Toword Advanced Wireless Sensors Networks Architecture

Published Date: 02 Nov 2017

Led by the scientific revolution of micro-electro-mechanical system (MEMS) technology, WSNs have become forefront of the scientific community. Due to a powerful combination of functions : sensing, processing and communication in a wireless fashion ,WSNs have found countless applications in different domains ranging from medical to military, and from home to industry. Because you cannot control what you cannot measure, the world becomes field with sensors in every corner. The following sections are not intended to make a comprehensive review of all WSN applications; instead it's a collection of state-of-the-art research papers discussing current applications and deployment experiences.

Military :

Military requirements :

Being the main driver for investigation, military applications are being served by many researches for all military requirements including [2] :

Physical attributes of sensors: Sensors nodes could be hand deployed in advance and transported by vehicle to the deployment area, and thus the physical size and weight of the sensor is not a constraint although a small size and light weight is desirable.

Self-configuration after deployment: Each sensor node must be able to rapidly identify its neighbours to configure themselves into an ah-hoc network. Moreover, the network should maintain itself where and when needed [3] in order to cope with a failing node and reconfigure the network without any intervention from the outside.

Network size: A network with less than 100 nodes, mostly it covers 5 to 20 km2 where a communication range is between 250-500m.

Information flows: The need of a bidirectional communication, first from sensors network to the WSN gateway and beyond, and the second way is used to send monitoring information, e.g. changing cameras orientation. Exchanged data in both sides must be considered in the network security as a priority to avoid leakage or false transmitted information.

Duration of usage: Military sensor networks operate for about two months, while some other networks are required for days. An exchange of batteries is helpful for a longer lifetime.

Physically and electronically discrete operation: Nodes might be covered in appearance with a small electromagnetic emission pattern to remain hidden from potential adversaries.

Data type: Data transmission rates do not require to be high, It can be limited to less than 30 bytes, even if military commanders ask for imagery or video

Data reliability: To ensure the secure reception of data, some delivery techniques should be included.

Denial of service: Resistant to jamming is one of the means to report attacks of this type.

Tamper-proof: The sensor nodes must include an anti-tamper mechanisms in -builtre so that a captured node cannot be revealed to any malicious third party.

Costs: The price for a single node is generally not as critical as in the "civil Bluetooth-focussed market".

Other requirement such as tailored routing and transport protocols, short distances between nodes and special-purpose operating systems are more likely challenges of a typically assumption in the near-term of military applications.

Military applications:

DARPA’s self-healing minefield [4]: A self-organizing sensor network used to complicate the progress of enemy troops and redistribute mines by peer-to-peer communication between anti-tank mines.

Urban warfare [4]: An application that consists of a set of nodes deployed in an urban landscape as so to detect chemical attacks and to track enemy movements.

PinPtr [4]: An ad hoc acoustic sensor network developed at Vanderbilt University in order to localize snipers, by detecting muzzles blast and the acoustic shock wave caused by gunfire. The main goal is to determine sniper's position.

Mainly the same goal as PinPtr, the application described in [5] brings in play tracking multi-vehicle in a pursuit-evasion game similar to a battlefield. Along with a sensor network, the pursuers teams seek to locate their adversary.

"A line in the Sand" [1]: Same kind of application as described in [5], developed by Ohio State University consists of ninety nodes able to detect metallic objects and track and classify the moving ones. The system could make the difference between vehicles and soldiers and other beings e.g. civilians that must be ignored.

Healthcare:

Background:

Large-scale field studies of human behavior and chronic diseases providers patient's healthcare insight into physiological and physical health states that are critical to the detection, diagnosis and treatment.

Advances in medical sensing technologies are based on 3 different dimensions [7]:

Sensing Modality:

These sensing technologies carry the promise to resolve public health crisis caused by infectious diseases [6] and also enabling early detection and personalized treatments.

Size and Cost:

The latest advances in microelectronics and computing have made the complex and cost traditional medical sensors accessible to patient at their homes, work places, and every living spaces. The first to appear were portable medical sensors for home use. Then ambulatory medical sensors, emerged. Their small size allowed them to be worn or carried by a person. Finally the latest Implantable medical sensors for continuous measuring internal health status and physiological signals.

Connectivity:

Medical sensors have incorporated wireless connections such as Bluetooth, Zigbee to communicate wirelessly to nearby computers or smartphones with cloud computing services. Sensors lock the history of measurements in nonvolatile memory while patients go through their daily work life away from home so that it can be used later and shared with healthcare personnel.

Healthcare applications:

A long list of healthcare applications we introduce some of them in what follows [7]:

Monitoring in Mass-Casualty Disasters:

In case of disaster the rapidly deployable nature of wireless sensing systems and their portability helps to automatically report the triage levels of numerous victims and track their health status.

Vital Sign Monitoring in Hospital:

Less noticeable Wireless sensing hardware, helps to settle enduring numerous wired sensors used in hospital to monitor patients.

At-home and Mobile Aging: Wirelessly networked sensors embedded in people’s living spaces or carried on the person are able to monitor and treat physical, physiological and behavioral states particularly for elderly in real-time and everywhere.

Assistance with Motor and Sensory Decline: So many types of intelligent assistive devices embedded in the surroundings, worn or even implanted on the user’s person provide the assistance and guidance to patients with declining sensory and motor capabilities

Large-scale In-field Medical and Behavioral Studies:

Body-worn sensors and sensor-equipped Internet-connected smartphones enable behavioral and physiological data to be collected from a large number of users while they're leading their daily lives.

Technical challenges:

Unlike applications in other fields, healthcare applications, impose stringent requirements

on system reliability, quality of service and privacy [7]. Some of the core challenges among along list can be: trustworthiness, privacy and security, resource scarcity.

Environmental Monitoring:

It was obvious that civil security and public safety is the main concern of the society. According to a survey based on more than 300 cities, the spending on public safety already makes up 18% of a usual city budget and 62% of surveyed cities indicated that public safety is the capital driver for adopting new technologies such as Wireless Sensor Networks (WSN) [8].

Indeed, WSN are deployed in many hazardous workspaces entailing a high risk like underground mining, steelworks, and refineries, by monitoring deteriorating grounds, toxic gases, unstable grounds or tracking workers in hazard zone in order to guide

Firefighters [9]. Moreover, WSN are used in emergency cases to prevent consequences of natural disasters such as flood, tsunami, earthquake, terrorist attack. For example the deployment of Wireless nodes in rivers is able to monitor real time water levels.

Environmental Observation and Forecasting:

Environmental Observation and Forecasting Systems (EOFS) is a new class of large-scale distributed system designed to alert, monitor, model, and forecast wide-area physical processes. One of the first WSNs application areas that are affecting people's living conditions. Especially when it's about natural disasters such as Flood, Volcanic Eruption, earthquake, ect. [9]

Disaster Prevention:

Fire detection:

Fire rescue is one of the most important public safety activities:

In the summer of 2007, more than 80 fatalities in Greece and 670,000 acres(2,711 km2) by fires. The same year in California, 500,000 acres (2,027 km2) were devastated by the flames, causing at least 14 decease [10].

Sensors are affective by certain basic variables including:

relative humidity, atmospheric pressure, temperature, Carbon monoxide (CO),Carbon Dioxide (CO2) as well as dynamic and static variables such as the type of fuel, slope of the land, the direction and the speed of the wind, and so on .

A sensor is able to transform physical or chemical readings gathered from the environment into signals that can be measured by a system. If some of these measured goes above the preconfigured threshold, due to system rapidity and real-time information, an alarm will be sent to the firefighters. They will know immediately and exactly the location of fire as well as the direction and possible evolution of the flames.

Fire rescue is different from any other WSN application like object tracking and monitoring. It involves several specific requirements including: accountability of firefighters, real-time monitoring, intelligent scheduling and resource allocation, web-enable service and integration.ect [11].

Volcanic Eruption:

Studying active volcanoes requires high data rates, high data fidelity, and high spatial separation between nodes.

In[12] the authors describe a WSN deployed, In August 2005, on Volcán Reventador in northern Ecuador composed of 16 nodes over 3 km. The sensors were equipped with microphones and collected continuous data from the erupting volcano. Over three weeks, the network captured 230 volcanic events; therefore useful collected volcanic data allows evaluating the sensor networks: smaller and lighter nodes, less power consumption.

Agriculture:

WSN for Food Security and Agriculture:

The main goal of food security is to ensure that everyone has enough food to lead a healthy life. For this wireless sensor networks deployed or implemented locally or globally provide a reliable and secure food systems at each stage of the food cycle, from food production, harvesting, transport to the shops a consumer buy at and resulting bio-waste outputs. Such monitoring and management is able to solve out food problems by the following techniques:

Monitoring and Early Warning:

First step of food security is the systematic monitoring of food supplies by mapping agricultural production, food shortages and establishing comprehensive data bases. Food monitoring becomes greatly easily due to the use of WSNs, including: remote sensing infrastructure, communication infrastructure and other equipments such as geographic information systems and mainframes. In the case of natural disasters sensors can make it possible for governments to take preventive actions.

Locally and Globally: Emergency Communications

Example the UN World Food Program (WFP) using emergency telecommunications services includes networks and satellite phone services.

Locally: Monitoring Agricultural Conditions :

In order to enhance the farming system and the production, a set of tools is used in agriculture soil monitoring, including:

Autonomous Sensors: These sensors measure air temperature, atmospheric pressure and humidity.

Ubiquitous Sensor Networks (USN): Deployed on the field and transmitting data to a base station that can be uploaded to global systems or tested for different purpose for better farming conditions.

Telemetry Units: These units measure and transmit air temperature, humidity, leaf wetness data, solar radiation, wind speed, and soil moisture, using cellular networks.

Wireless sensor networks can be used to improve food yields and enable farmers to better forecast crop yields and production, they can also monitor isolated areas of difficult access the risk of coolness can also be detected by combining sensors such as humidity, temperature, and light.

The best example to mention is the COMMON Sense Net project (Community-Oriented Management and Monitoring of Natural Resources through sensor network) [13] that consists of a wireless network of ground-sensors that periodically record the state of the soil (measuring salinity and humidity), the air temperature, the volume of precipitation and other parameters in the rural semi-arid areas in Karnataka, Southern India. A second network of subterranean sensors is used to monitor the level and quality of ground-water.

Locally: WSN to Enhance Sustainable Agricultural Development: This is also referred to as e-agriculture and the following are some practical examples of this use of WSN:

Rural Radio: Is an inexpensive communication, provides a fairly wide coverage of information about farming conditions.

SMS: This service reaches millions of farmers every week due to continuous text messages reception of market information on commodities.

Telecenters: Telecenters in rural areas help farmers to communication with buyers and access information on improved farming techniques.

E-learning/Training: Several partnership initiatives give the opportunity to train individuals and support institutions and networks all over the world so as to fight against poverty and hunger in rural areas and also to manage agriculture information.

A study in Kerala, India, showed that fishing profits grew by 8 per cent while fish prices decreased by 4 per cent, after mobile phone services were introduced in the market. This improvement was equivalent to an increase of 2 per cent in per-capita GDP. [14]

Glossary of acronyms

SMS Short Message Service

Conclusion:

Military application was the original motivation for wireless sensor network researches, as they provide endless opportunities as well as reduced costs and communication networks, many other potential applications have emerged in what follows our target interest will be in the environmental monitoring. However various challenges involved such as energy problem, infrastructure-less sensor network so that routing and maintenance algorithms should be distributed, randomly deployed sensor nodes hence, the setup and maintenance of the network should be entirely autonomous, secure communication and mechanisms, and so on.