| Integrated modern sensor, micro-electronics, wireless communication, embedded computing, distributed information processing and other technologies, wireless sensor network (WSN) is an emerging research direction. Compared with the traditional networks, WSN is a data-centric wireless network with self-organizing and self-regulating characteristics, and can be widely used in military, health care, space exploration and many other kinds of commercial applications. Location information of each sensor node is essential to WSN. It is not only the basic of taking further measures and making decision-making, but also the research foundation of other key technologies (for example target tracking, routing supporting and network management) in WSN.Most of typical localization algorithms belong to Anchor-Dependent localization, whose localization accuracy decrease quickly once the density of anchor nodes declined significantly, and is not suitable for some harsh or dangerous application environments. Facing on the limitations of Anchor-Dependent localization, based on geometry, probability theory, iterative memorization, graph theory, particle swarm optimization (PSO) and other calculating methods, Anchor-Independent localization research is carried out from two aspects in this thesis: the relative localization and the mobile anchor node based localization. The important research results are as follows:â‘ Based on OK clustering algorithm, a K-hop clustering algorithm for relative localization- Enhanced Overlapped K-hop (EOK) is proposed. In relative localization, accumulating ranging error is one of the main factors affecting localization performance, and can be reduced effectively through clustering. In EOK, some strategy (cluster header selection based on both connectivity and remaining energy of each node, neighbor cluster header mergence based on power control, cluster optimization) are help to satisfy the demands of relative localization on the number of cluster header, overlapping degree of cluster and coordinate transformation rate between neighbor clusters. Compared with OK, EOK not only reduces the number of clusters header and make better uniformity of distribution of clusters, but also can control overlapping degree of cluster and maintain coordinate transformation rate between neighbor clusters at 100%.â‘¡A stepwise refinement relative localization algorithm based on clustering (SRRLC) is put forward. Relative localization algorithm is a typical type of Anchor-Independent algorithms. It needs none anchor nodes, and localization accuracy is not affected by the density of anchor nodes. SRRLC is divided into three stages: initial local localization, localization optimization and local coordinate system transformation. In initial local localization stage, a weighted centroid localization algorithm based on RSSI (WCL-RSSI) is put forwarded. In WCL-RSSI, a frequency allocation based on vertex coloring algorithm is proposed to eliminate the influence of hidden terminal phenomenon on ranging error of cluster border nodes. Besides, reference nodes refining strategy and reference node sets refining strategy are used to reduce the influence of ranging error on WCL-RSSI, and enhance the localization accuracy. In localization optimization stage, a SMACOF based strategy is used to optimize location, and a weight function used in this strategy, general considering both distance and localization errors factors, is put forward. This weight function can speed up the convergence rate of this strategy and better the localization accuracy. Compared with typical relative localization algorithm, SRRLC is not only robust to ranging error and achieve higher localization accuracy, but also enjoys advantages on convergence rate, communication overhead and localization coverage.â‘¢A PSO localization algorithm based on mobile anchor is put forward. In many harsh or dangerous application environments, parameters in path loss model of wireless channel are unknown, and neighbor nodes are unable to range using RSSI. So localization in this environment which path loss model of wireless channel is unknown, is abstracted into non-linear constraint optimization in PLBMA.A weighted localization target function is designed and the location of each node can be estimate based on PSO. In order to reduce localization cost and the dependence of localization accuracy on the density of anchor nodes, a mobile anchor node is used in PLBMA instead of static anchor nodes in Anchor-Dependent localization algorithm. Network interest area is divided into grids, and the mobile anchor node traversals network interest area based on shortest path traversal strategy, which insure network interest area can be complete covered with virtual anchor nodes. The principle of PLBMA is simple and easy to implement, and there is only a few adjustable parameters. After a few times of iteration, localization accuracy can be improved obviously and is robust to the environment noise interference. PLBMA expands the application adjustability of Anchor-Independent localization technology.â‘£Considering military defense, disaster monitoring and rescue and other harsh or dangerous application environments, an Anchor-Independent localization application prototype system - multi-modal monitoring prototype system based on WSN is built. Facing on mixed network topology with multiple mobile Sinks, a new routing protocol is designed and implemented in this system. Besides that, integrated Pioneer3 intelligent mobile platform and PLBMA, a event localization strategy is put forward and implemented. The conception of conventional static WSN has been enriched and expended because of some new elements integrated in this system: 1) both 802.11g and 802.15.4 wireless communication protocol are coexisted, 2) mixed network topology with multiple mobile Sinks, 3) intelligent mobile platform is used.An in-depth study of Anchor-Independent localization theory and application technology is carried out in this thesis. Three relative algorithms have been studied and put forward, and an Anchor-Independent localization application prototype system is built. The simulation and experiment results full proof the validity of each algorithm and system. In near future, some research about each algorithm proposed will be carried out from two aspects: improve the performance and enhance the practicability; besides some application research on this prototype system will also be carried out.
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