Aleksandra M. Cvetkovic

Partial Relay Selection With Outdated Channel State Estimation in Mixed RF/FSO Systems

We study a dual-hop relaying system, composed of mixed radio frequency (RF)/free-space optical (FSO) links. Partial amplify-and-forward relay selection is assumed, which is based on outdated channel state information (CSI). The RF link is subject to Rayleigh fading, while the FSO link is affected by atmospheric turbulence, modeled by Gamma-Gamma distribution. Novel analytical expressions for the outage probability and average bit error rate (BER) are derived. Numerical results are presented and validated by Monte-Carlo simulations. The outage probability and average BER dependence on turbulence strength, average signalto-noise ratio (SNR) over RF hop, average electrical SNR over FSO hop, number of relays, and rank of selected relay, are also investigated, while the effect of time correlation between current source-relay channel and its outdated CSI, is considered. The results illustrate that the outdated CSI used for the relay selection has a strong effect on the system performance, especially in weak turbulence conditions of the FSO hop. Furthermore, the improvement of the system performance with increase of the number of the relays is highly dependent on the FSO channel state.

Mixed RF/FSO Relaying With Outdated Channel State Information

We investigate the outage probability and the average bit error rate (BER) performance of a dual-hop amplify-and-forward (AF) relaying system, composed of a mixed radio frequency (RF)/free-space optical (FSO) link, when simultaneously outdated channel state information (CSI) is assumed at the relay and there is a misalignment between transmitter and receiver apertures in FSO link. In contrast to the majority of works on CSI-assisted AF relays, in this paper, we assume that the estimated CSI is outdated, when the relay amplifies the transmitted signal. The RF link experiences Rayleigh fading, while the FSO link is under the influence of atmospheric turbulence, modeled by the Gamma-Gamma distribution. Novel analytical expressions for the outage probability and the average BER are derived in a power series form, which in some special cases are simplified to offer engineering insight into the effects of important transceiver and channel parameters on the system performance. Numerical and simulation results show that there is an optimal value of the transmitter beam waist, which minimizes the overall outage probability. This optimal value strongly depends on the pointing errors standard deviation. Furthermore, the outage probability varies for several orders of magnitude depending on the transmitter beam waist.

Performance analysis of dual switched diversity over correlated Weibull fading channels with co-channel interference

This paper studies the performance of switch and stay combining (SSC) diversity in the presence of co-channel interference over correlated Weibull fading channels. SSC diversity based on signal-to-interference ratio (SIR) is a low-complexity and a very efficient technique that reduces fading and co-channel interference influence. New closed-form expressions for the probability density function and cumulative distribution function of the output SIRs are derived. These formulas are used in a detailed analysis of the average output SIR and outage probability. The influence of fading severity and correlation coefficient on the optimum switching threshold and system performance is investigated. Monte Carlo simulations are performed to verify obtained theoretical results and determine average bit error rate in detecting binary phase-shift keying (BPSK), differential BPSK and quadrature amplitude modulation signals. Copyright

PERFORMANCE OF DUAL-HOP RELAYING OVER SHADOWED RICEAN FADING CHANNELS

Performance of Dual-Hop Relaying Over Shadowed Ricean Fading Channels In this paper, an analytical approach for evaluating performance of dual-hop cooperative link over shadowed Ricean fading channels is presented. New lower bound expressions for the probability density function (PDF), cumulative distribution function (CDF) and average bit error probability (ABEP) for system with channel state information (CSI) relay are derived. Some numerical results are presented to show behavior of performance gain for the proposed system. Analytical exact and lower bound expression for the outage probability (OP) of CSI assisted relay are obtained and required numerical results are compared.

Outage analysis for uncoordinated decode-and-forward networks over nakagami-m channels

In this paper, the outage performance of decode-and-forward (DF) cooperative networks over Nakagami-m fading channels is investigated. In the case of the integer values of the fading severity parameter, the novel closed-form analytical expression for outage probability of networks where destination performs maximum ratio combining (MRC) is derived. Impacts of number of networks nodes, signal-to-noise ratio and fading severity are analyzed.

ABER performance of dual-hop system over asymmetric fading channels with interference at the relay

This paper studies the performance of a dual-hop amplify-and-forward (AF) system where the source-relay and relay-destination channels experience Rayleigh and Rician fading, respectively. The relay node is corrupted by Rayleigh faded multiple co-channel interferences. Based on proposed system model, new closed-form expression for the average bit error rate (ABER), in the case of several modulation formats, is derived. Numerical results are performed in order to verify analytical approach.

Mixed RF/FSO Relaying Systems

In this chapter, we are focused on wireless optical communications utilizing in overcoming a connectivity gap between the backbone and last mile access networks. The outage performance of dual-hop amplify-and-forward (AF) relaying systems, composed of mixed radio frequency (RF)/free-space optical (FSO) links is presented, when the partial relay selection is considered based on outdated channel state information (CSI). We analyze an example when the RF link is subjected to Rayleigh fading, while the FSO link is affected by atmospheric turbulence, which results in the intensity fluctuations of the optical signal, following the Gamma–Gamma distribution with taking the pointing errors into account. Analytical expressions for the outage probability are presented. The effects of atmospheric turbulence strength, pointing errors standard deviation, number of relays and rank of selected relay, are observed, considering the effect of time correlation between current and outdated CSI of the source-relay channel.

Outage probability of decode-and-forward network with threshold based protocol over Rayleigh fading

In this paper, the outage performance for decode-and-forward cooperative networks is investigated. The analytical results for outage probability are derived in the case when network nodes communicate with each other over Rayleigh fading channel using a threshold based protocol, while Rayleigh propagation also is experienced over a channel between a node and the destination. Impact of signal-to-noise ratio values and number of nodes when maximum ratio combining is applied at the destination are analysed.

Outage Performance of Dual-Hop AF Relay Channels with Co-Channel Interferences over Rayleigh Fading

This paper studies the outage performance of a dual-hop amplify-and-forward (AF) relay fading channel in an interference-limited environment. The relay and destination nodes are corrupted by multiple co-channel Rayleigh interferences. New exact closed-form expressions for the outage probability for channel-state-information (CSI)—assisted relay, in which gain is dependent on previous hop CSI and interference, are derived. Monte Carlo simulations are performed to verify the obtained theoretical results. For the cases where the number of interferers at the relay and the destination node is equal, we derive novel expressions for outage probability upper and lower bounds.

Performance analysis of energy harvesting DF relay system in generalized-K fading environment

Abstract The performance of decode-and-forward (DF) relaying systems is analyzed for the energy constrained relay and Generalized-K fading environment, assuming that the communication in both links of relaying system is corrupted by effects of multipath fading and shadowing. We analyze the ergodic and outage capacities for two representative cases: in one case energy harvesting and information transmission are arranged based on time-switching relaying protocol, while in the other analyzed case they are arranged based on power-splitting relaying protocol. The novel analytical closed-form results for error performance of DF energy harvesting system are applicable for wide range of modulation formats. The derived closed-form capacity and error rate expressions are valid for both relaying protocols and various scenarios of composite fading environment. Analytical results are corroborated by an independent simulation method. Finally, the impact of the system and channel parameters on the system performance is demonstrated through numerical analysis.