Sustainability is gaining significance for the development of smart cities and society; hence why intelligent and holistic Internet of Things (IoT) is promising and practical. Smart cities and society have numerous amounts of IoT devices (e.g., sensors, meters, cameras, actuators), from different industrial sectors and public utility companies deployed, and connected by widely paved network infrastructure.

In recent years, we have witnessed IoT solutions designed and optimised with considerable efforts to achieve spectrum, energy, and cost efficiency for individual applications. However, overlapping geographical and functional domains of IoT services in smart cities and society make traditional IoT solutions face problems in vast energy consumption, and in duplicated investment. Therefore, IoT solutions for smart cities and society should be developed comprehensively in an integrated way, which is referred to as the holistic approach. The holistic approach emphasises that practical systems and their properties must be viewed as a whole for decision making, not just as a collection of well-optimised parts. In terms of modern IoT, the holistic approach can be used in two different ways. Firstly, through IoT, information from different sectors can be safely gathered, delivered, and processed for holistic decisions. Alternatively, assisted with novel powerful artificial intelligence, IoT can form a closed-loop ecosystem for self-driving perception, analysing, optimising, and decision-making. The heterogeneous nature of implementations demands effective IoT deployments, which can ensure proper interoperability and reliability at the network level. In the meanwhile, facing the need for cross-sector data sharing, manufacturers, operators, and data-providers will have to work together to secure the connected user devices and data. Multidisciplinary approaches should be encouraged for more applications of the holistic approach in non-linearity within mathematical models. Deep reinforcement learning and other computational intelligence approximations are recently prevailing in the non-linear domain, however practical solutions with reasonable complexity are yet to be improved.

The aim of this Special Issue is to collate original research articles and review articles about intelligent and holistic IoT solutions for sustainable cities and society. We hope that this Special Issue will inspire new thoughts and contributions to this specific topic.

Potential topics include but are not limited to the following:

• Fifth-generation (5G) and sixth-generation (6G) sustainable, and massive IoT for smart cities
• Deep learning-based holistic solutions for modern society
• Hybrid cloud/edge architecture for future IoT applications
• Data driven IoT solutions for smart city IoT
• Efficient data delivery in holistic IoT networks
• Sustainable big data analytics for massive IoT
• Fast and reliable artificial intelligence (AI) algorithms for practical IoT system
• Data security for intelligent and holistic IoT applications