Overview of Wireless Sensor Networks-1

Wireless Sensor Networks represent a new generation of real-time embedded systems with significantly different communication constraints from the traditional networked systems.
Wireless sensor nodes have emerged as a result of recent advances in low-power digital and analog circuitry, low-power RF design and sensor technology. sensor networks are distinct from traditional computing domains. Their design assumes being embedded in common environments, instead of dedicated ones.
As these devices are deployed in large numbers, they will need the ability to assist each other to communicate data back to a centralized collection point.

Sensor networks are composed of large numbers of tiny sensing and computing devices. Each of these devices called motes, have very limited communication, computational and energy resources. Often embedded in uncontrolled physical environments, such as nature reserved, seismically threatened structures. These networks require distributed algorithms for efficient processing.

The character of the TinyOS should be small physical size, modest active power load and tiny inactive load. TinyOS is an event based power use with embedded networked sensors. It is designed to support the concurrency intensive operations required by networked sensors with minimal hardware requirements.

HARDWARE : MOTES
WSNs composed of tens of thousand of tiny device with very limited resource (motes). Two mote hardware platforms, RENE2 and MICA, currently used by several institutions.
RENE2 is limited to 10kbit, mica supports 40kbit communication in its radio.

MICA motes by their design are fairly robust mechanically with the battery case firmly integrated with main processing and sendor boards, and mounting holes for securing the sensor boards.
THe motes are generally programmed using MIB(Mote Interface Board). The interface board connects to the parallel ports of the PC or laptop. Once the TinyOS environment is installed, a command line interface is used to install the TinyOS code and assign the MoteID number.

MICA can detect ultra small vibrations, acoustic noise, magnetic disturbances, conventional light, temperature and proximity.
MICA architecture consists of MTS sensor modules that plug into MPR processor modules. an MTS and MPR pair lalong with 2 AA batteries. MPR modules run a very small operating system, called TinyOS and communicate bi-directionally with other MICA sensor nodes or a radio base station.
– MTR Sensor Modules are compact, low power and small units.
– MPR process and radio modules are small low-power, combination radio and processor modules that can communicate in a peer-to-peer or master-slave fashion.
mica1.jpg
SOFTWARE : TINYOS
TinyOS with small size, modest active power load and design to support concurrency-intensive operation. Tiny OS is a power efficient, component-based, event-driven operating system framework.
TinyOS in open-source operating system designed for wireless embedded sensor networks. It features a component-based architechture which enables rapid innovation and implementation while minimizing code size. TinyOS’s component library includes network protocols, distributed services, sensor drivers and data acquisition tools.
TinyOS software has three software components : command, event and tasks.


REFERENCES:

1.An Overview of Wireless of Sensor Network and Applications, V. Rajaravivarma, Yi Yang, and Teng Yang, Central Connecticut State University.
2. http://www.tinyos.net/
3. http://tinyos.stanford.edu/ttx/2007/
4. http://www.cs.berkeley.edu/~pal/research/tossim.html
5. Projects Using TinyOS : http://webs.cs.berkeley.edu/users/select_users.php

Note : This resume is created for self-learning only. Author and Publisher hold copyrights

February 02 2008,
Taipei City
High Speed Network Lab

Udin Harun

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