# Sustainable and Reliable Information and Communication Technology for Resilient Smart Cities
## 1 Introduction
There are various aspects that enabled the sustainability and resiliency (see also Section 3) of the Internet, including the following (1) reference architectures, the (2) implementation, quality assurance and certification procedures, the corresponding (3) standardization activities and the (4) systematic approach to components, systems and networks integration and interoperability. Within smart cities, these tasks are far more challenging given the plethora of technologies including legacy technology, data models, communication protocols, components, modules, providers, vendors, use cases, stakeholders, application domains, services and users, which are involved and should be considered. The overall structure of the paper and its contributions is provided in Figure 1 with the concept inputs on the left and derived results for the smart city community and interested stakeholders on the right. The approach is to take various aspects from current theoretical smart city frameworks as an input, including blueprints for ICT reference architectures and belonging standards, various views and dimensions of the sustainability topic, theoretical foundations from the domain of dependable ICT systems, state-of-the-art and emerging technologies as well as theoretical artifacts from the area of quality assurance and testing for communication-based systems. All these inputs are combined within the paper as to provide an overall approach for a resilient and sustainable ICT-based smart city. This resilient and sustainable smart city should build on three main pillars in our view, which are depicted as the papers' theoretical output on the right side in Figure 1, namely: the design principles for developing sustainable and resilient ICT for smart cities, concrete recommendations for next steps on technological and organizational level, as well as the concept for continuous quality assurance and certification processes for the establishment of high quality and secure critical IT and data communication infrastructures within an urban environment. A key goal of this paper is to combine the reasonable features from multiple approaches to ICT reference architectures and to show how these can be used to define a sustainable and resilient ICT infrastructure within a city/community. Such a reference architecture for ICT in smart cities emerged from the activities of established standardization groups such as the DIN 91357 [2] by the German Institute for Standardization,which is based on the European Innovation Partnership (EIP) and the Memorandum of Understanding (MoU) on Sustainable Cities and Communities (SCC) [3] and its belonging ICT reference architecture work stream [4]. In this context, we also discuss the quality assurance approach oupPLUS and detail the way it can be used to provide an interoperable, secure and resilient ICT. oupPLUS is a quality-oriented extension of open urban platforms as defined in [2] and was initially presented in [5,6]). Furthermore, we outline key technological pillars which should be considered in each smart city development plan and for which oupPLUS provides the means for quality assurance, resilience and sustainability. The rest of this paper is organized as follows: Section 2 reviews various related research and development activities including long-term initiatives such as FI-WARE (FI-WARE stands for Future Internet-ware) or European projects such as Triangulum and Espresso. Section 3 provides the basic definitions of sustainability, smart cities and sustainable smart cities, thereby setting a frame around the discussions and elucidations of the current paper. Section 4 presents the concept of reliable ICT and motivates it through some historical definitions. Section 5 sets the ICT frame for further discussions by presenting the concept of ICT reference architectures and open urban platforms, which is the natural setting for the development of a smart city and enhancing its reliability.