Kyu Sung Hwang

Performance analysis of incremental opportunistic relaying over identically and non-identically distributed cooperative paths

In this paper, we consider an incremental relaying protocol based on an amplify-and-forward transmission in conjunction with the best relay selection scheme over non-identically distributed relay channels. In order to satisfy the spectral efficiency and the bit error rate (BER) requirements, adaptive modulation is applied to our proposed scheme. We derive the average spectral efficiency, average BER and outage probability for the performance analysis of our proposed scheme. For a more tractable analysis, we start with an upper bound for the combined signal-to-noise ratio at the destination and provide closed-form expressions for independent non-identically distributed Rayleigh fading conditions. Our analytical-based numerical results are validated by some computer-based simulations. These results show that our proposed scheme leads to a considerable improvement in the performance of cooperative diversity systems.

Performance Bounds for Two-Way Amplify-and-Forward Relaying Based on Relay Path Selection

In this paper, we consider two-way amplify-and- forward relaying communication over a multiple relays network in which the best relay node is selected among others. Our proposed scheme picks for duplex communication between the source and the destination only the relay which provides the best end-to-end performance based on the instantaneous channel information. Similar to the relay selection method proposed in (1), our scheme also does not require any explicit communications among the relays. Based on the proposed relay selection criterion, we offer the performance bounds on the average sum-rate, average symbol error rate, outage probability over identically, independent distributed Rayleigh fading channels. Further, our numerical examples show that our proposed scheme provides considerable sum-rate gains and offers an increasing a diversity order as the number of relay candidates increases. Index Terms—Two-way relaying, half-duplex transmission, amplify-and-forward relaying, opportunistic relaying, and per- formance bounds.

Outage probability of cooperative diversity systems with opportunistic relaying based on decode-and-forward

Opportunistic relaying with cooperative diversity has been introduced in as a simple alternative protocol to the distributed space-time coded protocol while achieving the same diversity-multiplexing tradeoff performance as a point-to-point multiple-input multiple-output scheme. In this paper, we derive the upper and lower bounds for the cumulative distribution function of the signal-to-noise ratio per hop, and then provide their probability density function and moment generating function.We also derive approximate but tight closed-form expressions for the lower and upper bounds of the outage probability of opportunistic relaying based on decode-and-forward transmission under the assumption of unbalanced/balanced hops and independent, identically distributed Rayleigh fading channels.

An Efficient Relay Selection Algorithm for Cooperative Networks

Recently, the cooperative diversity systems, based on the distributed space-time coding (DSTC), have been presented to provide the spatial diversity gain in the wireless networks. Although the performance of DSTC cooperative diversity systems is quite attractive in terms of the link performance, the complexity and the power consumption at each node are the main practical issues for the deployment of the systems, in particular, when the number of nodes is large. In this paper, we propose the suboptimal relay selection algorithm where a predetermined threshold is set both at the relay node and the destination node, and the node selection is performed only when the signal quality of either relay node or destination node is below a predetermined threshold, which has less complexity than the opportunistic relaying in while satisfying the required performance. We provide the closed-form expression of statistics of the output SNR and study the complexity of the proposed scheme. Based on our analytical results we show several selected numerical examples to show the efficiency of our proposed schemes.

Performance Analysis of Two-Way Amplify and Forward Relaying with Adaptive Modulation over Multiple Relay Network

In this letter, we propose two-way amplify-and-forward relaying in conjunction with adaptive modulation in order to improve spectral efficiency of relayed communication systems while monitoring the required error performance. We also consider a multiple relay network where only the best relay node is utilized so that the diversity order increases while maintaining a low complexity of implementation as the number of relays increases. Based on the best relay selection criterion, we offer an upper bound on the signal-to-noise ratio to keep the performance analysis tractable. Our numerical examples show that the proposed system offers a considerable gain in spectral efficiency while satisfying the error rate requirements.

Performance analysis of incremental relaying with relay selection and adaptive modulation over non-identically distributed cooperative paths

In this paper, we consider an incremental relaying protocol based on an amplify-and-forward transmission in conjunction with a best relay selection scheme over non-identically distributed relay channels. In order to satisfy the spectral efficiency and the bit error rate (BER) requirements, adaptive modulation is applied to our proposed scheme. We derive the average spectral efficiency, average BER and outage probability for the performance analysis of our proposed scheme. For a more tractable analysis, we start with an upper bound for the combined signal-to-noise ratio at the destination and provide closed-form expressions for independent non-identically distributed Rayleigh fading conditions. Our analytical-based numerical results are validated by some computer-based simulations. These results show that our proposed scheme leads to a considerable improvement in the performance of cooperative diversity systems.

Performance analysis of opportunistic incremental relaying with adaptive modulation over cooperative networks

Opportunistic relaying and incremental relaying over cooperative network were introduced as efficient relaying protocols to increase the system capacity and performance. In this paper, we propose an opportunistic incremental relaying scheme in conjunction with adaptive modulation, and provide its performance analysis in terms of average spectral efficiency, average bit error rate, and outage probability. For more tractable analysis, we start with an upper bound for the combined signal-to-noise ratio at the destination and derive closed-form expressions for Rayleigh fading conditions. Our analytical-based numerical results are validated by some selected computer-based simulations.

Performance Analysis of Incremental Relaying Transmission with Adaptive QAM over Nakagami-m Fading Channels

Cooperative network is a way to make a reliable communication by adding a relay between the source and the destination. The incremental relaying based on the amplify-and-forward transmission was introduced in (Laneman et al., 2004) as an efficient relaying protocol. In this paper, we provide the performance analysis of incremental relaying with adaptive QAM transmission over the independent, non-identically distributed Nakagami-m fading channels. By using an upper bound on the output signal-to-noise ratio, the average spectral efficiency, average bit error rate and outage probability of our proposed system are derived. Our analytical-based numerical results are validated by some computer-based simulations.

Low Complexity Cooperative Communication with Switched Relay Selection and Adaptive Modulation

In this paper, we propose a low complexity coop- erative communication systems with the amplify-and-forward protocol over a multiple distributed relay network where only one relay among relay candidates is selected according to a certain threshold. By setting different values of their threshold, we consider two different relay selection schemes: (i) achieving the maximum spectral efficiency and (ii) minimizing system complexity. From our provided statistics of the combined output signal-to-noise ratio and our analysis of the system complexity, we show that our proposed node selection schemes provide considerable spectral efficiency gain and outage performance while it has a relatively low complexity comparing to other schemes known in the literatures. Index Terms—Cooperative diversity, relay selection, amplify- and-forward and adaptive modulation.

Performance analysis of two-way amplify and forward relaying with adaptive modulation

In this paper, we study two-way amplify-and-forward relaying in conjunction with adaptive modulation over a multiple relay network. In order to keep the diversity order equal to the number of relays and maintain a low complexity, we consider the best relay selection scheme in this work. Based on the proposed selection criterion for the best relay, we analyze the average spectral efficiency by its approximated upper bound. In addition, we extend the proposed scheme to the case where a direct path between source and destination exists. Our numerical examples show that the proposed system offers a considerable gain in the spectral efficiency while satisfying the error rates requirements.