# A Low Power IoT Sensor Node Architecture for Waste Management Within Smart Cities Context
## 2 Smart Cities and Waste Management
A drawback of this solution is that two LASER diodes, which in turn act as transmitter and receiver, are exploited for sensing the filling level of trash bins. As it will be explained in Section 4.2 it could be an unreliable method. Beside this, the authors did not adopt any energy-saving policy at all. Moreover, in [7] efficient routing algorithms are advised as well as real-time waste related information. In particular, the filling level of bins can be sent to a monitoring and Decision Support System (DSS) owing the storage of historical data that can be exploited to predict waste bins filling rates. In the IoT applications, many designers and developers opted for microcontroller boards (for example Arduino boards) or Systems on Chip (SoC, such as Raspberry Pi, BeagleBone, Lopy) as platforms to provide sensor nodes with Internet connection: this choice is often very complex, due to the fact that a trade-off between costs, performances and functionalities is needed for each particular application project. Many enabling technologies are used to setup smart platforms, which are capable of collecting and managing data, that deal with problems related to waste management. Some examples are: environment pollution due to overflowed trash bins that causes human diseases, increasing number of insects and mosquitoes. Emerging technologies and innovative devices are used to optimize these solutions, even though ZigBee and GSM technologies are still a valid choice, especially if combined with microcontrollers or SoCs. Some IoT smart waste management systems combine the strengths of WSN with the high performances of SoCs [8]: the embedded board acts as a node in a WSN based on the ZigBee protocol and consisting of a coordinator and sensor nodes distributed in the test area. The coordinator collects data from sensor nodes and then sends it to the communication board, that stores collected data in a database, analyzes it and provides a user interface to monitor them. Each of the trash bins is equipped with an Arduino UNO board. This directly implies an increase of both costs and consumption. In addition, the authors choose a network architecture that relies on a coordinator node for which a Raspberry Pi board is exploited involving higher costs and consumption as well. Smart garbage bins [9] allow authorized people to acquire information concerning the filling level, through ultrasonic sensors placed on the bins and by using a GSM-equipped microcontroller that sends data to a control station. A similar study [10] shows how it is possible to acquire useful data (garbage level, wet garbage and toxic gases detection) from a set of sensors (ultrasonic, moisture and gas sensors) installed within the bins and connected to a microcontroller which sends data covering a long distance through a ZigBee transmitter, also sending SMS to mobile devices by using a GSM module. Once again, these two last solutions do not suit well to the context of this paper since GSM entails pretty high running costs. Reference [11] shows a sensor node for monitoring the filling level of waste bins equipped with RFID technology, that could be a viable solution due to its robustness and cheapness. Unfortunately though, it cannot provide a communication range as large as the one ensured by Low Power Wide Area Network (LPWAN) technologies (as described in Section 4.1). A recent study [12] proposes how to implement a smart garbage management IoT system combining sensors and Raspberry Pi, while a well-performed survey [13] about smart garbage management in cities using IoT suggests many other ideas that may be implemented.