• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3B
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• pp.181-188
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• 2012

In this paper, the time slot assignment algorithm, which is based on various transmission interval in TDMA DAMA communication system, has been proposed. The performance of the proposed algorithm and the random assignment algorithm is compared through computer simulations. The simulation results show that the new algorithm can enhance the efficiency of time slot usage much more than the random assignment algorithm. Especially, the lower the congestion of the network is, the higher the efficiency of time slot usage for short transmission interval is.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.267-273
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• 2012

The short-range communication module was developed in this paper which is suitable for the point-to-multipoint circumstances of 40 terminals communicating frequently in about 50 meters. The media access control layer of this communication module using asynchronous time-division multiplexing provides a fast and robust performance even in the worst case of simultaneous transmission events, and low packet error rate was measured a in LOS (Line-of-sight) circumstance by adding the function of acknowledge response to media access control layer. The difference test was carried out in order to measure the performance of point-to-multipoint communication. Two communication modules are respectively measured and graphed in 10 branches to 40 branches. The communication module developed in this paper showed a faster performance than the commercial Zigbee module in the specific case presented in this paper. Especially, in over 20 branches showed wide differences of the transmission speed. This results is caused by more network overhead of Zigbee whose wider applications needs the network layer and applicaiton layer besides media access control layer. Also, the asynchronous time-division multiplexing proposed in this paper are more suitable than CSMA-CA of Zigbee module when a lot of module ought to be frequently communicated in small area.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1129-1137
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• 2012

The wireless link of tactical datalink system provides a communication network to share digitalized tactical data in real-time. Also MAC(Multiple Access Control) of this system is subject to TDMA or CSMA according to a operated circumstance of target nodes to exchange the data reliably. In this paper, we verify the operability when we use CSMA scheme based on MIL-STD-188-220 in tactical datalink system which is basically designed with TDMA, and provide a mathematical analysis scheme to verify the operability and performance. Finally, by implementing CSMA scheme to a tactical datalink equipment we obtain practical results which can be compared with theoretical results.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.5
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• pp.640-648
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• 2018

Time division wireless communication in tactical MANET is attractive to deliver both high data rates and long-range coverage, and to provide scheduled QoS to mission participants. This paper is about the time synchronization issue of multi-mission USV in tactical MANET. As USV communication coverage becomes longer, the synchronization error also becomes higher; therefore, which results in link disconnection, and consequent failures of reconnection because base station cannot configure necessary parameters over long-distant terminal. We propose a range adaptive time synchronization method to compensate for synchronization errors. The issue of long-range time synchronization problem was identified during maritime communication tests, and we verified the proposed method through analyses of both indoor and outdoor test results.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.489-496
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• 2018

In this paper, a performance comparison of dynamic TDMA and fixed TDMA in tactical data link system is conducted. The performance metric include: delay, queue size and system throughput. To perform comparison of two TDMA schemes, we adopt the modified M/D/1 queueing model. Computer simulation is also performed to verify conducted analytical results.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.1
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• pp.50-56
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• 2016

This paper is about the implementation of the OFDM-based border guard/reconnaissance communication terminal systems. We have implemented Real-time Dynamic DL/UL symbol rate control function using the DL-MAP message, and proposed error detection method caused by malfunctioning and timing optimization method. The proposed scheme detects the variable rate symbol decoding timing without increasing additional physical layer logic, and also provides a wide variety of DL/UL data transfer rate. Furthermore, the proposed scheme applies to the current border guard/reconnaissance equipment and confirms a operation performance through field tests and demonstration at home and abroad.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.7
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• pp.747-749
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• 2016

We consider a time-division multiple-access relay channel (MARC), in which two source nodes (SNs) transmit data with different data rate to a destination node (DN) with the help of a relay node (RN) using network coding (NC). However, due to its asymmetric data rate, the RN cannot combine the received bits by XOR NC. In this paper, we compare with the problem of asymmetric data rates by using zero padding and hierarchical 16QAM.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.9 no.2
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• pp.91-99
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• 2001

오늘날 위성항법, 위성통신을 이용한 항공항법감시의 새로운 변화 가운데 국제민간항공기구(ICAO)에서 VDL(VHF Digital Link) Mode 4로 채택된 STDMA (Self-organized Time Division Multiple Access)에 관심이 증대되고 있다. 해양분야에서는 선박위치 자동인식시스템(AIS) 및 선박운행관리시스템(VTS)에서 2002년부터 적용될 예정이고, 항공분야에서는 향후 몇 년후에는 ADS-B, SMGCS에서 응용될 가능성이 높다. 본 연구에서는 STDMA를 이용한 SMGCS구현을 위한 기술개발로서 사전에 측지된 기준국으로부터 실시간으로 GPS 보정값을 생성, 전송하도록 하는 실시간 DGPS기술과 동기신호에 따라 시분할 다중접속을 구현한 소프트웨어 기반의 TDMA기술을 구현하였으며 이를 연구원내에서 차량이동 실험을 수행하여 다수의 이동국간에 측위값을 상호전송함으로써 각각의 위치를 실기간으로 파악할 수 있음을 보였다.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.45-49
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• 2012

VDL(VHF Data Link) Mode E uses TDMA(Time Division Multiple Access) based aeronautical communication technologies for airborne environments. In the VDL Mode E, aircraft uses RR(Reservation Requests) slot to request data slot. However, RR needs a long guard time, since aircraft communication spans a considerable distance. The more number of aircrafts causes a larger amount of guard times which can make a throughput decreased. In this paper, we propose an enhanced MAC to reduce the guard time by using the distance information of aircraft. The ground station sends management data including time stamp. And then all aircraft can measure their distance from the ground station.

• Information and Communications Magazine
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• v.15 no.7
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• pp.169-179
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• 1998

본 논문에서는 현재 연구 개발되고 있는 Fiber-to-the-curb / Very high-rate digital subscriber line(FTTC/VDSL) 시스템의 DAVIC 표준 가입자 전송 기술인 51.84 Mb/s 16-CAP (Carrierless AM/PM) 전송시스템 (downstream)과 1.62 Mb/s QPSK burst-mode TDMA 전송시스템 (upstream)및, 타이밍 복원회로 등의 동작 원리 및 구조를 간략하게 기술하였다. 본 논문은 FTTC/VDSL 전송시스템 개발을 위하여 전체시스템이 운영될 환경, 즉 채널에 대하여 기술한 후, 주어진 채널에 적합한 down-stream전송시스템 알고리즘 및 구조를 설명하였으며, 타이밍 복원 시스템을 기술하였다. FTTC/VDSL시스템은 네트워크의 한 개의 송수신부가 가입자 댁내의 여러 개의 set-top box와 데이터를 주고받는 점 대 다점 (point-to-multipoint) 구조로 이루어져 있으며, 따라서 역 방향 (upstream) 채널 데이터 전송을 위한 QPSK 전송시스템은 네트워크쪽의 QPSK 수신부가 가입자 댁내의 여러개의 QPSK 송신부를 서비스할 수 있게끔 시분할 다중접속 방식인 burst-mode TDMA전송방식으로 구현되었다. FTTC/VDSL 전송시스템은 DAVIC의 시스템 성능 요구조건을 만족하게 설계되었으며, 모든 기능은 디지털로 구현되었고 칩 구현을 위하여 각 기능의 VLSI 시스템 파라메타 들을 추출하고 성능 시험을 실시하였다.