Semi-blind Relays Research Articles

Ergodic Capacity and SNR Analysis for Dual Hop Amplify and Forward Cooperative Communication Systems Over <inline-formula> <tex-math notation="LaTeX">$\alpha$</tex-math> </inline-formula><inline-formula> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula><inline-formula> <tex-math notation="LaTeX">$\eta$</tex-math> </inline-formula><inline-formula> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula><inline-formula> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> Channels

Dual-hop communication systems are known to extend coverage and reduce transmit power in scenarios where one-hop communication is not possible. The $\alpha -\eta -\mu$ fading distribution is a general fading distribution that can be reduced to other fading distributions like Rayleigh, Nakagami- $m$ , $\alpha$ - $\mu$ , and $\eta$ - $\mu$ . In this paper, we study the statistics of the end-to-end signal to noise ratio (SNR) of a dual-hop amplify and forward system with semi-blind relay over independent but not necessarily identical $\alpha -\eta -\mu$ fading channels. Specifically, we derive an expression for the $n$ th moment of the end-to-end SNR. The derived expression is then utilized to find the average value, the amount of fading, and the ergodic capacity of the end-to-end SNR. Numerical results are provided and compared to simulations to validate the derived expressions.

Cooperative HARQ protocols using semi-blind relays for underlay cognitive radio networks

In this paper, we evaluate the throughput of cooperative ARQ and HARQ I protocols in underlay cognitive radio networks using semi blind relays. Semi Blind Relays do not require to estimate the channel of the first hop, they use only some channel statistics. Relays help the secondary source to deliver its packet. Only relays that generate an interference to primary receiver lower than a predefined threshold will be activated. Three relay selection techniques are considered: opportunistic relaying, partial and reactive relay selection. Opportunistic relaying consists in selecting the relay that offers the highest end-to-end SNR. Partial relay selection consists in selecting the relay that offers the highest SNR of the first hop. Reactive relay selection consists in selecting the relay that offers the highest SNR of the second hop. This relay is selected among the active ones that generate an interference to primary receiver lower than a predefined threshold. To the best of our knowledge, there are no studies dealing with throughput evaluation of HARQ protocols for cognitive radio networks using opportunistic relaying, partial and reactive relay selection. Besides, this is the first paper to deal with HARQ protocols using semi blind relays. Previous studies dealt with outage, bit and symbol error probabilities evaluation for cognitive radio networks.

Performance analysis of semi-blind two-way AF relaying over generalized-k fading channels

In this paper, we present analytical expressions for the outage probability, average symbol error rate (SER), and average sum-rate of two-way dual-hop opportunistic amplify-and-forward (AF) relaying over independent and not necessarily identical generalized-k (KG) fading channels. New closed-form expression for the gain of non-regenerative semi-blind relays is derived. This expression is used to obtain the equivalent signal-to-noise ratio (SNR). Based on the above mentioned formulas, tight bounds of some performance metrics, the outage probability, average SER, and average sum-rate, are derived for the semi-blind and channel state information (CSI) relaying. In order to prove the exactness of the proposed mathematical analysis, a selection of numerical results is provided.

A comprehensive framework for performance analysis of dual-hop cooperative wireless systems with fixed-gain relays over generalized fading channels

In the present contribution, we propose a comprehensive framework for the analysis of cooperative dual-hop wireless systems over generalized fading channels, which use an amplify and forward (AF) relaying mechanism with blind and semi-blind relays. In particular, the proposed framework provides either exact results or very accurate bounds for computing the moment generating function (MGF) of the end-to-end signal-to-noise ratio (SNR) for various fading channel models typically encountered in real propagation environments. Furthermore, with the help of the MGF-based approach for performance analysis of wireless systems over fading channels, we will show that important performance indexes can be easily derived from the MGF. With respect to previous published articles on the matter, the main contribution of the paper is twofold: i) by relying on the properties of the Meijer-G function, either exact expressions or accurate bounds for the MGF of the end-to-end SNR are provided, and ii) the analysis encompasses the vast majority of fading channel models. Numerical and simulation results will be compared to substantiate the analytical derivation.

End-to-end performance of dual-hop semi-blind relaying systems with partial relay selection

The end-to-end performance of dual-hop cooperative links using semi-blind (fixed gain) relays and partial relay selection is investigated. The selection scheme considers that the source monitors the connectivity among the nodes (relays) of the first hop only. This scheme is interesting in practical ad-hoc and sensor networks. In our analysis, compact closed-form expressions are obtained for the outage probability, probability density function, moment generating functions, and generalized moments of the end-to-end signal-to-noise ratio(SNR), from which other relevant statistics that well-describe the distribution of the end-to-end SNR, such as mean, variance, kurtosis, skewness, and amount of fading, can also be deduced. Furthermore, the dynamic behavior of the end-to-end envelope is investigated, and the corresponding level crossing rate and average fade duration are obtained in an exact manner. Also, tight lower and upper bounds for these second-order statistics are presented in closed-form. Numerical results illustrating the system's performance in terms of the above metrics are provided, and the influence of the relay selection on performance is analyzed and discussed. For instance, it is shown that the power imbalance between the hops may have positive or negative effects on the overall system performance irrespective of the number of selected relays.

Cooperative dual-hop relaying systems with beamforming over nakagami-m fading channels

In this paper, we investigate the end-to-end performance of dual-hop relaying systems with beamforming over Nakagami-m fading channels. Our analysis considers semiblind (fixed-gain) relays with single antennas, and source and destination nodes equipped with multiple antennas. Closed-form expressions for the outage probability (OP), moment generating function (MGF), and generalized moments of the end-to-end signal-to-noise ratio (SNR) are derived. The proposed expressions apply to general operating scenarios with distinct Nakagamim fading parameters and average SNRs between the hops. The influence of the power imbalance, fading parameters, and antenna configurations on the overall system performance are analyzed and discussed through representative numerical examples. Furthermore, the exactness of our formulations is validated by means of Monte Carlo simulations.

Dual-hop transmissions with semi-blind relays over Nakagami- m fading channels

The performance of dual-hop wireless communication systems with semi-blind relays over Nakagami-m fading channels is investigated. The analysis is based on the evaluation of the average end-to-end signal-to-noise ratio. Some numerical plots show that the power imbalance between the hops may have both positive or negative effects on the overall system performance.

Performance bounds of multihop wireless communications with blind relays over generalized fading channels

In this letter, efficient performance bounds for multihop wireless communications systems with non-regenerative blind relays over non-identical Nakagami-n (Rice), Nakagami-m and Nakagami-q (Hoyt) generalized fading channels, are presented. More specifically, the end-to-end signal-to-noise ratio (SNR) is formulated and upper bounded by using the well-known inequality between harmonic and geometric mean of positive random variables. This bound is used to study important system's performance metrics: i) the moments of the end-to-end SNR which are obtained in closed-forms, and ii) the outage probability and the average error probability for coherent and non-coherent modulations, which are accurately approximated using the moments-based approach. Furthermore, new analytical formulae are derived for the gain of previously proposed semi-blind relays in generalized fading environments. These kind of relays are used in numerical examples and computer simulations to verify the accuracy and to show the tightness of the proposed bounds.