Azita Laily Yusof

Gain enhancement of air substrates at 5.8GHz for microstrip antenna array

This paper concerned on enhancement of gain for microstrip patch planar array antenna. The structure in this project is 2 by 2 microstrip patch planar array antenna using air substrate with εr= 1at frequency 5.8 GHz. Frequency for 5.8GHz can be applied to unlicensed WiMAX. In this project, the simulation is performed by using the simulation software Computer Simulation Technology (CST) Microwave Studiowhich is a commercially available electromagnetic simulator based on finite difference time domain technique. The novelty of the design is the application of air to replace regular Flame Retardant 4 (FR-4) materials as the substrate.The substrate used for the design is C-foam (thickness = 3mm) which represent as air gap. Copper foil with thickness 0.12mm is used as the patch. The performance of the designed antenna was analyzed in term of bandwidth, gain, return loss, VSWR, and radiation pattern.

Aperture-Coupled Frequency and Patterns Reconfigurable Microstrip Stacked Array Antenna

This paper investigates a novel structure of a reconfigurable microstrip antenna integrated with the aperture coupling technique which can reduce spurious radiation pattern with stacked patch in order to enhance the gain and bandwidth performance. The antenna design implements a new concept of the frequency reconfigurability methods applying in an aperture-coupled technique. Four PIN diode switches named as Switch A were used to activate the selected aperture slots on the ground, thus resulting in two different operating frequencies either at 2.6 or 3.5 GHz. Meanwhile, an additional four PIN diode switches named Switch B, positioned at the four L-stub elements were used to turn ON the patterns capabilities while maintaining the frequencies. The beam angle of the antenna can be controlled with turning ON Switch C and Switch D alternately in order to activate selected numbers of stacked radiating patches, either the two upper patches or two lower patches. With six cases of the switches configuration, the antenna has the capability to change its patterns with its beam directed at +32°, +3°, or -1° at 2.6 GHz or at +28°, +23°, or -24° at 3.5 GHz.

Performance Analysis of Handover Strategy in Femtocell Network

Femtocells, as known as HeNB is the tremendous network technology in the Long Term Evolution (LTE) network in order to fulfill the upcoming demand of high data rates. However, Femtocells deployment may cause the incidence of frequent and unnecessary handover due to the movement of the user. As Femtocells coverage area is very small and deployed randomly, there are many possible targets Femtocells for handover. This paper analyzed on the performance analysis of handover strategy in Femtocells network under Hybrid Access Mode to minimize the unnecessary handover. The handover strategy for three different threshold stay time with considering the velocity of user equipment (UE) in the mobility are analyzed. The simulation results showed that the proposed algorithm minimized the number of handover and decreased the unnecessary handover probability. Simulation results indicate that the proposed algorithm has a better performance as compare with the traditional strategy

Design of reconfigurable dual-band E-shaped microstrip patch antenna

A novel compact size of reconfigurable E-shaped microstrip single patch antenna was designed and analyzed for dual-band at 3.02 GHz and 6.38 GHz frequencies. The basic antenna was designed to operate at 3.02 GHz and with reconfigurability in frequency, it will operate at 6.38 GHz. The physical parameters of the novel structure as well as its partial ground plane will be analyzed and optimized using commercial computer simulation technology (CST) packages. Return loss (S11), voltage standing wave ratio (VSWR) and gain will be carried out. The return loss of the optimized reconfigurable E-shaped microstrip patch antenna has to be less than -10dB at 3.02 GHz and 6.38 GHz frequencies band. The reconfigurable antenna was then to be measured by vector network analyzer (VNA) to carry out its S11 and VSWR result. The result from simulation and measurement will be compared. The proposed antenna is very promising for various modern communication applications such as wireless and satellite application.

Frequency reconfigurable quasi-Yagi microstrip antenna with beam shaping for WiMAX application

This paper presents a frequency reconfigurable quasi-Yagi microstrip antenna with beam shaping for WiMAX application by using a folded dipole as a driven element. The reconfigurability of this antenna can be achieved by varying length of driven element. The usage of PIN diodes which act as switches will help to vary the length of driven element. This microstrip antenna has use quarter-wave matched T-junction power divider to match the impedances between feed line and driven element. Furthermore, this quasi-Yagi microstrip antenna was originally designed using CST Microwave Studio for operation in 5.8GHz frequency band. However, by changing the driven element length, this quasi-Yagi microstrip antenna can operate at differ frequency and differ directions. In addition, this reconfigurable quasi-Yagi microstrip antenna with switching has been fabricated and experimental results are provided in this paper.

Handover mechanism in dynamic load balancing for LTE systems

Next-generation wireless systems will be conceived to have all Internet Protocol (IP). It is based on infrastructure with the support of heterogeneous access technologies. IP system is the designs of intelligent mobility management technology that have many advantages to achieve global roaming as compare to others technologies. As the user allowed to move freely across different network, the hotspot cells can occur when available wireless resources at some point of location are not sufficient to sustain the needs of users. Therefore, this scenario can potentially leads to high dropped calls rate, which can deteriorate the service quality of users. This paper presents a load balancing scheme that can control the handover time based on the load status of cells. The scheme requests the load information of the target cell in advance to avoid handover to an overloaded target cell. The simulation results show a significant reduction in dropped calls rate which can manage overloaded traffic in the system.

Handover initiation across heterogeneous access networks for Next Generation Cellular Network

The heterogeneous networks are expected to become a main focus in the development toward the Next Generation Cellular Network (NGCN). The heterogeneous networks will allow users to move freely across different networks. However, the determination of the handoff initiation time is difficult in heterogeneous networks since many factors should be considered in the decision algorithm. Therefore, in this research, the main idea is early detection of the possibility of inter access system handoff and then to carry out registration of the mobile in the next domain before the actual handoff. In this paper, first the mathematical formulation for the length of the dynamic boundary area is derived as a function of users speed. Then, an adaptive value of Receive Signal Strength (RSS) threshold is proposed using the estimation of the boundary area to enable the mobile handoffs on time. Numerical analysis is done to evaluate the performance of the handoff initiation using the above mathematical formulations. By incorporating value of speed and handoff signaling delay into adaptive RSS calculation in advance, the system can make better preparation for the handoff so that the mobile handoffs on time.

Traffic Driven Handoff Management Scheme for Next Generation Cellular Networks (NGCN)

In NGCN, mobile users can move between heterogeneous networks. In this kind of environment, handoff management is the essential issue that supports the handoff of users between various wireless technologies. Handoff decision, one of the handoff management issues consists of finding the appropriate time to perform the handoff and which cell to hand over in cellular networks. Traditionally, the need for initiating the handoff arises when the RSS of the serving base station deteriorates below a certain threshold value. However, in a heterogeneous network environment, more criteria (not only RSS) are needed to initiate the appropriate time to perform the handoff. This research presents a traffic driven handoff management scheme which adopts a hard handoff scheme to adaptively control the handoff time according to the load status of cells. Before accepting a new user, it requests the load information of the target cell in advance before handoff execution. Then, the value of adaptive RSS is applied in the scheme to initiate the right handoff time. The results show that how the handoff initiation criteria might be set in accordance with the quality of services requested by users. It was found that the proposed scheme can support better service quality than the scheme compared. The scheme could efficiently manage overloaded traffic in the system.

Differences of image classification techniques for land use and land cover classification

Land use and land cover classification of remotely sensed data is an important research and commonly used in remote sensing application. In this study, the different types of classification techniques were used by using satellite image of some part of Selangor, Malaysia. For this objective, the land use and land cover was classified with Landsat 8 satellite image and ERDAS Imagine software as the image processing packages. From the classification output, the accuracy assessment and kappa statistic were evaluated to get the most accurate classifier. The optimal performance would be identified by validating the classification results with ground truth data. Of classified image, the Maximum Likelihood technique (overall accuracy 82.5%) is the highest and more applicable for satellite image classification compared with Mahalanobis Distance and Minimum Distance. The accurate classification can produce the correct Land Use and Land Cover map that can be used for many varieties purposes.

PIN diode switches for frequency-reconfigurable stacked patch microstrip array antenna using aperture-coupled technique

This paper presents a novel design of frequency-reconfigurable antenna by using an aperture-coupled technique as feeding technique and stacked patch technology. The proposed antenna generally consists of three substrate layers (RT-Rogers 5880) and air gap filled between feedline substrate and layer 2 substrates. Four PIN diode (BAP51-02) switches are implemented to configure the length of the feedline by configuring the switches to ON or OFF mode. A new approach of coupling methods is presented. When all the switches are in ON mode, the signal will be passed to the selective aperture slot and activate the particular radiating patch layer to achieve the frequency reconfigurability either at 2.6 GHz or 3.5 GHz. The prototype of the proposed antenna is tested/fabricated with the biasing circuit to validate the performance of the antenna. The simulated and measured results are presented to confirm the performance of the antenna.