# Design, Deployment and Evolution of Heterogeneous Smart Public Lighting Systems
## 5 Network Architectures and Transmission Technologies
### Wireless Networks
#### 5.2.2 Non-Cellular LPWANs  
Non-cellular LPWANs are increasingly adopted for smart lighting applications, as they allow to reduce the operational costs of streetlights networking with respect to cellular networks. Long Range (LoRa) and Sigfox are, in particular, the LPWAN technologies mostly considered in smart lighting scenarios, thus deserving specific discussions. **LoRa wide area network (LoRaWAN)**: LoRaWAN [88] is a point-to-multipoint networking protocol for WAN communications that uses the LoRa proprietary modulation scheme owned by chip manufacturer Semtech. More specifically, LoRaWAN is an open-standard that defines the medium access control (MAC) layer for LPWANs based on the LoRa chip, which transmit over license-free bands (169 MHz, 433 MHz, 868 MHz and 915 MHz) with a very long transmission range (more than 10 km in rural areas) and low power consumption [89; 90; 91; 92]. It supports bit rates ranging from 250 bps to 21.9 kbps. It was designed to connect battery-powered, low bit rate, IoT devices across a wide coverage area. Regarding network aspects, LoRaWANs are generally laid out according to a star topology and the central node is usually called gateway. In urban scenarios, more than one gateway might be installed to increase the coverage, so that several star networks might be deployed to cover the whole service area. The typical communication infrastructure adopted in smart lighting scenarios is shown in Figure 3, where two star networks providing connectivity to groups of light fixtures are depicted. Each gateway, acting as a hub, is then connected to the Control Center by means of the widespread cellular network or another IP-based communication technology. As can be observed, the resulting network is very similar, from an architectural point of view, to a cellular network. In fact, the LoRa gateways spread across the city play exactly the same role of the cellular BSs. The main difference is that LoRa networks are private ones, so that the holder of the smart lighting infrastructure is also the owner of this fundamental asset. In any case, if the cellular network is adopted to connect the LoRa gateways to the Control Center a fee is to be paid, which is however scarcely significant owing to the low number of gateways. **Sigfox**: Sigfox is an LPWAN network operator that offers end-to-end low bit-rate IoT connectivity based on its patented technology. Its proprietary BSs are deployed in the service area by Sigfox partners and are connected to the back-end servers through an IP-based network. They provide wireless connectivity to end devices in unlicensed ISM bands (868 MHz in Europe, 915 MHz in North America, and 433 MHz in Asia). By employing ultra-narrow band (100 Hz) signals, Sigfox communications experience very low noise levels, thus achieving large coverage distances (up to 10-40 km in rural zones and 1-5 km in urban zones) at the expense of maximum throughput of only 100 bps [93]. Sigfox supports limited bidirectional communications: downlink communications can only occur following an uplink communication. The number of uplink messages is limited to 140 per day, with maximum payload of 12 bytes for each message, whereas the number of downlink messages is limited to 4 messages per day, with maximum payload of 8 bytes [94]. As far as the network topology is concerned, Sigfox adopts the same architecture previously described for LoRa. Also in this case, an adequate number of hubs, usually called Sigfox stations, are deployed in the services area, each of them establishing a star network (as shown in Figure 3). However, differently from LoRaWAN, Sigfox networks are owned by Sigfox itself, hence, end users have to pay for the connectivity. In the case of smart lighting scenarios, this entails that a fee is to be paid for thousands of streetlights. Both LoRa and Sigfox technologies are currently adopted by several light fixture manufacturers.