Wireless sensor network coverage problem

Abstract

The title of this project is called "Wireless Sensor Network Coverage Problem". The objective of the coverage problem is to use some wireless sensors to fully cover a target area. In this project, we focus on the problem when the target area is a line. Therefore, the problem can also be referred as "Barrier Coverage Problem". This problem has some significant applications in the real world such as highway monitoring, seaway monitoring and border surveillance, etc. The aims of the project include finding some efficient algorithms, analysing these algorithms and developing a system for naive users to find the optimal solutions of the problem by themselves. We analyse each algorithm from the following aspects: the approximation ratio, the time complexity of the algorithm and the performance in experiments. In this project, we study the objective of minimizing the total cost of a range assignment that can fully cover the line interval. We can further divide the problem into two sub-problems. One sub-problem is called "On-the-line Barrier Coverage Problem" ("On-the-line"), which has been well researched by researchers. The other sub-problem is called "Off-the-line Barrier Coverage Problem"("Off-the-line"), which very few researchers are working on. Moreover, the "Off-the-line" problem can be considered as a generally case of the "On-the-line" problem. Because the "On-the-line" problem has been well researched and we think not many extensions can be made further, we spend most of our time on studying the "Off-the-line" problem and try to make some extensions on the "On-the-line" problem based on some previous works. In the first several months of the project, we find an approximation algorithm to solve the "Off-the-line" problem and it can achieve an approximation ratio of 1:5. Later, we improve the algorithm so that it can achieve a better approximation ratio of 4/3 . Then we try to apply this algorithm to the "On-the-line" problem and find that it can achieve an approximation ratio of 5/4 , which is the best approximation ratio for the "On-the-line" problem as far as we know. Besides looking for constant-approximation algorithms, we also try to use some other techniques to solve the problem. Later in this report, we will show that this problem can be solved by dynamic programming and finding the shortest path under some situations. Some other related extensions have been made in addition for both the "On-the-line" problem and the "Off-the-line" problem. We have turned our work into two papers, "Barrier Coverage by Sensors with Adjustable Ranges" and "Barrier Coverage Using Sensors with Off-sets". The first paper has been accepted by an international journal called "ACM Transactions on Sensor Networks" and the second one is accepted by an international conference called "The International Conference on Wireless Algorithms, Systems and Applications"("WASA"). In addition to these achievements in the theoretical side, we have developed a system on the problem as well. The system is written in Python. Users can find the optimal range assignment for both the "On-the-line" problem and the "Off-the-line" problem by using our system. Our system can get users' inputs either through keyboard or an external file. The system is robust, user-friendly and easy to use. Overall speaking, we have achieved most of the aims we have made before the project. Furthermore, we have done quite well on the time management. Considerable progress has been made every month during the whole year.