The way to provide time synchronization
for sensor networks may be di?®erent for di?®erent applications. The current
timing techniques that are available for di?®erent applications are described in
the following section.
6 State-of-the-Art Time Synchronization Protocols
Since time synchronization is to synchronize the time within the sensor networks,
the timing techniques are methods/protocols that achieve this. There
are three types of timing techniques as shown in Table 2, and each of these
types has to address the factors and design challenges a?®ecting time synchronization
as mentioned in Sections 3 and 4, respectively. In addition, the
timing techniques have to address the time representation di?®erences between
the sensor networks and the Internet, e.g., universal coordinated time. For
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Chapter 9 Time-Synchronization Challenges and Techniques
Table 2. Three types of timing techniques.
Type Description
(1) Relies on fixed time servers -The nodes are synchronized to time
to synchronize the network servers that are readily available.
These time servers are expected to
be robust and highly precise.
(2) Translates time throughout -The time is translated hop-by-hop for
from the network the source to the sink. In essence, it
is a time translation service.
(3) Self-organizes to synchronize -The protocol does not depend on
the network specialized time servers. It
automatically organizes
and determines the master nodes as
the temporary time-servers.
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