| Summary: | 博士 === 國立成功大學 === 電腦與通信工程研究所 === 102 === In wireless sensor network applications, it is a fundamental requirement to maintain essential sensing coverage and network connectivity for ensuring the successful operations of sensing environmental information and sending data to the backend center. However, owing to the limitation of energy supply of the sensor devices, it is unavoidable that the failures of sensor devices will result in coverage holes and topology disconnections. Topology control approaches can effectively adjust and balance the energy consumption of sensor devices. However, due to the limitations of energy resources, extending the lifetime of the network is very limited. The healing method for the failure of wireless sensors is discussed in this thesis. The healing approach is the main method we proposed to keep the system continuously working well, and make the wireless sensor network maintain a high sensing coverage rate and good topological connectivity. In this study, we use mathematical methods to analyze the relationship of healing parameters, such as residual energy of sensors, number of redundant nodes and dispatching speed, to gradually repair the failed nodes and analyze the feasibility of proposed strategies to confirm the parameters in the healing process and keep the system be well functioning. A distributed healing method is subsequently proposed in this thesis, which discusses the healing of coverage holes by the mobile sensor nodes that uniformly deployed in the sensing environment. The mobile sensors located around the boundary of a hole will be invited to heal the hole. This approach can reduce the movement distance of a healing device and thus the energy consumption can be also reduced.
When several coverage holes occur in the surveillance field, the priority of the holes to be healed may affect the efficiency of the healing process and the system. Thus, some relevant factors of the holes should be evaluated before the healing process. The evaluation performed in this study is focused on the impact degree of holes on system efficacy, which the factors involves the hole area, distance and influence of the data transmission. Impact degree of each factor on the system efficiency is assigned with a respective weight. After the calculation of the weight for each hole, the total value of weighted degree is used to decide the priority of selecting a hole to heal and the corresponding healing path. It aims to provide the appropriate conditions for topology control and reduce the time delay of data transmission in the wireless sensor network.
|
|---|
