system based on chaotic composite spread spectrum sequence is proposed. Chaotic composite spread spectrum sequence is generated by combining chaotic sequence and spread spectrum sequence. First, chaotic sequence is generated according to the number of subcarriers. Then chaotic composite spread spectrum sequence is generated by cyclic multiplication of chaotic sequence and spread spectrum sequence. Spread spectrum sequence adopts M sequence, Walsh sequence and complete complementary sequence, respectively. The simulation results show that the chaotic composite spread spectrum sequence has better PAPR suppression ability in different degrees than the original spread spectrum sequence. In the case of 32 chips, chaotic composite spread spectrum sequence achieves 5 ~ 6 dB PAPR suppression performance gain.