Islam Md. Rafiqul

Environmental effects on free space earth-to-satellite optical link based on measurement data in Malaysia

FSO is a developing technology that has a great chance to compliment the traditional wireless communications and offer some inherent advantages compared to microwave links due to transmitting higher speed of data, easily deployment, and no license spectrum required. However, FSO is very vulnerable to the climatological phenomena such as fog, snow, rain, and haze that reduce the link availability. Most researches and studies are focusing on improving the FSO system for terrestrial link based on data in temperate region. Therefore, this paper is aiming to provide the feasibility analysis on performing FSO from earth to satellite in Malaysia as the performance of FSO is dependent on local weather conditions and in tropical region, the attenuations are dominant by rain and haze. The analysis is based on measurement of rain intensity, visibility and variation of optical free space signal level which has been done at Faculty of Engineering, International Islamic University (IIUM) Kuala Lumpur campus. From the terrestrial data, it will be scaled up for earth to satellite especially Low Earth Orbit (LEO) satellite and will be compared with calculated of FSO earth-to-satellite data. The analysis will determine the operability of FSO for long distance and as a benchmark for future design.

Effects of rain intensity variation on rain attenuation prediction for Free Space Optics (FSO) links

Free Space Optics (FSO) link have capabilities of providing optical communications similar to fiber optics based communications. However, the operational status of an FSO link is highly weather dependent which hampered the FSO link with feasibility issue. Among the major effect on FSO links under local weather condition is due to attenuation of heavy rainfall. Attenuation due to rainfall can restrict the path length of communication systems at frequencies above 10 GHz. The studies on the effect of rain intensity variation have been proposed by many models based on the radio wave propagation at centimeter or millimeter wavelength. Among the models are Lin Model, Moupfouma Model, Assis Model, Dissanayake and Allnutt Model, ITU Model, Abdulrahman Model and Silva Mello Model. The objective of this research to investigate the effect of rain intensity variation on the rain attenuation prediction for FSO links.

U-Slot Rectangular Patch Antenna for Dual Band Application

Dual and multi-band rectangular microstrip antennas can be realized by cutting U-slots inside the patch. In this paper, the length and width of U-slots are optimized in order to achieve dual-band and multi-band operation. Computer Simulation Technology (CST) software was used to design, simulate and optimization of antenna. Two resonant frequencies at 1.8 and 2.4 GHz were found with reasonable gain. Additional resonant frequencies could also be achieved from 2.8 to 3.0 GHz using the similar approach.

Preliminary Analysis of Dust Effects on Microwave Propagation Measured in Sudan

Dust storms are meteorological phenomena which occur for a percentage of time in arid and semi arid areas especially at African Sahara and Middle East. Measurements at existing microwave links have showed dust storms can potentially result in serious attenuation in signal level especially at Ku band and higher frequencies with direct impact on telecommunications system performance. Only a limited amount of research has been carried out and the available data was very scarce. Few prediction models have been developed to estimate microwave signal attenuation during the dust storm based on scattering theory and approximation of dust properties. However, real dust storm is a complex phenomenon which is difficult to be described by theoretical physical or mathematical models [5–6]. In this paper, an evaluation of the existing attenuation prediction models has been done based on the measured dust storm properties and measured attenuation in Sudan.

Propagation studies on rain for 5.8 GHz and 23 GHz point to point terrestrial link

The radio waves propagating through the earth atmosphere will be attenuated due to the presence of atmosphere particles, such as water vapor, water drops and the ice particles. The atmospheric gases and rain will both absorb and scatter the radio waves, and consequently degrade the performance of the link. Rain is a major source of attenuation for microwave propagation above 7 GHz. In tropical and equatorial regions, the rain intensity is higher and designing terrestrial and earth-to-satellite microwave links are very critical and challenging for high frequencies. This paper presents the summary of rain effects studies for lower operating frequency such as C band compare to higher operating frequency such as Ka band in tropical environment. The main objective to justified the literature findings on the effect of rain at lower and higher operating frequency in microwave link and solution to overcome it. An experimental test bed has been set up for 5.8 GHz and 23 GHz terrestrial point to point data communication link. The received signal strength (RSS) data and rain fall intensity data were recorded for 24 hours daily over period of 7 months (June 2011 - Dec 2011) at 1 minute interval. The collected rain rate data been analyzed with some prediction based on the results obtain. The main outcome of the research shows there is no effect of rain for 5.8 GHz link but there is strong effects with rain on the 23 GHz link. It was observed 15 dB to 35 dB attenuation during measurement period. This will be useful resources of information for researchers or telecommunication engineers, before implementation any mitigation method as a solution for point to point terrestrial link communication in future.

Analysis of Synthetic Storm Technique Based on Ku-Band Satellite Beacon Measurements in Malaysia

Most of the existing rain attenuation prediction models were proposed based on measurements taken in temperate climates. These models are found not accurate in tropical regions and were thus modified in order for such models to be applied in tropical regions. Synthetic Storm Technique (SST) is one of the most reliable methods to estimate rain attenuation time series in Europe. However, due to the lack of measured data in the tropical regions of the world, the above-mentioned method is yet to be validated for those regions. This paper aims to investigate SST validity in Malaysia by focusing on both rain events and the overall statistical behavior. Its performance is assessed based on concurrent measurement of Ku-band satellite beacon and rain rate over University of Science Malaysia (USM) campus at Tronoh. Preliminary analysis shows that SST is capable of providing details of time-series of many rain events to reflect the dynamics of rain fade. However, it is unable to predict the entire range of rain intensity.

Scintillation measurement on Ku-band satellite path in tropical climate

Scintillation data was collected in Kuala Lumpur, Malaysia for one year measurement. The data were obtained from MEASAT3 satellite operating at Ku-band with elevation angle of 77.4 . In this paper, scintillation statistics are analysed in dry (non-rain) condition. The scintillation distributions are represented scintillation intensity and amplitude by monthly, seasonal, worst-month and annual distributions. Probability density function (PDF) of scintillation intensity correspondingly agrees to Generalize Extreme Value (GEV) fit. In addition, model validation to the measured data is also provided.

Frequency diversity improvement factor for rain fade mitigation in Malaysia

Microwave communication systems in tropical region like Malaysia, operating at higher frequency ranges, are degraded its performance severely during rains. Hence, the rain fade must be taken in consideration for the MW link design to track the service outage and quality. This paper aims to develop and propose frequency diversity Improvement Factor prediction model for rain fade mitigation from 5-40 GHz. The rain attenuation is predicted based on ITU-R rain attenuation prediction method using measured rain rate in Malaysia. The predicted data are analysed to develop and propose a prediction for the improvement factor. The proposed improvement factor model is investigated according to the fade margin where the frequency separation is set to 5 GHz only.

Rain Rate Distributions for Microwave Link Design Based on Long Term Measurement in Malaysia

With the rapid growth of communications via the Internet, the need for an effective firewall system which has not badly affect the overall network performances has been increased. In this paper, a Field Programmable Gate Array (FPGA) -based firewall system with high performance has been implemented using Network FPGA (NetFPGA) with Xilinx Kintex-7 XC7K325T FPGA. Based on NetFPGA reference router project, a NetFPGA-based firewall system was implemented. The hardware module performs rule matching operation using content addressable memory (CAM) for higher speed data processing. To evaluate system performance, throughput, latency, and memory utilization were measured for different cases using different tools, also the number of rules that an incoming packet is subjected to was varied to get more readings using both software and hardware features. The results showed that the designed firewall system provides better performance than traditional firewalls. System throughput was doubled times of the one with Linux-Iptables firewalls.

Design of a Quintuple Band Microstrip Patch Antenna Using Multiple L-Slots

This paper proposes a simple approach to design microstrip patch antenna that can resonate at multiple frequency bands specifically at quintuple resonant frequencies. The antenna is designed to meet five frequency bands which are 0.9GHz, 1.8GHz, 2.1GHz, 2.45GHz and 2.8GHz. The microstrip patch antenna was designed to operate as dual band and a capital L-slot was introduced to design as triple band antenna. Subsequently by adding small l-slots enhanced antenna characteristics to quad band and quintuple bands. The approach is simple and the design of quintuple band antenna consists of a microstrip patch antenna with triple slots inserted on top of the radiating patch. The antenna is designed and simulated using CST Microwave studio. The proposed antenna was fabricated and tested using vector network analyzer. The test result is found close to that obtained by simulation.