• 한국항공운항학회지
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• 제17권1호
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• pp.52-57
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• 2009

One of the error sources for microwave ranging is the instability of the oscillator that drives the microwave signals. Dual one-way ranging (DOWR) minimizes the oscillator effect by combining two one-way carrier phase signals from two transmitter/receiver instrument. The DOWR is first implemented in the GRACE (Gravity Recovery and Climate Experiment) satellites. Direct evaluation of the DOWR is not possible due to its extremely high accuracy. The flight performance of the GRACE DOWR is analyzed by applying several indirect methods. Comparison with the design noise level is discussed.

• 한국정보통신학회논문지
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• 제14권3호
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• pp.587-594
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• 2010

본 논문에서는 two-way ranging protocol 기반의 비동기 IR-UWB 거리 측정 시스템을 제안한다. 거리 측정을 위해서 주기 선호 특성을 지닌 펄스열을 송신하며 수신단에서는 수신 펄스열을 아날로그 코릴레이터 뱅크틀 이용해서 주파수 도메인으로 변환한 후 주파수 도메인에서 디지털 선호 처리를 하게 되어 펄스률 정도 속도의 ADC로 구현이 가능하다. 제시된 알고리즘은 주파수 도메인에서 다중경로 채널 보상 및 matched 필터링을 하여 피크를 검출한 후 검출된 피크에 동기를 이룬 펄스열을 재전송하는 과정을 거친다. CM1 채널을 가정한 두 디바이스 사이의 거리 측정 시뮬레이션을 통해서 제시한 알고리즘의 타당성을 검증한다.

• 대한임베디드공학회논문지
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• 제5권4호
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• pp.234-242
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• 2010

Two-way ranging methods such as TWR and SDS-TWR have been considered for many ranging systems because these methods are useful in the absence of synchronization. To estimate the location of a mobile node, complicated ranging procedures consisting of ranging frames between an anchor node and the mobile node are performed. Supporting multiple mobile nodes such as a few hundreds or thousands and several anchor nodes, the ranging procedures have the fatal disadvantage of processing delay and inefficient traffic bandwidth. On the other hand, the one-way ranging method is simple and fast, but susceptible to network synchronization. In this paper, we propose a method to modify asynchronous ranging equations to establish exact frequency or frequency offset, a method to estimate frequencies or frequency offsets, and a method to establish post-facto synchronization with anchor nodes. The synchronization for a node pair is adapted using instantaneous time information and corresponding difference of distances can be determined. We evaluate the performance of TWR, SDS-TWR and proposed ranging algorithms.

• 제어로봇시스템학회논문지
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• 제19권2호
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• pp.125-130
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• 2013

Compared to OWR (One-Way Ranging) method that requires precise network time synchronization, TWR (Two-Way Ranging) method has advantages in building an indoor WPAN (Wireless Personal Area Network) location system with lower cost. However, clock offsets of nodes in WPAN system should be eliminated or compensated to improve location accuracy of the TWR method. Because conventional clock offset elimination methods requires multiple TWR transactions to reduce clock offset, they produce network traffic burden instead. This paper presents a clock offset estimation method that can reduce clock offset error with a single TWR transaction. After relative clock offsets of sensor nodes are estimated, clock offsets of mobile tags are estimated using a single TWR communication. Simulation results show that location accuracy of the proposed method is almost similar to the conventional clock offset elimination method, while its network traffic is about a half of the conventional method.

• 로봇학회논문지
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• 제12권3호
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• pp.350-355
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• 2017

UWB (Ultra Wide Band) refers to a system with a bandwidth of over 500 MHz or a bandwidth of 20% of the center frequency. It is robust against channel fading and has a wide signal bandwidth. Using the IR-UWB based ranging system, it is possible to obtain decimeter-level ranging accuracy. Furthermore, IR-UWB system enables acquisition over glass or cement with high resolution. In recent years, IR-UWB-based ranging chipsets have become cheap and popular, and it has become possible to implement positioning systems of several tens of centimeters. The system can be configured as one-way ranging (OWR) positioning system for fast ranging and TWR (two-way ranging) positioning system for cheap and robust ranging. On the other hand, the ranging based positioning system has a limitation on the number of terminals for localization because it takes time to perform a communication procedure to perform ranging. To overcome this problem, code multiplexing and channel multiplexing are performed. However, errors occur in measurement due to interference between channels and code, multipath, and so on. The measurement filtering is used to reduce the measurement error, but more fundamentally, techniques for removing these measurements should be studied. First, the TWR based positioning was analyzed from a stochastic point of view and the effects of outlier measurements were summarized. The positioning algorithm for analytically identifying and removing single outlier is summarized and extended to three dimensions. Through the simulation, we have verified the algorithm to detect and remove single outliers.

• ETRI Journal
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• 제35권3호
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• pp.361-370
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• 2013

In this paper, a packet-reduced ranging method using a superresolution time of arrival estimation algorithm for a chirp-based real-time locating system is presented. A variety of ranging methods, such as symmetric double-sided two-way ranging (SDS-TWR), have been proposed to remove the time drift due to the frequency offset using extra ranging packets. Our proposed method can perform robust ranging against the frequency offset using only two ranging packets while maintaining almost the same ranging accuracy as them. To verify the effectiveness of our proposed algorithm, the error performance of our proposed ranging method is analyzed and compared with others. The total ranging performance of TWR, SDS-TWR, and our proposed TWR are analyzed and verified through simulations in additive white Gaussian noise and multipath channels in the presence of the frequency offset.

• 한국산학기술학회논문지
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• 제11권4호
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• pp.1248-1253
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• 2010

본 논문은 SDS-TWR(Symmetric Double-Sided Two-Way Ranging)의 Ranging 오차를 보정하기 위하여 균등거리비율 개념을 적용한 위치인식 보정 알고리즘인 AEDR(Algorithm for localization using the concept of Equivalent Distance Rate)을 제안하고, 위치인식 실험을 통해 위치인식 측정 성능을 분석하였다. SDS-TWR의 Ranging 오차는 실험에 의하면 비콘노드와 이동노드의 특정 거리구간에서 평균 1m~8m로 측정되었다. 그러나 제안한 AEDR에 의한 위치인식 성능은 실험을 통해 전체적으로 교내 강당과 복도 모두에서 SDS-TWR 보다 4배 정도 우수하였으며, 측정된 3~10m 이상의 위치인식 오차를 평균 2m 내외로, 3m 이내의 위치인식 오차를 평균 1m 내외로 각각 감소시킬 수 있음을 확인하였다. 특히 AEDR은 LOS(Line Of Sight) 보다 NLOS(Non Line Of Sight)에서 훨씬 더 위치인식 보정 성능이 우수함을 나타내며, 대부분의 센서 네트워크의 환경이 NLOS임을 고려할 때 AEDR이 실제환경에서의 위치인식에 큰 도움을 줄 수 있다고 판단된다.

• 한국산학기술학회논문지
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• 제11권6호
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• pp.2263-2268
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• 2010

본 논문은 SDS-TWR(Symmetric Double-Sided Two_Way Ranging)의 Ranging 오차를 보정하여 위치인식 성 능을 향상시키는 방법으로 비컨노드의 거리별 Ranging 오차의 평균 값을 이용하여 Ranging 오차를 보정하는 알고리즘($CA_d$)과, 균등거리비율의 적용으로 Ranging 오차를 보정하는 알고리즘(AEDR)이 적용된 하이브리드형 위치인식 보정 알고리즘($A_{HB}$)을 제안하고, 위치인식 실험을 통해 성능을 분석하였다. 실험결과, $A_{HB}$ 는 전체 32개의 좌표 중 28개 좌표에서 오차 개선이 이루어졌고, 설정한 3개의 오차크기 영역에서 최소한 70%이상의 오차 개선이 이루어졌음을 확인하였다. 또한 32개 좌표에서 발생한 평균 오차 2.67m를 1.19m로 55.4% 보정하였으며 특히 3m 이상의 오차크기 영역에서의 보정 성능은 90% 이상으로 매우 우수함을 확인하였다. 이와 같은 결과를 볼 때, $A_{HB}$ 는 $CA_d$와 AEDR이 각각 수행되었을 때 보다 오차 개선 비율 및 보정 성능이 더 우수함을 확인하였다.

• 한국산학기술학회논문지
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• 제11권3호
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• pp.914-919
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• 2010

CSS(Chirp Spread Spectrum)기반에서 SDS-TWR(Symmetric Double Side-Two-Way Ranging)의 거리측정 정확도는 실험에 의하면 전파환경 간섭으로 인해 일부 레인징 구간에서 매우 큰 오차가 발생함을 확인하였다. 본 논문에서는 이러한 문제를 해결하기 위해 레인징 오차를 감소시킬 수 있는 측정거리의 오차비율 오프셋을 적용한 SDS-TWR의 보정 알고리즘($CA_d$)을 제안하였다. $CA_d$는 두 노드를 LOS(Line Of Sight)환경에서 1~25m까지 1m 간격으로 SDS-TWR으로 거리 값을 측정하여, 거리보정에 필요한 각 파라미터의 값을 계산한 후 이를 사용하여 거리값을 보정한다. 제안한 보정 알고리즘의 성능분석 결과, $CA_d$는 SDS-TWR에 비해 오차가 평균 95cm, 최대 오차가 526cm 감소하였고, 는 25m에서 약 60cm의 오차가 발생함을 확인하였다. 이러한 결과를 볼 때 제안한 $CA_d$는 LOS 환경에서 SDS-TWR에 비해 매우 정밀한 정확도를 가진 것으로 판단된다.

• 제어로봇시스템학회논문지
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• 제21권9호
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• pp.898-902
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• 2015

Alternative radio-navigation technologies aim at providing continuous navigation solution even if one cannot use GNSS (Global Navigation Satellite System). In shadowing region such as indoor environment, GNSS signal is no longer available and the alternative navigation system should be used together with GNSS to provide seamless positioning. For soldiers in battlefield where GNSS signal is jammed or in street battle, the alternative navigation system should work without positioning infrastructure. Moreover, the radio-navigation system should have scalability as well as high accuracy performance. This paper presents a TWR (Two-Way-Ranging)-based cooperative positioning system (CPS) that does not require location infrastructure. It is assumed that some members of CPS can obtain GNSS-based position and they are called mobile anchors. Other members unable to receive GNSS signal compute their position using TWR measurements with mobile anchors and neighboring members. Error propagation in CPS is analytically studied in this paper. Error budget for TWR measurements is modeled first. Next, location error propagation in CPS is derived in terms of range errors. To represent the location error propagation in the CPS, Location Error Propagation Indicator (LEPI) is proposed in this paper. Simulation results show that location error of tags in CPS is mainly influenced by the number of hops from anchors to the tag to be positioned as well as the network geometry of CPS.