• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1147-1155
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• 2008

In this paper, we derive the probability density function (PDF) of end-to-end signal-to-noise ratio (SNR) for t he dual-hop MIMO (Multiple-Input Multiple-Output) DCF (Decouple-and-Forward) system. We also provide the end-to-end bit error ratio (BER) with M-ary PSK constellations for four antenna combinations. These are (1,8,1), (8,1,8), (2,4,2), and (4,2,4). Each number in the parentheses is the number of the transmit antenna at the source, the transmit and receive antenna at the relay and the receive antenna at the destination, respectively. We show t hat the end-to-end BER expression with M-ary PSK constellations makes an exact match with numerical results. We also show that MIMO DCF relay system achieves spatial diversity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.924-944
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• 2014

This paper investigates the power allocation and outage performance of MIMO full-duplex relaying (MFDR), based on orthogonal space-time block codes (OSTBC), in cognitive radio systems. OSTBC transmission is used as a simple means to achieve multi-antenna diversity gain. Cognitive MFDR systems not only have the advantage of increasing spectral efficiency through spectrum sharing, but they can also extend coverage through the use of relays. In cognitive MFDR systems, the primary user experiences interference from the secondary source and relay simultaneously, owing to full duplexing. It is therefore necessary to optimize the transmission powers at the secondary source and relay. In this paper, we propose an optimal power allocation (OPA) scheme based on minimizing the outage probability in cognitive MFDR systems. We also analyse the outage probability of the secondary user in noise-limited and interference-limited environments in Nakagami-m fading channels. Simulation results show that the proposed schemes achieve performance improvements in terms of reducing outage probability.

• Journal of information and communication convergence engineering
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• v.12 no.2
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• pp.67-74
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• 2014

In multi-hop communication systems, two-way relaying is one of the solutions to mitigate the spectral efficiency loss caused by a half-duplex transmission. In this paper, a simple two-way relaying scheme is proposed for two-hop two-user multiple input multiple output (MIMO) systems. In the proposed system, a base station and a relay station (RS), both equipped with two antennas, form a point-to-point MIMO channel, while the RS and two single-antenna mobile users form a point-to-multipoint multiuser (MU)-MIMO channel. Numerical examples show that the proposed system achieves a significant sum rate gain as compared to a one-way relaying system as the distance between a relay and the two users decreases. We also show that although we can expand the proposed scheme to more than two users, its performance gain as compared to that of one-way relaying decreases with an increase in the number of users.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.8
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• pp.2722-2742
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• 2014

We propose methods of linear transceiver design for two different power constraints, sum relay power constraint and per relay power constraint, which determine signal processing matrices such as base station (BS) transmitter, relay precoders and user receivers to minimize sum mean square error (SMSE) for multi-relay multi-user (MRMU) networks. However, since the formulated problem is non-convex one which is hard to be solved, we suboptimally solve the problems by defining convex subproblems with some fixed variables. We adopt iterative sequential designs of which each iteration stage corresponds to each subproblem. Karush-Kuhn-Tucker (KKT) theorem and SMSE duality are employed as specific methods to solve subproblems. The numerical results verify that the proposed methods provide comparable performance to that of a full relay cooperation bound (FRCB) method while outperforming the simple amplify-and-forward (SAF) and minimum mean square error (MMSE) relaying in terms of not only SMSE, but also the sum rate.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.53-58
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• 2011

Recently, MIMO technology, which can improve data rate, link reliability and diversity order, has been widely studied. However, due to the limitation of size, cost and complexity, it is difficult to equip multiple antennas in mobile devices. To overcome this problem, the cooperative communication scheme has been proposed. In this scheme, each terminal shares its single antenna to form a virtual MIMO environment. However, in conventional cooperative scheme, e.g, decode-and-forward, amplify and forward, the spectral efficiency is decreased if there are many terminals taking part in the cooperation. Therefore, the incremental relaying scheme has been proposed to solve this problem. In this paper, we consider various models using incremental relaying technique. In addition, the position of relay is investigated in order to obtain optimal performance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.29-34
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• 2011

In this paper, we propose antenna and relay selection system by considering channel environment between nodes. Each node has multiple antennas in each hop. And, we analyze the performance of proposed system. A General MIMO system receives signals through multiple channels and obtains diversity gain. But MIMO system causes performance degradation due to poor received signals. The proposed system consider transmitters-relays channels, relays-receivers channels and select a best channel. This channel selection prevents performance degradation and increase total system's performance. Therefore, we must select best antennas and a best relay, simultaneously.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.1
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• pp.168-186
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• 2016

In this paper, we investigate the degrees of freedom (DoF) of a two-cluster multiple-input multiple-output (MIMO) multiway relay interference channel (mRIC), where there are two relays and two users per cluster. In this channel, users within the same cluster exchange messages among themselves with the help of two relays.We first obtain the DoF upper bound of the considered MIMO mRIC based on cut-set bound. Then, we propose a novel transmission strategy, blind interference neutralization (BIN), to approach the DoF upper bound. This new method utilizes the overheard information at two relays and focuses on the beamforming matrix designs at two relays so that the channel state information (CSI) at users is not required. Through theoretical analysis and numerical simulations, we show that the DoF upper bound can be obtained by using the BIN scheme. From simulation results, we show that the proposed BIN scheme can provide significant performance gain over the conventional time division multiple access (TDMA) scheme in terms of DoF. In addition, we show that the BIN scheme is a superior approach to the existing signal space alignment (SSA) schemes for the considered mRIC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.746-752
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• 2012

SVC layered video is consists of a Base Layer (BL) and Enhancement Layer (EL). Without the base layer decoding, the higher EL layer can not be decoded. Therefore, successful transfer of the BL is important factor for improving the SVC video data. In this paper, we propose a network coding of layered video to improve success decoding probability with the importance order of the video data over a multi-relay system. We shows that formula analysis and experimental results of the proposed network coding scheme. In addition, we shows performance of video quality according to the number of relays.

• ETRI Journal
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• v.34 no.2
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• pp.264-267
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• 2012

This letter analyzes the performance of a two-hop MIMO multiuser relay network with a fixed gain amplify-and-forward protocol and antenna selection at the transmitter and receiver. A new expression for the cumulative distribution function of the highest instantaneous end-to-end signal-to-noise ratio is derived. Based on the above result, closed-form expressions for outage probability and bit error rate are presented. Also, the diversity order of the system is determined. Finally, computer simulations are compared to the analytical results, and insights and observations are provided.

• Advances in Computational Design
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• v.3 no.2
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• pp.191-200
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• 2018

Establishment of an efficient routing technique in multiple-input-multiple-output (MIMO) based mobile ad hoc network (MANET) is a new challenge in wireless communication system to communicate in a complex terrain where permanent infrastructure network implementation is not possible. Due to limited power of mobile nodes, a minimum power consumed routing (MPCR) algorithm is developed which is an integration of cooperative transmission process. This algorithm select relay node and support short distance communication. The performance analysis of proposed routing algorithm increased signal to noise interference ratio (SNIR) resulting effect of cooperative transmission. Finally performance analysis of the proposed algorithm is verified with simulated result.