Christos K. Datsikas

Serial Free-Space Optical Relaying Communications Over Gamma-Gamma Atmospheric Turbulence Channels

In this paper, a study on the end-to-end performance of multihop free-space optical wireless systems over turbulence-induced fading channels, modeled by the gamma-gamma distribution, is presented. Our analysis is carried out for systems employing amplify-and-forward channel-state-information-assisted or fixed-gain relays. To assess the statistical properties of the end-to-end signal-to-noise ratio for both considered systems, we derive novel closed-form expressions for the moment-generating function, the probability density function, and the cumulative distribution function of the product of rational powers of statistically independent squared gamma-gamma random variables. These statistical results are then applied to studying the outage probability and the average bit error probability of binary modulation schemes. Also, for the case of channel-state-information-assisted relays, an accurate asymptotic performance analysis at high SNR values is presented. Numerical examples compare analytical and simulation results, verifying the correctness of the proposed mathematical analysis.

Average Symbol Error Probability of General-Order Rectangular Quadrature Amplitude Modulation of Optical Wireless Communication Systems Over Atmospheric Turbulence Channels

Using an accurate exponential bound for the Gaussian Q-function, we derive simple approximate closed-form expressions for the average symbol error probability (ASEP) of a free-space optical communication link using subcarrier intensity modulation (SIM) with general-order rectangular quadrature amplitude modulation (QAM) over atmospheric turbulence channels. To model the atmospheric turbulence conditions, the log-normal and the gamma-gamma distribution are used. Extensive numerical and computer simulation results are presented in order to verify the accuracy of the proposed mathematical analysis.

Outage Analysis of Decode-and-Forward Relaying Over Nakagami-

In this letter, closed-form outage probability expressions are presented for an -relays dual-hop plus a direct link network, in which the decode-and-forward relaying protocol is employed. Our analysis significantly extends previous results on Rayleigh fading, considering a Nakagami- fading environment with either equal or distinct second hops fading parameters to average power ratios. Various numerical examples illustrate the proposed analysis.

m

In this paper, a study on the end-to-end performance of dual-hop non-regenerative relaying over independent generalized-K (KG) fading channels is presented. Using a suitable upper bound for the end-to-end signal-to-noise ratio (SNR), novel closed-form expressions for the cumulative distribution function (CDF), probability density function (PDF) and the moments of this bounded SNR are derived. These results can be afterwards used to obtain important performance metrics of the considered system such as the outage probability and the error performance of digital modulation schemes. In the case of independent but non-necessarily identical fading channels, lower bounds for the average bit error probability (ABEP) for different modulation schemes are determined by using the Pade approximants method. For the case of identical fading channels, closed-form lower bounds for the ABEP are derived. Various numerical and computer simulation results illustrate the proposed analysis.

Fading Channels

The authors study the performance of a dual-hop plus a direct link multiple-input multiple-output (MIMO) wireless communication system using orthogonal space–time block codes. The system under consideration is based on the decode-and-forward relaying protocol and operates over spatially correlated Nakagami-m fading channels. The proposed analysis is generic enough to account for any MIMO correlation model either from measurements or having theoretical and analytical justification. Analytical expressions for the system end-to-end outage and average symbol error probability are obtained, while critical parameters of the MIMO channel are taken into consideration such as the angle of arrival, the antenna array configuration, the wavelength and non-isotropic scattering conditions. Various numerical and computer simulation results demonstrate the proposed mathematical analysis and the impact of the above parameters to the system performance.

Dual-hop relaying communications over generalized-K (KG) fading channels

In this paper, a study on the end-to-end performance of multi-hop non-regenerative relaying networks over independent generalized-gamma (GG) fading channels is presented. Using an upper bound for the end-to-end signal-to-noise ratio (SNR), novel closed-form expressions for the probability density function, the moments, and the moments-generating function of the end-to-end SNR are presented. Based on these derived formulas, lower bounds for the outage and the average bit error probability (ABEP) are derived in closed form. Special attention is given to the low- and high-SNR regions having practical interest as well as to the Nakagami fading scenario. Moreover, the performance of the considered system when employing adaptive square-quadrature amplitude modulation is further analyzed in terms of the average spectral efficiency, the bit error outage, and the ABEP. Computer simulation results verify the tightness and the accuracy of the proposed bounds. Copyright

Dual-hop multi-input multi-output relay systems over spatially correlated Nakagami-m fading channels

In this paper, for an L-relays dual-hop plus a direct link wireless network, in which the decode-and-forward relaying protocol is employed, closed-form expressions for the end-end outage probability are presented. Our analysis considers a Nakagami-m fading environment with either equal or distinct second hops fading parameter to average power ratios. Various numerical examples illustrate the proposed analysis.

Serial relaying communications over generalized-gamma fading channels

In this paper, a study on the end-to-end performance of multihop non-regenerative relaying over independent and identical generalized-gamma fading channels is presented. Novel closed-form bounds for the cumulative distribution function, the moments, and the moment generating function (MGF) of the end-to-end signal-to-noise ratio are presented. Using the MGF-based approach, closed-form expressions for the amount-of-fading, the outage probability, and the average bit error probability for binary differential phase shift keying are derived. In order to validate the accuracy of the proposed mathematical analysis, various numerical and computer simulation results are presented and compared to the analytical ones.

Dual-Hop Relaying Networks over Nakagami-M Fading Channels

An infinite series representation for the moment generating function of the sum of squared arbitrarily correlated Rayleigh random variables is presented. Based on the derived formula, corresponding analytical expressions for the probability density and cumulative distribution functions are extracted. As an application for the aforementioned sum, exact analytical expressions for the outage and the average error probability, as well as, the channel average spectral efficiency of multibranch maximal-ratio diversity receivers operating over identically distributed and arbitrarily correlated Rayleigh fading channels are obtained. Our analysis is verified by comparing numerically evaluated results with extensive computer simulation ones.