• Journal of electromagnetic engineering and science
• /
• v.5 no.1
• /
• pp.1-7
• /
• 2005

The implementation of a simple analog in-phase combiner is presented for a high capacity radio relay system with space diversity. It provides good performance in terms of simple hardware and easy control, and measured results are in good agreement with simulated ones. To suggest practical applications, signatures with/without diversity are measured for STM-1 signal of 64-QAM radio relay system combined with a 13-tap equalizer, and they provided more than 25 dB fade depth at 10$^{-3}$ BER under the frequency selective fading condition.

• Journal of electromagnetic engineering and science
• /
• v.11 no.1
• /
• pp.5-10
• /
• 2011

We propose an adaptive cooperative scheme with a multi-relay node that achieves high bandwidth efficiency and achieves better SEP performance. In the proposed protocol, if the quality of the direct channel is better than that of the all channels from relays to destination, the source will transmit directly to the destination. Otherwise, the source broadcasts the signal and then a potential relay will be chosen to help the source. A re-transmission will also occur if the potential relay cannot be detected. The spectral efficiency is first derived by calculating the probability of each mode, i.e., direct and cooperation transmission. Subsequently, the SEP performance of M-PSK modulation for the scheme is analyzed by considering each event where the source transmits data to the destination. Finally, the obtained analytical results are verified through computer simulations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.4
• /
• pp.392-398
• /
• 2010

In this paper, we proposed adaptive two-way relay cooperative communication considering the quality of the user-relay links, and derived outage probability. Network-coding based two-way relay communication can achieve more throughput since it can reduce transmission time compared conventional two-way relay communication. However, Network-coding based two-way relay communication assume that the relay can decode received signal correctly. If relay cannot decode the signal, it leads to error propagation at the relay. In this paper, we proposed adaptive two-way relay cooperative communication scheme. In proposed scheme, the user "A" transmits the signal to relay and another user "B". The relay operates adaptively depend on quality of user-relay links. Simulation result show that proposed scheme has better performance when the quality of the user-relay links are poor. Also it can get diversity order 2.

• Journal of electromagnetic engineering and science
• /
• v.11 no.2
• /
• pp.133-142
• /
• 2011

Coded cooperation that integrates channel coding in cooperative transmission has gained a great deal of interest in wireless relay networks. The performance analysis of coded cooperation protocol with multiple relays is investigated in this paper. We show that the diversity order achieved by the coded cooperation in a multi-relay wireless network is not only dependent on the number of cooperating relays but is also dependent on the code-rate of the system. We derive the code-rate bound, which is required to achieve the full diversity gain of the order of cooperating nodes. The code-rate required to achieve full diversity is a linearly decreasing function of the number of available relays in the network. We show that the instantaneous channel state information (CSI)-based relay selection can effectively alleviate this code-rate bound. Analysis shows that the coded cooperation with instantaneous CSI-based relay selection can achieve the full diversity, for an arbitrary number of relays, with a fixed code-rate. Finally, we develop tight upper bounds for the bit error rate (BER) and frame error rate (FER) of the relay selection based on coded cooperation under a Rayleigh fading environment. The analytical upper bounds are verified with simulation results.

• Journal of electromagnetic engineering and science
• /
• v.12 no.1
• /
• pp.8-12
• /
• 2012

In this paper, we evaluate performances of dual-hop decode-and-forward relaying systems with the $N^{th}$ best-relay selection scheme. In some schemes, such as scheduling or load balancing schemes, the best relay is unavailable and hence the system must resort the second best, third best, or generally the $N^{th}$ best relay. We derive the expressions of the outage probability and symbol error rate (SER) for this scenario over Rayleigh fading channels. Monte-Carlo simulations are presented to verify the analytical results.

• Journal of electromagnetic engineering and science
• /
• v.11 no.4
• /
• pp.239-249
• /
• 2011

In this paper, we propose a reliable $8{\times}8$ up-down switching polar relay code based on 3GPP LTE standard, motivated by 3GPP LTE down link, which is 30 bps/Hz for $8{\times}8$ MIMO antennas, and by Arikan's channel polarization for the frequency selective fading (FSF) channels with the generator matrix $Q_8$. In this scheme, a polar encoder and OFDM modulator are implemented sequentially at both the source node and relay nodes, the time reversion and complex conjugation operations are separately implemented at each relay node, and the successive interference cancellation (SIC) decoder, together with the cyclic prefix (CP) removal, is performed at the destination node. Use of the scheme shows that decoding at the relay without any delay is not required, which results in a lower complexity. The numerical result shows that the system coded by polar codes has better performance than currently used designs.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2001.11a
• /
• pp.25-28
• /
• 2001

In this paper. to eliminate a cross-polarization interference caused by co-channel dual polarization technique of digital radio relay system(DRRS), a cross-polarization interference canceller(XPIC) is analysed in terms of the analytical modeling, digital design, and its performance. By virtue of a 13-tap adaptive equalizer and XPIC, about 23dB in XPIC improvement can be obtained by computer simulation. To show the operation of designed XPIC, some simulated results are reviewed under 64-QAM DRRS with co -channel dual Polarization.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.10 no.3
• /
• pp.219-226
• /
• 2022

In this experimental study, the effect of continuously changing the position of electromagnetic force using several coils and a relay switch on fracture energy was investigated. Normal mortar and steel slag mortar specimens in which 50 % and 100 % of sand was replaced with steel slag were cast and exposed to electromagnetic field. The electric field was induced by one coil without a relay switch as an existing method and by partitioning the coil and continuously changing the position using a relay switch. The fracture energy was calculated from the load-vertical displacement curve obtained from the experiment and compared with each other. As a result of the experiment, it was confirmed that the method of partitioning the coil and changing the position of electromagnetic force by using a relay switch is effective in increasing the fracture energy even if the same amount of power is used.

• Journal of electromagnetic engineering and science
• /
• v.13 no.3
• /
• pp.173-177
• /
• 2013

This paper presents a new method for analyzing the maximum efficiency of a wireless power transfer (WPT) system with multiple n resonators. The method is based on ABCD matrices and allows transformation of the WPT system with multiple n resonators into a single two-port network system. The general maximum efficiency equation of a WPT system with multiple n resonators is derived using the ABCD matrix. Use of this equation allows placement of the relay resonators for maximum efficiency even though they are asymmetrical. The general maximum efficiency equation and the method of the optimum placement are verified by a full wave simulation. The results show that the method is useful for the analysis of a WPT system with relay resonators.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.8
• /
• pp.1444-1454
• /
• 2000

The implementation of IF group delay equalizer and its performance are presented for radio relay system applications, and measured results are in good agreement with the simulated ones based upon analytical formulations. For waveguide filter of 40㎒ channel spacing, equalized delay accuracy of about +/- 2.0nsec can be obtained only by constructing 4 stage delay circuits, which provides good performance in system BER curves compared with no filter case, and the difference is less than 1.0㏈ at $10^{-12}$ BER. So this scheme with simple hardware design can be used for correcting the distorted group delays mainly caused by wavegiude filters. To evaluate the designed group delay equalizer, various simulated and experimental results are shown here in conjunction with STM-1 signal of co-channel 64-QAM digital radio relay system.