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The world is entering a new era, where Internet-of-Things (IoT), smart homes, and smart cities will play an important role in meeting the so-called big challenges. In the near future, it is foreseen that the majority of the world’s population will live their lives in smart homes and in smart cities. To deal with these challenges, to support a sustainable urban development, and to improve the quality of life for citizens, a multi-disciplinary approach is needed. It seems evident, however, that a new, advanced Information and Communications Technology ICT infrastructure is a key feature to realize the “smart” vision. This paper proposes a specific solution in the form of a hierarchical layered ICT based infrastructure that handles ICT issues related to the “big challenges” and seamlessly integrates IoT, smart homes, and smart city structures into one coherent unit. To exemplify benefits of this infrastructure, a complex IoT system has been deployed, simulated and elaborated. This simulation deals with wastewater energy harvesting from smart buildings located in a smart city context. From the simulations, it has been found that the proposed infrastructure is able to harvest between 50% and 75% of the wastewater energy in a smart residential building. By letting the smart city infrastructure coordinate and control the harvest time and duration, it is possible to achieve considerable energy savings in the smart homes, and it is possible to reduce the peak-load for district heating plants.

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Providing last-mile Internet access to rural areas in Africa is a very challenging task, i.e. many more or less successful attempts have been made over the years. One solution that seems to offer a sustainable business case is based on WiFi base stations with access points placed in the centers of the villages. Nevertheless, this solution has a limited range, especially inside the homes where the wall attenuation dominates. This paper provides a solution in the form of deploying a cheap, simple, and powerless passive repeater on the shielding walls. By simulating the WiFi radio-link between a base station and a user positioned inside a home, it has been found that the passive repeater lowers the wall attenuation considerably and thereby extends the usable range.