Ahmad Zamani Jusoh

Assessment of ITU-R conversion method for 1-minute integration time of precipitation intensity in Malaysia

A study has been embarked with the aim to identify the best formulation capable of obtaining statistics of precipitation intensity at 1-minute integration time from longer integration times. Few years back, the ITU-R has proposed a conversion method claimed to be capable of generating precipitation intensity at 1-minute integration time. Measurement data of precipitation intensities collected in Kuala Lumpur, Malaysia between 1996 and 1998 has enabled the compilation of statistics at several integration times of interest. The generated 1-minute statistics using ITU-R method were then compared with those of measured in order to assess the methods dependability. This paper highlights the findings drawn from the evaluation process. It can be suggested that the ITU-Rs conversion method appears to be capable of producing consistent statistics for 1-minute integration time from various other integration times. In addition, the paper also proposes new values for constants in the conversion formula that has been derived based on measured data.

SDR-Based Transceiver of Digital Communication System Using USRP and GNU Radio

Transmission over wireless channel is challenging. As such, different application required different signal processing approach of radio system. So, a highly reconfigurable radio system is on great demand as the traditional fixed and embedded radio system are not viable to cater the needs for frequently change requirements of wireless communication. A software defined radio or better known as an SDR, is a software-based radio platform that offers flexibility to deliver the highly reconfigurable system requirements. This approach allows a different type of communication system requirements such as standard, protocol, or signal processing method, to be deployed by using the same set of hardware and software such as USRP and GNU Radio respectively. For researchers, this approach has opened the door to extend their studies in simulation domain into experimental domain. However, the realization of SDR concept is inherently limited by the analog components of the hardware being used. Despite that, the implementation of SDR is still new yet progressing, thus, this paper intends to provide an insight about its viability as a high re-configurable platform for communication system. This paper presents the SDR-based transceiver of common digital modulation system by means of GNU Radio and USRP.

Mutual impedance with finite feed gap model of dipole antennas using the induced EMF method

Mutual coupling in antenna arrays bring a significant impact especially when antenna elements are placed close with each other. It affects antenna performance, communication capacity and so on. Likewise, an accurate analysis of mutual coupling which can be expressed in terms of mutual impedance is important. A few analytic approaches for mutual impedance between two dipoles are available, one of it is the Induced EMF method. The Induced EMF method is accurate for short and thin, with an infinitesimal feed gap, which is impractical. A finite feed gap which is practical, can be modeled using electromagnetic simulation approaches. However, no analytical techniques are available to compare the results of the design with numerical software. The finite feed gap modelling of the mutual impedance using the Induced EMF method will be highlighted in this paper. The results are compared with other electromagnetic software. Then, the effect of the finite feed gap model has been observed in the far field pattern of dipole antenna arrays and they are in good agreement with other electromagnetic software.

Assessment of Conversion Methods to Acquire 1-Minute Integration Time Rain Intensity Statistic

This paper presents some preliminary findings of assessments carried out pertaining to the applicability of rain intensity conversion methods. Five conversion methods were identified in this study namely the ITU-R, Segal, Burgeuno, Chebil-Rahman and Khairolanuar et al. 1 year of rain intensity data were acquired from the Malaysian Meteorological Department (MMD) and utilized in the investigation. The research methodology involves productions of annual rain intensity cumulative distributions at 1-minute integration time using mentioned conversion methods. Predicted values established by ITU-R are used as benchmark. The values are then compared with values acquired using other conversion methods; in order to validate the applicability and effectiveness of each method. Based on the evaluation, it can be observed that the Khairolanuar et al. method seems to be a befitting conversion method and capable of generating values with smallest percentage difference.

Basic study of OFDM with multipath propagation model in GNU platform

Wireless communications technology is a vast and dynamic field of study. As such, high-reconfigurable tool like software defined radio is crucially needed. Software defined radio is a set of tool that consists of RF frond-end hardware and supported software like MATLAB, GNURadio, etc. For researcher, software defined radio is important to support the frequently change configurations and requirements of the studied system in real scenario as the inflicted cost and time consumed to re-configure the embedded system are significantly high. For instance, the endless demand for better quality and service of wireless communications leads to active research in current technology like OFDM. The way OFDM been implemented is vary from one application to the other, which required a high reconfigurable tool for real scenario experimentation and analysis. Thus, for knowledge enrichment, this paper intends to study the basic approach of OFDM by providing an insight of the system in multipath propagation channels. This paper is the first part of authors study whereas the simulation was implemented on GNU platform. The platform was used to model the OFDM system that based on both FFT and built-in GNURadio blocks, and the multipath propagation environment using the flat fading model. The observed signal constellations across the multipath models are consistent with the theoretical output, shows the reliability of GNU platform to deliver the OFDM system which will be used later for real transmission study.

Comparison of ITU-R predicted rainfall rates against measured data in Malaysia

This paper presents assessments of ITUs predicted rainfall intensities against measurements acquired from a campaign in Kuala Lumpur, Malaysia. Data for a period of twenty months were collected between 1996 and 1998. The statistical analyses involve generation of annual cumulative distributions. Predicted values generated using established ITU-R rainfall intensity prediction models are compared with measurements, in order to test the validity of each model. Based on the comparison between the available rainfall intensity models, it can be suggested that the locally measured rainfall intensity annual cumulative distribution falls within the ITU-R climatic zone P, as suggested by the earliest ITU-R P.837-1 recommendation.

Assessment of ITU-R predictions for Ku-Band rain attenuation in Malaysia

This paper presents findings on the assessments carried out pertaining to ITU-Rs predicted rain attenuations. The predictions are put against measurements acquired from a campaign in Kuala Lumpur, Malaysia. The investigation tasks involve generation of annual cumulative distributions using assorted ITU-R recommendations as well as from measured data collected for a period of 20 months. Predicted values generated using established ITU-R rain attenuation prediction models are then compared with measurements values, in order to validate the applicability and effectiveness of each model. Based on the evaluation, it can be suggested that the ITU-R P.618-5 recommendation seems to be a befitting prediction model and capable of generating satisfactory prediction for Malaysia.

Assessment of empirical conversion methods for producing 1-min integration time rainfall rate in Malaysia

This paper presents assessments of empirical conversion methods in obtaining cumulative distribution function of rainfall rate at 1-minute integration time. From collected measured data in Kuala Lumpur, cumulative distributions of rainfall rate at various integration times were compiled. Four conversion methods were selected in the assessment namely: Segal, Burgueno, Ismail et al and Polynomial. The generated 1-minute statistics using the mentioned four empirical conversion methods are then compared with measured statistics, in order to test its validity. Based on the assessment, it can be suggested that the Ismail et al and Polynomial conversion methods seem to be capable of producing rainfall rate statistics at 1-minute integration time with close approximation to the measured values.

Comparison of Radar Derived Rain Attenuation with the RazakSAT's X-Band Link Signal Measurement

Abstract—The preliminary analysis involving comparison between radar derived attenuation using an S-band meteorological radar and measured signal of RazakSAT’s X-band satellite link is presented. The radar data employed was attained from the Malaysian Meteorological Department’s (MMD) terminal Doppler weather radar installed strategically in the vicinity of Kuala Lumpur International Airport (KLIA). The X-band (8 GHz) satellite-Earth signals of Malaysian RazatSat’s collected at the National Space Agency (NSA) space center have been analyzed and studied. The vertical polarization S-band radar reflectivity information was used to calculate the likely rain attenuation along the RazakSAT satellite propagation paths. This was carried out by first converting the radar reflectivity values into rainfall rate using the established Z-R relations of Marshall-Palmer equation and, afterwards, by evaluating the slant path attenuation through the assimilation of the specific rain attenuation derived at the rainfall rate.