• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.357-357
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• 2007

• Journal of electromagnetic engineering and science
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• v.12 no.3
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• pp.189-195
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• 2012

In this paper, we propose a novel protocol called a Multi-hop Diversity Transmission protocol in which the retransmission is realized by a relay that is Nearest to a current Source (MDTNS). We derive the mathematical expressions of the packet error rate (PER) and the average number of transmissions over Nakagami-m fading channels, and verify them by Monte Carlo simulations. The simulation results show that the MDTNS protocol improves the performance of the network in terms of PER when compared to the Multi-hop Diversity Transmission protocol in which the retransmission is done by a relay that is Nearest to Destination (MDTND) and to the conventional multi-hop transmission (CMT) protocol.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.97-98
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• 2007

In this paper, we investigate the throughput capacity of a multi-hop relay network with cognitive radio (CR) enabled relay stations (RS). We suggested a TDMA/FDMA based frame structure where RSs dynamically select unused channels to communicate with the base station (BS) using CR techniques to analyze the throughput capacity. We developed the throughput capacity model for the proposed system based on utilization factor. The analytical results based on those equations show significant improvement in throughput capacity for CR enabled multi-hop relay system.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.394-397
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• 2008

Recently WiBro network is installed for high speed wireless internet service by telecommunication service provider, however WiBro service is not provided in the region of mountain or difficult region to install network infra. Fixed repeater is used to resolve those shadow area problem in current WiBro network. This paper study introducing Ad-hoc based multi-hop relay instead of using fixed repeater in order to resolve those shadow area problem. Cost down of fixed repeater and active network expansion is possible to resolve shadow area problem by introducing multi-hop relay technology.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.19-26
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• 2016

In this paper, the performance of dual-hop multi-relay maximum ratio transmission (MRT) over Rayleigh flat fading channels is studied with both conventional (all relays participate the transmission) and opportunistic (best relay is selected to maximize the received signal-to-noise ratio (SNR)) relaying. Performance analysis starts with the derivation of the probability density function, cumulative distribution function and moment generating function of the SNR. Then, both approximate and asymptotic expressions of symbol error rate (SER) and outage probability are derived for arbitrary numbers of antennas and relays. With the help of asymptotic SER and outage probability, diversity and array gains are obtained. In addition, impact of imperfect channel estimations is investigated and optimum power allocation factors for source and relay are calculated. Our analytical findings are validated by numerical examples which indicate that multi-relay MRT can be a low complexity and reliable option in cooperative networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.10
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• pp.2732-2749
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• 2023

Device-to-Device (D2D) communication has received increasing attention and been studied extensively thanks to its advantages in improving spectral efficiency and energy efficiency of cellular networks. This paper proposes a novel relay selection algorithm for multi-hop full-duplex D2D communications underlaying cellular networks. By selecting the relay of each hop in a reverse manner, the proposed algorithm reduces the heavy signaling overhead that traditional relay selection algorithms introduce. In addition, the social domain information of mobile terminals is taken into consideration and its influence on the performance of D2D communications studied, which is found significant enough not to be overlooked. Moreover, simulations show that the proposed algorithm, in absence of social relationship information, improves data throughput by around 70% and 7% and energy efficiency by 64% and 6%, compared with two benchmark algorithms, when D2D distance is 260 meters. In a more practical implementation considering social relationship information, although the proposed algorithm naturally achieves less throughput, it substantially increases the energy efficiency than the benchmarks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.133-138
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• 2011

This paper presents an information theoretic outage analysis for physical layer of a cooperative multihop wireless network. Our analysis shows that cooperation by selecting a proper relay at each hop increases the coverage or data rate of the network. In our analysis we consider both symmetric and asymmetric network model. We also investigate the availability of cooperative relay at each hop and show that end-to-end performance of the network depends on the relay selection procedure at each hop. We also verify our analytical results with simulations.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.3
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• pp.200-209
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• 2017

In this paper, we investigate the tradeoff between security and reliability for a multi-hop protocol in cluster-based underlay cognitive radio networks. In the proposed protocol, a secondary source communicates with a secondary destination via the multi-hop relay method in the presence of a secondary eavesdropper. To enhance system performance under the joint impact of interference constraint required by multiple primary users and hardware impairments, the best relay node is selected at each hop to relay the source data to the destination. Moreover, the destination is equipped with multiple antennas and employs a selection combining (SC) technique to combine the received data. We derive closed-form expressions of the intercept probability (IP) for the eavesdropping links and the outage probability (OP) for the data links over a Rayleigh fading channel. Finally, the correction of our derivations is verified by Monte-Carlo simulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2616-2635
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• 2013

In this paper, we propose an iterative transceiver design in a multi-relay multi-user multiple-input multiple-output (MIMO) system. The design criterion is to minimize sum mean squared error (SMSE) under relay sum power constraint (RSPC) where only local channel state information (CSI)s are available at relays. Local CSI at a relay is defined as the CSI of the channel between BS and the relay in the $1^{st}$ hop link, and the CSI of the channel between the relay and all users in the $2^{nd}$ hop link. Exploiting BS transmitter structure which is concatenated with block diagonalization (BD) precoder, each relay's precoder can be determined using local CSI at the relay. The proposed scheme is based on sequential iteration of two stages; stage 1 determines BS transmitter and relay precoders jointly with SMSE duality, and stage 2 determines user receivers. We verify that the proposed scheme outperforms simple amplify-and-forward (SAF), minimum mean squared error (MMSE) relay, and an existing good scheme of [13] in terms of both SMSE and sum-rate performances.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.1
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• pp.187-199
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• 2016

In this paper, we consider secure communications in multi-hop relaying systems, where multiple decode-and-forward (DF) relays are located at each individual hop and perform cooperative beamforming to improve physical layer security. In order to determine the cooperative relay beamformer at each hop, we propose an iterative beamformer update scheme using semidefinite relaxation and bisection techniques. Numerical results are presented to verify the secrecy rate performance of the proposed scheme.