In underwater wireless sensor networks (UWSN), acoustic communication naturally introduces challenges such as long\npropagation delay and high packet loss. The flooding-based routing protocol can address these challenges with its multipath\ncharacteristics. As in flooding-based routing, due to multipath propagation mechanism, not only DATA but also ACK messages\nare transmitted through multiple routes however still some packet loss will degrade the performance. So, to provide high\nreliability of message delivery, an efficient retransmission mechanism is inevitable. Though, if the network uses conventional\ntransport layer protocol such as TCP, it will suffer a spurious retransmission problem as TCP was originally not designed for the\nmultipath environment. In this paper, we propose route discrimination for flooding-based routing to reduce spurious\nretransmission in UWSN to solve the limitation. The notion of ACK copies waiting time (ACWT) is utilized which is selectively\nupdated based on the similarity of paths of transmission of ACK message copies. We also improved our previous solution that\nlacks flexibility to cope with dynamic link error characteristics. Through evaluation, we verified that our new scheme achieves\nthe performance improvements of 14%~84% in terms of retransmission ratio compared to the previous research.
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