In underwater wireless sensor networks (UWSNs), the sensor nodes are sparsely deployed over a large sea area due to their high design cost and high manufacturing cost. Opportunistic routing protocols are a promising forwarding technique for various UWSNs. However, many opportunistic routing protocols suffer from the void problem in sparse underwater scenarios. Hop count-based opportunistic routing protocols inherently alleviate this problem by periodically maintaining the topological information of sensor node. Nevertheless, the robustness of these protocols degrades due to channel variation and node movement in UWSNs. In this paper, we propose a coding-aware opportunistic routing method for sparse UWSNs (CORS). In CORS, we use topological information to adaptively expand the candidate set. On this basis, a forwarding with opportunistic coding strategy is developed to join interflow network coding and opportunistic forwarding in CORS. In addition, we design a sliding window-based coding algorithm to provide effective coding gains with low coding overhead. Then, a sliding window-based decoding algorithm is designed to reduce decoding overhead. Simulation results show that CORS significantly improves upon the network performances of existing protocols in various scenarios.INDEX TERMS Underwater wireless sensor networks, opportunistic routing, hop count, network coding.
Underwater wireless sensor networks (UWSNs) have emerged as a promising technology to monitor and explore the oceans instead of traditional undersea wireline instruments. Traditional routing protocols are inefficient for UWSNs due to the specific nature of the underwater environment. In contrast, Opportunistic Routing (OR) protocols establish an online route for each transmission, which can well adapt with time-varying underwater channel. Cross-layer design is an effective approach to combine the metrics from different layers to optimize an OR routing in UWSNs. However, typical cross-layer OR routing protocols that are designed for UWSNs suffer from congestion problem at high traffic loads. In this paper, a Cross-Layer-Aided Opportunistic Routing Protocol (CLOR) is proposed to reduce the congestion in multi-hop sparse UWSNs. The CLOR consists of a negotiation phase and transmission phase. In the negotiation phase, the cross-layer information in fuzzy logic is utilized to attain an optimal forwarder node. In the transmission phase, to improve the transmission performance, a burst transmission strategy with network coding is exploited. Finally, we perform simulations of the proposed CLOR protocol in a specific sea region. Simulation results show that CLOR significantly improves the network performances at various traffic rates compared to existing protocols.
Underwater acoustic networks (UWANs) have emerged as a promising technology to accomplish Internet of Underwater Thing (IoUT). Handshake-based protocols have been used in UWANs to resolve various problems for different protocol layers. However, the effectiveness of handshake is seriously influenced by interference as the underwater channel has lower spreading loss factor and absorption attenuation. In this paper, we derive effectiveness of handshake strategy for 3D UWAN and analyse it with various parameters.
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