dc.description.abstract | In this thesis we present the requirements needed for a Condition Based Main-
tenance (CBM) solution by using Wireless Sensor Networks(WSN).
The sensor network needs to be secure and reliable to be implemented in a
CBM solution, hence we have chosen the popular ZigBee protocol to see how it
fulfill the reliability requirements of transmission delay, lost packets and battery
consumption. The security requirements is based on the CIA(confidentiality,
integrity, availability) triad for security objectives, and in this thesis we will give
a general overview of the security mechanisms used in ZigBee to achieve these
requirements. Also a brief overview of threats a WSN faces is also presented.
Practical experiments for testing delay, battery consumption and environ-
mental interference from magnetic fields has been conducted using XBee units
from Digi International. These tests shows that the transmisson delay is within
acceptable levels, and the battery consumption for sensors allows them to run
for several years.
Another contender for use in industrial processes is WirelessHART by HART
Communication foundation. Like ZigBee, WirelessHART is based on the IEEE
802.15.4 standard for wireless personal area networks. However WirelessHART
has a dfferent specification for the data-link layer than ZigBee and offers funda-
mental differences like Time Division Multiple Access and Frequency Hopping
Spread Spectrum while ZigBee uses Carrier Sense Multiple Access and Direct
Sequence Spread Spectrum. | en |