# Smart City Pilot Projects Using LoRa and IEEE802.15.4 Technologies
## 4 Smart Lighting Testbed  
In the framework of the PEGASUS project, funded by the Italian Ministry for Economic Development, WiLAB realized an experimental testbed at the premises of Fondazione Alma Mater (University of Bologna), where a network of smart, remotely controlled street lamps was deployed, which was also capable of supporting the provision of smart services. The main objective was twofold. First, the poles wireless network was meant to increase the efficiency of the lighting infrastructure itself, reducing electricity consumption via a combination of dimmers and task lighting (Figure 1a). Second, it was meant as an access network for the provision of context services, such as smart parking (Figure 1b). More precisely, eight LED street lamps located in the park of the historic building Villa Gandolfi Pallavicini (Bologna), shown in Figure 2, were equipped with IEEE 802.15.4 short-range communication interfaces, on top of which the proprietary routing protocol implemented at the University of Bologna and allowing to create a mesh topology, was implemented. One of the poles (hosting the coordinator) was also capable of long-range communications, through a cellular interface, which allowed the connection of the whole pole PAN with a remote control center. All the poles were thus completely managed by the control center with no need for a fixed communication infrastructure, allowing the remote dimming of each light fixture independently of the others, as well as the monitoring of their operating conditions through individual telemetering (e.g., power consumption and temperature) and telediagnostic. The deep expertise gained from the deployment and management of such testbed led to a large-scale implementation of the smart lighting technology in the Italian municipality of Montechiarugolo. Here, the whole public lighting infrastructure, around 3000 luminaries in a 211 square kilometres area, was enhanced accommodating LED lamps and the devices needed for establishing wireless communications and the provision of smart services. This infrastructure is  
Figure 1: Examples of smart services enabled by intelligent street lamps. Figure 2: Smart city testbed at Fondazione Alma Mater (2012). fully operational since 2014, when the replacement of the previous fixtures (mainly working with sodium-vapor lamps) was completed. All poles of the new infrastructure are equipped with the circuitry for the dynamic light dimming and with IEEE 802.15.4 communication interfaces (for the mesh network establishment), having a transmission power of 20 dBm and a transmission rate of 250 kbit/s. Exchanged packets have a maximum payload length of 64 bytes. From a hierarchical point of view, the network is organized in clusters (i.e., PANs) of 100\(\sim\)150 light poles (depending on propagation conditions), each one managed by a coordinator. The number of hops between the coordinator and the cluster peripheral goes from 5 to 10 (depending on the cluster topology), which determines in the worst case a latency from the control center to the network border of 100 ms, more than adequate for smart lighting applications. Moreover, in order to minimize inter-cluster interference, different channels were chosen for adjacent clusters. Figure 3 shows an exemplification (with only three clusters and 30 nodes) of the network architecture. In perspective, all poles are also ready to host additional sensors, in order to allow, for instance, environmental monitoring or motion detection for context-aware light dimming. Thanks to the wireless network, the light intensity of each street lamp can be remotely controlled with no need of a fixed communication infrastructure. Moreover, the switching and dimming of street lights can be remotely programmed and re-programmed as per requirement so as to save valuable power. Lamp diagnostic, real-time fault detection and energy consumption controllers are implemented as well, providing city managers with all the information required for an efficient service provision.