• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.795-798
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• 2007

In this paper, we proposed a simple power allocation scheme to maximize network lifetime. To maximize network lifetime, it is important to allocate power fairly among nodes in a network as well as to minimize total transmitted power. In the proposed scheme, the allocated power is proportional to the residual power and also satisfies the required SNR at destination node. In this paper, we calculate power allocation in "amplify and forward" (AF) model. We evaluated the proposed power allocation scheme using extensive simulation and simulation results show that proposed power allocation obtains much longer network lifetime than the equal power allocation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4223-4239
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• 2016

In this paper, we consider an amplify-and-forward (AF) full-duplex relay network (FDRN) using simultaneous wireless information and power transfer, where a battery-free relay node harvests energy from the received radio frequency (RF) signals from a source node and uses the harvested energy to forward the source information to destination node. The time-switching relaying (TSR) protocol is studied, with the assumption that the channel state information (CSI) at the relay node is imperfect. We deliver a rigorous analysis of the outage probability of the proposed system. Based on the outage probability expressions, the optimal time switching factor are obtained via the numerical search method. The simulation and numerical results provide practical insights into the effect of various system parameters, such as the time switching factor, the noise power, the energy harvesting efficiency, and the channel estimation error on the performance of this network. It is also observed that for the imperfect CSI case, the proposed scheme still can provide acceptable outage performance given that the channel estimation error is bounded in a permissible interval.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1194-1199
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• 2010

In this paper, for a relay-based cellular network, a interference avoidance beamforming technique is proposed to enhance direct link capacity while minimizing loss in the capacity of concurrent relaying link. A direct link is transmitted by beamforming at the transmitter, and the relaying link with the least interference to the direct link is scheduled to transmit data by a collision avoidance scheduling algorithm. Simulation results show that the proposed IA beamforming provides a considerable direct link capacity enhancement while minimizing relaying link capacity loss by effectively mitigating inference between concurrent direct and relaying links only with limited feedback.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4967-4986
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• 2015

Multi-hop relaying communications have great potentials in improving transmission performance by deploying relay nodes. The benefit is critically dependent on the accuracy of the channel state information (CSI) of all the transmitting links. However, the CSI has to be estimated. In this paper, we investigate the channel estimation problem in one-way multi-hop MIMO amplify-and-forward (AF) relay system, where both the two-hop and three-hop communication link exist. Traditional point-to-point MIMO channel estimation methods will result in error propagation in estimating relay links, and separately tackling the channel estimation issue of each link will lose the gain as part of channel matrices involved in multiple communication links. In order to exploit all the available gains, we develop a novel channel estimation model by structuring different communication links using the PARAFAC and PARATUCK2 tensor analysis. Furthermore, a two-stage fitting algorithm is derived to estimate all the channel matrices involved in the communication process. In particular, essential uniqueness is further discussed. Simulation results demonstrate the advantage and effectiveness of the proposed channel estimator.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4432-4450
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• 2014

It is widely observed that in practical wireless cooperative communication systems, different links may experience different fading characteristics. In this paper, we investigate into the outage probability and channel capacity of two-way amplify-and-forward (TWAF) relaying systems operating over a mixed asymmetric Rician and Rayleigh fading scenario, with different amplification policies (AP) adopted at the relay, respectively. As TWAF relay network carries concurrent traffics towards two opposite directions, both end-to-end and overall performance metrics were considered. In detail, both uniform exact expressions and simplified asymptotic expressions for the end-to-end outage probability (OP) were presented, based on which the system overall OP was studied under the condition of the two source nodes having non-identical traffic requirements. Furthermore, exact expressions for tight lower bounds as well as high SNR approximations of channel capacity of the considered scenario were presented. For both OP and channel capacity, with different APs, effective power allocation (PA) schemes under different constraints were given to optimize the system performance. Extensive simulations were carried out to verify the analytical results and to demonstrate the impact of channel asymmetry on the system performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2949-2963
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• 2019

A novel distributed compress-and-forward (CF) system based on multi-relay network is presented. In this system, as the direct link between the source and destination is invalid due to some reasons, such as the limited power, special working environment, or even economic factors, relays are employed to receive analog signals and carry on distributed compressed encoding. Subsequently, the digital signals are transmitted to the destination via wireless channel. Moreover, a theoretical analysis for the system is provided by utilizing the Chief Executive Officer (CEO) theory and Shannon channel capacity theory, and the rate-distortion function as well as the connection between the transmission rate and the channel capacity are constructed. In addition, an optimal signal-to-noise ratio (SNR) -based power allocation method is proposed to maximize the quantization SNR under the limited total power. Simulation result shows that the proposed CF system outperforms the amplify-and-forward (AF) system versus the SNR performance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.61-66
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• 2011

Cooperative Communication using relays which include network separated into fixed cooperative relaying and incremental cooperative relaying defending on method receiving signal from a source. If some nodes included network is Primary user ad source and destination, another is Secondary user as relay, The nodes included network excepting source can help PU transmit signal. In the case of all of SU playing a role as relay, destination can get diversity gain, but useless time slot is consumed for transmitting signal. So in this paper, we analysis cooperative relaying which a node succeeding to sense primary signal send signal to destination. We use matlab simulation tool and consider AF, DF, fixed relaying, incremental relaying

• Journal of Advanced Information Technology and Convergence
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• v.9 no.1
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• pp.25-37
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• 2019

Power-line communication (PLC) has influenced smart grid development. In addition, PLC has also been instrumental in current research on internet-of-things (IoT). Due to the implementation of PLC in smart grid and IoT environments, strides have been made in PLC and its combination with the wireless system to form a hybrid communication system. Also, PLC has evolved from a single-input-single-output (SISO) configuration to multiple-input-multiple-output (MIMO) configuration system, and from a point-to-point communication system to cooperative communication systems. In this work, we extend a MIMO wireless two-way amplify-and-forward (AF) cooperative communication system to a hybrid PLC and wireless (PLC/W) system configuration. We then maximize the weighted sum-rate for the hybrid PLC/W by optimizing the precoders at each node within the hybrid PLC/W system. The sum-rate problem was found to be non-convex, therefore, an iterative algorithm is used to find the optimal precoders that locally maximize the system sum-rate. For our simulation results, we compare our proposed hybrid PLC/W configuration to a PLC only and wireless only configuration at each node. Due to an improvement in system diversity, the hybrid PLC/W configuration outperformed the PLC only and wireless only system configurations in all simulation results presented in this paper.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1117-1124
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• 2013

As the recently soaring wireless traffic, small-cell techniques have been actively studied in order to support such a wireless demand for cellular wireless networks. This paper focuses on the inter-cell interference neutralization to resolve the main barrier for implementing small-cell cellular networks. Assuming that each message is delivered to the final destination by the help of base stations or relays, ergodic interference neutralization is proposed, which exploits the time-varying nature of wireless channels. The previous approach based on amplify-and-forward (AF) suffers from severe performance degradation in the low signal-to-noise (SNR) regime due to noise amplification. On the other hand, the proposed interference neutralization based on recently developed compute-and-forward (CF) fixes such a problem and improves the performance in the low SNR regime.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4295-4316
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• 2018

In this paper, the performance of non-orthogonal multiple access (NOMA) dual-hop (DH) amplify-and-forward (AF) relaying networks is investigated, where Nakagami-m fading channel is considered. In order to cover more details, in our analysis, the transceiver hardware impairments at source, relay and destination nodes are comprehensively considered. To characterize the effects of hardware impairments brought in NOMA DH AF relaying networks, the analytical closed-form expressions for the exact outage probability and approximate ergodic sum rate are derived. In addition, the asymptotic analysis of the outage probability and ergodic sum rate at high signal-to-noise ratio (SNR) regime are carried out in order to further reveal the insights of the parameters for hardware impairments on the network performance. Simulation results indicate the performance of asymptotic ergodic sum rate are limited by levels of distortion noise.