A Survey of Localization in Wireless Sensor Network <s> Cooperative Node Localization. <s> Wireless sensor networks are widely adopted in many location-sensitive applications including disaster management, environmental monitoring, military applications where the precise estimation of each node position is inevitably important when the absolute positions of a relatively small portion as anchor nodes of the underlying network were predetermined. Intrinsically, localization is an unconstrained optimization problem based on various distance/path measures. Most of the existing localization methods focus on using different heuristic-based or mathematical techniques to increase the precision in position estimation. However, there were recent studies showing that nature-inspired algorithms like the ant-based or genetic algorithms can effectively solve many complex optimization problems. In this paper, we propose to adapt an evolutionary approach, namely a micro-genetic algorithm, as a post-optimizer into some existing localization methods such as the Ad-hoc Positioning System (APS) to further improve the accuracy of their position estimation. Obviously, our proposed MGA is highly adaptable and easily integrated into other localization methods. Furthermore, the remarkable improvements attained by our proposed MGA on both isotropic and anisotropic topologies of our simulation tests prompt for several interesting directions for further investigation. <s> BIB001 </s> A Survey of Localization in Wireless Sensor Network <s> Cooperative Node Localization. <s> Location-aware technologies will revolutionize many aspects of commercial, public service, and military sectors, and are expected to spawn numerous unforeseen applications. A new era of highly accurate ubiquitous location-awareness is on the horizon, enabled by a paradigm of cooperation between nodes. In this paper, we give an overview of cooperative localization approaches and apply them to ultrawide bandwidth (UWB) wireless networks. UWB transmission technology is particularly attractive for short- to medium-range localization, especially in GPS-denied environments: wide transmission bandwidths enable robust communication in dense multipath scenarios, and the ability to resolve subnanosecond delays results in centimeter-level distance resolution. We will describe several cooperative localization algorithms and quantify their performance, based on realistic UWB ranging models developed through an extensive measurement campaign using FCC-compliant UWB radios. We will also present a powerful localization algorithm by mapping a graphical model for statistical inference onto the network topology, which results in a net-factor graph, and by developing a suitable net-message passing schedule. The resulting algorithm (SPAWN) is fully distributed, can cope with a wide variety of scenarios, and requires little communication overhead to achieve accurate and robust localization. <s> BIB002 </s> A Survey of Localization in Wireless Sensor Network <s> Cooperative Node Localization. <s> The recent demonstration of precise ranging measurements through low power Low Data Rate (LDR) Impulse Radio - Ultra Wideband (IR-UWB) communications has disclosed new perspectives for cooperative location-enabled wireless networks. With this respect, joint ranging and distributed positioning mechanisms supported by specific protocol transactions have already been proposed within user-centric infrastructureless applications. However, in spite of advanced medium access techniques, those approaches still suffer from resource inefficiency. In this paper, we describe and compare new scheduling strategies regarding the joint update of ranging measurements and positional information. One goal is to accelerate the convergence of positioning errors and hence to reduce network latency and overhead accordingly. As an example, one scheduling option considers discarding so-called useless pair-wise links based on the prior analysis of the conditional Cramer Rao Lower Bound (CRLB) of positioning errors at each mobile node. <s> BIB003 </s> A Survey of Localization in Wireless Sensor Network <s> Cooperative Node Localization. <s> We developed a TOA/TDOA hybrid relative positioning system with UWB-IR technology. The proposed system reduces both the number of base stations and the wireless communication times in a positioning sequence. We evaluated the system performance over various distances between base stations by using computer simulations and experiments, assuming that the target nodes were outside the area surrounded by the base stations. For the experiments, we implemented the system with UWB transceivers that we developed. From the experimental results, we confirmed that the proposed system could detect the relative positions of the target nodes using two base stations 4 m apart and with a measured angle accuracy of 8.6 degrees. <s> BIB004 </s> A Survey of Localization in Wireless Sensor Network <s> Cooperative Node Localization. <s> Cooperative positioning is an emerging topic in wireless sensor networks and navigation. It can improve the positioning accuracy and coverage in GPS-challenged conditions such as inside tunnels, in urban canyons, and indoors. Different algorithms have been proposed relying on iteratively exchanging and updating positional information. For the purpose of computational complexity, network traffic, and latency, it is desirable to minimize the amount of information shared between devices, while still maintaining acceptable performance. We show that information that is not reliable should not be shared, and information that is not informative should not be used. This naturally leads to censoring schemes. We consider different censoring schemes based on the Cramer Rao bound (CRB). We find that by blocking the broadcasts of the nodes that do not have reliable estimates (transmit censoring) and selecting the most usable links after receiving signals from neighbors (receive censoring), complexity and traffic can be reduced significantly without degrading positioning performance. <s> BIB005 </s> A Survey of Localization in Wireless Sensor Network <s> Cooperative Node Localization. <s> The problem of positioning a target node is studied for wireless sensor networks with cooperative active and passive sensors. Two-way time-of-arrival and time-difference-of-arrival measurements made by both active and passive nodes are used to estimate the position of the target node. A maximum likelihood estimator (MLE) can be employed to solve the problem. Due to the nonlinear nature of the cost function in the MLE, an iterative search might converge to local minima which often results in large estimation errors. To avoid this drawback, we instead formulate the problem of positioning as finding the intersection of a number of convex sets derived from measurements. To obtain this intersection, we apply the projection onto convex sets approach, which is robust and can be implemented in a distributed manner. Simulations are performed to compare the performance of the MLE and the proposed method. <s> BIB006
There may be not enough information in the concentrated network or the node may contain the harmful information in sparse network. There are two branches in this area: (1) access the accuracy and reliability of the neighborhood nodes. (2) Improve precision with the cooperation of the active and passive nodes. Some nodes may bring unreliable or even harmful information BIB002 , so it is essential to review the received information. Tam et al. BIB001 employed the nearest link as reference to review the information. When there are massive link in dense network and positioning mainly depends on the geometry of the neighbor node topology information, the nearest neighbors may not correspond to the best link. Aiming at this issue, Denis et al. BIB003 proposed an adaptive method to eliminate the inefficient links, but this method has to work with neighbor node information, and the method cannot effectively reduce the number of packet effectively. Therefore, Das and Wymeersch BIB005 put forward a kind of distributed criterion; this method employed Cramer-Rao limit as identifiable parameters to identify the links. This method could avoid the invalid neighbor node links and unreliable transmission; thus, it can effectively reduce the computation time and the number of packets. The accuracy of master-slave node cooperative localization is mainly depended on the measurements accuracy and the number of primary reference nodes (PRN, Primary Reference Node). But in the actual application, it is difficult to increase the number of primary reference nodes because of the factors of energy and the complexity. Wymeersch et al. BIB002 and Fujiwara et al. BIB004 put forward a new method: the nodes which received the information of the target and the primary reference nodes are termed as secondary reference nodes (SRN, secondary Reference Node), the SRNs participated in the localization in a passive way. This cooperative method reduced the required number of PRN with relatively higher localization accuracy. Gholami et al. BIB006 used the maximum likelihood estimation method to obtain the target position. The authors formulated the localization problem into finding the intersection of the vertex set by using geometry description. This method avoids getting into the local optimum.