A novel Multi-permittivity Cylindrical Dielectric Resonator Antenna for Wideband Applications

In this paper, a novel multi-permittivity cylindrical dielectric resonator antenna for wideband application is presented. The multi-permittivity cylinder is formed by combining two different permittivity material sectors in such a way that each sector (with constant permittivity) is 90 degree apart. A direct microstrip line coupling terminated with T-stub at the open end is used to excite the multi-permittivity cylindrical dielectric resonator. The angular position of the multi sector dielectric resonator with respect to the longitudinal axis of the microstrip line and length of the additional strip at the open end of the feeding circuit is key parameters for wideband operation of the antenna. By optimizing all parameters of the proposed antenna, wideband impedance bandwidth of 56% (12.1 GHz - 21.65 GHz) is achieved. The average gain of the antenna throughout the bandwidth is 5.9 dB with good radiation properties in both E-plane and H-plane. A well matched simulation and experimental results show that the antenna is suitable for wideband applications

Improving IEEE 802.11 to Support Quality of Service in Wireless Networks

This paper investigates and describes the Quality of Services (QoS) provisioning techniques for IEEE 802.11 based networks, focusing on the Distributed Coordination Function (DCF). This paper propose better techniques to provide QoS by assigning new parameters to the DCF access method, involving the DCF Interframe Space (DIFS), backoff time and the maximum data packet size to high priority nodes, which will distinguish the high priority traffic from the low priority traffic to support QoS. A simulation is done using Network Simulator 2 (NS-2) and the expected output is then presented

Achieving Stable Throughput to Support QoS in IEEE 802.11 Wireless Networks

This paper investigates and describes a new provisioning technique for IEEE 802.11 based networks, focusing on the ad-hoc Distributed Coordination Function (DCF) to redefine stability of the network throughput to support QoS. This paper propose better techniques to achieve stable throughput in Wireless LAN networks by assigning new values to the Contention Window to high priority traffics which will guarantee better throughput to the selected network traffic. A simulation is done using Network Simulator 2 (NS-2) and findings are then presented. Results showed that stable throughput can be achieved to provide better traffic flows especially for real-time traffic and multimedia applications

Improving IEEE 802.11g Mac to Support Quality of Service for Multimedia Applications in Wireless Networks

This paper paper investigates, describes and propose better techniques to provide QoS by assigning new metrics to the DCF access method, involving the DCF Interframe Space (DIFS), Contention Window values and the maximum data packet size to high priority nodes, which will bias towards high priority multimedia traffic to support QoS. A simulation is done using Network Simulator 2 (NS-2) and comparisons were made between different sets of network simulation scenarios. Improvements on throughput, delay and jitter can clearly be seen and further analysis is then presented

A Novel Approach on Teaching Network Security for ICT Courses

This paper discusses a curriculum approach that will give emphasis on practical sessions of teaching network security subjects in information and communication technology courses. As we are well aware, the need to use a practice and application oriented approach in education is paramount [1]. Research on active learning and cooperative groups showed that students grasps and have more tendency towards obtaining and realizing soft skills like leadership, communication and team work as opposed to learning using the traditional theory and exam based method. While this teaching and learning paradigm is relatively new in Malaysia, it has been practiced widely in the West. This paper examines a particular approach whereby students learning wireless security are divided into small manageable groups consisting of black hat and white hat team. The former will try to find and expose vulnerabilities in a wireless network while the latter will try to prevent such attacks on their wireless networks using hardware, software, design and enforcement of security policy and etc. This paper will try to demonstrate whether this approach will result in a more fruitful outcome in terms of students concept and theory understandings and motivation to learn

Performance of Silicon Solar Cell with Various Surface Textures

The performance of solar cell with various surface texture patterns was reported. Wet, RIE, one and two dimensions texturing with and without the nitride antireflection coating were compared. An I-V tester calibrated by Sandia National Laboratory was used. The surface texture of the solar cells were as follows (a) solar cell with 2D texturing without nitride antireflection, (b) solar cell with 1D texturing with nitride antireflection (c) solar cell with 1D texturing without nitride antireflection, (d) solar cell with wet texturing without nitride antireflection, (e) solar cell with wet texturing with nitride antireflection (f) solar cell with RIE texturing with nitride antireflection. RIE and two dimension surface texturing showed the best output with maximum short density current of 0.042 mA/cm2 and of 0.045 mA/cm2 respectively

Behavioral Analysis on IPv4 Malware in both IPv4 and IPv6 Network Environment

Malware is become an epidemic in computer net-work nowadays. Malware attacks are a significant threat to networks. A conducted survey shows malware attacks may result a huge financial impact. This scenario has become worse when users are migrating to a new environment which is Internet Protocol Version 6. In this paper, a real Nimda worm was released on to further understand the worm beha-vior in real network traffic. A controlled environment of both IPv4 and IPv6 network were deployed as a testbed for this study. The result between these two scenarios will be analyzed and discussed further in term of the worm behavior. The ex-periment result shows that even IPv4 malware still can infect the IPv6 network environment without any modification. New detection techniques need to be proposed to remedy this prob-lem swiftly

5.75 GHz Microstrip Bandpass Filter for ISM Band

This paper presents on 5.75 GHz bandpass filter based on IEEE802.11a standard for wireless LAN application. The development of bandpass filter includes calculation, simulation, testing and measurement of the filter parameters process has been presented. Simulation software for this project used Ansoft Designer software. The filter operates at center frequency of 5.75 GHz with 100 MHz bandwidth and insertion loss below 10 dB. The bandpass filter contributes to the application of direct conversion front-end receiver for WLAN application at 5.8 GHz frequency

SINGLE STAGE RF AMPLIFIER AT 5.8GHZ ISM BAND WITH IEEE 802.11a STANDARD

This paper describes the circuit design and measurement of a single stage RF amplifier for 5.8 GHz-band with IEEE 802.11a standards for WLAN applications.The circuit was simulated using Ansoft Designer where a 14dB of gain; input and output return loss less than -10dB were observed. The GaAs Hetrojunction FET (HFET), capacitors and resistors are combined with the microstrip line pattern by silver epoxy. A 1dB output power compression point (P1dB) of 17dBm and 14.56dB of gain when -1dBm power injected under 6V and ½ Idss biasing are measured

Simulation Of Cascading LNA And RF Amplifier For Front-End Direct-Conversion Receiver At 5.8 GHz

In this paper, a simulation of cascaded LNA and RF amplifier for front-end direct conversion receiver at 5.8-GHz frequency band is presented. By using direct conversion architecture, the image rejection performance is improved, lower complexity and the component is reduced. The cascading LNA and RF amplifier has 27 dB gain and 2.17 dB noise figure. The LNA and RF amplifier is simulated using Ansoft Designer software and fabricated with Duroid 5880 as the microstrip material