Browsing by Subject "Visible light positioning"

Now showing 1 - 6 of 6

Open Access
Intelligent reflecting surfaces for visible light positioning based on received power measurements
(IEEE, 2024-09) Kökdoğan, Furkan; Gezici, Sinan
In this paper, we formulate and analyze a received power based position estimation problem for visible light positioning (VLP) systems in presence of intelligent reflecting surfaces (IRSs). In the proposed problem formulation, a visible light communication (VLC) receiver collects signals from a number of light emitting diode (LED) transmitters via line-of-sight (LOS) paths and/or via reflections from IRSs. We derive the Cramér--Rao lower bound (CRLB) expression and the maximum likelihood (ML) estimator for generic three-dimensional positioning in the presence of IRSs with arbitrary configurations. In addition, we consider the problem of optimizing the orientations of IRSs when line-of-sight (LOS) paths are blocked, and propose an optimal adjustment approach for maximizing the received powers from IRSs based on analytic expressions, which can be solved in closed form or numerically. Since the optimal IRS orientations depend on the actual position of the VLC receiver, an N-step localization algorithm is proposed to perform adjustment of IRS orientations in the absence of any prior knowledge about the position of the VLC receiver. Performance of the proposed approach is evaluated via simulations and compared against the CRLB. It is deduced that although IRSs do no provide critical improvements in positioning accuracy in the presence of LOS signals from a sufficient number of LED transmitters, they can be very important in achieving accurate positioning when all or most of LOS paths are blocked
Embargo
IRS aided visible light positioning with a single LED transmitter
(Elsevier, 2025-01) Tarhan, Efe; Kökdoğan, Furkan; Gezici, Sinan
We propose a visible light positioning (VLP) system with a single light emitting diode (LED) transmitter and an intelligent reflecting surface (IRS) for estimating the position of a receiver equipped with a single photo-detector. By performing a number of transmissions from the LED transmitter and optimizing the orientation vectors of the IRS elements for each transmission, position information is extracted by the receiver based on power measurements of the signals reflecting from the IRS. The theoretical limit and the maximum likelihood (ML) estimator are presented for the proposed setting. In addition, an algorithm, named IRS focusing, is proposed for determining the orientations of the IRS elements during the localization process. The effectiveness of the proposed localization approach is demonstrated through simulations. Furthermore, extensions are provided to apply the proposed approach in the presence of partial prior information about the receiver position and when the IRS is located at the LED transmitter.
Open Access
Optimal and robust power allocation for visible light positioning systems under illumination constraints
(IEEE, 2019-01) Keskin, Musa Furkan; Sezer, Ahmet Dündar; Gezici, Sinan
The problem of optimal power allocation among light emitting diode (LED) transmitters in a visible light positioning system is considered for the purpose of improving localization performance of visible light communication (VLC) receivers. Specifically, the aim is to minimize the Cramér-Rao lower bound (CRLB) on the localization error of a VLC receiver by optimizing LED transmission powers in the presence of practical constraints, such as individual and total power limitations and illuminance constraints. The formulated optimization problem is shown to be convex and thus can efficiently be solved via standard tools. We also investigate the case of imperfect knowledge of localization parameters and develop robust power allocation algorithms by taking into account both overall system uncertainty and individual parameter uncertainties related to the location and orientation of the VLC receiver. In addition, we address the total power minimization problem under predefined accuracy requirements to obtain the most energy-efficient power allocation vector for a given CRLB level. Numerical results illustrate the improvements in localization performance achieved by employing the proposed optimal and robust power allocation strategies over the conventional uniform and non-robust approaches.
Open Access
Optimal pulse design for visible light positioning systems
(Elsevier BV, 2021-10-16) Yazar, Onurcan; Gezici, Sinan
The problem of optimal pulse design for light-emitting diode (LED) transmitters is investigated in an indoor visible light positioning (VLP) setup. In particular, the problem of localization performance maximization is formulated for both asynchronous and synchronous VLP systems with consideration of practical limitations related to power consumption, illumination levels, and/or effective bandwidths, while quantifying the localization accuracy via the Cramér–Rao lower bound (CRLB). In both asynchronous and synchronous scenarios, the formulated problems are shown to be convex optimization problems, and some properties of the optimal solutions are derived. In addition, the pulse design problem for minimum power consumption is formulated under a CRLB constraint along with other practical limitations; and this problem is also revealed to be a convex optimization problem. Based on the solutions of the proposed optimization problems, pulse design procedures are described to determine the parameters of optimal pulse shapes. Numerical results illustrate the benefits of the proposed optimal pulse design approach in comparison with the state-of-the-art optimal power allocation scheme in the literature. In particular, electrical power consumption can be reduced by around 45% or localization accuracy can be improved by as much as 25% via the proposed optimal pulse design approach in certain scenarios.
Open Access
Optimal signal design for visible light positioning under power and illumination constraints
(2021-11) Yazar, Onurcan
The optimal design of transmit signals for light-emitting diodes (LEDs) in a visible light positioning (VLP) system is analyzed with the objectives of im-provements in localization accuracy and power eﬃciency. Speciﬁcally, the lo-calization performance maximization problem is addressed for asynchronous and synchronous VLP systems where certain system limitations including power con-sumption, illumination, and eﬀective bandwidth are considered, and the localiza-tion performance is quantiﬁed using the Cram´er-Rao lower bound (CRLB). The formulated signal design problems are demonstrated to be convex optimization problems and some properties of the optimal signal design parameters are found. On the other hand, the signal design problem is also formulated for achieving the lowest possible power consumption while guaranteeing a certain localization ac-curacy. Then, the optimal signal design parameters resulted from the solution of these optimization problems are used to construct the optimal transmit signals in the LEDs. The advantages of the optimal signal design approach is demonstrated through the numerical experiments while also presenting a comparison with the state-of-the-art optimal power allocation method in the literature.
Embargo
Visible light positioning with intelligent reflecting surfaces under mismatched orientations
(Elsevier BV, 2024-12-30) Iddrisu, Issifu; Gezici, Sinan
Accurate localization can be performed in visible light systems in non-line-of-sight (NLOS) scenarios by utilizing intelligent reflecting surfaces (IRSs), which are commonly in the form of mirror arrays with adjustable orientations. When signals transmitted from light emitting diodes (LEDs) are reflected from IRSs and collected by a receiver, the position of the receiver can be estimated based on power measurements by utilizing the known parameters of the LEDs and IRSs. Since the orientation vectors of IRS elements (mirrors) cannot be adjusted perfectly in practice, it is important to evaluate the effects of mismatches between desired and true orientations of IRS elements. In this study, we derive the misspecified Cramér–Rao lower bound (MCRB) and the mismatched maximum likelihood (MML) estimator for specifying the estimation performance and the lower bound in the presence of mismatches in IRS orientations. We also provide comparisons with the conventional maximum likelihood (ML) estimator and the CRB in absence of orientation mismatches for quantifying the effects of mismatches. It is shown that orientation mismatches can result in significant degradation in localization accuracy at high signal-to-noise ratios.