Master of Science in Electronics & Telecommunications

Permanent URI for this collectionhttp://192.248.9.226/handle/123/233

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Now showing 1 - 13 of 13

item: Thesis-Abstract
Sensor node localization in the presence of limited anchor nodes
Wicramasinghe, GB; Dias, D
Wireless sensor networks hold the promise of many new applications in the area of monitoring and control. In most applications if location information of the sensing node is not available, measured data from sensing node become meaningless. Iterative techniques are widely used to enhance localization coverage. Main problem with iterative technique is error propagation. So this research proposes a mechanism to improve the localization coverage as well as a new technique to minimize the error propagation. new Localization coverage improvement is based on the 2 hop neighbors (referred as “New method”). When a location unknown node has only 2 anchor node in its radio range, location can’t be determined. But if 2 hop anchors are available with satisfying a certain criteria location can be determined as shown in this research. In Iterative techniques once location is determined it is upgrade to anchor status. Ifthis node upgrade is handled more carefully error propagation can be minimized. So this research proposed Distance Measurement Error based node upgrade to minimize the errors. Simulations were carried out for three simulation scenarios to demonstrate the performance improvement of the proposed techniques. According to the simulation results obtained, 7% improvement for localization coverage and 4% improvement for localization accuracy from the DME based anchor node upgrade were achieved with respect to standard trilateration.
item: Thesis-Abstract
Input voltage imbalance compensation in peak current mode controled half bridge converters
Fernando, LTN; Munasinghe, R
Instability of the input capacitors’ midpoint voltage has been observed to be one of the major obstacles ofimplementing the peak current mode control in symmetric half bridge converters. Slight variation of the voltage balance in input capacitors may cause serious damages to the operation of the half bridge converter leading total failure ofthe operation ofthe power converter. Some methods have been proposed in various papers some of them includes major changes in the power stage which requires specific application oriented design of some of the basic power stage components (ie: transformer) reducing the availability of components for custom designs. This analysis proposes simple but reliable solution to the aforesaid matter without applying any major modification to the power stage of the half bridge converter circuit and its hardware implementation. This discussion will also extend to analyze various instability phenomena’s possible in the peak current controlled half bridge converter applications in power conversion.
item: Thesis-Abstract
Ukuwela-Polgolla remote telemetry system & forecasting water level of Polgolla Barrage
Amarasinghe, D; Munasinghe, R
In this project, a wireless telemetry system was designed and implemented to monitor the water level information of Polgolla barrage from the control room of Ukuwela power station. Using the water level variation, a mathematical algorithm was developed to predict the time to reach minimum / maximum water levels. The wireless telemetry system consists ofthree sub systems. They are I. Data transmitting unit located at Polgolla dam: The water levels are digitized by “Analog Input Modules” and fed the the Telemetry Module. The gate Open / Close status are directly fed to the Telemetry Module serialize these information and send the Data Radio. The Data Radio modulates these information and transmit in to the air. II. The Repeater Station located at Dunuwila: Receives this information and re transit after five seconds. (Store & Forward Repeater) III. Data receiving unit located at Ukuwela Power Station: The information received by Data Radio are sent to the Telemetry Module. It de-multiplexes the information and a) Updates Analog Output modules so that these output modules can re-construct original water level information. b) Outputs gate open / close status through relay contacts. The mathematical algorithm uses two sets of input data. I. Water volume, V(h) vs water level, h ; This is available as a table. II. Water level, h(t); This is given by the above mentioned telemetry system. This model can be run on a personal computer and can be used to estimate the time taken to reach maximum and minimum water level and raise alarms.
item: Thesis-Abstract
Low cost weight measurement technique with fuzzy controlled pneumatic muscle
Pallawela, PM; Kulasekara, C
Weighing of material has been a basic human need since ancient times. Currently there are requirements in the general industry to assess approximate weights of objects electronically for various purposes at a low cost. The possibility of using pneumatic muscle for this purpose has been explored in this research attempt since pneumatic muscle is becoming very popular among robotic designers due to its very high power to weigh ratio, the low price and because of its ease of use. Apart from this main objective, another area is also focused in this research. This is to obtain servo pneumatic actuation from pneumatic muscle or fine control of actuation. The increasing number of muscle based robotic arms and manipulation systems built through out the world for various tasks, need to assess the weights of objects manipulated by the particular system in order to establish a proper control function for the system. Therefore a solution for this requirement has been given priority and explored during this research. The methodology proposed is to design suitable pneumatic control system for fine elongation control of the muscle in order to eliminate the highly non-linear dynamic behavior of the muscle. Thereafter to do research studies in order to identify the characteristic curves of the required properties. Final stage has bee focused on the design of a suitable electronic controller and to establish an electronic set up for the measurement of weight. Design and implementation of a suitable Fuzzy controller is descriptively explained under this section. After this step the setup was practically utilized to measure weight and results were tabulated against the measured weight with load cell based weighing scales. Finally the conclusions were raised and also the suitability of this apparatus as a smooth actuation controlling device is also discussed.
item: Thesis-Abstract
Broadband connectivity using optical Access for the eastern province of Sri lanka
(2015-08-27) Alakurajah, B; Samarasinghe, ATLK
In Sri Lanka the widely used wired technology for broadband access is Asymmetric Digital Subscriber Line (ADSL).Fiber access is available in the Western Province with limited usage such as for business purposes. The Eastern Province is the focus for this research because it is one of the affected areas during the last two decades ofwar and therefore has limited facilities for the people living in that part of the country.The development work in the Eastern Province is in progress at present and it also includes facilities for broadband access. ADSL broadband usage within Eastern Province is available but limited to city areas only. This work focuses on a system to implement Fiber to the Home (FTTH) for the Eastern Province and thus provide efficient broadband access for its people. The available Fiber Access technologies are analyzed and the most suitable one is selected for implementation. The thesis proposes a network based on Passive Optical Network (PON) technology to be employed with Gigabit PON (GPON) in order to provide FTTH to a wider area of the Eastern Province. The GPON technology includes Coarse Wavelength Division Multiplexing (CWDM) with Time Division Multiple Access (TDMA); known as Hybrid PON. For the selected four cities Optical Line Terminal (OLT) locations are identified and Ring topology access is used with Remote Nodes which can be expandable when customer number increased. A cost estimate using the current equipment prices and the payback of the capital are calculated and presented in the thesis. The performance of the proposed network is analyzed which includes the Link Power Budget and the Bit Error Rate(BER). The performance analysis shows that the proposed Optical Access Network using GPON is feasible for implementation in the Eastern Province.
item: Thesis-Abstract
A Novel controller for a voltage source sine wave transformerless boost inverter
(2015-06-24) Molligoda, LDA; Muanasinghe, SR
In this thesis a transformer less voltage source sine wave inverter is proposed. A previously developed tri-state boost converter is utilized for the stepping up operation. By using this topology the dynamic response of the inverter is increased, by avoiding the right hand plane zero in the converter’s small-signal control-to-output transfer function when operating in the continuous conduction mode. The reference voltage for the tri-state boost converter is determined from the measured output voltage of the sine wave inverter, and the calculated instantaneous value of the sine wave. The inverter with the tri-state boost converter and the inverter with a classical boost converter with voltage mode control and current mode control are compared for the dynamic response and efficiency. The analytical work of the design has been verified using a simulation. Furthermore, the boost converter is implemented in hardware to verify the boost inverter calculations. The current mode control and the tri-state logic hardware implementation is ongoing, and it is presented as future work. Finally, two user selectable modes are proposed for the inverter optimized for dynamic performance or efficiency.
item: Thesis-Abstract
High resolution stepper motor controller for tunable laser
(2015-06-24) Ganeshanathan, V; Munasinghe, R
Tunable laser systems use stepper motors to rotate the wave selective opticalelements. Stepper motors can rotate with high accuracy and precision. This research focuses on the stepper motor controller, with the feedback to improve the accuracy and the precision of the movement. Sine cosine and trapezoidal current controlling techniques for micro stepping are analyzed, and used in two different types of situations. The variable step interval technique is proposed to overcome the speed variation in the trapezoidal current controlling technique. The proposed controller uses the linear interpolation and sine cosine current controlling technique to improve the rotation accuracy by two times than the resolution of the encoder. The technique is proposed to detect the obstacle by using the encoder and the static characteristic of the stepper motor. The simulation and the experimental results show that proposed controller can produce the required accuracy, the precision and obstacle detection. Also, the movement smoothness could be achieved by variable step intervals. Therefore, proposed controller has better performance to suit the tunable laser system.
item: Thesis-Abstract
Development of holonomic mobile platform for field robotic applications
(2014-08-12) De Silva, WR; Munasinghe, R
Most mobile platforms or vehicles used today are non holonomic. They only have one or two independent degrees of freedom. Due to that its maneuverability is limited and often requires much space to control functions like turning and parking. By improving degrees of freedom (improving the maneuverability) of a vehicle, it can follow many complex trajectories that are difficult or impossible by conventional non holonomic vehicles. Any mobile platform that has three independent degrees of freedom in a plane is a holonomic platform. Independent degrees of freedom means that it can change its orientation or position without effecting other motions unlike in car type vehicles that require turning or changing its orientation when need to move. Holonomic motion is very useful to acquire abilities such as, avoid any obstacle while keeping its orientation the same, capability to move in constrained spaces and track a target while moving in an arbitrary trajectories etc. Because of these advantages and capabilities some of the scientific and industrial researches are targeting to develop holonomic mobile platforms. Already robotics community have managed to build some working models and used in applications like robot soccer games and mobile robot manipulators. Many different mechanisms have been created to achieve the holonomic capability. These include various arrangements of Swedish wheels or omni wheels, chains of spherical or cylindrical wheels, ball wheels and powered caster wheels etc. While most of these designs are practical in indoor environments they are not suitable for outdoor operations in large scale versions. In this research project our goal was to develop a viable design to achieve holonomic capability that minimizes these problems and more suited to outdoor operations. The proposed design has a wheel arrangement similar to a car but with the capability of independent driving and steering capability of each of the four wheels. Car type rolling and steering mechanism avoid any uneven wear of the wheels and avoid lateral forces applied on the wheels. Wheel driving and steering mechanism was designed such a way that wheels can be steered 360 degrees continuously without interfering with the wheel drive system. This enables the platform to move in complex trajectories continuously without stopping for wheel resetting. The developed platform has increased ground clearance that is necessary for outdoor rough terrain operations like farming. Although these benefits exist, controlling the robot to acquire the desired motion is very complex and need innovative algorithm. Four independent wheels with eight degrees of freedoms to achieve three degree of freedom motion is a redundant control problem and require complex control system. Using inverse kinematics model of the platform and multiprocessor design with advance micro-controllers we have tried to solve these issues and were able to achieve successful performance.
item: Thesis-Abstract
Development of a decision support system for long sea outfall designing and operations
Lankasena, BNS; Ratnayake, N; Indralingam, M
Long sea out-fall is an acceptable method of domestic wastewater disposal, provided that the design is done properly, and it is constructed robustly and according to the design. The dispersion of the sewage after discharging to the sea has come under increased scrutiny in recent years, due to the sea and seashore pollution. In a properly designed and constructed long sea out-fall, the waste is discharged at a point in sea, away from any environmentally sensitive areas such as coral reefs, and far enough from the beach so that the quality of water reaching the beach conforms to the stipulated standards. In this research development of SOS (Sea Outfall System) was done and a successful implication of GA (Genetic Algorithm) in sea outfall optimization and ANN (Artificial Neural Network) in concentration prediction after discharging to sea is introduced. The SOS is specially developed to design and identify pollutant behavior of sewage discharged using Multi-port Diffusers. The system is designed to handle several scenarios such as stratified and unstratified sea conditions and stagnant and flowing plumes. The system can predict concentrations of parameters in the far field as well as the near field, and also can be used as a decision support system for designing. It is also capable of analyzing the near field of single port sea outfalls, and can be developed for the far field analyzing and design decisions of multiport diffuser discharges. SOS Expert (Decision-maker) provides decisions on required designing configurations, so that the user can find optimum configurations. SOS HELP provides necessary information about long sea outfalls as well as information about the SOS. In addition to SOS, Artificial Neural Network (ANN) too is used in concentration prediction after outfall discharging. Artificial Neural Networks are capable of modeling experience based non-algorithmic knowledge. Different technologies and data gathering methodologies used in ANN training and it is possible to develop site-specific neural networks for predictions. The system is developed according to Object Oriented Techniques. Major programming is done using Visual C++ Version 6.0 and MATLAB 5.3 was used in GA optimizations. WinNN Version 0.93 used in ANN designing, training and testing. The system provides an easy way to identify concentrations due to dispersion and decaying. With the help of SOS Expert designers can optimize outfall configurations. The cost and time needed in sea outfall designing and operations can be reduced with the SOS, SOS Expert, GA optimization technique and ANN predictions.
item: Thesis-Abstract
Indoor signal propagation : a case study for Sri Lanka
Chandraguptha, GLR; Samarasinghe, ATLK
Mobile communication radio channel vanes very rapidly at times and causes very hard to predict its behavior and characteristics. Even if the channel does not explicitly change, speed of the mobile user and the surrounding will contribute to these variations causing many problems for mobile communication. Therefore study of Indoor signal propagation is an important factor in arriving at a good mobile network design. Most of the work carried out in this area is specific for a particular country, region or area as evident by previous researches. Research specific to an area is essential since deals with surrounding buildings, environment and especially in the case of indoor propagation building material used for construction. In this research the radio signal strengths inside a building were measured for two cases; one where the transmitter is an outdoor antenna installation and the other where the transmitter is an indoor antenna installation. Literature surveyed propagation models, equations and other graphs were used to map the measured and analyzed signal strength values, attenuation characteristics, propagation characteristics. Principal objectives of the research were to determine how these parameters fit into best model(s) and determine the parameters appropriately to suit the conditions in Sri Lankan context. The parameters obtained are of similar range with other literature surveyed values such as path loss exponent, floor attenuation factor and partition attenuation factor values. The parameters obtained can be used for any commercial software used in indoor signal strength estimations as the starting values for signal strength optimization and in order to obtain better results in terms of optimum signal coverage and optimum antenna placement. Generalization of these parameters for Sri Lankan context can be done once similar type of analysis is carried out in many buildings in Sri Lanka
item: Thesis-Abstract
Analyzing traffic behavior and treatment in NGN IP core networks
Karunaratne, MAIK; Samarasinghe, K
Today Internet Protocol has taken over the entire communication. With the advancements in the new technologies cost of the IP related equipments has come down which has helped this exponential growth. with the increase of the usage the telecommunication service providers are expanding their infrastructure to cater the growth. Entire world is expanding their infrastructure mainly on IP equipments. Integrating the legacy infrastructure to the IP Network has lot of challenges. The real challenges are the transporting delay sensitive traffic like voice over the IP Network, IP node failures, IP link failure detections, delay variations. There are proprietary systems being developed between the IP vendors and the others in order to over come these challenges which can sometime be not flexible to the telecom service provider. In this research an open standard based approach is used to integrate media gateways to an IP/MPLS Network. The challenges of the integration are discussed in this thesis. A lab setup and a live network test were performed in order to measure the quality of the integration work. The interconnection methods were analyzed after going through the theories related to the media gateways and IP/MPLS technologies. Also since there. can be different type of traffic in an IP/MPLS network a traffic treatment method should also be developed The major results of the research was that using open standards methods the Essential parameters for the Media gateway integration of the IP core networks can be achieved. Also the model that was developed for the traffic treatments was successful. Media gateways interconnections with IP. networks are successful on open standards IP protocols. Fast convergence requirements, QoS requirements and jitter and delay requirements can be addressed using open standards IP protocols
item: Thesis-Abstract
Analysis of early dropping mechanism for optical burst switched networks
Amarasinghe, T; Thilakumara, P
Quality of Service in Optical Burst Switched Networks using Early Dropping Mechanism with Different Network Characteristics Keywords: Optical Burst Switching (OBS), Absolute Quality of Service (QoS), Early Dropping Mechanism, Dense Wave Length Division Multiplexing (DWDM). Optical Burst Switching is a promising bufferless DWDM switching technology that can potentially provide high wavelength utilization. Quality of Service support has become an important issue in OBS networks. There are two models to guarantee QoS in OBS networks. Those are relative QoS guarantee and absolute QoS guarantee. Most existing schemes are based on relative QoS model and in those models the service levels can be defined relative to the service requirements of another class of traffic. In absolute QoS model it provides a bound for loss probability of the guaranteed traffic. This kind of hard guarantee is essential to support applications with bandwidth constraints. Further efficient admission control and recourse provisioning mechanisms will enhance the service of absolute QoS model to guarantee the service requirements in the OBS networks. Early dropping mechanism is proposed to maintain the dropping probability in Absolute QoS model in OBS networks. Due to the bufferless nature of the OBS core nodes, the early dropping mechanism computes the intentional dropping probability based on measured , online loss probability. In early dropping mechanism it can be simply implemented by using a threshold value which is responsible to maintain the maximum acceptable loss probability. But in this mechanism the lower priority class of traffic suffers from high loss probability when higher priority Glasses exceed its threshold vales of loss probability. Early dropping by Span mechanism introduces a span of acceptable loss probabilities rather than using one threshold value andthis mechanism has improved QoS guarantee in higher priority classes of traffic while reducing the loss probability of lower priority classes as well. Further the performance of this mechanism can be applied in a dynamic wave length assigning network in order to guarantee the absolute QoS with efficient recourse provisioning
item: Thesis-Abstract
TCP performance evaluation in a VSAT link
Fernando, KM; Samarasinghe, K
The Transmission Control Protocol (TCP) is the mostly used protocol for data transmission over networks. However, TCP's congestion control algorithm wasn't created to match the special characteristics of satellite links, resulting in a drastically performance degradation. TCP appears in different algorithm versions, all with different features but with maximal throughput as their main objective. The aim of this paper is to evaluate and compare six TCP versions, which are Tahoe, Reno, New Reno, Sack, Fack, and Vegas, when applied over GEO satellite VSAT links in TCP connections, using Ns-2 simulation. Suitable scenarios based on a GEO bent-pipe satellite have been implemented. I evaluate the performance of the above mentioned TCP versions over GEO VSAT-based satellite links and compare it with the performance of a real VSAT link. It was found that the flow and congestion control mechanism used in some of TCP versions were unable to reach full utilization on VSAT link speeds.

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