Chungsan Kim

Localization with a mobile beacon based on geometric constraints in wireless sensor networks

The location information of sensor nodes is needed for location-based services and network management in wireless sensor networks. Among the many kinds of localization schemes researched to find the location of sensor nodes, a few some schemes presume the use of mobile beacons because using mobile beacons has many potentialities. In particular, a localization scheme with mobile beacons, such as proposed by Ssu et al. [5], has fine-grained accuracy, scalability, and power efficiency even without distance or angle information. To improve the localization accuracy encountered in Ssus scheme, this paper proposes a localization scheme that estimates the location of a sensor node from a possible area where the sensor node is supposed to be, by using geometric constraints. Through simulation results, the proposed scheme is shown to provide higher localization accuracy and reduce the power consumption of sensor nodes by decreasing the communication overhead between sensor nodes and a mobile beacon in comparison to Ssus scheme.

Mobile Beacon-Based 3D-Localization with Multidimensional Scaling in Large Sensor Networks

Localization is essential in wireless sensor networks to handle the reporting of events from sensor nodes. For 3-D applications, we propose a mobile beacon-based localization using classical multidimensional scaling (MBL-MDS) by taking full advantage of MDS with connectivity and measurements. To further improve location performance, MBL-MDS adopts a selection rule to choose useful reference points, and a decision rule to prevent a failure case due to reference points placed on the same plane. Simulation results show improved performance of MBL-MDS in terms of location accuracy and computation complexity.

3D Underwater Localization with Hybrid Ranging Method for Near-Sea Marine Monitoring

Location information is fundamental and essential for UWSNs monitoring underwater environment. Underwater environment requires three dimensional localization algorithm. Several localization protocols and system architectures have been proposed for underwater sensor networks. In this paper, 3D underwater localization algorithm is proposed for near-sea marine monitoring system, using a small number of beacons. Underwater sensors are found through a hierarchical approach. We also propose a distributed self-organized ordering scheme and a hybrid ranging method selecting one of TOA and RSS measurement in order to improve localization accuracy. The proposed 3D underwater localization algorithm increases the coverage of underwater sensor network and makes it possible to achieve accurate location.

LaMSM: localization algorithm with merging segmented maps for underwater sensor networks

Underwater sensor networks (UWSNs) are considered a costeffective solution to ocean applications, such as the acquisition of natural resources in oceans, protection from underwater disasters, etc. These applications basically require location information of nodes to identify the venue of reported events. To locate more accurately the position of nodes, multidimensional scaling (MDS) is widely used because of its good tolerance to errors in measured distances. MDS requires measured distances between every pair of nodes but in practice, only distances between nodes within a communication range can be measured. Hence, the well-known MDS-MAP(P) [6] calculates unmeasured distances for MDS but these calculations result in large errors. In this paper, we proposed a localization algorithm with merging segmented maps (LaMSM) that constructs many reliable segmented maps composed of only nodes within a communication range, and then merges them together based on their common nodes. The segmented maps are built from only the measured distances and as a result, LaMSM provides more accurate node positions than MDS-MAP(P).

Localization with a Mobile Beacon based on Geometric Constraints in Wireless Sensor Networks

The location information of sensor nodes is needed for location-based services and network management in wireless sensor networks. Among the many kinds of localization schemes researched to find the location of sensor nodes, a few some schemes presume the use of mobile beacons because using mobile beacons has many potentialities. In particular, a localization scheme with mobile beacons, such as proposed by Ssu et al. [5], has fine-grained accuracy, scalability, and power efficiency even without distance or angle information. To improve the localization accuracy encountered in Ssus scheme, this paper proposes a localization scheme that estimates the location of a sensor node from a possible area where the sensor node is supposed to be, by using geometric constraints. Through simulation results, the proposed scheme is shown to provide higher localization accuracy and reduce the power consumption of sensor nodes by decreasing the communication overhead between sensor nodes and a mobile beacon in comparison to Ssus scheme.

Path Planning of a Mobile Beacon for Localization in Underwater Sensor Networks

In underwater sensor networks, localization is one of the most important issues because sensor nodes are considerably difficult to be deployed at determined locations. Localization schemes using a mobile beacon have fine-grained localization accuracy because one mobile beacon can replace a lot of static beacons. In localization with a mobile beacon, the movement of a mobile beacon determines the deployment of the beacons used for localization and the deployment influences the localization accuracy. To improve the localization accuracy for localization with a mobile beacon, the study on the path of a mobile beacon is necessary. In this paper, we propose a static path to improve the localization accuracy by considering the path of a mobile beacon and the deployment of the beacons. Simulation results show that the determined static path provides higher localization accuracy than a random path and other static paths.

Long-Range Beacons on Sea Surface Based 3D-Localization for Underwater Sensor Networks

In underwater sensor networks (UWSNs), localization is an important issue and a challenging task due to harsh environments for people to access. In this paper, we propose a distributed algorithm to locate nodes deployed in 3-D space using long-range beacons floating on the sea surface. Long-range beacons allow underwater nodes directly to obtain reference positions of beacons and to measure distances to beacons. Because all beacons are placed on the same plane, i.e. the sea surface, the proposed algorithm estimates two candidates for a node position with multidimensional scaling and then determines the final position out of two candidates. Simulation results confirm that our proposed algorithm can achieve high location accuracy with respect to measurement errors.

Floating beacon-assisted 3-D localization for variable sound speed in underwater sensor networks

In this paper, we propose a floating beacon-assisted 3-D localization for variable sound speed in underwater sensor networks (FBL-VSS). Most underwater localization schemes have assumed that the sound speed is constant under water for simplicity; however, it is actually variable depending on depth and seasonal variation. Taking into account various sound speed, FBL-VSS utilizes novel beacons moored to the sea floor. Each beacon has a transmitter floating on the sea surface and a receiver placed on the sea floor, in order to obtain the average of the actual sound speed from the sea surface to the sea floor by measuring the time of flight (TOF) of broadcasted messages. For self-location, FBL-VSS uses multidimensional scaling techniques with distances computed from the average of the actual sound speed. Simulation result shows that our proposed scheme has stable location accuracy for variable sound speed profile under water.

Bearings-only Tracking Systems with Distributed Floating Beacons in Underwater Sensor Networks

This paper presents a bearings-only tracking (BOT) scheme based on distributed floating beacons in underwater sensor networks (UWSNs). Conventional BOT systems extract target-originated bearings in noisy measurements, locate and track targets based on the bearings in real time. We propose a tracking scheme by modifying BOT systems for UWSNs where a multidimensional assignment (MDA) method is used to extract target-originated bearings and to associate them with corresponding targets. In addition, a threshold-based decision in extracting bearings in MDA and a local Kalman filter is proposed to keep tracking information at a floating beacon even if a target is undetected. Simulation results show that the proposed scheme has advantage of tracking accuracy over recently known work under low detection probability.

An Exact Analytical Time-Domain Model for Nonlinear Optical Links with Mach-Zehnder Modulator and Photodetector in Dispersive Channel

In this paper, a time-domain approach for exact analytical model is presented to analyze nonlinear optical links in radio-on-fiber (RoF) systems. This analytical model unifies general cases of a dual drive Mach-Zehnder modulator (DD-MZM) and photodetector (PD) in dispersive channel, which results in output current after a PD as a function of the summation of each frequency component in time domain. Additionally, the model provides explicitly power spectral density function of a photocurrent. By utilizing simulations for typical optical double sideband and single sideband signals, we confirm that the model is well matched even in relatively high input radio frequency (RF) power