• The Journal of the Korea institute of electronic communication sciences
• /
• v.14 no.6
• /
• pp.1061-1068
• /
• 2019

Cooperative networks transmit signals form the source node to the destination node via several relay node where the combining and demodulation of relay aided signals provide the benefit of performance enhancement and data rate increment. In general, a repetitive manner transmission scheme in which the received signal from the source node is amplified/re-generated and forward to the destination node is widely used. In this paper, we analyzed the performance of cooperative networks using the mixed transmission scheme. The conventional modulation scheme is used in the source-relay links, and space-time code is applied in the relay-destination links. To reduce the complexity of the overall system, we adopt differential modulation which bypasses channel state information. We analyze bit error rate (BER) of the proposed system by considering the number of relay nodes, and the performances depending on the strength of transmission signal in the source-relays and rely-destination links are compared. In addition, we also discuss the system performance with the signal strength and the number of relay nodes simultaneously.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.12A
• /
• pp.941-949
• /
• 2011

In a cooperative communication system with a source node and multiple relays equipping single antenna and a destination node equipping multiple antennas, the selective cooperative spatial multiplexing scheme can obtain spatial multiplexing gain and additional selection diversity gain. But it can degrade a bit error rate performance because some received symbols forwarded from particular relays may be lost by attenuation due to path-loss. We propose a relay and transmission mode selection scheme which selects minimum number of multiple relays having the channel capacity larger than a given data rate and transmission mode which switches spatial multiplexing and spatial diversity mode in cooperation phase to enhance the bit error rate performance. The proposed scheme achieves 1.5~2dB gain at the low SNR range compared with the conventional scheme by obtaining additional spatial diversity gain.

• Journal of Broadcast Engineering
• /
• v.10 no.3
• /
• pp.372-382
• /
• 2005

DS/CDM-QPSK (ITU-R Recommendation BO.1130-4 Annex 6, 'Digital System E'), which has been adoptedas a standard of Korean Satellite DMB (Digital Multimedia Broadcasting) system, is a satellite-based multimedia broadcasting service which transmits the multi-channel and high quality contents to the terrestrial users through a satellite or gap-fillers. The broadcast from a satellite is directly received in the plain terrain which are within line-of-sight, but in cities where the broadcast cannot be received directly due to the shadow of buildings, an attempt is being made to install 'Gap-Fillers' to improve the reception in those areas. The gap-fillers, however, may induce interference to service of adjacent band, when their output power is substantially higher compared to the received signal power of signal from a satellite of the adjacent service. In this paper, a link budget analysis is performed, and the optimal EIRP of a gap-filler to maximize the gap-filler coverage, while preventing adjacent band interference is derived.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.5A
• /
• pp.408-413
• /
• 2009

In this paper, minimum mean-square-error (MMSE)-based transceiver processing of a bidirectional amplify-and-forward (AF) relay having multiple antennas is proposed. Besides, the optimal beamforming vectors of users are designed in the sense of the sum rate maximization. Simulation results show that the proposed relay processing can effectively reduce both co-channel interferences and self-interferences and that the proposed beamforming method is proper to the bidirectional communication employing the AF relay.

• Pallet News
• /
• s.59
• /
• pp.5-10
• /
• 2010

본 원고는 11월 11일 기술표준원 중강당에서 개최될 "2010년 APSF 유닛로드시스템컨퍼런스"의 발표원고로 아시아파렛트시스템연맹(APSF) 서병륜 회장의 아시아리터너블 파렛트시스템에 대한 비전을 제시하고 있습니다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2019.05a
• /
• pp.392-394
• /
• 2019

Tunnels and subterranean roads, which are representative evacuation facilities for national or regional disasters, have radio relay broadcasting facilities for legal reasons and convenience reasons. However, this system is limited to radio broadcasting and it is impossible to effectively communicate disaster or emergency situations that occur locally due to broadcasting of national broadcasting without DMB broadcasting. In order to improve this, we construct a remote disaster broadcasting system at each regional disaster station and implement a system to transmit it to each tunnel using internet or LTE network. The system in the tunnel transmits the emergency broadcasting signal through the existing relay equipment through the modulator which decodes the SMS, the media file, the real time broadcasting or the image received by the digital signal and converts it into FM and DMB frequency. The method proposed and implemented in this study can be used to provide efficient information and remote field control in case of emergency in tunnel and underground roadway.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.11
• /
• pp.18-24
• /
• 2009

This paper proposes two novel prediction-based adaptive selection cooperation schemes combined with a new relay selection strategy. In the proposed schemes, the destination predicts whether the transmission will be successful or not before a single relay is selected to transmit source's decoded data. Depending on the prediction, the destination feeds back a command to the whole network. Numerical results show that the proposed schemes combined with the relay selection strategy successfully reduce its outage probability, improve its throughput, save transmitted power, and prolong the lifetime of the network.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.2A
• /
• pp.91-99
• /
• 2011

Several repeater systems are used to enhance the cell coverage to location such as shadow and rural areas in mobile systems. But the general RF repeater solutions are not suitable for high power outdoor environment because it has the weakness such as self oscillation problem With adoption of a adaptive digital filter technology, feedback interference cancellation repeater prevents oscillation by detecting and canceling the unwanted feedback signal between transmission and receiver antenna. In this paper, dual NLMS based interference cancellation method is proposed and the step size adaptation can be implemented by the estimation of the feedback channel Doppler frequency characteristics. The performance of the proposed algorithm is quantified via analysis and simulation for the static and multipath fading feedback channels.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.12A
• /
• pp.1244-1250
• /
• 2007

User cooperation provides high reliability in wireless communication systems by employing relay nodes to transmit the same information. In this paper, a bit error rate (BER) study is presented for decode-and-forward (DF) relaying for user cooperation in independent and identically distributed Rayleigh fading channels. For an arbitrary number of relays, exact and closed-form expressions of the BER are proposed for M-ary PAM (Pulse Amplitude Modulation), QAM (Quadrature Amplitude Modulation) and PSK (Phase Shift Keying), respectively. It is also shown that the analytic results are perfectly matched with the simulated ones.

• The Journal of the Acoustical Society of Korea
• /
• v.28 no.6
• /
• pp.506-513
• /
• 2009

In this paper, we propose a bi-directional communication method applying time reversal technique in underwater acoustic channel in order to exchange data between sensor nodes with an available relay node. The proposed method reduces the conventional 4-step relaying procedure to 2-step and improves the system capacity. Moreover, it increases transmission range efficiently while the relay node can be implemented with low complexity. Simulation results demonstrate that the proposed scheme achieves 3.2 bps/Hz higher capacity than that of the conventional method at SNR 20 dB.