Measurement-Based Path Loss and Delay Spread Propagation Models in VHF/UHF Bands for IoT Communications

Abstract

Internet of Things (IoT) holds a great promise in providing autonomous and ubiquitous connectivity between devices in future communication systems. Due to the spectrum scarcity, very high frequency (VHF) and ultra high frequency (UHF) bands are viewed as valuable resources for IoT communications, especially to connect to distant locations that are hard to reach using higher frequencies. Existing propagation models in the VHF/UHF frequency bands are mainly for broadcasting and cellular systems with high transmit antenna heights, and hence, they are not suitable for IoT communications characterized by low antenna heights at both the transmitter and receiver. In this paper, we present new statistical path loss and delay spread models for IoT communications based on quasi-simultaneous wideband channel measurements conducted in the VHF/UHF frequency bands (from 37.8 to 370 MHz) at the city of Halifax, Canada. In particular, we present two log-distance path loss models (frequency-independent path loss exponent and frequencydependent path loss exponent), as well as, a new statistical distribution of the delay spread.

Design and field trial measurement results for a portable and low‐cost very‐high‐frequency/ultra‐high‐frequency channel sounder platform for Internet of things propagation research

“…Results in [15] for 77.5 MHz propagation measurement in a hilly city identified a distance-dependent coefficient of 46.4 (aligning well with our city pedestrian model) and a standard deviation of 8.6 dB. Our suburban car results are influenced by significant path loss variations in the small data set.…”

“…However, shadowing and small-scale fading effects are quite usual in such field measurements and the standard deviation of the data (from the model straight lines) are not out of the ordinary, compared with other trials. The reduced distance-dependent term n of Table 2 may be due to the existence of several near LoS paths existing between the TX and some of the RX sites -even at the furthest range, which may not have existed in [15].…”

“…Previously reported VHF and UHF RMS delay spreads have been observed to be typically in ranges of 100 ns to 2 µs at distances of up to 2 km in various urban settings [12], [13], [14], [15] though occasionally reaching 5 µs when indoor-outdoor transitions are included [16]. In contrast, the delay spreads in mountainous regions at VHF have achieved 8 µs [13] to 30 µs [17].…”

“…Traditional path loss models focus on broadcast or cellular systems so are not relevant or representative of the use cases for IoT. New research is now developing propagation models for VHF systems that are close to ground for short range outdoor applications [19], [7], [15] and indoor-outdoor transitions [20], but the need for a compact and portable low cost CSR is clear, to provoke and enable further research.…”

Performance Analysis of Propagation in VHF Military Tactical Communication System

“…When working locally in a small town with regular grid roads aside from some roadblocks, there are two types of radio connections. The first is a line-ofsight (LoS) connection, and the second is a nonline-of-sight (NLoS) connection 12 . The NLoS connect occurs when Rx is shielded by homes or impediments and the transmit antenna of Tx is not visible at the Rx location.…”