Master of Science By Research

Permanent URI for this collectionhttp://192.248.9.226/handle/123/18682

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item: Thesis-Full-text
A 3D models of human ejaclulatory ducts
Gunasekera, CL; Dayananda, N
Benign Prostatic Hyperplasia (BPH) is a common non-malignant ailment effecting in ejaculatory duct of aging men. BPH induces bothersome lower urinary tract symptoms. The standard treatment for BPH is Transurethral Resection of the Prostate (TURP), which mitigate urinary symptoms and enhance urinary flow. Smooth sphincter of the bladder neck accumulates and resides seminal fluid as it reaches the prostatic urethra before it ejects during ejaculation. Retrograde ejaculation occurs due to removal of this smooth sphincter of the bladder neck during TURP. Hence, about 53-77% patients develop retrograde ejaculation after the procedure. The research has shown that preserving the portion of supramontanal prostatic tissue during TURP leads to preserve antegrade ejaculation in about 80% of patients. The accuracy of this surgical procedure could be enhanced by the aid of 3D modelling. A literature survey on the existing procedures for model construction indicated that further improvements could be achieved through reconstructing a 3D model. A 3D model will enhance the understanding of the anatomical relationship of the ejaculatory ducts and prostatic urethra in cross sections of the prostate gland and to determine a safe zone with the prostate to remove without damaging the ejaculatory ducts. We used photographic images of prostates obtained from male cadavers above the age of fifty years. The prostate samples fixed on to a wax block and uniform 2 mm thick slices were removed sequentially while taking photographs with a digital camera. Major steps in constructing a 3D model from the acquired images include: image registration to align series of slices, segmentation of the prostate, urethra and ducts and 3D modelling of the segmented structures. A simple landmark based image registration technique was employed by manually selecting points along the four edges of the wax block and automatically detecting the vertices of the block using intersections. Then rotation, translation and scaling were estimated on individual slices to align all the slices. The prostate was then segmented manually using an existing software tool program. The ejaculatory ducts and the urethra were segmented using a simple active contour based segmentation tool. Finally, a 3D mesh model was developed using boundary points of each of the segmented structure. The following three surgically important measurements calculated using to the model: the angles of the centre of the left duct, to the centre of urethra and to the centre of right duct, perpendicular distance from the centre of urethra to the line joining the two centres of ducts, and width of the prostate. Results showed a large angle both proximally and distally, 3D relationships of ejaculatory ducts and urethra depended on the maximum width of the prostate. During TURP, safe distances to resect the prostate without damaging the ducts are calculated based on the maximum width of the prostate. Depth can be safely resected without damaging the ejaculatory ducts. In the future, it is quite essential to test these results on clinical grounds.
item: Thesis-Abstract
Adaptive video streaming for bandwidth variation with optimum quality
(2014-05-31) Medagama, JMW; Dias, D; Fernando, MSD
Bandwidth scarcity is a common problem faced in video transmission over broadband networks, particularly in wireless medium. It is important to find solutions for that since high bandwidth consuming video applications such as video streaming, video conferencing are of high interest to the broadband and mobile users today. This thesis presents adaptive video streaming based methodology to address the given problem. Adaptive streaming is discussed through transcoding. It is a solution that can be adopted to overcome this problem in any network environment. Conversion of video to a form that has less information so that the resulting data volume is appropriate for streaming over a low bandwidth scenario can be done with transcoding. But the video quality drops due to transcoding. A compromise can be made between the video quality and network delay. Effect on video quality and data volume with the variation of transcoding parameters are analyzed in this research, especially with the temporal scaling parameters. A relationship between the transcoding parameters, the data volume reducing factor and the video quality is obtained through numerical methods. Hence a methodology derived from the numerical method is proposed to achieve an adaptive streaming solution. One of the significant outcomes of this thesis is the video quality measurement mechanism proposed that could be used in the presence of spatial and temporal scaling. This solution presents the best transcoding parameters to achieve optimum quality video in a low bandwidth situation. With that, when there is a large number of users are sharing the network, they could watch a video at a lower, but acceptable quality with no interruption. Keywords – Adaptive stream, Transcode, Video quality, Frame Rate, Quantization
item: Thesis-Abstract
Analysis of pairwise error probability bounds for space-time coded mimo systems
Dharmawansa, KDP
Space-time codes have attracted considerable attention in the area of wireless communications due to their ability to exploit the enormous capacity promised by the multiple-input multiple-output(MIMO) antenna system in comparison with a single antenna system. The main idea behind MIOMO is to establish independent parallel channels between multiple transmit and receive antennas. But in reality, the spatial correlation and the tap correlation in the case of frequency selective channel degrade the performance of space -time codes. For that reason, analytically derived pair wise error probability (PEP) expressions or bounds are of great importance in analyzing the performance of space-time codes over different fading environments. The main contribution of this thesis is to provide a broad mathematical framework to derive PEP bounds, which ultimately pave the way to design good codes. A new analytical PEP upper bound is derived in this thesis for frequency selective Rician fading channels with dependent fading coefficients and tap coefficients. The mathematical analysis presented in this thesis in deriving the former bound is sufficiently general to handle any form of fading environment except Nakagami-m fading model. With this bound the impact of correlation towards the code performance is also discussed. An exact PEP expression is also presented in the form of a definite integral, which doesn't have a closed form while the closed form is presented when the codewords are taken from orthogonal designs. Since the exact PEP expressions have complicated closed forms, an approximate expression is presented which is valid for sufficiently high signal-to-noise ratios. Although the Nakagami-m fading model is of practical importance compared to the other models, the mathematical complexity is very high if one follows the same classical approach, due to the unavailability of probability density function for a linear sum of several Nakagamim random variables. There is not much literature available related to the properties of spacetime codes due to this complexity. The thesis provides a new way of approach to the PEP upper bound derivation in the case of Nakagami-m fading channels employing two transmit antennas and subsequently it is extended to a more general case. Furthermore, exact PEP expressions are also derived in the case of orthogonal designs. Validity of the bounds is verified by the simulations at the latter part of the thesis.
item: Thesis-Abstract
Analysis on business to business (B2B) e-commerce infrastructure of Sri Lanka
Rodrigo, DNR
This thesis presents the findings from a comprehensive survey done to find out to how far the Sri Lankan Industries have adapted E Commerce technology and also the bottlenecks faced by them in adapting E Commerce" This research has three main Objectives:  To identify the obstacles faced by the Sri Lankan industry to enter into  132B E-commerce through a comprehensive survey To investigate the possibility of B2B Framework specifically suitable for  Sri Lanka and also investigate the services expected by the participants, To propose a suitable framework according to the findings of the survey A general questionnaire was used to gather information of Companies* current use of Internet, their website status and barrier and drivers in adapting E Commerce: and a System Integration questionnaire was designed to feed core indicators on the usage of ICT in those enterprises. At the Pilot Analysis stage population for the direct interviews was selected among the major Companies in Sri Lanka. The research survey covered only the private sector organizations, due to their ability for quick implementation possibility of theB2B e-commerce trading, as they have the potential in entering into L-Commerce. A comprehensive survey was administered by Postal mail, Internet, e-mail and personal interviews. The questionnaire was web enabled to reach larger population, so that the si/e of the sample, together with its geographical dispersion, has a significant bearing on the research. The comprehensive study showed the current situation of B2B E Commerce Infrastructure in the Sri Lankan Industries have barriers and drivers, where recommendations are made to rectify those barriers and make advantages of the drivers, so that they can be in par with the global E commerce. One of the major findings was that the current E commerce regulatory factors in SriLanka do not support the Companies doing B2B E Business. Companies who have technical facilities up to some standards should be encouraged to upgrade their systems to venture into E Business. The available data shows that Sri Lanka Telecommunication Infrastructure availability is not a problem for companies to commence E Business. It is the reliability, running cost and connection cost that mainly affect the businesses* confidence to venture into E business. E commerce solution providers in Sri Lanka are competent in developing Ecommerce solutions but again it is clear that insufficient in-house skills and training and non-availability of in-house technology arise among the organisations which do not engage in E Business. It was revealed that even an enterprise with a single person can practice E Commerce. This is an encouragement to new businessmen in Small and Medium Scale Enterprises to use the advantages in E Commerce.
item: Thesis-Abstract
Blind frequency-offset estimation for OFDM systems operating in frequency selective fading channels
Patabandi, KPCS
Orthogonal frequency division multiplexing (OFDM) is successfully used in many wireless digital communications systems. It is used in Digital Audio/ video broadcasting, Wireless Local Area Networks (LAN) and related discrete multi-tone (DMT) is use in wired digital communications. Power of OFDM lies in dividing wideband channels into narrow band sub cannels while keeping the bandwidth efficiency. When channels are narrow band, they can be considered as frequency flat even in harsh conditions such as mobile communications. It also possesses some disadvantages. Sensitivity of OFDM to carrier frequency offsets and the degradation due to that in performance is one of the main disadvantages. This research work is focused on estimating unknown frequency offsets which cause intercarrier interference (ICI), while maintaining the bandwidth efficiency. There are numerous methods that have been proposed to overcome frequency offset problem in OFDM. Some adversely affect on the bandwidth efficiency by repeatedly transmitting data symbols or by overloading system with synchronization aided data. But there are methods which use inherent properties of OFDM signals to estimate the carrier offset while not lowering the bandwidth efficiency. The technique proposed in this thesis uses a concept which has been published by Mounir Ghogho and Anantharam Swami. But their algorithm has been modified so that a relatively efficient combined quadrature amplitude modulation (QAM) scheme can be used for transmissions. This new combined modulation scheme, which is referred to as pseudo QAM in this thesis, uses full QAM constellation for modulating part of the sub carriers in the OFDM symbol while other sub carriers are modulated using a sub constellation of the full QAM constellation. The sub constellation is selected so that all the symbols in the constellation have the same modulus. The estimation algorithm is based on virtual sub carrier property and the constant modulus property of the pseudo QAM sub carriers. To compare the performance improvement of the proposed scheme, computer simulations have been carried out for multi path fading channel with additive white Gaussian noise (AWGN). Simulation results indicate very good improvement of the accuracy of the estimation relative to the estimation based on virtual sub carriers alone. Few bit error rate (BER) simulations have also been carried out and the results are included to verify performance in terms of BER. The bandwidth efficiency has been improved in proposed scheme since part of the sub carriers can be modulated with full QAM constellations. Hardware required for this new modulation scheme is the same as that for general QAM schemes. Required changes can be carried out in software. System can be made such that it goes for pseudo QAM scheme only when the estimation accuracy obtained with virtual carriers alone is not enough. ii
item: Thesis-Abstract
Broadband connectivity using optical access for the eastern province of Sril Lanka
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 ofthe affected areas during the last two decades of war 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-Full-text
Cellular positioning by location fingerprinting with the aid of propagation models
Wijesinghe, WHMP; Dias, D
The Fingerprinting method or the Database Correlation Method (DCM) is a network based positioning technique which has shown superior accuracy. DCM is based on a pre-measured database of location dependent variables such as Received Signal Strength (RSS). The major challenge of the technique is the effort involved in forming the database, which prevents it being deployed in large, dynamic networks. The work presented in this thesis investigates the possibility of using network planning tool predictions instead of field measurements to create the fingerprint database for DCM. While the accuracy of this approach is lower than the DCM method with field measurements, further tuning of the predictions in order to improve the performance is proposed. The tuning method is defined as cell-wise calibration, which calibrates the predictions by using a lesser number of field measurements in a cell-by-cell basis. In addition, a novel fingerprint filtering approach and a fingerprint matching technique (a cost function) are proposed. The trial results show that, the performance of DCM using the proposed database is inferior to that using a measured database. However, the application of calibration process for predictions improves the performance up to an acceptable level. The calibration method, designed for the bad urban scenario is based on curve fitting whereas that for urban, suburban and rural environments is based on neural networks. In addition, the novel fingerprint filtering approach is robust for the bad urban environment while the novel cost function shows higher performance with the proposed database. The best positioning accuracy for the. bad urban environment is 200m in 80% of the estimates and that for the urban environment is 125m (80%). Remarkable performance improvement can be observed in the rural environment giving a positioning error less than 385m in 80% of the estimates. The performance in suburban environment is inferior to that-in both urban and rural, with an error less than 550m in 80% of the time. The proposed solution for positioning is best suited for the deployment in large dynamic networks as a network-based method to provide basic information services, such as nearest ATM machine, petrol. station or hospital, traffic information and location based advertising.
item: Thesis-Abstract
Database correlation for GSM location in outdoor and indoor environments
Lakmali, BDS; Dias, D
Accurately estimating the location of a Mobile Station is a key requirement to effectively provide a wide range of Location Based Services over mobile network. Since the mobile phone has become a common device in today's society, location based services are very popular among cellular subscribers. Hence developing cellular positioning techniques has been a key research problem and numerous localization solutions have been proposed. These include technologies such as Cell ID, angle and time of arrival methods and fingerprinting methods.// This thesis presents fingerprinting based positioning techniques suitable for different outdoor and indoor environments. Thus multiple positioning techniques are proposed, implemented and evaluated for different environments. Three outdoor trials in areas falls under urban, suburban and rural areas and two indoor trials in two nuiti storey buildings were used for evaluation. The ultimate solution proposed in this thesis is not a single positioning technique; rather it presents several positioning techniques that achieve optimum performance in each test environment.// This thesis proposes a novel fingerprint collection process for outdoor positioning and introduces a more accurate correlation algorithm. This thesis reports 67% positioning error as 12 n, 299 r and 221 l for urban, suburban and rural areas respectively. Experimental results show that the proposed positioning methods achieve accuracy far better than Cell-ID and trilateration approaches for the tested network environments especially for rural area. The 67 % positioning error for rural area is IC45 t and 1386 n with basic Cell-ID and trilateration techniques while proposed fingerprinting based technique reports 67% positioning error as 221 m.// With indoor positioning this thesis reports 50% positioning error as 20.5m and 8.7m for the selected two buildings. Also it was possible to accurately differentiate between floors in these multi storey buildings. Results achieved for Building 2 is reasonable when compared with the results reported in a similar study by Ve jc Otsason et ii (2005).
item: Thesis-Abstract
Design of a vision enabled wireless sensor node
(2020) Wijesinghe WYM; Samarawickrama J; Dias D
This thesis describes a novel system architecture and implementation of a wireless visual sensor node. The proposed design of the node can be used to extract traffic information based on the visual description of road. In this research, the real-time performances and the capability to perform at low power consumption meanwhile obtaining accurate results were considered as the essential factors since a large amount of data need to be processed in an embedded level vision system. At first, a suitable vision algorithm is proposed to harvest the traffic condition on road. The functionality for each section of the algorithm has been performed by using carefully selected available vision techniques and image processing algorithms. The vehicle extraction from the current frame of view and the tracking process of the vehicle are identified as the most important functions in the algorithm. The vehicle extraction from the current frame is carried out by the ViBe algorithm with some modifications in order to acquire promising real time performances and the tracking process is carried out by a light weight but an accurate enough particle filtering technique. Moreover, the complete system is implemented in the FPSoC hardware system as a hardware and software co-design by considering advantages that can be obtained from different aspects. The performances of the system have been evaluated from many aspects for different standard data available from other research works. The conclusions and suggestions for further development have been presented at the end of this thesis.
item: Thesis-Abstract
Design of circularly polarized microstrip antennas
Senavirathna, HMSB
Circularly polarized antennas are used in mobile communication, satellite communication and in other communication systems. The receiver is then able to pick the transmitted signals without a polarization mismatch due to the alignments of the antennas. It can also mitigate multi path interference. In multi path conditions, the reflected signal changes the hand of the circularity giving a polarization mismatch with respect to the signal that arrives from the direct path. Therefore a circularly polarized receiving antenna will pick only the direct path signal which has the desired hand of circularity.// Circularly polarized micro strip antennas can be used in communication systems where the geometry and the size are constraints because it is lightweight, miniature in profile and etched on a double sided printed circuit board.// Analysis, design and implementations are presented of square, nearly square and circular single feed circularly polarized micro strip antennas. In order to get familiarized with the basic theory. A linearly polarized micro strip antennas were first made. Circularly polarized 4 patch planner array antenna, circularly polarized circular patch antenna, circularly polarized micro strip Yagi array antenna and a circularly polarized micro strip frequency scanning antenna were designed with the help of the single patch designs. Transmission line model and resonance cavity model were used in the analysis while the mode detuning method was used to obtain circular polarization.// The single square patch and the single circular patch antennas designed for 9.4 GHz for RHCP showed broad radiation patterns, both in the E- plane and the H -plane, as expected from theory. The polarization was nearly circular while no measurable gain was observed.// The circular patch with protruding perturbations for mode detuning behaved very similar to the circular patches having perturbations with depression. Therefore both methods appear equally good to produce circular polarization.// The circular patch antenna designed for RHCP for 1.4 GHz had a total gain of 5.74 dBi Its radiation pattern is broad and hemispherical and thus this antenna could be fixed on a vehicle for MSAT applications.// The 4-square patch planner array designed for RHCP for 9.4 GHz had a gain of 4.5 dBi. Its measured radiation pattern had 2 major lobes as expected but it also showed minor lobes which was not seen in the theoretical radiation pattern. This could also be a useful antenna for MSAT applications.// The micro strip Yagi antenna for RHCP designed for a frequency of 1.150 GHz had a total gain of 6.2 dBi and its major lobe was tilted by 35° from the broadside direction. By suitable alteration to the element separations, it is possible to tilt the beam by a desired angle. I A 2-element square patch array for RHCP designed for a frequency of 1.4 GHz showed a gain of 4.88 dBi. The measured radiation patterns obtained for the frequency rage from 1.17 GHz to 1.625 GHz had a significant similarity with the theoretical radiation patterns and demonstrated the possibility of frequency scanning with the antenna.
item:
DOA estimation using ann techniques for asynchronous DS/CDMA systems
Kariyapperuma, KADAV
ABSTRACT The demand for the mobile communication services is increasing rapidly and this necessitates finding new ways to use the spectrum more efficiently. As a solution, smart antenna systems are found to be promising. For a smart antenna system to operate efficiently, accurate Direction of Arrival (DOA) information of the sources are needed. This thesis proposes a new technique for estimating the DOA accurately in asynchronous DS/CDMA systems using neural networks./ The general spectral based techniques, such as MUSIC and ESPRIT, were simulated and analyzed. In order to estimate accurately using these methods the number of sources should be less than the number of antenna elements in the array. In addition, they cannot be operated in multipath environments. The processing power requirement of spectral based techniques and parametric based techniques is high to be operated in real time. These conditions disqualify the techniques, to operate in DS/CDMA systems. The techniques, which have been developed for DS/CDMA systems, were analyzed. Generally, most of the algorithms rely on information such as, complex attenuating factors, synchronizing information of all users, including themultipaths. In addition, they heavily rely on the Gaussian distribution of MAI, which is not a realistic assumption in dominating MAI environments. As a solution to these, a new analytical and training combined method is proposed in this thesis./ The signal rcccived at the antenna array contains the DOA information of the desired signal, MAI and Gaussian noise, and the DOA is extracted by mitigating the MAI and noise components. This is performed in three stages: an initial temporal processing stage followed by a spatial or antenna array processing stage and a final NN stage. The MAI is reduced at all three stages while the Gaussian noise is reduced mainly at spatial processing and the NN stages. All three stages use non-complex techniques and therefore the algorithm is computationally very efficient./ Using a 6-element isotropic antenna array, the system was simulated under different environmental conditions such as varying signal to noise ratios, varying multipaths and for untrained sources and no assumptions were made unlike in the simulations of the previous workers. The arrival of a signal is first detected within a 10° sector and then the exact direction is estimated with a very high accuracy using the estimation NN. A new preprocessing technique is proposed which leads for a small training data set and a training and generalizing time. The results arc very promising and the mathematical reasoning supports them.
item: Thesis-Abstract
An Electrical parametric model of human skin and blood glucose spectroscopy
(2014-06-05) Wanasinghe, TR; Kulasekere, EC
Diabetes is well known as a leading cause of death all around the world. Mainly, invasive methods are used for blood glucose monitoring in the current context. The monitoring is done either as an inpatient procedures or using home based measuring devices. Invasive or minimally invasive methods make it di_cult when it comes to frequent measurements required by diabetes patients. It also has other issues such as the associated pain, phobia, and the spread of diseases like AIDS. These issues are heightened in the case of home based monitoring devices. As a result many researchers have attempted to introduce non-invasive measuring techniques for home based glucose monitoring devices. However none of then have met the accuracy requirements for medical use. Dielectric spectroscopy (DS) is one such methods which has been proposed for non-invasive glycaemia monitoring. In DS, the variation of skin impedance has been used to derive an index representing blood glucose uctuation. As a re- sult of the lack of knowledge of the impedance characteristics of the skin and the tissue underneath, and its relation to the level of blood glucose, the consistency and accuracy of the measurements are questionable. The ensuing research pro- poses a theoretical framework for skin impedance variations with the blood glucose level and also provides experimental veri_cation of the same. This research also proposes an electrical parametric (impedance) model for human skin and blood glucose spectroscopy which consists of human skin, electrode-electrolyte interface and coupling capacitance between transmitter and receiver. Such a mathematical model of the physiological system will enable us to further analyze the relationship the physiological parameters have with the uctuation of the blood glucose levels for di_erent individuals. Moreover, the thesis analyzes the inuence from bio-sensor to sensitivity mea- surements and proposes a concentric annular ring slot antenna (CARSA) as a possible sensor for non-invasive blood glucose measurement via DS. Compared to early research of Cada_ et al. [1], CARSA showed a 13 fold increment of the measurement sensitivity. Further, it could be seen that, this sensitivity increment was 40 fold when the e_ective length of CARSA decreases from 10 cm to 6.5 cm. The thesis further highlights the importance of careful design of this sensor and proposes a rigorous mathematical model of its derivation.
item: Thesis-Full-text
Enhancing the Wi-Fi Direct protocol for Vehicular Ad-hoc Networks
Manamperi, WN; Samarasinghe, T; Dias, D
We present a technique for enhancing Wi-Fi Direct (WD) for vehicular environments. Dedicated short range communication (DSRC) has been standardized for communication in Intelligent Transportation Systems (ITS). However, due to high costs at initiation, alternative communication strategies are of interest in order to facilitate the quick deployment of ITSs. WD, which is a relatively mature technology available in mobile devices, has come across as a possible alternate candidate. However, the presence of large communication delays in the WD protocol stack is a shortcoming in deploying this in highly dynamic vehicular scenarios. The objective of our work is to propose and evaluate a method to overcome some of the large transmission delays in WD. Our proposal is to use a broadcast mechanism in the downlink between the group owner (GO) and the clients of a WD group, as an alternative to the currently used peer-to-peer (P2P) method. We study our technique by simulating a bi-directional highway scenario with multiple lanes. We set up the vehicular channel model using two well-known models: Friis propagation model and the Nakagami fading model. Performance measures such as average total delay, average energy consumption of the GO, average packet loss ratio, and average packet reception ratio are presented. While the proposed GO Broadcast method reduces the downlink delay, it increases the probability of packet losses due to the lack of retransmissions. Our results demonstrate a gain in terms of average total delay and the average energy consumption of the GO. We use a theoretical analysis as well as a simulation study using OMNeT-r-K It is also shown that the degradation in performance on the downlink due to packet losses is within tolerable limits, given that the size of the group is selected properly.
item: Thesis-Abstract
High performance parallel packet classification architecture with popular rule caching
(2015-07-09) Lakshitha, OGS; Pasqual, AA
As the Internet evolves novel services and applications are being introduced which require di erent levels of Quality of Service or non best e ort service for proper functionality. Thus, there is a requirement for future networking equipment to distinguish between tra c ows belonging to di erent applications. The enabling function for such di erentiation is multi eld packet classi cation. Traditional software and hardware approaches to multi eld Packet Classi cation are being challenged due to the exponential growth of internet tra c and data rates. Cur- rent growth rates of silicon technologies will not be able to handle the growth rates of Internet tra c, data rates, and rule database storage requirements in the future. Even though many research have been done in this area, packet classi- cation technologies that support scalability in both line rates and rule sets is scarce. We try to address these issues through a hardware architectural approach for packet classi cation. We identify that classifying multiple packet streams simul- taneously by utilizing immense parallelism o ered by modern hardware technolo- gies while sharing a common rule database among several packet classi cation modules is the solution to the ever widening gap between Internet data rates and silicone speeds. Main contribution of this work is design and implementation of a packet classi cation architecture which has following characteristics: scalability in terms of both throughput and number of rules, capability of classifying parallel packet streams simultaneously, capability of using temporal locality of Internet tra c to increase the classi cation throughput by identifying classi cation rules which are popular among incoming packets and caching them in private caching entities in classi cation modules to avoid contentions at the shared rule database. Simulation results revealed that proposed architecture is capable of achieving a throughput of more than 200Gbps for worst case packet size of 40 bytes. Proposed architecture was implemented on NetFPGA platform and the classi cation was done at full line rate.
item: Thesis-Abstract
Intelligent Control of Distributed Decision Agents
(2016-05-25) Jayakody, SA; Kulasekere, EC
Advances in technology have enabled the manufacturing of massive numbers of deployable computing agents with integrated sensors and actuators. Networked multiple distributed agents in a remote environment will enable distinct event sensing, and information dissemination. Such a collection of deployed agents can perform as a distributed micro sensor network, which cooperates to solve at least one common application. The basic building block of such a network is its deployable agents, and those are considered to be autonomous, unreliable, and irregular in orientation. The interconnections are unknown and assembled in an ad hoc manner. Hence, intelligent control and expected dynamics in the system present unique challengers in the system design. This research presents an approach to organize an unstructured collection of autonomous agents into a cooperative sensor network spontaneously. Furthermore, intelligent control is achieved through instantly populated set of searching agents, followed by natural biological Ant systems. A set of independent searching agents called ants cooperate to find distinct sensor-events with the shortest possible routes concurrently. Ants cooperate using an indirect form of communication mediated by pheromone. Ants update pheromone on the edges of the network as local variables while they are in parallel search. This allows multiple users to sense distinct events simultaneously. Overall design minimizes total energy consumption and allows selfconfiguring, robust, and scalable sensor network design. Proposed framework simplifies coordination overhead of the network and facilitates the implementation of efficient, adaptive Ant based algorithm..
item: Thesis-Abstract
Investigation of multiuser detection algorithm for a space time coded MC-CDMA system
Sriyananda, MGS
Some of the critical and crucial barriers identified in the air interface of multiuser communication systems are multiuser detection, channel capacity and channel stability. These barriers are so significant and pivotal that the development has been solely obstructed by them in wireless sectors such as cellular mobile, wireless LANs and satellite communication systems. Space Time Trellis Coding is one of the prominent multiple-input multiple-output channel concepts which has been proposed for high data rate communication systems .This gives space diversity, temporal diversity and coding advantage, making the communication channel much more stable. MC-CDMA is a multiple access communication system designed to be operated in a multiuser environment, having the advantage of subcarrier frequency diversity. In this system, signal transmission and reception is based on the Fast Fourier Transform technique similar to the well known OFDM technology. This research is a combination of the above mentioned technologies. First the performance evaluation is done for a Space Time Trellis Coded (STTC) Frequency Domain Spreading Assisted Multicarrier COMA (FDSA MC-CDMA) system with a single user. Then it presents a multiuser detection scheme based on combining techniques that can be applied to a STTC FDSA MC-CDMA system, operated in a frequency selective slow fading channel. In the case of multiuser detection, for the purpose of better symbol recovery, multiple numbers of spreading codes are employed for a single user. One of the main combining techniques, namely Equal Gain Combining(EGC) is selected and tested as an example showing that the proposed detection scheme can be used or tested with any of the spreading code aided multiuser detection mechanisms. In addition to the initial detection, iterative based or multistage Parallel Interference Cancellation (PIC) is used to improve the performance of the receiver to indicate, how far this method is compatible with the existing receiver technologies. It gives clear evidence to the fact that the signal recovery can be further improved. Simulation results how the performance of the system, when it is operated with single, 2, 4, 8 and 16 users with iterations for the PIC.
item: Thesis-Full-text
Lightning warning system based on slow fields and fast transient variations, suitable for oceanic tropics
Abhayasinghe, KN; Kulasekara, EC
Lightning causes a lot of property and human damage all over Sri Lanka. It has been a major requirement to develop a low cost lightning warning system. The environmental vertical static electric field changes from 0.1 kVm-1 under fair weather conditions to extreme values like 10 kVm-1 under thunderstorm conditions. Also, lightning discharges generate electromagnetic radiation from ultra low frequency (ULF) through ultra high frequency (UHF) with peak energy emission at 10 kHz. The work discussed in this thesis uses both the static field variation and the electromagnetic radiation emitted by lightning discharges to predict a thunderstorm. A portable transient detector using an envelope detector tuned to 1600 kHz is used to detect electromagnetic radiation emitted by lightning discharges. An operational amplifier circuit having a slow response with a horizontal plate antenna is used to detect the static field variation. Final decision is made by a third circuit and three levels of alarms are released accordingly. Using the transient detector only, a warning can be released 25 minutes before the close by thunderstorm with 95% level of confidence. With the entire system, the confidence of the warning further increases. The cost of the transient detector is about 2500 Sri Lankan rupees with a rechargeable battery bank. The entire system with a battery backup costs about 5000 Sri Lankan rupees. According to the observations made by the transient detector the delay between cloud flashes and ground flashes shows a distribution of the form of a fractional function with a maximm at 27.52 minutes. The newly designed lightning warning system shows an acceptable grade of performance with its low cost.
item: Thesis-Abstract
Multiple degree of freedom stereo camera platform for active vision : design of an instruction set architecture and a processor architecture for related calculations
Sumanasena, MGB
Vision or visual perception is the most, prominent moans of observation in human beings and primates. The potential of visual perception has caused a substantial research effort to be put in to machine vision. But still, harnessing the full power of vision is only a fiction than reality. The main reason for this is the over whelming amount of information and complexity that has to be handled. In this context the concept of active vision has attracted t he interest of researchers. An active vision system can be defined as a system capable of manipulating its visual parameters in order to extract useful information about the scene. The main contribution of the this work is the creation of 7 degrees of freedom binocular camera platform with its own optimized FPGA based controller. The objective is to use the created platform to further the knowledge-base in active vision. It consists of two eye modules and a neck module where the two eyes are mounted. The system is able to look at. a particular point in space at a given time and to trace a given trajectory. The camera platform has three degrees of freedom in its neck and two degrees of freedom in its each eye. Stepper motors are used to drive all the degrees of freedom. Stepper motors are used in a closed loop control system with sequential optical encoders to provided feedback information 011 position. Custom built gearwheels are used to increase the torque provided by the motors. since a large number of inputs and outputs have to be handled in parallel and the architecture can be optimized for the types of mathematical calculations required, a FPGA based microprocessor was developed to control the Stereo Camera Platform .it interprets the instructions given by the user and calculates, the angle of rotation for individual degrees of freedom, and the required acceleration. The generation of pulses to drive the stepper motors is also done by the controller. Optical encoder feed back was used by the controller t o correct any error resulting from, step missing of stepper motors or backslash of gear trains. Results show that the velocity profiles, of individual degrees of freedom quite closely follow the expected velocity profiles. The deviations may be due to mechanical deficiencies like uneven friction, and eccentric ness of gear wheels and shafts.
item: Thesis-Abstract
Multiple Degree of Freedom Stereo Camera Platform for Active Vision Designing the Core Architecture of the Processor
(2016-05-18) Samarawickrama, JG; Pasqual, AA
Vision is our most powerful sense. It provides us remarkable amount of information about our surrounding and enables us to interact intelligently with the environment, all without direct physical contact. Vision is also our most complicated sense. The knowledge we have accumulated about how biological vision systems operate is still fragmentary. Nature has proven to be capable of creating versatile and flexible vision systems, which are much more efficient than all artificial vision systems already designed. Therefore, the comprehension of some of the biological principles of vision has brought important ideas and concepts for the development of computational vision. One of the main goals of the research is to develop a high-performance stereo active vision head ,that can be used for studying human vision. The head consists of two eye modules and a neck module on which the two eyes are mounted. The camera platform has a total number of seven degrees of freedom, three in its neck and two in its each eye. Stepper motors with custom built gear wheels are used to drive all the degrees of freedom and the motors are used in a closed loop control system with sequential optical encoders for providing position feedback. This research also focuses on implementing an FPGA (Field Programmable Gate Array) based microprocessor that interprets the instructions given by the user, calculates all the necessary parameters for driving the motors as required and controls the motors accordingly. This stand alone processor includes several floating-point units operating in parallel with the other motor control units. A total no of five floating point operations can be done in parallel that consists of 4 addition( or subtraction) and one multiplication( or division)operations. In addition, a CORDIC processor also runs in parallel to calculate trigonometric functions and root squares. With altogether the processor gives grater improvement to the performance in terms of speed exploiting parallelism. The results show that the FPGA based microprocessor for controlling the multi degree of freedom stereo vision head is very efficient for active vision.
item: Thesis-Full-text
On Demand deployment of UAV base stations in wireless communication networks
(2022) Hassaan MHM; Hemachandra K T; Samarasinghe TN; Jayakody DNK
Unmanned aerial vehicles (UAVs)-assisted communication systems are considered a promising technology in diverse verticals. The objective of this research is to study on demand deployment of UAVs in special applications. We analyze the multi-UAV deployment in two di erent scenarios. First, we analyze the deployment of UAVs as an aerial base stations (ABSs) to provide cellular coverage to isolated users. The main contributions of this study includes a less complex approach to optimally position the UAVs and assigning user equipment (UE) to each ABS, such that the total spectral e ciency (TSE) of the network is maximized, while maintaining a minimum QoS requirement for the UEs. The main advantage of the proposed approach is that it only requires the knowledge of UE and ABS locations and statistical channel state information. We propose two approaches with common and diverse altitude selection. Both approaches lead up to approximately 8-fold energy savings compared to ABS placement using a naive exhaustive search. Second, we have investigated the deployment of UAVs in wireless sensor network (WSN) systems. Considering the energy-constrained nature of the WSN, we have proposed a multi-UAV deployment algorithm that minimizes the maximum power transmitted among the sensor nodes (SN) for given data rate and altitude constraints. The problem is divided into three subproblems in order to reduce the complexity. Each subproblem is optimized by xing other parameters as constant. Finally, we proposed a joint optimization algorithm that combines the approaches of all three subproblems. In the joint optimization, the rst and second subproblems are iteratively solved together while third subproblem is solved independently for each UAV. Moreover, the joint optimization gives the minimum number of UAVs required to serve all the SNs with the given constraints. The results indicate a signi cant performance gain compared to the benchmark methods in terms of the number of iterations for convergence, maximum transmission power requirement and the minimum number of UAV requirements.