A data link layer protocol for hybrid vehicular sensor networks using practical mobility models with real maps

Safety applications in Hybrid Vehicular Sensor Networks (HVSN) require robust transmission of messages in order to deliver safety to roads and drivers as intended. Since moving vehicles are equipped with wireless sensors that utilize and share the unreliable wireless channel for communication, the transmission of safety messages must be coordinated to minimize or completely eliminate collision of exchanged packets. The first step on the way of achieving that is through the Media Access Control (MAC) layer which is responsible for managing the access to the shared media safely and without collisions. This thesis aims at designing and implementing a HVSN MAC protocol to help exchange safety and control messages between the network elements, i.e. vehicles\u27 on board sensors and road side sensor units. The Time Division Multiple Access (TDMA) is one of the media access techniques used for eliminating collisions. However, it imposes few challenges in implementation, namely, rescheduling and time synchronization among communicating nodes. In this proposed protocol, we provide a complete solution for such problems. Instead of dividing the time frame between just the available nodes, the protocol provides fixed schedules or time frames with enough time slots that are able to accommodate the maximum number of vehicles that may fit in one segment at a time. Such arrangement eliminates the need for re-scheduling and unnecessary processing. The synchronization problem is solved as well, with coordination from the network controller which is the road side unit. Since we are dealing with HVSN, the protocol has not only considered the network or the communication part, but also included the vehicles\u27 behavior in the design process, through realistic mobility modeling. The mobility model and the protocol operations are employed on a small real map where vehicles interact and communicate. Moreover, a new Packet Delivery Ratio calculation method that considers the vehicles\u27 mobility in the analysis is applied to practically evaluate the protocol performance. The devised MAC protocol is characterized by several features; first, it is a collision free MAC protocol that does not require the re-configuration of time slots division as well as it accounts for the time synchronization problem. Second, the protocol is one of the initial works that employs the IEEE 802.11 p in HVSN and utilizes its features and specifications. Third, the design is comprehensive and it is built and based on a realistic mobility model that helped in assessing the protocol performance through a unique TDMA mobility based-PDR calculation metho

Protocol stacks for power-aware wireless microsensor networks

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 71-72).In a distributed wireless sensor system, a need to prolong the lifetime of the network is crucial and limited by battery capacity. As communication traffic among sensor nodes is triggered by sensing events, the network can exploit these time-varying scenarios to obtain power savings by adjusting its operating conditions accordingly. A coherent design of application-specific network protocol stacks is the key. Specifically, embedding power aware features in the link layer and media access control (MAC) layer promises to extend the lifetime of the sensor network. The power-aware design will be illustrated on [mu]AMPS sensor node prototypes. With the integrated design framework, lower layers of the network stack provides configurable power-aware features to be controlled by higher network layers that maintain broaderview knowledge of the environment. TDMA has been chosen as a MAC Layer protocol for its inherited power-aware mechanism of radio shutdowns outside its TDMA slot and in absence of sensing events. Another level of power-aware features can be deployed in MAC ID and TDMA slot assignments. In a field of scattered sensor nodes, not all the nodes are in radio range of one another or of the base station. Hence, assigning N TDMA slots for the network of N sensor nodes that are not all in radio range will waste the receiver energy and link bandwidth. An algorithm for a re-use of MAC ID and MAC time slot is proposed based on the number of neighboring nodes. Hence, varying the number of neighboring nodes by varying the transmit power can optimize the system lifetime and bandwidth. An implementation of the Link and MAC infrastructure is completed. Power scalability is illustrated on [mu]AMPS node prototypes, with TDMA Media Access and a vehicle tracking application demonstration.by Phanaphat Piyada.M.Eng

A Study of Medium Access Control Protocols for Wireless Body Area Networks

The seamless integration of low-power, miniaturised, invasive/non-invasive lightweight sensor nodes have contributed to the development of a proactive and unobtrusive Wireless Body Area Network (WBAN). A WBAN provides long-term health monitoring of a patient without any constraint on his/her normal dailylife activities. This monitoring requires low-power operation of invasive/non-invasive sensor nodes. In other words, a power-efficient Medium Access Control (MAC) protocol is required to satisfy the stringent WBAN requirements including low-power consumption. In this paper, we first outline the WBAN requirements that are important for the design of a low-power MAC protocol. Then we study low-power MAC protocols proposed/investigated for WBAN with emphasis on their strengths and weaknesses. We also review different power-efficient mechanisms for WBAN. In addition, useful suggestions are given to help the MAC designers to develop a low-power MAC protocol that will satisfy the stringent WBAN requirements.Comment: 13 pages, 8 figures, 7 table

Distributed Time-Frequency Division Multiple Access Protocol For Wireless Sensor Networks

It is well known that biology-inspired self-maintaining algorithms in wireless sensor nodes achieve near optimum time division multiple access (TDMA) characteristics in a decentralized manner and with very low complexity. We extend such distributed TDMA approaches to multiple channels (frequencies). This is achieved by extending the concept of collaborative reactive listening in order to balance the number of nodes in all available channels. We prove the stability of the new protocol and estimate the delay until the balanced system state is reached. Our approach is benchmarked against single-channel distributed TDMA and channel hopping approaches using TinyOS imote2 wireless sensors.Comment: 4 pages, IEEE Wireless Communications Letters, to appear in 201

Katakan tidak pada rasuah

Isu atau masalah rasuah menjadi topik utama sama ada di peringkat antarabangsa mahupun di peringkat dalam negara. Pertubuhan Bangsa- bangsa Bersatu menegaskan komitmen komuniti antarabangsa bertegas untuk mencegah dan mengawal rasuah melalui buku bertajuk United Nations Convention against Corruption. Hal yang sama berlaku di Malaysia. Melalui pernyataan visi oleh mantan Perdana Menteri Malaysia, Tun Dr. Mahathir bin Mohamed memberikan indikasi bahawa kerajaan Malaysia komited untuk mencapai aspirasi agar Malaysia dikenali kerana integriti dan bukannya rasuah. Justeru, tujuan penulisan bab ini adalah untuk membincangkan rasuah dari beberapa sudut termasuk perbincangan dari sudut agama Islam, faktor-faktor berlakunya gejala rasuah, dan usaha-usaha yang dijalankan di Malaysia untuk membanteras gejala rasuah. Perkara ini penting bagi mengenalpasti penjawat awam menanamkan keyakinan dalam melaksanakan tanggungjawab dengan menghindari diri daripada rasuah agar mereka sentiasa peka mengutamakan kepentingan awam

Self-stabilizing TDMA Algorithms for Wireless Ad-hoc Networks without External Reference

Time division multiple access (TDMA) is a method for sharing communication media. In wireless communications, TDMA algorithms often divide the radio time into timeslots of uniform size, $\xi$, and then combine them into frames of uniform size, $\tau$. We consider TDMA algorithms that allocate at least one timeslot in every frame to every node. Given a maximal node degree, $\delta$, and no access to external references for collision detection, time or position, we consider the problem of collision-free self-stabilizing TDMA algorithms that use constant frame size. We demonstrate that this problem has no solution when the frame size is $\tau < \max\{2\delta,\chi_2\}$, where $\chi_2$ is the chromatic number for distance-$2$ vertex coloring. As a complement to this lower bound, we focus on proving the existence of collision-free self-stabilizing TDMA algorithms that use constant frame size of $\tau$. We consider basic settings (no hardware support for collision detection and no prior clock synchronization), and the collision of concurrent transmissions from transmitters that are at most two hops apart. In the context of self-stabilizing systems that have no external reference, we are the first to study this problem (to the best of our knowledge), and use simulations to show convergence even with computation time uncertainties

Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View

Small satellite systems enable whole new class of missions for navigation, communications, remote sensing and scientific research for both civilian and military purposes. As individual spacecraft are limited by the size, mass and power constraints, mass-produced small satellites in large constellations or clusters could be useful in many science missions such as gravity mapping, tracking of forest fires, finding water resources, etc. Constellation of satellites provide improved spatial and temporal resolution of the target. Small satellite constellations contribute innovative applications by replacing a single asset with several very capable spacecraft which opens the door to new applications. With increasing levels of autonomy, there will be a need for remote communication networks to enable communication between spacecraft. These space based networks will need to configure and maintain dynamic routes, manage intermediate nodes, and reconfigure themselves to achieve mission objectives. Hence, inter-satellite communication is a key aspect when satellites fly in formation. In this paper, we present the various researches being conducted in the small satellite community for implementing inter-satellite communications based on the Open System Interconnection (OSI) model. This paper also reviews the various design parameters applicable to the first three layers of the OSI model, i.e., physical, data link and network layer. Based on the survey, we also present a comprehensive list of design parameters useful for achieving inter-satellite communications for multiple small satellite missions. Specific topics include proposed solutions for some of the challenges faced by small satellite systems, enabling operations using a network of small satellites, and some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications Surveys and Tutorial

A critical analysis of research potential, challenges and future directives in industrial wireless sensor networks

In recent years, Industrial Wireless Sensor Networks (IWSNs) have emerged as an important research theme with applications spanning a wide range of industries including automation, monitoring, process control, feedback systems and automotive. Wide scope of IWSNs applications ranging from small production units, large oil and gas industries to nuclear fission control, enables a fast-paced research in this field. Though IWSNs offer advantages of low cost, flexibility, scalability, self-healing, easy deployment and reformation, yet they pose certain limitations on available potential and introduce challenges on multiple fronts due to their susceptibility to highly complex and uncertain industrial environments. In this paper a detailed discussion on design objectives, challenges and solutions, for IWSNs, are presented. A careful evaluation of industrial systems, deadlines and possible hazards in industrial atmosphere are discussed. The paper also presents a thorough review of the existing standards and industrial protocols and gives a critical evaluation of potential of these standards and protocols along with a detailed discussion on available hardware platforms, specific industrial energy harvesting techniques and their capabilities. The paper lists main service providers for IWSNs solutions and gives insight of future trends and research gaps in the field of IWSNs