• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.11
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• pp.3008-3025
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• 2012

In this paper, the downlink resource allocation of OFDMA system with decode-and-forward (DF) relaying is investigated. A non-convex optimization problem maximizing system throughput with users' satisfaction constraints is formulated with joint relay selection, subcarrier assignment and power allocation. We first transform it to a standard convex problem and then solve it by dual decomposition. In particular, an Optimal resource allocation scheme With Time-sharing (OWT) is proposed with combination of relay selection, subcarrier allocation and power control. Due to its poor adaption to the fast-varying environment, an improved version with subcarrier Monopolization (OWM) is put forward, whose performance promotes about 20% compared with that of OWT in the fast-varying vehicular environment. In fact, OWM is the special case of OWT with binary time-sharing factor and OWT can be seen as the tight upper bound of the OWM. To the best of our knowledge, such algorithms and their relation have not been accurately investigated in cooperative OFDMA networks in the literature. Simulation results show that both the system throughput and the users' satisfaction of the proposed algorithms outperform the traditional ones.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.5
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• pp.2177-2193
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• 2018

This paper studies resource allocation schemes for the relay-aided cooperative system consisting of multiple source-destination pairs and decode-forward (DF) relays. Specially, relaying selection, multisubcarrier pairing and assignment, and power allocation are investigated jointly. We consider a combinatorial optimization problem on quality of experience (QoE) and energy consumption based on relay-aided cooperative system. For providing better QoE and lower energy consumption we formulate a multi-objective optimization problem to maximize the total mean opinion score (MOS) value and minimize the total power consumption. To this end, we employ the nondominated sorting genetic algorithm version II (NSGA-II) and obtain sets of Pareto optimal solutions. Specially, two formulas are devised for the optimal solutions of the multi-objective optimization problems with and without a service priority constraint. Moreover, simulation results show that the proposed schemes are superior to the existing ones.

• Journal of information and communication convergence engineering
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• v.20 no.3
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• pp.143-152
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• 2022

The ongoing adoption of 5G will increase the data traffic, throughput, multimedia services, and power consumption for future wireless applications and services, including sensor and mobile networks. Multipath fading on wireless channels also reduces the system performance and increases energy consumption. To address these issues, device-to-device (D2D) and cooperative communications have been proposed. In this study, we propose two inter-clustering models using the relay selection method to improve system performance and increase energy efficiency in cooperative D2D networks. We develop two inter-clustering models and present their respective algorithms. Subsequently, we run a computer simulation to evaluate each model's outage probability (OP) performance, throughput, and energy efficiency. The simulation results show that inter-clustering model II has the lowest OP, highest throughput, and highest energy efficiency compared with inter-clustering model I and the conventional inter-clustering-based multirelay method. These results demonstrate that inter-clustering model II is well-suited for use in 5G overlay D2D and cellular communications.

• Journal of Korea Society of Digital Industry and Information Management
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• v.18 no.4
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• pp.13-21
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• 2022

Recently, in wireless video sensor networks(WVSN), various schemes for efficient video data transmission have been studied. In this paper, a layer based cooperative relaying(LCR) algorithm is proposed for minimizing scalable video transmission distortion from packet loss in WVSN. The proposed LCR algorithm consists of two modules. In the first step, a parameter based error propagation metric is proposed to predict the effect of each scalable layer on video quality degradation at low complexity. In the second step, a layer-based cooperative relay algorithm is proposed to minimize distortion due to packet loss using the proposed error propagation metric and channel information of the video sensor node and relay node. In the experiment, the proposed algorithm showed that the improvement of peak signal-to-noise ratio (PSNR) in various channel environments, compared to the previous algorithm(Energy based Cooperative Relaying, ECR) without considering the metric of error propagation.The proposed LCR algorithm minimizes video quality degradation from packet loss using both the channel information of relaying node and the amount of layer based error propagation in scalable video.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.7-13
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• 2009

In This Paper, we propose relay schemes for network-coding based two-way relay communication in multi relay channel. Two-way relay channel communication is a bi-directional communication that two users exchange their data with the help of a relay. Network-coding based Two-way relay communication can achieve more throughput compared to conventional two-way relay communication. In this paper, we propose relay selection schemes to provide maximum performance considering instantaneous signal-to-noise in multi-relay channel. Simulation results show that the proposed relay selection schemes can provide diversity order according to the number of relays.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.5
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• pp.421-427
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• 2009

This paper has proposed 1-2-1 coded cooperative communication that is a combination of STBC and ARQ. Coded cooperative communication is a protocol that integrates channel coding with cooperative communication. In this paper consider convolution encoder. ARQ method can increase the spectral efficiency than conventional cooperative communication because if the received signal from source node is satisfied by the destination preferentially, the destination transmits ACK message to both relay node and source node and then recovers the received signal. Where each relay 1, 2 forwards a punctured portion of receive data. When relay transmit to destination apply STBC the reliability to increase. Moreover this protocol can get better BER performance of receiver using simple comparator. We verified BER performance for the proposed protocol through Monte-Carlo simulation over Rayleigh fading plus AWGN.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.703-709
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• 2012

In this paper, we propose a hybrid decode-amplify-forward incremental cooperative diversity protocol using SNR-based relay selection. In the proposed protocol, whenever destination unsuccessfully receives the source's signal, one of relays that exploit hybrid decode-amplify-forward technique is chosen to retransmit the signal. We derive approximate closed-form expressions of outage probability and average channel capacity. Monte-Carlo simulations are presented to verify the theoretical results and compare the performance of the proposed protocol with the direct transmission protocol and conventional incremental relaying protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1138-1146
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• 2008

This paper considers 2-hop wireless cooperative communications networks with fixed decode-and-forward relays. Specifically, we first derive the closed-form BER expression for theoretically evaluating the end-to-end performance of these networks. Then, based on this expression and long-tenn fading statistics, we propose a power allocation method for source and relay. Such a method brings about multiple advantages in tenn of spectral efficiency and implementation complexity over other power allocation methods based on instantaneous fading statistics. A variety of numerical results reveal that the cooperative communications scheme with the proposed power allocation significantly outperforms that with the equal power allocation and the direct transmission scheme for any position of the relay subject to the same total transmit power constraint.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2262-2269
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• 2016

In IEEE 802.11 wireless LANs, when a source node with low data rate occupies the channel resource for a long time, network performance degrades. In order to improve performance, the cooperative communication has been proposed. In the previous cooperative communication protocols, relay nodes deliver data packets only for a source node. In this paper, we propose an additional transmission scheme in which relay nodes select an additional source node based on several information and deliver data packets for the original source node and the selected additional source node. The proposed scheme improves performance and provides fairness among source nodes. Performance of the proposed scheme is investigated by simulation. Our results show that the proposed scheme outperforms the previous protocol in terms of fairness index and throughput.

• ETRI Journal
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• v.35 no.4
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• pp.710-713
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• 2013

We propose a new space-time block coding (STBC) for asynchronous cooperative systems in full-duplex mode. The orthogonal frequency division multiplexing (OFDM) transmission technique is used to combat the timing errors from the relay nodes. At the relay nodes, only one OFDM time slot is required to delay for a pair-wise symbol swap operation. The decoding complexity is lower for this new STBC than for the traditional quasi-orthogonal STBC. Simulation results show that the proposed scheme achieves excellent performances.