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Dynamic block-cycling over a linear network in underwater acoustic channels

The underwater acoustic (UWA) environment is known to have large spatial and temporal variations. In this paper, we propose a dynamic cooperative relaying protocol, termed dynamic block-cycling (DBC) protocol, for a UWA linear network. Considering large channel variations, we assume one node can hear from not only its direct but also several remote neighbors. A transmission package with multiple blocks is taken as one relay unit, where an erasure-correction code and an error-correction code are used for inter-block encoding and intra-block encoding, respectively. During the relaying process, each node in the proposed protocol starts relaying immediately after it decodes the relayed message, hence a reduced end-to-end transmission latency can be achieved. Meanwhile, to avoid the overhead for relay cooperation, the relays' transmissions are cyclically synchronized, such that in each time slot, the blocks arriving at the downstream receiving nodes from all the upstream transmitting nodes have the same block index. Numerical results showthat for a one-shot transmission, the proposed protocol achieves a reduced end-to-end delay relative to existing protocols while maintaining a decent outage performance.