An Investigation of Decoding Complexity and Coding Rate Performance of Raptor Codes

This thesis examines two aspects of wireless transmissions using Raptor codes: (i) decoding complexity and (ii) rate performance. First, observing that the high complexity of Raptor decoding process is mainly due to the required number of decoding attempts, a strategy is proposed to reduce the decoding complexity by choosing an appropriate time to start the first decoding attempt and thus keeping a small number of decoding attempts. Simulations results show that the proposed strategy, when combined with a decoding algorithm, can achieve a significant reduction in Raptor decoding complexity. Another threshold strategy is also investigated, aiming to further reduce the decoding complexity by providing only "reliable" bits for Raptor decoding process. The effect of this considered strategy can be interpreted as simulating a better transmission channel and techniques to estimate its effective channel quality improvement are developed and evaluated. Second, the Raptor coding rate performance over Nakagami-m fading channels and in a cooperative relaying network using Binary Phase Shift Keying (BPSK) is studied. The simulation results show that the Raptor-coded BPSK scheme can provide a transmission rate closely approaching the channel capacity for different fading conditions at low SNR. For cooperative relaying network using Raptor-coded BPSK scheme, two cooperative protocols are considered: the existing Time Division (TD) and the modified Phase-2 Simultaneous Transmission (PST). Their performance is investigated in terms of average time and energy required for a successful transmission under various conditions of the Relay-Destination (RD) link. The simulation results show that the PST protocol often outperforms the TD protocol in terms of average transmission time and the TD protocol only has lower average transmission energy when the RD link's quality is better that of the Source-Destination (SD) link

OPERATING SYSTEM FOR WIRELESS SENSOR NETWORKS AND AN EXPERIMENT OF PORTING CONTIKIOS TO MSP430 MICROCONTROLLER

Wireless Sensor Networks (WSNs) consist of a large number of sensor nodes, and are used for various applications such as building monitoring, environment control, wild-life habitat monitoring, forest fire detection, industry automation, military, security, and health-care. Each sensor node needs an operating system (OS) that can control the hardware, provide hardware abstraction to application software, and fill in the gap between applications and the underlying hardware. In this paper, researchers present OS for WSNs and an experiment of porting contikiOS to MSP430 microcontroller which is very popular in many hardware platforms for WSNs. Researchers begin by presenting the major issues for the design of OS for WSNs. Then, researchers examine some popular operating systems for WSNs including TinyOS, ContikiOS, and LiteOS. Finally, researchers present an experiment of porting ContikiOS to MSP430 microcontroller. Wireless Sensor Networks (WSNs) terdiri dari sejumlah besar sensor nodes, dan digunakan untuk berbagai aplikasi seperti pemantauan gedung, pengendalian lingkungan, pemantauan kehidupan habitat liar, deteksi kebakaran hutan, otomatisasi industri, militer, keamanan, dan kesehatan. Setiap sensor nodememerlukan sistem operasi (SO) yang dapat mengontrol hardware, menyediakan abstraksi hardware untuk aplikasi perangkat lunak, dan mengisi kesenjangan antara aplikasi dan hardware. Dalam penelitian ini, peneliti menyajikan SO untuk WSNs dan percobaan dari port contikiOS untuk MSP430 mikrokontroler yang sangat populer di platformhardware untuk WSNs. Peneliti memulai dengan menghadirkan isu utama yaitu desain SO untuk WSNs. Lalu, penelitimemeriksa beberapa sistem operasi populer untuk WSNs, termasuk TinyOS, ContikiOS, dan LiteOS. Akhirnya penelitimenyajikan sebuah percobaan dari port ContikiOS untuk MSP430 mikrokontroler

Dynamics of IUD use in Vietnam: implications for family planning services at primary health care level

This study describes the dynamics of intrauterine device (IUD) use in Vietnam and implications for family planning services. A retrospective study was conducted among women who received IUD services in 2006–2009 at six commune health stations in three provinces. Women were interviewed about IUD use and switching behaviors. Of 1316 participants, 12.1% had discontinued IUD use at 12 months after insertion, 19.4% at 24 months, and 26.9% at 36 months. The highest rates of discontinuation were among older women and farmers/manual workers. Among 434 women who had an IUD removed, 49% cited health concerns as the main reason. Following removal, 70% switched to another contraceptive method (n = 306); of these, 15% switched to withdrawal, and 12% waited >2 months before adopting a new method. Dissatisfaction with IUD services was associated with high rates of discontinuation. Early discontinuation, delays in adopting new methods, and switching to withdrawal may contribute to unintended pregnancy among commune health station users in Vietnam

IMPROVED SEPTIC TANK, A PROMISING DECENTRALIZED WASTEWATER TREATMENT ALTERNATIVE IN VIETNAM

Joint Research on Environmental Science and Technology for the Eart

SUCCESSFUL IMPLEMENTATION OF FULL-SCALE BAFFLED SEPTIC TANK WITH ANAEROBIC FILTERS FOR WASTEWATER TREATMENT IN VIETNAM

Joint Research on Environmental Science and Technology for the Eart