The underwater wireless sensor networks integrating the techniques of wireless sensor networks and underwater robots presents a good idea for overcoming the difficulties in such applications as underwater monitoring and exploring, marine navigation. However, the limitations of underwater acoustic communication make it unpractical to employ some research results directly from terrestrial wireless sensor networks, which bring more challenges for the research of UWSN. Supported by the key project of NSFC (National Science Foundation of China), this paper focuses on four important problems including node design, time synchronization method, media access control, and system integration of an UWSN experimental platform. And the research work are introduced in detail as below. 1. An underwater low cost low power sensor node is designed and realized, which presents a solution for the realization of UWSN physical layer. The node integrates the functions of underwater acoustic communication, ranging among the nodes and underwater environments sensing. And, the node also has excellent performances, such as efficient power utilization, good scalability, and real-time responses for urgent events. 2. A time synchronization method based on loop-convergence is presented for underwater acoustic communication with long propagation delay and low data rate. In the proposed method, several main kinds of time delay in underwater acoustic communication are compensated firstly to decrease the synchronization errors between the nodes, and then a loop-convergence strategy is designed to decrease the cumulate errors caused by multi-hop transmission. 3. the traditional TDMA Media Access Control in UWSN has been proved to be a feasible solution with such weaknesses as low channel utilization, bad scalability. So an improved TDMA MAC is presented based on template matching, which gives a solution for UWSN link layer. In the MAC design, the factors affecting round trip time are analyzed and discussed, and coloring theory is employed to estimate the size of time frame. All these analyses are helpful to improve the channel utilization and the network througthput. Considering the underwater sensor nodes` limited resources, a template matching method is designed to fulfill the channel reassignment process, and it also decreases the channel collisions of the intersection nodes. 4. An UWSN platform is developed, which has a framework with three layers: an underwater network, a transmissio...
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