Towards a generalized methodology for smart antenna measurements

The huge expansion of mobile communications and the need for high data rate services require more efficient use of the spectrum to increase the capacity of networks and enhance the quality of services. Within that frame, the adoption of Smart Antenna techniques in future wireless systems is expected to have a significant impact on the aforementioned needs. Following the proliferation of the use of Smart Antennas systems there is a growing need for characterization of such systems which is still an open issue. In this work, a generalized methodology for Smart Antenna characterization measurements is introduced. Simulation results from the application of the proposed measurement procedure using a reference array to characterise the smart antenna algorithm subsystem are presented

Reconfigurable Intelligent Surfaces vs. Relaying: Differences, Similarities, and Performance Comparison

Reconfigurable intelligent surfaces (RISs) have the potential of realizing the emerging concept of smart radio environments by leveraging the unique properties of meta-surfaces. In this article, we discuss the potential applications of RISs in wireless networks that operate at high-frequency bands, e.g., millimeter wave (30-100 GHz) and sub-millimeter wave (greater than 100 GHz) frequencies. When used in wireless networks, RISs may operate in a manner similar to relays. This paper elaborates on the key differences and similarities between RISs that are configured to operate as anomalous reflectors and relays. In particular, we illustrate numerical results that highlight the spectral efficiency gains of RISs when their size is sufficiently large as compared with the wavelength of the radio waves. In addition, we discuss key open issues that need to be addressed for unlocking the potential benefits of RISs.Comment: Submitted for journal publication (revised version

An SINR balancing based multiuser relaying scheme

We consider a relay network with multiple users and propose a signal-to-interference and noise-ratio (SINR) balancing based relay signal forwarding scheme. Each relay receives a combined signal from multiple sources and processes it using a complex valued scalar and transmits towards the destinations so that the SINR at the receiver of each user is maximised. We solve this problem using semidefinite and geometric programming along with bisection search methods. The performance of the proposed scheme has been studied in terms of worst case SINR for various numbers of users and relays. © 2010 IEEE

An SINR balancing based multiuser relaying scheme

We consider a relay network with multiple users and propose a signal-to-interference and noise-ratio (SINR) balancing based relay signal forwarding scheme. Each relay receives a combined signal from multiple sources and processes it using a complex valued scalar and transmits towards the destinations so that the SINR at the receiver of each user is maximised. We solve this problem using semidefinite and geometric programming along with bisection search methods. The performance of the proposed scheme has been studied in terms of worst case SINR for various numbers of users and relays. © 2010 IEEE

Evaluation of a terrain-based point-to-point propagation model in the 900 MHz band

The accuracy of a semi-empirical point-to-point propagation model, based on terrain data information close to the receiver, is tested. The evaluation is performed through extended transmission loss measurements taken in an urban environment (Athens region) in the 900 MHz band. The prediction error is calculated for each measurement point and coordinated with detailed terrain information. Specifically, the evaluation of the model is separately performed for various categories of measurement data with respect to the measurement point's effective height and line-of-sight conditions. © 1997 by John Wiley & Sons, Ltd

Tissue equivalence of diamond for heavy charged particles

A dedicated Geant4 study was developed to determine a correction factor (C) to convert the energy deposition response in diamond to water for heavy charged ions, with atomic number (Z) greater than 2 with energies typical of Galactic Cosmic Rays. The energy deposition response within an ideal diamond based microdosimeter was modelled and converted into a microdosimetric spectrum. The simulation was then repeated, substituting diamond with water. It was shown that by applying the correction factor, the energy deposition and microdosimetric response in diamond could be matched to that of water. The correction factor was determined to be C = 0.32 to 0.33. This study has shown a weak dependence of the correction factor C with respect to the Z of the projectile. The correction factor remains applicable for converting microdosimetric spectra in diamond to water for Galactic Cosmic Rays. This result is extremely encouraging and indicative of the applicability of diamond for use in radioprotection applications in space environments