Yasir Alfadhl

LTE-A an overview and future research areas

This paper gives an overview of the Long Term Evolution (LTE) of the Universal Mobile Telecommunication System (UMTS), which is being developed by the 3rd Generation Partnership Project (3GPP). LTE constitutes the latest step towards the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications. Particular attention is given to the requirements and targets of LTE, its use of multiple antenna techniques, and to the Single Carrier Frequency Division Multiple Access (SC-FDMA) modulation scheme used in the LTE uplink. Furthermore new future research areas are proposed here.

Radiofrequency heating of nanomaterials for cancer treatment: Progress, controversies, and future development

In recent years, the application of nanomaterials to biological and biomedicine areas has attracted intensive interest. One of the hot topics is the nanomaterial mediated radiofrequency (RF) hyperthermia or ablation, i.e., using RF fields/waves to heat tumor tissues treated with nanomaterials to destroy cancerous cells while minimizing the side-heating effect. However, there are currently many contradictive results reported concerning the heating effect of nanomaterials under a RF field. This paper provided a comprehensive review to nanomaterial mediated RF ablation from both experimental and theoretical aspects. Three heating mechanisms were discussed, i.e., laser heating, magnetic field heating, and electric field heating in RF spectrum, with the focus on the last one. The results showed that while diluted pure metallic nanoparticles could be heated significantly by a laser through the surface plasmon resonance, they cannot be easily heated by a RF electric field. Further studies are proposed focusing on nanoparticle structure and morphology, electromagnetic frequency and localized heating effect to pave the way for future development.

An investigation of the effects of TETRA RF fields on intracellular calcium in neurones and cardiac myocytes

Purpose: This study aimed to determine whether Terrestrial Trunked Radio (TETRA) fields can affect intracellular calcium signalling in excitable cells. Materials and methods: Intracellular calcium concentration ([Ca2 + ]i) was measured in cultured rat cerebellar granule cells and cardiac myocytes during exposure to TETRA fields (380.8875 MHz pulse modulated at 17.6 Hz, 25% duty cycle). [Ca2 + ]i was measured as fura-PE3, fluo-3 or fluo-4 fluorescence by digital image analysis. Results: Granule cells exposed at specific absorption rates (SARs) of 5, 10, 20, 50 or 400 mW · kg−1 showed no significant changes in resting [Ca2 + ]i. Increases in [Ca2 + ]i in response to potassium-induced depolarization were significantly different from sham controls in TETRA-exposed cells, but the majority of the difference was attributable to initial biological variation between cell cultures. No difference was found between fura-PE3 (UV excitation) and fluo-3 (visible light excitation) measurements in these cells. Exposure to TETRA (50 or 400 mW · kg−1) had no significant effect on either the rate or amplitude of spontaneous Ca2 + transients in cardiac myocytes. The cells showed normal responses to salbutamol (50 μM) and acetylcholine (10 μM). Conclusions: Overall, these results showed no evidence of any consistent or biologically relevant effect of TETRA fields on [Ca2 + ]i in granule cells and cardiac myocytes at any of the SAR tested.

Conductivity and frequency dependent specific absorption rate

Recently, a number of contradicting results have been reported regarding the electromagnetic (EM) energy absorption by highly conductive materials in a liquid phase. The argument rises from the fact that higher conductive media absorb more electromagnetic energy; this however would be constrained by the localized field values that are dictated by the dielectric variations, which may reduce the absorption rate. Using salted water as an example, a systematic investigation of the mechanisms of EM absorption in the presence of highly conductive materials is conducted in this work. A theoretical model is developed, which is supported by both numerical and experimental studies. The influence of salt concentration, dielectric properties, boundary conditions, and EM frequency on the specific absorption rate (SAR) is carefully examined. The results show that the presence of salt in water modifies the dielectric properties significantly in the RF range, while the effect is less prominent in the microwave range. The...

Electromagnetic heating effect of aggregated gold nanoparticle colloids

Gold nanoparticles (GNPs) have been recently investigated intensively for potential hyperthermia treatment of malignant cancer cells in combination with radiofrequency (RF) electromagnetic (EM) fields/waves. However, many controversial results have been reported on whether GNPs can be heated by EM fields. It has been suggested that aggregated GNPs may be heated significantly by a RF field, which however has not been examined experimentally. This work proposes a novel electric treatment of mono-dispersed particles to create aggregated GNPs, and conducts an investigation of their bulk heating behavior under a 655 nm laser and a 13.56 MHz RF electric field. It is revealed that the heating rates of aggregated colloids are significantly higher than those of mono-dispersed GNPs for the 655 nm laser, whereas at 13.56 MHz, the heating effects are barely noticeable for both aggregated and mono-dispersed colloids. Various possible reasons are discussed and the negligible electric field enhancement is believed to be responsible at 13.56 MHz.

Study of an Eighth-Harmonic Large-Orbit Gyrotron in the Terahertz Band

A 0.42-THz eighth-harmonic large-orbit gyrotron (LOG) operating with TE8,1,1 mode has been designed and studied. The LOG design is characterized by the requirement of low external magnetic field and short cavity length to limit the ohmic loss. The cold cavity analysis is presented and followed by the hot cavity simulation with the 3-D particle-in-cell code. It is shown in the initial hot test that by proper choice of the electron beam source, the eighth harmonic of the electron cyclotron resonance can be selectively excited at 0.42 THz with an output power of 3.8 kW, which requires an external magnetic field as low as 2.8 T. Based on the model, the starting oscillation process of TE8,1,1 mode at the eighth harmonic and the dynamic of beam-wave interaction are investigated. Upon verification of the design and modeling, a number of parameter variation studies are conducted to draw broader conclusions about the beam-wave interaction behavior in a high-harmonic LOG. The design procedure and the conclusion of this paper can be generalized and applied to other LOGs.

Efficient dynamic scheduling scheme between vehicles and roadside units based on IEEE 802.11p/WAVE communication standard

In recent years, Vehicle Ad Hoc Networks (VANETs) have become very popular. A typical VANET defines an intelligent way of using vehicular networking by integrating vehicular connections via a number of short-distance ad-hoc networking links, such as the IEEE802.11p. This type of system could provide effective communication between moving vehicles and fixed Road Side Units (RSUs), which are usually very expensive to install and may, in some cases, undergo heavy demand. To improve the efficiency of communication between vehicles and RSUs (Vehicle to Infrastructure, V2I), most existing work ignores the following facts: the uneven distribution of vehicles and unbalanced working loads on different RSUs. By considering the periodic and the unchanging features of public transportation, we propose a novel V2I hybrid optimisation scheme named Dynamic Resources Allocation Scheme (DRAS). In this scheme, all resources on the RSUs are scheduled as a whole and buses will be introduced as moving infrastructure points (or relay stations) to take some of the burden of the RSUs in real-time traffic conditions. We import the Variable-Length Contention Free Period (VL-CFP) for MAC access and also define Time-to-Live (TTL) value to guarantee the data credibility on bus. Using both Math analysis and NS-2 simulation, we can prove our DRAS can achieve a better QoS performance and adequate utilisation of RSU resources than legacy 802.11p and WAVE-based HCCA. These advantages become more obvious as the vehicles number increases.

Quad band circular polarized antenna

A novel quad band circular polarized stacked patch antenna has been designed for global navigation satellite systems. The presented antenna operates in the three GPS carrier bands (L1, L2, L5) and the 2.3 GHz frequency band. The stacked patch technique has been used while the antenna performances are analyzed in respect to the simulated s-parameters, radiation patterns and axial ratios. The antenna is potentially suitable for use in mobile or satellite communication receivers.

Evaluation of ad-hoc routing protocols in vehicular ad-hoc network using OPNET

Vehicular Ad-hoc NETwork (VANET) is becoming a promising technology in which moving vehicles are able to exchange information between them without the need of infrastructure. The original idea of VANET is for the safety purposes such as warning the drivers when there is an accident happened in the front of the road. Nowadays, VANET is extended to offer more services like downloading emails transfer, assessing Internet and Global Positioning System (GPS) services. To make sure that information transmitted correctly, an efficient routing protocol is crucial and indispensable for coping with the rapid topology changes. In this paper, we developed an OPNET model to evaluate the VANET performance of Ad-hoc On-demand Distance Vector (AODV) and Dynamic Source Routing (DSR) protocols in the city with different scenarios. We found out that AODV outperforms DSR protocol in VANET with increasing vehicles.

A novel Wide-Band reflection-based system for measuring abdominal fat in humans

A Wide-Band (WB) radio frequency (RF) system has been thoroughly developed in order to measure the Subcutaneous Fat (SF) thickness in the abdominal region of humans. Recent conducted research has shown that the SF thickness is related to the thickness of internal fat called Visceral Fat (VF), which has important health implications, and therefore cannot be measured accurately by non-invasive techniques. Thus, this proposed noninvasive RF system offers the possibility of measuring the SF thickness and then estimating the VF thickness. The investigation details work carried out to optimise the penetration depth and the range resolution. These considerations resulted in a Gaussian pulse with a 1.45 GHz centre frequency and 462 MHz bandwidth being selected for the system. This has been implemented using an accurately designed compact antenna based on double-ridged horn (DRH) inside a high-permittivity material, which has been designed using the CST Microwave Studio (MWS) software. The employed abdominal model consisted of three layers: skin; fat, and muscle. The WB pulse has been directed at the model, and the reflections recorded for several SF thicknesses, including an infinitely thick layer, which provided the reference system pulse to compare the other cases with. This successfully demonstrated the principles of the system operation, with SF thickness of 10 to 30 mm being accurately measured, based on amplitude variations and also time shifting, in the proposed RF system.