• The Transactions of the Korea Information Processing Society
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• v.2 no.3
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• pp.374-381
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• 1995

For designing radio communication systems, radio-channel effects must be considered in order to obtain the desired communication quality, transmitting power, transmission speed and bit error rate. In radio channel, one of major factors that degrade communication quality is multipath fading between transmitting and receiving points. Therefore, a channel model which can describe fading effects correctly is requested. This paper deals with the composition of the channel simulator model that describes multipath fading effects and delay times which occur in the channel. For the performance analysis of the proposed model, trandmitting signal is used in the simulation. From simulation results, it can be shown that probability density function. level crossing rates and average fading-duration time distribution of the faded receive signal are very similar with theoretic values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.447-455
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• 2014

In this paper, we consider a representative integral imaging method in glasses-free 3D image processing and propose a prioritized transmission scheme for guaranteeing a received video quality in error-prone environments. According to the correlation of pixels consisting of each voxel of integral image, we set the priority differently and apply the modulation level according to this priority value. That is to say, the corresponding pixels with small variance are set to a high priority and transmitted by using a low level modulation that is robust under transmission errors, but the corresponding pixels with greater variance are set to a lower priority and transmitted by using a high level modulation that has a high bit error rate but fast transmission rate. Result shows that the proposed scheme that applies the error-robust modulation level to the important image bit stream with the high priority improves the peak to sidelobe ratio (PSR) of the received 3D image, compared with a typical method that use the same modulation level without distinction of priorities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.315-321
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• 2010

In Ad-hoc networks, centralized power control is not suitable due to the absence of base stations, which perform the power control operation in the network to optimize the system performance. Therefore, each node should perform power control algorithm distributedly instead of the centralized one. The conventional distributed power control algorithm does not consider the adaptive bit loading operation to change the MCS (modulation and coding scheme) according to the received SINR (signal to interference and noise ratio), which limits the system throughput. In this paper, we propose a novel distributed bit loading and power control algorithm, which considers the adaptive bit loading operation to increase total system throughput and decrease outage probability. Simulation results show that the proposed algorithm performs much better than the conventional algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.61-68
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• 2010

In this paper, we investigate the performance of ARQ-aided Time Switched Transmit Diversity (ARQ-TSTD) applying the multi-level control signaling in the WCDMA LCR-TDD system. Proposed ARQ-TSTD system applies the multi-level control signaling scheme in which the receiver sends the response signal (ACK or NACK signal) to the transmitter and defines NACK2 signal for multi-level control. Transmitter utilize the NACK2 control signal to the postponement of transmission and multi-user scheduling scheme proposed by this paper. Simulation results demonstrate that the proposed postponement of transmission and multi-user scheduling scheme yield about 1.3dB, 1.4dB performance gain respectively, compared with the conventional ARQ-TSTD with antenna switching scheme in tenn of the frame error rate (FER) for mobile speed of 3km/h and FER value of 10%. In addition, 14% and 11.5% of throughput gain respectively is shown when Eb/N0=-3dB.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.611-614
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• 2006

Resolution 122 requires to study power limitation applicable for HAPS ground stations to facilitate sharing with space station receivers in 47/48GHz bands. ITU-R Recommendation 1481-1 recommends to improve the side lobe characteristics of HAPS ground station antenna for sharing between FSS system and HAPS system. Thus, in this paper, we propose maximum allowable off-axis e.i.r.p. level of HAPS ground station antennas by considering power limitation to HAPS ground station in Resolution 122 in order to reduce unfeasible separate distance between HAPS and GSO FSS service coverage and improve the side lobe characteristics of HAPS ground station antennas in Recommendation SF.1481-1.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.490-492
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• 2010

A swing level controlled voltage-mode transmitter is proposed to support a stub series-terminated logic channel with center-tapped termination. This transmitter provides a swing level control to support the diagnostic mode and improve the signal integrity in the absence of the destination termination. By using the variable parallel termination, the proposed transmitter maintains the constant output impedance of the source termination while the swing level is controlled. Also, the series termination using an external resistor is used to reduce the impedance mismatch effect due to the parasitic components of the capacitor and inductor. To verify the proposed transmitter, the voltage-mode driver, which provides eight swing levels with the constant output impedance of about $50{\Omega}$, was implemented using a 70nm 1-poly 3-metal DRAM process with a 1.5V supply. The jitter reduction of 54% was measured with the swing level controlled voltage-mode driver in the absence of the destination termination at 1.6-Gb/s.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.6
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• pp.53-67
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• 2002

The multimedia synchronization is one of the key issues to be resolved in order to provide a good quality of multimedia related services, such as Video on Demands(VoD), Lecture on Demands(LoD), and tele-conferences. In this paper, we introduce an adaptive multimedia synchronization algorithm using the level of buffers and load of servers, which are modeled and analyzed by ExSpect, a Petri net based simulation tool. In the proposed algorithm, the audio and video buffers are divided to 5 different levels, and the pre-defined play-out speed controller tries to make the buffer level to be normal in different temporal relations between multimedia streams using buffer levels and server loads. Because each multimedia packet is played by the pre-defined play-out speed, the media data can be reproduced within the permissible limit of errors while preserving the level of buffers to be normal. The proposed algorithm is able to handle and support various communication restrictions between providers and users, and offers little jitter play-out to many users in networks with the limited transmission capability. The performance of the developed algorithm is analyzed in various network conditions using a Petri net simulation tool.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.3 s.333
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• pp.25-34
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• 2005

In this paper, we analyzed and measured the electrical crosstalk characteristics of a triplex transceiver module for ethernet Passive optical networks(EPONS). And we improved the electrical crosstalk levels using Dummy ground lines with signal lines. The triplex transceiver module consists of a laser diode as a transmitter, a digital photodetector as a digital data receiver, and a analog photodetector as a community antenna television signal receiver. And there are integrated on silicon substrate. The digital receiver and analog receiver sensitivity have to meet -24 dBm at $BER=10^{-l2}$ and -7.7 dBm at 44 dB SNR. And the electrical crosstalk levels have to maintain less than -86 dB from DC to 3 GHz. From analysis and measurement results, the proposed silicon substrate structure that contains the Dummy ground line with $100\;{\mu}m$ space from signal lines and separates 4 mm among devices respectively, is satisfied the electrical crosstalk level compared to simple structure. This proposed structure can be easily implemented with design convenience and greatly reduced the silicon substrate size about $50\%$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.132-137
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• 2003

This performance is motivated to develop a tracking antenna system for receive the satellite broadcasting signal in the coast sailing ship. Therefore, this system is made to small size, light weight and simple operation which is must to low cost system for popularization of small size ship and adaptive possibilities with useful on a ship in the coast using 1 axis Az-mount. The antenna mount structure is a compact size and easy operation to the Az-axis type which is operated by step motor. The antenna unit is a domestic made plate type of patch array and ship's moving detection is using the gyro sensor for ship's moving control. We are designed to algorithm, which walking is abreast for step track and ship's moving compensation. Ship's moving compensation is adapted to the closed loop control method by detection from gyro sensor. This system is consisted of micro processor, ADC, comparative amplifier, step motor driver, mount mechanism and algorithm. We have analysised the tracking performance of prototype on sailing ship board.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.9-18
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• 1998

A single RF transceiver chip for an extended GSM handset application was designedm, fabricated and evaluated. A RFIC was fabricated by using silicon BiCMOS process, and then packaged in 80 pin TQFP of $10 {\times} 10 mm^{2}$ in size. As a result, it was achieved guite reasonable integraty and good RF performance at the operation voltage of 3.3V. This paper describes development results of RF receiver section of the RFIC, which includes LNA, down conversion mixer, AGC, switched capacitor filter and down sampling mixer. The test results show that RF receiver section is well operated within frequency range of 925 ~960 MHz, which is defined on the extended GSM specification (E-GSM). The receiver section also reveals moderate power consumption of 67 mA and minimum detectable signal of -105 dBm.