# Sensor-Based Solid Waste Handling Systems: A Survey
## 5 IoT-Enabled Solid Waste Management Systems
### Network Architecture  
A generic IoT architecture for solid waste handling system is shown in Figure 6. The architecture comprises four sections namely IoT end device, gateways or base station, cloud server, and end-user. * IoT end device: It consists of sensors to measure the unfilled level or weight of the trash bins, a microcontroller to perform local processing, and a radio device to establish wireless connectivity with gateways or base stations. * Gateway or Base stations: Several communication technologies are available to establish connectivity between the end devices and the cloud server. According to the adopted wireless technology, the gateway or base station will act as a bridge between the end devices and the cloud server. For instance, a gateway for LoRaWAN devices, a base station for Sigfox and NB IoT devices, and a wireless router for Wi-Fi devices. * Cloud Server: For IoT applications, cloud servers are preferred due to their flexibility, scalability, and secure authentication process. * End-user: Remotely monitoring a system can be performed by the end-user. The end-user may be an employee of the solid waste management company or a person in charge of the solid waste collection department in a municipality or corporation. A hierarchical view of trash bins' filled level can be obtained through a web page or application software. Furthermore, automated route optimization for waste pickup trucks is another part of waste management operations. To collect trash, these trucks usually follow a certain path every day. Drivers are often unaware of how full a trash bin is filled until they come across it. IoT solutions in waste management are helping to improve this situation by providing truck drivers with real-time information of the actual fill level of trash bins. IoT Embedded Trash Bin Level Monitoring Systems  
IoT-embedded trash bin level monitoring systems are the latest approach towards building smart cities. A wide range of IoT-based systems, starting from general trash bin monitoring to waste sorting and recycling is available in the literature. This section provides a comparative analysis of various IoT-embedded trash bin level monitoring systems. Table 4 shows the summary of IoT-based solid waste handling systems. An approach for the optimized handling of solid wastes in urban areas is proposed in [41]. A combination of proximity and weight sensors is incorporated to obtain the status of trash bins (i.e., weight/filled level). A Raspberry Pi microcomputer is acting as the gateway to transmit the measured data to the smart-M3 platform. However, this system requires additional gateways to increase its wireless range. Cloud-based smart waste management for waste collection and recycling is proposed in [42]. This system consists of separate trash bins for different types of wastes such as organic, plastic, bottles, etc. However, the study has not specified the details of the sensors and wireless technology adopted for deployment. In [43], the author describes various waste disposal methods in which IoT-based systems can be implemented. A smart box that is powered with solar energy is proposed in this system for bin level measurement. However, this work fails to present the architecture in detail. A system for screening and sorting plastic resin is proposed in [44]. After removing plastic wastes, the remaining wastes are used for biogas plants. In [45], the author describes a smart bin system that uses a mesh network to monitor