| The development of marine resources is inseparable from the support of underwater communication networks,but field testing in the marine environment is challenging and costly.Pure network software simulation is low in cost but cannot truly reflect the hardware and channel characteristics,and generally is only suitable for initial research.Hardware-based underwater acoustic network emulation is a more appropriate transitional research method from simulation to field test.In order to improve the reliability and efficiency of hardware emulation testing,the workload of secondary development from software simulation to hardware emulation should be minimized,and the hardware emulation platform is required to provide a functional interface that supports rapid switching from pure software simulation to hardware emulation.Based on the above research background,this thesis designed and developed a software-defined remote underwater acoustic network emulation platform SDR-Uan based on the combination of multi-core underwater acoustic modem hardware and public cloud platform,and based on the platform,the underwater acoustic MAC protocol was designed and verified.The main work of this paper is as follows:(1)This thesis has designed and developed a multi-core underwater acoustic communication node low-level software program based on multi-core open source hardware.Based on the hardware platform of the open source ARM-DSP multi-core processor AM5728,as well as the extended hydroacoustic communication transmitter board and receiver board,this paper implements the simulator protocol process,dual-core data interaction program and transplantation of the DSP underlying communication program in the ARM core and DSP core respectively.It realizes the data receiving and transmitting function of the node in the underwater acoustic channel.(2)This thesis has developed a software-defined remote underwater acoustic network emulation verification platform SDR-Uan.Deploy the expanded NS3 simulator and node management service program on the public cloud platform.The NS3 of the public cloud extension supports the establishment of mapping between virtual nodes and real underwater acoustic modem hardware nodes;while the node management service program manages both virtual and real nodes,and forwards data packets according to the mapping table.Therefore,the entire system completes the exchange of data packets sent and received between the virtual node and the real communication node,thereby realizing the seamless switch from simulation to hardware emulation for NS3 underwater acoustic network research.(3)This thesis proposes an improved MAC protocol for data collection type underwater acoustic network suitable for high traffic load: MACA-EP protocol,and is verified based on the SDR-Uan platform.Compared with the traditional MACA-BI protocol,this protocol has the following three improvements: First,the sending node determines the number of packets to be sent,and the node gets an invitation to send,and can send out multiple packets in the sending queue continuously.The second is to set aside time intervals for broadcasting at intervals of polling time to expand new data source nodes.The third is to introduce a dynamic adjustment mechanism for the polling interval.According to the actual number of received packets,this mechanism dynamically reduces the polling frequency of low-rate nodes in the network,increases the polling frequency of high-rate nodes in the network,and eliminates nodes that have not been able to transmit data for a long time,thereby improving the polling efficiency.The protocol is simulated and tested by the SDR-Uan platform developed in this paper,and compared with the Pure-ALOHA,MACA,and MACA-BI protocols.The results of simulation and emulation test jointly verify that the protocol has a higher traffic volume.The data collection type underwater acoustic network has a good performance,and the emulation test also verifies the feasibility and effectiveness of the SDR-Uan emulation platform system. |
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