This study presents a comprehensive analysis of network-level performance and the practical implementation of a smart city Internet of Things (IoT) system using an Infrastructure as a Service (IaaS) cloud computing architecture. The performance of the smart city IoT network topology is evaluated through simulation using the NS3 simulator, focusing on crucial performance-affecting parameters. The improved performance smart city topology is then put into practice within the IaaS architecture. The envisioned smart city IoT system is designed to monitor key parameters such as video surveillance employing thermal cameras (for detecting individuals with COVID-19-like symptoms), transportation, water quality, solar radiation, noise pollution, air quality (including O3, NO2, CO, and particulate matter), parking availability, significant landmarks, electronic suggestions, and public relations information. This monitoring is achieved over a wide area network with low power requirements, covering an area of 61.88 km x 61.88 km.Primary attention is given to addressing challenges related to IoT network-level routing, quality of service (QoS), and implementation-level security. A network topology analysis is conducted at the simulation level to enhance routing and QoS. To enhance security, a decentralized approach based on blockchain technology is adopted, aiming to bolster the overall performance of the IoT system. Keywords: IoT technology ,Smart applications ,Network simulation , Blockchain technology