Vision towards 5G: Comparison of radio propagation models for licensed and unlicensed indoor femtocell sensor networks

Sensors and sensor networks are the future of fully automated industry solutions. With more capability and complex machinery, the requirements for sensing in larger factories are critical, considering the data amount, latency, and the number of sensors in operation. Given the excellent time-critical operation, bandwidth and the number of devices connected, the 5G indoor femtocells could prove an excellent option for building industrial sensor grids. For more flexibility in control and reliability, operating the 5G indoor femtocell network in license-free frequency bands could be an alternative to commercial 5G services. The 5G networks incorporate a very dense network of indoor femtocells. The Femtocells also enhance data rates, indoor performance, and coverage area both in residential and industrial environments. Therefore, keeping in view the above-stated actualities, this paper addresses different indoor scenarios for radio wave propagation and simulates several path loss models to calculate the likely and most suitable propagation model for indoor signaling. Multiple models for frequencies in the unlicensed band below 6 GHz and above 6 GHz (licensed) 5G femtocells are discussed in the paper considering the constraints of material types, attenuation due to obstacles, various floors, carrier frequency, and distance from the transmitter. The comparative analysis indicates that the ITU model and Keenan–Motley model give the highest path loss in residential and industrial environments, respectively, while the log-distance model has the lowest path loss in both environments for below 6 GHz frequencies in the unlicensed spectrum. For the above 6 GHz licensed bands, the Alpha Beta Gamma (ABG) model and Path Loss Exponent (CIF) model are observed to have the minimum path loss difference