Wireless Sensor Networks and Their Usage
Ali Raza,Shahid Rasheed & Shazib Javeed
University Of Central Punjab

Abstract
Innovations in industrial, home and automation in transportation represent smart environments. Wireless Sensor Networks (WSNs) provide a new paradigm for sensing and disseminating information from various environments, with the potential to serve many and diverse applications Networks (WSN), where thousands of sensors are deployed at different locations operating in different modes .WSN consists of a number of sensors spread across a geographical area; each sensor has wireless communication capability and sufficient intelligence for signal processing and networking of the data.
Wireless Sensor Networks (WSN) are used in variety of fields which includes military, healthcare, environmental, biological, home and other commercial applications. With the huge advancement in the field of embedded computer and sensor technology, Wireless Sensor Networks (WSN), which is composed of several thousands of sensor nodes which are capable of sensing, actuating, and relaying the collected information, have made remarkable impact everywhere?
Key Words
Wireless Sensor Network (WSNs)
Structural Health Monitoring (SHM)
Micro Electro-Mechanical Systems (MEMS)
Introduction
Sensor network is capable of sensing, processing and communicating which helps the base station or command node to observe and react according to the condition in a particular environment (physical, battle field, biological) . Sensor network protocols have a unique self-organizing capability. Another interesting feature of WSNs is that the sensor nodes cooperate with each other. Sensor nodes have an in-built processor, using which raw data are processed before transmission. These features facilitate wide range of applications of WSNs ranging from biomedical, environmental, military, event detection and vehicular telematics.
The sensors that, when distributed in the environment, comprise WSNs include cameras as vision sensors, microphones as audio sensors, and those capable of sensing ultrasound, infra-red, temperature, humidity, noise, pressure and vibration. Although the individual sensor’s sensing range is limited, WSNs can cover a large space by integrating data from many sensors. Diverse and precise information on the environment may thus be obtained. Sensor networks are an emerging computing platform consisting of large numbers of small, low-powered, wireless motes each with limited computation, sensing, and communication abilities. WSNs could potentially become a disruptive technology, for example because of social issues such as security and privacy, but the technological vision is for new and diverse types of applications for the social good. The environment can be monitored for fire-fighting, to detect marine ground floor erosion, and to study the effect of earthquake vibration patterns on bridges and buildings. Surveillance of many kinds can be supported, such as for intruder detection in premises. Wireless sensors can be embedded deeply within machinery, where wired sensors would not be feasible because: wiring would be too costly; could not reach the deeply embedded parts; would limit flexibility; would represent a maintenance problem; or would prevent mobility. Mobile items such as containers can be tagged, as can goods in a factory floor automation system. Smart price tags for foods could communicate with a refrigerator.

Working

Block diagram

Wireless Sensor Networks are collections of motes. Motes are the individual computers that work together to form networks. The requirements for motes are extensive. They must be small, energy efficient, multifunctional, and wireless. Collections of motes communicate with each other to reach a common goal. For example, if the goal is to collect information about the microclimates around all sections of redwoods in a forest, the motes are placed in the trees to form a network. Once placed, they collect and transmit data to each other, and eventually to a main computer.
How do motes communicate with each other?
Motes communicate with each other using radio transmitters and receivers. They form networks with other motes that change with the positions of the motes. They create links with each other in different configurations to maximize the performance for each mote. These links all lead to the “parent” mote, which transmits the information from each of the “child” motes to computer.

What safety mechanisms are in place?
In addition to communicating, motes also adapt to their situation. In the case of a malfunction the remaining motes will reform the network. For example, there are 500 motes in place around a system. If 20% or 100 motes die, the rest of the motes will reconfigure the network to continue working with the remaining 400. Furthermore, 400 motes will collect as much data as 400 scientists working non-stop for that period of time. The bigger problems that face these networks are people with destructive intentions, and the potential for motes to keep “working” while spitting out bad information. Corrupt data can sometimes be caught when the information is used and reread by humans, but the times that it goes unnoticed can slightly or significantly alter conclusions drawn from the data.
The threat of hackers is a serious problem because the operating system for the motes is an “open-source” system, which allows relatively easy access to codes. All security procedures will develop with the growth of the technology in response to a larger number of hackers. The harder people try to break the system, the more the system will be protected.
How do WSNs communicate with the user?
Wireless sensor networks communicate within themselves as well as with a user not necessarily near the network’s location. Wireless sensor networks collect data about what is happening, and perform some action according to that data, be it moving, setting off alarms, or simply recording the data. All of these actions change the world that the mote is in, causing other changes, and so on. Because of the connection between the motes, all of these changes affect each mote, and all of the data collected by the mote is routed to the parent mote. This parent mote is connected to a computer of higher power that performs a function for which the motes are not designed. One such function is to access the internet and transfer the motes’ data to the user’s computer. The user may also communicate with the motes. If the user gives some directives, the directives will be sent over the internet to the computer/station. The computer will communicate the same directives to the parent mote, which then disperses the message.
Construction of motes
Sensors:
When motes are under construction, their intended purpose often dictates the sensors that are added to the mote e.g temperature, moisture, and vibration sensors. These are fairly typical mote, but some motes have many more functions. There are motes that take photographs of the surroundings, sense motion, measure light intensity, and much more.
Power Source: The power source for the mote also depends the mote’s intended use. If the mote is designed to last a very long time, say one year, it will have a larger power source than a mote that is only meant to run for a month.
Radio:
The radio consists of a radio transmitter and a radio receiver. Both of these parts must exist for any mote to fully communicate with the other motes. The radio, when transmitting, receives information from the electronic brain and broadcasts the data to other motes according to the network connections. In the other direction, when receiving, the radio receives information from another mote’s radio and transmits it to the electronic brain.
The Electronic Brain:
It consists of a microprocessor and some flash memory. Many of them have connectors to add other processes and sensors with ease.
Challenges In WSNs.
Life Time
One of the main issues in sensor networks is network lifetime.With the available technology, the sensors are battery powered. Due to size and cost constraints, the energy available at each sensor for sensing and communications is limited and globally affects the application lifetime. A solution for mitigating the energy problem is to implement mechanisms for efficient energy management. One method is based on scheduling sensor activity so that for each sensor the active state, in which it actually performs its monitoring task alternates with a low-energy idle (sleep) state.
Flexibility
Sensor networks should be scalable, and they should be able to dynamically adapt to changes in node density and topology, like in the case of the self-healing minefields. In surveillance applications, most nodes may remain quiescent as long as nothing interesting happens. However, they must be able to respond to special events that the network intends to study with some degree of granularity.
In a self-healing minefield, a number of sensing mines may sleep as long as none of their peers explodes, but need to quickly become operational in the case of an enemy attack. Response time is also very critical in control applications (sensor/actuator networks) in which the network is to provide a delay-guaranteed service.
Maintenance
The only desired form of maintenance in a sensor network is the complete or partial update of the program code in the sensor nodes over the wireless channel. All sensor nodes should be updated, and the restrictions on the size of the new code should be the same as in the case of wired programming.
Data Collection
Data collection is related to network connectivity and coverage.
Communication
Most sensor networks use radio communication, even if alternative solutions are offered by laser and infrared.
Sensing
The high sampling rates of modern digital sensors are usually not needed in sensor networks. The power efficiency of sensors and their turn-on and turn-off time are much more important. Additional issues are the physical size of the sensing hardware, fabrication, and assembly compatibility with other components of the system.
Applications
HEALTHCARE APPLICATIONS
WSNs are very efficient in supporting various day-to-day applications. WSN based technologies have revolutionized home and elderly healthcare applications. Physiological parameters of patients can be monitored remotely by physicians and caretakers without affecting the patients’ activities. This has resulted in reduction of costs, improvement of equipment’s and better management of patients reaping huge commercial benefits. These technologies have significantly minimized human errors, allowed better understanding into origin of diseases and has helped in devising methods for rehabilitation, recovery and the impacts of drug therapy. Biological Task Mapping
WSNs find widespread applications in the area of biological sensing. Specifically, there is recent research going on in the concept of “labs on a chip”, supported by latest technologies like nano-techniques. The use of WSNs for biological applications have been accelerated due to the advancements in Micro Electro-Mechanical Systems (MEMS), embedded systems, microcontrollers and various wireless communication technologies.
Biomedical Signal Monitoring
WSNs have revolutionized the field of medicine in many ways. Telemedicine is the field which involves the treatment and care of patients from a distance and also aids in biomedical diagnosis. The application of WSNs has significantly improved this field. In this technique a mote is placed inside or around the desired body part and kept it under observation
COMMERCIAL APPLICATIONS
Some of the commercial applications of WSNs include vehicular monitoring, cultural property protection, event detection and structural health monitoring. These applications have a profound impact on ordinary day-to-day affairs.
Smart Parking
WSNs are widely used in the applications like intelligent parking for the purposes such as effective usage of existing parking lots instead of making expensive investments in new installations and to make provisions for coupling with cheap sensor nodes which can track the vehicles effectively. Existing solution for parking application uses magnetometers and video cameras. The detections of magnetometers are not very accurate as they are influenced by environmental factors. Video camera which is the alternate is expensive and it is not feasible to transmit large amount of data in a wireless environment through multiple hops. Another factor which affects the application of magnetometers and video cameras is that in a parking lot, apart from entry and exit of vehicles there may be other moving objects, which is a great challenge.
Monitoring of remote parking, mechanism for parking reservation and automated
Guidance is some of the latest features provided by the system. Modern vehicles.
Fuel efficiency and reduction in the weight of automotive can be achieved by replacing wired sensors and their cables with wireless sensors.
Event Detection
Tracking is a typical characteristic of wireless sensor networks, especially for instant tracking of events. Much work has been done in WSN, with sensor nodes having identical sensing units.
Structural Health Monitoring
The process of detection of damage for civil, aerospace and other engineering systems is referred to as Structural Health Monitoring (SHM). Any change in the material or geometric properties of these systems due to internal factors (aging) or external factors (natural calamities, pollution) is termed as damage. The normal operation of an SHM system includes low power, long-term monitoring of a structure to provide periodic updating of its health condition. However, during critical events such as earthquakes and other natural
Disasters, real-time rapid structural conditional screening can be done using SHM system.
ENVIRONMENTAL APPLICATIONS
Environmental applications include the monitoring of farms, green house, forest ,snow ,erosion phenomenon and flood warnings.
SEISMIC MONITORING: A promising application for underwater sensor networks is seismic monitoring for oil extraction from underwater fields. Frequent seismic monitoring is of importance in oil extraction .Terrestrial oil fields can be frequently monitored, with fields typically being surveyed annually, or quarterly in some fields, and even daily or continuously in some gas storage facilities and permanently instrumented fields. However, monitoring of underwater oil fields is much more challenging, partly because seismic sensors are not currently permanently deployed in underwater fields.
Greenhouse Monitoring
To ensure that the automation system in a greenhouse works properly, it is necessary to measure the local climate parameters at various points of observation in different parts of the big greenhouse. This work if done using a wired network will make the entire system clumsy and costly. However, a WSN based application for the same purpose using several small size sensor nodes equipped with radio would be a cost effective solution. Habitat Surveillance
WSNs find widespread application in habitat surveillance compared to other monitoring methods due to high deployment density and self-organization of the sensor nodes. The advantage with WSN is that the invisible placement of sensor nodes in the habitat does not leave any noticeable mark which might affect the behavior pattern of the inhabitants.
Tsunami Surveillance
WSNs system can be used to predict the tsuami.The buoyant sensor can be placed in remote locations,which will analyze the ocean waves. INDUSTRIAL APPLICATIONS
Nowadays, industrial applications are built on distributed architectures and they are required to be inexpensive, flexible and dependable. The system’s performance can be improved by interfacing sensors and actuators directly to the industrial communication network, as data and diagnostics can be made accessible to many systems and also shared on the web.
MILITARY APPLICATIONS
WSNs play a vital role in military Command, Control, Communications, Computing, Intelligence, Surveillance, Reconnaissance and Targeting (C4ISRT) systems. In the battlefield, the WSNs are prone to the attacks, where either the data or corrupting control devices are attacked, leading to large amount of energy consumption and finally to the exit of nodes from work. The energy efficiency of sensor nodes and the correct modeling of energy consumption are the research issues yet to be explored.
Conclusion
Advancement in the field of wireless communication has drastically changed our lives. Today we can’t even imagine to live without this technology. And the time is not far when this technology will replace the human services.
Acknowledgement
A highly gratitude to Dr.ir Nasir for their motivation and rendering their precious services to pen this paper . He kept an eagle eye and vigilantly usher’s us to make this paper unabridged.
References
[1] http://faculty.kfupm.edu.sa/COE/mayez/ps-coe499/project/Sensor-network/XSCALE-STARGATE/1-1-challenges-sensor-networks.pdf
[2] http://www.eecs.berkeley.edu/~binetude/work/reliable.pdf
[3] http://www.eecs.harvard.edu/~dbrooks/hempstead_JOLPE08.pdf
[4] http://www.eecis.udel.edu/~fei/reading/070426.wsn.security.survey.pdf