WIRELESS SENSOR NETWORK

CHAPTER ONE
INTRODUCTION
1.1       Preamble
The emerging fields of wireless sensor networks combines sensing, computation, and communication into a single tiny device. While the capabilities of any single device are minimal, the composition of hundreds of devices offers radical new technological possibilities. The power of wireless sensor networks lies in the ability to deploy large numbers of tiny nodes that assemble and configure themselves. Usage scenarios for these devices range from real-time tracking, to monitoring of environmental conditions, to ubiquitous computing environments, to in-situ monitoring of the health of structures or equipment. While often referred to as wireless sensor networks, they can also control actuators that extend control from cyberspace into the physical world. The most straightforward application of wireless sensor network technology is to monitor remote environments for low frequency data trends. For example, a chemical plant could be easily monitored for leaks by hundreds of sensors that automatically form a wireless interconnection network and immediately report the detection of any chemical leaks. Unlike traditional wired systems, deployment costs would be minimal. Instead of having to deploy thousands of feet of wire routed through protective conduit, installers simply have to place quarter-sized device at each sensing point (Jason, 2003).
The network could be incrementally extended by simply adding more devices or complex configuration. In addition to drastically reducing the installation costs, wireless sensor networks have the ability to dynamically adapt to changing environments. Adaptation mechanisms can respond to changes in network topologies or can cause the network to shift between drastically different modes of operation. For example, the same embedded network performing leak monitoring in a chemical factory might be reconfigured into a network designed to localize the source of a leak and track the diffusion of poisonous gases. The network could then direct workers to the safest path for emergency evacuation. Current wireless systems only scratch the surface of possibilities emerging from the integration of low-power communication, sensing, energy storage, and computation.
Recent developments and market trends towards portable computing and communication devices imply an increasingly important role for wireless access in the next generation internet. The research of wireless sensor networks has become prosperous in recent years because of their potential applications in many areas, such as environmental monitoring, surveillance, disaster search and rescue. The short range wireless sensor networks are of prime importance to drive the deployment of large-scale embedded computing devices. Wireless, mobile and sensor network scenarios are expected to grow rapidly at the edge of internet. These devices will be used increasingly in “pervasive computing” applications in which the internet enables monitoring and interaction with every aspect of the physical world. Over past few years, the internet has evolved into a global network supporting a variety of computing and telecommunication applications. In future, the internet must respond to many emerging requirements like increased scale, improved security, and support for mobile, wireless devices and embedded applications (Divya, 2008).
In order to help building the next generation internet which will include wireless and sensor network devices, researchers need a vehicle to drive their next ideas. Researchers are investigating next generation network architecture and protocols but they need a facility to evaluate them. The evaluation can be done using Analytical modelling, simulation or High-fidelity environments (measurements).
Analytical modelling provides best insight into the effects of various parameters and their interactions. In spite of being flexible to use at any stage, analytical modelling is less used compared to simulation or measurements because of its complexity. Another disadvantage of analytical modelling is its simplified mathematical modelling tools which do not capture the irregularity of sensor networks.
1.2       Background of the Study
1.2.1    Wireless Technology
There are situations when it is desirable to make measurements in locations where the use of cabled sensors is challenging. Protecting cable, is by running them through conduit or burying them in channels is time consuming, labour intensive and sometimes not even possible. In some applications, measurements need to be made at distances where long cable decreases the quality of the measurement or are too costly. At times, when there is increase in the measurement being made but the datalogger does not have enough available channels left for attaching additional sensor cables. Each of these instances can be resolved with a wireless sensor network. WSN provides a reliable, low maintenance, low power method for making measurements in applications where cabled sensors are impractical or otherwise undesirable.
1.2.2    Wireless Sensor Network
This is a network that uses wireless connected sensor devices to monitor and communicate specific conditions. It gathers concerned information such as voltage, pressure, motion, sound etc. in different locations, especially some place that people cannot be competent e.g. in nuclear power plants.
A WSN can be formed by multi sensor nodes with different topologies such as star, tree, ring and mesh structures. Different multi-hop routing protocols are applied in these WSN to broaden the communication range. The ideal wireless sensor is networked and scalable, consumes very little power, is smart and software programmable, capable of fast data acquisition, reliable and accurate over the long term, cheap, easy to install, and requires virtually no real maintenance.
1.3       Statement of the Problem
With the effect of environmental quantities on nature and human being, it is our goal is to build an environmental physical quantity monitoring system for intelligent planning, and maintenance of the environment. This system should work under varied physical conditions. It should be cost effective, easy to deploy (no need to dig or build overhead structures) and it should require minimal maintenance. We want to build a physical quantity monitoring system that is able to remove or reduce the error in human readings. Thus, our efforts are based on reporting temperature, light intensity, humidity and gases (i.e. smoke). The testbed will be controlled by PC-end with different commands which can collect data from all sensor nodes easily and report failure or abnormity to users in time.
1.4       Justification of the Study
Wireless sensor networks are mainly designed for habitat and environmental monitoring where many sensor nodes gather data that is sent towards one or more sink nodes. Since all this nodes are scattered over a wide area in most cases, they cannot communicate with the sink directly. Due to this fact, we plan on designing two prototypes that will communicate through a receiver means that has to be designed for effective environmental monitoring and analysis.
1.5       Aim and Objectives
1.5.1  Aim
This project work is aimed at developing a wireless sensor network (WSN) testbed for realization of an environmental condition monitoring system.
1.5.2  Objectives
i.  To review the existing WSN testbeds with their respective goals.
ii.  To identify the components to be used for the design of the sensory nodes.
iii.  To design a WSN based environmental monitoring system.
iv.  To implement the designed sensory node that measures different environmental quantities selected.
1.6  Scope of the Study
The proposed solution of this project is limited to two nodes and a server. The two nodes can communicate with the server by sending signal to the server as well as receiving processed signal from the server. The transmitter can only transmit through a distance ranging from 90m to 110m. The two nodes are arranged using star topology network in which the signal sent from each node is being transmitted straight to the server and reply from the server can be received from the node from which the signal is received. The design is to be modelled and simulated for measuring physical environmental quantities using WSN.
1.7       Methods of the Study
The methods employed in the study are:
i.  Library: - This entails the use of several textbooks, journals, past projects that have discussed previously the subject matters and have shed light to the subject.
ii.  Internet browsing: - This requires surfing through various websites to get latest information and insight into the project work.
iii.  Field survey: - This includes preliminary and reconnaissance survey of the research area to get basic information about the area for data collection.
iv.  Laboratory works: - This has to do with circuitry design, storage, querying and system analysis.
v.  Test: This involves the implementation of the design and testing it for data collection.