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GPS 재방송 재밍신호 검출을 위한 통합 의사잡음신호를 사용한 확장된 ELP 기법
유승수(Seungsoo Yoo),염동진(Dong-Jin Yeom),지규인(Gyu-In Jee),김선용(Sun Yong Kim) 제어로봇시스템학회 2016 제어·로봇·시스템학회 논문지 Vol.22 No.6
This paper proposes a repeat-back jamming signal detection scheme that utilizes a combined pseudo random noise signal that is effective for processing a global positioning system (GPS) repeat-back jamming signal with the early minus late phase scheme to alleviate any existing multipath signal detection. The proposed scheme uses the combined pseudo random noise signal to treat repeat-back jamming signals like similar multipath signals and can effectively detect a repeat-back jamming signal by applying the early minus late phase scheme to a combined pseudo random noise signal. Through a Monte-Carlo simulation, the detection probability of the proposed scheme is better than the one of the conventional scheme under low jamming to signal power ratio.
대역제한 백색잡음 재밍환경에서 GPS L1 C/A신호를 위한 유효 반송파 대 잡음 전력비 추정비의 CRLB
유승수(Seungsoo Yoo),염동진(Dong-Jin Yeom),지규인(Gyu-In Jee),김선용(Sun Yong Kim) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.8
In this paper, we derive the CRLB (Cramer-Rao Lower Bound) of effective carrier-to-noise power ratio (C/N?) estimation for a GPS (Global Positioning System) L1 C/A (Coarse/Acquisition) signal under band-limited white noise jamming environments. The quality of a received GPS signal is commonly described in terms of its C/N?, implying that the noise is white and thus can be described by scalar noise density. However, if some intentional interference is received to a victim GPS receiver, then the C/N? is no longer the efficacious performance indicator. The correct and straightforward measurement to analyze the receiving situation is the effective C/N?. In this paper, we consider a band-limited white noise jamming whose bandwidth is 2MHz and is the same as one of the first null-to-null bandwidth of the GPS L1 C/A signal.
GNSS 수신기를 위한 낮은 복잡도를 갖는 새로운 반송파 대 잡음 전력비 추정기법
유승수(Seungsoo Yoo),백지현(Jeehyeon Baek),염동진(Dong-Jin Yeom),지규인(Gyu-In Jee),김선용(Sun Yong Kim) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.7
The carrier-to-noise power ratio is a key parameter for determining the reliability of PVT (Position, Velocity, and Time) solutions which are obtained by a GNSS (Global Navigation Satellite System) receiver. It is also used for locking a tracking loop, deciding the re-acquisition process, and processing advanced navigation in the receiver subsystem. The representative carrier-to-noise power ratio estimation schemes are the narrowband-wideband power ratio method (NW), the MM (Moment Method), and Beaulieu’s method (BL). The NW scheme is the most classical one for commercial GNSS receivers. It is often used as an authoritative benchmark for assessing carrier-to-noise power estimation schemes. The MM scheme is the least biased solution among them, and the BL scheme is a simpler scheme than the MM scheme. This paper focuses on the less biased estimation with low complexity when the residual phase noise remains, then proposes a novel carrier-to-noise power ratio estimation scheme with low complexity for GNSS receivers. The asymptotic bias of the proposed scheme is derived and compared with others, and the simulation results demonstrate that the complexity of the proposed scheme is lowest among them, while the estimation performance of the proposed scheme is similar to those of the BL and MM schemes in normal and high gained reception environments.
상관 함수의 기울기 차에 기반한 GNSS의 부호 추적 기법
유승수(Seungsoo Yoo),유승환(Seung Hwan Yoo),정다해(Dahae Chong),안상호(Sangho Ahn),윤석호(Seokho Yoon),김선용(Sun Yong Kim) 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.6C
위성 항법 시스템은 (global navigation satellite system, GNSS) 통신 물리계층으로 직접 수열 확산 대역 (direct sequence/spread spectrum, DS/SS) 시스템을 사용하고 있다. DS/SS 시스템은 확산된 정보를 복원하기 위해 한 칩(chip) 또는 그 이하로 동기를 맞추는 획득 단계와 정확한 동기를 결정하고 유지하는 추적 단계를 수행한다. 가장 널리 알려진 추적 기법은 상관 값의 대칭성을 이용해 부호를 추적하는 -DLL이다 (single delta delay lock loop). 여기서, Δ는 이른-늦은 상관 값의 상관 시간 옵셋 간격을 뜻한다. Δ-DLL은 이상적인 환경에서 최적 부호 추적 기법이다. 그러나 이 기법은 다중경로 환경에서 상관 함수의 대칭성이 깨짐으로 인해 판별기 출력이 비대칭으로 나타나기 때문에 큰 추적 편이를 갖는다. 추적 편이는 정확한 동기 시점과 추적이 완료되어 결정한 동기 시점의 차이를 의미한다. 이러한 추적 편이를 감소시키기 위한 기법으로 작은 Δ를 사용한 Δ-DLL과 두 개의 Δ-DLL을 조합한 Δ<SUP>(2)</SUP>-DLL이 (double delta DLL) 제안되었다. 그러나 두 기법 모두 여전히 추적 편이가 존재하며, 작은 Δ를 사용하기 때문에 추적 단계의 동적 영역이 줄어들어 정확한 획득 단계가 요구되는 단점을 갖고 있다. 본 논문에서는 추적 편이를 효과적으로 줄이면서도 정확한 획득 단계가 요구되지 않는 상관 값의 최대 기울기 변화에 기반한 추적 편이 감소 기법을 제안한다. The global navigation satellite system (GNSS) is using a direct sequence/spread spectrum (DS/SS) modulation. In order to recover the information data, the DS/SS system first performs a two-step synchronization process: acquisition and tracking. The acquisition process adjusts the phase difference between the received and locally generated acquisition sequences within ± Tc/2 or less, where Tc is the chip period. The tracking process performs fine synchronization. In this paper, we focus on the tracking issue. The single delta delay locked loop (Δ-DLL) is the optimal tracking scheme for a GNSS in the absence of multipath signals, where Δ means the spacing between the early and late correlation time offset. In the multipath environments, however, the Δ-DLL suffers from huge estimation bias (denoted by β) caused by distorted correlation values. Although some modified schemes such as a Δ-DLL with a narrow Δ and a double delta DLL (Δ<SUP>(2)</SUP>-DLL) were proposed to reduce the estimation bias, they cannot remove the estimation bias completely and need more accurate acquisition process. This paper proposes a novel tracking scheme that can dramatically reduce the estimation bias, using the maximum slope change among the correlation outputs.
가상행성 섭동력을 고려한 긴 주기 GPS 위성궤도예측기법
유승수(Seungsoo Yoo),이정혁(Junghyuck Lee),한진희(Jin Hee Han),지규인(Gyu-In Jee),김선용(Sun Yong Kim) 제어로봇시스템학회 2012 제어·로봇·시스템학회 논문지 Vol.18 No.11
The purpose of this paper is to analyze GPS (Global Positioning System) satellite orbital mechanics, and then to propose a novel long-term GPS satellite orbit prediction scheme including virtual planet perturbation. The GPS orbital information is a necessary prerequisite to pinpointing the location of a GPS receiver. When a GPS receiver has been shut down for a long time, however, the time needed to fix it before its reuse is too long due to the long-standing GPS orbital information. To overcome this problem, the GPS orbital mechanics was studied, such as Newton’s equation of motion for the GPS satellite, including the non-spherical Earth effect, the luni-solar attraction, and residual perturbations. The residual perturbations are modeled as a virtual planet using the least-square algorithm for a moment. Through the modeling of the virtual planet with the aforementioned orbital mechanics, a novel GPS orbit prediction scheme is proposed. The numerical results showed that the prediction error was dramatically reduced after the inclusion of virtual planet perturbation.
MBOC(6,1,4/33) 신호의 다중경로 영향 완화를 위한 새로운 Strobe 펄스 설계
유승수(Seungsoo Yoo) 제어로봇시스템학회 2020 제어·로봇·시스템학회 논문지 Vol.26 No.11
In this paper, we propose a novel strobe pulse to mitigate the multipath effect of MBOC (6,1,4/33) signal and analyze its performance. By additionally modulating a passband Direct Sequence/Spread Spectrum (DS/SS) signal with a Binary Offset Carrier (BOC) sub-carrier, the signal band can be moved to a desired band, thereby increasing frequency efficiency. In addition, the correlation characteristics of the correct code synchronization point are improved, so that the multipath effect can be reduced to compare with the existing Binary Phase Shift Keying (BPSK) modulated signal. However, the multipath effect is still one of the major performance limitations of the Global Navigation Satellite Systems (GNSSs). A conventional scheme to mitigate multipath effects of GNSS is the Strobe pulse technique. In this paper, we design a new strobe pulse that can effectively mitigate the multipath effects of MBOC (6,1,4/33) signals, and multipath mitigation in the 2-Ray model, a representative channel environment to assess the multipath mitigation performance by computer-based simulation. In order to compare the performance of the proposed new strobe pulse, the W2 pulse scheme with similar implementation complexity is considered. The W2 pulse technique is the one of the Strobe pulse technique for BOC signal. Based on the output of the discriminator in multipath free environment, the pull-in range of the W2 pulse technique is about 0.2 chips, whereas the proposed scheme is about 0.6 chips, which is about 3 times wider. And the false-lock point of the proposed scheme is less than about 20% to compare the W2 scheme. In the same environment, the multipath error envelope of the W2 and the proposed schemes is shown, and both techniques are affected only by the closed-in multipath signal. Among them, the proposed scheme has significantly lower multipath errors due to the closed-in multipath signal compared to the W2 technique, and the maximum value of the proposed scheme based on the running average of the multipath errors is about 32% compared to the W2 scheme.
유승수(Seungsoo Yoo),신천식(Cheon Sig Sin),김선용(Sun Yong Kim) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.6
본 논문에서는 GPS (Global Positioning System) L1 C/A (Coarse/Acquisition) 신호에 대한 대표적인 상용 수신기 가운데 하나인 u-Blox사의 EVK-M8N 수신기의 AM/CW (Amplitude Modulation/Continuous Wave), Chirp, FM (Frequency Modulation) 재밍에 대한 영향을 분석한다. GPS L1 C/A 신호는 고정된 실외 안테나로 수신한 신호를 LabSat3로 저장한 후 재생하고, 재밍 신호는 USRP (Universal Software Radio Peripheral) N210으로 생성한다. 재밍 영향의 단계는 추적 결정(tracking lock)에 따른 가시 GPS 위성 수로 구별했으며, 각 장비를 유선으로 연결하여 신호 소실 시점부터 복원 시점까지의 소요 시간을 복원 시간으로 정의해 이를 확인한다. 재밍 별 복원 시간은 AM/CW 재밍은 약 35.72초, Chirp 재밍은 약 34.24초, FM 재밍은 약 86.30초였다.