# Next Generation Wireless Technologies for Internet of Things
###### Abstract  
In the fast-growing Internet of Things (IoT), applications from personal devices to industrial instruments and sensors connect wirelessly to the Internet. Considering that a broad diversity of use cases in different environments with specific requirements can be developed, it is clear that no single wireless standard can abundantly predominate. With many standards available on the market, spread over various frequency bands and employing diverse communication protocols, the choice of the best wireless connectivity technology for an IoT application can be quite challenging. The first issues to be evaluated are the frequency bands and global regulations. In fact, in most regions, the available spectrum assignment is subdued to a licensing scheme, which implies that users have to obtain a license from the local regulator to transmit signals in a selected frequency channel. On the contrary, several frequency bands have been designated for Industrial, Scientific, and Medical (ISM) applications. These bands are unlicensed and differ slightly from country to country. In recent years, the popular ISM bands have involved 433 MHz, 868 MHz, 915 MHz, 2.4 GHz, and 5 GHz. Nevertheless, as a standard rule, it is well-known that higher-frequency bands offer a broader bandwidth and hence make broader bandwidth and more channels available. As a consequence, they can serve more extended networks and handle a higher data throughput. Contrariwise, lower-frequency radio waves propagate better than higher-frequency ones and can thus achieve a longer range, especially inside buildings. Another characteristic to be analyzed is the communication protocol. In fact, for several years, numerous protocols have been developed following a layered network implementation. This choice, on the one hand, includes complexity and needs more code and memory. Furthermore, it also implies data overhead because each layer expects further framing and control messages. Nonetheless, on the other hand, layered networks facilitate more flexibility and scale. For instance, it is useful to note that a simple network scheme, with no or limited layering, is represented by a proprietary application protocol, operating directly over the physical layer equipped with a simple radio transceiver. It is clear that this type of solution can be pretty efficient, but it can be used only in simple, single-function networks. The network range is undoubtedly another feature to take into account. A network's range is commonly categorized in 4 categories: Personal Area Networks (PANs), Local Area Networks (LANs), Neighborhood Area Networks (NANs), and Wide Area Networks (WANs). PANs usually are wireless and cover a range of about 10 m. A direct consequence of these features is that wireless PAN devices typically have low radio transmission power and operate on tiny batteries. On the contrary, LANs can be wired or wireless and a combination of the two technologies is also possible. It is useful to note thatwireless LANs (WLANs) ordinarily cover a range up to 100 m. In most cases, NANs are wireless and can reach more than 25 km. In this case, they transmit with high power levels but usually carry low data traffic. Lastly, WANs are disseminated across an extensive area. As it is known, the Internet is considered a WAN and involves a heterogeneous mix of wired and wireless connections. The way in which wireless nodes in a network are organized and how they connect to each other, i.e., the topology, is another peculiarity to evaluate. The typical network topologies are star and mesh. In a star-based network, all nodes are connected to a central one, which typically serve as the gateway to a wider network. On the contrary, in a mesh network, every node can connect to various other ones. In this case, one or more nodes can work as a gateway. The main advantage of a mesh network is that it can increase the range through many hops while keeping a low radio transmission power.