# Smart Waste Collection System with Low Consumption LoRaWAN Nodes and Route Optimization
## 2 State of the Art
### Wireless Sensors Networks  
Wireless sensors networks have become a crucial element in the process of sensor development for smart waste systems (2015; 2016). Apart from the different transducers used to measure data, one of \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sensor Type** & **Range (cm)** & **Accuracy (mm)** & **Angle of Operation (\({}^{\circ}\))** \\ \hline Capacitive & 0–3 & 3 & 5 \\ Ultrasonic & 20–400 & 8 & 20 \\ Infrared & 10–220 & 5 & 0 \\ Radar & 30–4000 & 15 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of volumetric sensors. the main purpose of sensors is to establish a level of communication that is effective over as great of a distance as possible as well as being energy-efficient to allow the battery lives of the final nodes to be increased. These two features are greatly determined by the communication networks employed in device developments. Previous literature has presented works using traditional communication networks, such as General Packet Radio Service (GPRS) cellular networks [27; 28]. These networks are distinguished by their large deployment, which virtually guarantees their availability but presents a clear problem with battery consumption [29]. Also remarkable is the way that current Wireless Personal Area Networks (WPAN) try to adapt themselves to the requirements previously indicated, such as Bluetooth 5, which duplicates the range and reduces the consumption [30]. Previous literature has also included adapted specifications, such as the IEEE 802.11 ah specification, also called Wi-Fi HaLow [31]. These specifications theoretically reach connection ranges of up to 1 km when operating at lower frequencies, like 900 MHz. This technology is available but is not being used nowadays; this could be due to the fact that there are several competing technologies available in the market that better address the needs of large connection ranges [32]. ZigBee [33] is a very mature technology, with a range from 10 up to 100 m, but this technology can reach large distances by passing messages through a mesh network. Version ZigBee IP [34] allows the routing of different nodes through IPv6. However, ZigBee is a technology that is strongly focused on home automation instead of reaching great coverage distances. Meanwhile, new communication technologies are emerging, and they are specifically designed to establish great distance communications with low bit rates and low energy consumption. These groups of networks are known as LPWAN (Low Powered Wide Area Networks) [35]. All of them are designed to reach great distances and have really low consumption so that nodes using these networks have battery lives of years. The most important technologies in this domain are Sigfox, LoRaWAN, and Narrowband Internet of Thing (NB-IoT) [36]. Sigfox [37] is an Ultra Narrow Band (UNB) communication network [38]. It has a marketing model similar to the one of a traditional enterprise of communication where an operator provides a signal to a big area or country and gets paid for access and transfers. The operator could be the Sigfox company itself (such as in France, Germany and Spain [39]) or other companies belonging to the Sigfox Partner Network [39] (such as IoTNet [40] in Croatia or VT-IoT [41] in Ireland). Regarding LoRa [42; 43], on one hand, it is a proprietary technology based on chirp spread spectrum (CSS) radio modulation. Semtech acquired this technology in 2012, and it currently produces transceivers which use LoRa. On the other hand, LoRaWAN [44] is a media access control layer protocol, employed for managing communication between LPWAN gateways and node devices. It defines system architecture and it is maintained by the LoRa Alliance [45]. LoRaWAN uses the physical layer protocol defined by LoRa. The LoRaWAN specification is open and in contrast to Sigfox, a LoRaWAN network can be deployed free of charge for license or data transfer.