2 dimension woven kenaf reinforced unsaturated polyester composite

In recent years, natural fiber from vegetables such as hemp, sisal, ramie, jute and kenaf has been recognized and studied by many researchers due to its potential as an alternative material for synthetic fibers in composite application. Kenaf fiber is a potential reinforced material for composite due to its acceptable properties and supported by the development in Malaysian Kenaf cultivation. Previous studies have demonstrated that Kenaf fibers were recognized in several applications such as automotive component, panel board, packaging, filter material and industrial paper. However, the reinforcement of the fibers is in random, unidirectional and particle form. Therefore, this research is focusing on the composites woven structural preform from the kenaf fiber assisted with the use of internal geometry modeling for optimization. The effect of primary parameters, which are the yarns properties, the fabric count and the weave designs were evaluated on it physical and mechanical properties. Different woven design preform (plain, twill 4/4, satin 8/3 and basket 4/4) were fabricated using floor loom and infused with unsaturated polyester resin using vacuum infusion process. The mechanical properties of the composites were measured and showed that satin 8/3 has highest tensile strength of 39MPa and Plain has highest tensile modulus of 2.63GPa, with flexural strength and impact strength of 48MPa and 29kJ/m2 respectively. The use of VIP and UPE show a good infusion of resin between intra yarns but need much lower viscosity on the UPE for inter yarns. The used of 5% sodium hydroxide solution with the application of tension during the treatment enhanced the composite strength of 12%. The stacking sequence and orientation of 0⁰ ,45⁰,0⁰ of the laminate composite had increased the flexural strength and impact strength of 73MPa and of 82MPa respectively. It is recommended to use a plain and satin structure for better infusion in vacuum infusion proces

QoS in LEO satellite networks with multipacket reception

Dissertação apresentada para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaLow Earth Orbit (LEO) satellite networks can improve terrestrial wireless networks to allow global broadband services for Mobile Terminals (MT), regardless of the users' location. In this context, hybrid telecommunication systems combining satellites with Long Term Evolution (LTE) networks, like the LightSquared technology, are intended to provide ubiquitous high-speed services. This dissertation analyses the performance of a random access protocol that uses Hybrid Network-assisted Diversity Multiple Access (H-NDMA), for a LEO satellite system network, named by Satellite Random NDMA (SR-NDMA). The protocol also considers a Single Carrier-Frequency Domain Equalization (SC-FDE) scheme for the uplink transmission and a Multipacket Reception (MPR) receiver. In this scenario, the transmission of data packets between MTs and the Base Station (BS) is made through random access and schedule access slots, organized into super-frames with the duration of a Round Trip Time (RTT). A SR-NDMA simulator is implemented to measure the system performance in matters of throughput, energy consumption, system delay and also the protocol capacity to meet Quality of Service (QoS) requirements. A set of simulations tests were made with a random Poisson process tra c generation to validate the analytical model. The capacity to ful l the QoS requirements of a real-time tra c class was also tested.FCT/MEC: MPSat - PTDC/EEA-TEL/099074/2008, OPPORTUNISTIC CR - PTDC/EEA-TEL/115981/2009, Femtocells - PTDC/EEA-TEL/120666/2010 e ADIN - PTDC/EEI-TEL/2990/201

Hybrid ARQ with parallel and serial concatenated convolutional codes for next generation wireless communications

This research focuses on evaluating the currently used FEC encoding-decoding schemes and improving the performance of error control systems by incorporating these schemes in a hybrid FEC-ARQ environment. Beginning with an overview of wireless communications and the various ARQ protocols, the thesis provides an in-depth explanation of convolutional encoding and Viterbi decoding, turbo (PCCC) and serial concatenated convolutional (SCCC) encoding with their respective MAP decoding strategies.;A type-II hybrid ARQ scheme with SCCCs is proposed for the first time and is a major contribution of this thesis. A vast improvement is seen in the BER performance of the successive individual FEC schemes discussed above. Also, very high throughputs can be achieved when these schemes are incorporated in an adaptive type-II hybrid ARQ system.;Finally, the thesis discusses the equivalence of the PCCCs and the SCCCs and proposes a technique to generate a hybrid code using both schemes

Investigation of Vertical Handoff Techniques in Integrated WLAN/Cellular Networks and Performance Analysis of Horizon Handoff in WiMax Networks

A thesis presented to the faculty of the College of Science and Technology at Morehead State University in partial fulfillment of the requirement for the Degree of Master of Science by Elaheh Arabmakki May 9, 2011

Proceedings of the Fifth International Mobile Satellite Conference 1997

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments

Application priority framework for fixed mobile converged communication networks

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The current prospects in wired and wireless access networks, it is becoming increasingly important to address potential convergence in order to offer integrated broadband services. These systems will need to offer higher data transmission capacities and long battery life, which is the catalyst for an everincreasing variety of air interface technologies targeting local area to wide area connectivity. Current integrated industrial networks do not offer application aware context delivery and enhanced services for optimised networks. Application aware services provide value-added functionality to business applications by capturing, integrating, and consolidating intelligence about users and their endpoint devices from various points in the network. This thesis mainly intends to resolve the issues related to ubiquitous application aware service, fair allocation of radio access, reduced energy consumption and improved capacity. A technique that measures and evaluates the data rate demand to reduce application response time and queuing delay for multi radio interfaces is proposed. The technique overcomes the challenges of network integration, requiring no user intervention, saving battery life and selecting the radio access connection for the application requested by the end user. This study is split in two parts. The first contribution identifies some constraints of the services towards the application layer in terms of e.g. data rate and signal strength. The objectives are achieved by application controlled handover (ACH) mechanism in order to maintain acceptable data rate for real-time application services. It also looks into the impact of the radio link on the application and identifies elements and parameters like wireless link quality and handover that will influence the application type. It also identifies some enhanced traditional mechanisms such as distance controlled multihop and mesh topology required in order to support energy efficient multimedia applications. The second contribution unfolds an intelligent application priority assignment mechanism (IAPAM) for medical applications using wireless sensor networks. IAPAM proposes and evaluates a technique based on prioritising multiple virtual queues for the critical nature of medical data to improve instant transmission. Various mobility patterns (directed, controlled and random waypoint) has been investigated and compared by simulating IAPAM enabled mobile BWSN. The following topics have been studied, modelled, simulated and discussed in this thesis: 1. Application Controlled Handover (ACH) for multi radios over fibre 2. Power Controlled Scheme for mesh multi radios over fibre using ACH 3. IAPAM for Biomedical Wireless Sensor Networks (BWSN) and impact of mobility over IAPAM enabled BWSN. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in multi radios over fibre performance in terms of application response delay and power consumption by upto 75% and 15 % respectively, reduction in traffic loss by upto 53% and reduction in delay for real time application by more than 25% in some cases

An Investigation On An Efficient Approach Of Improving Quality Of Service Of Voip Over Satellite

Kepentingan Protokol Suara Melalui Internet (VoIP) semakin diperakui oleh industri telekomunikasi. Sejak dekad yang lalu banyak perisian VoIP telah dibangunkan yang menawarkan banyak faedah kepada kedua-dua pembekal perkhidmatan rangkaian dan telekomunikasi. The importance of Voice over Internet Protocol (VoIP) is slowly being recognized by the telecommunications industry. In the past decade, many VoIP applications have been developed, offering a wide range of benefits to both telecommunications and network service providers