• 한국통신학회논문지
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• 제35권6B호
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• pp.921-929
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• 2010

그룹통신은 이동통신 환경에서 사용할 수 있는 중요한 응용분야의 하나이다. PoC(Push to Talk over Cellular)는 셀룰러 전화망에서 사용되는 그룹통신을 위한 서비스이며, 단방향(half duplex) 통신으로 통화 버튼을 한 번 누름으로써 한 사용자가 그룹에 속한 다수에게 통화를 할 수 있게 한다. 이러한 서비스를 바탕으로 본 논문에서는 모바일 와이맥스(802.16e) 네트워크에서 그룹통신 프로토콜을 설계하였다. 또한 설계된 프로토콜의 검증과 성능평가를 위해 시뮬레이션을 실행하였다. 성능평가 결과 개발된 그룹통신이 안정적으로 동작함을 확인할 수 있었으며, 성능이 허용 범위 내에서 정상적으로 동작함을 확인할 수 있었다.

• 한국산학기술학회논문지
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• 제10권3호
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• pp.542-546
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• 2009

본 논문은 신경망을 이용한 간섭 신호 제어로써 합성 다층 퍼셉트론에 입각하여 셀룰라 이동통신에서의 수신된 신호들을 역전파 학습알고리즘을 이용하여 검파하는 것에 대하여 소개하였다. 그리고 컴퓨터 시뮬레이션 결과를 통하여 co-channel간섭과 협대역 간섭의 실제 음색에서 기존에 쓰여진 Rake수신기보다 더 낮은 비트 오차 확률을 가지는 NNAC(neural network adaptive correlator)에 대하여 분석 고찰하였다.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권4호
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• pp.160-166
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• 2002

Since conventional mobile robot control with one module has limitation to solve complex problems, there have been a variety of works on combining multiple modules for solving them. Recently, many researchers attempt to develop mobile robot controllers using artificial life techniques. In this paper, we develop a mobile robot controller using cellular automata based neural networks, where complex tasks are divided to simple sub-tasks and optimal neural structure of each sub-task is explored by genetic algorithm. Neural network modules are combined dynamically using the action selection mechanism, where basic behavior modules compete each other by inhibition and cooperation. Khepera mobile robot simulator is used to verify the proposed model. Experimental results show that complex behaviors emerge from the combination of low-level behavior modules.

• 센서학회지
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• 제18권5호
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• pp.337-342
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• 2009

This paper describes a robust mobile u-healthcare system with multiple physiological signs measurement capability in real time with integration of WSN(wireless sensor network) technology and CDMA(code division multiple access) network. A cellular phone receives health data in WSN and performs local physiological signs analysis at a phone processor, and then transmits abnormal data to server for further detail or precise health signal evaluation by a medical doctor over a CDMA network. Physiological signs of the patients are continuously monitored, processed and analyzed locally at cellular phone process to produce useful medical information for diagnosis and tracking purposes. By local simple analysis in cellular phone processor we can save the data transmission cost in CDMA network. By using the developed integrate ubiquitous healthcare service architecture, patients can realize self-health checking so that the prevention actions can be taken earlier. Appropriate self-monitoring and self-management can cure disease and relieve pain especially for patients who suffer from chronic diseases that need long term observation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.10-14
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• 2004

When providing flexible data transmission for future CDMA(Code Division Multiple Access) cellular networks, problems arise in two aspects: transmission rate. This paper has proposed an approach to maximize the cellular network capacity by combining the genetic transmission rate allocation and a rapid power control algorithm. We present a genetic chromosome representation to express call drop numbers and transmission rate to control mobile's transmission power levels while handling their flexible transmission rates. We suggest a rapid power control algorithm, which is based on optimal control theory and Steffenson acceleration technique comparing with the existing algorithms. Computer simulation results showed effectiveness and efficiency of the proposed algorithm Conclusively, our proposed scheme showed high potential for increasing the cellular network capacity and it can be the fundamental basis of future research.

• 제어로봇시스템학회논문지
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• 제18권4호
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• pp.375-383
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• 2012

Together with the GPS-based approach, geolocation through mobile communication networks is a key technology for location-based service. Since the Mobile WiMAX system is considered as a candidate for fourth-generation mobile systems, it is important to investigate its location capability. The geolocation of Mobile WiMAX can be realized when the preamble symbols in the down-link channel are appropriately used for a TDOA (Time-Difference-of-Arrival) approach. However, the cellular structure of Mobile WiMAX inevitably generates co-channel interference, and it is difficult for the mobile terminal to acquire distance measurements from multiple base stations. Therefore, for geolocation via multilateration using the Mobile WiMAX network, it is very important to increase hearability. This paper proposes a geolocation method for Mobile WiMAX which employs interference cancellation and preamble signal overlapping for the enhancement of hearability. A novel interference cancellation strategy for complex-valued Mobile WiMAX signals is presented which has an iterative structure. Simulation results show that the proposed geolocation method provides the user's position with an accuracy of less than 20 m through the Mobile WiMAX cellular network if there is no multi-path or NLOS (None-Line-of-Sight).

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 The Third Asian Fuzzy Systems Symposium
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• pp.181-184
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• 1998

CAM-Brain is a model to develop neural networks based in cellular automata by evolution, and finally aims at a model as and artificial brain,. In order to show the feasibility of evolutionary engineering to develop an artificial brain we have attempted to evolve a module of CAM-Brain for the problem to control a mobile robot, In this paper, we present some recent results obtained by analyzing the behaviors of the evolved neural module. Several experiments reveal a couple of problems that should be solved when CAM-Brain evolves to control a mobile robot. so that some modification of the original model is proposed to solve them. The modified CAM-Brain has evolved to behave well in a simulated environment, and a thorough analysis proves the power of evolution.

• 산업기술연구
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• 제27권A호
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• pp.131-139
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• 2007

The recent advance in wireless network technologies has enabled the streaming media service on the mobile devices such as PDAs and cellular phones. Since the wireless network has low bandwidth channels and mobile devices are actually composed of limited hardware specifications, the transcoding technology is needed to adapt streaming media to given mobile devices. Futhermore owing to the diversity of bandwidth in the wireless network by reason of mobile users' movements and environments, it is difficult to provide stable QoS. In this paper, the autonomic multimedia transcoding system is proposed in order for users to provide network adaptive QoS. Our proposed system is based on the estimation of available bandwidth in wireless network for seamless multimedia streaming service. The proposed system is designed and implemented for various mobile clients. In experiments, we evaluate its seamless multimedia streaming and the adaptation transcoding bit rate according to the changes of bandwidth in wireless network.

• 대한산업공학회지
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• 제29권4호
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• pp.312-320
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• 2003

Recently there is a growing interest in mobile cellular network providing multimedia service. However, the link bandwidth of mobile cellular network is not sufficient enough to provide satisfactory services to users. To overcome this problem, an adaptive framework has been proposed. In this study, we propose a new method of estimating DPR(Degradation Period Ratio) in an adaptive multimedia network where the bandwidth of ongoing call can be dynamically adjusted during its lifetime. DPR is a QoS(Quality of Service) parameter which represents the ratio of allocated bandwidth below a pre-defined target to the whole service time of a call. We improve estimation method of DPR using DTMC(Discrete Time Markov Chain) model by calculate mean degradation period, degradation probability more precisely than in existing studies. Under Threshold CAC(Call Admission Control) algorithm, we present analytically how to guarantee QoS to users and illustrate the method by numerical examples. The proposed method is expected to be used as one of CAC schemes in guaranteeing predefined QoS level of DPR.

• 한국시뮬레이션학회논문지
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• 제13권2호
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• pp.65-73
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• 2004

The capability to provide the network service must survive even if a significant network system element is disrupted. To sustain the network service under the system failure, network survivability mechanisms minimizing the impact of failures are needed. Also, since the mobile network has its unique characteristic, the survivability scheme for the vulnerability of the mobile network is required. This paper proposes a survivability scheme to support the reliable service of the wireless access point level (BS-base station system). By the survivability scheme, the mobile network can use an overlap BS of the cellular network architecture after a BS system failure. We analyze the performance of the proposed scheme using Markov model. Also, a computer simulation is used for the scheme analysis. The proposed scheme shows that the service of the mobile network can be provided under the BS system failure.