Indoor localization has recently witnessed an increase in interest due to its wide range of potential services. Further, the location information is very important in many applications, such as the Internet of Things, logistics, library management and so on. Hence, different technologies and techniques have been proposed in the literature for indoor localization systems. Most of these systems present the disadvantages of a poor performance, low accuracy and high cost. However, thanks to its low cost, high accuracy and non-line-of-sight detection, radio frequency identification (RFID)-based localization has increasingly become the most used technology for indoor localization. In this paper, we propose an innovative approach based on the multiple input single output (MISO) protocol to improve the accuracy of a low-cost RFID localization system. Whereas most traditional systems use a single tag for localization, the proposed architecture encourages the use of a group of RFID tags named as a constellation. According to experimental results and based on the signals’ diversity, the location accuracy is improved to get an estimated position error of 81 cm at the cumulative distribution function of 90%.

A theoretical method based on the induction equivalence principle and Green's functions is presented here to calculate the scattered electromagnetic fields from exterior plane building facades in urban environment. The reflection coefficient of the whole inhomogeneous structure can be calculated for different incidence angles. The derivation of appropriate Green's functions is presented. The method takes into account the large-scale discontinuities on the facade. It is simple to implement and fast to obtain results because of the absence of poles in the Green's functions expressions. The accuracy of the method is discussed comparing to a commercial software and physical optics as another method based on equivalent currents. The article concludes with a statistical study on the influence of concrete permittivity variation on the reflection coefficient of a concrete–glass building facade.

The aim of this paper is to propose a statistical analysis of the performance of an RFID system in a high-density context, based on a physical model which takes into account the mutual coupling and random position of tags. The read-range of an isolated tag is measured and validated from simulation. The degradation in terms of read-range and the power absorbed by the RFID chip is analysed in the presence of surrounded shortcircuited tags. Then a set of randomly distributed RFID tags are modelled by a set of loaded half-wave dipoles distributed over an electrically small area to observe the absorbed power on circuitlevel. An impedance matching technique employing a T-match has been adapted with dipoles for maximum power transfer in the forward link. The coupling effects taking into account the randomness of dipoles are studied using linear and circular polarisations of the incident field. Numerical Electromagnetics Code (NEC) simulator and High-Frequency Structure Simulator (HFSS) are used for the assessment of forward links for dipoles (with and without T-match) and tags respectively.

This paper proposes an improved model for the nonlinear behavior of the components of Radio-over-Fiber (RoF) links focusing here on the laser source. In a previous work, it was shown with a flexible new opto-microwave design approach a first behavioral model of RoF links that exploited the hyperbolic tangent function (the so-called tanh model) to model the high-power nonlinearities. Since this was not sufficient to simulate adequately all the nonlinearities, in this work, for the first time in the authors' knowledge, the improved nonlinear model based on Cann's model is developed, on an electro optic transducer. Then the amplitude-to-amplitude conversion of the link is better taken into account with the introducing of nonlinear properties of the link at high input power in the model. The new transfer equation includes several parameters that can be adjusted to adapt the model to any of the components, especially the photo-emitters under study, which are the main cause of this type of nonlinear behavior of the system. In particular, this improved model is applied on the state-of-the-art 850 nm GaAs Vertical Cavity Surface Emitting Laser (VCSEL), simulating several Figures of Merit such as the Error-Vector Magnitude (EVM) of a Long Term Evolution (LTE) signal with a Quadrature Phase Shift Keying (QPSK)and the output amplitude-modulated power versus input amplitude-modulated power, also called AM/AM curve. This new proposed nonlinear model outperforms other existing behavioral models and its non linear simulation better fits with the measurements. Finally, we conclude that the performance improvement highly depends on the nonlinearity sharpness parameter, depending on the frequency and the bias current.

In UHF RFID (radio frequency identification), passive tag antennas can be fixed on boxes or recipients where the nature and contents might vary. These variations strongly affect the antenna performance. A combined antenna is proposed to ensure an effective read‐range for a plastic recipient containing water or not. Two separate antennas are first designed for the filled and unfilled cases, respectively, then combined for a correct working in both configurations.