• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1198-1205
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• 2000

In this paper, we introduce a modified interference cancellation scheme to overcome MAI in DS-CDMA. Among ICs(Interference Cancellers), PIC(Parallel IC) requires the more complexity, and SIC(Successive IC) faces the problems of the long delay time. Most of all, the adaptive detector achieves the good BER performance using the adaptive Inter conducted iteration algorithm. So it requires many iterations. To resolve the problems of them, we propose an improved adaptive detector that the received signal removed MAI through the sorting scheme and the cancellation method are fed into the adaptive filter. Because the improved input signal is fed into the adaptive filter, it has the same BER performance only using smaller iterations than the conventional adaptive detector, and the proposed detector having adaptive filter requires less complexity than the other detectors.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.21-28
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• 2016

This paper presents a cooperative transmission scheme for underwater acoustic sensor networks to improve packet transmission rate and reduce energy consumption. Source node transmits duplicated information relayed by distributed antennas called a virtual antenna array. Destination node combines that information to reduce packet error rate. The suggested cooperative scheme enhances the reliability by providing high diversity gains through intermediate relay nodes to overcome the distinct characteristics of the underwater channel, such as high transmission loss, propagation delay, and ambient noises. It is suggested that the algorithm select destinations and potential relays from a set of neighboring nodes that utilize distance cost, the residual energy of each node and local measurement of the channel conditions into calculation. Simulation results show that the proposed scheme reduces average energy consumption, response time, and increases packet delivery ratio compared with the SPF(Shortest Path First) and non-cooperative scheme using OPNET Moduler.

• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.295-300
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• 2002

We developed an optical transmitter and receiver for an electrical time division multiplexed (ETDM) 20 Gb/s optical transmission system, and experimentally investigated their characteristics. Especially, the clock extraction circuit, which is a key component in realizing broadband optical transmission receivers, was realized by using an NRZ-to-PRZ converter implemented with a half-period delay line and an EX-OR, a high-Q bandpass filter using a cylindrical dielectric resonator, and a microstrip coupled-line bandpass filter. Finally, the bit-error-rate of demultiplexed 10 Gb/s electrical signal after back to-back transmission was measured, and a high receiver sensitivity [-26.2 dBm for NRZ ($2^{7}-1$) pseudorandom binary sequence (PRBS)] was obtained

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.5
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• pp.709-714
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• 2018

Visual Reality technology is becoming more and more interesting as it attracts people's interest. VR technology is used in various markets such as games, animation, and education. However, there were many people experiencing motion sickness such as dizziness and headache due to the delay time between hardware such as a device for sending a video after experiencing a VR image and an HMD for reproducing an image. The system proposed in this paper focuses on the environment rather than the movement of the attraction and detects the dividing line existing on the path by the proximity sensor and accurately calculates the position on the path according to the user 's motion. Since the position of the user is synchronized with the VR image, the position error of the user is improved to 0.2%.

• Journal of Advanced Navigation Technology
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• v.13 no.5
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• pp.742-748
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• 2009

Zigbee wireless communication technology has features which are low cost, low power and coping ability against a high delay time when the automatic wireless system is manufactured. Therefore, in this paper, we research a method improving the data transmission reliability of the industrial equipment control and management system using zigbee wireless communication technology. we used a convolutional code with code rate R=1/2, constraint K=5 and generation polynomial constant g1=(10111) and g2=(10011) as a reliability method. From the transmission simulation at LOS environment, we are able to predict the transmission error performance according to the distance difference. Furthermore, At the PER performance analysis, we can get the result that this system reliability with convolutional code is improved about 5 times than the existing system. From these results, we can prove that the convolutional code is the solution to improve the system reliability of the industrial equipment control and management system using zigbee wireless communication technology.

• Journal of Advanced Navigation Technology
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• v.19 no.5
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• pp.389-394
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• 2015

This paper considers the transfer alignment in the inertial navigation system which has lever-arm and the time delay in the velocity measurement. We suggest a method to improve the performance of the velocity matching. First, we analyze the estimation performance of the velocity matching through the tuning of the two covariance matrices of process noise and measurement noise. Next we provide some maneuvering conditions of the vehicles to improve the estimation performance using the observability analysis. The analysis results are verified using the computer simulations, which show that cruise movements do not provide the azimuth estimation of the vehicles, while east or north accelerating movement can provide.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8C
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• pp.810-823
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• 2005

The transmission of duplicate packets provides a great loss-resilience without undue time-delay in the video transmission over packet loss networks. But this method generally deteriorates the problem of traffic congestion because of the increased bit-rate required for duplicate transmission. In this paper, we propose an efficient packetization and duplicate transmission of video packets. The proposed method transmits only the video signal with high priority for each video macroblock that is quite small in volume but very important for the reconstruction of the video. The proposed method significantly reduces the required bit-rate for duplicate transmission. An efficient packetization method is also proposed to reduce additional packet overhead which is required for transmitting the duplicate data. The duplicated high priority data of the Previous video slice is transmitted as a Piggyback to the data Packet of the current video slice. It is shown by simulations that the proposed method remarkably improves the packet loss-resilience for video transmission only with small increase of redundant duplicated data for each slice.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1387-1398
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• 2009

In the latest we will make a demand for the precision position estimation for the Mobile-station(MS)'s position. But, we have a lot of problems the position estimation method using the existing method. The Base-station(BS) measure a distance according to time delay waves to receive propagate from the MS and estimate the position using the existing circle equation with method to be selected BSs in close proximity the MS. It knows that happens a lot of error the estimated position and the true position. This paper propose that the method is selected round BSs to estimate for MS's position and estimated the angle using the second law of cosine. This paper demonstrate that using simulation the proposal method is a predominant method to compare with the existing method.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.584-591
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• 2000

Power Quality Compensator(PQC) has been installed to protect the sensitive loads against the voltage disturbances, such as voltage sag and interruption. In general, static switch is used for the purpose of link between utility and PQC. So transfer operation of the static switch play a important part in the PQC. Many studies on the structure and control of PQC have been progressed in active, but these researches have been rarely mentioned about any voltage-disturbances-detection method to start the PQC operation. In this paper, a new voltage-disturbances-detection algorithm for computer application loads using the CBEMA/ITIC curve is proposed for transfer operation of the static switch. The proposed detection algorithm is implemented to get fast detecting time through the comparison of instantaneous 3-phase voltage values transferred to DC values in the synchronous reference frame with the operating reference values. To get the robust characteristics against the noise, a first order digital filter is designed. The magnitude falling and phase delay caused by the filter are compensated through the error normalizing and numerical analysis using transfer function, respectively. Finally, the validity of the proposed algorithm is proved by ACSL simulation and experimental results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1950-1958
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• 2016

Today, technique for precisely positioning vehicles is very important in C-ITS(Cooperative Intelligent Transport System), Self-Driving Car and other information technology relating to transportation. Though the most popular technology for vehicle positioning is the GPS, its accuracy is not reliable because of large delay caused by multipath effect, which is very bad for realtime traffic application. Therefore, in this paper, we proposed the Vision-Based High Accuracy Vehicle Positioning Technology. At the first step of proposed algorithm, the ROI is set up for road area and the vehicles detection. Then, center and four corners points of found vehicles on the road are determined. Lastly, these points are converted into aerial view map using homography matrix. By analyzing performance of algorithm, we find out that this technique has high accuracy with average error of result is less than about 20cm and the maximum value is not exceed 44.72cm. In addition, it is confirmed that the process of this algorithm is fast enough for real-time positioning at the $22-25_{FPS}$.