Delay-oriented reliable communication and coordination in wireless sensor-actuator networks.

摘要

Wireless sensor-actuator networks, or WSANs, greatly enhance the existing wireless sensor network architecture by introducing powerful and mobile actuators. These actuators are expected to work with the sensor nodes and perform much richer application-specific actions. For the applications which request for fast and accurate report of the environmental events, an efficient and reliable communication/coordination scheme is urged. Unfortunately, multi-hop communication in a WSAN is inherently unreliable due to frequent sensor failures and network partitions. Excessive delays, introduced by congestion or in-network data aggregation, further aggravate the problem.;In this thesis, we propose a general reliability-centric framework for event reporting in WSANs. We point out that the reliability in such a real-time system depends not only on the accuracy, but also the importance and freshness of the reported data. Our proposed design thus integrates three key modules, (1) an efficient and fault-tolerant event data aggregation algorithm, (2) a delay-aware data transmission protocol, and (3) an adaptive actuator allocation algorithm for unevenly distributed events. We further propose a latency-oriented fault tolerant data transport protocol (LOFT) and a power-controlled real-time data transport protocol (POWER-SPEED) for WSANs. LOFT balances the workload of sensors by checking their queue utilization and handles node/link failures by an adaptive replication algorithm. POWER-SPEED transmits packets in an energy-efficient manner while maintaining soft real-time packet transport. We evaluate our framework and the two proposed protocols through extensive simulations, and the results demonstrate that they achieve the desirable reliability for WSANs.;To minimize the data collection time, we propose a new routing design. We present the mathematical formulation of the route design problem, and show that it is computationally intractable. We then propose two practical algorithms to reduce the delay of the sensors. Our algorithms adaptively adjust the actuator visiting frequencies to the sensors according to their relative weights and data generation patterns. We further propose a probabilistic route design (PROUD) algorithm which adapts to network dynamics. We present the distributed implementation for PROUD and an extension which accommodates actuators with variable speeds. We also propose algorithms for load balancing among the actuators. Simulation results show that our algorithms can effectively reduce the overall data collection time. They adapt to the network dynamics and balances the energy consumption of the actuators.;Finally, we present a novel algorithm for intruder detection in a sinkhole attack of wireless sensor network. The algorithm can identify the intruder and deal with multiple malicious nodes effectively. We have evaluated the performance of the proposed algorithm through both numerical analysis and simulations, which confirmed the effectiveness and accuracy of our algorithm.