Petros Bithas - Academia.edu (original) (raw)

Papers by Petros Bithas

IET Networks, 2013

In many situations the performance of wireless communication systems decreases especially when th... more In many situations the performance of wireless communication systems decreases especially when they operate over multipath fading channels subject also to shadowing. In this sense, cluster-based networks have been introduced as an efficient solution, offering coverage extension and energy savings. In this paper, we investigate new clusterhead (CH) selection algorithms, where the nodes can select different CHs, according to the corresponding signal strength. Additionally, it is shown that if CHs are equipped with multiple antennas, the negative consequences of the fading/shadowing can be further reduced. The performance of this scheme is theoretically investigated over correlated Nakagami-m fading channels, which are also subject to shadow fading, modelled by the Gamma distribution. The derived statistical metrics are used to obtain numerical evaluated results for the outage and the average bit error probabilities. These results are complemented by computer simulated ones, which validate the accuracy of the proposed analysis.

2014 IEEE 19th International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), 2014

ABSTRACT In wireless networks, the transmission medium poses several challenges in preserving the... more ABSTRACT In wireless networks, the transmission medium poses several challenges in preserving the Quality-of-Service due to its random nature especially in operational environments with mobility and absence of line-of-sight links between the receiver and the transmitter. On the other hand, confronting the effects of fading channels requires the employment of complex but necessary mechanisms, such as channel equalization and diversity reception and/or transmission, which utilize hardware and channel resources. A common practice, which compromises between resources consumption and performance improvement, is to employ adaptive diversity mechanisms, such as the selection diversity (SD), which represents an attractive solution in various wireless communication scenarios, since it offers relatively low complexity and improved performance. In many practical situations, though, the continuous monitoring of all the available diversity paths, which is mandatory in SD schemes, leads to unnecessary resources consumption (e.g., control channels). In order to alleviate this complexity, we adopt a new adaptive threshold based SD (t-SD) receiver, where only the current diversity path is used for signal reception as long as its signal-to-noise ratio is above a predefined threshold, otherwise the receiver becomes a pure SD. To this aim a new analytical performance evaluation framework is presented in terms of important statistical metrics, along with a complexity analysis. Numerical evaluated results illustrate how the proposed scheme outperforms other well known schemes in terms of performance and complexity trade-off.

In this paper the Shannon capacity of generalizedgamma (GG) fading channels is studied, under dif... more In this paper the Shannon capacity of generalizedgamma (GG) fading channels is studied, under different adaptive transmission techniques. The GG is a generic distribution, which is considered to be appropriate for modeling fading/shadowing phenomena. Hence, assuming single (i.e., no diversity), as well as, dual-branch selection diversity receivers, novel expressions for the capacity under three adaptive transmission policies, namely optimal power and rate adaptation (OPRA), channel inversion with fixed rate (CIFR) and truncated CIFR (TIFR), are obtained. The derived expressions are in closed form and generalize previously presented results. The proposed analysis is accompanied by numerical results, clearly demonstrating the usefulness of the theoretical approach.

IEEE Transactions on Communications, 2011

In this paper we study the statistics of the sum of not necessarily identically distributed kappa... more In this paper we study the statistics of the sum of not necessarily identically distributed kappa, that is, , random variables (RV)s. Assuming half-integer values for the shaping parameters, novel closed-form expressions for the probability density function (PDF) of the sum of independent RVs are obtained, while for arbitrary values of the shaping parameters, a corresponding PDF expression is derived in terms of fast converging infinite series. Furthermore, an infinite series representation for the PDF of the sum of two arbitrarily correlated RVs is derived. The proposed analysis is employed to the performance analysis of equal-gain combining (EGC) receivers operating over composite fading/shadowing channels modeled by the distribution. More specifically, the outage and the average bit error probabilities, as well as the average channel capacity of EGC receivers operating over such composite environment are studied. Considering different channel fading/shadowing conditions and correlation effects, various numerical performance evaluation results are presented. These results are complemented by equivalent computer simulated ones that validate the accuracy of the proposed analysis.

IEEE Transactions on Wireless Communications, 2007

A detailed performance analysis for the most important diversity receivers operating over a compo... more A detailed performance analysis for the most important diversity receivers operating over a composite fading channel modeled by the Generalized-K (KG) distribution is presented. The KG distribution has been recently considered as a generic and versatile distribution for the accurate modeling of a great variety of short term fading in conjunction with long term fading (shadowing) channel conditions. For this relatively new composite fading model, expressions for important statistical metrics of maximal ratio combining (MRC), equal gain combining (EGC), selection combining (SC) and switch and stay combining (SSC) diversity receivers are derived. Using these expressions and by considering independent but not necessarily identical distributed fading channel conditions, performance criteria, such as average output signal-to-noise ratio, amount of fading and outage probability are obtained in closed form. Moreover, following the moments generating function (MGF) based approach for MRC and SSC receivers, and the Padé approximants method for SC and EGC receivers, the average bit error probability is studied. The proposed mathematical analysis is complemented by various performance evaluation results which demonstrate the accuracy of the theoretical approach.

IEEE Transactions on Vehicular Technology, 2009

The capacity of correlated generalized Gamma (GG) fading channels with dual-branch selection dive... more The capacity of correlated generalized Gamma (GG) fading channels with dual-branch selection diversity (SD) reception and channel side information (CSI) available at both the transmitter and the receiver is studied and analyzed. In particular, the capacity is evaluated under four adaptive transmission policies defined according to the operational CSI: 1) optimal power and rate adaptation (OPRA); 2) constant power with optimal rate adaptation (ORA); 3) channel inversion with fixed rate (CIFR); and 4) truncated CIFR (TIFR). Under these four adaptation policies, fast converging infinite series expressions for the capacity are derived and evaluated. Furthermore, for the simplifying cases of independent GG fading channels and/or single-channel reception (i.e., no diversity), closed-form expressions have been obtained. Previously published expressions are shown to be special cases of the derived expressions. Performance evaluation results obtained by means of numerical analysis clearly demonstrate the usefulness and accuracy of the analysis.

Journal of Communications and Networks, 2007

The performance of dual diversity receivers operating over correlated Ricean fading channels is a... more The performance of dual diversity receivers operating over correlated Ricean fading channels is analyzed. Using a previously derived rapidly converging infinite series representation for the bivariate Ricean probability density function, analytical expressions for the statistics of dual-branch selection combining, maximal-ratio combining, and equal-gain combining output signal-to-noise ratio (SNR) are derived. These expressions are employed to obtain novel analytical formulae for the average output SNR, amount of fading, average bit error probability, and outage probability. The proposed mathematical analysis is used to study various novel performance evaluation results with parameters of interest the fading severity, average input SNRs, and the correlation coefficient. The series convergence rate is also examined verifying the fast convergence of the analytical expressions. The accuracy of most of the theoretical performance evaluation results are validated by means of computer simulations.

IEEE Communications Letters, 2006

The performance of digital communication systems over generalized-K (KG) fading channels is analy... more 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 average capacity and the BER for a great variety of modulation formats in KG fading channels. The proposed mathematical analysis is accompanied with various performance evaluation results, which demonstrate the usefulness of the proposed approach.

Iet Communications, 2008

The performance of dual-branch equal-gain combining (EGC) and maximal-ratio combining receivers o... more The performance of dual-branch equal-gain combining (EGC) and maximal-ratio combining receivers operating over a composite correlated fading environment, modelled by the generalised Gamma (GG) distribution, is analysed. The moments of the output signal-to-noise ratio are derived in closed form for both types of receivers, and by employing the Padé approximants method, the average bit error probability is studied for a great variety of modulation schemes. Furthermore, based on the statistic of the product of two correlated GG random variables, a tight union upper bound for the outage probability of the EGC is obtained, whereas for the special case of Weibull fading a simpler bound is derived in closed form. The proposed mathematical analysis is complemented by various, numericaly evaluated performance results, whereas simulations verify the correctness of the proposed analysis.

In this paper a performance analysis of triple-branch maximal ratio combining (MRC) diversity rec... more In this paper a performance analysis of triple-branch maximal ratio combining (MRC) diversity receivers operating over an arbitrarily correlated Weibull fading environment is presented. For the trivariate Weibull distribution infinite series representations for the joint probability density function (PDF) and the cumulative distribution function (CDF) are derived. Moreover, a novel analytical expression for the joint moment-generating function (MGF) is presented. It is assumed that the arbitrarily correlated variates do not necessarily have identical fading parameters and average powers. These series representations are readily applicable to the performance analysis of a triple-branch MRC receiver. Furthermore, the average bit error probability (ABEP) is then derived and analytically studied. The proposed mathematical analysis is accompanied by various numerical results, with parameters of interest the fading severity, the correlation and the power decay factor.

This paper studies the performance of switch and stay combining (SSC) diversity receivers operati... more This paper studies the performance of switch and stay combining (SSC) diversity receivers operating over correlated Ricean fading satellite channels. Using an infinite series representation for the bivariate Ricean probability density function (PDF), the PDF of the SSC output signal-to-noise ratio (SNR) is derived. Capitalizing on this PDF, analytical expressions for the corresponding cumulative distribution function (CDF), the moments of the output SNR, the moments generating function (MGF), and the average channel capacity (CC) are derived. Furthermore, by considering several families of modulated signals, analytical expressions for the average symbol error probability (ASEP) for the diversity receivers under consideration are obtained. The theoretical analysis is accompanied by representative performance evaluation results, including average output SNR (ASNR), amount of fading (AoF), outage probability (P out ), average bit error probability (ABEP), and average CC, which have been obtained by numerical techniques. The validity of some of these performance evaluation results has been verified by comparing them with previously known results obtained for uncorrelated Ricean fading channels.

Electronics Letters, 2009

This paper studies the performance of the quadrivariate Weibull distribution with arbitrary corre... more This paper studies the performance of the quadrivariate Weibull distribution with arbitrary correlation assuming non-identical fading parameters and average powers. Novel infinite series representations for the joint probability density function (PDF), the cumulative distribution function (CDF) and the product moments are derived. Using these theoretical results, a performance analysis study in terms of outage probability, for receivers employing selection combining (SC) diversity techniques is presented. The proposed mathematical analysis is accompanied by various numerical results, with parameters of interest the fading severity and the power decay factor. Furthermore, equivalent performance evaluation results, obtained by various computer simulations have verified the accuracy of the proposed analytical method.

IEEE Signal Processing Letters, 2008

The correlated bivariate -distribution with arbitrary and not necessarily identical parameters is... more The correlated bivariate -distribution with arbitrary and not necessarily identical parameters is introduced and analyzed. Novel infinite series expressions for the joint probability density function and moments are derived for the general case where the associated bivariate distributions, i.e., Rayleigh and gamma, are both arbitrary correlated. These expressions generalize previously known analytical results obtained for identical parameter cases. Furthermore, considering independent gamma distributions, the cumulative distribution and characteristic functions are analytically obtained. Although the derived expressions can be used in a wide range of applications, this letter focuses on the performance analysis of dual branch diversity receivers. Specifically, the outage performance of dual selection diversity receivers operating over correlated fading/shadowing channels is analytically evaluated. Moreover, for low normalized outage threshold values, closed-form expressions are obtained.

Starting from on a recently introduced Gaussian class bivariate Weibull stochastic model, the pro... more Starting from on a recently introduced Gaussian class bivariate Weibull stochastic model, the probability density and the cumulative distribution functions of the product (Z1 Z2) c and the ratio (Z1/Z2) c , when Z1 and Z2 are correlated Weibull random variables belonging to this class (c > 0), are derived in closed form. Moreover, using the inequality between arithmetic and geometric mean, a union upper bound for the distribution of the sum of two correlated Weibull variates Z c 1 + Z c 2 is also presented. Special cases of our results are in agreement with previously published ones. The proposed analysis is useful in several scientific fields of engineering.

Towards the realization of the Internet of Things (IoT), cellular networks are expected to play a... more Towards the realization of the Internet of Things (IoT), cellular networks are expected to play a fundamental role, providing the ubiquitous coverage and global internetworking. However, due to the physical limitations, namely energy consumption or hardware complexity, of many of these objects, the direct communication with the cellular infrastructure is hindered. In this sense, cluster-based networks have been introduced as an efficient solution, offering coverage extension and energy savings. The energy efficiency and performance of these networks can be further enhanced if the devices can choose between two or more cluster-heads towards their connection to the infrastructure. In this paper, we propose a novel cluster-head (CH) selection algorithm, where the nodes can switch between different CHs, according to the corresponding signal strength, in order to maintain a predefined quality of service constraint. We show that the network reliability significantly increases, especially when considering mobile scenarios, where the connection to a CH may be not feasible, due to shadowing. In addition, the CHs are equipped with multiple antennas for enhanced performance. The performance of this scheme is theoretically investigated over correlated Nakagami-m multipath fading channels, subject also to shadowing. By considering Gamma distributed shadow effects, convenient expressions for important statistical metrics are obtained. The theoretical analysis is accompanied by representative performance evaluation results, complemented by equivalent computer simulated ones, which validate the accuracy of the proposed analysis.

Eurasip Journal on Wireless Communications and Networking, 2007

In this paper an approach to the performance analysis of a dual-branch switched-and-stay combinin... more In this paper an approach to the performance analysis of a dual-branch switched-and-stay combining (SSC) diversity receiver, operating over interference-limited Ricean correlated fading environment, is presented. Infinite series expressions are obtained for the output signal-to-interference ratio's (SIR) probability density function (PDF) and cumulative distribution function (CDF). Using these new formulae, the outage probability (OP) and the average symbol error probability (ASEP) for modulation schemes such as noncoherent frequency-shift keying (NCFSK) and binary differentially phase-shift keying (BDPSK) are efficiently evaluated. Numerical results, presented into this paper, are graphically presented and analyzed, in order to point out the effects of fading severity and the level of correlation on the system performances.

IEEE Transactions on Wireless Communications, 2009

The correlated bivariate generalized-K (KG) distribution, with not necessarily identical shaping ... more The correlated bivariate generalized-K (KG) distribution, with not necessarily identical shaping and scaling parameters, is introduced and studied. This composite distribution is convenient for modeling multipath/shadowing correlated fading environments when the correlations between the signal envelopes and their powers are different. Generic infinite series expressions are derived for the probability density function (PDF), the cumulative distribution function (CDF) and the joint moments. Assuming identical shaping parameters, simpler expressions for the PDF, CDF and the characteristic function (CF) are provided, while the joint moments are derived in closed form. Furthermore, the PDFs of the product and ratio of two correlated KG random variables are obtained. Capitalizing on these theoretical expressions for the statistical characteristics of the correlated KG distribution, the performance analysis of various diversity reception techniques, such as maximal ratio combining (MRC), equal gain combining (EGC) and selection diversity (SD), over bivariate KG fading channels is presented. For the SD, the outage probability is studied, while for the MRC and EGC the average bit error probability is obtained. The proposed analysis is accompanied by numerical results, clearly demonstrating the usefulness of the theoretical approach as well as the appropriateness of the KG distribution to model multipath/shadowing fading channels.