• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4432-4450
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• 2014

It is widely observed that in practical wireless cooperative communication systems, different links may experience different fading characteristics. In this paper, we investigate into the outage probability and channel capacity of two-way amplify-and-forward (TWAF) relaying systems operating over a mixed asymmetric Rician and Rayleigh fading scenario, with different amplification policies (AP) adopted at the relay, respectively. As TWAF relay network carries concurrent traffics towards two opposite directions, both end-to-end and overall performance metrics were considered. In detail, both uniform exact expressions and simplified asymptotic expressions for the end-to-end outage probability (OP) were presented, based on which the system overall OP was studied under the condition of the two source nodes having non-identical traffic requirements. Furthermore, exact expressions for tight lower bounds as well as high SNR approximations of channel capacity of the considered scenario were presented. For both OP and channel capacity, with different APs, effective power allocation (PA) schemes under different constraints were given to optimize the system performance. Extensive simulations were carried out to verify the analytical results and to demonstrate the impact of channel asymmetry on the system performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.32-39
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• 2006

5.8GHz DSRC(Dedicated Short Range Communications) is a short to medium range communications service that supports both public safety and private operations in roadside to vehicle and vehicle communication. However the 5.8GHz frequency may cause the shadowing effect or communication blocking problem when there is an obstacle or another vehicle between RSE (Road Side Equipment) and OBE (On Board Equipment). In this paper, to solve this problem of the 5.8GHz DSRC, we propose a relay protocol based on the standard of DSRC radio communication between RSE and OBE in the 5.8GHz band made by TTA (Telecommunication Technology Association). By using the proposed relay protocol to DSRC system and intervehicle communication, we also consider a fixed relay protocol and mobile relay protocol. We expect to apply this relay protocol for the DSRC intervehicle communication and video communication between drivers and safe distance among vehicles in the near future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.61-66
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• 2011

Cooperative Communication using relays which include network separated into fixed cooperative relaying and incremental cooperative relaying defending on method receiving signal from a source. If some nodes included network is Primary user ad source and destination, another is Secondary user as relay, The nodes included network excepting source can help PU transmit signal. In the case of all of SU playing a role as relay, destination can get diversity gain, but useless time slot is consumed for transmitting signal. So in this paper, we analysis cooperative relaying which a node succeeding to sense primary signal send signal to destination. We use matlab simulation tool and consider AF, DF, fixed relaying, incremental relaying

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.6
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• pp.292-298
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• 2006

Because of the high cost for the active power filter, passive filters have been widly used to eliminate harmonic currents of nonlinear load and can also improve the power factor. They are not often optimal filters because the passive filters are designed under the fixed load conditions. In this paper we proposed the method which only the necessary harmonic filters are operated by detecting the various harmonic current components. We presents the new control method of passive filter selection type with the relay control circuit which is consist of analog GIC, comparater, flip-flop and etc. By the experimental results using the proposed system for the rectifier load, we concluded that the researched method is cost effective and the performance is better than the passive filter.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.25-33
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• 2017

NOMA (Non-orthogonal multiple access) system becoming a strong candidate for 5G cellular system of its high spectral efficiency. This paper considers an optimal power allocation scheme to minimize the outage probability of a user relay based cooperative NOMA system. We first derive the outage probabilities of the relay user (RU) and the destination user (DU) with selection combining. Based on these probabilities, the outage probability of the cooperative NOMA system is obtained. The analytical results are verified by Monte Carlo simulation. It is noticed that the outage probability of cooperative NOMA system has a convex function, the optimum power allocation coefficient, which satisfied the minimum outage probability, is calculated. Numerical examples show that the optimal power allocation coefficient increases with the required capacity of DU. While the capacity of DU is fixed, we noticed that the increase of the required capacity of RU decreases the optimal power allocation coefficient.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.367-370
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• 2017

This paper proposes a method for selecting efficient relay nodes in stochastic DTN model. Delay Tolerant Network (DTN) uses the Carry and Forward method, which creates a bundle layer for efficient communication, selects relay nodes between different networks and heterogeneous networks, and forwards messages. DTN is basically composed of mobile nodes so DTN has no fixed routing route and it has long latency due to intermittent connection. Therefore, the nodes constituting the DTN necessarily have the characteristics to store the messages, and the capacity of the stored messages and nodes affects the performance of the network. Stochastic DTN model proposed a Markov model that changes randomly over time to analyze the performance of DTN. In this paper, we use stochastic message distribution and node contact probabilities using contact time analyzed through message generation and extinction in order to select efficient relay nodes in stochastic DTN model.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.75-80
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• 2011

In the cooperative communication, The relay that transmit signal to destination can achieve diversity gain. But transmitter and relay must have own frequency to transmit signal to destination. If Relay is secondary user and does not have own frequency, relay can't transmit signal to destination. So, To analysis performance of cognitive radio We need to consider detection probability of secondary user. In the paper we propose cooperative communication system considering detection probability. And to compare proposed system and conventional, we also simulate incremental cooperative communication. Through the simulation result, we can know that BER performance of proposed scheme is better than incremental relaying in the cognitive radio.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1138-1146
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• 2005

This paper makes a study of a formulation of net filter discrimination(NFD) and its computation for analyzing adjacent channel interference and suggests a systematic algorithm for calculating protection ratios of co-channel and adjacent channel applicable to frequency coordination in the fixed radio relay networks. It is shown that adjacent channel protection ratio can be derived from two factors: One is NFD depending upon receiver filter characteristic as well as transmitter spectrum mask and the other is co-channel protection ratio given by a function of fade margin, modulation scheme, and allowable interference. Actually to show the computing procedure from transmitter spectrum mask and receiver filter characteristic, NFD has been obtained for channel bandwidth of 29.65 and 40 MHz at 6.2 and 6.7 GHz band, respectively. According to the results, NFDs at the first adjacent channel of 29.65 and 40 MHz provide 27.4 and 28.9 dB, respectively. From these data, adjacent channel protection ratios corresponding to each channel bandwidth yield 47.5 and 46.3 dB for a given 64-QAM and 60 km. The proposed method gives some merits of an easy calculation, systematic extension, and applying the same concept to frequency coordination in millimeter radio relay networks.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.104-114
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• 2005

This work presents a concept and the related analysis of the traffic performance for a wireless broadband system based on fixed relay stations acting as wireless bridges. The analysis focuses on the important performance indicators end-to-end throughput and delay, taking into account the effects of an automated repeat request protocol. An extension to a MAC frame based access protocol like IEEE 802.11e, 802.15.3, 802.16a, and HIPERLAN2 is outlined and taken as basis for the calculations. The system is intended for both dense populated areas as an overlay to cellular radio systems and to provide wide-area broad-band coverage. The two possible deployment scenarios for both dense urban and wide-area environments are introduced. Analytical and validating simulation results are shown, proving the suitability of the proposed concept for both of the mentioned scenarios. It is established that the fixed relaying concept is well suited to substantially contribute to provide high capacity cellular broad-band radio coverage in next generation (NG) cellular wireless broadband systems.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.253-254
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• 2008

본 연구는 다중 안테나 배열 시스템을 응용한 고정 중계기가 적용된 상향 링크 셀룰러 환경에서 효과적으로 외곽 사용자의 QoS(Quality of Service)를 개선시키고 보다 높은 수준의 전체 데이터 전송률을 보장하는 기술을 제안한다.