In fact, this match-making method only performs well when the network is
dense enough or source and destination nodes are close to each other.
Figure 7 (from [28]) compares the success rate and forwarding rate (number
of forwarding nodes divided by n) for quorum-based and match-making
methods for n=100 nodes in the network, respectively. The transmission radius
of node varies from 13 to 40. According to the comparison, the quorum
based scheme can achieve a much higher success rate and requires about 30
percent of its nodes to forward messages. It is an energy e?±cient method to
deal with data accessing transactions. Although the match-making protocol
requires fewer nodes to forward packets, it is at the sacrifice of a much lower
success rate.
4 Object Tracking
Object tracking is one of the most important applications of WSNs in our
society, especially for military usage. Assume existence of a battlefield, within
which some tanks and soldiers are patrolling around. Thousands of sensor
nodes are deployed in an unattended fashion. They should collect information
about intruders and sound alarms to the military in good time. On one hand,
once sensor nodes detect a new object moving into its surveillant scope, they
should generate robust and reliable sensing reports, and forward the report
quickly and e?±ciently to the multiple data sinks (moving soldiers or static
command centers) that have interest in it [38].
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