Sajina Pradhan

A TOA Shortest Distance Algorithm for Estimating Mobile Location

위치 추정 기술 (LDT, Location Detection Technology)은 자원관리 및 통신 서비스의 품질을 향상시키기 위한 무선통신 분야에서 사용되고 있는 LBS(Location Based Service)의 핵심기술 중 하나이다. 이동국(MS, mobile station)의 위치는 세 개의 기지국(BS, base station)들의 좌표와 이동국과 기지국들 사이의 거리에 상응하는 반지름에 기초한 세 개의 원들에 기반한 도래시간(TOA, Time of Arrival)기법을 사용하여 추정된다. 삼각변 측량법을 이용하여 정확한 이동국의 위치를 추정하기 위해서는 세 개의 원들이 한 점에서 만나야 하는데, 이동국과 기지국의 거리를 추정하기 위한 시간지연 개수와 전송 주파수에 따라 원들의 반지름이 증가하여 세 개의 원들이 한 점에서 만나지 못하는 경우들이 발생한다. 반지름이 증가된 세 개의 원들은 여섯 개의 교점을 가지게 되고 이 교점들 중 세 개의 교점들이 특정 이동국의 좌표에 가까이 위치하게 된다. 본 논문에서는 여섯 개의 전체 교점들 중에서 세 개의 내부 교점들을 선택하는 TOA 삼각변 측량법을 위한 최단 거리 알고리즘을 제안한다. 제안된 방법은 여섯 개의 교점들 중 이동국의 좌표와 가장 가까운 세 개의 교점을 선택하고, 선택된 교점들의 평균 좌표를 특정 이동국의 위치로 결정한다. 제안된 알고리즘의 성능은 컴퓨터 시뮬레이션 예를 통해 확인된다.

Line Intersection Algorithm for the Enhanced TOA Trilateration Technique

The location determination technology (LDT) is one of the core techniques for the location-based services (LBS) which has various applications, including a mobile robot, for the modern wireless com...

Comparison Approach of Intersection Distances for Advanced TOA Trilateration

The time of arrival trilateration method is one of the representative algorithms for the location detection technology, which estimates the location of mobile station (MS) at a unique intersection point of three circles with radiuses corresponding to distances between MS and base stations (BSs) and centers corresponding to coordinates of BSs. However, there may be serious estimation errors, when they do not meet at a point because the estimated radiuses of them are increased. The solutions for reducing the estimation position error in the main case of meeting three circles with the extended radius have been recently provided as the shortest distance algorithm and the line intersection algorithm. In general, they have good performance for the location estimation, but they may have serious errors in some cases. In this paper, we propose the efficient location estimation algorithm for the specific case of two large circles and one relatively small circle, which is located in the area of two large circles. In this case, there are six intersections in total based on the three extended circles and a small circle has four intersections with two large circles. The proposed approach compares four distances based on four neighboring intersections and selects the shortest one. Finally, it determines the averaged coordinate of two intersections corresponding to the shortest distance, as the location of MS. The location-estimating performance of the proposed algorithm is illustrated by the computer simulation example.

The advanced TOA trilateration algorithms with performance analysis

The time of arrival (TOA) trilateration, which is one of the representative localization algorithms, estimates the location of the mobile station (MS) based on the received signals from at least three base stations (BS). The MS location is determined at a single intersecting point of three circles with radiuses corresponding to distances between MS and BSs and centers corresponding to BSs coordinates. In general, three estimated circles may not meet at a single point, causing the location estimation error, because the distance between MS and BS is usually estimated by counting the number of delay samples, which it should be an integer but it is not originally integer, and it may be slightly increased. In this paper, we present the advanced TOA trilateration algorithms for solving the above problem, such as the line intersection algorithm, which has good performance in the general case, and the comparison approach of intersection distances which has good performance in the specific case where one relatively small circle is located inside the area of two large circles. In addition, we analytically prove that the comparison approach of intersection distances in the specific case has better performance for estimating the MS location than that of the line intersection algorithm.

Mathematical analysis of line intersection algorithm for TOA trilateration method

Time of arrival (TOA) technique based on the trilateration method is one of the representative location detection technologies (LDT), which have various applications in the wireless communication system. It utilizes signals from three base stations (BS) for estimating the location of a mobile station (MS). Since the location of MS is estimated using the distance between the MS and BS and the distance is estimated using the number of the time delay, three circles based on three radii between MS and three BSs should not meet at a point. In order to solve this problem, the shortest distance algorithm which selects three nearest intersection points among six intersection points from three circles was proposed. However, it sometimes has high location estimation errors in the extreme cases due to the selection of three intersection points. In order to overcome this problem, we consider the line intersection algorithm which does not require selecting interior intersection points. Although this algorithm has good performance of the location estimation, it must assume that three lines, connecting two intersections based on two circles, meet at a point. In this paper, we also mathematically prove that these three intersection lines based on three circles meet at a point. In this algorithm, we determine this intersection point based on three lines as the location of MS.

Enhanced location detection algorithms based on time of arrival trilateration

The TOA trilateration method decides the location of MS using an intersection point of three circles with centers corresponding three base station (BS) coordinates and radius based on the distance between MS and three BSs. Since the distance between BS and MS is generally estimated counting the number of time delay samples, the estimated distances are slightly increased and three circles may not intersect at a point. In this paper, we introduce the shortest distance and line intersection algorithms for improving conventional TOA trilateration method to resolve above problem. Also, the mathematic analysis is provided to indicate the relation between both algorithms.