Wireless Sensor Networks 113
environmental. They differ from MANETs in that the number of nodes is much larger and the
computing power is much lesser.
Many routing algorithms have been designed for WSNs. These can be divided into datacen-
tric protocols, hierarchical protocols and protocols based on location. The more important ones
among these are SPIN, LEACH, PEGASIS, TEEN and APTEEN.
The Mica mote kit was one of the earliest WSN nodes developed and has been usefully em-
ployed and tested for such diverse applications as aiding the movement of visually handicapped
persons and for sensing and reporting fires. TinyOS is an example of a real-time operating system
that has been specifically designed for such WSN nodes.
In the next chapter, we will discuss the handheld devices used in mobile computing, their
characteristics and their underlying operating systems.
Problems
1. Explain clearly the differences between WSNs and other types of ad hoc networks.
2. Many applications have been given in the chapter for WSNs. Choose any given application
and identify the design of the WSN for it.
3. For the above design, list the important security issues to be taken care of.
4. Compare and contrast the use and benefit of RFIDs vs. WSNs in a typical industrial environment.
5. Can the topology of a WSN change, even if there is no mobility? Discuss your answer.
6. Wireless sensor nodes are being increasingly deployed in the human body. What are the special
security requirements of such biomedical sensors?
7. The energy consumed by different functions in a sensor is not the same. List the typical
amounts of such consumption, for functions like aggregation, communication to cluster
head, cluster head to BS, sleeping mode, sensing mode, etc.
8. Draw a table to compare and contrast the various routing algorithms used in WSN. List the
items in terms of the parameters used for comparison.
9. Download the TinyOS or any other open source operating system available for WSN and
implement and test a simple protocol with it using a simulator.
10. Suppose that a nuclear plant building of size 20 20 sq. metres and height 10 metres is to be
fitted with wireless sensors. If the sensors have a transmit/receive range of 2 metres, what
would be an efficient arrangement of the sensors? Discuss.
Multiple-choice questions
1. Smart dust is a synonym for which of the following?
(a) Wireless sensor networks
(b) Mobile ad hoc networks
(c) Wearable computers
(d) Both (a) and (c)
2. The kind of computing where computers become so small and so omnipresent that they fade
into the background is known as
(a) Soft computing
(b) Pervasive computing
114 Mobile Computing
(c) Hard computing
(d) None of the above
3. Which one of the following is true for the statements X and Y?
X: Sensor nodes mainly use the broadcast communication paradigm
Y: Most ad hoc networks are based on point-to-point communication
(a) X is true but Y is false
(b) X is false but Y is true
(c) Both X and Y are true
(d) Both X and Y are false
4. Which of the following layers is not present in WSN (wireless sensor network) communica-
tions architecture?
(a) Physical layer
(b) Data link layer
(c) Presentation layer
(d) Application layer
5. Which one of the following balances and schedules the sensing tasks given to a specific region?
(a) Power management plane
(b) Task management plane
(c) Mobility management plane
(d) Balance management plan
6. Which of the following protocols are query-based and depend on the naming of desired
data, which helps in eliminating many redundant transmissions?
(a) Data-centric protocols
(b) Hierarchical protocols
(c) Location-based protocols
(d) None of the above
7. A process where the receiving node sends the packet to a randomly selected neighbour,
which picks another random neighbour to forward the packet to, and so on is known as
(a) Flooding
(b) SPIN
(c) LEACH
(d) Gossiping
8. Which one of the following algorithms avoids the problem of implosion by just selecting a
random node to send the packet rather than broadcasting?
(a) Flooding
(b) LEACH
(c) Gossiping
(d) SPIN
9. Which one of the following is a hierarchical protocol designed to respond to sudden changes
in the sensed attributes, such as temperature?
(a) LEACH
(b) PEGASIS
(c) TEEN
(d) Gossiping

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