Poster Abstract: Enabling Concurrent Random Access in Underwater Acoustic Networks

Uncoordinated random-access protocols are especially suitable for underwater acoustic networks with long propagation delays due to their simplicity. However, their performance is limited by severe collisions caused by uncoordinated access, and the current modulations cannot handle the collisions under the multipath environment. In this paper, we propose a new modulation and a new demodulation algorithm to resolve collisions. In particular, we adopt a Zadoff-Chu (ZC) sequence with cyclic shifts as the modulation, and assign users with different ZC sequences to minimize inter-user interference. To combat the multipath challenge, we leverage the insight that the multipath interference pattern is almost constant within the same packet and the modulated data only shifts the pattern, and develop a pattern-based demodulation algorithm. Trace-driven simulation results show that our new approach allows at least five users, and outperforms the existing approach by at least 8dB. In the future, we intend to develop a real-time system in a realistic environment.