1. In the name of God

2. A Survey on Fault Tolerance Techniques in Wireless Sensor Networks
Presented by :
Gholamreza Kakamanshadi
ICGCIoT 2015

3. CONTENTS Introduction Fault Tolerance in WSN
Existing Techniques for FT in WSN
Conclusion and Future Directions

4. INTRODUCTION Low cost Low power consumption Low memory
Wireless Sensor Networks
Low cost
Low power consumption
Low memory
Low computational power
WSN is a self organized network.

5. Sensor Nodes collaborate with each other to perform tasks of:
Sensing
Computing
Communication
Group of sensors linked by wireless media to perform distributed sensing tasks.

6. Applications of WSNs Military Commercial Health care monitoring Space
Environmental monitoring
Battle fields surveillance
…..

7. Fault Tolerance in WSN Failure is part of the WSN.
Why Fault Tolerance in WSN?
Failure is part of the WSN.
Due to their deployment in hostile or harsh environments, unknown area, Limited power, Malicious and so on, Sensor Nodes are prone to failure.
Faulty Sensor Nodes cannot perform any monitoring of task properly.
Faulty Sensor Nodes should be recognized timely, and should be excluded from the data collection process to ensure the overall data quality.

8. Fault tolerance is a key element for reliable data delivery in wireless sensor network applications.
Fault tolerance is the ability to sustain sensor network functionalities without any interruption due to sensor node failures.

9. Existing Techniques for FT in WSN
There are many strategies to achieve fault tolerance in wireless sensor networks. Deployment based, Clustering based, Redundancy based etc.

10. Existing Techniques for FT in WSN

11. Redundancy based mechanisms and Fault tolerance
Many researchers have investigated various mechanisms based on redundancy in WSNs, such as:
Path redundancy
Time redundancy or Temporal redundancy
Data redundancy
Node redundancy or Physical redundancy.
These mechanisms are used to achieve energy efficiency, ensure the reliability, security and FT in WSNs.
For instance, in dynamic sensing environments, time redundancy is used whenever parameters like weather conditions quickly change in time. Furthermore, in this case, the computation or data sending is repeated and the result is compared with the previous output in order to increase reliability.

12. Major features achieved
S. No.
Mechanism(s)
Redundancy types
Major features achieved
Node
Data
Path
Time 1
FEEM, EM-GMR [17] *
1) Energy efficiency
2)Tolerant link failure 2
Distributed fault detection method [18]
1)High fault detection accuracy 3
IHR [19]
1)Energy efficiency
2)Data loss rate 4
FTLBS [20]
1)Data accuracy with minimum delay 5
Coverage and Connectivity based fault tolerance [21]
1)Packet loss rate

13. Clustering based mechanisms and Fault tolerance
Scalable control of WSNs can be done by clustering, uses of clustering mechanism effect on energy saving and control over the network.
Clustering mechanism is useful to achieve local communication in which each CH receives data from cluster members and sends aggregated data to the BS named as single hop communication.
On the other hand, data gathered can be transferred to the BS via multiple hop communications.
Failure of CH is inevitable in WSNs; therefore, that is a need for adaptive fault tolerant clustering mechanism.

14. Major features achieved
S. No.
Mechanism(s)
Clustering types
Major features achieved
Single hop
Multiple hop
Hierarchical 1
CMATO [22] *
1)Energy efficiency
2)Fault coverage 2
FTEP [23]
1-Energy efficiency 3
FTTCP [24]
1)High fault detection accuracy 4
FT-DSC [25]
2)Reliability 5
ILP [26]
2)Lifetime 6
Novel flexible, hierarchical clustering method[27] 7
Fuzzy knowledge based Fault tolerance [28]
1)Reliability 8
Clustering coefficient and Fault tolerance [29]
1)Degree of fault tolerance 9
Distributed fault tolerant algorithm[30]
1)Event detection accuracy
2)Fault detection accuracy
3)False alarm rate

15. Deployment based mechanisms and Fault tolerance
Careful deployment of SNs in WSNs can lead to effective design goals.
Pre deployment of SNs that is called design of the network.
During deployment of SNs.
After deployment of SNs.
Network topology may changes due to dislocation of SNs, sensor nodes failure, or other conditions. Moreover, connectivity of SNs may also change due to noise, interference, etc.
Therefore, topology control algorithms are required to increase the network lifetime. Moreover, topology control methods in fact decrease the degree of routing redundancy by decreasing the number of communication links in the WSN.

16. Major features achieved
S. No.
Mechanism(s)
Deployment types
Major features achieved
Topology design
Topology control 1
Topology control algorithm [31] *
1)Energy efficiency
2)Higher network capacity
3)Network connectivity 2
FT and energy efficient topology control protocol [32] 3
ER-MAC [33]
1)Reliability and fast delivery
2)Robustness against single failure 4
AFTC [34]
2)Fault tolerant capability
3)Reliability 5
Robust recovery mechanism[35]
1)Energy efficiency for area failure 6
Trust framework for data aggregation with FT [36]
1)Data accuracy of multimedia data
2)Reliability 7
Active node based Fault Tolerance[37]
1)Data delivery ration
2)Memory overhead
3)Control overhead
4)Failure recovery delay

17. Conclusion and Future Directions
Adding few redundant components can increase level of FT and enhance data accuracy. Efficient clustering can improve energy consumption and increase lifetime of the system. Attention to the deployment phase can drastically save the energy, increase the lifetime and enhance the reliability of the network.

18. Conclusion
Most of the researchers investigated considering only one base station in the network where in large-scale WSNs, we need to consider multiple BSs in order to save energy and to increase fault tolerant against BS failure.
Area based failures can be considered, where failed devices are in close proximity to each other.

19. The presented mechanisms are limited to smaller networks, consideration for large-scale networks is required and distributed approach can be developed.
A WSN can be interrupted by malicious attacks. In order to achieve security goals for WSNs, there is a need to design and develop specific mechanism with respect to FT.

20. Thank you