Research On Nodes Coordination Related Issues Of Wireless Sensor And Actor Networks

In Wireless sensor and actor networks (WSANs), coordination mechanisms are required among sensors and actors to observe on physical world and perform appropriate actions upon the environment. So new networking phenomena called sensor-actor (SA) and actor-actor (AA) coordination may occur. In fact, SA and AA coordination are inseparable, and producing series of problem including service discovery, task assignment, and coverage optimization etl. These requires finishing the job of reporting and handling events, and guarantee real-time, coverage and service quality of networks at the same time. So current research in WSANs face a serious challenge.Facing node coordination of WSANs, aiming at service discovery, task assignment, and coverage optimization of actor, relevant theories and algorithms are carried out in this thesis. The main contributions of this work are as follows:1. This part research on service discovery of SA coordination, analyzing requirements and two typical scheme of this problem, introducing some existing algorithm. A multi-center addressing service discovery algorithm based on hexagon partition (MASD) is presented for random topology, With the comprehensive consideration of the communication cost and per-node storage load, a multi-centre addressing scheme which uses no global computation is designed. Sensor node can find the next hop to the nearby actor through address or local searching. Analyzing algorithm through the experiment, the algorithm has shorter search distance and more little communication cost compared to the imesh algorithm.2. Aiming at single event task assignment problem in WSANs, A Market-Based distributed directional simple auction aggregation protocol (DSAAP) is presented, which uses constructing response tree to assign tasks. This protocol screens the next-hop child node and restricts the retransmission to reduce the message transmission during auction. Through simulated experiments, the results show that the protocol has lower communication cost compared to the SAAP without performance loss in optimal node found. Combining DSAAP and MASD has improved the efficiency of service discovery.3.Coverage recovery problem brought by actor node failure is analyzed, and be proved NP-hard. Then a searching mobile fault-tolerant recovery algorithm based on dichotomy coding (SMR)is proposed to be the approximate solution. Dichotomy coding and counts is reference for actor reposition to make more sensors to be covered. Simulation and analysis results show that compared with the typical algorithms, SMR algorithm achieve the best coverage, and both nodes moving distance and load balancing are well.All of the work has partly solved the coordination problem in WSANs, so the efficiency and life of network can be improved further.