• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.6
• /
• pp.2567-2582
• /
• 2016

This paper investigates the impact of outdated channel state information (CSI) on the performance of the incremental amplify-and-forward (AF) opportunistic relaying (OR) over dual-hop Rayleigh fading channels. According to the definition of distribution function, we obtain the cumulative distribution function (CDF) of the actual combined signal-to-noise ratio (SNR) received at the destination. Based on this CDF, the closed-form expressions of the average spectral efficiency and outage probability are derived for the incremental AF OR under outdated CSI. Numerical results show that in the low region of the average SNR of the direct link, outdated CSI deteriorates the system performance, whereas in the high region, outdated CSI has almost no impact on the system performance.

• 한국정보통신설비학회:학술대회논문집
• /
• 2009.08a
• /
• pp.329-332
• /
• 2009

In this paper, performance of cooperative communication system is analyzed with various relay conditions for mobile communication system using OFDM. We research mainly on the performance analysis of amplify-and-forward scheme. First, we analyzed the diversity gain between the number of antenna on the relay is one and two. And then, in this paper, we analyzed difference of the performance with distance between relay and mobile. Amplify-and-forward scheme has the problem that the noise components are also amplified in low sinal-to-noise (SNR) condition. The results of this paper can be applicable to the cooperative relay systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.5A
• /
• pp.408-413
• /
• 2009

In this paper, minimum mean-square-error (MMSE)-based transceiver processing of a bidirectional amplify-and-forward (AF) relay having multiple antennas is proposed. Besides, the optimal beamforming vectors of users are designed in the sense of the sum rate maximization. Simulation results show that the proposed relay processing can effectively reduce both co-channel interferences and self-interferences and that the proposed beamforming method is proper to the bidirectional communication employing the AF relay.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.3
• /
• pp.1131-1143
• /
• 2016

Differential detection schemes do not require any channel estimation, which can be employed under user mobility with low computational complexity. In this work, a soft-input soft-output (SISO) differential detection algorithm is proposed for amplify-and-forward (AF) over time-varying relaying channels based cooperative communications system. Furthermore, maximum-likelihood (ML) detector for M-ary differential Phase-shift keying (DPSK) is derived to calculate a posteriori probabilities (APP) of information bits. In addition, when the SISO is exploited in conjunction with channel decoding, iterative detection and decoding approach by exchanging extrinsic information with outer code is obtained. Finally, simulation results show that the proposed non-coherent approach improves detection performance significantly. In particular, the system can obtain greater performance gain under fast-fading channels.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.4A
• /
• pp.418-425
• /
• 2008

In this paper, we propose two different types of cooperative transmission protocols, referred to as spatial multiplexing with receive diversity (SMRD), that are bandwidth-efficient. We show that the BER performance can be significantly improved with a proper design of SMRD protocol under the AF (Amplify-and-Forward) and the DF (Decode-and-Forward) modes of relaying, when there is no interference among all symbols transmitted in the same time slot. BER analysis and our simulation result show that the proposed transmission protocol achieves a significant gain over no-cooperation (direct transmission) without any bandwidth expansion.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.5
• /
• pp.426-435
• /
• 2013

The diversity-multiplexing tradeoff (DMT) functions of three special half-duplex (HD) dynamic decode-and-forward (DDF) protocols with multiple antennas only at the source node, only at the destination node, and only at the relay node are analytically derived. The DMT functions of these three relay protocols are compared with one another and with those of the nonorthogonal amplify and forward (NAF) protocols.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.6
• /
• pp.94-102
• /
• 2009

In [1], the authors have proposed a novel scheme to achieve full diversity and to combat the time delays from each relay node, but decode-and-forward (DF) model operation mode puts more processing burden on the relay. In this paper, we not only extend their model into amplify and forward (AF) model proposed in [2],[3], but also propose an efficient decoding algorithm, which is able to order the joint channel coefficients of overall channel consisting of source-relay link and relay-destination link and cancels the previous decoded symbols at the next decoding procedure. The simulation results show that this algorithm efficiently improves its performance achieving 2-3dB gain compared to [1] in high SNR region and also useful to DF achieving more than 3dB gain compared to an original algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.8
• /
• pp.733-738
• /
• 2013

In this paper, we consider a physical layer security of an amplify-and-forward (AF) transmission in a presence of an eavesdropper in a wiretap channel. The proposed wiretap channel consists of a source, a destination, a relay, and an eavesdropper. Specifically, we consider that the relay has multiple antennas to exploit a diversity gain and a receive/transmit antenna selection schemes are applied to maximize a signal-to-noise ratio. In a practical point of view, we focus on the practical scenario where the relay does not have any channel state information of the eavesdropper while performing an AF protocol at the relay. For a secrecy performance analysis, we analyze a secrecy outage probability of the proposed system in one-integral form and verify our analysis with the computer-based simulation.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.1
• /
• pp.27-33
• /
• 2013

In this paper, we propose a pilot based channel estimation technique in two-way relay networks. We propose to transmit a pilot symbol together with the data symbol during transmission. In absence of Channel State Information (CSI), destination uses the pilot symbol to estimate the channel. In this system, the relay amplifies the pilot and the data symbol then forward them to the destination using amplify and forward (AF) protocol. We assume that the relay gain is fixed, so the relay does not need to estimate the channel, the destination only estimate the channel. We apply well-known Least-square (LS) and minimum mean-square error (MMSE) channel estimation methods to estimate the channel.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.83-84
• /
• 2006

In this paper, we introduce the AF cooperative diversity with multiple relays using phase feedback. Simulation results show that the proposed schemes obtain the diversity gain according to the number of the cooperating terminals. The performance of proposed scheme using tolerable quantized feedback is close to that of proposed scheme using full feedback.