Decode-and-forward Cooperative Networks Research Articles

User selection protocol in DF cooperative networks with hybrid TSR-PSR protocol based full-duplex energy harvesting over rayleigh fading channel: system performance analysis

Cooperative communication has been recently proposed in wireless communication systems for exploring the inherent spatial diversity in relay channels. In this work, we investigate the system performance of the energy harvesting full-duplex (FD) decode-and-forward (DF) hybrid TSR-PSR (TPSR) protocol relaying network. In the selection scheme, the best user selection protocol is proposed and investigated. Mainly we derive the closed-form expression for the outage probability, system throughput and the symbol error rate (SER) of the system. Numerical results are also presented by the Monte Carlo simulation to validate the theoretical analysis in connection with the all possible parameters in the comparison between TSPR, TSR and PSR cases. The research results show that TPSR case is better than the others in term of outage probability and SER.

User selection protocol in DF cooperative networks with hybrid TSR-PSR protocol based full-duplex energy harvesting over rayleigh fading channel: system performance analysis

<span>Cooperative communication has been recently proposed in wireless communication systems for exploring the inherent spatial diversity in relay channels. In this work, we investigate the system performance of the energy harvesting full-duplex (FD) decode-and-forward (DF) hybrid time switching-power splitting relaying TSR-PSR (TPSR) protocol relaying network. In the selection scheme, the best user selection protocol is proposed and investigated. Mainly we derive the closed-form expression for the outage probability, system throughput and the symbol error rate (SER) of the system. Numerical results are also presented by the Monte Carlo simulation to validate the theoretical analysis in connection with the all possible parameters in the comparison between TSPR, TSR and PSR cases. The research results show that TPSR case is better than the others in term of outage probability and SER.</span>

Joint Relay Selection and Power Allocation for Full-Duplex DF Co-Operative Networks With Outdated CSI

We investigate joint relay selection (RS) and power allocation (PA) for full-duplex (FD) decode-and-forward (DF) co-operative networks, considering the scenario where the available channel state information (CSI) is outdated, yet the correlation coefficient between the outdated CSI and the real one is known. We show that in the outdated CSI environment, the proposed scheme can provide a performance improvement over the conventional schemes, and if the residual loop interference (RLI) is sufficiently low, more performance gains can be offered in the high signal-to-noise-ratio (SNR) region. Simulations are provided to validate our results.

A Fair Relay Selection Based on Mapping Functions in the Dual Hop DF Cooperative Networks

We address the load balance, referred as “fairness” in our work, in the relay selection procedure of the dual hop decode-and-forward (DF) cooperative networks. Firstly, the unfairness caused by the known best-path relay selection (BRS) scheme is analyzed by the metric of blocking probability at the relays with equal relay channels. Secondly, aiming to improve the fairness while keeping a satisfied and comparable outage performance, we propose a fair relay selection algorithm based on mapping functions, including the signal to noise ratio (SNR) mapping functions and load mapping functions. It is worth mentioning that BRS scheme can be viewed as a special case of the proposed algorithm. Afterwards, the outage probability of the proposed algorithm is derived. During the derivation, the mixture Gamma distribution is used to model SNRs of wireless fading channels, so this kind of derivation is valid for different fading channels, e.g. Rayleigh, Nakagami-m etc.. Finally, taking the average load and outage probability as performance metrics, we simulated the proposed algorithm and compared it with the proportional fair cooperation (PFC) algorithm in the literature. As observed in the simulation results, the proposed algorithm guarantees fairness well among the relays, especially when the network is heavily burdened

Relay selection for DF-based cooperative vehicular systems

In this paper, error performance analysis of decode-and-forward (DF)-based cooperative vehicular networks with relay selection is investigated. All of the links in the system are modeled as cascaded Nakagami-m distributed random variables which provide a realistic description of an intervehicular channel. We employ virtual-noise (VN)-based demodulation, maximum likelihood (ML) demodulation, cooperative maximal ratio combining (C-MRC), and log-likelihood-ratio-based transmissions in mitigating error propagation effect encountered in DF cooperative networks. In order to obtain more effective solutions and improve the system performance, we introduce hybrid anti-error propagation approaches, namely VN-MRC, VN-ML, and VN-LLR in which relay selection criterion is derived by using conditional bit error rate (BER) expressions of VN technique while data detection is performed by utilizing maximal ratio combining (MRC), ML detection, C-MRC and LLR transmission methods. The performance analyses and the numerical results for cascaded Nakagami-m channels have shown that VN-LLR approach provides significant performance improvement with respect to the other considered techniques in DF cooperative vehicular systems with relay selection.

Estimation of synchronization impairments in multi-relay DF cooperative networks

Cooperative communication systems can effectively increase channel capacity and combat fading. Effective cooperation requires synchronization impairments such as multiple timing offsets and multiple carrier frequency offsets to be accurately estimated and mitigated. This paper seeks to address the joint estimation of synchronization impairments in multi-relay decode-and-forward (DF) cooperative networks. Firstly, a simple yet effective estimation method based on the devised training signals is presented for achieving synchronization. Then, an iterative algorithm is further derived in order to improve the performance associated with the estimation of synchronization impairments. Our proposed algorithm converts the difficult multiple parameter estimation problem into more tractable sub-problems of estimating many individual impairments pairs for the independent relays. Simulations indicate that, the proposed estimator can asymptotically achieve the mean square error (MSE) for the perfectly timing or frequency synchronized case.

A Unified Matching Framework for Multi-Flow Decode-and-Forward Cooperative Networks

Recent works have shown that cooperative diversity can be achieved by using relay selection (RS), distributed space-time coding (DSTC), and distributed beam-forming (DBF) in narrow-band decode-and-forward (DF) cooperative networks with one source-and-destination (s-d) pair. However, the joint resource allocation for broadband DF cooperative networks with multiple s-d flows has not received much attention yet. In this paper, a random hypergraph based unified matching framework is proposed, under which five feasible types of multi-flow DF cooperative networks will be considered. In each type, the maximum matching method will be applied to RS, DSTC, and DBF schemes so as to achieve the optimal channel allocation and relay selection with fairness assurance. By analyzing the properties of maximum matching, the outage probability of each s-d pair after resource allocation will be obtained. The results of diversity-multiplexing tradeoff will show that the proposed framework is capable of achieving the full frequency diversity and cooperative diversity for each s-d pair simultaneously, while the frequency multiplexing is equally shared. Based on the unified framework, the random rotation based parallel Hopcroft-Karp (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> PHK) algorithm will then be designed, which can work in each destination node independently, and shall enjoy a poly-logarithmic complexity O(log <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2l</sup> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> N), where N is the number of channels and l <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> is a constant.

Fast method for precoding and decoding of distributive multi-input multi-output channels in relay-based decode-and-forward cooperative wireless networks

It is well-known that the performance of the relay-based decode-and-forward (DF) cooperative networks outperforms the performance of the amplify-and-forward cooperative networks. However, this performance improvement is accomplished at the expense of adding more signal processing complexity (precoding/decoding) at each relay node. In this study, the authors tackle this signal processing complexity issue by proposing a Jacket-based fast method for reducing the precoding/decoding complexity in terms of time computation. Jacket transforms have shown to find applications in signal processing and coding theory. Jacket transforms are defined to be n×n matrices A=(ajk) over a field ℱ with the property AA†=nIn, where A† is the transpose matrix of the element-wise inverse of A, that is, A†=(akj−1), which generalise Hadamard transforms and centre weighted Hadamard transforms. In particular, exploiting the Jacket transform properties, the authors propose a new eigenvalue decomposition (EVD) method with application in precoding and decoding of distributive multi-input multi-output channels in relay-based DF cooperative wireless networks in which the transmission is based on using single-symbol decodable space-time block codes. The authors show that the proposed Jacket-based method of EVD has significant reduction in its computational time as compared to the conventional-based EVD method. Performance in terms of computational time reduction is evaluated quantitatively through mathematical analysis and numerical results.