• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6A
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• pp.405-419
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• 2012

In this paper, we propose a joint base station(BS) and relay precoders design in multi-relay aided multi-user all-multiple-input multiple-output(MIMO) system. The design criterion is to minimize user sum mean square error(SMSE) with 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 which the relay itself accesses, out of among all the 1st hop and the 2nd hop channel in the system. With BS precoder structure which is concatenated with block diagonalization(BD) precoder, each relay can determine its own precoder using only local CSI. Proposed scheme is based on sequential iteration of two stages; stage 1 determines BS precoder and relay precoders jointly with SMSE duality, and stage 2 determines user receivers. Proposed scheme can be demonstrated theoretically to be always converge. We verify that proposed scheme outperforms simple amplify-and-forward(SAF), MMSE relay, and proposed schemes in [1] in terms of both SMSE and sum-rate performances.

• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.4
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• pp.213-219
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• 2017

Streaming server is that an image produced in real time or a file form of image produced ahead consists of SNS service, and the relay module of streaming server includes output management module that set an output channel more than 2 and control transmission of video content. This thesis intends to suggest how to stream through plural output channel that contains output channel of external streaming server using relay module and do streaming provided to terminal receiving image, and streaming server, streaming system for this. Thus, by extending output channel sending out image to output channel of external streaming server, the scale of streaming server is not limited and the process allotting external streaming server into output channel sending the image becomes simple, so management of output channel becomes efficient even when sending several images.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.562-570
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• 2011

In this paper, a distributed mobile relay power control (DMRPC) scheme for maximizing individual cell throughput is proposed for mobile relay aided multi-cell orthogonal frequency division multiplexing (OFDM)-time division duplex (TDD) system. In the system with DMRPC, the power levels of relay's are controlled by individual cell without cell cooperation and signalling overhead. It is demonstrated by numerical simulation that DMRPC provides the better cell throughput performance than either the full power relay aided system or conventional system without relay does. Moreover, it is also shown that relay aided systems with DMRPC, and the conventional system have almost identical cell edge throughput, while full power relay aided systems show worse performance in cell edge throughput.

• 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

• 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 the Korea institute of electronic communication sciences
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• v.10 no.6
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• pp.671-676
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• 2015

Cooperative networks eliminate shadow area using relay and enhance communication performance by creating virtual multi input multi output (MIMO) system. In this paper, we analyze the performance of cooperative networks which use coherent modulation scheme in source-relay nodes and differential modulation scheme in relay-destination nodes depending on the relay location. We consider the performance analysis of systems with and without the direct transmission between source and destination node where the direct transmission adopts differential modulation scheme. In addition, the performance of the system with fully differential modulation scheme is compared with the system using partially differential modulation scheme. The performance of system is based on the symbol error rate between source and destination node.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.10
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• pp.5035-5057
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• 2019

Advancements in nanotechnology and novel nano materials in the past decade have provided a set of tools that can be used to design and manufacture integrated nano devices, which are capable of performing sensing, computing, data storing and actuation. In this paper, we have proposed cooperative nano communication using Power Switching Relay (PSR) Wireless Power Transfer (WPT) protocol and Time Switching Relay (TSR) WPT protocol over independent identically distributed (i.i.d.) Rayleigh fading channels in the Terahertz (THz) Gap frequency band to increase the range of transmission. Outage Probability (OP) performances for the proposed cooperative nano communication networks have been evaluated for the following scenarios: A) A single decode-and-forward (DF) relay for PSR protocol and TSR protocol, B) DF multi-relay network with best relay selection (BRS) for PSR protocol and TSR protocol, and C) DF multi-relay network with multiple DF hops with BRS for PSR protocol and TSR protocol. The results have shown that the transmission distance can be improved significantly by employing DF relays with WPT. They have also shown that by increasing the number of hops in a relay the OP performance is only marginally degraded. The analytical results have been verified by Monte-Carlo simulations.

• ETRI Journal
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• v.39 no.5
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• pp.729-736
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• 2017

This work investigates secure cluster-aided multi-hop randomize-and-forward networks. We present a hop-by-hop multi-hop transmission scheme with relay selection, which evaluates for each cluster the relays that can securely receive the message. We propose an analytical model to derive the secure connectivity probability (SCP) of the hop-by-hop transmission scheme. For comparison, we also analyze SCPs of traditional end-to-end transmission schemes with two relay-selection policies. We perform simulations, and our analytical results verify that the proposed hop-by-hop scheme is superior to end-to-end schemes, especially with a large number of hops or high eavesdropper channel quality. Numerical results also show that the proposed hop-by-hop scheme achieves near-optimal performance in terms of the SCP.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.8
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• pp.365-372
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• 2001

This paper presents a new protection concept to achieve the adaptive optimal function by introducing the multi-agent system technology. Making each relay an agent which consists of relay agent module and coordinator module, each agent works autonomously to improve protection capability by cooperating with other agents. It is applied to the overcurrent protection system of the industrial power system in order to show the feasibility of the proposed methodology.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.325-338
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• 2012

In this paper, a radio resource allocation scheme for a multi-hop relay transmission in cognitive radio (CR) system is proposed to support the employment of relay nodes in IEEE 802.22 standard for wireless regional area network (WRAN). An optimization problem is formulated to maximize the number of serving secondary users (SUs) under system constraints such as time-divided frame structure for multiplexing and a single resource-unit to every relay-hop. However, due to mathematical complexity, the optimization problem is solved with a sub-optimal manner instead, which takes three steps in the order of user selection, relay/path selection, and frequency selection. In the numerical analysis, this proposed solution is evaluated in terms of service rate denoting as the ratio of the number of serving SUs to the number of service-requesting SUs. Simulation results show the condition of adopting multi-hop relay and the optimum number of relaying hops by comparing with the performance of 1-hop system.