• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.321-322
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• 2008

CSS(Chirp Spread Spectrum) technology adopt SDS-TWR algorithms of TOA(Time of Arrival) using velocity of specific medium and ToF(Time of Flight) to measure a distance, but this method always has a regular error on distance regardless of a real distance, as a result, in far distance, it decrease a error on distance relatively, but in near distance, it increase a error on distance relatively. in this paper, we propose and test new method measuring a distance more precisely in near distance using CSS and RSSI

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.7
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• pp.1-8
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• 2012

In this paper, we consider an efficient protocol for the multi-hop relay transmission on a sensor network which can be utilized in a ubiquitous environment. More specifically, we propose an efficient relaying protocol for the distance and position recognition on the proposed sensor network which performs with the differentially bi-orthogonal chirp spread spectrum (DBO-CSS) in the industrial, scientific and medical (ISM) bands. For an efficient networking access, we design and implement four different packet structures, zone information packet, hop information packet, tag information packet, and application serial packet. Additionally, we also propose an efficient position recognition algorithm. Finally, for verification of our proposed protocol's efficiency, we build the testbed system which consists of $15m{\times}15m$ multi-cell and 10 hops in the network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5B
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• pp.370-376
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• 2012

The CSS(Chirp Spread Spectrum) technology is used for developing various WPAN(Wireless Personal Area Network) application fields in general, and it can be adapted to implement localization systems especially using SDS-TWR(Symmetric Double Sided - Two Way Ranging). But the ranging errors are occurred in many practical applications due to some interferences by some experiments. Thus, the compensation algorithm for localization is required for developing localization applications. The suggested compensation algorithm that is named KF_EDR(Kalman Filter and Equivalent Distance Rate) for localization in order to reduce the ranging errors is suggested in this paper. The KF_EDR compensation algorithm for localization is mainly composed of the AEDR(Algorithm of Equivalent Distance Rate) and the Kalman Filter. It is confirmed that the improved error ratio of the KF_EDR are 10.5% and 4.2% compared with the AEDR algorithm in lobby and stadium. From the results, it is analyzed that the KF_EDR can be widely used for some localization system in ubiquitous society.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.914-919
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• 2010

It is confirmed that as the distance measurements accuracy of the SDS-TWR(Symmetric Double-Sided Two-Way Ranging) based on CSS(Chirp Spread Spectrum) is considerably degraded due to frequency interference and it causes to severe errors in the localization applications. In this paper, the compensation algorithm based on error rate offset of distance measurement ($CA_d$) is proposed for the purpose to reduce the ranging errors due to by the SDS-TWR ranging problems. The $CA_d$ measures the distance values between two nodes by means of 1m interval about 1~25m distances in the SDS-TWR, and compensates the distance values using the parameters related to the distance compensation. From the experiments, it is analyzed that the $CA_d$. have reduced the distance error to average 95cm and maximum 526cm, and the distance error by the $CA_d$ was below about 60cm in the 25m distances. In particular, the performance of the distance measurements accuracy by the $CA_d$ is very high in LOS(Line Of Sight) environments.

• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.219-227
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• 2021

This paper proposed an Orthogonal Frequency Division Multiplexing (OFDM) based biomimetic communication method using a dolphin whistle which covertly transmits communication signals to allies. The proposed method divides the dolphin whistle into several time slots corresponding to a number of OFDM symbols, and modulates the communication signal by mapping differential phase shift keying (DPSK) symbols into subcarriers that have the frequency bands of the dolphin whistle in each slot. The advantages of the proposed method are as follows: In the conventional Chirp Spread Spectrum (CSS) and Frequency Shift Keying (FSK) based biomimetic communication methods, the discontinuity of the frequency contour is large, but the proposed method can reduce the discontinuity. Even if the modulation order is increased, the degradation of the mimicking performance is small. The computer simulations demonstrate that the Bit Error Rate (BER) and mimicking performance of the proposed method are better performance than those of the conventional CSS and FSK.

• The KIPS Transactions:PartC
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• v.19C no.4
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• pp.239-246
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• 2012

The function of location estimation in WPAN has been studied and specified on the ultra wide band optionally. But the devices based on CSS(Chirp Spread Spectrum) specification has been used widely in the market because of its functionality, cheapness and support of development. As the CSS device uses 2.4GHz for a carrier frequency and the sampling frequency is lower than that of the UWB, the resolution of a timestamp is very coarse. Then actually the error of a measured distance is very large about 30cm~1m at 10 m depart. And the location error in ($10m{\times}10m$) environment is known as about 1m~2m. So for some applications which require more accurate location information, it is very natural and important to develop a sophisticated post processing algorithm after distance measurements. In this paper, we have studied extended Kalman filter with the frequency offsets of anchor nodes, and proposed a novel algorithm frequency offset compensated extended Kalman filter. The frequency offsets are composed with a variable as a common frequency offset and constants as individual frequency offsets. The proposed algorithm shows that the accurate location estimation, less than 10cm distance error, with CSS WPAN nodes is possible practically.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.213-219
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• 2013

Recently, with the rapid advancement in information and communication technology, indoor location-based services(LBSs) that require precise position tracking have been actively studied with outdoor-LBS using GPS. However, in case of a ship which consists of steel structure, it is difficult to measure a precise localization due to significant ranging error by the diffraction and refraction of radio waves. In order to reduce location measurement errors that occur in these indoor environments, this paper presents distance compensation algorithms that are suitable for a narrow passage such as ship corridors without any additional sensors by using UWB(Ultra-wide-band), which is robust to multi-path and has an error in the range of a few centimeters in free space. These improvement methods are that Pythagorean theory and adjacent node technique are used to solve the distance error due to the node deployment and distance variation analysis technique is applied to reduce the ranging errors which are significantly fluctuated in the corner section. The experimental results show that the number of nodes and the distance error are reduced to 66% and 57.41%, respectively, compared with conventional CSS(Chirp spread spectrum) method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.3
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• pp.258-272
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• 2010

The low-rate (LR) UWB is a promising technology for the ubiquitous sensor network (USN) due to its extremely low power consumption and simple transceiver implementation. However the limited communication range is a bottleneck for its widespread use. This paper deals with a new frame structure of class 4 active RFID multi-hop relay system based on ISO/IEC 18000-7 standard integrating with IEEE 802.15.4a LR-UWB PHY layer specification, which sets up a connection to USN. As a result of the vital importance of the coverage and throughput in the application of USN, further we analyze the performance of the proposed system considered both impulse radio UWB (IR-UWB) and chirp spread spectrum (CSS). Our simulation results show that the coverage and throughput are remarkably increased.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.467-470
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• 2009

본 논문에서는 유비쿼터스 기반 인프라를 이용한 실시간 유괴방지 시스템을 구축하였다. 급속한 사회 발전과 더불어 강력사건이 증가되고 있으며 그중에서 어린이 유괴 범죄 같이 질적으로 흉악한 범죄가 해마다 증가되고 있는 실정이다. 이러한 유괴 범죄를 예방하기 위하여 현재 GPS(Global Positioning System)을 이용한 위치인식 기술 및 이동통신 기지국을 이용한 위치인식 기술이 사용되고 있다. 단순히 위치인식 기술은 위험상황이 발생하였을 때, 상황을 정확히 인지하기 어려워 유괴된 어린이 44%가 1시간 이내 사망하고 74%가 3시간 이내 사망 한다는 통계를 감안하면 기존 시스템은 어린이 생명 보호 능력에 한계가 있다. 본 연구에서는 유비쿼터스 도시 기반 인프라를 구축하여 WPAN(Wireless Personal Area Network)환경에서 RF만으로 거리 측정이 가능한 IEEE 802.15.4a의 ISM Band CSS(Chirp Spread Spectrum)방식을 이용하여 보다 저 전력으로 정확한 위치정보 시스템을 적용하였다. 이에 CSS방식을 통하여 얻은 위치정보를 지능형 CCTV와 융합하여 CCTV가 단말기 위치로 자동 초점하는 시스템을 구성하였다. 도시통합운영센터에서 상황을 정확히 인지하고 신속하게 출동할 수 있도록 단말기 위치를 지속적으로 요원의 PDA 및 핸드폰으로 통보하고 현장 주변의 미디어 보드 표시와 음성 경고로 경찰의 적절한 대응 및 주변의 도움을 받을 수 있는 시스템을 구성하였다.

• 전자공학회논문지 IE
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• v.47 no.2
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• pp.60-65
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• 2010

In this paper, we propose a dual-band filtering method optimized to DBO-CSS systems which are alternatively transmitted in low and high bands. The conventional channel filter which passes entire signal bandwidth causes a problem that excessive noise in neighboring sub-band is added while one of signals in two sub-bands is received. The dual-band filtering proposed in this paper can overcome the performance degradation in the conventional filtering method without increase of hardware complexity. The proposed method is based on two filters to be matched with DBO-CSS signals receiving alternatively and can exclude the undesired noise in neighboring sub-band. Simulation results for the proposed method show better performance about 2.5dB than the conventional one.