Reliable Cross-Layer Protocol Design for Carrier-Sense-Based Underwater Acoustic Networks

This thesis investigates the application of carrier-sense (CS)-based underwater acoustic networking for reliable multi-hop communication with per-hop acknowledgements (ACKs), aiming to maximise end-to-end data delivery. In particular, the work focuses on the JANUS digital communication standard to ensure seamless integration into existing underwater infrastructure.

Starting from JANUS’s medium access control (MAC) protocol, marked by strong collision avoidance but high scheduling delays, a novel protocol is introduced: JANUS-Accelerated with Slotted CSMA ACKs (JASCA), which unlike JANUS, handles ACKs explicitly using a dedicated fast-transmission mechanism.

Following that, this thesis also introduces the Multi-User Packed Acknowledgements (MUPACK) automatic repeat request protocol. MUPACK supports selective, multi-destination burst delivery with bundled ACKs.

Together, these contributions implement new CS-based reliability mechanisms that remain fully JANUS-compliant while significantly improving throughput, latency, and delivery success rates. The proposed network stack has been validated through extensive simulation across varied scenarios. This work advances JANUS from a minimal signalling protocol to a practical foundation for full-featured underwater networking and provides a clear path for deploying robust CS-based solutions.