Wireless Sensor Networks pt 1: Introduction - Sensor Node Features
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Comparing Sensor Nodes to Ad-hoc Wireless Networks
Wireless sensor networks share similarities (and differences) with ad-hoc wireless networks. The main similarity is the multi-hop communication method. The differences among the two types of networks are listed below:
- More nodes are deployed in a sensor network, up to hundred or thousand nodes, than in an ad-hoc network that usually involves far fewer nodes.
- Sensor nodes are more constrained in computational, energy and storage resources than ad-hoc.
- Sensor nodes can be deployed in environments without the need of human intervention and can remain unattended for a long time after deployment.
- Neighboring sensor nodes often sense the same events from their environment thus forwarding the same data to the base station resulting in redundant information.
- Aggregation and in-network processing often requires trust relationships between sensor nodes that are not typically assumed in ad-hoc networks.
Sensor Node Hardware Architecture
Sensor nodes are minute. The following figure presents the Mica2 sensor node, which is the most popular research platform at the moment.
As you can see, the main components of a typical sensor node include an antenna and a radio frequency (RF) transceiver to allow communication with other nodes, a memory unit, a CPU, the sensor unit (i.e. thermostat) and the power source which is usually provided by batteries. The operating system running on sensor nodes is called TinyOS and was initially developed at theUniversityofCalifornia,Berkeley. TinyOS is designed to run on platforms with limited computational power and memory space.The programming language of TinyOS is stylized C and uses a custom compiler called NesC. Though it may work on other platforms, the supported platforms are Linux RedHat 9.0, Windows 2000, and Windows XP. Further information you may obtain from the official TinyOS website http://webs.cs.berkeley.edu/tos/.
The following table lists some of the capabilities of the current sensor network platforms organized by device class as presented in the paper, “The platforms enabling wireless sensor networks” written by Jason Hill, Mike Horton, Ralph Kling and Lakshman Krishnamurthy, and is published by the ACM.
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