Abstract. Coverage is a problem area in Wireless Sensor Networks that determines
how well an area is monitored by the sensor network. One variation of the
coverage problem is Barrier Coverage. The main aim of barrier coverage is
to detect intruders as they penetrate the monitored area. A region is said to
be k-barrier covered when every crossing path through the region is detected
by at least k sensors.
Sensor nodes may fail due to several reasons such as environmental haz-
ards, lack of power supply etc. The failure of sensors after a certain extent,
deteriorates the degree of coverage provided by the sensor barriers and al-
lows intruder penetration through paths undetected by the sensor network.
Quality of barrier coverage is a measure of the degree of coverage provided by
the sensor deployment. If the quality of coverage degrades below a threshold
level, the network needs to be repaired. The degrade in the quality is due
to formation of gaps in the barrier or decrease in the length of overlapping
region in component of the deployment. Such components are termed as
segments. The first problem addressed in the thesis thus focuses on de-
termining the relationship between the quality of coverage and overlapping
region. Later on effect of a sensor failure on the number of such overlapping
region is discussed.
Improving the quality of coverage requires identifying the regions that
needs to be repaired. The network can be repaired by either re-deploying
all the sensors or moving sensors. Re-deploying of sensors is not always fea-
sible. Instead the method of relocation of few sensors to the region needs
to be repaired incurs less effort and is preferred for maintaining the cov-
erage. This gave a scope to design algorithms to improve the quality of
barrier coverage by relocating the sensors. The proposed algorithm gives
methods for detecting the best suitable sensor in the network that should
be relocated to the region that need to be repaired to improve the quality .
Firstly, a centralised algorithm to improve the quality by moving the sensors
horizontally is proposed. After that the algorithm to improve the quality by
moving the sensors horizontally as well as vertically in the given deployment
is proposed. Experimental results are presented to analyse the algorithms.