Directional antennas for wireless sensor networks

Directional antennas provide angle-of-arrival information, which can be used for localization and routing algorithms in wireless sensor networks. We briefly describe three classical, major types of antennas: 1) the Adcock-pair antenna, 2) the pseudo-Doppler antenna, and 3) the electronically switched parasitic element antenna. We have found the last type to be the most suitable for wireless sensor networks, and we present here the early design details and beam pattern measurements of a prototype antenna for the 2.4-GHz ISM band, the SPIDA: SICS Parasitic Interference Directional Antenna

A Robust Frame of WSN Utilizing Localization Technique

Wireless sensor networks are becoming increasingly popular due to their low cost and wide applicability to support a large number of diverse application areas. Localization of sensor nodes is a fundamental requirement that makes the sensor data meaningful. A wireless sensor network (WSN) consist of spatially distributed autonomous devices using sensors to monitor cooperatively physical or environmental conditions such as temperature, sound, vibration, pressure, motion or pollutants at different locations. The development of wireless sensor networks was originally motivated by a military application like battlefield surveillance. Node localization is required to report the origin of events, assist group querying of sensors, routing and to answer questions on the network coverage. So one of the fundamental challenges in wireless sensor network is node localization. This paper discusses different approaches of node localization discovery in wireless sensor networks. The overview of the schemes proposed by different scholars for the improvement of localization in wireless sensor networks is also presented. Keywords: Localization, Particle Swarm Optimization, Received Signal Strength, Angle of Arrival

Design and Implementation of an Ultrasonic Localization System for Wireless Sensor Networks using Angle-of-Arrival and Distance Measurement

AbstractThis paper presents a localization system for Wireless Sensor Networks (WSN) based on ultrasonic (US) Time-of-Flight (ToF) measurements. The participants send out US pulses while a central localization unit measures the Time-Difference-of-Arrival (TDoA) between four US sensors to calculate the Angle-of-Arrival (AoA). The radio frequency (RF) transceiver of the sensor nodes enables distance measurements using TDoA (US vs. RF) in addition. This improves the localization accuracy significantly since the estimated distance from triangulation suffers excessively from even small angle errors. Several filter stages including Kalman-filtering minimize the number of outliers and fluctuations of the calculated distances and angles. Those computed polar coordinates (angle/distance) are converted into a Cartesian form and forwarded to a base station which is connected to a PC. The mean error and standard deviation of the angle and distance measurements (1.36 ¡ ± 0.39 ¡ / 1.00cm ± 0.14cm) lead to a small mean localization error of 4.21cm and a standard deviation of 0.57cm

DESIGN AND IMPLEMETATION OF NETWORK LOCALIZATION SERVICE USING ANGLE-INDEXED SIGNAL STRENGTH MEASUREMENTS

The recent technological developments in low-power electronics and wireless communication have increased the use of ad hoc wireless sensor networks for environmental monitoring and security applications. A typical network is a randomly distributed collection of scores of low-power wireless sensor nodes. Network localization is the process of estimating the location of each sensor in the network. Network localization is an imperative capability for the effective operation of wireless sensor networks. In this research project we explore an innovative approach to localization that uses an array of directional antennas, together with a node’s radio communications, to sense the bearing and distance between neighboring nodes. We also pursue a variety of computational methods to determine the best position estimator. We found that the proposed localization approach can measure the angle of arrival (AOA) with about 4 degrees mean absolute error and can determine distance between the transmitter and receiver with 5 feet mean absolute error using the prototype antenna array. In addition, the mean absolute distance error between the actual and estimated positions was found to be 14.5 feet (about 4.5 meters). Also, compared to other approaches, our approach can solve the network localization problem with fewer beacon nodes needed in the network, which means a significant reduction in hardware and software cost. Our findings demonstrate the feasibility of non-coherently using directional arrays in wireless sensor networks for determining angle from radio signal strength. The estimated angles, combined with either coarse distance information or a few known node locations, provide a solution for the network localization task

Investigations on real time RSSI based outdoor target tracking using kalman filter in wireless sensor networks

Target tracking is essential for localization and many other applications in Wireless Sensor Networks (WSNs). Kalman filter is used to reduce measurement noise in target tracking. In this research TelosB motes are used to measure Received Signal Strength Indication (RSSI). RSSI measurement doesn’t require any external hardware compare to other distance estimation methods such as Time of Arrival (TOA), Time Difference of Arrival (TDoA) and Angle of Arrival (AoA). Distances between beacon and non-anchor nodes are estimated using the measured RSSI values. Position of the non-anchor node is estimated after finding the distance between beacon and non-anchor nodes. A new algorithm is proposed with Kalman filter for location estimation and target tracking in order to improve localization accuracy called as MoteTrack InOut system. This system is implemented in real time for indoor and outdoor tracking. Localization error reduction obtained in an outdoor environment is 75%

Cooperative and Distributed Localization for Wireless Sensor Networks in Multipath Environments

We consider the problem of sensor localization in a wireless network in a multipath environment, where time and angle of arrival information are available at each sensor. We propose a distributed algorithm based on belief propagation, which allows sensors to cooperatively self-localize with respect to one single anchor in a multihop network. The algorithm has low overhead and is scalable. Simulations show that although the network is loopy, the proposed algorithm converges, and achieves good localization accuracy

Efficient AoA-based wireless indoor localization for hospital outpatients using mobile devices

The motivation of this work is to help outpatients find their corresponding departments or clinics, thus, it needs to provide indoor positioning services with a room-level accuracy. Unlike wireless outdoor localization that is dominated by the global positioning system (GPS), wireless indoor localization is still an open issue. Many different schemes are being developed to meet the increasing demand for indoor localization services. In this paper, we investigated the AoA-based wireless indoor localization for outpatients’ wayfinding in a hospital, where Wi-Fi access points (APs) are deployed, in line, on the ceiling. The target position can be determined by a mobile device, like a smartphone, through an efficient geometric calculation with two known APs coordinates and the angles of the incident radios. All possible positions in which the target may appear have been comprehensively investigated, and the corresponding solutions were proven to be the same. Experimental results show that localization error was less than 2.5 m, about 80% of the time, which can satisfy the outpatients’ requirements for wayfinding