Research Of Basic Proteocls In Spatial-temporal Varying Underwater Acoustic Sensor Networks

Underwater acoustic sensor network(referred to as UASN) is a distributed self-organized underwater monitoring network, which formed by low-cost sensor nodes that have the low energy consumption, underwater acoustic communications and computing power, deployed to the designated area. UASN can be widely used in the exploration of marine resources, marine information monitoring, underwater target tracking and positioning, and other civilian and military areas. It has extensive application value and research value, and gradually becomes one of the hotspots in information science research domain.We analyze the influence of the underwater acoustic channel properties on the underwater acoustic sensor network performance. Then we study three issues of the basic network protocols: data link layer protocol, time synchronization mechanisms and network architecture. We design scalable, universal new delay tolerant network architecture for underwater mobile sensor network, propose a medium access control protocol (MAC) and a time synchronization algorithm for underwater sensor networks in order to adapt the characteristics of spatial and temporal variability, high error rate and high latency. The specific research and contributions are as follows:1. Investigate the problem of limited and heterogeneous communication in underwater mobile sensor network. Analyze the capacity of the proposed network architectures, indicate that due to the versatility is poor, and do not apply to underwater mobile sensor network. Further, we study the typical application scenarios and basic characteristics of underwater mobile sensor network. We propose scalable universal underwater mobile sensor network architecture. Finally we point out the key research issues of underwater mobile sensor network protocols.2. Analyze the cube-based underwater acoustic sensor network topology; investigate the effect of three different communication modes in data transmission direction and delay. Study the relationship between nodes coordinates and data transmission. Under the foundation of the unit circle interference model, we derive the function between node coordinates and slot distribution. We propose a centralized MAC protocol for three-dimensional cube-based underwater acoustic sensor network: USS-TDMA. USS-TDMA algorithm uses the collision avoidance mechanism, manages the time slots allocated by the base station and keeps the whole network synchronous through broadcast synchronization message to whole network. It can greatly improve the utilization of underwater acoustic channel and reduce the delay.3. Investigate the nature of the nodes slot allocation rules in TDMA algorithm, propose an energy effiency distributed TDMA algorithm for UASN: UD-TDMA. UD-TDMA algorithm transforms the solution of the number of concurrent communication node into solving the theoretical issues of maximal independent set. It designs a distributed algorithm to obtain a maximal independent set of concurrent node and to determine the node slot distribution and the transmission cycle. UD-TDMA algorithm has a time complexity of O (n), where n is the maximum degree of two hop neighbor node sets. The theoretical analysis and simulation tests show that the UD-TDMA is feasibility and effectiveness, is validated the performance and efficiency.4. Directed towards dynamic changes of data transmission delay caused by underwater nodes mobility, research the impact of nodes mobility on underwater sensor network data propagation delay, establish the model of relationship between propagation delay and nodes mobility, propose an energy efficienct distributed time synchronization algorithm: E2DTS. By solving the time difference of adjacent receive/transmit packets, E2DTS use linear regression methods to estimate the clock skew and offset so as to reduce the influence of various factors on the time synchronization accuracy in the process of data exchange. Simulation experiments show that compared with existing algorithms, E2DTS has the lower energy consumption and better accuracy of at least 30% higher than others. This research work is an exploration in spatial-temporal varying underwater acoustic sensor networks. Several practical solutions are designed directed towards the characteristics of underwater acoustic sensor networks and have some theoretical and practical value.