Performance Evaluation And Enhancement Of EDCA Protocol To Improve The Voice Capacity In Wireless Network

Enhanced Distributed Channel Access (EDCA) protocol is used to support quality of service (QoS). However, using the default parameter values for EDCA protocol leads to increasing the collisions in the wireless network and decreasing the capacity. This is due to the default EDCA protocol gives the access point and wireless stations the same priority to access the medium, in spite of the access point has high load traffic compared with normal wireless stations. Therefore, in this research work a new algorithm was proposed to enhance the capacity of the EDCA protocol and increase the number of the active voice users. The idea of the algorithm was based on creating different contention window ranges between access point and wireless workstations, and changing the technique of increasing the contention window value when the collision happened. Through the proposed algorithm, the Minimum Contention Window (CWmin) and Arbitration Inter Frame Space (AIFS) parameters were adapted based on the percentage of the collision in the network. By applying the proposed algorithm, the throughput of EDCA protocol was increased by 42.9% and it can support 14 voice users rather than 11 in the default EDCA protocol. The QoS requirements were achieved when the network contained 14 voice users. The end to end delay became 86.44 ms and the packet loss percentage was 0.06 %. In addition to that the uplink and downlink voice throughputs covered the data rate requirements. Moreover, a new mathematical model was designed based on the Markov chain mechanism in order to evaluate the performance of the EDCA protocol under saturation and non saturation conditions, which aimed to separate between the uplink and downlink throughputs with different data types. The separation between uplink and downlink throughputs is based on separating the model equations between the access point and the stations. This separation contributes in determining the effect of access point on the network performance as well as it allows in evaluating the algorithms that based on the differentiation between the access point and stations. The OPNET simulator and the mathematical model were used to evaluate the performance for the proposed algorithm. Therefore, by applying the proposed algorithm, the collisions in network will be decreased and leading to the enhancement of the network capacity. It is believed that this study is useful to cover more voice users in the public wireless network that deployed in bus stations, restaurants, parks, airports and etc

Enhanced symmetrical split ring resonator for metallic surface crack detection

An enhanced sensor based on symmetrical split ring resonator (SSRR) functioning at microwave frequencies has been proposed in order to detect and characterize the metal crack of the materials. This sensor is based on perturbation theory, in which the dielectric properties of the material affect the quality factor and resonance frequency of the microwave resonator. Conventionally, coaxial cavity, waveguide, dielectric resonator techniques have been used for characterizing materials. However, these techniques are often large, and expensive to build, which restricts their use in many important applications. Thus, the enhanced bio-sensing technique presents advantages such as high measurement sensitivity with the capability of suppressing undesired harmonic spurious and permits potentially metal crack material detection. Hence, using a High Frequency Structure Simulator (HFSS) software, the enhanced sensor is modeled and the reflection S11 is performed for testing the aluminum metal with crack and without crack at the frequency range of 100 MHz to 3GHz. Variation of crack width and depth has been investigated and the most obvious finding emerged from this study is that the ability of detecting a minimum of sub-millimeter crack width and depth which is a round 10 m width or depth where the minimum shift of reflected frequency is recorded at 6.2 MHz and 3 MHz for crack width and depth respectively. The enhanced SSRR provides high capability of detecting small crack defection by utilizing the interaction between coupled gap resonators and it is useful for various applications such as aircraft fuselages, nuclear power plant steam generator tubing, and steel bridges and for others that can be compromised by metal fatigue

Analysis And Investigation Of A Novel Microwave Sensor With High Q-Factor For Liquid Characterization

In this paper, a new design of microwave sensor with high Q-factor for liquid characterization is analyzed and investigated. The new microwave sensor is based on a gap waveguide cavity resonator (GWCR). The GWCR consists of upper plate, lower plate and array of pins on the lower plate. The liquid under test (LUT) is characterized by placing it inside the GWCR where the electric field concentrates using a quartz capillary that is passing through microfluidic channels. The results show that the proposed sensor has a high Q-factor of 4832. Moreover, the proposed sensor has the ability to characterize different typesof liquids such as oils, ethanol, methanol and distilled water. The polynomial fitting method is used to extract the equation of the unknown permittivity of the LUT. The results show that the evaluated permittivity using the proposed sensor has a good agreement with the reference permittivity. Therefore, the proposed sensor is a good candidate for food and pharmaceutical application

Analysis and investigation of a novel microwave sensor with high Q-factor for liquid characterization

In this paper, a new design of microwave sensor with high Q-factor for liquid characterization is analyzed and investigated. The new microwave sensor is based on a gap waveguide cavity resonator (GWCR). The GWCR consists of upper plate, lower plate and array of pins on the lower plate. The liquid under test (LUT) is characterized by placing it inside the GWCR where the electric field concentrates using a quartz capillary that is passing through microfluidic channels. The results show that the proposed sensor has a high Q-factor of 4832. Moreover, the proposed sensor has the ability to characterize different types of liquids such as oils, ethanol, methanol and distilled water. The polynomial fitting method is used to extract the equation of the unknown permittivity of the LUT. The results show that the evaluated permittivity using the proposed sensor has a good agreement with the reference permittivity. Therefore, the proposed sensor is a good candidate for food and pharmaceutical applications

Compact CPW-Fed Broadband Circularly Polarized Monopole Antenna With Inverted L-Shaped Strip And Asymmetric Ground Plane

The design of a coplanar waveguide-fed (CPW-fed) broadband circularly polarized printed monopole antenna is proposed. The antenna consists of a simple rectangular radiator monopole, an inverted L-shaped strip, a horizontal stub, and a modified asymmetric ground plane. Simulation results indicate that the impedance bandwidth (IBW) is 121% (1.575-6.4 GHz), and the axial ratio bandwidth (ARBW) is 64.3% (2.85-5.55 GHz). A parametric study is performed for verification. Results: indicate that the proposed antenna is suitable for different wireless communications systems

Microfluidic Biochemical Sensor Based On Circular SIW-DMS Approach For Dielectric Characterization Application

This work proposes an advancement of microwave planar resonator sensor with high sensitivity for microfluidic dielectric characterization. The physical design was employed based on circular substrate integrated waveguide (CSIW) with an integration of defected microstrip structure (DMS). This approach can be applied to accelerate the dielectric detection, structure miniaturization and material differentiation. The presented sensor operates based on variations in the dielectric properties of solvents in the vicinity of a planar open-ended microstrip resonator device. Further analysis in volume and concentration were performed to validate the reliability of the sensor. Validation and functionality of the sensor were investigated by experimental and results comparison. A mathematical model was developed to determine the dielectric constant and the loss tangent of the microfluidic samples. The average error detection has a lower percentage value of 0.11% by comparison to the commercial and ideal dielectric properties of the aqueous samples. The maximum relative error detection, ±0.37% implied better accuracy compared to the existing resonator sensors with more than 400 of the Q-factor. The proposed CSIW-DMS sensor was found to give higher accuracy and detection response; besides easier to fabricate, and compatible for integration with other electronic components in an RF sensor for variety of application

A novel explanatory hybrid artificial bee colony algorithm for numerical function optimization

Over the past few decades, there has been a surge of interest of using swarm intelligence (SI) in computer-aided optimization. SI algorithms have demonstrated their efcacy in solving various types of real-world optimization problems. However, it is impossible to fnd an optimization algorithm that can obtain the global optimum for every optimization problem. Therefore, researchers extensively try to improve methods of solving complex optimization problems. Many SI search algorithms are widely applied to solve such problems. ABC is one of the most popular algorithms in solving diferent kinds of optimization problems. However, it has a weak local search performance where the equation of solution search in ABC performs good exploration, but poor exploitation. Besides, it has a fast convergence and can therefore be trapped in the local optima for some complex multimodal problems. In order to address such issues, this paper proposes a novel hybrid ABC with outstanding local search algorithm called β-hill climbing (βHC) and denoted by ABC–βHC. The aim is to improve the exploitation mechanism of the standard ABC. The proposed algorithm was experimentally tested with parameters tuning process and validated using selected benchmark functions with diferent characteristics, and it was also evaluated and compared with well-known state-of-the-art algorithms. The evaluation process was investigated using diferent common measurement metrics. The result showed that the proposed ABC–βHC had faster convergence in most benchmark functions and outperformed eight algorithms including the original ABC in terms of all the selected measurement metrics. For more validation, Wilcoxon’s rank sum statistical test was conducted, and the p values were found to be mostly less than 0.05, which demonstrates that the superiority of the proposed ABC–βHC is statistically signifcant