Research On Key Technology Of Multi-mode Adaptive Underwater Wireless Communication Networks

Since the21st century, with the needs of the development of the military and worldeconomy, the marine high-techs such as exploitation and utilization of marineresources hasbecome one of the major fields of the new science and technologyrevolution. Every maritime power around the world is accelerating the research on keytechnology and equipment of underwater wireless communication. The development ofunderwater wireless communication networkis significant to the establishment ofunderwater wireless early warning system and underwater wireless navigationsystem.According to the requirements of exploitation and utilization of marine, thecommunication system can detectenvironment factors, adaptively adjustcommunication scheme. What is more, the communication system can supply variousways of services: short, middleand long range low-speed real-time communication ofdata and audio, middle range high-speed real-time communication of multimedia andimage data. To meet demands above, this paper research onsome key issues ofmulti-mode adaptive underwater communications network.The detailed contents are as follows：(1) The concept and composition of Multi-mode Adaptive Underwatercommunications network based on software-defined radio is proposed. The physicallayer, link layer and network layer protocols are briefly analyzed. Meanwhile, to meetthe need of security, a security architecture is proposed and briefly analyzed.(2) The characteristic and modeling method of underwater wireless acoustic andoptical channel is proposed. A space-time codes project based on LDPC is proposedfor shallow water and a space-time codes project based on Turbo is proposed for deepwater. To simplify decoding complexity at receiver, a unified adaptive decodingscheme is proposed.(3) According to the need of modulation and demodulation, communication nodefirstly choosesthe type of modulation based on the data quantities and the demand ofbandwidth. Meanwhile, a cross-layer adaptive modulation and demodulationarchitecture combined with the MAC layer protocol,is introduced. The future state ofchannel is anticipated by sender using Markov model. And then the sender adaptivelychooses appropriate modulation scheme and notifies the receiverby handshaking signal.To satisfy the special requirement for resources (eg. power, frequency), the sendercalculatesthe communication distance based on handshaking signal. And then thesender determinesthe optimal resource allocation plan based on Water injectionprinciple and the relationship between distance and SNR. (4) The cluster formation strategy is the core algorithm of underwatercommunications network topology. In order to save energy of node and prolonglifetime of whole network, the cluster-head election algorithm based on the ratio ofresidual energy of nodes and residual energy weighted average of whole cluster isintroduced. A EQE-MAC protocol which is based on time slot is proposed to guaranteethe minimal opportunity of confliction and solve the hidden-end problem. The nodeis allowed to communicate with cluster-head only in the assigned time slot,andin othertime it is in sleep model. It is difficult to synchronize time slot, so aReservation-Monitor-Sleep MAC (RMS-MAC) protocol is studied in this paper.Inorder to guarantee important data can be transmited on time, we adopt adaptive accesscontrol scheme to offer burst communication. In our assumptions, nodes generate alarge number of one-hop clusters. Aiming at the sceneof mobile nodes between clusters,we propose an improved routing algorithm based on VBF. The aim of the wholeprotocol is to save energy and prolong the lifetime of entire network.(5) The platform of underwater wireless communication node which is based onprogrammable logic devices (FPGA,CPLD,ARM) are proposed in this paper.