• ETRI Journal
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• v.32 no.1
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• pp.139-141
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• 2010

In this letter, closed-form approximations for outage probability and symbol error rate are presented for a selective decode-and-forward relay network with partial channel information. An independent but not identically distributed Rayleigh fading environment is considered. Numerical and simulated results demonstrate the validity of the analytical results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.426-435
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• 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 Internet Computing and Services
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• v.12 no.6
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• pp.35-42
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• 2011

Cooperative relay communication for wireless networks has been extensively studied due to its ability to mitigate fading effectively via spatial diversity. In this paper, we propose a balanced transmit scheme in cooperative relay communication with decode-and-forward DF) scheme. The proposed scheme selects the feedback bits to obtain the maximum cooperative diversity gain. The simulation results show that the proposed scheme improves the bit error rate BER) performance as compare with a conventional scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5347-5360
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• 2016

In decode and forward relay systems, choosing the duplex mode is an important factor to the performance. To satisfy the performance requirement, self-interference must be mitigated for the full-duplex relay (FDR), and the resource efficiency must be increased for the half-duplex ratio (HDR). Therefore, if a wise scheme to consider these two factors exists, decode and forward relay systems are used more effectively. This study proposes a new duplex selection scheme for decode and forward relay systems. The proposed duplex selection scheme chooses the better duplex mode according to the channel statistical conditions with optimal power allocation. The simulation results show that the proposed duplex scheme with optimal power allocation has lower outage probability than the FDR and the HDR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1A
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• pp.36-43
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• 2008

In this paper, we propose an optimal relay selection scheme for decode-and-forward relaying systems. The optimal relay selection minimizes the number of time slots used to relay source's signal and maximizes an end-to-end signal-to-noise ratio. However, decode-and-forward relaying systems require additional overhead for the optimal relay selection. Assuming independent and identically distributed Rayleigh fading channels, we provide exact and closed-form expressions for the outage probability of capacity and the bit error rate for decode-and-forward relaying systems with the optimal relay selection. It is shown that the analytic results are perfectly matched with the simulated ones. When the numbers of relay nodes are 2, 4, and 8, and the numbers of time slots for overhead are 1, 2, and 4, respectively, the proposed system achieves 1 dB, 2 dB, and 3 dB gains at 1% bit error rate, respectively, and 0.5 dB, 4 dB, and 12 dB gains at 1% outage probability for 1 bps/Hz, respectively, over the conventional decode-and-forward relaying system.

• Journal of Communications and Networks
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• v.16 no.5
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• pp.502-511
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• 2014

In this paper, we evaluate performance of a hybrid decode-amplify-forward relaying protocol in underlay cognitive radio. In the proposed protocol, a secondary relay which is chosen by partial relay selection method helps a transmission between a secondary source and a secondary destination. In particular, if the chosen relay decodes the secondary source's signal successfully, it will forward the decoded signal to the secondary destination. Otherwise, it will amplify the signal received from the secondary source and will forward the amplified signal to the secondary destination. We evaluate the performance of our scheme via theory and simulation. Results show that the proposed protocol outperforms the amplify-and-forward and decode-and-forward protocols in terms of outage probability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.436-442
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• 2013

The diversity-multiplexing tradeoff (DMT) function of a special half-duplex (HD) dynamic decode and forward (DDF) relay protocol with more than two antennas at the source node, two antennas at the relay node, and two antennas at the destination node is derived. This protocol is compared to a HD NAF protocol with the same number of source antennas and a HD DDF relay protocol with two antennas at the source node, more than two antennas at the relay node, and two antennas at the destination node.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9A
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• pp.776-783
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• 2011

In this paper, assuming that the transmitter can exploit imperfect channel state information (CSI), the diversity-multiplexing tradeoff (DMT) functions of three adaptive decode-and-forward (DF) relay protocols, each of which uses multiple-antennas at the destination node, at the relay node, or at the source node are derived. When the imperfect CSI qualities for the source-relay link, the relay-destination link, and the source-destination link are subject to asymptotic conditions, the additional diversity gains attainable by exploiting the imperfect CSI at the transmitter for those three adaptive DF relay protocols are investigated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.81-108
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• 2018

In this paper, we derive the theoretical Symbol Error Probability (SEP) of cooperative systems with best relay selection for Nakagami-m fading channels. For Amplify and Forward (AF) relaying, the selected relay offers the best instantaneous Signal to Noise Ratio (SNR) of the relaying link (source-relay-destination). In cooperative networks using Decode and Forward (DF), the selected relay offers the best instantaneous SNR of the link between the relay and the destination among the relays that have correctly decoded the transmitted information by the source. In the second part of the paper, we derive the SEP when all participating AF and DF relaying is performed. In the last part of the paper, we extend our results to cognitive radio networks where there is interference constraints : only relays that generate interference to primary receiver lower than a predefined threshold T can transmit. Both AF and DF relaying with and without relay selection are considered.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.31-37
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• 2009

In the two-way relay channel, the relay employ Amplify-and-Forward (AF) or Decode-and-Forward (DF) protocol, and broadcast the network-coded signal to both user. In the system, DF protocol provides maximum throughput at low signal to noise ratio(SNR). On the other hand, at high SNR, AF protocol provides maximum throughput. The paper propose active transmission scheme which employ Amplify-and-Forward or Decode-and-Forward protocol based on received SNR at the relay over Two-way relay channel. The optimal threshold is investigated numerically for switching the protocol. Through numerical results, we confirm that the proposed scheme outperforms conventional schemes over two-way relay channel.