Development of a Modified Real-time Fault-tolerant Task
Allocation Scheme for Wireless Sensor Networks
CHAPTER ONE
Aim and Objectives
The aim of the research is the development of a modified real-time fault-tolerant task allocation scheme (mRFTAS) for WSNs.
The following are the objectives of this research work:
- Development and implementation of the mRFTAS using active replication backup techniques.
- Development of a graphical user interface (GUI) for simulation of sensor nodes in WSNs using real-time fault tolerant task allocation scheme (RFTAS) and mRFTAS respectively called the task allocation scheme simulator (TASS).
- Comparison of the performance of mRFTAS and RFTAS using task execution time, energy consumption, reliability cost and network lifetime as the performance metrics.
CHAPTER TWO
LITERATURE REVIEW
Introduction
The chapter encompasses the review of essential concepts fundamental to the research and a review of similar and related works in the area of fault-tolerant task allocation scheme for WSNs.
Review of Fundamental Concepts
Fundamental concepts such as wireless sensor networks (WSNs), fault tolerance and task allocation schemes, are discussed in this sub section in addition to the basics of the performance metrics considered in this study.
Wireless sensor networks (WSNs)
A WSN is a network created by a sizeable number of sensor nodes where respectively nodes are equipped with a sensor to sense physical phenomena such as light, pressure and heat(Bröring et al., 2011). WSNs are considered as a revolutionary data gathering scheme to build the communication and information system which will significantly enhance the reliability and effectiveness of infrastructure schemes. Associated along with the wired solution, WSNs attribute is easier deployment and enhanced the flexibility of devices. Along with the fast technological growth of sensors, WSNs will turn out to be the central technology for (Internet of things) IoT (Matin & Islam, 2012). WSNs can largely be termed as networks of nodes that jointly sense and could control the environment, consequently enabling communication between computers or human beings and the immediate location (Presser et al., 2009). In reality, the act of sensing, processing and communicating with a reduced quantity of energy, ignites a cross-layer design style typically necessitating the collaborative consideration (Matin & Islam, 2012) of distributed signal/data processing, medium access control and communication protocols (Bröring et al., 2011).
CHAPTER THREE
MATERIALS AND METHODS
Introduction
In this chapter, the materials, the methods used for the implementation, development and simulation of the RFTAS and mRFTAS are described in details based on the outline developed.
CHAPTER FOUR
RESULTS AND DISCUSSIONS
Introduction
In this section, the performance of the real-time fault-tolerant task allocation scheme and that of the modified real-time fault-tolerant task allocation scheme of the WSNs, with processing time delay and fault-tolerant problem are discussed and appropriate results reported.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
Summary
RFTAS is a task allocation scheme that was modelled based on the principle of the fault tolerance ability of a system (such as the WSN). This is to ensure that the system keeps processing even when there is sudden failure of a component (e.g. node of the WSN) of the system. The RFTAS was developed based on the issues associated with real-time task allocation in WSNs using the backup copies techniques. The passive replication backup technique, which is the most commonly used technique for the RFTAS, has the problem of processing time delay. This is as a result of the delay arising from the backup task copy activation. Processing time delay in systems that are safety- or security-critical can be inimical to lives and properties. In order to overcome the problems associated with the RFTAS in terms of fault tolerance and processing time delay, the mRFTAS using active replication backup copy
technique was developed. A GUI-based simulator called the TASS was developed using Visual Studio 2015 and
simulations involving the RFTAS and mRFTAS were carried on task allocation involving 400 tasks amongst a different number of nodes in a WSN. Analyses were carried out on the performance of the RFTAS and the mRFTAS using the following metrics: energy consumption, task execution time, reliability cost and network lifetime. The results indicated that mRFTAS performed better in terms of reducing the task execution time and reliability cost
while increasing the network lifetime by 28.65%, 7.29% and 22.26% respectively when compared with the RFTAS but with a trade-off in energy consumption (with -17.32% performance measure)
Conclusion
This research developed the mRFTAS using the active replication backup technique for addressing the real-time fault tolerance and processing time delay in WSNs by reducing the task execution time and reliability cost and increasing the network lifetime but at the expense of energy consumption, A GUI was developed for simulation of real-time task allocation using mRFTAS and RFTAS for WSNs called the TASS.
The comparisons of the performance of mRFTAS and RFTAS were carried out for energy consumption, task execution time, reliability cost and network lifetime. The mRFTAS outperformed the RFTAS in all the metrics except for energy consumption.
Significant Contributions
The significant contributions of this research work are as follows:
a) Development of a C# based GUI model for real-time fault-tolerant task allocation scheme (mRFTAS) for WSNs using active replication backup technology.
b) The mRFTAS produced a performance improvement of 28.65% over RFTAS for task execution time, 7.29% improvement in reliability cost and 22.26% improvement in network lifetime. The mRFTAS failed to perform better than the RFTAS in term of energy reduction, its performance was -17.32%
Recommendations for Further Work
The following possible areas of further work are recommended for consideration for future research:
a) The research conducted did not consider the presence of malicious nodes, thus further work can be carried over by implementing security.
b) The modified Real-time Fault-tolerant task allocation scheme can be further modified for minimization of energy consumption and task execution time in WSNs.
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