Research On Networking Protocols In Underwater Wireless Sensor Neworks

With the wide application in both civilian and military domains, wireless sensor network (WSN) has been highly focused on in the world. Furthermore, along with the urgent requirement for exploring wide ocean area and the constant growing developments of military defense and business exploiture, underwater acoustic wireless sensor network (UAWSN) based on WSN is also being concerned and expected to play a very important role in future underwater monitoring system. Therefore, UAWSN are becoming those research topics with great significances.As known, an efficient design of network topology and communication protocol is very important for UAWSN. Besides that, long transmission delay, serious multi-path reflection and Doppler frequency spread are also very serious in the underwater acoustic channel. These problems prevent many techniques used in the land wireless sensor network transplanting into UAWSN directly. So the UAWSN confronts several challenges such as balanced energy consumption, network topology and energy efficient communication protocol.Based on above discussion, this thesis addresses those problems relative to the network organization. First of all, theoretical researches are developed on the network topology, and the topology model of balanced energy consumption is also designed. After that, deep researches on the routing and MAC protocols of UAWSN are developed and designed to be able to avoid long transmission delay and heavy energy consumption. Finally, sufficient simulations are made and experimental results demonstrate the better performance and feasibility of those proposed protocols.Main works in this thesis fall into following aspects:(1) Network topology and energy consumption analysis. By the usage of energy consumption model for the underwater acoustic channel, the energy consumption of node on multi-hop path, the advantage of underwater clustered network and the optimal number of cluster head for energy consumption are analyzed in detail, which become the theoretical basis for the next research on the selection of network topology.(2) Propose adaptive clustering algorithm in underwater multi-hop sensor network. By using the network analysis model and the underwater energy consumption model, an efficient balanced energy consumption strategy (BECS) is proposed based on the geometrical programming theory. BECS makes use of the distance vector and node energy level to adaptively dynamically change the probability for a node becoming the cluster head, and enables the cluster head to adaptively determine its managing radii. As expected, BECS balances the network burden very well and prolongs the life time of network.(3) Propose routing algorithm based on the forward cluster head and forward gateway in the UAWSN. A routing protocol based on the forward cluster head and forward gateway is proposed to solve the long delay and heavy energy consumption problems in acoustic transmission.(4) Propose energy efficient MAC protocol in the acoustic network. An energy efficient MAC protocol based on the real-time delay estimation is proposed to overcome the problems such as long delay, synchronization difficulty and uncertain variation in the UAWSN.The research of this thesis optimized the topology of the underwater sensor networks to certain extend, especially, propose feasible communication protocol for the UAWSN, it can expedite the ocean explore and research.