This project investigates effective and resource efficient establishment of connectivity among disjoint wireless sensor network (WSN) segments. The segments can belong to a structurally damaged network caused by the failure of multiple sensor nodes. In addition, the segments can simply be standalone WSNs that are normally operated by different agencies and are to be federated to serve a common application. The objectives of this project are to develop novel solutions for various aspects and contexts of the federation problems, to create a prototype for validation and to share the results/experience with application designers.
The technical approaches consider the availability of resources such as mobile sensors, mobile and static gateways and their count. Both optimal and heuristic solutions for repositioning of mobile sensors and placement of mobile gateways are studied to establish connectivity as well as achieving some desired performance (i.e., QoS). Finally, the results are validated via a real test-bed consisting of sensors and mobile robots. This project will boost the effectiveness of many civil and scientific applications. Example of such applications include crisis management, where existing WSNs may suffer an extensive loss of nodes due to fire, flooding, debris, etc., or when the services of networks owned or controlled by different parties or agencies need to be aggregated to assess in search-and-rescue. The results are made available in various forms including archival publications, tutorials and web-based resources. The project is enriching the curricula at UMBC and SIUC through hands-on projects and attracting K-12 students via prototype demonstrations.
The project investigated various novel techniques for restoring the connectivity of disjoint wireless sensor networks that are partitioned due to the failure/damage of one or more sensor nodes. The following are the outcomes of the project: - Novel self-organizing solutions have been designed and implemented for the connectivity restoration problem in disjoint wireless sensor networks. The major novelties in these approaches were the ability to self-recognize the partitioning and then the ability to orchestrate coordinated recovery approaches that will guarantee the network restoration and thus the network operation. - One of the main outcomes of the project is that Game Theory has been identified as a strong solution for dealing with uncertainties when a completely distributed self-recovery approach is to be designed. Due to lack of information about the node failures, their locations and scope of the failures, utilizing Game-theory helps making the right decisions even though the information is missing or vague. - The project introduced a new inexpensive and easy-to-build mobile sensing platform using the off-the-shelf devices such as iRobots. These robots were integrated with IRIS motes in order to build a mobile node that can be part of a mobile sensor network. Using this new platform, called iRobotSense, a testbed was built to test some of the existing connectivity restoration approaches. The iRobotSense mobile node and the testbed have provided realistic guidelines for the researchers working on mobile sensor networks. - The project also investigated the possibility of providing intermittent connectivity when there are not enough relay nodes to restore connectivity in a disjoint wireless sensor network. The approaches developed in this project were one of the first to suggest using mobility to provide intermittent connectivity by touring the partitions of the network. Several novel solutions were developed to meet various goals in terms of delay, tour length and coverage. - One of the unique outcomes of the project is the inclusion of mobile node navigation issues in the research challenges dealt at the network level. Due to high dependance on the mobility of the sensors, this project incorporated realistic navigation mechanisms from robotics by considering the terrain conditions and localization errors. The outcome of such inclusion is that most of the existing protocols that rely on mobile node movement may need revisions for realistic results. - The self-organizing approaches developed in this project will be instrumental in a lot of real-life applications where mobile sensing nodes can be deployed for different purposes. Urban search and rescue, habitat monitoring, and disaster management approaches can benefit from these approaches by deploying a number of mobile nodes that can be used during network damages due to fire, wind or flooding. - The idea of using mobile nodes as data collectors to ensure connectivity can be applied to many applications when there is not enough assets to be deployed due to high costs or when the intervention is not possible due to lack of personnel or inaccessibility of the region. This approach can provide a temporary solution to data collection (e.g., during a disaster) until a permanent solution can be provided. - The project made a significant impact in Southern Illinois region. It provided opportunities for the first generation college students and a lot of high school students to get engaged with sensor network technology and attract them to careers in engineering and computer science. The hands-on experience the project provided for the graduate and undergraduate students was very rewarding given the limited resources at the university and in the region which is mostly rural. - The project provided several outcomes in terms of products and publications. Several quality papers, simulation software, reports, presentations, theses and a dissertation were produced during the entire life of the project.
