name: Ihor Rusnak Research Topic: Optimization Problems in Wired and Wireless Sensor Networks

student name: Ihor Rusnak Research Topic: Optimization Problems in Wired and Wireless Sensor Networks Abstract: Wireless sensor networks (WSNs) are widely used today for many purposes, such as weather forecasting, environmental monitoring, seismic monitoring, target and hazard detection, fire and flood detection, and military surveillance. Therefore, efficient network data collection is highly valued. Using a tree as a routing structure can be quite effective for data collection. Furthermore, data collection in WSNs is efficient when a fixed amount of data can be aggregated into a single packet. Specifically, data aggregation helps reduce the number of transmissions and conserve sensor battery power. The collected data is periodically generated by sensors and transmitted to a specific node, called a sink. Since the sink is often located far from the sensors, multi-hop transmissions are used. In many WSN applications, time-critical transmission of collected data is required, but collisions may occur between messages transmitted simultaneously. Therefore, message scheduling through the network is required to minimize the time it takes for a message to reach the sink and avoid collisions. Network functions virtualization (NFV) is also a very important trend. It allows organizations to reduce costs and optimize service deployment. With virtualization, network functions that were previously executed on specialized hardware are replaced with software called virtual network functions (VNFs), which can be run on standard hardware. This allows network functions to be applied to data flows passing through network nodes hosting VNFs. These network nodes are called VNF nodes. To fully realize the benefits of network functions virtualization, each flow must be fully processed on these VNF nodes. Typically, due to budget constraints, only a limited number of nodes can be selected to host VNFs. Furthermore, each node typically has limited capacity, which must be used to process the multiple flows passing through it. Given these constraints, it is necessary to select a subset of nodes to host VNFs and determine a capacity allocation that maximizes the volume of traffic passing through them. In my research, I considered several problems using a tree-based data routing structure and data aggregation: minimum-cost data collection tree aggregation (MCDCTA), the problem of minimizing the latency of collision-free data aggregation in WSNs, where a fixed amount of data can be aggregated into a single packet, given the presence of multiple sinks in the network (MLCAMDAS-MultiSink), and a problem in the field of network function virtualization—the joint VNF placement and in-band power allocation problem (VPCA-ILP). To solve each of these complex problems, I have developed approximation algorithms and provided a theoretical analysis, determining their approximation coefficient and complexity. For one of the problems, the obtained results have been validated by extensive simulation results.