Introduction to Wireless Sensor Networks

Presented by Sushanth Sivaram Vallath

The most profound technologies are those that disappear. They weave themselves into the fabric of everyday life until they are indistinguishable from it.

- The late Mark Weiser, Father of Ubiquitous Computing and Chief Technologist of Xerox PARC

Wireless Sensors

Small microcontroller 8 kB code 512 B data

Simple, low-power radio 10 kbps ASK

EEPROM (32 KB)

Simple sensors

WeC 99“Smart Rock”

Mica 1/02

NEST open exp. Platform128 kB code, 4 kB data40kbps OOK/ASK radio512 kB Flash

Rene 11/00

Designed for experimentation

-sensor boards

-power boards

Dot 9/01

Demonstrate scale

Spec 6/03“Mote on a chip”

Telos 4/04RobustLow Power250kbpsEasy to use

Mica2 12/0238.4kbps radioFSK

Tiny sensing devices capable of wireless communication

What are sensor networks

spatially distributed sensors to monitor conditions at different locations, such as temperature, sound, vibration, pressure, motion or pollutants.

Platforms

• Berkeley Motes

• Tiny OS

• nesC

• Ns-2

• TOSSIM

Applications of WSN

• Temperature• Humidity• Vehicular movement• Pressure• Noise levels• Mechanical stress levels on attached objects • Speed, direction• Etc…

Factors Influencing Sensor Network Design

• Fault tolerance

• Scalability

• Operating environment

• Sensor network topology

• Transmission media

• Power consumption

Sensors Representation

• Communication Graph– Sensors are nodes– Link between the sensors are the edges

Routing Protocols

• LEACH

• Directed Diffusion

• PEGASIS

• TEEN

• APTEEN

• Etc…

Sensor Issues

• Energy Constraint

• High Communication cost

• & Lot of other issues

Management Issues

• Conversion of data to Information

• Data access control

SQL

• Underlying routing protocol transparent to user

• Some routing protocols are considered to be aggregation protocols (implicit aggregation)

Sensor Database

• SQL type interface

– SELECT avg(temperature), room,

FROM sensors

WHERE building = “Nedderman Hall”

ORDER BY temperature

GROUP BY room

SAMPLING PERIOD 10 min

SQL type interfaces

• Cougar

• TinyDB

Approximations

Query Propagation

Data Centric Storage

Aging Data

Query scenario

SinkSelect temp from

Efficiency achieved through

In-network aggregation

Different types of queries

• Fully aggregated queries

• Un-aggregated queries

• Partially aggregated queries

Fully aggregated queries

Theorem: Finding maximum lifetime routing tree for fully aggregated queries with reception costs is NP-complete.

Similar to Minimum Degree Spanning Tree(MDST) which is known to be NP-complete

Un-aggregated queries

Theorem: Finding maximum lifetime routing tree for unaggregated queries is NP-complete.

Reduced from decision problem for SET-COVER.

Partially aggregated queries

Can be reduced to unaggregated queries

Approximation algorithms used to solve the unaggregated routing tree problem can be adapted.

Active areas in WSN

• Routing• Topology control• Data management, aggregation and query• MAC protocols• Target tracking, resource discovery• Monitoring and maintenance• Sensor validation• Power issues• Coverage and Connectivity

Companies in Research

• Crossbow• Intel• IBM• Microsoft• PARC• Fujitsu• Lot more…

References[1] Cedric Florens and Robert McEliece, “Packet Distribution Algorithms for Sensor Networks”, IEEE INFOCOM 2003.[2] Samuel Madden, Robert Szewczyk, Michael J. Franklin and David Culler, “Supporting Aggregate Queries Over Ad-Hoc Wireless

Sensor Networks”,[3] Sartaj Sahni and Xiaochun Xu, Algorithms for Wireless Sensor Networks. [4] Jamal N. Al-Karaki Ahmed E. Kamal, Routing Techniques in Wireless Sensor Networks: A Survey.[5] Bhaskar Krishnamachari, D Estrin, Stephen Wicker, Modeling Data-Centric Routing in Wireless Sensor Networks.[6] S.S Iyengar, Richard R. Brooks, “Distributed Sensor Networks”, Chapman & Hall/CRC.[7] Wendi Rabiner Heinzelman, Anantha Chandrakasan, and Hari Balakrishnan, “Energy-efficient communication protocol for wireless

microsensors networks,” in 33rd Annual Hawaii International conference on System Sciences.[8] David Braginsky and Deborah Estrin, “Rumor routing algorithm for sensor networks,” in First ACM International Workshop on

Wireless Sensor Networks and Application.[9] Y.Xu, J. Heidemann, and D. Estrin, “Geography-informed energy conservation for ad hoc routing,” in Proceedings of the Seventh

Annual ACM/IEEE International Conference on Mobile Computing and Networking, 2001.[10] B. Chen, K. Jamieson, H. Balakrishnan, and R. Morris, “SPAN: An energy-efficient coordination algorithm for topology maintenance

in ad-hoc wireless networks,” ACM Wireless Networks Journal, September 2002.[11] Feng Zhao and Leonidas Guibas, “Wireless Sensor Networks, an Information Processing Approach”.[12] Yong Yao, J. E. Gehrke. The Cougar Approach to In-Network Query Processing in Sensor Networks. Sigmod Record, Volume 31,

Number 3. September 2002.[13] Yong Yao, J. E. Gehrke. Query Processing in Sensor Networks. In Proceedings of the First Biennial Conference on Innovative Data

Systems Research (CIDR 2003). Asilomar, California, January 2003.[14] Xiuli Ma, Dongqing Yang, Shiwei Tang, Qiong Luo, Dehui Zhang, and Shuangfeng Li. Online Mining in Sensor Networks. NPC

2004: 544-550[15] Chiranjeeb Buragohain, Divyakant Agrawal, and Subhash Suri, Power Aware Routing for Sensor Databases.

Thank You