## 3 The Integrated Sensing and Communication Platform
### LoRaWAN Communication Platform: LoRa Node, GW and Server  
In the following we provide a brief outline on the overall technology and the network architecture considered in this work.  
LoRaWAN protocol is based on the LoRa transmission technology, a proprietary modulation patented by Semtech. LoRa operates in the unlicensed Sub-GHz (below 1 GHz) Industrial, Scientific and Medical (ISM) bands, with three operating frequencies: 433 MHz, 868 MHz and 915 MHz. It exploits the Chirp Spread Spectrum (CSS) modula  
Figure 5: Sensor Node supply current at 4.2V showing sensors data acquisition followed by LoRaWAN message transmission.  
Figure 6: Sensor node device final prototype.  
tion technique which allows to achieve extremely high receiver sensitivity values (up to \(-146\) dBm): in these conditions, very long transmission ranges are obtained (up to some kms in urban areas and some tens of kms in rural areas) with limited power consumption. LoRa is then the ideal candidate for a plethora of wide area IoT applications, with a large number of connected devices. LoRaWAN networks adopt a star-of-stars topology, which enables multiple GWs to receive packets from a large quantity of EDs: GWs are in charge to transfer the packets to a central network server which manages the network aspects related to security, scalability and reliability. EDs are divided in 3 Classes (Class A, Class B and Class C) which differ for their ability to receive DL packets from the GW. Class A devices are the simplest and less power hungry ones and, as such, they are by far the most common ones. However, all the three ED typologies are bi-directional in operation. Every ED must be registered with a network before performing communication. These activation processes are of two types: (a) OTAA; the most secure and recommended for EDs and (b) Activation by Personalization (ABP); less secure and requires hardcoding the device address as well as the security keys in the device. Moreover, one of the important aspects of LoRaWAN is the use of frequency plan and its duty cycle regulations. More specifically, duty cycle indicates the fraction of time a resource is busy. As an example, when a ED transmits on a channel for 3 time units every 10 time units, the device has a duty cycle of 30%. As for the transmission frequencies, they are specified in the LoRaWAN regional parameters document [24]. Note that the words frequency and channel are used interchangeably throughout the paper. The duty cycle policy is often regulated by the government and it applies to an entire sub-band. This means that if a user transmits in one of the channels of a given sub-band, it cannot use any of the frequencies of the same sub-band for a time interval regulated by the duty cycle policy. Specifically, the duty cycle values for different sub-bands are regulated by the ETSI EN300.220 standard and are reported below [25].
* g (863.0--868.0 MHz): 1% g1 (868.0--868.6 MHz): 1% g2 (868.7--869.2 MHz): 0.1% g3 (869.4--869.65 MHz): 10% g4 (869.7--870.0 MHz): 1%  
The above regulations apply to both EDs and GWs. In the followings, we briefly describe the main components of overall system.