Browsing by Author "Karbalayghareh, M."

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Channel modelling and performance limits of vehicular visible light communication systems
(IEEE, 2020-07) Karbalayghareh, M.; Miramirkhani, F.; Eldeeb, Hossıen Badr; Kızılırmak, R. Ç.; Sait, S.Q.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELDEEB, Hossien Badr Hossien
Visible light communication (VLC) has been proposed as an alternative or complementary technology to radio frequency vehicular communications. Front and back vehicle lights can serve as wireless transmitters making VLC a natural vehicular connectivity solution. In this paper, we evaluate the performance limits of vehicular VLC systems. First, we use non-sequential ray tracing to obtain the channel impulse responses (CIRs) for vehicle-to-vehicle (V2V) link in various weather conditions. Based on these CIRs, we present a closed-form path loss expression which builds upon the summation of geometrical loss and attenuation loss and takes into account asymmetrical patterns of vehicle light sources and geometry of V2V transmission. The proposed expression is an explicit function of link distance, lateral shift between two vehicles, weather type (quantified by the extinction coefficient), transmitter beam divergence angle and receiver aperture diameter. Then, we utilize this expression to determine the maximum achievable link distance of V2V systems for clear, rainy and foggy weather conditions while ensuring a targeted bit error rate.
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Comparative performance evaluation of VLC, LTE and WLAN technologies in indoor environments
(IEEE, 2021) Zeshan, A.; Karbalayghareh, M.; Miramirkhani, F.; Uysal, Murat; Baykas, T.; Electrical & Electronics Engineering; UYSAL, Murat
Recent years have seen an exponential rise in the demand for indoor wireless connections that have driven future generation networks to aim for higher data rates with extended coverage and affordable rates. The two most prominent technologies for providing indoor wireless connections, WLAN and LTE, have their limitations and they can not coexist in a single band to form heterogeneous networks (HetNets). Visible light communication (VLC) has seen rapid growth in recent years as it has the capability to seamlessly merge with the existing technologies and provide wireless connections with high data rates. VLC based hybrid indoor network effectively combines the preferences of an end-user with the practicality of implementation. In this work, we investigate specific VLC/WLAN and VLC/LTE hybrid scenarios to perform a detailed analysis on the effect of user mobility on the performance of the system and how the performance of the network (in terms of throughput) can be maximized. The study aims to show how different technologies complement each other in the best and even the worst-case scenarios.
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Effect of scattering phase function on underwater visible light communication channel models
(Elsevier, 2021-10) Miramirkhani, F.; Karbalayghareh, M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
Non-sequential ray tracing simulations are commonly employed to model underwater visible light communication (VLC) channels. The accuracy of such simulations highly depends on how well the optical properties of water (i.e., absorption and scattering) as well as scattering phase function (SPF) are modeled in the simulation. Existing empirical models are only a function of chlorophyll concentration and particle composition and are independent of refractive index, size and concentration of particles. In this paper, we carry out an underwater VLC channel modeling study using the Mie SPF which provides a full description of the scattering from phytoplankton particles which dominate the optical properties of most oceanic waters. We obtain the channel impulse response (CIR) based on an extensive non-sequential ray tracing study and calculate the fundamental channel parameters such as channel gain and delay spread. Comparison of CIRs reveals out that deployment of simplified SPF models results in the overestimation of path loss with respect to Mie SPF. Our results clearly demonstrate the importance of selecting realistic SPF models for an accurate underwater VLC channel modeling. While highlighting the channel models, we discuss adaptive modulation technique to maximize the data rate under the constraint of a targeted bit error rate. Besides, the maximum achievable distance is also determined both in terms of analytical guarantees and computer simulations. The results reveal that larger transmission distances can be achieved through Mie SPF channel model.
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SLIPT for underwater visible light communications: Performance analysis and optimization
(IEEE, 2021-10) Uysal, Murat; Ghasvarianjahromi, Sara; Karbalayghareh, M.; Diamantoulakis, P. D.; Karagiannidis, G. K.; Sait, S. M.; Electrical & Electronics Engineering; UYSAL, Murat; Ghasvarianjahromi, Sara
In this paper, we investigate simultaneous lightwave information and power transfer (SLIPT) for underwater visible light communication systems. We consider three SLIPT methods namely time switching (TS), power splitting (PS) and time switching-power splitting (TS-PS) where the splitting/switching factors are defined as optimization parameters. For each of these methods, we derive closed-form expressions for the average harvested energy, bit error rate and spectral efficiency in the presence of underwater turbulence modeled by lognormal statistics. Using these expressions, we determine the optimal splitting factors to maximize the harvested energy while satisfying a given bit error rate value and a given threshold spectral efficiency value. Our results reveal that, if not optimized, SLIPT methods under consideration are outperformed by the simple AC-DC separation (ADS) method which provides the largest harvested energy versus spectral efficiency (HE-SE) region. Optimization of splitting/switching factors extends the HE-SE regions; hence, optimized versions of TS, PS and TS-PS methods are able to significantly outperform ADS for most cases. We further investigate the effect of various channel and system parameters such as water type, turbulence level, beam divergence, receiver aperture size on the harvested energy and quantify the improvements in battery lifetime through the use of SLIPT methods.