Showing papers by "Norbahiah Misran published in 2007"

A 4×1 L-probe fed inverted hybrid E-H microstrip patch antenna array for 3G application

Abstract: This paper presents a compact and broadband microstrip patch antenna array (BMPAA) with uniform linear array configuration of 4x1 element for 3G applications. The 4A—1 BMPAA was designed and developed by integrating new patch shape Hybrid E-H shape, L-probe feeding, inverted patch structure with air filled dielectric microstrip patch antenna (MPA) element. The array was constructed using two dielectric layer arrangement with a thick air-filled substrate sandwiched between a top-loaded dielectric substrate (RT 5880) with inverting radiating patch and a ground plane. The Lprobe fed inverted hybrid E-H (LIEH) shaped BMPAA achieves an impedance bandwidth of 17.32% referenced to the center frequency at 2.02 GHz (at VSWR ≤ 1.5), maximum achievable gain of 11.9±1dBi, and 23 dB crosspolarization level.

Ionospheric TEC and scintillation during the 15–16 May 2005 major storm over equatorial anomaly region at ARAU

Abstract: The ionospheric TEC and scintillation measurements were investigated at ARAU, Malaysia station based on GPS measurements during major storm on 15-16 May 2005. The major storm was observed for the period from 12 to 17 May 2005 and was accompanied by a moderate solar activity with F10.7 > 100 and SSN > 100. The maximum readings of geomagnetic indices Dst, Kp and Ap recorded by the World Data Centre (WDC) are -263 nT, 9 and 105 respectively. The solar wind index, Bz showed a sharp incursion to the south with a peak reaching -37 nT. The 15-16 May 2005 storm has only one SSC and is the most intense storm recorded during the solar minimum 2005. The results show pronounced phase and amplitude scintillations and sudden increase in TEC is clearly observed during the storm. The peak phase scintillation recorded during the storm is 0.19 m and the measured amplitude scintillation and S4 index on both L1 and L2 bands are > 13 dB-Hz and > 0.7 respectively.

Architecture and mobility management protocols for next-generation wireless systems (NGWS)

Abstract: Next-generation wireless systems are envisioned to have all Internet Protocol (IP) based infrastructure with the support of heterogeneous access technologies. One of the research challenges for next generation all-IP-based wireless systems is the design of intelligent mobility management techniques that take advantage of IP-based technologies to achieve global roaming among various access technologies. In this paper a new wireless network architecture for mobility management is proposed to integrate the cellular system and Wireless Local Area Network (WLAN) of various providers that may not necessarily have direct service level agreement (SLA) among them. This algorithm considers traffic load as an important factor for initiating handoff. New mobility management protocols are also developed to support vertical handoff between different wireless systems by using the concept of the dynamic boundary area. The dynamic boundary area is determined based on the speed of the user and handoff signaling delay information. A simulation model is developed to study the performance of the proposed algorithm. Performance analysis and simulation results show that this algorithm significantly increases the probability of unnecessary handoff and the use of adaptive value of received signal strength avoids too early or too late initiation of the handoff process.

An Investigation on the Effects of Wall Parameters on the Indoor Wireless Propagations

Abstract: The type of the construction materials of the interior walls of the indoor environments plays a great role in the propagation of the transmitted signals inside the buildings. A comparison of calculated and simulated Fresnel reflection and transmitted coefficients at 2.4 GHz and 900 MHz for a variety of typical exterior building surfaces has been achieved. The effect of the different types of wall on the path loss prediction had been conducted by using a ray tracing program with real time reflection and refraction phenomena.

Remote Sensing of Antarctic Atmospheric Water Vapour using Ground-Based GPS Meteorology

Abstract: Atmospheric precipitable water vapour (PWV) is one of the key components in determining and predicting the global climate system. Accurate quantification and interpretation of their physical characters using sounding technologies are quite difficult, especially in the Antarctic environment due to difficulties of the remote location and maintenance cost. This paper presents a method for deriving atmospheric PWV from ground-based GPS sensing technique. Methods for calculating the Zenith Tropospheric Delay (ZTD), Zenith Hydrostatic Delay (ZHD), Zenith Wet Delay (ZWD) and PWV are given. The Modified Hopfield model with an improvement is used to calculate ZTD, the Saastamoinen model is used to calculate ZHD and the Niell hydrostatic mapping function is used to map the ZTD to the individual satellite view. Scott Base (SBA), Casey (CAS1) and Syowa (SYOG) stations in Antarctica were taken as the observation sites. For the analysis, both GPS and surface meteorological (MET) data over the period of 2003 are presented. Before calculating the PWV, we firstly validate the ZTD determination and compared with the ZTD reference estimated from Center for Orbit Determination in Europe (CODE) Analysis Center. After that ZWD are converted into PWV using surface temperature measured at the site. Good results are achieved for ZTD validation at all stations. From statistical results found that the PWV content were below 10 mm (on average), which are all within 1~2 mm accuracy and showed that climate changes could be monitored through trends in the water vapour time series. Further work planned is to improve global climate model through quantifications, linkages, similarity or differences of either atmospheric processes between Antarctic environment and the equatorial environment.

Handoff architecture in next-generation wireless systems

Abstract: One of the most critical aspects in mobility management is handoff. Handoff is a complex process involving location identification, performance evaluation of available networks at that location, decision to switch to a different network and actions to effect the switching. During the process of handoff, the communication channel between the mobile host and a corresponding host may be broken, and this leads to loss of data. The communication channel is established after the handoff is completed. Hence, there is no communication at least for the duration of handoff, referred to as handoff latency. This paper identifies these problems and performs analyses on the handoff. Then, a simplified system architecture that contains fewer network nodes was proposed. This new architecture consists of mobile IP extensions and a new handoff protocol. We have shown that this new protocol allows to minimize handoff latency and reduce packet loss.

Multiple-Band Antenna for In-building Coverage Operation

Abstract: A monopole disc antenna for multi band system operation is presented. The operating frequency of the proposed in-building antenna includes the GSM 900, GSM 1800 and 3G bands. The antenna structure consists of a two-steps cylinder combined with a circular disc to provide broadband characteristics. This antenna has a VSWR les 1.5 and an omni-directional radiation pattern at all bands. The proposed monopole disc antenna was designed according to stringent electrical and mechanical specifications. In this paper, both simulated and actual measurement results are presented. In addition, we have included a walk-test (field trial) result to verify the antennas performance in an in-building environment.

On the Capacity of Correlated MIMO Channels for Informed and Uninformed Transmitter at Different Antenna Configurations

Abstract: Modern wireless systems continue to demand higher data rates and better reliabilities These demands can be met by using multiple antennas at both sides of the wireless link ie Multiple-Input Multiple-Output (MIMO) The capacity of MIMO correlated Rayleigh channels for different antenna configurations with and without channel knowledge (CSI) at the transmitter is simulated When CSI is available at the transmitter (ie informed transmitter), waterfilling algorithm is used to allocate the power among the transmitter antennas Simulations show that capacity is improved significantly when CSI is known at the transmitter It also shows that the lack in channel knowledge (ie uninformed transmitter) can be compensated for by increasing the number of antennas in the receiver (Mr) When the number of antennas in the transmitter is larger than those in the receiver, using waterfilling becomes necessary to get the optimum capacity

Development of SATB based on LIEH shaped patch antenna for digital beamforming system

Abstract: This paper presents the design and development of the smart antenna system testbed (SATB). The SATB is developed based on using the novel L-probe fed inverted hybrid E-H (LIEH) microstrip patch element design arranged into 4×1 uniform linear array antenna. This paper reports the development of a software reconfigurable testbed for the implementation and evaluation of digital beamforming algorithm for smart antenna systems. The novel SATB developed based on modular design employing two novel designs of LIEH array antenna and software reconfigurable digital beamforming system (DBS). The modular concept of the system provides the capability to test the antenna hardware, beamforming unit, and beamforming algorithm in an independent manner, thus allowing the smart antenna system to be developed and tested in parallel, hence reduce the design time. The digital beamforming system was developed using a high performance TMS320C6711 TM floating-point DSP board and a 4-channel RF front-end receiver developed in-house. The over all peak side lobe level is achieved around at -10 dB for the different scanning angle. The antenna is used for a scan range as far as ± 30°.