The document summarizes and compares several MAC layer synchronization protocols for wireless sensor networks, including IEEE 802.11, IEEE 802.15.4, S-MAC, T-MAC, and OB-MAC. It describes the operation and key features of each protocol, such as sleep schedules, synchronization techniques, and handling of channel contention. Simulation results using the NS2 simulator show that OB-MAC has the lowest energy consumption compared to the other protocols. The document concludes that all WSN MAC protocols are designed for energy efficiency and proposes further analyzing OB-MAC and collision handling through a hardware testbed implementation.

3. Sommaire
Protocol of synchronization
Design mac layer
outcomes
Conclusion
Introduction
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4. Introduction
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5. Introduction
The Wireless sensor networks are networks composed by a
large number of sensors nodes which are spread in the
environment to detect and activate their applications
The energy efficiency is one of the most important themes
in the field of the scientific research. The use of the wireless
sensor networks for diverse applications knew a very important
development.
The objective of this document is to realize a comparative
study between the existing protocols of the MAC layer of
synchronization and which are based on the contention.
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6. what is a network sensors and what does it?
We could define a sensor array as a set of interconnected
means by radio communication nodes, wherein each node must be
capable of self-without the need to configure any centralized
management
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The concept of wireless sensor networks is based on a simple
equation: sensor module + CPU + Radio = Thousands of potential
applications

7. Applications of Wireless Sensor Network
•
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8. Protocol of synchronization
The synchronized protocols were created to coordinate the phases
of awakening of nodes so that they wake up at the same time and so
can exchange their data, with no connectivity problems.
• The channel contention is a serious problem in WSNs resulting in
collisions, re-transmissions. In this paper, we focus on the MAC
layer problem with contention protocols oriented saving energy and
latency
 Several protocols using the technique of synchronization were
proposed. The most important of them are described below:
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9. Protocol of synchronization
Standard IEEE 802.11
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This standard specifies the characteristics of the physical
layer, as well as the medium access control (MAC) protocols in the
link layer,and provides two protocols for the MAC layer:
Distributed Coordination Function (DCF) and Point
Coordination Function (PCF).It’s proposed to encourage cooperation
between different modes of access to the channel.

10. Protocol of synchronization
Standard IEEE 802.11
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The standard IEEE 802.11 gives more priority than PCF mode
and DCF mode. After expiration of the PIFS, the base station has the
right to access the channel to disseminate scheduling channel
access time to all nodes.

11. Protocol of synchronization
Standard IEEE 802.15.4
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This standard works on two modes :
The mode not-beacon using CSMA / CA not Slotted
The mode beacon, using CSMA / CA Slotted
A model master-slave is adopted. The FFD takes the role of a
PAN coordinator.
In the topology peer-to -peer, a FFD can speak to other FFD in
its range of radio and can spend messages to other FFD .

12. Protocol of synchronization
Standard IEEE 802.15.4
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The super-frame is divided into an active part and an inactive
part. The first is divided into an interval of fixed size, that
contains a contention access period ( CAP) ,
Besides the coordinator raises no problem because both nodes
are active all the time.

13. Protocol of synchronization
Protocol S-MAC
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T Is one of the first synchronized protocols which improves the
IEEE 802.11,and it consists of dividing the time in periods of fixed
duration T
During sleeping, the node turns off its radio, and sets a timer
to awake it later. All nodes are free to choose their own listen/sleep
schedules
. Established of the radio-on and the radio-off.S-MAC reduces the
listen time by putting nodes into periodic sleep state.

14. Protocol of synchronization
Protocol T-MAC
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Timeout MAC (T-MAC) based on the protocol S-MAC and on the
attempts to limit the problems caused by this protocol.
. The Nodes choose their schedule as in S-MAC but the active
windows are not fixed in time, the interval of time varies according to
the traffic.
Adding package of control FRTS (future RTS) to indicate that the
transmission manages, and reduce the latency of the transmission
multi-soute..

15. Protocol of synchronization
protocol S-MAC and T-MAC
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The following figure presents a Comparison between two periods
active / inactive for both protocols S-MAC and T-MAC

16. Protocol of synchronization
Protocol OB-MAC
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The main point of the Overhearing Based is to reduce
the energy consumption, this includes two tasks:
Reduce the running time of the transceiver
Reduce the number of redundant communication.
We illustrate the operation of OB-MAC on both synchronization
protocols for access to S-MAC and IEEE 802.15.4 medium

17. Protocol of synchronization
Protocol OB-MAC on IEEE802.15.4
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The figure 4 shows an example of operation of the OB-MAC in
the standard 802.15.4

18. Protocol of synchronization
Protocol OB-MAC on S-MAC
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We apply OB-MAC on S-MAC because S-MAC is a typical
example of the family synchronized MAC ,and here is the protocol of
functioning

19. Free Powerpoint Templates
MAC layer design

20. Our contribution
Design mac layer?????
Simulation under NS ???
The laency??
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 The objective of the MAC layer is decomposed into two parts: the first
part is the creation of the infrastructure of sensor networks.
Energy eficiency ??
 And the second part is the division of the communication channel in
an effective way for the transfer which respect the following criteria:

21. MAC layer design
Energy eficiency
 The energy consumption is a very important factor in the
WSN, they nodes are feed by batteries, but it is often very
difficult to change them .
The latency
 It is the interval of time between the times or event occurs
and the time or the base station receives the information of
this event.
 The NS project was launched in 1989 as a variant of the
simulator REAL network simulator. It’s evolves in the conger
of the contributions ofits users .
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Simulation under NS

22. Simulation under NS2
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, we find according after the results that the energy consumption
in the protocol IEEE802.11 is very raised with regard to the other
protocols such as IEEE802.15.4, S-MAC, T-MAC and the OB-MAC

23. Simulation under NS2
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. We notice that the OB-MAC consumes less energy than to the
other protocols

24. Simulation under NS2
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We notice that the IEEE802.11 gives a very important latency
comparing to the other protocols because the IEEE802.11 uses the
packages of control as RTS, CTS and ACK to avoid the problem of the
collision

25. Conclusion

26. Conclusion and
perspective
• In this paper, we presented and analyzed the functioning of
synchronization protocols medium access in the simulator as
well as in the real case. In the various protocols medium
access, the passive listening is always considered as a source
of wasting of energy.
 All WSN MAC protocols are designed with the goal to
conserve energy
 Choose the protocol OB-MAC and looking for collision
problems realize plate forme witch hard in labo
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