Alyani Ismail
UPM - Universiti Putra Malaysia, Faculty of Engineering, Faculty Member
Abstract We present a learning system that provides continuous self learning environment to the students. From the students' responses, this system is proven to provide better understanding and appreciation to the courses been... more
Abstract We present a learning system that provides continuous self learning environment to the students. From the students' responses, this system is proven to provide better understanding and appreciation to the courses been taught. Out of 60 students 71.7% admitted that this learning system has improved their study style and knowledge acquisition which then agreed to be implemented in future. The observation shows that this system increases the appreciation to the knowledge better than conventional method. Apart from ...
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The WiMAX mesh networks based on IEEE 802.16 standard is a key topology for the next generation wireless networking. However, interferences from transmission of the neighboring nodes within the mesh networks are inevitable. Cross-layer... more
The WiMAX mesh networks based on IEEE 802.16 standard is a key topology for the next generation wireless networking. However, interferences from transmission of the neighboring nodes within the mesh networks are inevitable. Cross-layer design for tree-type routing and level-based centralized scheduling is proposed as the optimization strategy. The cross-layer design here is relying on the routing information in network layer and centralized scheduling in the medium access control (MAC) layer. This paper proposes a centralized scheduling algorithm that can reduce interferences by constructing routing tree with multi-channel single transceiver system in WiMAX mesh networks. In this algorithm, each node has one transceiver that can be tuned to any of the channels, intending to eliminate the secondary interference. The results of analysis show that this proposed algorithm greatly improves the length of scheduling, channel utilization ratio (CUR) and throughput.
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Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for mobile satellite terminals. Determination... more
Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for mobile satellite terminals. Determination and quantification of these requirements are important to optimize service quality, particularly in the Malaysian region.Moreover, the tests on current satellite propagation models were carried out at temperate regions whose environmental characteristics are much different from those in Malaysia. This difference renders these propagation models inapplicable and irrelevant to tropical regions in general. This paper presents the link characteristics observations and performance analysis with propagation measurements done in tropical region to
provide an accurate database regarding rain and power arches supply (PAs) attenuations in the tropics for mobile scenarios. Hence, an extension for improving the performance assessment and analysis of satellite/transmission has been achieved. The Malaysia propagation measurement for mobile scenario (Malaysia-PMMS) enables first-hand coarse estimation and attenuation analysis, because the attenuation resulting from rain and PAs becomes easily amenable for measurement. Parallel to that, the measured attenuation has been compared with that of the simulated output at noise floor level.The underlying analytical tool is validated by measurements specific at tropical region, for dynamic model of mobile satellite links operating at higher than 10GHz.
provide an accurate database regarding rain and power arches supply (PAs) attenuations in the tropics for mobile scenarios. Hence, an extension for improving the performance assessment and analysis of satellite/transmission has been achieved. The Malaysia propagation measurement for mobile scenario (Malaysia-PMMS) enables first-hand coarse estimation and attenuation analysis, because the attenuation resulting from rain and PAs becomes easily amenable for measurement. Parallel to that, the measured attenuation has been compared with that of the simulated output at noise floor level.The underlying analytical tool is validated by measurements specific at tropical region, for dynamic model of mobile satellite links operating at higher than 10GHz.
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Recent advances in satellite to land mobile terminal services and technologies, which utilize high frequencies with directional antennas, have made the design of an appropriate model for land mobile satellite (LMS) channels a necessity.... more
Recent advances in satellite to land mobile terminal services and technologies, which utilize high frequencies with directional antennas, have made the design of an appropriate model for land mobile satellite (LMS) channels a necessity. This paper presents LMS channel model at Ku-band with features that enhance accuracy, comprehensiveness, and reliability. The effect of satellite tracking loss at different mobile terminal speeds is considered for directional mobile antenna systems, a reliable tropospheric scintillation model for an LMS scenario at tropical and temperate regions is presented, and finally a new quality indicator module for different modulation and coding schemes is included. The proposedextended LMS channel (ELMSC)model is designed based on actual experimental measurements and can be applied to narrow- and wide-band signals at different regions and at different speeds and multichannel states. The proposed model exhibits lower root mean square error (RMSE) and signific...
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A negative index metamaterial antenna is presented in this paper for ultra-wideband (UWB) applications; which operates in C and X-bands. The proposed antenna is composed of three-unit cells of left-handed metamaterial (LHM) where these... more
A negative index metamaterial antenna is presented in this paper for ultra-wideband (UWB) applications; which operates in C and X-bands. The proposed antenna is composed of three-unit cells of left-handed metamaterial (LHM) where these LHM unit cells are composed of a combination of modified octagonal spiral resonator (OSR), octagonal split-ring resonator (OSRR), capacitance-loaded strip (CLS), and wire that exhibit negative
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This paper presents a designed notched band ultra-wideband (UWB) printed antenna using coplanar waveguide-fed configuration. Simple technique of perforating the substrate and modifying the ground plane and radiator patch was used to... more
This paper presents a designed notched band ultra-wideband (UWB) printed antenna using coplanar waveguide-fed configuration. Simple technique of perforating the substrate and modifying the ground plane and radiator patch was used to achieve UWB for the designed antenna at smaller structure. Narrow arch-shaped slot was introduced to the patch of the proposed antenna to obtain the band rejection function around the 5.4 GHz frequency to avoid the interference with WLAN applications. The proposed antenna was fabricated and the measurement result is found in well agreement with the simulation result. In addition to the acquirable UWB bandwidth, the designed antenna is capable to exhibit high radiation efficiency and omni-directional pattern.
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ABSTRACT A comparative analysis of defected microstrip structure (DMS) with band-reject characteristic and high-Q is presented in this paper. This paper studies the parametric analysis on the different structure of DMS that consists of... more
ABSTRACT A comparative analysis of defected microstrip structure (DMS) with band-reject characteristic and high-Q is presented in this paper. This paper studies the parametric analysis on the different structure of DMS that consists of different length and width in order to produce good band-reject response at resonant of approximately 5.2 GHz. These types of structures are designed and simulated on Roger Duroid RO4350 with a dielectric constant, εr of 3.48 and a thickness of 0.508 mm. The optimum topology of DMS with Hashtag-shape exhibits high selectivity, sharp response as well as high attenuation in the stopband. The simulation performance results show good and promising results with high Q-factor and narrow bandwidth, and therefore could be further examined in future works during experimental works. This structure of DMS is useful for microwave applications when the undesired signals need to be removed such as in wideband systems.
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Cloud impairments have significant effect on signal propagated in the satellite to land stationary terminals channel at frequencies above 10 GHz. With the recent satellite to land mobile terminals network technologies and services that... more
Cloud impairments have significant effect on signal propagated in the satellite to land stationary terminals channel at frequencies above 10 GHz. With the recent satellite to land mobile terminals network technologies and services that use these frequencies, there is a lack of channel impairments modeling and analysis for such type of link. This study presents a reliable channel model of satellite-to-land mobile terminals that consider dynamic cloudy weather impairments. The cloud’s dynamic parameters and their effect on the Rician factor are modeled. The model involves modules that design multipath signals, direct clear line-of-sight (LOS) normalized signals, and cloud impairments. Results show that a considerable change occurs in the performance of the signal propagated through the cloud. The change appears as deviations in the fade depth and the variance of the propagated signal in the link between the satellite and the land mobile terminals. The channel model is a realistic approach to the link characteristics, which satellite systems designers should consider when designing high data rate satellite systems.
Research Interests: Atmospheric Modeling, Radio Channel Modelling, Satellite Communications, Satellite Communication, Channel Estimation, and 6 moreWireless Channel Modeling, Wave propagation, Atmospheric Effect on Electromagnetics Wave Propagation, Mobile and Satellite Communication, Land Mobile Satellite Communication, and Cloud attenuation
In the last few years, demand for high speed internet access service has increased greatly so the IEEE 802.16 working group on broadband wireless access (BWA) is developing the worldwide interoperability for microwave access (WiMAX)... more
In the last few years, demand for high speed internet access service has increased greatly so the IEEE 802.16 working group on broadband wireless access (BWA) is developing the worldwide interoperability for microwave access (WiMAX) standard for wireless metropolitan area networks (MANs) which aims to provide broadband wireless last mile access, easy deployment, and high speed data rate for large
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Abstract A multi-standard multi-band SDR baseband platform digital transceiver is proposed in this paper, where two different multi access techniques have been used. This paper also focuses on the methods to generate VHDL models of... more
Abstract A multi-standard multi-band SDR baseband platform digital transceiver is proposed in this paper, where two different multi access techniques have been used. This paper also focuses on the methods to generate VHDL models of communication systems that can be ...
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Abstract The WiMAX mesh networks based on IEEE 802.16 standard is a key topology for the next generation wireless networking. However, interferences from transmission of the neighboring nodes within the mesh networks are inevitable.... more
Abstract The WiMAX mesh networks based on IEEE 802.16 standard is a key topology for the next generation wireless networking. However, interferences from transmission of the neighboring nodes within the mesh networks are inevitable. Cross-layer design for tree-type routing ...
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Planning of energy-efficient protocols is critical for wireless sensor networks (WSNs) because of the constraints on sensor node's energy. Therefore, the routing protocol should be able to achieve uniform power dissipation during... more
Planning of energy-efficient protocols is critical for wireless sensor networks (WSNs) because of the constraints on sensor node's energy. Therefore, the routing protocol should be able to achieve uniform power dissipation during transmission to the sink node. In this paper, we present a self-optimization scheme for WSN which is able to utilize and optimize the sensor nodes' resources, especially the
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Abstract - In this paper, a compact 5 poles Ultra-Wideband (UWB) microwave filter is designed by using a quarter wave short-circuited stubs. The UWB filter bandwidth is covered from 2.75 GHz to 10.0 GHz. This filter designed is developed... more
Abstract - In this paper, a compact 5 poles Ultra-Wideband (UWB) microwave filter is designed by using a quarter wave short-circuited stubs. The UWB filter bandwidth is covered from 2.75 GHz to 10.0 GHz. This filter designed is developed from a Low Pass Chebychev prototype ...
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ABSTRACT An inductively coupled feed novel technique is proposed to enhance the performance of radio frequency identification tag antennas. The applied feeding concept is comprised of two opposing symmetrical U-shaped structures to feed a... more
ABSTRACT An inductively coupled feed novel technique is proposed to enhance the performance of radio frequency identification tag antennas. The applied feeding concept is comprised of two opposing symmetrical U-shaped structures to feed a radiating body. It is a simple alternative to effectively match the antenna impedance with the chip impedance from the flexible augmentation of equivalent inductance to the radiating body. The proposed feeding method offers better expectation of performance among antenna size, impedance, and gain at the size of 50 × 70 × 1.6 mm3. The peak gain of the proposed tag antenna is 2.5 dBi at its operating frequency, which is higher among conventional tag antennas. Measured results indicated that this tag antenna has a good impedance matching characteristic at 904–937 MHz (power reflection coefficient lower than −3 dB). The comparison between the simulation and measurement results verified the proposed technique's capability to improve overall performance of the tag antennas.
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Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for fixed and mobile satellite terminals. Due... more
Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for fixed and mobile satellite terminals. Due to lack of reliable investigations regarding accurate performance evaluation, experiments, and analysis on the satellite communication link in tropical regions under atmospheric impairments for both scenarios, accurate signal quality performance analysis is necessary. This paper presents the link characteristics observations and performance analysis with propagation measurements done in tropical region to provide an accurate database regarding rain attenuation in the tropics for fixed and mobile scenarios. The paper also presents a newly developed extension attached to the measurements setup for improved packet error rate (PER) performance evaluation related to the degradation's occur in channel quality for different types of impairments (rain, mobility, and physical obstacles) for 4 modulation schemes, namely QPSK, 8-PSK, 16-QAM and 32-QAM. The results show that the rain impairments at Ku band cause up to 12.5 dB and 23 dB at 77.5 and 40.1 elevation angles respectively in two tropical regions inside Malaysia for fixed scenario with a significant increase in PER at higher M-ary modulation schemes. For mobile scenario the PER appeared at higher M-ary scheme due to the lower signal power degradation in which, in turn, exceeded 1 dB when the vehicle speed exceed 100 km/hr
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ABSTRACT In general, a classical Split Ring Resonator (SRR) structure exhibits high Q-factor based on deeper and sharper transmission dips at resonance as well as produce high electric field density at the gaps. It is believed, by... more
ABSTRACT In general, a classical Split Ring Resonator (SRR) structure exhibits high Q-factor based on deeper and sharper transmission dips at resonance as well as produce high electric field density at the gaps. It is believed, by introducing more gaps, a strong and localized E-field will be obtained in the area between the split gaps. Based on these features, three types of rectangular multiple Split Ring Resonators (SRRs) were proposed to resonate in the frequency range of 3–7 GHz and simulated using Computer Simulation Technology (CST) Microwave Studio to determine the transmission characteristics and the resonance frequency. A Nicolson-Ross-Weir (NRW) technique is used to retrieve the effective parameters from the resultant S-parameter. It is shown that the resonance frequency of investigated structures falls in a frequency region in which the real part of permeability is negative. Later, the simulated results were investigated and the performances as well as the size of each unit cell itself were compared. Simulation for three different type of dielectric samples were also presented to demonstrate that the proposed structure may be well suited for bio-sensing.
ABSTRACT This paper proposes miniature radio frequency identification (RFID) tag antenna designed to operate on metallic objects, in the UHF frequency range (915 MHz). The antenna structure is comprised of two parts: Part 1 with two... more
ABSTRACT This paper proposes miniature radio frequency identification (RFID) tag antenna designed to operate on metallic objects, in the UHF frequency range (915 MHz). The antenna structure is comprised of two parts: Part 1 with two layers; a top layer of two square fractal patches electrically connected to the ground plane (bottom layer) through vias while Part 2 is an unconnected inter-layer consisting of two square complementary split ring resonators to allow for capacitive reactance increase. Consequently, the antenna resonant frequency is lowered, which theoretically allows shrinking RFID tag antenna into smaller size. The antenna was simulated and measured to verify its conjugate matching with chip impedance. The results of experimental tests showed that the proposed RFID tag offers a maximum read range of 0.48 m when placed on a metallic object. The tag's overall size is 36.7×18.1×3.2 mm3. Both simulation and measurement results are provided to validate the design.
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These days, there is a very large demand for wireless applications. Antennas which are used in these applications require being low profile, light weight, easily mounted and broad bandwidth. The microstrip antenna suits the features... more
These days, there is a very large demand for wireless applications. Antennas which are used in these applications require being low profile, light weight, easily mounted and broad bandwidth. The microstrip antenna suits the features mentioned except for its narrow bandwidth, typically from less than 1% to several percent. This paper introduces an alternative approach in enhancing the bandwidth of
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This paper presents an Ultra-Wide Band (UWB) microstrip filter which is initially modeled from a quarter-wavelength short-circuited stubs, without the use of any vias. All vias that provide short circuit stubs are replaced by microstrip... more
This paper presents an Ultra-Wide Band (UWB) microstrip filter which is initially modeled from a quarter-wavelength short-circuited stubs, without the use of any vias. All vias that provide short circuit stubs are replaced by microstrip patches which have low impedance at high ...
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Atmospheric condition variations were shown to have a major effect on the earth sky signal quality at Ku band. Moreover, such variations increased in the tropical regions as compared to temperate areas due to their different weather... more
Atmospheric condition variations were shown to have a major effect on the earth sky signal quality at Ku band. Moreover, such variations increased in the tropical regions as compared to temperate areas due to their different weather parameters. With the increase of recent satellite communication technology applications throughout the tropical countries and lack of information regarding the atmospheric impairments analysis, simulation and mitigation techniques, there is an ever increasing need for extracting a unique and accurate performance of the signal quality effects during highly natural tropical weather impairments. This paper presents a new method developed for proper analysis with distinctive and highly realistic performance evaluation for signal quality during the atmospheric conditions variations in 14 tropical areas from the four continents analyzed based on actual measured parameters. The method implementation includes signal attenuation, carrier to noise ratio, symbol energy to noise ratio, and symbol error rate at different areas and different modulation schemes. Furthermore, for improvement in analysis in terms of covering more remarkable regions in tropics, the paper provides new measurements data with analysis for certain region in tropics used as a test bed and to add measurement data of such area to the world's data base for future researchers. The results show a significant investigation and performance observation in terms of weather impairments in tropical regions in general and each region in that area in particular regarding the signal attenuation and error rates accompanied for several transmission schemes.
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Abstract. Future wireless access networks will be heterogeneous wireless network (HWN) environment which consists of various wireless technologies including universal mobile telecommunications system (UMTS) networks and wireless local... more
Abstract. Future wireless access networks will be heterogeneous wireless network (HWN) environment which consists of various wireless technologies including universal mobile telecommunications system (UMTS) networks and wireless local area networks (WLAN). They are used ...
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A radar system for detecting and localizing small targets on the ground is proposed in this paper. The system transmits wideband Linear Frequency Modulated pulses from ground-based transmitter. The reflected pulses will be collected... more
A radar system for detecting and localizing small targets on the ground is proposed in this paper. The system transmits wideband Linear Frequency Modulated pulses from ground-based transmitter. The reflected pulses will be collected simultaneously by two different ground-based receivers installed in different bistatic positions. Accurate range processing in this bistatic configuration will lead us to detect small objects like
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ABSTRACT An accurate, contactless and nondestructive method has been developed to characterize the rheological properties of asphalt (bitumen) by applying microwave techniques. The measured microwave parameters can be related to material... more
ABSTRACT An accurate, contactless and nondestructive method has been developed to characterize the rheological properties of asphalt (bitumen) by applying microwave techniques. The measured microwave parameters can be related to material parameters because microwaves are affected by means of wave transmission through the asphalt medium. In lossless and lossy dielectrics, diverse properties such as porosity, material composition, uniformity of the material, delamination of layers, moisture and contamination content and many other properties can be measured by suitable modeling and calibration of the measuring techniques. Microwave parameters can be correlated with conventional testing and the Strategic Highway and Research Program (SHRP) standard. Preliminary test results indicate a good correlation with material properties. Conventional methods, which are time consuming, costly and empirical, could be replaced by this new microwave method. This would bring about a revolutionary change in the highways and transportation sector worldwide.