tion purposes related to ultra-high node density environments, such as massive machine-type communications. 8.3 Conclusions The current needs and future evolution of IoT applications require wireless com- munication capabilities in order to enable connectivity of increasing density of devices. In this sense, compliance of coverage/capacity requirements foresees the use of sub 6 GHz frequency spectrum in order to enable large coverage areas, mainly focused in low to moderate transmission rates for telemetry and telecontrol applications. Current solutions based on LPWAN, WLAN, and 4G/5G machine-type connections will be coupled with future B5G/6G systems, for high-density line-of- sight scenarios (such as VLC), applications with very stringent QoS requirements in terms of delay and transmission bit rate, and new node/device aggregation schemes, which can benefit for fronthaul/backhaul solutions in the extended mm- wave/THz range. The combined use of these technologies, following a cooperative heterogeneous network approach, will expand overall coverage levels as well as application domains of IoT solutions. References 1. A. Zanella, N. Bui, A. Castellani, L. Vangelista, M. Zorzi, Internet of things for smart cities. IEEE Int. Things J. 1, 22-32 (2014). https://doi.org/10.1109/JIOT.2014.2306328 I. Picallo et al. 2. R. Morello, S.C. Mukhopadhyay, Z. Liu, D. Slomovitz, S.R. Samantaray, Advances on sensing technologies for smart cities and power grids: a review. IEEE Sensors J. 17, 7596-7610 (2017). https://doi.org/10.1109/JSEN.2017.2735539 3. M.A.A. Mamun, M.R. Yuce, Sensors and systems for wearable environmental monitoring toward IoT-enabled applications: a review. IEEE Sensors J. 19, 7771-7788 (2019). https:// doi.org/10.1109/JSEN.2019.2919352 4. C. Paniagua, J. Delsing, Industrial frameworks for internet of things: a survey. IEEE Syst. J. 15, 1149-1159 (2021). https://doi.org/10.1109/JSYST.2020.2993323 5. W. Ayoub, A.E. Samhat, F. Nouvel, M. Mroue, J. Prévotet, Internet of mobile things: overview of LoRaWAN, DASH7, 