• Journal of Communications and Networks
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• v.8 no.3
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• pp.306-312
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• 2006

This paper studies theoretically the bit error rate (BER) performance of cooperative transmission using space-time block code (STBC) in a fully distributed manner. Specifically, we first propose a STBC-based cooperative signaling structure to make the cooperation of three single-antenna terminals possible. Then, we derive the closed-form BER expressions for both cooperation and noncooperation schemes under flat Rayleigh fading channel plus additive white Gaussian noise (AWGN). The validity of these expressions is verified by Monte-Carlo simulations. A variety of numerical and simulation results reveal that the cooperative transmission achieves higher diversity gain and better performance than the direct transmission for the same total transmit power.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.11
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• pp.1365-1373
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• 1999

In many countries including Korea, in order to transmit the more electric power, the higher transmission line voltage is inevitable. So, a rapid reclosing scheme is important for EHV/UHV transmission lines to ensure requirements for high reliability of main lines. A critical aspect of reclosing operation is the extinction of the secondary arc since it must extinguish before successful reclosure can occur. Therefore the accurate simulation techniques of arcing faults are of importance. And successful reclosing switching can be accomplished by adopting a proper method such as HSGS and hybrid scheme to reduce the secondary arc extinction time. First of all, this paper discusses a suggested arc model, which have time dependent resistance for primary arc and piecewise linear approximated arc model for secondary arc. And this simulation technique is applied to Korean 765 kV transmission lines. Also hybrid scheme is simulated and evaluated for the purpose of shortening dead time. For adaptive reclosing scheme, variable dead time control algorithm is suggested. Two kinds of algorithm are tested. One is max tracking algorithm and the other is rms tracking algorithm. According to simulation results, rms tracking has less errors than max tracking. Therefore rms tracking is applied to Korean 765 kV transmission lines with hybrid scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.7
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• pp.2365-2382
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• 2014

While single-user spatial multiplexing multiple-input multiple-output (SU-MIMO) allows spatially multiplexed data streams to be transmitted to one node at a time, multi-user spatial multiplexing MIMO (MU-MIMO) enables the simultaneous transmission to multiple nodes. However, if the transmission time required to send packets to each node varies considerably, MU-MIMO may fail to utilize the available MIMO capacity to its full potential. The transmission time typically depends upon two factors: the link quality of the selected channel and the data length (packet size). To utilize the cumulative capacity of multiple channels in MIMO applications, the assignment of channels to each node should be controlled according to the measured channel quality or the transmission queue status of the node.A MAC protocol design that can switch between MU-MIMO and multiple SU-MIMO transmissions by considering the channel quality and queue status information prior to the actual data transmission (i.e., by exchanging control packets between transmitter and receiver pairs) could address such issues in a simple but in attractive way. In this study, we propose a new MAC protocol that is capable of performing such switching and thereby improve the system performance of very high throughput WLANs. The detailed performance analysis demonstrates that greater benefits can be obtained using the proposed scheme, as compared to conventional MU-MIMO transmission schemes.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.157-160
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• 2002

When the teleoperation system has a signal transmission time delay between slave system and control system, the position tracking performance of the slave system and system stability are likely to be deteriorated. This paper proposes a force reflecting position control scheme for teleoperation system with signal transmission time delay. The proposed scheme not only satisfy the system internal stability but also improves the position tracking performance with disturbance rejection capability. The simulation results show that the proposed control method provides excellent performances.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.2
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• pp.64-70
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• 2021

Nowadays, there are significant interests in real-time remote control using wireless networks. In implementing real-time remote control, one important factor is delay performance of real-time control message. Especially, the technique to reduce jitter of delay is necessary in transmitting periodically real-time control message. In this paper, we proposed synchronized transmission to reduce jitter of delay, when real-time control message was transmitted through wireless networks. The proposed transmission kept synchronization between source node and wireless transmitter and controlled transmission instance to transmit real-tie control message with fixed delay in wireless networks. According to results of experiment in military unmanned vehicle system, the proposed transmission reduced jitter of delay as 32% as that of a non-employing case.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.2
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• pp.191-198
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• 2013

Geo-pointing is a function that maintains LOS(Line of Sight) to a stationary ground target by controlling azimuth and elevation angles of a EOS(Electro-Optical System) which are calculated from aircraft navigation data and target coordinates. In design and implementation of the geo-pointing, a transmission time delay between GPS/INS and EOS is a major degradation factor of the geo-pointing performance when the aircraft is rapidly maneuvered especially. In this paper, a kalman filter is designed to compensate the transmission time delay of aircraft navigation data. Simulation and test results show that the geo-pointing performance is enhanced by the proposed compensation technique.

• Korean Journal of Computational Design and Engineering
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• v.7 no.4
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• pp.262-268
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• 2002

Octree representation has the advantage of being able to represent complex shapes approximately through the repetition of simple primitive shapes. Due to this reason, octree representation together with VRML(Virtual Reality Modelling Language) is usually used for approximating 3D shapes. Since the data size of octree representation increases rapidly as 3D shape to be represented is more and more complicated, its transmission time also increase. In this paper, provided is the new octree representation and encoding/decoding scheme for real-time transmission through the internet in order to visualize 3D geometric data of large size approximately.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.174-175
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• 2019

In this study, the spalling and ultrasonic pulse transmission time of concrete were investigated according to compressive strength during heating. As a result, the higher the compressive strength of the concrete, the more the explosion occurs, which affects the cross-sectional loss and the spalling fragment size. Also, ultrasonic pulse transmission time was found to be strongly influenced by the section loss of concrete.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.39-40
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• 2007

In this Paper a transmission algorithm based on Zigbee Networks is proposed. The superframe of IEEE 802. 15.4 is applied to the transmission method of real-time mixed data (periodic data, sporadic data, and non real-time message). The simulation results show the real-time performance of sporadic data is improved by using the proposed transmission algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.943-950
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• 2005

Recently, many of researches on stream transmission for satisfying each of different real-time transmission condition of the multimedia data that demands various service quality through high-speed networks have been studied actively. In this paper, we design a scheme that discriminately reserves the network resources for the transmission of each multimedia application and propose a bandwidth allocation scheme for improving the utilization ratio of free resources. And we also propose a pipelining scheme for providing flexible real-time transmission. The proposed schemes can be used to support a real-time transmission by applying feedback transmission control method based on receiving buffer for guaranteeing the synchronization conditions requested by the multimedia data. Moreover, we propose a transmission control scheme that can take the amount of network resources down to the minimum amount within the range of permissible error-range under the guarantee with no quality degradation simultaneously when the bottleneck is caused by the network congestion. Finally, we propose a dynamic bandwidth smoothing scheme that can smooth the maximum bandwidth to the demand of each video steam for giving continuous transmission to the delay sensitive video steam between senders and receivers.