# Next Generation Wireless Technologies for Internet of Things
## 2 A Review of the Contributions in This Special Issue  
In the last years, various research efforts have been carried out to merge the IoT with smart city environments. The goal to shape a city \"smart\" is rising as a potential solution to decrease the issues caused by the urban population growth and fast urbanization. Information and Communications Technologies (ICT) can unquestionably be an outstanding assistance in developing smart cities. In fact, some papers published in the special issue focused on these research fields. The authors of [1] present a novel solution able to sustain the development and dynamic deployment of infrastructure-less wireless applications in sparse smart city environments. The solution introduced by the authors enables the dynamic control of mobile nodes by creating new single-hop links and dispatching packets at multi-hop distance. Moreover, it also lets software components on mobile nodes to be deployed and upgraded on-the-fly. The results obtained through a working implementation of the proposed middleware are promising to the point that the authors, in their future works, will focus on on the containerization of the proposed solution as well as of specific sensor/controller components. A novel methodology to distinguish the electromagnetic field induced by wireless networks is presented in [2]. The authors exploit the functionalities of a smart city platform to use some low-complexity probes. The analysis of the information gathered during a whole year validates the proposed technique regarding the characterization of large areas, close-by dosimeters, and the exposure induced by the different wireless communication technologies. In the scenario of Vehicular Ad-Hoc Networks (VANETs), the authors of [3] present an underlay Radio Resource Management approach that can enhance cellular spectral capability, with a minimum influence on cellular communications,and, at the same time, guarantees the different Quality of Service (QoS) requirements of Intelligent Transportation Systems (ITS) applications. Simulations results, highlight the benefits of the spectral efficiency provided by the presented approach. Moreover, the improvement of energy efficiency is the goal of the authors in their future works. Other authors have concentrated their research works on proposing specific improvements concerning the protocol structure or hardware components. For instance, the potential of the Sub-GHz wireless communications for future IoT wearable applications is examined in [4]. The authors focus on the antenna gain limitation and, for this reason, several tests are conducted to compare two bands. Results highlight that the 915 MHz band offers a comparable link budget when compared to the 2.45 GHz one. Further evaluation is carried out among different wireless protocols and radio transceivers, and the results reveal that average current consumption is an active function of sleep current and sampling rate. The authors also present an antenna design developed to work both in free-space and on-human wrist scenarios. An authentication and key management mechanism for the establishment of a security association between a resource-constrained IoT device and an access point is introduced in [5]. The proposed mechanism can reduce the number of cryptographic processes needed on the IoT device by transferring the mutual authentication and the key derivation functions processes of the device to the station-side authentication server. Results show that the mechanism presented by the authors decreases almost all the computational costs, the cryptographic functions can be replaced with new ones without affecting the resource-constrained devices, and a better scalability of the access point even with a large number of stations can be achieved.