• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.587-594
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• 2010

In this paper, we propose an asynchronous IR-UWB ranging system based on the two-way ranging protocol. The periodic pulse sequence is used to measure a distance between two devices. At the receiver, a received signal is first transformed into a frequency-domain signal using an analog correlator bank and digital signal processing is followed in the frequency-domain. This make it possible for the system to use an ADC with a conversion speed of pulse rate. The proposed algorithm at the receiver side includes a peak detection procedure using mutipath channel compensation and matched filtering, and retransmits a pulse sequence synchronized with the detected peak. The validity of the proposed algorithm is verified from simulation results where the CM1 channel is assumed.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.12
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• pp.1175-1186
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• 2016

The relative distance estimation technique is important to Location-Based Service(: LBS) in a wireless communication environment. In this paper, we propose a scheme for measuring the relative distance by utilizing a frame structure of a physical layer in asynchronous Frequency Division Duplexing(: FDD) when the Internal and external infrastructure for position measurement cannot be used. The proposed method is suitable for continuous distance measurement. The test results showed that the proposed method has the accuracy of less than 10 meters on average.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.169-171
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• 2006

무선 센서 네트워크에서는 고정된 인프라에 의존하기 어려운 환경을 가지고 있다. 하지만, 위치기반 기술을 접목하여 센서의 절대적 또는 상대적인 위치정보를 이용하면 다양한 응용서비스를 효과적으로 적용 할 수 있다. 이러한 센서 노드의 위치를 측정하는 방법 중에 시간을 기반으로 위치를 측정하는 방법이 가장 정확도가 높게 평가되었다[1]. 그러나 이러한 TOA방법은 노드의 Clock Rate에 의존적이기 때문에 위치오차가 발생하게 된다. 따라서 Node의 Clock Drifi를 줄이기 위해서 주기적인 시간동기화가 필요했다[3,4]. 하지만 본 논문에서는 이러한 거리오차를 제거하기 위한 방법으로 시간 비동기화 방법(ALS)을 소개하고, ALS를 기반으로 시뮬레이션과 실질적인 센서를 가지고 노드 사이의 거리와 위치를 측정하였다. 실험 결과, 기존의 TOA방법과 비교하여 거리 및 위치 정확도, Packet 트래픽에 대해서 성능 향상을 확인한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.347-354
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• 2011

This paper presents a time-domain based asynchronous IR-UWB ranging system. This system accomplishes the ranging by detecting peaks from the outputs of a correlator implemented by a FIR filter. To discriminate the peaks due to a signal component, we use windowing for the correlated data within which the data are sorted in amplitude-ascending order and the noise level is calculated. Comparing with the recently presented frequency-domain based ranging system, we show the system structure and explain how it operates for ranging. Moreover, through the simulations, the proposed system is compared with the frequency-domain based system in terms of performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.6
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• pp.515-519
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• 2021

IEEE 1588 PTP is a precision time protocol in which two systems synchronize without the aid of GPS by exchanging packets including transmission/reception time information. In the time synchronization process, the propagation delay time can be calculated and the distance between the two systems can be measured using this. In this paper, we proposed a method to improve the distance measurement precision less than the modulation symbol period using the timing error information extracted from the preamble of the received packet. Computer simulations show that the distance measurement precision is proportional to the length of the preamble PN sequence and the signal-to-noise ratio.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.534-543
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• 2015

This paper introduces the time-misalignment error between multiple range measurements acquired by an onboard distance measuring equipment (DME) interrogator and proposes an efficient position determination method that can mitigate the negative effects of the time-misalignment error. The introduced time-misalignment error does not occur in conventional utilization of DME combined with VHF omnidirectional range (VOR). The proposed position determination method projects all the DME range measurements acquired irregularly during an interval to the same time instance where the aircraft position is determined. By the simulation utilizing a representative aircraft trajectory, it is shown that it is possible to estimate the horizontal position accurately without any changes of ground DME facilities.

• Journal of KIISE:Information Networking
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• v.34 no.5
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• pp.370-378
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• 2007

In wireless sensor networks (WSNs), thousands of sensors are often deployed in a hostile environment. In such an environment, WSNs can be applied to various applications by using the absolute or relative location information of the sensors. Until now, the time-of-arrival (TOA) based localization method has been considered most accurate. In the TOA method, however, inaccuracy in distance estimation is caused by clock drift and clock skew between sensor nodes. To solve this problem, several numbers of periodic time synchronization methods were suggested while these methods introduced overheads to the packet traffic. In this paper, we propose a new localization method based on multiple round-trip times (RTOA) of a signal which gives more accurate distance and location estimation even in the presence of clock skew between sensor nodes. Our experimental results show that the Proposed RTOA method gives up to 93% more accurate location estimation.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1023-1030
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• 2023

FMCW LiDAR system with robust target detection capabilities even under adverse operating conditions such as snow, rain, and fog is addressed in this paper. Our focus is primarily on enhancing the performance of FMCW LiDAR by improving the characteristics of the frequency-modulated laser, which directly influence range resolution, coherence length, and maximum measurement range etc. of LiDAR. We describe the utilization of an unbalanced Mach-Zehnder laser interferometer to measure real-time changes of the lasing frequency and to correct frequency modulation errors through an optical phase-locked loop technique. To extend the coherence length of laser, we employ an extended-cavity laser diode as the laser source and implement a laser interferometer with an photonic integrated circuit for miniaturization of optical system. The developed FMCW LiDAR system exhibits a bandwidth of 10.045GHz and a remarkable distance resolution of 0.84mm.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.154-159
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• 2019

When measuring the radiating noise of an underwater moving source, the range information between the acoustic source and the receiver is an important evaluation factor, and the measurement standards such as a receiver position, a moving source depth and a speed are set. Although there is a method of using the cross correlation as a method of finding the range of the underwater moving source, this method requires a time synchronization process. In this paper, we proposed the method to estimate the range by comparing the Doppler frequency difference of the theoretically calculated multipath signal with the Doppler frequency difference of the multipath signal estimated from the received signal. The proposed method does not require a separate time synchronization process. Simulations were performed to verify the performance, and the ranging error of the proposed method reduced by about 95 % than that of the conventional method.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.335-343
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• 2012

This paper presents an target tracking algorithm for fusion of radar and infrared(IR) sensor measurement data. Generally, fusion methods with Kalman filter assume that processing data obtained by radar and IR sensor are synchronized. It has much limitation to apply the fusion methods to real systems. A key point which is taken into account in the proposed algorithm is the fact that two asynchronous dissimilar data are fused by compensating the time difference of the measurements using radar's ranges and track state vectors. The proposed fusion algorithm in the paper is evaluated via a computer simulation with the existing track fusion and measurement fusion methods.