Multiuser underwater acoustic communication using cyclic shift keying

A novel code division multiple access (CDMA) using cyclic shift keying (CSK) signaling, namely CSK-CDMA, has been proposed for multiuser underwater acoustic communication. The proposed method uses the cyclic correlation characteristic of spread spectrum signals and time reversal processing to increase the data rate each user and to reduce the complexity of the receiver. In CSK-CDMA system, multiple bits information is represented by the cyclically shifted version of the basic spread spectrum waveform at the transmitter. Therefore, the CSK scheme provides a higher data rate than conventional direct sequence spread spectrum. At the receiver, the peak position of the cyclic correlator output is estimated to recovery information. Multiuser communications are demonstrated with lake experimental recorded data. The data rate is 40 bits/s/user for 4 users with zeros error bits and 20 bits/s/user for 8 users with BER around 10-2 at low signal-to-noise ratio (-3 dB), given 4kHz bandwidth, respectively.