# A Low Power IoT Sensor Node Architecture for Waste Management Within Smart Cities Context
## 2 Smart Cities and Waste Management  
Many papers describe the strict correlation between Smart Cities and WSN focusing on how this technological framework can be exploited to develop interconnected intelligent systems. Moreover, if the data gathered by the network are made available on the Internet, then the IoT framework (which, nowadays, is a hot-topic) is encountered. For instance, in [1] such relation is highlighted. The authors report a list of applications encompassed by the concept of Smart City: structural health of buildings, air quality, noise monitoring, traffic congestion, city energy consumption, smart parking, automation and saluburity of public buildings, smart lighting and finally waste management. Then, they present how these services are performed within the whole picture of the Padova Smart City project whose aim is to develop an IoT island in the city of Padua, Italy. Within the context of air quality and pollution monitoring [2] gives an interesting overview of the problem and how to solve it by means of a wireless sensor node that is part of an IoT system. The authors propose an interesting energy-saving policy which controls the duty-cycle of the whole sensor node. This technique and the one shown in Section 5.1 are developed in a pretty similar fashion. However, it relies on a rechargeable battery via a photovoltaic cell and, as it will be described in Section 4, renewable sources of energy cannot be exploited in the proposed scenario. Reference [3] proposes an IoT infrastructure for Smart City and examines the case of study of the noise monitoring, while [4] shows a solution for long term structural health monitoring of buildings reporting the case of study of a church sited in L'Aquila, Italy, which is a city recently struck by an earthquake. There exist several useful services that can be implemented in Smart Cities by using WSN-based monitoring systems. They span throughout many application fields, such as environment, health, industry and home automation. Moreover, in recent years, many enabling technologies (like GPRS, RFID, GPS, WiFi) have been investigated in order to solve issues related to the various phases of solid waste generation, monitoring and management: these matters are often critical in terms of both operating costs and environmental quality. This paper deals with a WSN solution to face the solid waste monitoring by using an innovative IoT node architecture so as to monitor the filling of garbage bins. In particular, this case scenario is only a possible test-bed since the optimized implemented solution allows a node to reduce power consumption, therefore it may be applied to many other working fields. In the literature, several papers [5; 6; 7; 8; 9; 10; 11] propose solutions using WSN for waste management. Some researchers proposed a WSN and a web browser [5] for monitoring the bin status: this is a crucial parameter in this application field since if a bin is partially filled then it does not need any depletion. As a consequence, human intervention would be limited causing a reduction of the cost involved by solid waste collection. The authors opted for multiple communication technologies within the WSN. One of these is the GSM/GPRS, therefore such a paradigm requires high running costs. Moreover, they did not account for any energy-saving policy claiming that it should be a future works target. Solution [6] was developed by implementing Vehicular ad hoc networks (VANETs), providing a model in which the garbage collection is monitored in real time: each trash bin is equipped with a sensor node that continuously senses its status and when it is full it sends a signal to the nearest garbage collecting vehicle (hence, each of them is a WSN node as well). Then the vehicle will collect the garbage and will move back. In so doing, garbage collection from bins is made dynamically and it results a much more efficient solution in comparison with the traditional bins emptying based on planned collections.