In Section
5, we briefly point-out a deficiency of the current implementation of the
energy model in NS2 [24] network simulator. We end our presentation with
conclusions in Section 6.
2 Characteristics of MAC Protocols in WSNs
A MAC protocol is mainly responsible for providing a mechanism that controls
access to the shared communication medium. The specific characteristics of a
WSN determine the requirements of the MAC protocol. It is impractical to
use the MAC protocols designed for other wireless network types. New MAC
protocols have to be designed, specifically tailored for the characteristics of
WSNs. Next, we present the main requirements of MAC protocols for WSNs
and their classification, followed by a discussion of energy-e?±cient design of
MAC protocols.
2.1 Requirements of MAC Protocols in WSNs
The main requirements of a traditional wireless network MAC protocol are
per-node fairness, low delay and high throughput. Network lifetime is not
considered critical, as batteries might be replenished, although power e?±cient
schemes are recommended.
In contrast, for a WSN, an energy-e?±cient design is considered as the top
priority. The design should also be scalable, in order to accommodate large
networks. Latency and bandwidth utilization become secondary goals, while
per-node fairness is not considered a critical parameter. The main requirements
of a MAC protocol for WSNs can be summarized as follows [16, 17]:
1.
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