With the rapid development of the micro-sensor technology, embedded technology and low-power wireless communication technology, wireless sensor networks have aroused more and more attention. WSN refer to the self-organizing multi-hop networks, in which the monitoring area is composed of many micro-sensor nodes and are formed by wireless communication, aiming to collaboratively perceive, collect and dispose the information from the perceived objects in the network overlay area, and then send to the observer. With the broad application prospects, WSN can be applied to national defense and military, medical and health, environmental monitoring, disaster site and other areas.In WSN, sensor nodes are deployed randomly and densely in the monitored area. The precise positions of the most nodes may be unknown in advance; But in order to obtain the exact positions where events occur, it is important to know the nodes' positions. Therefore, determining the positions of the nodes is the prerequisite and basis for a variety of applications, so localization technology is a basic technology of sensor network, have high research value.In localization technology, the centroid localization algorithm is a kind of outdoor localization algorithm which is only based on network connectivity. It is simple, low computational complexity, and entirely based on the network connectivity. However, if the centroid algotithm wants to achieve ideal localization accuracy, it has to increase the anchor node density and has high requirements about the uniformity of the anchor node deployment.As for the inadequacies of the centroid algorithm, the paper has done the work as follows:First, two improved algorithms are proposed around the research of the weighted centroid algorithm:one is the weighted centroid localization algorithm based on RSSI, and the other is the weighted centroid localization algorithm based on power control. The former uses the wireless signal propagation path loss mode to obtain the maximum likelihood estimation of the distance, and introduces the weighting factors related to distance for the centroid algorithm. The latter uses anchor controling power to carry on several rounds of broadcast, and communication radius of each round has the average arithmetic expansion, nodes receive information to get the round-number as a weighting factor for the centroid localization algorithm. Through the simulation, determine two optimal expressions of the weighting factors. The simulation results show that the localization accuracy has been enhanced than the traditional centroid localization algorithm.Second, a kind of weighted centroid localization algorithm based on amendment is proposed on the basis of the weighted centroid algorithm. It makes use of the RSSI weighted centroid algorithm to obtain an orientation position, uses the RSSI value to compute the overall distance error coefficient, and then takes the method of successive approximation to get the amendment value from the orientation results. Simulation results show that this kind of algorithm improves requirements of the high density and uniformity for the nodes, localization effect is not sensitive relative to the growth of nodes communication range and greatly improves the localization accuracy. |