-In the second part of the dissertation, We have designed a new three different optimization protocols, which schedules nodes’ activities (wake up and sleep stages) with the objective of maintaining a good coverage ratio while maximizing the network lifetime in WSNs. This part proposes a two-step approaches. Firstly, the field of sensing is divided into smaller subregions using the concept of divide-and-conquer method. Secondly, one of the proposed optimization protocols is applied in each subregion in a distributed parallel way to optimize the coverage and lifetime performances.
+In the second part of the dissertation, We have designed a new three different optimization protocols, which schedules nodes’ activities (wake up and sleep stages) with the objective of maintaining a good coverage ratio while maximizing the network lifetime in WSNs. This part proposes a two-step approaches. Firstly, the field of sensing is divided into smaller subregions using the concept of divide-and-conquer method. Secondly, one of the proposed optimization protocols is applied in each subregion in a distributed parallel way to optimize the coverage and lifetime performances. The proposed protocols combine two efficient mechanisms: network leader election and sensor activity scheduling, where the challenges include how to select the most efficient leader in each subregion and the best
+representative active nodes that will optimize the network lifetime while taking the responsibility of covering the corresponding subregion.
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+In chapter 4, we have proposed an optimization protocol, called Distributed Lifetime Coverage Optimization protocol (DiLCO), which optimizes the coverage and the lifetime of a wireless sensor network. DiLCO protocol is distributed in each sensor node in the subregions of the sensing field. It has been implemented in each subregion simultaneously and Independently. The proposed DiLCO protocol is a periodic protocol where each period consists of 4 phases: information exchange, leader election, decision, and sensing. The sensor nodes collaborate in each subregion to elect the leader. The leader applies activity scheduling based optimization so as to provides only one optimal set of active sensor nodes that takes the mission of sensing during this period. The performance of our DiLCO protocol has been evaluated by a series of simulations. We have presented a comparison between our proposed protocol and other two existing and known in the literature, DESK and GAF. The experimental results have validated our protocol and showed their efficiency in the optimization of the coverage and the lifetime compared to existing methods.
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+Next, we propose a method called Multiround Distributed Lifetime Coverage Optimization protocol (MuDiLCO) in chapter 5, to maintain the coverage and to improve the lifetime in wireless sensor networks. MuDiLCO protocol is an extension of the DiLCO protocol introduced in chapter 4. In MuDiLCO, the protocol has implemented activity scheduling based optimization in order provides a multiple set of active sensor nodes for several rounds in the sensing phase. We have introduced an improved coverage optimization model that make a multiround optimization, whilst it was a single round optimization in DiLCO. We have conducted several sets of simulations comparing the proposed MuDiLCO protocol for different number of rounds as well as with other existing coverage methods like DESK and GAF.
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+In chapter 6, We have proposed an approach called Perimeter-based Coverage Optimization protocol (PeCO) in order to optimize the lifetime coverage, so that it provides activity scheduling which ensures sensing coverage as long as possible. PeCO protocol is distributed among sensor nodes in each subregion. The novelty of our approach lies essentially in the formulation of a new mathematical optimization model based on the perimeter coverage level to schedule sensors’ activities. The leader provides one schedule during the current period by executing the new integer program during the decision phase. The extensive simulation experiments have demonstrated that PeCO can offer longer lifetime coverage for WSNs in comparison with some other protocols.
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+Finally, we outline some interesting issues that we will consider in our perspectives which are discussed in more detail next.
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