Research on space division multiple access underwater acoustic communication

Abstract

An underwater acoustic (UWA) channel system is very sensitive to environmental parameters. According to this characteristic of UWA channels, the channel impulse response functions between each user and the master node are quite different in multi-user UWA communication; this means the cross-correlation is weak. A single-element time reversal mirror (STRM) can take advantage of this feature to focus expected users and to shield multiple access interference (MAI) at the same time. A vector sensor can simultaneously measure scalar and vector information for the sound field, and a single vector sensor's active acoustic intensity average (AAIA) can simultaneously measure the multi-user orientation at the same frequency band. Using the measured azimuth information, the vector sensor can be electronically rotated to achieve directional communications, which can further suppress MAI. STRM, together with AAIA, is applied to multiuser UWA communication to achieve space division multiple access (SDMA) UWA communication, which can effectively suppress MAI and increase the UWA communication system's capacity. Moreover, the SDMA technique is simple in structure and easy to achieve in algorithms.