In this letter, an analytically tractable model based on diffraction theory is proposed to describe the perturbations of the electromagnetic propagation of radio signals caused by the presence of a moving object in the two-dimensional (2-D) area near the transmitting/receiving devices. This novel model is instrumental to the evaluation of non-cooperative device-free localization (DFL) systems as it allows to relate the received signal strength measurements of multiple radio links to the object size, orientation and position. The proposed model is validated experimentally using radio devices and it is used to derive closed-form fundamental limits to DFL accuracy, providing an analytical tool for DFL system design and network 2-D pre-deployment assessment.

In this paper, we investigate the performance achievable with pattern and polarization multielement reconfigurable antennas in narrowband and broadband multiple-input-multiple-output (MIMO) systems by means of two-port reconfigurable circular patch antennas (RCPAs). We use field measurements collected in an indoor environment to determine the channel capacity achievable with the RCPAs when used at one or at both ends of the communication link. To conduct this analysis, we use two types of RCPAs: 1) an RCPA with two different antenna configurations, exploiting only pattern diversity and 2) an RCPA with three different antenna configurations, exploiting both pattern and polarization diversity. The benefits offered by each state (i.e., excited radiation pattern and polarization) of the RCPAs are investigated in both line-of-sight (LOS) and nonline-of-sight (NLOS) scenarios. The analysis shows the effectiveness of each array configuration in increasing the diversity level of the system and the amount of signal power received in LOS and NLOS communication links. The radiation efficiency and the level of pattern and polarization diversity of each configuration are investigated to explain the performance offered by this class of antennas in MIMO systems. Finally, we show the difference in performance achievable with these antennas when employed in narrowband or broadband communication systems.

In this letter, we show how an operational microwave link network can be used to reconstruct 2-D fields of accumulated rainfall over a limited area at ground level. To this purpose, we use a tomographic technique that exploits the relation between rainfall rate and the attenuation experienced by the microwave links of the network. The links located in Italy operate at K-band and are managed by an Internet service provider. The results are validated by comparing the reconstructed rainfall maps with those derived from a network of conventional rain gauges. Finally, we assess by simulation the impact of the network’s density and topology on the accuracy of the reconstruction algorithm.

In this letter, a simplified human body model based on the scalar diffraction theory is proposed. It allows us to evaluate the effects of a moving person on the propagation of radio signals originated from a communication network deployed close by. This novel model overcomes the limitations due to size and position constraints usually employed for static knife-edge representations with paraxial approximation, without introducing the complexity of a complete electromagnetic (EM) body simulation. The model is experimentally validated and quantifies the effects of position, size, orientation, and small movements of a human body on the received radio signal. It also evaluates the impact of source polarization. Finally, the model results are compared against full EM simulations.

This article proposes a multibody electromagnetic (EM) model for the quantitative evaluation of the influence of multiple human bodies in the surroundings of a radio link. Modeling of human-induced fading is the key element for the development of real-time device-free (or passive) localization (DFL) and human presence-aware systems (HPS) based on the processing of the received signal strength (RSS) data recorded by radio frequency devices. The proposed physical–statistical model is able to relate the RSS measurements to the position, size, orientation, and random movements of people located in the link area. This novel EM model is thus instrumental for crowdsensing, occupancy estimation, and people counting applications for indoor and outdoor scenarios. This article presents the complete framework for the generic N-body scenario where the proposed EM model is based on the knife-edge approach that is generalized here for multiple targets. The EM-equivalent size of each target is then optimized to reproduce the body-induced alterations of the free-space radio propagation. The predicted results are then compared against the full EM simulations obtained with a commercially available simulator. Finally, experiments are carried out to confirm the validity of the proposed model using IEEE 802.15.4-compliant industrial radio devices.