Smart cities aim to improve the quality  of life of citizens as well as providing asustainable environment. Since communication between the various components of a smart city is necessary for its operation, a tool on which these cities have been built is the Internet of Things (IoT). Despite the interest in expanding and improving solutions for smart cities and IoT, observed by the investment and by the increasing  deployment of globally connected devices, recent studies have shown that these devices do not receive the proper attention when it comes to Information Security. In addition, opportunities for improvement have been observed in communication between nodes of IoT considering the next generation of mobile telecommunication (5G) and in transport layer protocols that are optimized to devices with limited power resources. In that sense, this project presents four research lines related to improvements in various layers of the Internet of Things to create a safe, effective and efficient environment for future applications: Secure software architecture for the Internet of Things; Analysis of big data to detect threats to information security in smart cities; Performance evaluation of new transport layer protocols in the Internet of Things; and Optical Architectures for 5G Internet Support.