• 한국항공운항학회지
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• 제28권4호
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• pp.21-31
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• 2020

There are two to three helicopter accidents every year in Korea, representing 5.7 deaths per 100,000 flights. In this study, an analysis was conducted on helicopter accidents that occurred in Korea from 2005 to 2017. The accident analysis was based on the aircraft accident and incident report published by the Aircraft and Railway Accident Investigation Board. This Research analyzed the characteristics of accidents occurring in Korea caused by human error by pilots. Accident analysis was done by classifying the organization, flight mission, aircraft class, flight stage, accident cause, etc. Pilot's huan error was classified as Skill-based error, decision error and perceptual error in accordance with the HFACS taxonomy. The accidents caused by pilot's human error were classified into five categories: powerlines collision, loss of control, fuel exhaustion, unstable approach to reservoir, and elimination of tail rotor.

• 한국항공운항학회지
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• 제18권1호
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• pp.51-57
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• 2010

This study was to analyze the difference in pilot error by using the Signal Detection Theory. The task was to detect the targeted aircraft(signal) which is different shape from many other aircraft(noise). From the two experiments, we differentiated the task difficulty followed by change in noise stimuli. Experiment 1 was to search the signal stimuli(fighter plane) while the noise stimuli(cargo plane) were increasing. The results from the Experiment 1 showed the tendency to decrease the hit rate by increasing the number of noise stimuli. However, the false alarm rate was not increased. The sensitivity(d') showed quite high. In Experiment 2, a disturbance stimulus(helicopter) was added to noise stimuli. The result was generally similar to those of Experiment 1. However, the hit rate was lower than that of Experiment 1.

• 한국항공운항학회지
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• 제31권2호
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• pp.46-54
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• 2023

Helicopter pilots are required to perform many visual workloads in topographical avoidance, flight path modification and navigation, because helicopters operate at very low altitudes. The helicopter-specific instability also require the pilot to have precise perception and control. This has caused frequent human error in helicopter accidents. In Korea, two to three cases have occurred annually on average over the past 10 years, and this trend has not decreased. The purpose of this study was to identify human error risks in advance to prevent helicopter accidents and to help develop measures for missions and mission phases with high risk of human error. Through the study, the tasks and mission phases where accidents occur frequently were classified and the risk of human error was calculated for each mission phases. To this end, the task of frequent accidents during helicopter missions was first identified, detailed steps were classified, and the number of accidents was analyzed. Next, the AHP survey program was developed to measure the pilot's risk of human error and the survey was conducted on the pilots. Finally, the risk of human error by helicopter mission and by mission phases calculated and compared with the actual number of accidents.

• 한국통신학회논문지
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• 제33권8C호
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• pp.613-616
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• 2008

In this paper, a fine residual frequency offset estimation scheme is proposed for multiband orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) systems. The basic idea of our approach is based on the fact that two adjacent OFDM symbols carry the identical information in the MB-OFDM UWB system, thus removing the need of pilot symbols. The mean square error of the synchronization scheme is evaluated and simulation results are used to verify the effectiveness of the proposed estimator. When compared to the pilot-aided conventional estimator, the proposed estimator has a lower estimation error.

• 한국항공운항학회지
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• 제8권1호
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• pp.111-124
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• 2000

In this study, pilot's read-back errors were reviewed in terms of its cause and consequence while FAA tried to weigh a new initiative in the atc-pilot communication dispute in opposition of a majority of the aviation community by addressing an interpretive rule of 14CFR 91. Especially human factors in ATC communications were outlined with a view to suggest a line of recommendations for a successful accomplishment of safe flight in the busy terminal airspace.

• 한국통신학회논문지
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• 제29권6A호
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• pp.660-666
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• 2004

OFDM (Othogonal Frequency Division Multiplexing) 시스템과 CDMA (Code Division Multiple Access) 시스템의 결합 방식인 OFDM-CDMA 시스템에서는 파일럿 심볼을 이용하여 얻어진 채널 추정값으로 데이터 신호를 보상할 수 있다. 일반적으로 파일럿 심볼의 상관관계를 이용한 MMSE (Minimum Mean-Squared Error) 추정기를 사용하면 최적의 채별 추정값을 얻어낼 수 있으나 구조가 복잡하다는 단점이 있다. 본 논문에서는 파일럿 심볼에 대한 정보만을 이용하는 간단한 구조의 PA (Pilot-Aided) 알고리즘과 파일럿 심볼과 데이터 심볼의 정보를 모두 이용하는 PADD (Pilot-Aided Decision-Directed) 알고리즘을 변형하여 기존의 채널추정 방법보다 간단한 구조를 가지는 새로운 알고리즘을 제안하구 컴퓨터 모의실험을 통해 레일레이 다중 경로 페이딩 환경에서 수신기의 속도를 변화시키면서 성능을 평가한다. 모의 실험 결과를 살펴보면 제안된 채널추정 알고리즘이 기존의 PA 알고리즘보다 성능이 우수함을 확인할 수 있다.

• 한국통신학회논문지
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• 제32권2C호
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• pp.166-173
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• 2007

OFDM(Orthogonal Frequency Division Multiplexing) 시스템에서 채널추정을 위해 사용되는 파일럿에 발생하는 협대역 재밍은 시스템 성능에 나쁜 영향을 준다. 본 논문에서는 이 문제를 해결하기 위해 재밍된 파일럿을 검출하여 제거할 수 있는 방법을 제안한다. 또한, 한 개의 OFDM 심볼에서 재밍된 파일럿과 제거된 파일럿으로 인해 발생하는 평균 제곱 오류(Mean Squared Error, MSE)를 분석한다. 그리고, 실험을 통해 제안된 알고리즘을 사용한 채널추정 구조의 심볼 오류율(Symbol Error Rate, SER) 성능을 평가한다. 제안된 방법은 재밍 전력이 높은 환경에서 채널추정 성능을 향상시킬 수 있음을 확인하였다.

• 한국통신학회논문지
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• 제34권11C호
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• pp.1113-1121
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• 2009

본 논문에서는 기지국간 간섭이 큰 다중기지국 환경에서 multiple-input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) 시스템을 위한 파일럿 시퀀스 설계 방법 및 채널 추정 기법을 제안한다. 제안 파일럿 시퀀스의 경우 평균 제곱 오류치 (Mean Square Error)를 최소화시키며, 설계된 파일럿에 적합한 채널 추정 방법을 제안한다. 제안된 파일럿 시퀀스 및 채널 추정 기법은 추 시퀀스의 상관관계 특성을 이용해 설계되며 모의실험을 통해 설계된 파일럿 시퀀스를 이용한 채널 추정 기법이 기지국간 간섭을 완화에 효과적임을 보여준다.

• International Journal of Internet, Broadcasting and Communication
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• 제15권4호
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• pp.44-50
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• 2023

For Wi-Fi and IoT wireless systems, high-capacity wireless communication technology is being applied using MIMO OFDM. Because of virtu0al subcarriers in the practical MIMO OFDM system, the pilot subcarriers cannot be spaced equally. Thus, it is difficult to obtain a good mean square error (MSE) performance of the channel estimate. This paper proposes applicable methods and the newly discovered locations of pilot subcarriers in four transmitted antennas resulting in a good MSE performance with proposed optimization algorithms.

• 한국통신학회논문지
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• 제30권10A호
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• pp.949-957
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• 2005

In this paper, the performances of a single-user DS-UWB system applying two simple proposed channel estimation schemes are introduced, according to the newly updated DS-UWB PHY Layer standard from IEEE P802.15.3a. The performances of error control coding, different combining schemes in selective Rake receiver for DS-UWB system are analyzed. Both of the two channel estimation schemes using data-independent structure work well in DS-UWB system with few pilot bits. For the purpose of channel estimation and reduces the number of pilot bits, we apply a pilot symbol spreaded with $2{^8}-1\;or\;2{^9}-1$ periods of m-sequence for different channel estimation schemes.