Research On Key Technologies For Wireless Sensor Networks In Monitoring Applications

Wireless Sensor Networks (WSNs) provide a new paradigm for sensing and gathering information from various environments. They are the important technology infrastructure of future ubiquitous computing. With the mature technology and market promotion, WSNs will be used in many and diverse applications. One of the most important applications is monitoring. Taking the battlefield surveillance as the main background, the dissertation lays the theory and technology foundation for establishing WSNs-based battlefield surveillance system, on the basis of the systematical research on traffic distribution, load balancing, online data gathering, topology control, mobile data gathering and security of wireless sensor networks.The primary contributions of this dissertation include:1. The influence of topology structure on data transmission in WSNs is researched from the microscopic scale. The definition of load density of any node in many-to-one discrete network space and the distributed algorithm of load density are proposed. With load density, the load distribution of wireless sensor networks can be described accurately in discrete space. Then, the difference in energy consumption speed of sensor nodes can be estimated. A load sub-balancing condition is present. The load balancing of most nodes can be realized by this condition. An adaptive deployment algorithm for multiple sinks is proposed. The whole sensor network can be divided equably with it.2. A low latency and energy efficient online routing algorithm (ODMLR) is proposed. The algorithm combined the virtue of shortest path routing and maximum residual energy strategy. Each node selects optimal routing strategy dynamically according to its residual energy and situation in topology structure. ODMLR is a distributed and localized algorithm, which selecting next hop node only using local information. ODMLR can effectively extends the network lifetime and produces a small network latency, even if the network topology varies dynamically, without knowledge of future query arrivals and data sources.3. A new topology-aware heuristic algorithm on minimum connected dominating sets (MCDS), TACDS is proposed in this dissertation and which correctness is proved. A new concept of forwarding factor is present, which can describe the importance of nodes to the network topology accurately. By taking advantage of the topology characteristic of nodes, the algorithm can reduce the blindness in the process of selecting dominating nodes, and form a smaller CDS based on 2-hop local information, consequently obtain a virtue backbone network with the CDS. The simulation results show that the algorithm is prior to other distributed CDS algorithms, and more close to minimum CDS. 4. An adaptive movement strategy for mobile sinks in wireless sensor networks is proposed. Mobile sinks can traverse the sensor network in a timely and efficient way by it. Based on TACDS algorithm, the sensor network can determine the sink's sojourn points autonomously. By using a genetic algorithm, the sinks can get the optimal data gathering tour, reduce the delay and inefficiency resulted by uncontrolled sink mobility, while ensure the complete coverage for the network. The mechanism can easily extend to multiple mobile sinks to reduce the data latency greatly and provide a higher data delivery ratio. A hybrid computing paradigm based data gathering mechanism in distributed autonomy sensor networks is presented.5. A least privilege mutual authentication key agreement protocol is present for wireless sensor networks using a mobile entity. A session key is created in the process of mutual authentication. The protocol provides mutual authentication and secure data transmission between the mobile entity and target nodes, and can tolerate the mobile entity and sensor nodes compromises. The mobile entity and target nodes can be authenticated each other, only need to receive a message from the other side. Based on the principle of least privilege, the base station only grants the mobile entities the least privilege required to accomplish their tasks. The protocol secures the integrity of data gathering tasks by one-way hash function.