An FEC-based Reliable Data Transport Protocol for Underwater Sensor Networks

In this paper, we investigate the reliable data transport problem in underwater sensor networks. Underwater sensor networks are significantly different from terrestrial sensor networks in two aspects: acoustic channels are used for communication and most sensor nodes are mobile due to water current. These distinctions feature underwater sensor networks with low bandwidth capacity, large propagation delay, high error probability, half-duplex channels, and highly dynamic topology, which pose many new challenges for reliable data transport in underwater sensor networks. In this paper, we propose a protocol, called segmented data reliable transport (SDRT), to achieve reliable data transfer in underwater sensor networks. SDRT is essentially a hybrid approach of ARQ and FEC. It adopts efficient erasure codes (so-called SVT codes in this paper), transferring encoded packets block by block and hop by hop. Compared with other existing reliable data transport approaches for underwater networks, SDRT can reduce the total number of transmitted packets, improve channel utilization, and simplify protocol management. In addition, we develop a mathematic model to estimate the expected number of packets actually needed. Based on this model, we can set the block size appropriately for SDRT, as helps to address the node mobility issue. We conduct simulations to evaluate our model and SDRT. The results show that our model can closely predict the number of packets actually needed, and SDRT is energy efficient and can achieve high channel utilization.