These sensor nodes can monitor the environment by
collecting information from their surroundings, and work cooperatively to send the
data to a base station, or sink, for analysis.
However, currently there are two limitations on these sensor nodes. First, the
power supply is limited. Without electric infrastructure, the nodes are powered by
batteries. Once the batteries run out of energy, the nodes die. Battery replacement
is not economic, and sometimes infeasible. The sensor nodes will be very cheap
once they are mass production products. Deploying new sensor nodes will be more
economic than human power. Sometimes the sensor network may be deployed in a
hostile or unreachable environment, such as a battle field or chemical waste disposal,
and therefore it is not possible for a human to replace a depleted battery.
Second, the bandwidth of the radio transceiver is limited. Unlike the current
802.11 wireless LAN which can reach up to 54Mbps, current radio transceivers of
these sensor nodes can only reach to a few hundreds Kbps, and some only have 30
?» 40 Kbps. Therefore the amount of data that can be transmitted within the sensor
network is limited.
To reduce energy consumption and traffic load of a sensor network, the amount
of the data transmitted in the network must be reduced. Consider the dynamics of
a sensor network. It collects data from its surrounding environment. This data is
usually highly correlated within the sensor??™s area, thus the data collected by sensor
nodes close to each other is usually closely related.
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