• 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 Korean Electrochemical Society
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• v.3 no.4
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• pp.241-245
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• 2000

The objective of this work Is to design, fabricate, and characterize pseudo-capacitor using amorphous $MnO_2\;nH_2O$ electrode material. The cyclic voltammogram under 100mV/s scan rate of the material shows the electrochemically stable potential window of 1V and the specific capacitance of 250F/g. The TDMA pulse test result indicates that the TDMA system (2 parallel-pseudo-capacitor systems) has the ohmic voltage drop of 0.22V and the capacitor voltage drop of 0.38V. The total voltage drop of the TDMA system is 0.60V and less than 1V of which value is the maximum voltage drop requirement or the TDMA satellite phone. Also, the TDMA system had the ESR of $55m{\Omega}$ and the capacitance of 105mF. Therefore, it is confirmed that the TDMA system has the application feasibility as load-leveling capacitor for the satellite phone.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.639-644
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• 2001

Sequence Code Division Multiple Access) and TDMA(Time Division Multiple Access) system. In this system, the narrowband TDMA signals can cause intolerant interferences to CDMA signals. In this paper, DS-CDMA/TDMA frequency sharing system have been analyzed in AWGN(Additive white Gaussian Noise), MAI (Multi Access Interference) and NI(Narrowband Interference) environment. Also, performance improvement has been obtained by adopting an adaptive notch filtering scheme using complex filter bank and CCI canceller.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.1
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• pp.1-7
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• 2000

In this paper, we proposed a complex multirate filter bank(CMRFB) based adaptive notch filtering technique to solve the co-existence narrowband interference problem of DS-CDMA and TDMA systems. We have discussed error performance of co-existence of DS-CDMA and TDMA system by using complex multirate filter bank in land mobile channel and computer simulation results show that the proposed scheme can eliminate the narrowband interference(TDMA signals) effectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.4
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• pp.470-476
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• 2008

In this paper, we describe the cause of TDMA noise and distinction method of TDMA noise source in a GSM mobile phone. The causes of TDMA noise are composed of RF(Radio Frequency) energy coupling and low frequency energy coupling by burst ripple. We propose the distinction method of TDMA noise source from output(TDMA noise measurement) and frequency response of a system(audio path). Especially we propose a method of insertion loss($S_{21}$) analysis and the improvement method for RF energy coupling. Capacitor(40 pF) is a solution to reduce RF energy coupling and therefore TDMA noise was reduced by 10 dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9A
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• pp.1273-1281
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• 2000

In this paper we studied for multi-user detection system, which hold the merit of CDMA system and can enhance the system capacity. We designed actually realizable quasi-optimal multiuser detection system by use of linear equalizer on the concept that multiuser detection algorithm can be reduced by combining TDMA with CDMA. we call this the hybrid TDMA/CDMA system. And we proposed multiuser detection system, which can use PSAD and MSDD channel estimation method. As a result of performance analysis we acquired equal or much better performance by use of linear multichannel equalizer in the case of not so many user. And on the occasion of many user within cell we can also acquired much better performance in comparison with conventional single user detection system by use of hybrid TDMA/CDMA system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.298-304
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• 2013

Channel attenuation must be taken into account when designing Time Division Multiple Access(TDMA) communication systems. In addition, Automatic Gain Control (ACG) is a requirement in satellite communication systems in order to form a stable network regardless of rapidly changes in channel environment. In this study, we present an AGC with possible real-time application to time slots in satellite TDMA communication systems. A satellite TDMA system was designed and implemented in order to test the performance of the proposed real-time AGC, and the system's BER (Bit Error Rate) was found by applying the proposed AGC algorithm. These results can be expected to be of high value in improving the stability of satellite TDMA communication systems in the future.

• Journal of the Korean Professional Engineers Association
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• v.30 no.1
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• pp.125-136
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• 1997

The satellite communications system application to the Broadband ISDN(BISDN) is now being studied. Asynchronous transfer mode(ATM) is the target for BISDN and makes it possible to offer multimedia services on the simple network structure. This paper clarifies the required functions to the ATM interface between the terrestrial network and satellite TDMA system to compensate cell delay variation caused by satellite link, to improve the transmission efficiency, to do usage parameter control and to configure TDMA/ATM hardware interface.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.527-536
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• 2004

A novel hybrid multiple access system, TD-BCDMA, where Binary CDMA that maintains a constant amplitude by clipping the summation of input signals multiplied by the orthogonal codes is transmitted over a TDMA frame structure, was Nosed. In every time slot of TDMA, binary CDMA modulated multiple channel signals are transmitted with the same waveform of TDMA. TD-BCDMA has all the advantages of TDMA. Flexible adjustment of the data transmission rate In demand is possible by adjusting the number of codes and time slots assigned to each user. This property was used to show an example of Ad Hoc network applications. To obtain a proper synchronization scheme for TD-BCDMA, the Receiver Operating Characteristics performance and the false alarm probability and false dismissal probability under various channel environment of two different schemes, a preamble scheme as in TDMA and a synchronization channel scheme as in CDMA were compared. It was proved that the preamble scheme is more practical and suitable than the synchronization channel scheme for the hybrid multiple access system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1631-1641
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• 2012

A TDMA system in satellite communication has been utilized. Especially DVB-S2 was standardized and now operated in satellite broadcasting system. In this paper, we propose a TDMA frame structure appropriate for special purpose which has the good reliablilty in a poor RF environment even if frequency efficiency is decreased. TDMA frame duration is 12 seconds which is long duration in comparison with general TDMA system with several ms. Designing the frame structure, time and frequency shift in single frame duration are considered. Simulation results show that the proposed frame structure and synchronization method has robust synchronization performance when the terminal is even in low SNR as well as 25 kHz frequency offsets.