Sensor Networks in Traffic Surveillance

Around the world we can found some WSN approaches to overcome this problem In presents a novel system based on wireless sensors network that has the potential to revolutionize traffic surveillance technology because of its low cost and potential for large scale deployment.

The system consists of two parts: a wireless sensor network and an access point. The wireless sensor network consists of a group of nodes, each comprising one or more sensors, a processor, a radio and a battery. They generate traffic information such as number of cars, speed and length of the vehicles, based on processing of the sensor data. The information is then sent to the access point over the radio. The traffic management center collects the information from each access point to analyze traffic conditions and take actions such as adjusting the traffic light durations. An example configuration for the system is given in Figure for an urban intersection and a freeway.

This effort is to develop a traffic monitoring system that aims to control the traffic congestions and improve the transport service. Since this system is based on wireless sensor network and it is more applicable to country like Sri Lanka because of low cost and large scale deployment. To be applicable for traffic monitoring this system must confirm the accuracy, lifetime of system. To fulfill these requirements sensor node, vehicle detection algorithm and the protocol used must be well designed.

Habitat and environment monitoring with wireless sensors

Habitat and environment monitoring is one of the area that get the benefit of wireless sensor networks. Because the nature of the Sensor is ideal for the habitat monitoring. Tiny sensor help to deploy the device in manageable space. It has the capability of long term data collection. Integration of local processing and data give the ideal situation for the habitat and environment monitoring. Each sensor provides the unique information about the environment

Infrared Temperature Sensors

Infrared (IR) radiation is part of the electromagnetic spectrum,which includes radio waves, microwaves, visible light, and ultraviolet light, as well as gamma rays and X-rays.

The IR range falls between the visible portion of the spectrum and radio waves. IR wavelengths are usually expressed in microns, with the lR spectrum extending from 0.7 to 1000 microns. Only the 0.7-14 micron band is used for IR temperature measurement.

Using advanced optic systems and detectors, noncontact IR thermometers can focus on nearly any portion or portions of the0.7-14 micron band. Because every object (with the exception of a blackbody) emits an optimum amount of IR energy at a specific point along the IR band, each process may require unique sensor models with specific optics and detector types.

For example, a sensor with a narrow spectral range centered at 3.43 microns is optimized for measuring the surface temperature of polyethylene and related materials. A sensor set up for 5 microns is used to measure glass surfaces. A 1 micron sensor is used for metals and foils. The broader spectral ranges are used to measure lower temperature surfaces, such as paper, board, poly, and foil composites.

source : http://www.sensorland.com/HowPage022.html

How Wireless Sensor Works...

A wireless sensor is much similar to the computer. A mote consisted with 3 main parts. 1- a mini computer, 2- a sensing device, 3- a radio transmitter.

The radio communication of crossbow motes are described as follows.
(visit http://www.xbow.com/Technology/RadioCommunication.aspx)

"The radio technology used in Crossbow’s wireless modules supports domestic and international frequency bands in the 433 MHz, 868-915 MHz, and 2.4 GHz bands. Multiple channels are available in each band under software control, resulting in a flexible solution for customer applications. Two modulation formats are available, two-tone Frequency-Shift-Keyed (FSK) at 433 and 868-915 MHz, and direct sequence spread spectrum (DSSS) at 2.4 GHz supporting the 802.15.4/ZigBee standard. All radios are bidirectional (half-duplex), and support a range of 30 to 1000 feet (10 to 100 meters) using XMesh with low-power protocol and battery-life time of 5 plus years in commercial applications. Transmit power levels are software controlled to enable end users to comply with local government regulations for frequency transmission.

The processor has full control of radio features, and can control parameters such as transmit/receive mode switching, channel selection, output power, and radio standby mode. Data packets routed through the radio are error correction encoded, with the ability to listen to the channel via RSSI measurement to determine if the channel is clear to send data. Depending on choice of radio and configuration, data rates of 19.2kbps to 240kbps are available. Both the radio and processor support deep sleep modes for maximum power savings. The motes are designed to support battery operation from 2.4V to 3.6V, with an integral battery voltage monitor."

sensing devises are the sensor boards which we can plug in to the mote. We can plug several sensor boards to single mote and it enables multiple sensing capability to the sensor. Sensor board is consisted with one or more sensors. Humidity, temperature, light, acoustic and many more sensors are available.

Sensor networks for all...

Wireless sensor is a kind of a transducer which senses the physical world facts like temperature, light, humidity, magnetic field and many more. It is capable of data gathering, processing, storing and communicating. Recent advances in wireless sensor networks has enabled the development of low cost, low-power, multifunctional sensor nodes that are small in size and communicate short distances. Therefore this technology is currently used in many areas and can be used in many areas. The major difficulty which is faced by the people in different domains is programming of the sensor nodes. The user has to program the sensor nodes using “nesC” programming language. To do that, users should have good nesC knowledge and programming practice. It is not practical we expect sound programming practice from a user not in computer science domain. It is very easy if those users have a higher level abstract configuration environment for configure sensors in their applications.

Sensor pics.....

Bunet

image courtesy: http://www.ucsc.cmb.ac.lk/wiki/index.php/BusNet

Busnet is a WASN application which is done by the University of Colombo School of Computing (UCSC). Its main goal is to gather environmental information over the large geographical area. In such application there is a major problem that the researchers have to face. To collect the information from wide area they have to maintain large number of sensors.

UCSC researchers came up with a smart solution for that. They build up their WSN over the public transport network in the country. It means they mounted the sensor on the buses and buses travel over the area and collect environmental data. The collected data are transfered to the base stations which is situated in the bus-stations when the busses reached to a particular bus-station.

The Busnet is enhanced its functionality by adding road surface monitoring application. It provides the road surface information about the route that the sensor traveled.

People who make effort on this project

• Dr. Kasun De Zoysa
• Dr. Chamath Keppitiyagama
• Mr. Gihan P. Seneviratne
• Mr. T.G.T.A.Bandara
• Mr. Kenneth Manjula Thilakarathna
• Mr. Lakshaman
• Mr. W. W. A. T. Shihan

For more details visit

• http://www.ucsc.cmb.ac.lk/wiki/index.php/BusNet
• http://www.dritte.org/nsdr07/files/papers/s5p1.pdf

SmartDust

What is smart dust? Some people may know about this. Smartdust is a network of very small sensors that can communicate with each other in wireless and ad-hoc maner. Smartdust sensors are more simillar to the normal sensor.

As other sensors smartdust consisted with 3 major components.

1. Mote (processor)
2. Sensor (device to use sense)
3. Radio Link (communicate with other nodes and base station)

Smartdus can detect temperature, humidity, magnetic field, vibration and other messurements. When we apply smartdust in real world thousands of nodes are scattered around the sensor field.

This is a very valuble in military applications. battlefield surveillance, treaty monitoring, transportation monitoring, enemy troops tracking.

image courtesy www-bsac.eecs.berkeley.edu/

Literature

According to the literature found related to the road trac surveillance using wireless sensors there are several prime strategies to recognize identify or detect traffic conditions. Detection with Magnetic Sensors, Video Sensors, Seismic Sensors, Acoustic (audio) Sensors are the main sensors used for those studies. Using the data collected from the sensors researches were analyzed the data using various ways. Then they came up with a mechanism for detect the vehicles/congestions. Most of the time they had used a threshold value for detection.

In the system which was designed in [1] comprised with two main components. Set of sensor nodes an the access point. Sensors are sensing the magnetic fields variation in the earth due to the vehicles and according to those measurements the system identifies the vehicle. For that the correlation between magnetic field and the vehicle level in the road was identified. Further more using a state machine and a threshold value system categorizes the identified vehicles. It is an enhancement for the system.

The solution suggested in the research [2] is to identify the trac status of the road using the GPS sensors. The GPS receiver records timestamp, altitude, speed, distance, heading, and coordinates once every 4 to 10 seconds. To find the correlation of traffic status and the sensing measurements this process was done for several days continuously and extracted some features of trac patterns on road segment. There are three parameters concern with the preliminary data. Those are speed, temporal data and spatial data. To obtain a trac pattern or feature each analysis should be concerned with those three. Without any of these will cause ambiguity in analysis. Finally using the analysis they found an association of trac pattern and the GPS data.

Refferences
[1] Sinem Coleri, Sing Yiu Cheung and Pravin Varaiya, “Sensor Networks for Monitoring Trac”, University of California, Berkeley, August 5, 2004.

[2] Jungkeun Yoon, Brian Noble, Mingyan Liu, “Surface Street Trac Estimation”, Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109-2122.

Sensor Networks in real world

The sensor networks can be used for various application areas. For those application areas, there are different technical issues that researchers are currently resolving. In the deployment time sensors are used wireless ad-hoc networking features. Since sensor networking used in various areas it should have domain specific networking features such as protocols and algorithms. The sensors are scattered over the area that we want to extract data we called sensor field. Each scattered sensor can gather data from sensor field and process that if it is necessary. Then the information gathered by that node is routed to a gathering point that called sink. From the sink we can use that gathered information.

There are some design issues to be considered in sensor networking. First one is fault tolerance. Some nodes may not work as expected. In that case failure nodes should not affect to the entire network functionality. Power consumption is very important in the sensor networking. Sensor is a battery powered device and in some occasions we can’t change those batteries frequently (Military applications). Therefore we should have power saving methods to long last these nodes. Bandwidth in sensor nodes is not much higher. Therefore we should manage that with our resources. The sensor networking is currently used in many areas. Such as monitoring habitat, Military applications, Vehicle Monitoring, Disaster management systems, Chemical and Biological sensors etc...

Sensor

Sensor is a device. Sensors are used in everyday life. Applications include automobiles, machines, aerospace, medicine, industry and robotics. A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. The development of wireless sensor networks was originally motivated by military applications such as battlefield surveillance. However, wireless sensor networks are now used in many civilian application areas, including environment and habitat monitoring, healthcare applications, home automation, and traffic control.

content courtesy www.wikipedia.com