Terminal Orientation in OFDM-Based LiFi Systems

Purwita, Ardimas Andi; Soltani, Mohammad; Safari, Majid; Haas, Harald

doi:10.1109/twc.2019.2920132

Cited by 48 publications

(43 citation statements)

References 40 publications

(111 reference statements)

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“…In other words, random angles are generated using the statistics in Table I (Gaussian for walking and Laplace for sitting), and then, the channel gain can be obtained using (4) and (5). The same method as described in [35] is used to obtain the coherence time of α, β and γ. The values are presented in Table I.…”

Section: A Random Orientation Modelingmentioning

confidence: 99%

Bidirectional Optical Spatial Modulation for Mobile Users: Toward a Practical Design for LiFi Systems

Soltani

Arfaoui

Tavakkolnia

et al. 2019

IEEE J. Select. Areas Commun.

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Among the challenges of realizing the full potential of light-fidelity (LiFi) cellular networks are user mobility, random device orientation and blockage. In the paper, we study the impact of those challenges on the performance of LiFi networks in an indoor environment using measurement-based channel models, unlike existing studies that rely on theoretical channel models. In our work, we adopt spatial modulation (SM), which has been shown to be energy efficient in many applications, including LiFi. We consider two configurations for placing the photodiodes (PDs) on the user equipment (UE). The first one is referred to as the screen receiver (SR) whereby all the PDs are located on one face of the UE, e.g., the screen of a smartphone, whereas the other one is a multi-directional receiver (MDR), in which the PDs are located on different sides of the UE. The latter configuration was motivated by the fact that SR exhibited poor performance in the presence of random device orientation and blockage. In fact, we show that MDR outperforms SR by over 10 dB at bit-error ratio (BER) of 3.8×10 −3 . Moreover, an adaptive access point (AP) selection scheme for SM is considered where the number of APs are chosen adaptively in an effort to achieve the lowest energy requirement for a target BER and spectral efficiency. The user performance with random orientation and blockage in the whole room is evaluated for sitting and walking activities. For the latter, we invoke the orientation-based random waypoint (ORWP) mobility model. We also study the performance of the underlying system on the uplink channel where we apply the same techniques used for the downlink channel. Specifically, as the transmitted uplink power is constrained, the energy efficiency of SM is evaluated analytically. It is shown that the multi-directional transmitter (MDT) with adaptive SM is highly energy efficient. Furthermore, as a benchmark, we compare the performance of the proposed framework to that of the conventional spatial multiplexing system, and demonstrate the superiority of the proposed one.

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Section: A Random Orientation Modelingmentioning

confidence: 99%

Bidirectional Optical Spatial Modulation for Mobile Users: Toward a Practical Design for LiFi Systems

Soltani

Arfaoui

Tavakkolnia

et al. 2019

IEEE J. Select. Areas Commun.

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“…The analysis of indoor mobile channels is challenging for several reasons. First, it involves numerous factors such as mobile device orientation [ 7 , 8 , 9 , 10 , 11 , 12 ], distance dependency [ 13 ], shadowing [ 14 , 15 , 16 ], and others. Another aspect is related to reliable simulation of human movement; while realistic human motion simulations are possible, their combination with rigorous channel characterization is still challenging [ 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

Coherence Time Evaluation in Indoor Optical Wireless Communication Channels

Bykhovsky

2020

Sensors

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The coherence time is the time over which the channel-gain-values correlation coefficient drops below a predefined threshold. The coherence time is typically used to quantify the pace of appreciable channel changes and is important, for example, for determining handoff and resource allocation time constraints. The goal of this work is to experimentally measure the coherence time of indoor optical wireless communication (OWC) channels under various mobile scenarios. The amount of movement was quantified by mobile sensor measurements. The experiments show that it is reasonable to assume that the channel varies slowly for a time period of ~100 milliseconds for most mobile scenarios.

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“…This is attributed to the simplicity of the adopted model and also to the lack of proper channel models for the mobility and orientation of VLC devices in indoor scenarios. Nevertheless, several measurement-based channel models for VLC system were derived recently for various environments, such as indoor VLC systems [131]- [137], VLC-based vehicular communication [138] and underwater VLC systems [139], [140].…”

Section: Incorporating Realistic and Measurements Based Vlc Channementioning

confidence: 99%

Physical Layer Security for Visible Light Communication Systems: A Survey

Arfaoui

Soltani

Tavakkolnia

et al. 2020

IEEE Commun. Surv. Tutorials

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155

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Due to the dramatic increase in high data rate services and in order to meet the demands of the fifth-generation (5G) networks, researchers from both academia and industry are exploring advanced transmission techniques, new network architectures and new frequency spectrum such as the visible light and the millimeter wave (mmWave) spectra. Visible light communication (VLC) particularly is an emerging technology that has been introduced as a promising solution for 5G and beyond, owing to the large unexploited spectrum, which translates to significantly high data rates. Although VLC systems are more immune against interference and less susceptible to security vulnerabilities since light does not penetrate through walls, security issues arise naturally in VLC channels due to their open and broadcasting nature, compared to fiber-optic systems. In addition, since VLC is considered to be an enabling technology for 5G, and security is one of the 5G fundamental requirements, security issues should be carefully addressed and resolved in the VLC context. On the other hand, due to the success of physical layer security (PLS) in improving the security of radio-frequency (RF) wireless networks, extending such PLS techniques to VLC systems has been of great interest. Only two survey papers on security in VLC have been published in the literature. However, a comparative and unified survey on PLS for VLC from information theoretic and signal processing point of views is still missing. This paper covers almost all aspects of PLS for VLC, including different channel models, input distributions, network configurations, precoding/signaling strategies, and secrecy capacity and information rates. Furthermore, we propose a number of timely and open research directions for PLS-VLC systems, including the application of measurement-based indoor and outdoor channel models, incorporating user mobility and device orientation into the channel model, and combining VLC and RF systems to realize the potential of such technologies.

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Terminal Orientation in OFDM-Based LiFi Systems

Cited by 48 publications

References 40 publications

Bidirectional Optical Spatial Modulation for Mobile Users: Toward a Practical Design for LiFi Systems

Bidirectional Optical Spatial Modulation for Mobile Users: Toward a Practical Design for LiFi Systems

Coherence Time Evaluation in Indoor Optical Wireless Communication Channels

Physical Layer Security for Visible Light Communication Systems: A Survey

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