Khalida Ghanem

A Directive Dual-Band Antenna Based on Metallic Electromagnetic Crystals

This letter presents the design of a dual-band electromagnetic crystal antenna. The design is based on controlling the metallic wire crystal resonances by using different row periods. To analyze and predict the antenna radiation pattern behavior at the two frequency bands, the transmission coefficient parameter is used. To validate the proposed approach, numerical and experimental results are presented, and a good agreement is achieved

On the Performance Enhancement When Combining STBC and Channel Estimation Techniques in Underground MIMO Channels

One way to enhance the channel data rate in enclosed environments is by incorporating multiple-input-multiple-output (MIMO) systems. Very often, this comes at the cost of data reliability. Motivated by the proven efficiency of space-time block coding (STBC) technique in conventional MIMO systems in improving the communication quality, we propose to incorporate it in wireless underground MIMO communication system and investigate data reliability at the reception in terms of bit error rate (BER). For this purpose, an intensive channel measurement campaign was performed in a mine-laboratory in northern Canada to obtain the perfect channel state. As a second step, the underground MIMO channel is estimated by sending a pilot sequence and using minimum mean square error (MMSE) principle on the received pilots. The resulting MIMO channel estimate is used to evaluate the data part in the STBC block and perform a decision using the maximum likelihood (ML) detector. Moreover, both the channel and transmitted data estimates are given analytically, and the degradation of the BER performance of the system due to MMSE estimation errors is studied using Monte Carlo simulations.

Achievable capacity in underground channels using MIMO antenna systems

Average capacity is investigated using designed multiple input multiple output (MIMO) antenna systems in underground mine channels. This achievable capacity is evaluated in terms of SNR when two power allocation schemes are adopted with MIMO systems, namely uniform power and waterfilling, and compared to SISO case.

New variable-rate variable-power adaptive modulation scheme for time-varying MIMO channels

Recently, multiple-input multiple-output (MIMO) technology has emerged as a new paradigm of highly spectrum-efficient wireless communications. This paper describes a MIMO system, and presents variable-power variable-rate MQAM modulation in MIMO systems. The proposed rate quantization algorithm is described, followed by the simulation results and a brief conclusion.

On the channel capacity in MIMO systems for aeronautical channels

This paper investigates the capacity behavior in an aeronautical MIMO link between a terrestrial transmitting station and an airborne station. The channel model is small-area and considers only the scattering function. For this purpose, two different scenarios are simulated and analyzed. In the first one, only reflected scattered paths are considered and the second scenario adds a line of sight (LOS) component. The channel effect on the capacity and the capacity variation due to antenna rotation during flight are the main topics investigated. To enhance the channel capacity, the direct paths must be decorrelated by either a space-time coding or by polarization diversity.

Adopting ordered weighted averaging approach in multitaper temporal channel estimates to enhance channel capacity

This letter proposes to collect the most of temporal channel information from the frequency domain by exploiting the diversity offered from the fusion of multiple windows, commonly known as tapers. For this, frequency-domain measurements are filtered out by using the selected windows, weighted, and then combined prior to the application of the inverse Fourier transform, thereby adopting a dual temporal concept of multitaper spectrum estimate technique. We have opted for multitaper principle due to the previous findings with the spectrum estimate technique that, with a unique window, more or less a significant amount of the original data is discarded, leading to the increase of the estimates variance, and causing a leakage of energy across frequencies. In this letter, the windows weights are selected by adopting ordered weighted averaging method, which involves the solution of a constrained nonlinear optimization problem, such as this one, with a given orness degree as the constraint, and the maximum entropy as the objective function. This concept has been successfully applied to our multiple-input–multiple-output underground channel measurements carried out in a mine in Northern Canada using channel sounding technique in the frequency domain.

Real ECG signal acquisition with shimmer platform and using of compressed sensing techniques in the offline signal reconstruction

In this paper, the best ECG signal recovery quality of the realistic ECG signal and on which compressed sensing techniques have been applied, is investigated. The contribution of this paper is two folds: Firstly, a real-time ECG signal acquisition is performed using a Shimmer platform. Secondly, the collected are processed by the mean of compressed sensing approach to reduce the signal size and cope with the sensors requirements of high energy efficiency, thus a longer battery life. The recovery of the original signal is afterwards ensured by resorting to Orthogonal Matching Pursuit (OMP) and Matching Pursuit (MP) algorithms and PSNR is used as a metric for the reliability of the signal reconstruction. Several tests are carried out each time by either modifying the type and the size of the dictionaries or the number of iterations. It is shown that the best signal reconstruction is achieved by a value of PSNR that reaches 57 dB.

Off-body performance of patch antenna in underground mine

This paper presents the performance of a patch antenna in an off-body channel within a mine gallery. A measurement campaign was performed in a gold mine in order to characterize the off-body channel by determining the channel parameters. Measurements were performed in the frequency domain using the Vector Network Analyzer (VNA). Hence, the channel parameters were determined from the measured frequency responses, namely, the channel impulse response, path loss, RMS delay spread, coherence bandwidth, and capacity.

Characterization of an on-body quasi-static channel in underground mine environment

In this paper, the on-body performance of three quasi-static channels was evaluated, when the human body undergoes certain typical movements. The main contribution of this work is the analysis of the impact of body movements on the performance of the on-body system in a mine environment. The quasi-static channels parameters were determined and compared to those of a corresponding static channel.

An experiemental system-based analyis of humain body motions using embedded sensors

Wireless sensor networks technology knows a wide spread in numerous applications and fields. In this paper, a realistic IMOTE wireless sensor system is used to evaluate the on-body propagation quality in a laboratory indoor environment. Different on-body links are investigated using a set of movements and the received signal strength (RSS) parameter is evaluated. Herein the results pertaining to the belt-back and belt head channels are presented. The slow and fast fading components are separated and modeled and the results are then analyzed.