M. Z. A. Abdul Aziz

Bow-tie microstrip antenna design

In this paper, the bow-tie microstrip antennas have been designed with two different angles of 40deg and 80deg. An investigation on the effect of the angle to the return loss and radiation patterns had been carried out. The impedance matching network with the microstrip transmission line feeding was used in this study. Simulation and measurement results for the return loss and radiation patterns were presented

Physical and MAC Cross Layer Design for Wireless Mesh Networks

Wireless mesh networks (WMNs) are an alternative technology for last-mile broadband Internet access that can support broadband services. However, for a WMN to be all it can be, considerable research efforts are still needed. For example, the available MAC and routing protocols are not scalable; throughput drops significantly as the number of nodes or hops in WMNs increases. Thus, existing protocols need to be enhanced or re-invented for WMNs. When advanced physical layer techniques, used, novel MAC protocols, especially multi-channel MAC, need to be proposed to utilize the agility provided by the physical layer. This paper presents an introduction to wireless mesh networks, IEEE 802.11, physical layer and Medium Access Control (MAC) cross layer design.

SPDT switch with defected ground structure for time division duplex switching in wireless data communication system

A design of single series and double shunt of single pole double throw (SPDT) switch with defected ground structure (DGS) is presented in this paper. SPDT switch is commonly used in a RF transceiver system in modern wireless data communication system to perform time division duplex (TDD) switching for transmit and receive operation. The implementation of DGS in this switch has reduced 35% of the transmission line length and thus, reducing the circuit board size. The performances of SPDT switch with DGS such as insertion loss and isolation are comparable with the normal SPDT switch.

Modified Slotted Patch Electromagnetic Band Gap for Antenna Array Application

A modified slotted patch EBG structure has been investigated by measuring the forward transmission coefficient, S21. The thickness and dielectric constant of the substrate, the size and the gap of the elements in EBG structure has been modified and simulated to see the S21 value and followed by a discussion of the design and the evaluation of the structure itself. The simulation process was carried out using Microwave Office 2006 software. The 3 by 3 modified slotted patch EBG structures which has 11 mm x 11 mm elements size was fabricated using inexpensive fire retardant-4 (FR4) board, using wet etching techniques. The stimulated and measured S21 result shows the band gap of the structure, which are found to be between 2.24 GHz and 2.6 GHz at -20 dB. This structure is then incorporated into a 2 by 2 rectangular microstrip antenna array, operating at 2.4. The result shows that the radiation pattern improved with reducing side and back lobe with an extra gain of 1 dB compared with the antenna without the EBG structure.

Parametric performance simulation of a proximity-coupled fed microstrip dipole array

This work reports on the performance simulation of two element units of microstrip dipole array antennas for WLAN application. Simulation is done using two different simulation techniques, the circuit model (CM) derived from the transmission line model (TLM), and is compared with another simulation set using the method of moments (MoM). Both methods are simulated using Microwave Office. The basic microstrip dipole antenna, which is accurately modeled in a previous work, is adapted, by combining two basic element units. Both simulation sets of MoM and CM are evaluated to determine their level of variation in terms of return loss (S11), bandwidth and resonant frequency (fres). The MoM simulated structure is then fabricated and measured to determine the degree of distinction between hardware and the two simulation sets. MoM simulation set is also simulated over different dimensions to determine the level of variation generated by the alterations. Details of the proposed antenna design and simulation results for 2.45 GHz WLAN band are presented and deliberated.

Network and medium access control (NET - MAC) layers for Wireless Mesh Network (WMN)

Wireless Mesh Networks provide a cost-efficient avenue to extend the coverage of WiFi networks by using multi-hop communication. The capability of enhancing coverage and capacity with low transmission power, wireless mesh networks (WMNs) play a significant role for broadband access with ubiquitous coverage. WMNs have emerged as a key technology for next-generation wireless networking. Because of their advantages over other wireless networks, WMNs are undergoing rapid progress and inspiring numerous applications. However, many technical issues still exist in this field. In order to provide a better understanding of the research challenges of WMNs, this paper presents a detailed review on MAC and Network layer for Wireless mesh network and also proposing innovative protocol that may improve throughput for multi-hop mesh communication. This paper also discussed the criteria that must be considered in order to design a scalable MAC for WMNs.

Ray-tracing propagation prediction for wireless mesh networks (WMNs)

Nowadays, a lot of research efforts and technical papers are done on ad-hoc networks and wireless local area networks (WLAN). Recently, however wireless mesh networking is attracting significant interest from academia, industry, and standard organizations because it is offer several favorable characteristics such as dynamic self-organization, easy maintenance and reliable services. A network with several transmitters and receivers that communicate to each other will form a mesh network topology. Once the transmitter launches a ray, it will be reflected, refracted or diffracted to any kind of surfaces such as the concrete wall. That process will decrease the received signal strength at the receiver. So, ray-tracing technique can be used to analyze the network performance. It is a method that used to determine the ray paths that emanate from the transmitter (Tx) and arrive at the receiver (Rx), and also an efficient approach in determining the propagation issues in wireless environment. So, this paper will be focused on Ray-Tracing techniques and WMNs theories.