The Effects of Weather on the Life Time of Wireless Sensor Networks Using FSO/RF Communication

The increased interest in long lasting wireless sensor networks motivates to use Free Space Optics (FSO) link along with radio frequency (RF) link for communication. Earlier results show that RF/FSO wireless sensor networks have life time twice as long as RF only wireless sensor networks. However, for terrestrial applications, the effect of weather conditions such as fog, rain or snow on optical wireless communication link is major concern, that should be taken into account in the performance analysis. In this paper, life time performance of hybrid wireless sensor networks is compared to wireless sensor networks using RF only for terrestrial applications and weather effects of fog, rain and snow. The results show that combined hybrid network with three threshold scheme can provide efficient power consumption of 6548 seconds, 2118 seconds and 360 seconds for measured fog, snow and rain events respectively resulting in approximately twice of the life time with only RF link

Design and Analysis of Free Space Optical Sensor Networks for Short-Range Applications

Free space optical communication (FSOC) systems using direct detection and line of sight (LOS) laser links can provide spatially efficient and physically secure connectivity for wireless sensor networks. The FSOC system can be developed with low power microcontrollers so that the entire sensor system can be implemented on a single printed circuit board. Available data rates can range from kb/s to hundreds of Mb/s with the complete system consuming power only in the tens of mW. These features are advantageous for low-power communication networks over short distances in environments where LOS is available, and where radio frequency (RF) connectivity must be avoided because of interference or security issues. In particular, the faster data acquisition rates of FSOC systems are extremely attractive in applications where the sensor systems, or "motes", remain in sleep mode most of the time and need to transmit large amounts of data in extremely short bursts when they wake up. However, in order for directional FSO sensor networks to become viable short-range solutions, the networks must provide signal coverage over a wide field of view without strict optical alignment requirements, operate with efficient media access protocols that can handle network traffic in an efficient manner, and minimize random access times for the independent transmitting motes within the network. These challenges are the focus of this dissertation. In general, narrow optical beams used for FSOC require precise and complex pointing, acquisition, tracking and alignment methods. This dissertation addresses the challenge of alignment for FSO-based nodes by designing optical transceiver architectures with multiple narrow field of view (FOV) transmitters and a single, wide angle receiver. The architecture consists of rings of multiple transmitters surrounding a photodiode for light collection. Each ring is tilted at a different angle so that a wide transmission FOV can be obtained, thereby allowing point-multipoint communication. Depending on the number of transmitters and the transmitter's divergence angle, different FOVs can be tailored to fit the requirements of the target application. The developed transmitter design requires only a few milliwatts of transmission power from each transmitter to cover its respective FOV, which is sustainable with drive currents up to 10 milliamps using vertical cavity surface emitting lasers (VCSELs), making it a more practical strategy for a compact battery driven device. The other major challenge is designing the proper media access control (MAC) protocol, which provides nodes with addresses and channel access capability so that directional links between multiple nodes can be formed. The challenge lies in the fact that most nodes are blind to other nodes' transmissions because of their relatively narrow directional links. Because of this blindness, packet collisions are inevitable. Therefore, an efficient multiple access protocol needs to be designed for the FSOC system to ensure successful directional communication between the motes and cluster heads for data collection and relaying. While there are many protocols that allow multiple access and provide collision avoidance for traditional RF systems, these protocols are not optimized for FSOC systems consisting of multiple narrow FOV transmitters. Instead, a directional MAC (DMAC) protocol is developed from existing RF protocols, but modified for FSOC technology. It overcomes the limitations in FSOC communication resulting from directionality by setting up a master-slave network architecture where communication takes place between a sensing system, "mote", and a central control station, or "cluster head", which is designed with a multiple VCSEL transmitters. In this way, the physical transmitter sources of the cluster head become an integral part of the FSOC DMAC protocol. In this type of architecture, the master node, or cluster head, has the dual functionality of coordinating network traffic and aggregating data from all the slave nodes, or motes, that are within its field of view (FOV). Multiple cluster heads can form a directional network backbone, and can relay signals collected from a mote through other cluster heads, until the signal is delivered to its destination. In summary, this dissertation provides: 1) the design and implementation of small and inexpensive short-range FSOC systems that can be implemented using standard "off the shelf" components including a microcontroller and sensor device to form a complete standalone package; 2) development of a DMAC protocol that is optimized for the implemented FSOC system and target network applications; 3) network performance evaluation and optimization for the combined FSOC hardware, network architecture, and DMAC protocol. This is done through a series of hardware tests on an experimental prototype FSOC sensor network consisting of 10 motes and 1 cluster head and simulations of larger network sizes

Optical Wireless Data Center Networks

Bandwidth and computation-intensive Big Data applications in disciplines like social media, bio- and nano-informatics, Internet-of-Things (IoT), and real-time analytics, are pushing existing access and core (backbone) networks as well as Data Center Networks (DCNs) to their limits. Next generation DCNs must support continuously increasing network traffic while satisfying minimum performance requirements of latency, reliability, flexibility and scalability. Therefore, a larger number of cables (i.e., copper-cables and fiber optics) may be required in conventional wired DCNs. In addition to limiting the possible topologies, large number of cables may result into design and development problems related to wire ducting and maintenance, heat dissipation, and power consumption. To address the cabling complexity in wired DCNs, we propose OWCells, a class of optical wireless cellular data center network architectures in which fixed line of sight (LOS) optical wireless communication (OWC) links are used to connect the racks arranged in regular polygonal topologies. We present the OWCell DCN architecture, develop its theoretical underpinnings, and investigate routing protocols and OWC transceiver design. To realize a fully wireless DCN, servers in racks must also be connected using OWC links. There is, however, a difficulty of connecting multiple adjacent network components, such as servers in a rack, using point-to-point LOS links. To overcome this problem, we propose and validate the feasibility of an FSO-Bus to connect multiple adjacent network components using NLOS point-to-point OWC links. Finally, to complete the design of the OWC transceiver, we develop a new class of strictly and rearrangeably non-blocking multicast optical switches in which multicast is performed efficiently at the physical optical (lower) layer rather than upper layers (e.g., application layer). Advisors: Jitender S. Deogun and Dennis R. Alexande

Simulation and modeling of the behavior in the four-stroke spark ignition engine by using CFD simulation

Computational fluid dynamics (CFD) is a branch of fluid mechanics that use numerical analysis and data structures to analyze and solves problems that involve fluid flows. CFD have been applied to a wide range of research and engineering problems in many fields of study and industries, including engine and combustion analysis. The objective of this review paper is to analyze the behavior in the four-stroke Spark Ignition (SI) engine by using CFD simulation. To get the require result a few methods have been used to analyze the behavior in the engine such as using CAD geometric model where the solid works software have been prepared. Then, in the CAD geometric model also have ANSYS software to perform analysis in engine module. To predict the behavior of the engine during its working two type of analysis can be performed namely port flow simulation and combustion simulation. So, in first part of this report, the CFD analysis is carried out to analyze the performance parameter, including intake stroke, compression stroke, power stroke and exhaust stroke with hexane fuel combustion. For the results, some details of the engine model and some predicted results including temperature, flow time and pressure profiles. With the existence of CFD simulation it can help many fields of study and industries by predict and analyze the possibility that can be happened in the future. At the same time, serves as a quick and economical way of future engine designs and concepts

Underwater Optical Wireless Audio Transceiver

Scuba diving carries risks that can endanger lives. Many of these risks are preventable. However, an underwater communication system can increase a diver’s safety. Along with providing safety, an underwater communication device can enhance the scuba diver’s enjoyment. A low cost underwater optical wireless audio transceiver is designed. The project consists of the off-the-shelf parts that uses a microphone and speaker to transmit and receive sound. The project uses the concepts of visible light communications and pulse width modulation to transmit and receive sound. Although sound is commonly transmitted through ultrasound methods, visible light communications has several advantages. Visible light communications have higher bandwidth capability, suffer no electromagnetic interference, and travel at the speed of light. It also has its limitations including short ranges and line of sight. Fortunately, there is a small window in the blue-green region that is not heavily absorbed by water. The final prototype of the project is non-functional. However, there are possible fixes that could improve the project’s performance such as higher powered LEDs and collimating lens to focus the light to the receiver

Pointing-and-Acquisition for Optical Wireless in 6G: From Algorithms to Performance Evaluation

The increasing demand for wireless communication services has led to the development of non-terrestrial networks, which enables various air and space applications. Free-space optical (FSO) communication is considered one of the essential technologies capable of connecting terrestrial and non-terrestrial layers. In this article, we analyze considerations and challenges for FSO communications between gateways and aircraft from a pointing-and-acquisition perspective. Based on the analysis, we first develop a baseline method that utilizes conventional devices and mechanisms. Furthermore, we propose an algorithm that combines angle of arrival (AoA) estimation through supplementary radio frequency (RF) links and beam tracking using retroreflectors. Through extensive simulations, we demonstrate that the proposed method offers superior performance in terms of link acquisition and maintenance