Mohamad Ghaddar

A Conducting Cylinder for Modeling Human Body Presence in Indoor Propagation Channel

We demonstrate that in indoor radio propagation modeling, the presence of the human body may be approximated by a conducting circular cylinder at microwave frequencies. Therefore, a perfect tool such as the uniform theory of diffraction may be used to predict the diffracted field over a smooth circular surface. To validate the model, vertically and horizontally polarized continuous wave (CW) measurements were performed at 10.5 GHz between two fixed terminals inside a room along with the presence of an obstacle (person or metallic cylinder) moving along predetermined parallel and perpendicularly crossing paths with respect to the line-of-sight direction. Results indicate that there is a strong correlation between the effects of the human body and those of a conducting circular cylinder. The simulation results successfully agree with the CW experimental measurements.

Experimental Characterization of an UWB Propagation Channel in Underground Mines

An experimental characterization of the ultrawideband (UWB) propagation channel in an underground mine environment over the frequency range from 3 GHz to 10 GHz is reported in this paper. Two kinds of antennas, directional and omnidirectional, were used to investigate the effect of the antenna directivity on the path loss propagation and on the time dispersion parameters in both line-of-sight (LOS) and no-line-of-sight (NLOS) underground galleries. The measurement and simulation results show that the path loss exponents in an underground environment are larger than their counterparts in an indoor environment. In NLOS, the directional-directional (Direct-Direct) antenna combination showed better radiation efficiency for reducing the time dispersion parameters while the omnidirectional-omni directional (Omni-Omni) case resulted better performance in term of path loss. After extracting the channel parameters, a statistical modeling of the UWB underground channel based on data measurements was conducted.

Modeling human body effects for indoor radio channel using UTD

In this paper, a practical deterministic propagation prediction model is introduced to investigate the human body-scattering effects in the indoor channel using the uniform geometrical theory of diffraction (UTD). In the model, the human body is approximated with a perfect conducting circular cylinder and then combined with the ray-tracing technique to deal with particular indoor propagation scenarios. By maintaining both the transmitter and the receiver at fixed positions, we investigated the nature of propagation due to the movement of the cylinder in a predetermined parallel path with respect to the line-of-sight (LOS) path between the transmitter and receiver. In order to validate the developed model, continuous wave (CW) experimental measurements are conducted and have successfully fitted the predicted data. Results also indicate that reflections onto persons are significant and will have to be considered in developing a full deterministic model of the indoor propagation channel.

Deflecting-Obstacle Effects on Signal Propagation in the 60 GHz Band

This paper reports the non-line-of-sight (NLOS) results of broadband measurements and modeling of signal propagation characteristics in the 60 GHz band. The purpose of this work was to evaluate the importance of the presence of deflecting obstacles (DOs) for indoor wireless local area network (WLAN) applications in the unlicensed 60 GHz band. Based on sweeping-frequency sounding technique (59.6-60.6 GHz), an indoor propagation measurement campaign was carried out in a typical T-shaped intersection of two long corridors under non-line-of-sight (NLOS) at a distance of 20 meters between transmit and receive antennas, with and without the presence of DOs. Based on Ray-Tracing (RT) technique, deterministic models are derived for the considered environment. An interesting agreement is achieved between the predicted and the experimental results in both frequency and time domains. Thus, this work demonstrates that mm-waves communications are very sensitive to the propagation environment as compared with lower frequency bands. In NLOS corridor environments, the signal transmission relies mainly on the unavoidable diffraction phenomenon from the intersection corners. However, the presence of a DO might overcome significantly the hostile propagation characteristics that are normally encountered under NLOS propagation conditions.

Experimental analysis of human body effects on NLOS 60 GHz propagation channel

Reported are the results of an experimental investigation of human body scattering effects on non-line-of-sight (NLOS) 60 GHz broadband propagation channel. Based on sweeping-frequency sounding technique (59.6 - 60.6 GHz), an indoor propagation measurement campaign is carried out in a typical L-shaped intersection of two corridors, each with a length of 10 m. Thus, with and without the presence of a person at the corridors intersection, the channels statistical propagation characteristics are extracted and analyzed. The channels performance is investigated in terms of RMS delays, path loss and Ricean K-factor fading distributions. The experimental results show that NLOS mm-wave propagation characteristics are very hostile where a severe path loss is recorded in the NLOS corridors under consideration. Moreover, unlike line-of-sight (LOS) channel, the presence of person in the considered channel enhances NLOS propagation characteristics and thus, provides a better signal coverage.

MIMO Propagation Measurements in Underground Mine Using Beamforming Butler Matrix Networks

The advantages of integrating beamforming Butler matrix in 4×4 Multiple-Input MultipleOutput (MIMO) systems for underground mine wireless communications in the 2.4 GHz band are investigated. To satisfy both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, two separate measurement campaigns are performed in a real L-shaped underground mine gallery; the first uses 4elements beamforming conformal microstrip patch arrays (CMPA), while the second uses 4-elements beamforming Butler Network (BN-MIMO) by means of connecting a planar microstrip patch array to a Butler matrix. Due to its high radiation efficiency, the latter shows further performance for enhancing the channel propagation characteristics, and thus, for reducing the average path loss by about (2.2 dB, 5.1 dB) under (LOS, NLOS) conditions, respectively. Similarly, a reduction of (0.67 ns, 37 ns) in the RMS delay spread has been achieved to result in an additional gain of (46 MHz, 0.82 MHz) in the channel’s coherence bandwidth. Furthermore, the orthogonal property of BN array radiation beams has led to a suppression of about (6%, 11%) in inter-subchannels correlations to boost (1.1 bit/s/Hz, 4.35 bit/s/Hz) in the channel capacity.

Experimental characterization of NLOS broadband millimeter wave links

This study investigates the potential use of microwave scatterers (MS) for data transmission relay in order to extend the signal coverage over shadowed remote places where lineof-sight (LOS) transmission is not present. Series of indoor NLOS-CW (non-LOS continuous wave) measurements over the 29-30 GHz band were conducted at the intersection of two hallways in presence of two metallic cylinders of different diameters, a right angle standing metallic corner, and a flat surface metallic reflector. Results indicate that for systems operating at a short range of tens of meters, MS provides an alternative to LOS systems, cables or the use of repeaters. It was also found that some types of MS yield better signal coverage while others deflect the signal destructively. Hence, the received signal strength depends strongly on the MSs shape, size and surface roughness. (5 pages)