A Reliable Transfer File Protocol for Multi-hop Underwater Acoustic Networks

This work addresses reliable data transfer in underwater acoustic networks. We develop a protocol based on the Trivial File Transfer Protocol (TFTP) [1], a UDP-based file transfer protocol. First, we present the Underwater Trivial File Transfer Protocol (UW-TFTP), a variant specifically adapted for underwater acoustic environments. Building upon this, we introduce an optimized version, UW-TFTP-Buffer (UW-TFTPB), which introduces an out-of-order packet buffer at the receiver side. This enhancement improves resilience to packet loss while preserving the original Go-Back-N strategy to avoid the complexity of packet reordering on the transmitter side. We compare the performance of both versions in a multi-hop scenario, using emulated acoustic modems, in terms of the time required for successful file transfer under increasing packet error rates, thus demonstrating the effectiveness of our optimized approach in challenging underwater communication conditions. Finally, we evaluate the two protocols in a end-to-end scenario with two actual low-cost acoustic modems in a small water volume.