• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1042-1049
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• 2014

In Military MicroWave communication, the distance of link, availability, transmission capacity is the important point in order to design the circuit. Currently, operated by fixed modulation, in the future it will be evolved to the modulation techniques enabled to increase the transmission capacity. It would be hard to consistently guarantee the transmission quality of the high-availability because the occurrence probability of fading increase in terms of the link distance for the case of the long distance. In the case of the modulation techniques for the transmission of high-capacity, as the distance is long, a falling-off in the fade margin from the link budget analysis cause the decrease in the availability. It is difficult to provide QoS guaranteed connection. In this paper, we propose the performance improvement technique of transmission by the variable allocation of the bandwidth and the higher priority transmission technique using setting the ratio of the higher priority capacity in association with the distance of link. Also we suggest the alternative of the calculation for channel transmission capacity to design the circuit.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.364-369
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• 2007

A system heat pump provides the benefits of comfort, energy conservation and easy maintenance. Recently, the system heat pump has been employed in small and medium-sized buildings. However, the performance data and control algorithm for system heat pump are limited in literature due to complicated system parameters and operating conditions. In the present study, the performance of a system heat pump with two indoor unit is measured by varying indoor loads, EEV opening, and compressor speed. In addition, the integral optimum regulator which includes MIMO control algorithm is proposed. The capacity modulation and optimum capacity for each indoor unit can be adjusted by utilizing the EEVs opening and compressor speed. The proposed scheme shows appropriate control performance at test conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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• pp.98-107
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• 2002

The performance of a capacity controlled system, which are tandem, pole change, bypass and inverter driven compressor, has been compared with that of a con- ventional constant speed system. It has been found that capacity modulated system can offer more than 14 percent improvement in SEER over the conventional system. Comparative test results show that two compressor system can attain an improvement in SEER up to 42% over the conventional on/off system, and is feasible without additional investment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2521-2526
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• 2013

In this paper, a novel spatial modulation (SM) with transmit antenna selection (TAS) based on maximizing channel capacity is proposed. Comparing to the conventional TAS technique, the proposed TAS considers the channel capacity of the MIMO channel with antenna selection. The optimal antenna set selection is applied to SM by taking account of the all possible sets, and then, a sub-optimal antenna set selection is also proposed for reducing the computational complexity of the optimal method. Computer simulations show that the proposed TAS significantly outperforms the existing SM scheme based on the magnitude of the channel vectors in terms of bit error rate (BER) in various environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11C
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• pp.682-693
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• 2011

Energy spreading transform (EST) based modulation is an effective technique to combat frequency-selective fading in broadband wireless communication. It performs close to the inter-symbol interference (ISI)-free matched filter bound (MFB) only at the complexity of a linear detector. Originally, EST-based modulation has been proposed for QPSK. However, to fully utilize the capacity of multipath fading channels, higher-order modulations are also necessary. In this paper, we review the EST based modulation that has originally been proposed for QPSK and discuss its extension to 8 PSK and 16 QAM. The performance of the extended system is verified through simulation in Proakis B and 8-tap fading channel. The EST based modulation for 8 PSK shows the performance which is very close to MFB and the EST based modulation for 16 QAM shows the performance gap between its receiver and MFB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.2
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• pp.86-91
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• 2014

Holographic data storage (HDS) has a number of advantages, including a high transmission rate through the use of a charge coupled device array for reading two-dimensional (2D) pixel image data, and a high density capacity. HDS also has disadvantages, including 2d intersymbol interference by neighboring pixels and interpage interference by multiple pages stored in the same holographic volume. These problems can be eliminated by modulation codes. We propose a 7/9 error-correcting modulation code that exploits a Viterbi-trellis algorithm and has a code rate larger (about 0.778) than that of the conventional 6/8 balanced modulation code. We show improved performance of the bit error rate with the proposed scheme compared to that of the simple 7/9 code without the trellis scheme and the 6/8 balanced modulation code.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.381-384
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• 2002

Orthogonal Frequency Division Multiplexing (OFDM), which employs orthogonal overlapping subcarriers to modulate the signals, has been attracted much attention in recent time as a favorable option for future generation wireless networks due to its ability to overcome many impairments in wireless channels. Since OFDM is a multi-carrier system adaptive modulation techniques can be effectively and efficiently used to enhance the system performance in terms of both BER and overall system capacity. This paper discusses a COFDM-CDMA system with adaptive modulation schemes for future generation wireless networks.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.287-290
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• 1998

This paper presents PWM method which modulates two third period only during one cycle of power converter. This method is compared with the conventionl sinusoidal modulation method applying to the power converter with large capacity necessitating low switching frequency. The presented modulation method enables to reduce power semiconductor rating, minimize switching loss, and improve the current wave form.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.55-62
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• 2008

Adaptive modulation and Coding(AMC) scheme is promising technique to support the demands for high data rates and wideband proposed for 4G mobile communication system standards. In this paper, adaptive modulation and coding(AMC) based on OFDM system is analyzed through simulation for single user case and compared with SISO-OFDM and SFBC(Space frequency block coding)-OFDM. The performance analysis in terms of capacity for downlink system environments with different values of constellation size under multipath fading channel is done. The adaptive modulation and coding technique is based on perfect estimation channel. It has been observed that SFBC(Space-frequency block coding)-OFDM system gives better performance in terms of capacity.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.2 no.2
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• pp.59-63
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• 1988

In a fixed AC power source the PWM techniques were used to vary the voltage and the fundamental frequency. The conventional PWM techniques due to the problem of commutation number and filter size have been studied the PWM output waveforms which applied the motor drive. However in this paper, the carrier frequency with sinusoidal PWM waveform is modulated from 10(KHz) to 45(KHz) using termination devices with high - speed switching capacity and applying LPF(Low Pass Filter) with small capacity to output of inverter and the PAM(Pulse Amplitude Modulation)is obtained. Considering the property of the speed and the control, the sinusoidal PWM control circuit was composed of the microprocessor and analog circuit. In experment result, the system properties are study on the sinusoidal voltage waveform with modulation index changing from 0.6 to 1.0.