The localisation of moving and transceiver-free objects is addressed by processing the Received Signal Strength Indicator (RSSI) available at the nodes of a wireless sensor network. Starting from the RSSI measurements, the probability of the presence of unknown mobile objects is determined by means of a customised classification approach based on a support vector machine. Experimental results assess the feasibility of the proposed approach.

This letter presents the design of a planar antenna for ultrawideband (UWB) applications with a bandwidth of 5.5 GHz over 3.7 to 9.2 GHz and return loss values lower than -10 dB. The antenna geometry is described in terms of a spline-based representation whose control parameters, together with other geometrical descriptive quantities, are determined through a suitable particle swarm optimizer (PSO) in order to fit the UWB requirements. Representative results of both numerical and experimental validations are reported in order to assess the performance of the prototype as well as to give some preliminary indications on the reliability and effectiveness of the whole synthesis approach

In this paper, a slot-based electronically steerable parasitic array radiator (ESPAR) antenna suitable for Internetof-Things (IoT) applications is proposed. The antenna can provide 12 directive and 2 slightly different omnidirectional radiation states. The 12 directive patterns allow the antenna to focus the radiated energy towards 6 different directions uniformly distributed in the azimuth plane and with 2 different beamwidths. The reconfiguration of the radiation pattern is based on the use of low-capacitance low-power consuming diodes that can be digitally controlled. The paper details the design of the antenna structure and the practical implementation of the reconfiguration mechanism, discussing the effects of real electronic components on the antenna performance. The antenna effectiveness is numerically and experimentally assessed.

In this letter, a dual-band fractal monopole antenna suitable for Long Term Evolution (LTE) standard is proposed. The antenna geometry is based on a perturbed planar Sierpinski fractal shape, whose geometrical descriptors are determined by means of a particle swarm optimization (PSO). The optimized antenna exhibits a good impedance matching within the LTE bands at 700 and 2600 MHz as well as a 24% size reduction with respect to a standard quarter-wave resonant monopole. The efficiency of the proposed antenna is assessed by means of both simulations and measurements.

Synthesis of ultrawideband (UWB) antennas by means of a particle swarm optimizer (PSO)-driven spline-based shaping approach is described. In order to devise a reliable and effective solution, such a topic is analyzed according to different perspectives: 1) representation of the antenna shape with a simple and efficient description; 2) definition of a suitable description of the UWB Tx/Rx system; 3) formulation of the synthesis problem in terms of an optimization one; 4) integration of the modelling of the UWB system into a computationally efficient minimization procedure. As a result, an innovative synthesis technique based on the PSO-based iterative evolution of suitable shape descriptors is carefully detailed. To assess the effectiveness of the proposed method, a set of representative numerical simulations are performed and the results are compared with the measurements from experimental prototypes built according to the design specifications coming from the optimization procedure. To focus on the main advantages and features of the proposed approach, comparisons with the results obtained with a standard parametric approach are reported, as well.

Reconfigurable directional antennas (RDA) bring new opportunities to reduce data collision in wireless sensor networks (WSN). In this letter, a new reconfigurable directional antenna-based receiver-Initiated cycled receiver (RDA-RICER) medium access control (MAC) protocol is proposed for WSN nodes equipped with switched antennas. A low complexity and energy efficient scanning process is embedded in RDA-RICER to identify the direction providing the highest received signal strength Indicator between two nodes. OMNeT++ simulation results for a single hop network show that data collision rate can be drastically reduced compared with related MAC protocols, leading to a significant decrease in energy consumption. Our approach is also validated in the field using WSN platforms equipped with a four-direction RDA, and powered by solar cells.