| Underwater acoustic Multi-chain network has the characteristics of long propagation distance and wide monitoring range due to its relay and forwarding mechanism,so it has been widely studied in Marine disaster warning,military defense and other fields.Due to the unfair transmission and low reliability of the relay forwarding method,in one cycle,the data packets sent by the nodes far away from the sinks have less chance to be delivered to the sink than the nodes close to the sinks,that is,the transmission is unfair,and the reliability is low because of the high probability of packet loss due to multiple relays.Therefore,whether the transmission scheme of underwater acoustic MC network is fair and reliable is related to whether the sinks node can fully grasp the real-time information of each node in the network.However,the design of the transmission scheme for underwater communication faces challenges such as long propagation delay,narrow bandwidth,and high error rate,which are significantly different from the design of transmission schemes for land-based communication.Moreover,the design of transmission schemes is highly dependent on the network topology and application scenarios.All these problems pose challenges for designing data transmission schemes with fairness and reliability in MC networks.To address the fairness and reliability of the transmission scheme for underwater MC networks,this paper proposes the following works:(1)A MC-MAC protocol based on space-division multiplexing time-division multiple access is designed.First,MC-MAC designs a time slot scheduling strategy that meets transmission fairness and has short group delivery delay for networks with different node densities and scales.This paper proposes a quantified fairness formula and the minimum number of transmissions required for each node to achieve fairness,which can guide the time slot allocation of the MC-MAC protocol to ensure transmission fairness.Then,this paper proposes an algorithm for maximizing the time slot reuse rate of the MC-MAC protocol.MC-MAC analyzes the compatibility of node transmissions and obtains the node compatibility relationship diagram.By searching the compatibility relationship diagram,all maximum compatible transmission node cliques can be obtained.Finally,the scheduling problem of time slots is modeled as a conflict relationship cargo packing problem,and the minimum time slot usage is solved to obtain the optimal time slot scheduling strategy.Comparisons with ALOHA and TDMA protocols under different node densities and network scales show that MCMAC outperforms the other two protocols in terms of fairness,throughput,and group delivery delay.(2)A transmission scheme that combines multipath routing and network coding is proposed to improve the end-to-end data delivery reliability of MC-MAC,which does not require retransmission,feedback,or redundant data packet transmission.First,this scheme uses idle nodes in high node density MC networks for packet copying to increase the routing paths.Secondly,each chain is modeled as a directed graph,where the edges between nodes represent the connectivity between nodes.By performing a depth-first search on the above directed graph,all possible data packet routing paths are obtained.This scheme also provides a probability calculation algorithm for each node in the multipath routing transmission mechanism to successfully deliver data packets to the sinks node.Then,using the data packet increment brought by multipath routing,a network coding transmission scheme with distributed source symbols is designed for the MC network to further improve the end-to-end delivery reliability without introducing additional data packet transmissions.Finally,comparisons with ALOHA and TDMA protocols under different network densities,scales,and channel success probabilities show that the combined multipath routing and network coding transmission scheme of MC-MAC is more reliable than the ALOHA and TDMA. |
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