Master of Science in Electronics & Telecommunications

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

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Browsing Master of Science in Electronics & Telecommunications by Subject "ELECTRONIC AND TELECOMMUNICATION - Thesis"

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    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
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    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
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    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
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    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.