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sensors placed on the ground or floating on water experience greater attenua-
tion and consequently require higher transmit power. The choice of modulation
scheme is one of the prime factors in deciding the transmit power. The modula-
tion scheme decides the bit error rate (BER), spectrum efficiency, and number of
bits per symbol. For example, an M-ary modulation scheme is able to transmit
more bits per symbol than other binary modulation schemes such as Phase Shift
Keying (PSK). However, M-ary schemes result in higher BER and require more
transmit power than the binary modulation schemes. Hence binary modulation
schemes are more applicable to WSN.
Mobility plane: Sensor nodes can be fixed on moving objects such as animals,
vehicles, people, etc; which will lead to a dynamic topology. In the event of some
mobility by sensor nodes, the mobility in collaboration with the network layer is
responsible for maintaining the list of active neighboring nodes. It is also respon-
sible for interacting periodically with other neighboring nodes' mobility planes,
so that it can create and maintain a table of active, power-efficient routes.
Power plane: The power plane focuses on the awareness of power at each hori-
zontal and vertical layer. It is responsible for shutting off the sensors if they are
not participating in any routing decisions or simply if the sensing activity is com-
plete. Power planes of each node work collectively on deciding efficient routes to
sink nodes and maintain the sleep/awake cycles of sensor nodes.
Ta sk m a n a ge m e n t pl a n e: The task management plane is responsible for achiev-
ing a common goal by taking properties of each layer and across each layer in a
power-aware manner.
1.6 MANET Versus WSN
A mobile ad-hoc network (MANET) is a network of mobile nodes communicat-
ing through a wireless medium and with an ability to self-configure itself (Tavli and
Heinzelman 2005). The ability of each node to move freely in any direction results in
a topology that is very dynamic. MANET has been studied for decades and is closely
related to WSN. However, recent research work has shown that WSN can be catego-
rized as a separate research topic. Let us look at the similarities and dissimilarities of
MANET and WSN.
1.6.1 Similarities Between MANET and WSN
MANET and WSN are both wireless ad-hoc networks with distributed architectures.
The nodes in both types of network are powered by batteries. Intermediate nodes in
each of the networks may be involved in routing decisions. One of the major drawbacks
to both types of network is that they operate in an unlicensed spectrum, resulting in
radio interference from other radio technologies. Self-management is a key feature in
both types of network.
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