• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.9
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• pp.3152-3171
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• 2022

This work investigates the physical layer secrecy of a multi-antenna hybrid satellite-terrestrial relay networks (HSTRN) with jamming, in which a satellite aims to make communication with a destination user by means of a relay, along with spatially random eavesdroppers. In order to weaken the signals of eavesdroppers, the conventional relay can also generate intentional interference, besides forwarding the received signal. Shadowed-Rician fading is adopted in satellite link, while Rayleigh fading is adopted in terrestrial link, eavesdropper link and jamming link. The analytical and asymptotic formulas for the system secrecy outage probability (SOP) are characterized. Practical insights on the diversity order of the network are revealed according to the asymptotic behavior of SOP at high signal-to-noise ratio (SNR) regime. Then, analysis of the system throughput is examined to assess the secrecy performance. In the end, numerical simulation results are presented to validate the theoretical analysis and point out: (1) The secrecy performance of the considered network is affected by the channel fading scenario, the system configuration; (2) Decrease of the relay coverage airspace can provide better SOP performance; (3) Jamming from the relay can improve secrecy performance without additional network resources.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1402-1405
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• 2016

In this paper, we develop an interference neutralization (IN) method based on a set of multi-antenna relays for K-user interference channel. The feasibility condition for IN is fully characterized. We further provide a relaxed IN method for the cases in which there are not enough relays to satisfy the feasibility condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.213-220
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• 2009

Cooperative diversity is a promising technique for range extension and diversity increase without the use of multiple transmit antennas at the user equipment. In this paper, we propose a cooperative hybrid automatic repeat request relay method with adaptive retransmission to increase the throughput when the SNR of a source user is low. In the proposed method, the source user transmits the first segment of a codeword to relay users and a base station. If the base station fails to recover the information from the received packet, it requests the source or some relay users to retransmit the packet previously sent. In addition, the retransmission type of a selected user is chosen from repetition or incremental redundancy according to the quality of systematic bits in a turbo codeword. Simulation results show that the proposed method improves the throughput compared to conventional methods, and the improvement is significant when the source user has a low SNR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2C
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• pp.57-64
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• 2011

A two-way relay channel is a bidirectional cooperative communication channel between two nodes using a relay. In many cooperative communication schemes, a relay transmits its data to each node using separate channels. However, in the two-way relay channel, a relay can broadcast the network-coded signal to both nodes in a same time slot, which can increase the system throughput. In this paper, a new cooperative network error correcting scheme using distributed turbo code in a two-way relay channel is proposed. The proposed scheme not only increases the system throughput using network code but also improves the performance by utilizing the LLR information from relay node and other user node through distributed turbo code. Also, a power allocation scheme is investigated for various channel conditions to improve the system performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1638-1653
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• 2014

A sequential optimization algorithm (SOA) for resource allocation in a cyclic-prefixed single-carrier cognitive relay system is proposed in this study. Both subcarrier pairing (SP) and power allocation are performed subject to a primary user interference constraint to minimize the mean squared error of frequency-domain equalization at the secondary destination receiver. Under uniform power allocation at the secondary source and optimal power allocation at the secondary relay, the ordered SP is proven to be asymptotically optimal in maximizing the matched filter bound on the signal-to-interference-plus-noise ratio. SOA implements the ordered SP before power allocation optimization by decoupling the ordered SP from the power allocation. Simulation results show that SOA can optimize resource allocation efficiently by significantly reducing complexity.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.55 no.4
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• pp.183-189
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• 2006

In this work, the digital simulator for testing of digital protective relay is presented. The proposed simulator software has EMTP simulation data file conversion, sequence waveform generation, user define simulation data generation, communication engine, data analysis engine and measurements function etc. The simulator hardware is designed using 32bit floating point DSP architecture to achieve flexibility and high speed operation. This simulator is tested to evaluate the performance of relay simulator by using a output data of simulation model on EMTP.

• Journal of the Korea Society of Computer and Information
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• v.12 no.3
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• pp.267-275
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• 2007

In this paper, we designed and implemented DCS terminal remote monitoring middleware for real-time auditor and management terminal status signal with relay and fuse status at power management room. The middleware consist of four component as event analyzer, event manager, service manager and user interface. We expected economic effects extend relay life-time that pre-detected errors and prevented relay fault.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.5
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• pp.1944-1956
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• 2021

This paper considers a cellular two-way relay network with one base station (BS), one relay station (RS), and two users. The two users are far from the BS and no direct links exist, and the two users exchange messages with the BS via the RS. A non-orthogonal multiple access (NOMA) and network coding (NC)-based decode-and-forward (DF) two-way relaying (TWR) scheme TWR-NOMA-NC is proposed, which is able to reduce the number of channel-uses to three from four in conventional time-division multiple access (TDMA) based TWR approaches. The achievable sum-rate performance of the proposed approach is analyzed, and a closed-form expression for the sum-rate upper bound is derived. Numerical results show that the analytical sum-rate upper bound is tight, and the proposed TWR-NOMA-NC scheme significantly outperforms the TDMA-based TWR and NOMA-based one-way relaying counterparts.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2055-2061
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• 2022

In the event of a short-circuit accident on a 4.16 kV non-safety bus, the voltage is temporarily lowered as backflow occurs on the safety bus. In such cases, the undervoltage relay of the safety bus shall not pick up the undervoltage so as not to interfere with the operation of the safety motors. The aim of this study is to develop an adaptive undervoltage protection scheme for the 4.16 kV safety bus considering the faults on the 13.8 kV and 4.16 kV non-safety buses connected to secondary windings of the three winding transformers, UAT and SAT. The result of this study will be the adaptive undervoltage protection scheme for the safety bus of nuclear power plants satisfying functional requirements of the safety related medium voltage motors. The adaptive undervoltage protection scheme can be implemented into an integrated digital protective relay to make user friendly and reliable protection scheme.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.7-12
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• 2014

The data forwarding transmission is an important function of the relay in cooperative communication in wireless communication systems. However, additional relay cause the waste of power consumption and cost. Therefore, in this paper, we consider how to use the user mobile devices in stead of relays to deal with this problem. In this paper, we proposed the protocol that divide each relay into two states of idle and non-idle. The receiver has two functions of base station and user mobile device. In this case, it is possible that no additional cost, and improve the spectral efficiency and network capacity. We verified BER performance for the proposed protocol over Rayleigh fading through Monte-Carlo simulation.