2 Sensor Network Nodes
There are few sensor network nodes in which sensor networks may be built
for testing/research. These nodes are listed below:
??? MICA Mote [13]: It has a 4 MHz clock and runs on the 915 MHz band.
Newer generation of mote runs on 2.4 GHz band. In addition, the mote
runs on TinyOS operating system.
??? XYZ Sensor Node [12]: It has a ML67 series ARM /THUMB microcontroller
from OKI Semiconductor and a CC2420 Zigbee compliant radio
from Chipcon. In addition, the platform is open-source.
??? Scatterweb Node [17]: It operates in the 868 MHz to 915 MHz band and
utilizes frequency hopping. It also has bluetooth and WLAN capabilities.
??? Intel Mote [9]: It has an integrated wireless microcontroller consisting of
an ARM7 core, a Bluetooth radio, RAM and FLASH memory as well as
various I/O options. In addition, it runs on TinyOS operating system.
Each of these nodes uses di?®erent technology. Thus, the timing precision
of each will be di?®erent. In addition, each of these nodes will have to address
the factors a?®ecting time synchronization. The factors a?®ecting the quality of
synchronized time are described in the following section.
3 Influencing Factors
A time synchronization protocol has to address some of the inherent factors
that influence the quality of the synchronized time. In addition, small and
low-end sensor nodes may exhibit device behaviors that may be much worse
than the large systems such as personal computers (PCs).
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