Cooperative Localization Algorithm Research Articles

Closed-Form Hop-Count Distributions in Random Networks with Arbitrary Routing

We contribute a new solution to the problem of establishing an analytical relationship between hop-counts under a certain routing policy and Euclidean distances in random networks, both in the linear and planar cases. The contributed solution is unified, in that hop-count distributions have similar expressions both in the 1D and the 2D cases; general in terms of routing policies, in that the effect of any given policy is accounted for by means of a single parameter; closed-form, such that hop-count probability mass functions (PMF's) are given in terms of scaled versions of the closed-form PMF's of the number of nodes; and mathematically tractable, since the derived hop-count distributions are in the form of a difference of the well-known Nakagami-m cumulative density functions (CDF's). Direct and Kullback-Leibler divergence comparisons against empirical data demonstrate the high accuracy of our solution. The simplicity, accuracy and generality of the result owes partly to a self-imposed confinement to connected networks, defined formally in stochastic-geometric terms, which allows for the elimination of recursions and multivariate marginalization commonly required by existing solutions. The contributed results find application in the design and analysis of ad hoc networks, cooperative localization algorithms or latency and energy consumption analysis.

Localization Algorithm with On-line Path Loss Estimation and Node Selection

RSS-based localization is considered a low-complexity algorithm with respect to other range techniques such as TOA or AOA. The accuracy of RSS methods depends on the suitability of the propagation models used for the actual propagation conditions. In indoor environments, in particular, it is very difficult to obtain a good propagation model. For that reason, we present a cooperative localization algorithm that dynamically estimates the path loss exponent by using RSS measurements. Since the energy consumption is a key point in sensor networks, we propose a node selection mechanism to limit the number of neighbours of a given node that are used for positioning purposes. Moreover, the selection mechanism is also useful to discard bad links that could negatively affect the performance accuracy. As a result, we derive a practical solution tailored to the strict requirements of sensor networks in terms of complexity, size and cost. We present results based on both computer simulations and real experiments with the Crossbow MICA2 motes showing that the proposed scheme offers a good trade-off in terms of position accuracy and energy efficiency.

Information Fusion for Localization Within Vehicular Networks

Cooperative positioning (CP) is a localization technique originally developed for use across wireless sensor networks. With the emergence of Dedicated Short Range Communications (DSRC) infrastructure for use in Intelligent Transportation Systems (ITS), CP techniques can now be adapted for use in location determination across vehicular networks. In vehicular networks, the technique of CP fuses GPS positions with additional sensed information such as inter-vehicle distances between the moving vehicles to determine their location within a neighbourhood. This paper presents the results obtained from a research study undertaken to demonstrate the capabilities of DSRC for meeting the positioning accuracies of road safety applications. The results show that a CP algorithm that fully integrates both measured/sensed data as well as navigation information such as map data can meet the positioning requirements of safety related applications of DSRC (<0·5 m). This paper presents the results of a Cramer Rao Lower Bound analysis which is used to benchmark the performance of the CP algorithm developed. The Kalman Filter (KF) models used in the CP algorithm are detailed and results obtained from integrating GPS positions, inter-vehicular ranges and information derived from in-vehicle maps are then discussed along with typical results as determined through a variety of network simulation studies.

SIMULTANEOUS COOPERATIVE LOCALIZATION FOR AUVs USING RANGE-ONLY SENSORS

The absence of GPS underwater makes navigation for autonomous underwater vehicles (AUVs) a challenge. Moreover, the use of static beacons in the form of a long baseline (LBL) array limits the operation area to a few square kilometers and requires substantial deployment effort before operations. In this paper, an algorithm for cooperative localization of AUVs is proposed. We describe a form of cooperative Simultaneous Localization and Mapping (SLAM). Each of the robots in the group is equipped with an Inertial Measurement Unit (IMU) and some of them have a range-only sonar sensor that can determine the relative distance to the others. Two estimators, in the form of a Kalman filter, process the available position information from all the members of the team and produce a pose estimate for every one of them. Simulation results are presented for a typical localization example of three AUVs formation in a large environment and indirect trajectory. The results show that our proposed method offers good localization accuracy, although a small number of low-cost sensors are needed for each vehicle, which validates that it is an economical and practical localization approach.

Cooperative localization against GPS signal loss in multiple UAVs flight

Based on multiple unmanned aerial vehicles (UAVs) flight at a constant altitude, a fault-tolerant cooperative localization algorithm against global positioning system (GPS) signal loss due to GPS receiver malfunction is proposed. Contrast to the tradi- tional means with single UAV, the proposed method is based on the use of inter-UAV relative range measurements against GPS signal loss and more suitable for the small-size and low-cost UAV applications. Firstly, for re-localizing an UAV with a malfunction in its GPS receiver, an algorithm which makes use of any other three healthy UAVs in the cooperative flight as the reference points for re-localization is proposed. Secondly, by using the relative ranges from the faulty UAV to the other three UAVs, its horizontal location can be determined after the GPS signal is lost. In order to improve an accuracy of the localization, a Kalman filter is fur- ther exploited to provide the estimated location of the UAV with the GPS signal loss. The Kalman filter calculates the variance of observations in terms of horizontal dilution of positioning (HDOP) automatically. Then, during each discrete computing time step, the best reference points are selected adaptively by minimizing the HDOP. Finally, two simulation examples in Matlab/Simulink envi- ronment with five UAVs in cooperative flight are shown to evaluate the effectiveness of the proposed method.

Cooperative AUV Navigation using a Single Maneuvering Surface Craft

In this paper we describe the experimental implementation of an online algorithm for cooperative localization of submerged autonomous underwater vehicles (AUVs) supported by an autonomous surface craft. Maintaining accurate localization of an AUV is difficult because electronic signals, such as GPS, are highly attenuated by water. The usual solution to the problem is to utilize expensive navigation sensors to slow the rate of dead-reckoning divergence. We investigate an alternative approach that utilizes the position information of a surface vehicle to bound the error and uncertainty of the on-board position estimates of a low-cost AUV. This approach uses the Woods Hole Oceanographic Institution (WHOI) acoustic modem to exchange vehicle location estimates while simultaneously estimating inter-vehicle range. A study of the system observability is presented so as to motivate both the choice of filtering approach and surface vehicle path planning. The first contribution of this paper is to the presentation of an experiment in which an extended Kalman filter (EKF) implementation of the concept ran online on-board an OceanServer Iver2 AUV while supported by an autonomous surface vehicle moving adaptively. The second contribution of this paper is to provide a quantitative performance comparison of three estimators: particle filtering (PF), non-linear least-squares optimization (NLS), and the EKF for a mission using three autonomous surface craft (two operating in the AUV role). Our results indicate that the PF and NLS estimators outperform the EKF, with NLS providing the best performance.

무선 전파특성을 고려한 협력 위치추정 알고리즘 성능분석

본 논문에서는 실내외 무선 센서네트워크 환경에서 전파특성을 고려한 수신신호세기 기반의 협력 위치추정 알고리즘을 제안하고 이에 대해 성능을 분석하였다. 기존의 수신신호세기 기반의 위치추정 기법은 장애물 등 전파환경에 따라 신호세기가 불안정하여 낮은 위치추정 신뢰도를 보였다. 이러한 불안정한 전파환경을 극복하기 위해 본 논문에서는 광선발사법을 통해 도출된 전파특성 요인을 제안하는 협력 위치추정 알고리즘에 반영하였다. 또한 협력 위치추정 알고리즘의 성능평가를 위해 4개의 가상공간에 고정위치를 알고 있는 4개의 Zigbee 노드와 위치를 알지 못하는 미지의 Zigbee 노드 5개를 배치하여 실험하였다. 실험결과, NLCA의 경우 2m-3.5m 오차를 보였으나 본 논문에서 제안하는 CLA/ECLA의 경우는 1.3m-2.5m/0.5m-1.2m로 선형적인 성능개선을 보였다. 그러므로 전파특성요인이 고려되었을 경우 기존의 수신신호세기 기반 위치추정 방식에 비해 본 논문에서 제안하는 협력위치추정 방식이 보다 효율적임을 확인하였다. In this paper, we proposed and analyzed a RSSI based cooperative localization algorithm considering wireless propagation characteristics in indoor and outdoor environments for wireless sensor networks, which can estimate the BN position. The conventional RSSI based estimation scheme has low precision ranging due to instability propagation characteristics by time variable. Hence, we implemented ray-launching simulator for analysis of propagation characteristics in 4 case, and experimented proposed localization scheme with 4 RN and 1 to 5 BN. Simulation results show that NLCA has estimation error as 2m-3.5m, however, proposed CLA/ECLA has 1.3m-2.5m/0.5m-1.2m by same environments. Therefore, if we can consider channel characteristics, the proposed algorithm provides higher localization accuracy than RSSI based conventional one.

Convex Optimization Algorithms for Cooperative Localization in Autonomous Underwater Vehicles

In this paper, a cooperative localization algorithm for autonomous underwater vehicles (AUVs) is proposed. A “parallel” model is adopted to describe the cooperative localization problem instead of the traditional “leader-follower” model, and a linear programming associated with convex optimization method is used to deal with the problem. After an unknown-but-bounded model for sensor noise is assumed, bearing and range measurements can be modeled as linear constraints on the configuration space of the AUVs. Merging these constraints induces a convex polyhedron representing the set of all configurations consistent with the sensor measurements. Estimates for the uncertainty in the position of a single AUV or the relative positions of two or more nodes can then be obtained by projecting this polyhedron onto appropriate subspaces of the configuration space. Two different optimization algorithms are given to recover the uncertainty region according to the number of the AUVs. Simulation results are presented for a typical localization example of the AUV formation. The results show that our positioning method offers a good localization accuracy, although a small number of low-cost sensors are needed for each vehicle, and this validates that it is an economical and practical positioning approach compared with the traditional approach.

Mobile element assisted cooperative localization for wireless sensor networks with obstacles

In this paper, a cooperative localization algorithm is proposed that considers the existence of obstacles in mobility-assisted wireless sensor networks (WSNs). An optimal movement scheduling method with mobile elements (MEs) is proposed to address limitations of static WSNs in node localization. In this scheme, a mobile anchor node cooperates with static sensor nodes and moves actively to refine location performance. It takes advantage of cooperation between MEs and static sensors while, at the same time, taking into account the relay node availability to make the best use of beacon signals. For achieving high localization accuracy and coverage, a novel convex position estimation algorithm is proposed, which can effectively solve the problem when infeasible points occur because of the effects of radio irregularity and obstacles. This method is the only rangefree based convex method to solve the localization problem when the feasible set of localization inequalities is empty. Simulation results demonstrate the effectiveness of this algorithm.

Cooperative Localization in Wireless Networks

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.