International Journal of Communications


ISSN: 1998-4480
Volume 11, 2017

Notice: As of 2014 and for the forthcoming years, the publication frequency/periodicity of NAUN Journals is adapted to the 'continuously updated' model. What this means is that instead of being separated into issues, new papers will be added on a continuous basis, allowing a more regular flow and shorter publication times. The papers will appear in reverse order, therefore the most recent one will be on top.

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Volume 11, 2017


Title of the Paper: Performance Enhancement Using Unitary Frequency Modulation with PLC and VLC Cooperation

 

Authors: Ye Tian, Chang-Jun Ahn

Pages: 34-38

Abstract: Visible light communication (VLC) is expected as a means for ubiquitous communication using increasingly popular LED lights. However, for indoor optical channel, the received signals are with line of sight (LOS) component but also delayed components due to reflected secondary paths. Therefore, the energy is spread over the time, resulting in a reduction of the converted current at the photodiode. From this reason, the diversity gain of VLC is rarely expected as compared to radio frequency systems. To improve the VLC performance, we consider the combination of power line communication (PLC) and VLC systems for achieving the frequency diversity with unitary space-time modulation. In this paper, we propose the diagonal components of unitary signal constellation with splitting over the coherence bandwidth, and evaluate the system performance for PLC-VLC/OFDM.


Title of the Paper: Simulated Annealing Based Femtocell Power Control in Heterogeneous LTE Networks

 

Authors: Aykut Kalaycıoğlu, Ahmet Akbulut

Pages: 27-33

Abstract: In two-layer heterogeneous femtocell LTE networks co-channel interference is a limiting factor for the overall system performance. Since both femtocell and macrocell users share the same frequency spectrum, there exists a co-channel interference in the downlink direction. In this study, a power management scheme for macrocells and femtocells in a heterogeneous network, based on simulated annealing optimization algorithm, is employed to adjust the transmission power of the femtocell base stations to mitigate the co-channel interference. The algorithm tries to maximize the signal-to-interference plus noise ratio of the users while minimizing the transmission power of the femtocell base stations. The simulation results show that any noticeable signal-to-interference plus noise ratio doesn’t occur for femtocell users while reducing the femtocell average power consumption dramatically. Besides, the signal-to-interference plus noise ratio for macrocell users is improved though. Thus, simulated annealing based power management is an effective solution to mitigate the co-channel interference for both the femtocell users and macrocell users in a heterogeneous Long Term Evolution network.


Title of the Paper: Simulation of Quantum Wires with Resonant Transmission Lines

 

Authors: C. D. Papageorgiou, T. E. Raptis, A. C. Boucouvalas

Pages: 22-26

Abstract: We use the previously introduced Resonant Transmission Line (RTL) method for numerically tackling the problem of a 1D quantum wire with arbitrary curvature allowing fast, efficient computation of both eigenvalues and eigenfunctions. Analysis reveals a strict dependency of the energy eigenvalues to the curvature magnitude with significant lowering and even vanishing of the first harmonic beyond a threshold value which severely affects excitability of each eigenfunction.


Title of the Paper: Macrodiversity Outage Performance in the Presence of Weibull Short Term Fading, Gamma Long Term Fading and α-κ-µ Co-channel Interference

 

Authors: Dragana S. Krstic, Siniša G. Minić, Srdjan Milosavljevic, Bojana Milosavljević, Mihajlo C. Stefanovic

Pages: 14-21

Abstract: Macrodiversity reception containing of macrodiversity selection combining (SC) receiver and two microdiversity SC receivers in the presence of short term fading, long term fading and co-channel interference is considered in this article. Desired signal experiences Weibull short term fading, correlated Gamma long term fading and co-channel interference experiences α-κ-µ short term fading and correlated Gamma long term fading. In this article, probability density function and cumulative distribution function of Weibull random process and α-κ-µ random process ratio are evaluated. Theses expressions are used for evaluation cumulative distribution function of signal to interference ratio at outputs of microdiversity SC receivers and cumulative distribution function of macrodiversity SC receiver output signal to interference ratio. Outage probability can be evaluated from cumulative distribution function. The influence of Weibull short term fading nonlinearity parameter, α-κ-µ short term fading severity parameter, α-κ-µ short term fading nonlinearity parameter, α-κ-µ short term fading Rician factor, Gamma long term fading severity parameter and Gamma long term fading correlation coefficient are analyzed.


Title of the Paper: Resonant Transmission Line Modeling of Holey Photonic Crystal Fibers

 

Authors: E. Georgantzos, T. E. Raptis, A. C. Boucouvalas, C. D. Papageorgiou

Pages: 8-13

Abstract: A holey optical fiber with hexagonal modulation of the refractive index is studied with the aid of the Resonant Transmission Line (RTL) method. We show how to obtain an average approximation of the radial refractive index profile that helps to simplify the final lay out of the transmission line model for all three spatial components of the electric and magnetic fields respectively.


Title of the Paper: Level Crossing Rate of Macrodiversity in the Presence of Mixed Short Term Fading, Gamma Long Term Fading and Co-channel Interference

 

Authors: Dragana Krstic, Srdjan Milosavljevic, Bojana Milosavljevic, Suad Suljovic, Mihajlo Stefanovic

Pages: 1-7

Abstract: In this paper, macrodiversity with macrodiversity selection reception and two microdiversity selection receptions operating over short term fading channel in the presence of long term fading and co-channel interference is considered. Desired signal in both, the first and the second microdiversity receivers is subjected to Rayleigh short term fading and Gamma long term fading. Co-channel interference in the first microdiversity receiver experiences Nakagami-m short term fading and Gamma long term fading and co-channel interference in the second microdiversity receiver experiences Rician short term fading and Gamma long term fading. Level crossing rate of the ratio of Rayleigh random variable and Nakagami-m random variable and the ratio of Rayleigh random variable and Rician random variable is evaluated. These formulae are used for calculation the level crossing rate of macrodiversity selection combining (SC) receiver output signal to interference ratio. The influence of Nakagami-m short term fading severity parameter and Rician κ factor on level crossing rate is analyzed and discussed.