- http://uumoptics.wix.com/uum-optics
- Universiti Utara Malaysia, Optics Lab, Department Memberadd
- Optical Waveguides, Optical Fiber Communications, Cross Layer Protocol/Application Design For Wireless Networks, Fiber Optic Sensors, Multiplexing Techniques, MIMO communication, and 23 moreTelecommunications, Optical Networking, Photonic Crystals, Nano Photonics And Nano Electronics, Electromagnetism, Applied Numerical Methods in Engineering, Nanophotonics, Applied Electromagnetics, Numerical Modelling, Computational Electromagnetics, Applied Mathematics, Optical fiber sensors, Engineering Science, Wireless Communications, Optics, Photonics, Wireless Sensor Networks, Electronic Engineering, Telecommunications Engineering, Electronics, Nanoscience, Nanotechnology, and Digital Holographyedit
- The Optical Technology Research Group led by Dr. Angela Amphawan focuses on ultra high-speed optical communications systems and optical sensor applications.edit
Research Interests: Electronic Engineering, Communication Engineering, Telecommunications Engineering, Optics, Optical Fiber Communications, and 21 moreFiber Optics, Photonic Crystals, Electronics, Computational Electromagnetics, Photonics, Nano Photonics And Nano Electronics, Optical Communication, Numerical Modelling, Adaptive Optics, Electromagnetics, Optical wireless Communications, Optical Waveguides, Silicon Photonics, Nano Technology, Optical computing, FTTH, WDM Optical Networks, Numerical Techniques In Electromagnetic, Photonics Computing, Angela Amphawan, and Dr. Angela Amphawan
Research Interests:
Radio-over-Free-Space-Optics (Ro-FSO) is a promising technology for future wireless networks. In this work, we have designed a hybrid orthogonal frequency division multiplexing (OFDM) Ro-FSO system for transmission of two independent... more
Radio-over-Free-Space-Optics (Ro-FSO) is a promising technology for future wireless networks. In this work, we have designed a hybrid orthogonal frequency division multiplexing (OFDM) Ro-FSO system for transmission of two independent channels by mode division multiplexing. Two independent 40 GHz radio signals are optically modulated at 20Gbps by mode division multiplexing of two laser modes LG00 and LG10 and transmitted over a free-space link of 20 km to 100 km. The performance of proposed Ro-FSO system is also evaluated under the effect of strong atmospheric turbulences
Research Interests:
Complementing wireless radio networks with free-space optics (FSO) achieves high data rates by modulating radio subcarriers over an optical carrier without expensive optical fiber cabling, enabling a pervasive platform for reaching... more
Complementing wireless radio networks with free-space optics (FSO) achieves high data rates by modulating radio subcarriers over an optical carrier without expensive optical fiber cabling, enabling a pervasive platform for reaching underserved areas. In this paper, we review the main features of FSO for terrestrial and inter-satellite communications. Simulations of 1 Gbps data transmission through FSO links in both terrestrial and inter-satellite communications have been investigated to highlight potential atmospheric challenges in FSO.
Research Interests:
Free space optics (FSO) technology provides a promising solution for future broadband networks, offering high data transmission compared to RF technology. This work is focused on investigating the performance of an FSO system with OFDM... more
Free space optics (FSO) technology provides a promising solution for future broadband networks, offering high data transmission compared to RF technology. This work is focused on investigating the performance of an FSO system with OFDM and QAM. A 10 Gbps data stream is transmitted using a 4-level QAM sequence through the FSO system under different atmospheric conditions. Results indicate that the integration of SOA prolongs the maximum achievable distance with acceptable SNR to 185 km under clear weather conditions whereas under atmospheric fog, the maximum distance is extended to 2.5 km
Research Interests: MIMO-OFDM systems, Free Space Optics, FREE SPACE OPTICAL COMMUNICATION, • Optical communication and free space optical communication (FSO), Free-Space Optical Communications and Optical Performance Modelling, and 3 moreWireless Communication, Free Space Optical Communication, Radio over Free Space Optics, and RoFSO
A six-channel 2.4GHz subcarrier multiplexing - optical code division multiple access (SCM-OCDMA) system in conjunction with the selective excitation of LP01 and LP02 modes is presented for a multimode fiber Local Area Network. Simulation... more
A six-channel 2.4GHz subcarrier multiplexing - optical code division multiple access (SCM-OCDMA) system in conjunction with the selective excitation of LP01 and LP02 modes is presented for a multimode fiber Local Area Network. Simulation results demonstrate that mode selectivity increases the bandwidth-distance product and improves the BER performance of the channel.
Research Interests:
Current computing trends such as cloud computing, file sharing and social networking promote collaboration and allow greater mobility for users. Nevertheless, these computing trends increase the vulnerability of networks to security... more
Current computing trends such as cloud computing,
file sharing and social networking promote collaboration and allow greater mobility for users. Nevertheless, these computing trends increase the vulnerability of networks to security threats and challenge network resources. An ingenious technique employed by attackers for retaining anonymity is by exploiting intermediary host computers or stepping stones to instigate attacks on other computers. This paper explores novel application of the stepping stone detection concept in addressing network threats such as spams, backdoors, proxy server intrusions and denial of service attacks. Preliminary stepping stone detection models for each security threat will be constructed and the potential detection process is delineated. These preliminary concepts and models may prove useful for further optimization of network security in conjunction with other conventional detection techniques.
file sharing and social networking promote collaboration and allow greater mobility for users. Nevertheless, these computing trends increase the vulnerability of networks to security threats and challenge network resources. An ingenious technique employed by attackers for retaining anonymity is by exploiting intermediary host computers or stepping stones to instigate attacks on other computers. This paper explores novel application of the stepping stone detection concept in addressing network threats such as spams, backdoors, proxy server intrusions and denial of service attacks. Preliminary stepping stone detection models for each security threat will be constructed and the potential detection process is delineated. These preliminary concepts and models may prove useful for further optimization of network security in conjunction with other conventional detection techniques.
Research Interests:
In this paper, we present a new alternative method for text steganalysis based on an evolution algorithm, implemented using the Java Evolution Algorithms Package (JEAP).The main objective of this paper is to detect the existence of hidden... more
In this paper, we present a new alternative method for text steganalysis based on an evolution algorithm, implemented using the Java Evolution Algorithms Package (JEAP).The main objective of this paper is to detect the existence of hidden messages ased on fitness values of a text description.It is found that the detection performance has been influenced by two groups of fitness values which are good fitness value and bad fitness value. This paper provides a valuable insight into the development and enhancement of the text steganalysis domain.
Research Interests:
Hospital network is evolving towards a more integrated approach by interconnecting wireless technologies into backbone networks. Although various integrated network scenarios have been published in the networking literature, a generic... more
Hospital network is evolving towards a more integrated approach by interconnecting wireless technologies into backbone networks. Although various integrated network scenarios have been published in the networking literature, a generic hospital model has not yet been fully explored and it remains a challenging topic in practice. One of the problems encountered by network practitioners is the seamless integration of network components into healthcare delivery. A good understanding of the performance of integrated networks is required for efficient design and deployment of such technologies in hospital environments. This research paper discuss on the modelling and evaluation of integrated network scenarios in hospital environments. The impact of traffic types (e.g. data, voice and video), traffic load, network size and signal strength on network performance is investigated by simulation. Three piloted case studies look at client performance in radiology Accident and Emergency (A & E and Intensive Care Unit (ICU)) scenarios. Each scenario reflects the need for various traffic types that end up distinct network behaviours. In the radiology scenario, email and File Transfer Protocol (FTP) traffic is found to perform well for medium-to-large networks. In the A & E scenario, Voice over Internet Protocol (VoIP) traffic is shown to generate very limited jitter and data loss. The performance is aligned with the Quality of Service (QoS) requirements. In the ICU scenario, the performance of video conference degrades with network size, thus, a QoS-enabled device is recommended to reduce the packet delay and data loss. IEEE 802.11a suits in hospital environment because it mitigates interference on the 2.4GHz band where most wireless devices operate.
Research Interests:
For the past ten years, heterogeneous networks wired and wireless had tended to integrate seamlessly, offering effective and reliable service for medical operations. One of the problems encountered by network practitioners is the... more
For the past ten years, heterogeneous networks wired and wireless had tended to integrate seamlessly, offering
effective and reliable service for medical operations. One of the problems encountered by network practitioners is the seamless integration of network components into healthcare delivery. As a multiplexing hospital model, the implementation certainly presents some challenges. The major technical and performance issues involve are as following. The operating parameters should keep aligned to the Quality of Service (QoS) requirement throughout simulation. Bandwidth utilisation of wireless networking is a challenging issue for real-time multimedia transmission. IEEE 802.11 provides relatively lower data rate than wired networks, thus the developer tends to adopt a more compromised solution: either reduce the file size or compress the image packets. Communication performance that varies constantly with the impact of signal strength, traffic load and interference. As stated radio signal senses as a curve and attenuates greatly while metallic object and
microwave exist within the active range. To ensure devices do not interfere with other electronic equipments (e.g. heart monitors), assert wireless spectrum has to be managed appropriately. This research paper aims to develop a generic hospital network scenarios using Wireless Local Area Network (WLAN) over OPNET Simulation, to evaluate the performance of the integrated network scenario for Intensive Care Units (ICU). This research makes use of computer simulation and discusses various aspects of the network design, so as to discover the performance behaviour pertaining to effect of traffic type, traffic load and network size. In the ICU scenario, the performance of video conference degrades with network size, thus, a QoS-enabled device is recommended to reduce the packet delay and data loss. IEEE 802.11a suits in hospital environment because it mitigates interference on the 2.4GHz band where most wireless devices operate. Experiment examines the effect of signal strength in WLAN. It is convinced that -88dBm is the best signal strength threshold. Although 802.11a generates slightly lower throughput than 802.11g, this issues can be addressed by placing more APs in the service area. It is convinced that 802.11a suits the hospital environments, because it mitigates interference on the popular 2.4GHz band where most wireless devices operate. It is important for medical devices which require future upgrade and Bluetooth deployment.
effective and reliable service for medical operations. One of the problems encountered by network practitioners is the seamless integration of network components into healthcare delivery. As a multiplexing hospital model, the implementation certainly presents some challenges. The major technical and performance issues involve are as following. The operating parameters should keep aligned to the Quality of Service (QoS) requirement throughout simulation. Bandwidth utilisation of wireless networking is a challenging issue for real-time multimedia transmission. IEEE 802.11 provides relatively lower data rate than wired networks, thus the developer tends to adopt a more compromised solution: either reduce the file size or compress the image packets. Communication performance that varies constantly with the impact of signal strength, traffic load and interference. As stated radio signal senses as a curve and attenuates greatly while metallic object and
microwave exist within the active range. To ensure devices do not interfere with other electronic equipments (e.g. heart monitors), assert wireless spectrum has to be managed appropriately. This research paper aims to develop a generic hospital network scenarios using Wireless Local Area Network (WLAN) over OPNET Simulation, to evaluate the performance of the integrated network scenario for Intensive Care Units (ICU). This research makes use of computer simulation and discusses various aspects of the network design, so as to discover the performance behaviour pertaining to effect of traffic type, traffic load and network size. In the ICU scenario, the performance of video conference degrades with network size, thus, a QoS-enabled device is recommended to reduce the packet delay and data loss. IEEE 802.11a suits in hospital environment because it mitigates interference on the 2.4GHz band where most wireless devices operate. Experiment examines the effect of signal strength in WLAN. It is convinced that -88dBm is the best signal strength threshold. Although 802.11a generates slightly lower throughput than 802.11g, this issues can be addressed by placing more APs in the service area. It is convinced that 802.11a suits the hospital environments, because it mitigates interference on the popular 2.4GHz band where most wireless devices operate. It is important for medical devices which require future upgrade and Bluetooth deployment.
Research Interests:
Pervasive computing devices are configured for anywhere at any time services to adapt the changes in the dynamic environment with respect to the user mobility. The paper proposes a salient model for a log based anonymity handling in... more
Pervasive computing devices are configured for anywhere at any time services to adapt the changes in the dynamic
environment with respect to the user mobility. The paper proposes a salient model for a log based anonymity handling
in pervasive networks. The model defines a resource registry and sensor object modeling. Associability between the
nodes are configured with an allied user interface in the environment. Resource registry refers to a record of
information about the sensor nodes. A log book is maintained to keep track of the service discovery issues. New device
enquiry, registration and adaption are major issues in such pervasive devices. These issues lead to unacknowledged
communication that causes anonymity. This paper defines and discusses the presence of anonymity in pervasive
environments due to aforementioned issues.
environment with respect to the user mobility. The paper proposes a salient model for a log based anonymity handling
in pervasive networks. The model defines a resource registry and sensor object modeling. Associability between the
nodes are configured with an allied user interface in the environment. Resource registry refers to a record of
information about the sensor nodes. A log book is maintained to keep track of the service discovery issues. New device
enquiry, registration and adaption are major issues in such pervasive devices. These issues lead to unacknowledged
communication that causes anonymity. This paper defines and discusses the presence of anonymity in pervasive
environments due to aforementioned issues.
Research Interests: Pervasive Computing, Middleware, Mobile and Pervasive Computing, Web service discovery, Service Discovery and Provisioning, and 5 morePervasive and Ubiquitous Computing, Middleware Technology (Intelligent Middleware), SERVICE DISCOVERY IN ADHOC NETWORKS, Anonimity, and Service Oriented Architecture, Service Discovery, Ontology
This paper examines the avalanche photodiode (APD) gain impact on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems based single photodiode detection (SPD) technique. Numerical results are used for... more
This paper examines the avalanche photodiode (APD) gain impact on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems based single photodiode detection (SPD) technique. Numerical results are used for inspecting the APD gain influence upon the probability density function (PDF) and signal-to-noise ratio (SNR) performance. The usage of APD over positive-intrinsic-negative (PIN) photodiode accommodates more users with improved PDF and higher SNR.
Research Interests:
To address the overwhelming bandwidth increase in premise backbones, an attractive alternative for selective mode excitation in multimode fiber (MMF) using solid-core photonic crystal fiber (PCF) is presented. The power coupling... more
To address the overwhelming bandwidth increase in premise backbones, an attractive alternative for selective mode excitation in multimode fiber (MMF) using solid-core photonic crystal fiber (PCF) is presented. The power coupling efficiency, differential mode delay, and bit-error rate performance of several structural designs of solid-core PCF waveguides are investigated for the selective excitation of mode LP01 in a MMF. The achieved coupling efficiency into mode LP01 is above 90% for PCF profiles with seven rings.
Research Interests:
The integration of heterogeneous technologies promotes ubiquity and mobility. Optical code division multiple access (OCDMA) may be deployed in conjunction to SCM to improve the spectral efficiency and enhance the data rate of subscribers... more
The integration of heterogeneous technologies promotes ubiquity and mobility. Optical code division multiple access (OCDMA) may be deployed in conjunction to SCM to improve the spectral efficiency and enhance the data rate of subscribers in a Local Area Network (LAN). This paper compares the performance of multimode fiber to single mode fiber in the deployment of a SCM-OCDMA system with multi-diagonal (MD) codes in a LAN.
Research Interests:
To address the overwhelming bandwidth increase in premise backbones, an attractive alternative for selective mode excitation in multimode fiber (MMF) using solid-core photonic crystal fiber (PCF) is presented. The power coupling... more
To address the overwhelming bandwidth increase in premise backbones, an attractive alternative for selective mode excitation in multimode fiber (MMF) using solid-core photonic crystal fiber (PCF) is presented. The power coupling efficiency, differential mode delay and bit-error rate performance of several structural designs of solid-core PCF waveguides are investigated for the selective excitation of mode LP01 in a MMF. The achieved coupling efficiency into mode LP01 is above 90% for PCF profiles with seven rings.
Research Interests:
This paper investigates the avalanche photodiode (APD) gain effect on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a modified-AND subtraction detection in comparison to the conventional AND... more
This paper investigates the avalanche photodiode (APD) gain effect on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a modified-AND subtraction detection in comparison to the conventional AND detection scheme. Analytical results are presented to investigate the APD gain impact on the bit-error rate (BER) performance. In addition, we confirm the influence of the APD over the positive-intrinsic-negative (PIN) photodiode on the system performance using data transmission simulations.
Research Interests:
The demand for efficient optical communication systems has fuelled considerable research in developing techniques for eradicating phase-induced intensity noise (PIIN) in spectral-amplitude coding optical code-division multiple-access... more
The demand for efficient optical communication systems has fuelled considerable research in developing techniques for eradicating phase-induced intensity noise (PIIN) in spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA). This paper investigates the use of modified-AND subtraction detection technique to mitigate PIIN in SAC-OCDMA systems. The simulation results show that the modified-AND subtraction detection demonstrates better performance over the conventional AND detection approach. Furthermore, we have found that, from a transmission length of 40 km onwards, group velocity dispersion (GVD) degrades SAC-OCDMA system performance apparently. Dispersion compensating fiber (DCF) is used to lessen the influence of GVD caused by single mode fiber (SMF).
Research Interests:
In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN)... more
In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN) and multiple-access interference (MAI) in the optical domain. Analytical results show that for 35 simultaneous users transmitting at data rate of 622 Mbps, the bit-error rate (BER) = 1.4x10^-28 for SPD technique is much better compared to 9.3x10^-6 and 9.6x10^-3 for the modified-AND as well as the AND detection techniques, respectively. Moreover, we verified the improved performance afforded by the proposed technique using data transmission simulations
Research Interests:
This letter presents a single photodiode detection (SPD) as an effective technique for eradicating both multiple-access interference (MAI) and phase-induced intensity noise (PIIN) in spectral amplitude coding optical code-division... more
This letter presents a single photodiode detection (SPD) as an effective technique for eradicating both multiple-access interference (MAI) and phase-induced intensity noise (PIIN) in spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. Mathematical analysis and simulation experiments are used to investigate the spectral efficiency (SE) of SAC-OCDMA systems utilizing different detection techniques. Results show that the SPD technique significantly enhances the SE compared to AND as well as modified-AND subtraction detections.
Research Interests:
Free Space Optics Systems (FSO) is one of the most effective solutions, especially for atmospheric turbulence due to the weather and environment structure. Free space optics system suffers from various limitations. A well-known... more
Free Space Optics Systems (FSO) is one of the most effective solutions, especially for atmospheric turbulence due to the weather and environment structure. Free space optics system suffers from various limitations. A well-known disadvantage of FSO is its sensitivity on local weather conditions-primarily to haze and rain, resulting in substantial loss of optical signal power over the communication path. The main objective of this article is to evaluate the quality of data transmission using Wavelength Division Multiplexing (WDM) with highlighting several factors that will affect the quality of data transmission. The results of these analyses are to develop a system of quality-free space optics for a high data rate transmission. From the result analysis, FSO wavelength with 1550 nm produces less effect in atmospheric attenuation. Short link range between the transmitter and receiver can optimize the FSO system transmission parameters or components. Based on the analysis, it is recommended to develop an FSO system of 2.5 Gbps with 1550 nm wavelength and link range up to 150 km at the clear weather condition of bit-error-rate (BER) 10−9
Research Interests:
We report here for the first time the fabrication and characterization of mechanically induced ultralong period fiber gratings (MULPFG) with period size up to several millimeters. In these gratings the coupling of the fundamental guided... more
We report here for the first time the fabrication and characterization of mechanically induced ultralong period fiber gratings (MULPFG) with period size up to several millimeters. In these gratings the coupling of the fundamental guided core mode takes place with cladding modes of high diffraction orders.The transmission characteristic of grating with different external applied pressure has been experimentally verified.
Research Interests:
A new, robust Integrated Priority-Based Cell Attenuation Model for dynamic cell sizing is proposed and simulated using real mobile traffic data. The proposed model is an integration of two main components; the Modified Virtual... more
A new, robust Integrated Priority-Based Cell Attenuation Model for dynamic cell sizing is proposed and simulated using real mobile traffic data. The proposed model is an integration of two main components; the Modified Virtual Community–Parallel Genetic Algorithm (VC-PGA) Cell Priority Selection Module and the Evolving Fuzzy (EFuNN) Mobile Traffic Prediction Module. The VC-PGA Module controls the number of cell attenuations by ordering the priority for the attenuation of all cells based on the level of mobile level of mobile traffic within each cell. The EFuNN Module predicts the traffic volume of a particular cell by extracting and inserting meaningful rules through incremental, supervised real-time learning. The EFuNN Module is placed in each cell and the output, the predicted mobile traffic volume of the particular cell, is sent to Local and Virtual Community Servers in the VC-PGA Module. The VC-PGA Module then assigns priorities for the size attenuation of all cells within the network, based on the predicted mobile traffic levels from the EFuNN Module at each cell. The performance of the proposed Module was evaluated on five adjacent cells in Selangor, Malaysia. Real-time predicted mobile traffic from the EFuNN structure was used to control the size of all the cells. Results obtained demonstrate the robustness of the Integrated Module in recognizing the temporal pattern of the mobile traffic and dynamically controlling the cell size in order to reduce the number of calls dropped.
Research Interests: Wireless Communications, Radio Resource Management, Wireless Sensor Networks, Neural Networks, AdHoc Networks, and 12 moreWireless networks, Matlab, Genetic Algorithm, Beamforming, WSN (Wireless sensor network), Directional Antenna, Traffic Analysis and congestion control, Dynamic Cell Sizing, Data Traffic Control, Traffic Balancing, Evolving Fuzzy Neural Networks, and Mobile Traffic Data
This paper presents a qualitative, real-time backlighting positioning sensor for the alignment of an optical beam to a minutely deviated diffraction order axis to increase the power coupling efficiency into a multimode fiber in selective... more
This paper presents a qualitative, real-time backlighting positioning sensor for the alignment of an optical beam to a minutely deviated diffraction order axis to increase the power coupling efficiency into a multimode fiber in selective launches. Results show that the technique facilitates the alignment of the lenses to the first diffraction order axis and improves the power coupling efficiency into a multimode fiber.
Research Interests: Optical Fiber Communications, Digital Holography, Optimization (Mathematics), Optical Measurement Methods, Optical fiber sensors, and 13 moreComputer Generated Holograms, Self-collimation, photonic crystal, Optical cavity, Optical fiber sensor, Spatial Light Modulator, Diffraction, Power Coupling, SLM, Multimode Fibers, Fourier Optics, Power Coupling Efficiency, Selective Mode Excitation, Backlighting Sensor, and Diffraction Order
"In this paper, a cognitive radio based medium access control (CR-MAC) protocol for wireless sensor networks that utilizes cognitive radio transmission is used. In cognitive radio (CR) networks, identifying the available spectrum resource... more
"In this paper, a cognitive radio based medium access control (CR-MAC) protocol for wireless sensor networks that utilizes cognitive radio transmission is used. In cognitive radio (CR) networks, identifying the available spectrum resource through spectrum sensing, deciding on the optimal sensing and transmission times, and coordinating with the other users for spectrum access are the important functions of the medium access control (MAC) protocols. In this paper, the sensor nodes are classified into nodes of critical information, and nodes of non-critical information. The CR-MAC protocol prioritizes the critical packets access to the transmission medium by transmitting them with higher power while transmitting lower priority packets using lower transmission power. The network throughputs can be improved by increasing number of traffic rate, also the end-to-end delay will minimizes by CR-MAC protocol. And a motive to take advantage of heavy traffic rate which may occur at the receiver, a higher priority packet experience collision only when there are more than one critical packet transmission at the same time slot while non critical packets experience collision when there are more than one transmission at the same time slot.
Research Interests: Wireless Communications, Cognitive Radio Networks, Access Control, Wireless Sensor Networks, QoS for Wireless Sensor Networks, and 7 moreWireless networks, Wireless Networks (Computer Science), Spectrum Sensing, Medium Access Control protocols in WSN, Wireless, Medium Access Controls For Wireless Sensor Networks, and Medium Access Control
With rapidly growing bandwidth demands in Local Area Networks, it is imperative to support next generation speeds beyond 40Gbit/s. Various holographic optimization techniques using spatial light modulators have recently been explored for... more
With rapidly growing bandwidth demands in Local Area Networks, it is imperative to support next generation speeds beyond 40Gbit/s. Various holographic optimization techniques using spatial light modulators have recently been explored for adaptive channel impulse response improvement of MMF links. Most of these experiments are algorithmic-oriented. In this paper, a set of lenses and a spatial light modulator, acting as a binary amplitude filter, played the pivotal role in generating the input modal electric field into a graded-index MMF, rather than algorithms. By using a priori theoretical information to generate the incident modal electric field at the MMF, the bandwidth was increased by up to 3.4 times.
Note: This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the link to the OSA website provided below. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
Note: This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the link to the OSA website provided below. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
Research Interests: Optical Engineering, Optical Fiber Communications, Fiber Optics, Digital Holography, Photonics, and 26 moreOptical Communication, Modal Analysis, Biophotonics, Optical Measurements, Adaptive Optics, Fourier Analysis, Optoelectronics and Photonics, Spatial Light Modulator, Selective Launch, Offset Launch, Diffraction, Modal Multiplexing, SLM, Fourier transform, Bandwidth enhancement, Spatial Multiplexing, Multimode Fiber, Apriori Modal Field, Transverse Modal Field, Holographic Optimization, 100Gbps, Increase Bandwidth, Neurophotonics, Phase-only SLM, Phase Modulation, and Selective Mode Excitation
In this paper, spectrum pool is one of the efficient techniques for spectrum sensing selection. Cognitive radio always preferred for accessing free channels efficiently with minimum handoff delay . The performance of spectrum pool has... more
In this paper, spectrum pool is one of the efficient techniques for spectrum sensing selection. Cognitive radio always preferred for accessing free channels efficiently with minimum handoff delay . The performance of spectrum pool has been implemented and compared with conventional handoff mechanism. Spectrum handoff occurs when primary user appears and the secondary users using this particular licensed channel. This particular spectrum handoff would use channels for the handoff process from the spectrum pool formed by proposed method. Spectrum sensing plays important role in case of cognitive radio. For accessing the spectrum reuse functionality, secondary users used to sense the radio frequency environment. For this propose we proposed two different modules one is spectrum pool and other will be secondary user with multiple antennas.
Research Interests: Wireless Communications, Cognitive Radio Networks, Radio Resource Management, Access Control, Traffic control, and 12 moreMobile Computing, Spectrum Sensing, Wireless Computing, Wireless Networking, Medium Access Controls For Wireless Sensor Networks, Handoff, Dynamic Cell Sizing, Dynamic Cell Sizing, Dynamic Cell Sizing, Spectrum Pooling, Spectrum Handoff, and Spectrum Reuse
To boost the performance of spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems, the need for an effective solution to diminish phase-induced intensity noise (PIIN) is becoming progressively more crucial.... more
To boost the performance of spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems, the need for an effective solution to diminish phase-induced intensity noise (PIIN) is becoming progressively more crucial. In this letter, two PIIN suppression approaches: semiconductor optical amplifier (SOA)-based noise cleaning, and single photodiode detection (SPD) are employed. The performance of the hybrid SOA/SPD scheme is validated through simulation experiments. Our results show that SOA/SPD scheme remarkably improves the performance and increases the throughput of SAC-OCDMA system.
Research Interests: Optical Fiber Communications, MIMO Systems, SOA, Ocdma, Optical Code Division Multiple Access, and 12 moreSPD, SPD, SPD, SEMICONDUCTOR OPTICAL AMPLIFIER, Optical MIMO, Multi-channel optical transmission, COMIMO, OCDMA, CDMA, SAC-OCDMA, Single Photodide Detection, Phase-induced Intensity Noise Suprpression, Subtraction Detection, SOA/SPD, and Optisystem
"The demand for portable real-time optical applications such as medical optical sensors and optical transceivers instigate the need for compact optical designs. The aim of this paper is to demonstrate a new, compact design for binary... more
"The demand for portable real-time optical applications such as medical optical sensors and optical transceivers instigate the need for compact optical designs. The aim of this paper is to demonstrate a new, compact design for binary spatial amplitude modulation in a multimode fiber-based optical transceiver, adapted from microscopy. The continuous-amplitude transverse modal electric field of an infinite parabolic multimode fiber is retrieved from a binary amplitude-modulated field using a single lens. The retrieved field is in good agreement with the original modal electric field.
Note: This is an electronic version of an article published in the Journal of Modern Optics. The article is available online at: http://dx.doi.org/10.1080/09500340.2011.636486. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law."
Note: This is an electronic version of an article published in the Journal of Modern Optics. The article is available online at: http://dx.doi.org/10.1080/09500340.2011.636486. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law."
Research Interests:
The demand for higher bandwidth in local area networks (LANs) has fuelled considerable research in techniques for mitigating modal dispersion in multimode fiber (MMF). These techniques include selective mode excitation, offset launching,... more
The demand for higher bandwidth in local area networks (LANs) has fuelled considerable research in techniques for mitigating modal dispersion in multimode fiber (MMF). These techniques include selective mode excitation, offset launching, angular multiplexing and electronic dispersion compensation, all of which strive to optimize the channel impulse response of a MMF. To obtain the optimal bandwidth-enhancement results from these techniques, knowledge of the distribution of power coupling coefficients given an arbitrary offset launch in a MMF is important. In this paper, an analytical expression for the power coupling coefficient for an incident Gaussian beam launched with a radial offset into a MMF having an infinite parabolic refractive index profile is derived. This expression is useful in understanding the parameters which may affect the power coupling coefficient and how they may enhance the MMF bandwidth. The power coupling coefficients obtained from the derived analytical expression are compared with numerical results and are in excellent agreement. The analytical expression may be extended to manufactured MMF.
2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
Research Interests: Optics, Optical Fiber Communications, Fiber Optics, Photonics, Optical Communication, and 15 moreElectromagnetics, Optical Waveguides, Applied Electromagnetics, Spatial Mode Multiplexer/Demultiplexer Based on Tapered Hollow Waveguide, Local Area Networks, Selective Launch, Guided Waves, Optical Waveguide, Offset Launch, Power Coupling, Power Modal Coupling, Gaussian, Laguerre-Gaussian beams, Laguerre polynomial, and Linearly Polarized Modes
Current computing trends such as cloud computing, file sharing and social networking promote collaboration and allow greater mobility for users. Nevertheless, these computing trends increase the vulnerability of networks to security... more
Current computing trends such as cloud computing,
file sharing and social networking promote collaboration and allow greater mobility for users. Nevertheless, these computing trends increase the vulnerability of networks to security threats and challenge network resources. An ingenious technique employed by attackers for retaining anonymity is by exploiting intermediary host computers or stepping stones to instigate attacks on other computers.
This paper explores novel application of the stepping stone detection concept in addressing network threats such as spams, backdoors, proxy server intrusions and denial of service attacks. Preliminary stepping stone detection models for each security threat will be constructed and the potential detection process is delineated. These
preliminary concepts and models may prove useful for further optimization of network security in conjunction with other conventional detection techniques.
file sharing and social networking promote collaboration and allow greater mobility for users. Nevertheless, these computing trends increase the vulnerability of networks to security threats and challenge network resources. An ingenious technique employed by attackers for retaining anonymity is by exploiting intermediary host computers or stepping stones to instigate attacks on other computers.
This paper explores novel application of the stepping stone detection concept in addressing network threats such as spams, backdoors, proxy server intrusions and denial of service attacks. Preliminary stepping stone detection models for each security threat will be constructed and the potential detection process is delineated. These
preliminary concepts and models may prove useful for further optimization of network security in conjunction with other conventional detection techniques.
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The trend towards real-time optical applications predicates the need for real-time interferometry. For real-time interferometric applications, rapid processing of computer generated holograms is crucial as the intractability of rapid... more
The trend towards real-time optical applications predicates the need for real-time interferometry. For real-time interferometric applications, rapid processing of computer generated holograms is crucial as the intractability of rapid phase changes may compromise the input to the system. This paper introduces the design of a set of binary encoded computer generated holograms (CGHs) for real-time five-frame temporal phase shifting interferometry using a binary amplitude spatial light modulator. It is suitable for portable devices with constraints in computational power. The new set of binary encoded CGHs is used for measuring the phase of the generated electric field for a real-time selective launch in multimode fiber. The processing time for the new set of CGHs was reduced by up to 65% relative to the original encoding scheme. The results obtained from the new interferometric technique are in good agreement with the results obtained by phase shifting by means of a piezo-driven flat mirror.
Note: This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the link to the OSA website provided below. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.""
Note: This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the link to the OSA website provided below. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.""
Research Interests: Fiber Optics, Digital Holography, Biosensors, Optical Tomography, Optical Measurement Methods, and 20 moreFiber Optic Sensors, Holographic Interferometry, Adaptive Optics, Interferometry, Computer Generated Holograms, Spatial Light Modulator, CGH, Temporal Phase Shifting, Five Frame Phase Shifting, SLM, Laguerre-Gaussian beams, Computer Generated Hologram, Spatial Multiplexing, Digital Interferometry, Binary Amplitude Modulation, 5 Frame Phase Shifting, Piezo-Driven Mirror, Laguerre polynomial, Computer Generated Holography, and Selective Mode Excitation
The visualization of the modal electric field for an infinite parabolic multimode fiber may not be immediately intuitive due to the intricate nature of the Laguerre function. To capture the essence of the various properties of the... more
The visualization of the modal electric field for an infinite parabolic multimode fiber may not be immediately intuitive due to the intricate nature of the Laguerre function. To capture the essence of the various properties of the transverse modal electric field of the infinite parabolic multimode fiber, various simulations are drawn on and key observations are made.
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In this paper, we present a new alternative method for text steganalysis based on an evolution algorithm, implemented using the Java Evolution Algorithms Package (JEAP). The main objective of this paper is to detect the existence of... more
In this paper, we present a new alternative method for text steganalysis based on an evolution algorithm, implemented using the Java Evolution Algorithms Package (JEAP). The main objective of this paper is to detect the existence of hidden messages ased on fitness values of a text description. It is found that the detection performance has been influenced by two groups of fitness values which are good fitness value and bad fitness value. This paper provides a valuable insight into the development and enhancement of the text steganalysis domain.
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This study presents a new alternative of steganalysis method in order to detect hidden messages in text steganalysis called Evolution Detection Steganalysis System (EDSS) based on the evolution algorithm approach under Java Genetic... more
This study presents a new alternative of steganalysis method in order to detect hidden messages in text steganalysis called Evolution Detection Steganalysis System (EDSS) based on the evolution algorithm approach under Java Genetic Algorithms Package (JGAP). The result of the EDSS can be divided into two groups based on fitness values which are good fitness and bad fitness. Hopefully, this study can produce a good idea to other researchers for understanding the text steganalysis in order to develop a steganalysis system that can contribute a better performance in other domains.
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The success of optical multiple-input-multiple output (MIMO) systems in wireless communications has motivated interesting investigations of MIMO in optical fiber communications. This paper reviews various optical MIMO techniques in... more
The success of optical multiple-input-multiple output (MIMO) systems in wireless communications has motivated interesting investigations of MIMO in optical fiber communications. This paper reviews various optical MIMO techniques in multimode fiber.
Copyright 2011 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Copyright 2011 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Research Interests: Biosensors, Multi Antenna Multiple Access Techniques, Orthogonal Frequency Division Multiple Access (OFDMA), MIMO Systems, Radio over fiber, and 24 moreMIMO communication, Multiplexing Techniques, Optical MIMO, Multi-channel optical transmission, COMIMO, Modal Multiplexing, Dispersive Multiplexing, Modal Group Multiplexing, OCDMA, CDMA, Spatial Multiplexing, Performance analysis of diversity receivers over fading channels, COMIMO, Mode Division Mulitplexing, Mode Division Mulitplexing, Coherent Optical Muluiptle-input-muliple-output, Transmitter Diversity, Receiver Diversity, Receiver Diversity, Polarization Multiplexing, Few Mode Fiber, Mode Coverter, Berdague, Mode Division M,ultiplexing, Facq, Single Mode Fiber, and MIMO Single Mode Fiber
The development of many high bit-rate multimedia applications has emphasized the demand for service differentiation or prioritization techniques to ensure end-user quality-of-service (QoS) necessities. This paper focuses on utilizing... more
The development of many high bit-rate multimedia applications has emphasized the demand for service differentiation or prioritization techniques to ensure end-user quality-of-service (QoS) necessities. This paper focuses on utilizing different detection schemes in spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems to support 'triple-play' services (voice, video, and data) with diverse QoS requirements. The used subtraction detection techniques are complementary, AND, as well as modified-AND. Modified double-weight (MDW) codes are used as the signature codes for SAC-OCDMA systems. The simulation results show that modified-AND subtraction detection demonstrates better performance over other detection approaches.
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Voice over Internet Protocol (VoIP) technology has observed rapid growth in the world of telecommunications. VoIP offers high-rate voice services at low cost with good flexibility, typically in a Wireless Local Area Network (WLAN). In a... more
Voice over Internet Protocol (VoIP) technology has observed rapid growth in the world of telecommunications. VoIP offers high-rate voice services at low cost with good flexibility, typically in a Wireless Local Area Network (WLAN). In a voice conversation, each client works either as a sender or a receiver depending on the direction of traffic flow over the network. A VoIP technologically requires high throughput, less packet loss and a high fairness index over the network. The packets of VoIP streaming may experience drops because of competition among the different kinds of traffic flow over the network. A VoIP application is also sensitive to delays and requires voice packets to arrive on time from the sender to the receiver without any delay over a WLAN. To date, scheduling of VoIP traffic is still an unresolved problem. The objectives of this survey paper to discuss fundamental principles of VoIP-related schedulers and identify current scheduler issues. This survey paper also identifies the importance of the scheduling techniques over WLANs. Related research work for real-time applications specifically for VoIP will also be highlighted.
Research Interests: Wireless Communications, Computer Networks, Voice over IP, Network Analysis, Packet scheduling, and 12 moreTraffic control, Wireless networks, Wireless Networks (Computer Science), Voip, wireless Local Area Networks, Web Traffic Analysis, Traffic Light Scheduling, Local Area Networks, Traffic Analysis and congestion control, Tokens, Voice Over Internet Protocol, and Credit-based
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The advent of realtime multimedia services over the Internet has stimulated new technologies for expanding the information carrying capacity of optical network backbones. Multilayer wavelength division multiplexing (WDM) packet switching... more
The advent of realtime multimedia services over the Internet has stimulated new technologies for expanding the information carrying capacity of optical network backbones. Multilayer wavelength division multiplexing (WDM) packet switching is an emerging technology for increasing the bandwidth of optical networks. Two algorithms for the routing of the multimedia traffic flows were applied: (i) Capacitated Shortest Path First (CSPF) routing, which minimizes the distance of each flow linking the given source and destination nodes and satisfying capacity constraints; and (ii) Flow Deviation Algorithm (FDA) routing, which minimizes the networkwide average packet delay.
Research Interests: Wireless Communications, Heuristics, Wireless Sensor Networks, Cross Layer Protocol/Application Design For Wireless Networks, Packet Switching, and 15 moreWireless networks, Mobile Computing, Multilayer, Wdm, Wireless Computing, Optical Packet Switching, Wavelength Division Multiplexing, Multimedia Traffic, Multuilayer WDM, Traffic Routing, MatPlanWDM, Capacitated Shortest Path First, CSPF, Flow Deviation Algorithm (FDA), and Multilayer Packet Switching
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Denial of Service (DoS) is a security threat which compromises the confidentiality of information stored in Local Area Networks (LANs) due to unauthorized access by spoofed IP addresses. SYN Flooding is a type of DoS which is harmful to... more
Denial of Service (DoS) is a security threat which compromises the confidentiality of information stored in Local Area Networks (LANs) due to unauthorized access by spoofed IP addresses. SYN Flooding is a type of DoS which is harmful to network as the flooding of packets may delay other users from accessing the server and in severe cases, the server may need to be shut down, wasting valuable resources, especially in critical real-time services such as in e-commerce and the medical field. The objective of this paper is to review the state-of-the art of detection mechanisms for SYN flooding. The detection schemes for SYN Flooding attacks have been classified broadly into three categories - detection schemes based on the router data structure, detection schemes based on statistical analysis of the packet flow and detection schemes based on artificial intelligence. The advantages and disadvantages for various detection schemes under each category have been critically examined. The performance measures of the categories have also been compared.
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This paper examines the implementation of the Singular Value Decomposition (SVD) method to detect the presence of wireless signal. The method is used to find the maximum and minimum eigenvalues. We simulated the algorithm using common... more
This paper examines the implementation of the Singular Value Decomposition (SVD) method to detect the presence of wireless signal. The method is used to find the maximum and minimum eigenvalues. We simulated the algorithm using common digital signal in wireless communication namely rectangular pulse shape, raised cosine and root-raised cosine to test the performance of the signal detector. The SVD-based signal detector was found to be more efficient in sensing signal without knowing the properties of the transmitted signal. The execution time is acceptable compared to the favorable energy detection. The computational complexity of SVD-based detector is medium compared to the energy detector. The algorithm is suitable for blind spectrum sensing where the properties of the signal to be detected are unknown. This is also the advantage of the algorithm since any signal would interfere and subsequently affect the quality of service (QoS) of the IEEE 802.22 connection. Furthermore, the algorithm performed better in the low signal-to-noise ratio (SNR) environment.
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Recent adaptive holographic equalization experiments in multimode fiber demonstrate the advantage of the rapid reconfiguration speed of the spatial light modulator in mitigating modal dispersion, the principal source of bandwidth... more
Recent adaptive holographic equalization experiments in multimode fiber demonstrate the advantage of the rapid reconfiguration speed of the spatial light modulator in mitigating modal dispersion, the principal source of bandwidth limitation in MMF. Despite the suppression of a large number of modes, power modal coupling still manifests within the channel. In this paper, a noninterferometric modal decomposition technique was adapted for quantifying the amount of power modal coupling between the modes, for a holographic equalization experiment with a priori modal electric field input. The derivation of the objective function, simulation of binarized holograms and experimental work on intensity measurements at the MMF output are presented.
Research Interests: Optical Fiber Communications, Nonlinear Fiber Optics, Fiber Optics, Multi Antenna Multiple Access Techniques, Photonics, and 18 moreModal Analysis, Fiber Optic Sensors, Interferometry, Applied Electromagnetics, Applied Mathmatics, Selective Launch, Optical Waveguide, Laguerre-Gaussian beams, Spatial Multiplexing, Multimode Fiber, Mode Decomposition, LP Modes, Mode Division Mulitplexing, Laguerre Modes, Spatial Muliplexing, Transmitter Diversity, Receiver Diversity, and Selective Mode Excitation
For a conventional launch into an MMF, a large number of modes is excited, entailing significant modal dispersion and limiting the bandwidth of the MMF link. To mitigate modal dispersion in MMF, a new single mode field generation... more
For a conventional launch into an MMF, a large number of modes is excited, entailing significant modal dispersion and limiting the bandwidth of the MMF link. To mitigate modal dispersion in MMF, a new single mode field generation technique using a transmissive spatial light modulator and a set of lenses is proposed and demonstrated experimentally. The rapid reconfiguration speed of the SLM surmounts the mode switching limitations of previous single mode field generation techniques while allowing for adaptive updating of the incident field on the MMF. For modes up to azimuthal and radial mode numbers of 4, the generated modal electric fields achieved high power coupling efficiencies, in the range of 90.15% to 95.79%
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This paper highlights an algorithm for detecting the presence of wireless signal using the Singular Value Decomposition (SVD) technique. We simulated the algorithm to detect common digital signals in wireless communication to test the... more
This paper highlights an algorithm for detecting the presence of wireless signal using the Singular Value Decomposition (SVD) technique. We simulated the algorithm to detect common digital signals in wireless communication to test the performance of the signal detector. The SVD-based signal detector was found to be more efficient in detecting a signal without knowing the properties of the transmitted signal. The performance of the algorithm is better compared to the favorable energy detection. The algorithm is suitable for blind spectrum sensing where the properties of the signal to be detected are unknown. This is also the advantage of the algorithm since any signal would interfere and subsequently affect the quality of service (QoS) of the IEEE 802.22 connection.
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The modal electric field of an infinite parabolic multimode fiber may be expressed in terms of the generalized Laguerre function. The nature of the Laguerre function is intricate; hence the understanding and visualization of the modal... more
The modal electric field of an infinite parabolic multimode fiber may be expressed in terms of the generalized Laguerre function. The nature of the Laguerre function is intricate; hence the understanding and visualization of the modal electric field for an infinite parabolic multimode fiber may not be immediately intuitive. To capture the essence of various properties of the transverse modal electric field of the infinite parabolic multimode fiber, various simulations are drawn on and key observations are made.
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Dynamic cell sizing is a flexible load-balancing scheme which allows potential capacity gains by modifying its coverage area at any given time for optimum performance. In this paper, the diverse interaction among cells is discussed. The... more
Dynamic cell sizing is a flexible load-balancing scheme which allows potential capacity gains by modifying its coverage area at any given time for optimum performance. In this paper, the diverse interaction among cells is discussed. The preliminary description of forward link capacity gain on a single cell serves as groundwork for discussions on bi-directional impact of cell-pairs and the multifarious interactions of cells in a CDMA network. The diverse interaction of cells is then made analogous to that of community members in a virtual community in a genetic algorithm. The cell to be given highest priority cell over shrinking in the virtual community is selected by the virtual community parallel genetic algorithm (VC-PGA). By this method, the number of cell attenuations may be controlled, the emergence of coverage holes reduced and thus, the quality of service increased.
Research Interests: Wireless Communications, Radio Resource Management, Wireless Sensor Networks, Traffic Engineering, Traffic control, and 9 moreWireless networks, Mobile Computing, Genetic Algorithm, Mobile adhoc Network, Wireless Computing, Handoff Analysis for UMTS Environment, Handover in Mobile Wimax, Handoff, and Dynamic Cell Sizing
The increasing demand for cellular communicates access require a substantial increase in traffic capacity and full coverage of service area. In urban areas, the ratio of traffic demand in the busiest hour to the quietest hour can be very... more
The increasing demand for cellular communicates access require a substantial increase in traffic capacity and full coverage of service area. In urban areas, the ratio of traffic demand in the busiest hour to the quietest hour can be very substantial. To accommodate for the increase in traffic during peak hours, a variety of options are possible - more carriers may be added to existing cell sites, the cell may by be split into several smaller cells or alternatively, additional base stations may be built. However, these methods require the operator to drive a new frequency plan and as for the case of cell splitting, and additional base station construction, a new coverage plan will be required. The cost of installing new hardware and devising new frequency and coverage plans is considerable. It is therefore vital for an operator to ensure that their resources are utilized to their full potential. In light of the above, a more flexible network is required. In this paper, the potential benefits of dynamically controlling the size of any given cell within a layer of hierarchical cells are investigated.
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Voice over Internet Protocol (VoIP) has grown quickly in the world of telecommunication. Wireless Local Area Networks (WLANs) are the most performance assuring technology for wireless networks, and WLANs have facilitated high-rate voice... more
Voice over Internet Protocol (VoIP) has grown quickly in the world of telecommunication. Wireless Local Area Networks (WLANs) are the most performance assuring technology for wireless networks, and WLANs have facilitated high-rate voice services at low cost and good flexibility. In a voice conversation, each client works as a sender or a receiver depending on the direction of traffic flow over the network. A VoIP application requires high throughput, low packet loss, and a high fairness index over the network. The packets of VoIP streaming may experience drops because of the competition among the different kinds of traffic flow over the network. A VoIP application is also sensitive to delay and requires the voice packets to arrive on time from the sender to the receiver side without any delay over WLAN. The scheduling system model for VoIP traffic is an unresolved problem. The objectives of this paper are to identify scheduler issues. This comprehensive structure of Novel Voice Priority Queue (VPQ) scheduling system model for VoIP over WLAN discusses the essential background of the VPQ schedulers and algorithms. This paper also identifies the importance of the scheduling techniques over WLANs.
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Wavelength division multiplexing passive optical network (WDM –PON) is being widely considered for the deployment of fiber-to-the-home (FTTH) to deliver broadband access to business and home users. Optical vortices are helical wavefronts... more
Wavelength division multiplexing passive optical network (WDM –PON) is being widely considered for the deployment of fiber-to-the-home (FTTH) to deliver broadband access to business and home users. Optical vortices are helical wavefronts which focus to rings, rather than central points. This important property makes optical vortices ideal for exciting higher-order modes which are less prone to manufacturing defects in core refractive index and have closer propagation times. This research presents the application of VCSEL arrays for the independent transmission of parallel data streams over optical vortices in multimode fiber to increase the degrees of freedom in a FTTH WDM-PON. VCSEL arrays are selected for multiplexing optical vortices in WDM-PONs as they are tunable, compact, individually addressable and inexpensive. This book presents the mathematical framework and simulation of a novel design for WDM-PON using optical vortices. A transmission speed of 40Gbps is achieved at a central wavelength of 1550.12 nm while maintaining a BER of less than 1 x 10-9. The analysis reveals important results to be considered by operators towards the successful deployment of WDM-PON FTTH networks.
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he proliferation of multimedia data services has spurred the remarkable growth of the mobile cellular network industry. To optimize the resources and performance of mobile cellular networks, spectrum management and traffic congestion... more
he proliferation of multimedia data services has spurred the remarkable growth of the mobile cellular network industry. To optimize the resources and performance of mobile cellular networks, spectrum management and traffic congestion control are key issues. In large cities, traffic demands are heavier in the city center compared to the suburbs, with a large busiest to quietest traffic ratio. Dynamic cell sizing is a flexible traffic congestion control mechanism which increases the capacity of a network by adaptively varying the pilot power to modify the coverage areas of cells for optimum performance under various traffic conditions. In order to mitigate the occurrence of coverage holes in a dynamic cell sizing environment, it is important to prioritize cell attenuation based on the traffic load of adjacent cells. This book presents a novel framework for predictive priority-based cell attenuation in dynamic cell sizing.
Research Interests: Telecommunications Engineering, Antennas & Radio Wave Propagation, Wireless Communications, Telecommunications, Radio Resource Management, and 10 moreMobile Communications, Directional Antenna, Power Control, Cellular Network, Spectrum Management, Network Capacity, Traffic Analysis and congestion control, Network Planning, Dynamic Cell Sizing, and Priority-based Attenuation
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An optical transceiver using a transmissive binary amplitude spatial light modulator and three lenses is proposed for enhancing the bandwidth of a multimode fiber channel. Theoretical modal electric field information is provided to... more
An optical transceiver using a transmissive binary amplitude spatial light modulator and three lenses is proposed for enhancing the bandwidth of a multimode fiber channel. Theoretical modal electric field information is provided to optimize the channel impulse response, thereby reducing the number of iterations required for reducing modal dispersion and increasing the bandwidth. The proposed holographic transceiver increases the bandwidth of a conventional launch, particularly for local area network systems. The increased transmission speed and link capacity supports ubiquitous multimedia-rich applications in business, education, medicine and media industries.
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Research Interests: Optics and Holography
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Research Interests: Finite Element Methods, Finite Element Analysis (Engineering), Computational Electromagnetics, FDTD, Finite-Difference Methods, and 7 moreNumerical Methods, Applied Numerical Methods in Engineering, Lase beam propagation, Laser Beam Propagation in Atmosphere, Power Coupling Efficiency, Coupling Coefficient, and Finite Differences Time Domain, FDTD
Efficient application of the electro-optic effect in a lithium-niobate-based Mach-Zehnder interferometer to construct universal gates has been demonstrated. The study is carried out by simulating the proposed device with the beam... more
Efficient application of the electro-optic effect in a lithium-niobate-based Mach-Zehnder interferometer to construct universal gates has been demonstrated. The study is carried out by simulating the proposed device with the beam propagation method, and the results are verified using MATLAB. Various parameters influencing the performance of the device (such as speed, latency, and power consumption) also have been taken into account.
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The Mach–Zehnder interferometer (MZI) structures collectively show powerful capability in switching an input optical signal to a desired output port from a collection of output ports. Hence, it is possible to construct complex optical... more
The Mach–Zehnder interferometer (MZI) structures collectively show powerful capability in switching an input optical signal to a desired output port from a collection of output ports. Hence, it is possible to construct complex optical combinational digital circuits using the electro-optic effect constituting MZI structure as a basic building block. Optical switches have been designed for 1-bit and 2-bit magnitude comparators based on electro-optic effect using Mach–Zehnder interferometers. The paper constitutes a mathematical description of the proposed device and thereafter simulation using MATLAB. Analysis of some factors influencing the performances of proposed device has been discussed properly. The study is verified using beam propagation method.
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The optical switching phenomena have been studied and their efficient applications to construct the 2-bit multiplier based on electro-optic effect in Mach-Zehnder interferometers (MZIs) have been used. The Mach–Zehnder interferometer... more
The optical switching phenomena have been studied and their efficient applications to construct the 2-bit multiplier based on electro-optic effect in Mach-Zehnder interferometers (MZIs) have been used. The Mach–Zehnder interferometer (MZI) structures working on the principle of electro-optic effect show the powerful ability to switch the optical signal from one output port to the other output port. Hence, it is possible to construct some complex optical combinational digital circuits using the electro-optic effect based MZI structure as a basic building block. The paper constitutes the mathematical description of proposed device and thereafter compilation using MATLAB. The study is carried out by simulating the proposed device with Beam propagation method (BPM).
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ABSTRACT Photonic Crystal Fibers (PCFs) have special structures and offer a number of novel design options, such as very large or very small mode areas, high numerical aperture, guidance of light in air, and novel dispersion properties.... more
ABSTRACT Photonic Crystal Fibers (PCFs) have special structures and offer a number of novel design options, such as very large or very small mode areas, high numerical aperture, guidance of light in air, and novel dispersion properties. PCFs have become an attractive field for the researchers and they are trying to work on these to get their properties applied in dispersion related applications, sensing applications and much more. PCFs sensors are widely used in bio-medical applications. The sensitivity and performance of sensors are enhanced due to novel applications of PCFs. This paper outlines a novel design for a generalized biomedical sensor by collaborating PCF and electro-optic effect of Lithium Niobate (LiNbO_3) based Mach-Zehnder interferometer (MZI) structure.
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ABSTRACT In the advent of tremendous data growth in local area networks, various dimensions for multiplexing and modulating data in multimode fiber have been utilized in the intensity, phase, wavelength and time domains. The modal... more
ABSTRACT In the advent of tremendous data growth in local area networks, various dimensions for multiplexing and modulating data in multimode fiber have been utilized in the intensity, phase, wavelength and time domains. The modal dimension, however, has been relatively untapped. This paper models mode division multiplexing (MDM) of spiral-phased donut modes of different diameters generated from two VCSEL arrays and coupled into a MMF. A data rate of 40Gb/s for a distance of 1500 meters is achieved. The power coupling coefficients, modal delays and bit-error rates at the photodetectors are analyzed for different mode vortex orders.
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Radio-over-free-space-optics (Ro-FSO) is a promising technique to distribute radio frequency (RF) signals over the atmosphere using optical carriers. In this work, we designed a 60Gbps-120GHz OFDM-Ro-FSO transmission system in conjunction... more
Radio-over-free-space-optics (Ro-FSO) is a promising technique to distribute radio frequency (RF) signals over the atmosphere using optical carriers. In this work, we designed a 60Gbps-120GHz OFDM-Ro-FSO transmission system in conjunction with mode division multiplexing. Three independent 40 GHz radio signal are optically modulated at 20 Gbps and transported over a secure free-space link of 50 km by mode division multiplexing of three Hermite-Guassian modes HG 00, HG 01 and HG 02.
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Electrical component speed is a major constraint in high-speed communications. To overcome this constraint, electrical components are now being replaced by optical components. The application of optical switching phenomena has been used... more
Electrical component speed is a major constraint in high-speed communications. To overcome this constraint,
electrical components are now being replaced by optical components. The application of optical switching
phenomena has been used to construct the design of the D flip-flop and T flip-flop based on the electro-optic
effect in a Mach–Zehnder interferometer (MZI). The MZI structures show the powerful ability to switch the
optical signal from one output port to the other. Hence, it is possible to construct some complex optical combinational digital circuits using the electro-optic-effect-based MZI structure as a basic building block. This paper
constitutes the mathematical description of the proposed device and thereafter compilation using MATLAB.
The study is carried out by simulating the proposed device with the beam propagation method.
electrical components are now being replaced by optical components. The application of optical switching
phenomena has been used to construct the design of the D flip-flop and T flip-flop based on the electro-optic
effect in a Mach–Zehnder interferometer (MZI). The MZI structures show the powerful ability to switch the
optical signal from one output port to the other. Hence, it is possible to construct some complex optical combinational digital circuits using the electro-optic-effect-based MZI structure as a basic building block. This paper
constitutes the mathematical description of the proposed device and thereafter compilation using MATLAB.
The study is carried out by simulating the proposed device with the beam propagation method.