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- George K. Karagiannidis, Nikos C. Sagias, P. Takis Mathiopoulos
- IEEE Trans. Communications
- 2007

A generic and novel distribution, referred to as N∗Nakagami, constructed as the product of N statistically independent, but not necessarily identically distributed, Nakagamim random variables (RVs), is introduced and analyzed. The proposed distribution turns out to be a very convenient tool for modelling cascaded Nakagami-m fading channels and analyzing the… (More)

- Petros S. Bithas, Nikos C. Sagias, P. Takis Mathiopoulos, George K. Karagiannidis, Athanasios A. Rontogiannis
- IEEE Communications Letters
- 2006

The performance of digital communication systems over Generalized-K (KG) fading channels is analyzed and evaluated. Novel closed form expressions for the SNR statistics, the average Shannon’s channel capacity and the bit error rate (BER) are derived. These expressions are used to study important performance criteria such as the outage performance, the… (More)

- Nikos C. Sagias, George K. Karagiannidis
- IEEE Transactions on Information Theory
- 2005

Ascertaining on the suitability of the Weibull distribution to model fading channels, a theoretical framework for a class of multivariate Weibull distributions, originated from Gaussian random processes, is introduced and analyzed. Novel analytical expressions for the joint probability density function (pdf), moment-generating function (mgf), and cumulative… (More)

- George K. Karagiannidis, Theodoros A. Tsiftsis, Ranjan K. Mallik
- IEEE Trans. Communications
- 2006

We present closed-form lower bounds for the performance of multihop transmissions with nonregenerative relays over not necessarily identically distributed Nakagamifading channels. The end-to-end signal-to-noise ratio is formulated and upper bounded by using an inequality between harmonic and geometric means of positive random variables (RVs). Novel… (More)

- George K. Karagiannidis, Dimitris A. Zogas, Stavros A. Kotsopoulos
- IEEE Trans. Communications
- 2003

In this letter, capitalizing on the proof of a theorem presented by Blumenson and Miller many years ago, a useful closed formula for the exponentially correlated -variate Nakagamiprobability density function is proposed. Moreover, an infinite series approach for the corresponding cumulative distribution function is presented. Bounds on the error resulting… (More)

- George K. Karagiannidis, Athanasios S. Lioumpas
- IEEE Communications Letters
- 2007

We present a novel, simple and tight approximation for the Gaussian Q-function and its integer powers. Compared to other known closed-form approximations, an accuracy improvement is achieved over the whole range of positive arguments. The results can be efficiently applied in the evaluation of the symbol error probability (SEP) of digital modulations in the… (More)

- Theodoros A. Tsiftsis, Harilaos G. Sandalidis, George K. Karagiannidis, Murat Uysal
- IEEE Trans. Wireless Communications
- 2009

Optical wireless, also known as free-space optics, has received much attention in recent years as a cost-effective, licensefree and wide-bandwidth access technique for high data rates applications. The performance of free-space optical (FSO) communication, however, severely suffers from turbulence-induced fading caused by atmospheric conditions. Multiple… (More)

- Diomidis S. Michalopoulos, George K. Karagiannidis
- IEEE Trans. Wireless Communications
- 2008

We provide closed-form expressions for the outage and bit error probability (BEP) of uncoded, threshold-based opportunistic relaying (OR) and selection cooperation (SC), at arbitrary signal to noise ratios (SNRs) and number of available relays, assuming decode-and-forward relays and Rayleigh fading channels. Numerical results demonstrate that SC performs… (More)

- George K. Karagiannidis
- IEEE Trans. Communications
- 2004

In this letter, an alternative moments-based approach for the performance analysis of an -branch predetection equal gain combiner (EGC) over independent or correlated Nakagamifading channels is presented. Exact closed-form expressions are derived for the moments of the EGC output signal-to-noise ratio (SNR), while the corresponding moment-generating… (More)

- Diomidis S. Michalopoulos, Himal A. Suraweera, George K. Karagiannidis, Robert Schober
- IEEE Trans. Communications
- 2012

Performance evaluation by considering outdated channel estimates in cooperative communications systems is formulated, with only Amplify-and-Forward (AF) relaying mode being considered in this paper. The approximation of closedform solution for the system analysis is derived. The wireless relay channels between different nodes (e.g., source to relay, relay… (More)