• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.10
• /
• pp.2205-2218
• /
• 1997

We implement the CARMA-M (Collision Avoidance Radio Multiple Access-Mobile) protocol and DMP (Data-radio Multiplex Protocol) with a client/server architecture for a wireless communication netowrk. These protocols support a data transfer function between a remote computer and a mobile portable computer with a wireless modem which are proposed by dataradio in U.S.A. With the review and analysis of the proposed protocol, the impelementation methods of DMP, CARMA-M and LLC to interface the protocols are presented. Moreover the FEC technique is added to find and correct the errors generated in communication. The simulation method of a wireless network using wires is also shown to verify the implemented protocols.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.7B
• /
• pp.455-462
• /
• 2007

The GTS(Guaranteed Time Slot) of IEEE802.15.4 standard, which is the contention free access mechanism, has some problems such as the limited number of deployed devices, the low channel utilization and the service confirm delay. The proposed Cyclic-CFA(Contention Free Access) scheme is a modified polling algorithm that allows a large number of devices to be served Contention Free Access without polling packets. The Cyclic-CFA scheme improves the channel utilization dramatically and also reduces service delay time.

• Proceedings of the KIEE Conference
• /
• 1999.07b
• /
• pp.945-947
• /
• 1999

첨단의 자동화 시스템을 구축하기 위해서는 각 필드기기에서 생산되는 정보들을 적절한 형태로 가공하여 적시에 필요한 공정으로 제공하여 줄 수 있는 지능형 센서 및 필드기기의 도입이 필요하다. 이러한 필드기기들이 유기적으로 정보를 교환하고 공유하기 위해서는 통신망 시스템을 구축할 필요가 있다. 필드버스는 자동화 및 분산 제어 시스템의 컴퓨터 통신망 계층구조에서 최하위 계층 기기들 간에 실시간 통신을 제공하는 산업용 통신망이다. 본 연구에서는 통신용 프로세서인 Mc68360을 기반으로 하여 필드버스의 일종인 Profibus의 물리계층과 데이터링크계층 프로토콜을 구현하였다. 물리계층은 프로세서의 UART 통신 기능과 RS-485칩을 사용하여 구현하고, 데이터링크계층 프로토콜은 프레임 분석과 송수신, 에러처리, 흐름제어, 매체접속권한 관리 등의 기능을 소프트웨어로 구현하였다. 또한 지능형 센서 본래의 목적중의 하나인 원격관리 기능을 위하여 각 필드기기의 노드 주소, 타이머 값 등의 통신 파라미터를 원격 마스터에서 설정할 수 있도록 관리계층의 기능을 추가하였다. 본 연구에서는 각각 하나의 노드기능을 담당하는 여러 개의 보드들로 구성된 testbed를 구축하고, 다양한 통신환경에서 초기화, 정상, 비정상 상태 등의 동작을 실험하였으며, 이를 통하여 지능형 센서용 필드버스의 데이터링크계층 프로토콜이 정상적으로 동작됨을 확인하였다.

• 전자공학회논문지 IE
• /
• v.43 no.2
• /
• pp.75-79
• /
• 2006

Blind techniques without the help of training sequences are able to detect the information signal which has the minimal information of desired user. In this paper, we proposed the blind multiuser detector using the hybrid cost function to cancel the multiple user interference in direct sequence code division multiple access systems. The cost function of proposed blind multiuser detector is the hybrid type which joints both least mean square(LMS) algorithm and least mean fourth(LMF) algorithm. We evaluate the bit error rate(BER) performance of proposed blind multiuser detector under additive white Gaussian noise channel. Simulation results show that the proposed blind detector has an about 3dB of signal to noise ratio more than blind minimum output energy(MOE) multiuser detector under existing active user 20.

• The Journal of Information Technology
• /
• v.6 no.4
• /
• pp.81-91
• /
• 2003

This paper is concerned with the implementation of power line communication system with 9.6Kbps. This system is suitable to establish the smart home using the power line having been installed in house. In the suggested power line communication system, we use the chirp signal with a linearity and spread spectrum frequency band of 100KHz~200KHz. We had the performance experiment for the implementation system. The experiment was achieved in the pseudo load network similar to real circumstance of power line communication. As the result, the communications under the circumstance were accomplished satisfactorily. We confirmed that the suggested 9.6Kbps power line communication system with the Chirped-SS method had the performance enough to commercialize the smart home.

• Proceedings of the Korea Inteligent Information System Society Conference
• /
• 2006.06a
• /
• pp.381-384
• /
• 2006

인터넷과 IT 인프라의 증가는 인터넷 기반의 전자상거래 시스템의 성장을 주도하였고, 이와 관련된 새로운 형태의 서비스가 나타나는 계기가 되었다. 그러나, 현재 전자상거래 서비스는 구매자가 웹에 접속하여 인터넷 쇼핑몰에 보이는 상품을 선택하여 결제 및 상품을 수신하는 방식으로 이루어진다. 또한 구매 판단을 결정할 때 최저가격 외에 신속한 배송, 부가 서비스 등의 다양한 의사결정 요소가 있음에도 불구하고, 인터넷 쇼핑몰에서 제시한 최저가의 판단요소에 의존함으로 구매자가 수동적인 입장이 된다. 따라서, 본 논문에서는 이러한 문제점을 해결하기 위해 상호간에 의견교환 및 사용자가 정한 우선순위에 따른 판단을 효과적으로 할 수 있는 서비스인 게임이론 기반의 지능모델을 제시한다 게임이론은 전통적으로 경제문제 협상과 정치문제 협상, 워 게임 등에 적용되었다. 본 연구에서는 이 점에 착안하여 게임이론 알고리듬을 이용하여 e-Commerce를 위한 지능모델에 적용하여, 기존의 수동적이고 사용자의 취향에 따라 다양한 의사결정 요소를 선택 할 수 없었던 문제를 해결한다.

• The Journal of the Acoustical Society of Korea
• /
• v.19 no.3
• /
• pp.57-62
• /
• 2000

In recent, the innovative improvement of a internet and computing environment make users desire the capability of processing information in real time. In this paper we implement a PC-to-PC real time multi-user communication system on the internet environment using the efficient algorithm for a real time processing and the MFEG-4 CELP codec which can be used for a low bit-rate coding from 6 to 24kbps. The implemented system produces a compressed bit-streams with the MPEG-4 CEU Mode-I 18200bps mode. There is 5 frames for a package and 1 frame has 160 samples. We can use this system to communicate with 4 users simultaneously in real time. The system is designed and examined on the Windows operating system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.05a
• /
• pp.483-486
• /
• 2001

Home Networking is the last connection point for global information and telecommunication infrastructure establishment. Information infrastructure has been constructed to matured extent so far, and then the enhancement of data transferring performance and high speed capacity in houses tame to the problem to solve as the last communicating area. In addition, to hold such communicating rapacity in houses, the customer premises technology is important as the framework. In this paper, introducing various home networking technologies, prospect of premise technology is reviewed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.2
• /
• pp.207-217
• /
• 1993

In this paper, knowing a priori probability of phase offset between transmitted codes and reference codes in the receiver, we construct the state diagram of acquisition process of the direct sequence spread-spectrum communication system using the expanding window search. The scannings are performed from the cell with higher probability code epoch synchronization to that with lower one. We expand window size from initial value by r times of its previous size in each search, construct the corresponding the state diagrams, and derive average synchronization time using the Markov process and Mason's gain formula. Average synchronization times versus number of search n and detection probability $P_d$ are calculated.

• Korean Journal of Food Science and Technology
• /
• v.22 no.6
• /
• pp.686-689
• /
• 1990

For the monitoring of kimchi fermentation states, pressure detecting sensor and monitoring device were designed and fabricated. The system was consisted of an air tight fermenting tube(31.5 ml), strain gauge type pressure sensor and signal processing device built with operational amplifier and A/D converter, and interfaced to personal computer. Chiness cabbage kimchi was fermented in the plastic container($150{\times}220{\times}160mm$) at $25^{\circ}C\;and\;30^{\circ}C$. The fermentation was monitored with fermenting tubes containing kimchi. The pressure based kimchi fermentation curve was constructed and showed a typical kimchi curing curve having 2 stepwise pressure increasing pattern.