Data distribution satellite

A description is given of a data distribution satellite (DDS) system. The DDS would operate in conjunction with the tracking and data relay satellite system to give ground-based users real time, two-way access to instruments in space and space-gathered data. The scope of work includes the following: (1) user requirements are derived; (2) communication scenarios are synthesized; (3) system design constraints and projected technology availability are identified; (4) DDS communications payload configuration is derived, and the satellite is designed; (5) requirements for earth terminals and network control are given; (6) system costs are estimated, both life cycle costs and user fees; and (7) technology developments are recommended, and a technology development plan is given. The most important results obtained are as follows: (1) a satellite designed for launch in 2007 is feasible and has 10 Gb/s capacity, 5.5 kW power, and 2000 kg mass; (2) DDS features include on-board baseband switching, use of Ku- and Ka-bands, multiple optical intersatellite links; and (3) system user costs are competitive with projected terrestrial communication costs

Time Driven Priority Router Implementation and First Experiments

This paper reports on the implementation of Time-Driven Priority (TDP) scheduling on a FreeBSD platform. This work is part of a TDP prototyping and demonstration project aimed at showing the implications of TDP deployment in packet-switched networks, especially benefits for real-time applications. This paper focuses on practical aspects related to the implementation of the technology on a Personal Computer (PC)-based router and presents the experimental results obtained on a testbed network. The basic building blocks of a TDP router are described and implementation choices are discussed. The relevant results achieved and here presented can be categorized into two types: qualitative results, including the successful integration of all needed blocks and the insight obtained on the complexity related to the implementation of a TDP router, and quantitative ones, including measures of achievable network utilization and of jitter experienced on a fully-loaded TDP network. The outcome demonstrates the effectiveness of the presented implementation while confirming TDP points of strengt

Concurrent cell rate simulation of ATM telecommunications network.

PhDAbstract not availabl

Pendekatan konstruktif dalam inovasi pengajaran dan pembelajaran Bahasa Melayu di Kolej Vokasional

Pendekatan konstruktif adalah pendekatan pengajaran dan pembelajaran yang berpusatkan pelajar manakala inovasi pengajaran pula dikaitkan dengan kaedah pengajaran yang terbaru demi mengukuhkan pemahaman pelajar. Pembelajaran berasaskan pendekatan konstruktif merupakan elemen yang penting dan perlu difahami oleh guru-guru bagi memantapkan proses pengajaran dan pembelajaran sesuai dengan peredaran masa dan menjayakan proses tranformasi pendidikan negara. Objektif kajian ini dijalankan untuk mengenal pasti pemahaman guru-guru bahasa Melayu berkaitan inovasi, mengenal pasti perbezaan yang wujud antara guru lelaki dan guru perempuan dalam mengamalkan inovasi, pengkaji juga melihat adakah wujud perbezaan antara guru baru dan guru yang sudah berpengalaman dalam aspek mengaplikasikan inovasi serta mengenal pasti kekangan-kekangan yang dialami oleh para guru untuk mengaplikasikan inovasi di sekolah. Seramai 63 orang guru bahasa Melayu dari lapan buah kolej vokasional telah dipilih sebagai responden dalam kajian ini. Data dianalisis menggunakan perisian Winsteps 3.69.1.11 dengan pendekatan Model Pengukuran Rasch. Hasil analisis menunjukkan bahawa guru�guru bahasa Melayu memahami kepentingan inovasi dalam pengajaran dan pembelajaran. Hasil kajian juga menunjukkan guru-guru perempuan lebih banyak menerapkan unsur inovasi dalam pengajaran berbanding guru lelaki. Walaupun begitu, aspek pengalaman tidak menunjukkan perbezaan dari segi pengamalan inovasi sama ada guru baru ataupun guru yang sudah berpengalaman. Pengkaji juga mengenal pasti beberapa kekangan yang dialami oleh guru-guru untuk mengamalkan inovasi ini. Sebagai langkah untuk menangani masalah berkenaan, beberapa cadangan telah dikemukakan oleh pengkaji bagi memastikan guru-guru dapat merealisasikan proses pengajaran berkesan dengan penerapan inovasi mengikut model pendekatan konstruktif. Pengkaji berharap, kajian ini dapat dijadikan sebagai satu panduan kepada pelaksana kurikulum bagi memastikan budaya inovasi sentiasa menjadi amalan dalam kalangan guru demi mengangkat profesionalisme guru di Malaysia

Lessons learned from the design of a mobile multimedia system in the Moby Dick project

Recent advances in wireless networking technology and the exponential development of semiconductor technology have engendered a new paradigm of computing, called personal mobile computing or ubiquitous computing. This offers a vision of the future with a much richer and more exciting set of architecture research challenges than extrapolations of the current desktop architectures. In particular, these devices will have limited battery resources, will handle diverse data types, and will operate in environments that are insecure, dynamic and which vary significantly in time and location. The research performed in the MOBY DICK project is about designing such a mobile multimedia system. This paper discusses the approach made in the MOBY DICK project to solve some of these problems, discusses its contributions, and accesses what was learned from the project

ATM network impairment to video quality

Includes bibliographical reference

Cost-Effective and Energy-Efficient Techniques for Underwater Acoustic Communication Modems

Finally, the modem developed has been tested experimentally in laboratory (aquatic environment) showing that can communicates at different data rates (100..1200 bps) compared to state-of-the-art research modems. The software used include LabVIEW, MATLAB, Simulink, and Multisim (to test the electronic circuit built) has been employed.Underwater wireless sensor networks (UWSNs) are widely used in many applications related to ecosystem monitoring, and many more fields. Due to the absorption of electromagnetic waves in water and line-of-sight communication of optical waves, acoustic waves are the most suitable medium of communication in underwater environments. Underwater acoustic modem (UAM) is responsible for the transmission and reception of acoustic signals in an aquatic channel. Commercial modems may communicate at longer distances with reliability, but they are expensive and less power efficient. Research modems are designed by using a digital-signal-processor (DSP is expensive) and field-programmable-gate-array (FPGA is high power consuming device). In addition to, the use of a microcontroller is also a common practice (which is less expensive) but provides limited computational power. Hence, there is a need for a cost-effective and energy-efficient UAM to be used in budget limited applications. In this thesis different objectives are proposed. First, to identify the limitations of state-of-the-art commercial and research UAMs through a comprehensive survey. The second contribution has been the design of a low-cost acoustic modem for short-range underwater communications by using a single board computer (Raspberry-Pi), and a microcontroller (Atmega328P). The modulator, demodulator and amplifiers are designed with discrete components to reduce the overall cost. The third contribution is to design a web based underwater acoustic communication testbed along with a simulation platform (with underwater channel and sound propagation models), for testing modems. The fourth contribution is to integrate in a single module two important modules present in UAMs: the PSK modulator and the power amplifier