• 한국전자통신학회논문지
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• 제15권1호
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• pp.21-30
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• 2020

본 논문에서는 국제전기통신연합에서 권고하는 경로손실 예측모델을 이용하여 지상통제소와 무인 항공기 사이의 공대지 채널에 대한 경로손실을 예측하고, 이를 공대공 채널로 확장하여 중고도급 무인 항공기를 기반으로 하는 공중중계 시스템에 대한 네트워크 커버리지를 분석한다. 대기에 의한 경로손실 예측을 위해 한반도의 기후 및 지리적 인자를 활용하였다. 특히 국내의 강우량 및 유효지구반경 인자는 한국정보통신기술협회에서 공시한 실측 데이터를 활용하여 정확도를 높였다. 또한, 공중중계 송수신기는 현재 국내에서 개발 완료된 공용데이터링크 시스템의 주요지표를 활용하였다. 예측 결과로부터 임무 고도가 높아질수록 공중중계 시스템의 네트워크 커버리지가 넓어짐을 확인하였다.

• Journal of Platform Technology
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• 제9권1호
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• pp.3-14
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• 2021

Cognitive Radio network (CR) is a promising paradigm that helps the unlicensed user (Secondary User) to analyse the spectrum and coordinate the spectrum access to support the creation of common control channel (CCC). The cooperation of secondary users and broadcasting between them is done through transmitting messages in CCC. In case, if the control channels may get jammed and it may directly degrade the network's performance and under such scenario jammers will devastate the control channels. Hopping sequences may be one of the predominant approaches and it may be used to fight against this problem to confront jammer. The jamming attack can be alleviated using one of the game modelling approach and in this proposed scheme stochastic games has been analysed with more single users to provide the flexible control channels against intrusive attacks by mentioning the states of each player, strategies ,actions and players reward. The proposed work uses a modern player action and better strategic view on game theoretic modelling is stochastic game theory has been taken in to consideration and applied to prevent the jamming attack in CR network. The selection of decision is based on Q learning approach to mitigate the jamming nodes using the optimal MDP decision process

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.569-572
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• 2003

The broadband wireless access industry, which provides high-tate network connections to stationary sites, has matured to the point at which it now has a standard for second-generation wireless metropolitan area networks. IEEE Standard 802.16, with its WirelessMAN air interface, set the stage for widespread and effective deployments worldwide. This paper presents an implementation of media access control that can be applied to BWA (Broadband Wireless Access) system. Medium access control (MAC) is a key issue in multi-access networks where a common channel is shared by many users. The designed MAC prototype roughly consists of MAC Hardware and MAC Software. The MAC Hardware part includes timing process, MAC transmission control, MAC reception control, and CRC/HCS process. The MAC Software part includes control of MAC signaling, network interface, and Physical (PHY) control. The designed MAC protocol will be integrated with the PHY of BWA in future and we can test overall system performance of MAC and PHY.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1376-1379
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• 1996

In this paper a GPS receiver is developed using commercial chipsets. GP2010 RF front end and GP2021 Multi-channel correlator of GEC PLESSY are adapted in designing the receiver hardware. MC 68340 is used for controlling the correlator GP2021 and implementing the navigation processing. Also presented are some test results of the developed receiver whose software has an interrupt driven structure rather than common real-time kernel based structure.

• 전자공학회논문지B
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• 제28B권10호
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• pp.790-798
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• 1991

The congestion control methods of an integrated heterogeneous traffic multiplexer are studied. The real-time traffics have preemptive priority over nonreal-time traffics in capturing the common output link. Also real-time traffics are transmitted with bandwidth reduction when the nonreal-time traffics are over the buffer threshold. The proposed model formulated the system as a continous time Markov process and is analysed using matrix equation. Time delay and average number of used channel are applied for performance parameters. In this study, a new control method with the sizable buffer threshold is introduced and the optimal congestion control can be obtained.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2012년도 한국컴퓨터종합학술대회논문집 Vol.39 No.1(D)
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• pp.243-245
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• 2012

스펙트럼 자원이 비효율적으로 사용되는 무선 네트워크에서의 대안으로 여겨지는 CR (Cognitive Radio) 네트워크는 아키텍처에 따라 인프라 기반 네트워크와 CRAHNs (Cognitive Radio Ad Hoc Networks)으로 나눌 수 있다. CCC (Common Control Channel)조차 운영이 어려운 분산 CRAHNs에서 이를 해결하기 위해 제안된 기술들의 문제점을 제시하고 이를 개선하기 위한 주기적 스펙트럼 감지 정책을 제안해 OPNET을 사용해 SU (Secondary User) 처리량 측면에서 성능 검증하였다.

• 한국통신학회논문지
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• 제25권3B호
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• pp.423-430
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• 2000

Future microcellular systems will require distributed network control. A packet-switched network is suitable for this requirement. The packet reservation multiple access(PRMA) is a Reservation-ALOHA like protocol for wireless terminals to transmit packet speech to a base station. It allows spatially distributed users in cellular systems to transmit packeted voice and data to a common base station using a shared channel. In the existing PRMA, the problem is that the voice packets may collide with the data packets due to simultaneous channel access. the problem may be a major performance degradation factor to a voice and data mixed system. We propose a new PRMA method that integrates voice and data traffic efficiently by resolving the collision problem between data and voice packets. The proposed PRMA method gives a performance improvement than the existing PRAMA method in terms of voice packet dropping probability and data delay characteristic. From analytic results, we can confirm that the proposed PRMA method show a performance improvement than the existing PRMA protocol.

• 제어로봇시스템학회논문지
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• 제22권3호
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• pp.199-203
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• 2016

A brain-computer interface or BCI provides an alternative method for acting on the world. Brain signals can be recorded from the electrical activity along the scalp using an electrode cap. By analyzing the EEG, it is possible to determine whether a person is thinking about his/her hand or foot movement and this information can be transferred to a machine and then translated into commands. However, we do not know which information relates to motor imagery and which channel is good for extracting features. A general approach is to use all electronic channels to analyze the EEG signals, but this causes many problems, such as overfitting and problems removing noisy and artificial signals. To overcome these problems, in this paper we used a new optimization method called the Fruit Fly optimization algorithm (FOA) to select the best channels and then combine them with CSP method to extract features to improve the classification accuracy by linear discriminant analysis. We also used particle swarm optimization (PSO) and a genetic algorithm (GA) to select the optimal EEG channel and compared the performance with that of the FOA algorithm. The results show that for some subjects, the FOA algorithm is a better method for selecting the optimal EEG channel in a short time.

• 한국정보통신학회논문지
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• 제20권12호
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• pp.2387-2394
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• 2016

무선 센서 네트워크에서 대용량의 데이터를 효율적으로 전송하기 위해서 가장 적합한 채널을 선택하는 것이 중요하다. 무선 센서 노드가 사용할 채널을 고정하는 경우 주파수 부족 문제가 발생할 수 있고 다양한 환경을 지원하는데 큰 제약이 될 수 있다. 본 논문에서는 기존 무선 인지 라디오 네트워크에서 사용하는 공통 제어 채널 없이 두 노드가 서로 사용 가능한 채널을 찾기 위한 방식을 도입하여 무선 센서 네트워크의 채널을 효율적으로 이용하고자 한다. 기존 방식의 문제점으로 채널 설정 링크간의 간섭으로 인하여 성능이 크게 저하됨을 보이고 이를 개선하기 위해 임의 순차 알고리즘을 제안하였다. 컴퓨터 시뮬레이션 결과 제안 방식은 간섭으로 인한 비컨 패킷 수신 대기 시간을 현저하게 줄일 수 있어 간섭 링크 수가 증가할수록 다른 방식에 비해 50% 이상 빠르게 링크를 설정할 수 있다.

• Journal of Communications and Networks
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• 제17권1호
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• pp.12-20
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• 2015

Convolutional codes which are terminated by direct truncation (DT) and zero tail termination provide unequal error protection. When DT terminated convolutional codes are used to encode short messages, they have interesting error protection properties. Such codes match the significance of the output bits of common quantizers and therefore lead to a low mean square error (MSE) when they are used to encode quantizer outputs which are transmitted via a noisy digital communication system. A code construction method that allows adapting the code to the channel is introduced, which is based on time-varying convolutional codes. We can show by simulations that DT terminated convolutional codes lead to a lower MSE than standard block codes for all channel conditions. Furthermore, we develop an MSE approximation which is based on an upper bound on the error probability per information bit. By means of this MSE approximation, we compare the convolutional codes to linear unequal error protection code construction methods from the literature for code dimensions which are relevant in analog to digital conversion systems. In numerous situations, the DT terminated convolutional codes have the lowest MSE among all codes.