On the Underwater Acoustic Channel Effects on Uplink Multiple Access Techniques

Acoustic communication represents the most reliable technology to transmit data over long range underwater links, but unfortunately data rates performance suffers from the poor available bandwidth, the low speed of sound and the impairments caused by the channel. Such limitations impact not only on physical layer issues, but also when dealing with medium access control. In fact, the access opportunities for users deployed in a cellular-like underwater network are strongly influenced by the channel, as delay spread variability and Doppler can worsen the performance not only in terms of intersymbol interference but also in terms of multi-user interference. In this regard, the following contribution is aimed to investigate the role played by the channel in terms of access opportunities for time, frequency, code - division multiple access, that are the best known channelization based techniques, as well as for random access as ALOHA.