• 한국멀티미디어학회논문지
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• 제17권6호
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• pp.687-696
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• 2014

An integrated ship area network has functionality of remote control and autonomous management of various sensors and instruments embedded or boarded in a ship. For such environment, an wireless bridge is essential to transmit control and/or managing information to sensors or instruments from a central integrated ship area network station. In this paper, one of reliable schemes of WiMedia based wireless bridge using relay cooperative transmission using WiMedia distributed MAC protocol is proposed to increase a communication reliability between cluster headers, irrespective of channel variation. Simulation results show that the proposed wireless bridge using relay cooperative transmission scheme increases communication reliability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5361-5374
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• 2016

Combining channel coding and network coding in a physical layer in a fading channel, generalized joint channel-network coding (G-JCNC) is proved to highly perform in a two-way relay channel (TWRC). However, most relevant discussions are restricted to symmetric networks. This paper investigates the G-JCNC protocols in an asymmetric TWRC (A-TWRC). A newly designed encoder used by source nodes that is dedicated to correlate codewords with different orders is presented. Moreover, the capability of a simple common non-binary decoder at a relay node is verified. The effects of a power match under various numbers of iteration and code lengths are also analyzed. The simulation results give the optimum power match ratio and demonstrate that the designed scheme based on G-JCNC in an A-TWRC has excellent bit error rate performance under an appropriate power match ratio.

• ETRI Journal
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• 제36권4호
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• pp.625-634
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• 2014

This paper studies a dual-hop multiple-access relay network where two independent source nodes transmit information to a common destination node with the aid of multiple single-antenna amplify-and-forward relays. Each relay node is subject to an individual power constraint. We focus on the design of distributed beamforming schemes for the relays to support the transmission rate requirements of the two sources. To this end, we first characterize the achievable rate region for this network via solving a sequence of corner point optimization problems proposed in this paper. We also develop several low-complexity suboptimal schemes in closed form. Two inner bounds of the achievable rate region are theoretically shown to be approximately optimal in two special scenarios. Finally, numerical results demonstrate the effectiveness of our proposed approaches.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권5호
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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.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 추계학술대회
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• pp.54-56
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• 2013

직교 주파수 분할 다중 접속 (OFDMA) 방식을 사용하는 중계 시스템에서는 기지국, 중계기, 사용자에게 어떤 주파수를 할당하느냐에 따라 성능이 달라질 수 있다. 본 논문에서는 OFDMA 중계 시스템에서 인접셀 간섭과 네트워크 코딩을 고려하여 주파수를 할당하는 기법을 제안한다. 네트워크 코딩을 사용하는 구간에서는 중계기가 기지국과 사용자에게 네트워크 코딩을 이용하여 동시에 전송할 수 있는 환경을 고려한다. OFDMA 중계 시스템에서 하향 링크와 상향 링크 및 네트워크 코딩으로 동작하는 구간을 나누고, 각 구간별로 기지국, 중계기, 사용자가 이용하는 주파수를 인접셀 간섭을 고려하여 할당해준다. 제안하는 주파수 할당 기법에 대해서 시뮬레이션을 통해 성능 평가를 수행한다.

• 방송공학회논문지
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• 제15권6호
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• pp.783-790
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• 2010

양방향 중계 네트워크는 중계기에 중첩 부호화 또는 네트워크 부호화를 적용함으로써 기존의 단방향 중계 네트워크에 비해 향상된 주파수 효율을 제공한다. 한편, OFDMA 네트워크는 사용자에게 부반송파, 파워 등의 자원을 적응적으로 할당하여 네트워크의 성능향상을 얻을 수 있다. 본 논문에서는 복호후재전송을 사용하는 양방향 OFDMA 중계 네트워크에서 다중사용자를 위한 적응적 부반송파 할당 알고리즘을 제안한다. 제안된 알고리즘은 각 사용자 쌍의 최소 전송속도를 보장하며 모든 사용자 쌍에 대한 달성 합 전송속도를 최대화하기 위해 부반송파를 사용자 쌍과 중계기에 적응적으로 할당한다. 모의실험을 통해 제안된 알고리즘이 정적 알고리즘, 그리디 알고리즘 보다 우수한 성능을 보임을 확인한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5149-5173
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• 2016

Cooperative forwarding has shown a substantial network performance improvement compared to traditional routing in multi-hop wireless network. To further enhance the system throughput, especially in the presence of highly congested multiple cross traffic flows, a promising way is to incorporate the multi-radio multi-channel (MRMC) capability into cooperative forwarding. However, it requires to jointly address multiple issues. These include radio-channel assignment, routing metric computation, candidate relay set selection, candidate relay prioritization, data broadcasting over multi-radio multi-channel, and best relay selection using a coordination scheme. In this paper, we propose a simple and efficient cluster-based cooperative data forwarding (CCDF) which jointly addresses all these issues. We study the performance impact when the same candidate relay set is being used for multiple cross traffic flows in the network. The network simulation shows that the CCDF with MRMC not only retains the advantage of receiver diversity in cooperative forwarding but also minimizes the interference, which therefore further enhances the system throughput for the network with multiple cross traffic flows.

• Journal of Communications and Networks
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• 제14권3호
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• pp.257-266
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• 2012

A decode-and-forward two-way relay system benefits from orthogonal frequency division multiplexing (OFDM) and relay transmission. In this paper, we consider a decode-and-forward two-way relay system over OFDMwith two strategies: A joint subcarrier matching algorithm and a power allocation algorithm operating with a total power constraint for all subcarriers. The two strategies are studied based on average capacity using numerical analysis by uniformly allocating power constraints for each subcarrier matching group. An optimal subcarrier matching algorithm is proposed to match subcarriers in order of channel power gain for both transmission sides. Power allocation is defined based on equally distributing the capacity of each hop in each matching group. Afterward, a modified water-filling algorithm is also considered to allocate the power among all matching groups in order to increase the overall capacity of the network. Finally, Monte Carlo simulations are completed to confirm the numerical results and show the advantages of the joint subcarrier matching, power allocation and water filling algorithms, respectively.

• 한국인터넷방송통신학회논문지
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• 제9권5호
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• pp.31-37
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• 2009

양방향 중계 채널에서는 중계기가 복호 후 재전송 혹은 증폭 후 재전송 프로토콜을 기반으로 두 사용자에게 네트워크 부호화된 신호를 전송한다. 이러한 양방향 중계 채널 시스템에서 신호 대 잡음비(SNR)가 낮은 환경에서는 복호 후 재전송 프로토콜이 최대 전송량을 가지고, 신호 대 잡음비가 높은 환경에서는 증폭 후 재전송 프로토콜이 최대 전송량을 가진다. 따라서 본 논문에서는 양방향 중계 채널에서 중계기가 수신한 신호 대 잡음비에 따라 증폭 후 재전송(Amplify-and-Forward, AF) 혹은 복호 후 재전송(Decode-and-Forward, DF)프로토콜을 결정하는 능동적인 전송 기법을 제안하였다. 전송 기법이 스위칭(switching)되는 최적의 임계값을 계산하였고, 제안하는 기법이 기존의 양방향 중계 채널에서의 전송 기법보다 우수한 전송량을 보임을 수식적인 결과를 통해 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권10호
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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.