# Worldwide Connectivity for the Internet of Things Through LoRaWAN
## 1 Introduction  
The internet of things (IoT) is a well-known paradigm, established quite a few years ago. However, only in recent times the trend regarding the wireless connectivity for the IoT has been shifting from technologies based on short-range links and mesh topologies, to long-range, star-topology-based networks. Moreover, such a long-range IoT paradigm is taking two alternative directions: one for mission-critical applications, and one for the massive IoT. Therefore, in this respect we can distinguish between two families of wireless technologies that are playing now a key role:  
1. the low-power wide-area networks (LPWANs), which will serve the needs of the massive IoT for smart metering, remote monitoring and tracking, etc. [1]. Renowned examples of LPWANs are LoRaWAN(tm) and SigFox(tm) on unlicensed spectrum, and NB-IoT on licensed spectrum;
2. the ultra-reliable low-latency communications (URLLC), serving the needs of mission-critical IoT for, e.g., smart manufacturing and autonomous driving. URLLC is mostly implemented in the context of the fifth-generation (5G) cellular network [2]. The focus of this paper is on massive IoT, and in particular on the network architecture principles of LPWAN technologies. One architectural feature that is recently gaining momentum is the support of roaming of IoT nodes between different networks. As a matter of fact, such a feature has been totally neglected before the emergence of LPWANs. Indeed, classical short-range IoT technologies like, e.g., ZigBee, Thread, 6 LowPAN [3, 4] are based on _local_ networks run by either private or publicoperators, but spanning at most the area a city (even a large one, like London). However, the possibility of running such a legacy network for massive IoT in, e.g., a nationwide deployment is very hard--if not impossible at all. As a consequence, the possibility for a smart thing to migrate from a network to the other was simply not considered, and the support of roaming was neglected in the specification and in the implementations. On the other hand, with the rise of the LPWANs, the aim is that of providing wireless connectivity for a massive number of things to areas of very different sizes, from a private network in a building to a nationwide IoT network. Therefore, the use cases for having the possibility to roam from one network to the other have actually been a distinctive characteristic of LPWANs. As a first example, let us consider an appliance exploiting a LoRaWAN\({}^{\text{TM}}\) communication node to enable preventive maintenance programs. In order for the appliance manufacturer to effectively sell its products in many countries and markets around the world having LoRaWAN\({}^{\text{TM}}\) coverage, he needs a worldwide connection plan from the local LoRaWAN\({}^{\text{TM}}\) network operator. The feature requested by the appliance vendor is technically known as a roaming plan, and cannot be provided by traditional mesh-based technologies like ZigBee, Thread and 6 LoWPAN. This is the motivation that led us to deal with features like roaming in this paper, since this matter is essential for the full exploitation of the IoT possibilities. Among the LPWANs, the focus will be specifically on LoRaWAN\({}^{\text{TM}}\) networks because of the following reasons. * As NB-IoT works on licensed frequencies, is based on subscriber identification module (SIM) and run by traditional cellular operators, it should benefit from the traditional roaming features of the mobile networks. * Sigfox\({}^{\text{TM}}\) is based on a single worldwide network, thus the roaming concept does not apply. Looking more in depth, however, one may notice that the roaming is effectively applied as a \"feature\" of the business model SigFox\({}^{\text{TM}}\) is using. As a matter of fact, such a business model resembles quite closely the one of franchising, where--for example--in Italy the company NetTrotter, which is part of the EITowers group, is the franchise of SigFox France.